Co-reporter:Jian Wang, Yu Liang, Qingqing Jin, Jing Hou, Bei Liu, Xin Li, Wanying Chen, Tasawar Hayat, Ahmed Alsaedi, and Xiangke Wang
ACS Sustainable Chemistry & Engineering June 5, 2017 Volume 5(Issue 6) pp:5550-5550
Publication Date(Web):May 15, 2017
DOI:10.1021/acssuschemeng.7b00957
The potential coexistence of toxic metals and graphene oxide (GO) in the natural environment threatens human health. Herein, rare earth doped titanium dioxide coated carbon sphere composites (C@La-TiO2 and C@Ce-TiO2) were synthesized for the simultaneous removal of GO and Cr(VI) from wastewater. The results showed that a relatively high concentration of NaCl was beneficial to the binding of GO, whereas it was adverse to Cr(VI) removal. The removal capacity of C@La-TiO2 reached 383.3 mg/g for GO and 50.5 mg/g for Cr(VI) at pH 5.0. The adsorption process of GO and Cr(VI) on the composites was spontaneous and endothermic. Interestingly, the removal capacity of Cr(VI) on the composites increased significantly in the presence of GO, which was ascribed to the simultaneous adsorption of GO and Cr(VI) on composites and surface adsorbed GO for Cr(VI). However, in the presence of Cr(VI), the GO removal on the composites decreased prominently due to the competitive adsorption between GO and Cr(VI) on the composite surfaces. The interaction of GO was mainly dominated by electrostatic attraction and hydrogen bonding, whereas the removal of Cr(VI) was mainly attributed to outer-sphere surface complexation and electrostatic attraction. The findings can provide new insights into the simultaneous elimination of GO and heavy metal ions in natural aquatic environmental pollution cleanup.Keywords: C@Ce-TiO2 composite; C@La-TiO2 composite; Cr(VI); Graphene oxide;
Co-reporter:Tao Wen, Jian Wang, Xing Li, Shuyi Huang, Zhongshan Chen, Suhua Wang, Tasawar Hayat, Ahmed Alsaedi, Xiangke Wang
Journal of Environmental Chemical Engineering 2017 Volume 5, Issue 4(Issue 4) pp:
Publication Date(Web):1 August 2017
DOI:10.1016/j.jece.2017.07.022
In this paper, we reported an environmental friendly and cost-effective method to prepare magnetic nanoparticles decorated tea waste (Fe3O4-tea) composites by chemical co-precipitation of Fe3+/Fe2+ on waste tea leaves. Various physical and chemical characterizations indicated that the synthetic Fe3O4 nanoparticles were combined to the tea powder surface by chemical bonds. When tested as an adsorbent for Cu(II) and Zn(II) removal, the Fe3O4-tea composites showed an unexpected high sorption capacity and satisfactory regeneration performance, better than those of naked Fe3O4 and other reported materials. The results showed that the maximum sorption capacities of Fe3O4-tea calculated from Langmuir isotherm model were 95.44 mg g−1 for Cu(II) and 68.78 mg g−1 for Zn(II) at pH 6.0. Interestingly, it was found that much higher adsorption capacity was achieved for Cu(II) on Fe3O4-tea rather than that for Zn(II) adsorption, which was attributed to the higher ionic potential of Cu(II), preferably penetrating into smaller pores. Furthermore, in the binary-solute system, Cu(II) exhibited greater inhibition for Zn(II) sorption, suggesting stronger affinity of Fe3O4-tea for Cu(II). Relatively, pseudo-second-order equation was the optimal model to describe the kinetics of Cu(II) and Zn(II) sorption, suggesting a chemisorption with the adsorption mechanism via M-O or M-N bonding. X-ray photoelectron spectroscopy (XPS) analysis showed that the enrichment of Cu(II) and Zn(II) was attributed to the abundant binding sites (e.g., –OH, –COOH and –NH groups) of Fe3O4-tea, which made stable complex compound with Cu2+ or Zn2+. This work provides a facile and general approach to synthesize promising magnetic biochar materials for wastewater treatment.Download high-res image (214KB)Download full-size image
Co-reporter:Yidong Zou, Xiangxue Wang, Fen Wu, Shujun Yu, Yezi Hu, Wencheng Song, Yunhai Liu, Hongqing Wang, Tasawar Hayat, and Xiangke Wang
ACS Sustainable Chemistry & Engineering 2017 Volume 5(Issue 1) pp:
Publication Date(Web):November 3, 2016
DOI:10.1021/acssuschemeng.6b02550
Novel rod-like ternary nanoscale layered double hydroxides (Ca-Mg-Al-LDH) and their bimetal derivatives (Ca-Mg-Al-LDOx, x: 200, 300, 400, 500, and 600 °C) were fabricated with a simple-green hydrothermal and calicination process. The interaction mechanism and adsorption property of U(VI) on Ca-Mg-Al-LDH and Ca-Mg-Al-LDOx were investigated by a batch technique and spectroscopy analysis, and the results indicated that U(VI) could form strong and stable surface complexes on Ca-Mg-Al-LDH and Ca-Mg-Al-LDOx surfaces. The adsorption capacity of U(VI) on various adsorbents could be controlled and adjusted through changing the calcination temperature, which was attributed to the different contents of various metal–oxide bonds (e.g., Ca–O, Mg–O, and Al–O). The adsorption capacities of U(VI) on these adsorbents were in the order of Ca-Mg-Al-LDO500 (486.8 mg/g) > Ca-Mg-Al-LDO600 (373.4 mg/g) > Ca-Mg-Al-LDO400 (292.5 mg/g) > Ca-Mg-Al-LDO300 (260.0 mg/g) > Ca-Mg-Al-LDO200 (223.5 mg/g) > Ca-Mg-Al-LDH (132.5 mg/g), which might be attributed to more active surface sites and abundant “Ca–O and Al–O” with the increase of calcination temperature. The results of kinetic and thermodynamic studies demonstrated that the adsorption was a spontaneous and endothermic chemical process, and the better fitted Sips model revealed that the adsorption reaction was multilayer adsorption at low concentration of U(VI) and monolayer adsorption at high concentration of U(VI). This study provided highlights on the interaction mechanism of U(VI) with various metal–oxide bonds, and it could play an important role for the controllable adsorption capacity and effcient application in environmental remediation.Keywords: Controllable synthesis; Layered double hydroxides; Nanomaterials; U(VI);
Co-reporter:Jie Li, Qiaohui Fan, Yijin Wu, Xiangxue Wang, Changlun Chen, Zhiyong Tang and Xiangke Wang
Journal of Materials Chemistry A 2016 vol. 4(Issue 5) pp:1737-1746
Publication Date(Web):23 Dec 2015
DOI:10.1039/C5TA09132B
Potentially toxic metals and dyes commonly coexist in industrial wastewaters, posing a serious threat to public health and the environment and making the treatment more challenging. Herein, we report a novel magnetic polydopamine (PDA)–LDH (MPL) bifunctional material, which is fabricated by an easy and green approach for the simultaneous removal of potentially toxic metals and anionic dyes. In this assembly, both PDA and LDHs are expected to capture these pollutants. In a mono-component system, the removal behaviors showed heterogeneous removal capacities of 75.01, 624.89 and 584.56 mg g−1 for Cu(II), methyl orange (MO) and Congo red (CR), respectively. Interestingly, the presence of CR and MO enhanced the removal of Cu(II) significantly in the Cu(II)–dye binary system. However, the presence of Cu(II) had no significant effect on dyes. Based on the characterization results including X-ray diffraction (XRD) analysis, Fourier transformed infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and elemental mapping, the removal of Cu(II) was mainly controlled by bonding with surface functional groups (hydroxyl, catechol, imine and amine groups), coupled with isomorphic substitution and surface precipitation. In summary, such a green and facile synthesis method, efficient removal performance and superior reusability suggest that the MPL assemblies have practical application potential for integrative and efficient treatment of coexisting toxic pollutants.
Co-reporter:Shouwei Zhang, Qiaohui Fan, Huihui Gao, Yongshun Huang, Xia Liu, Jiaxing Li, Xijin Xu and Xiangke Wang
Journal of Materials Chemistry A 2016 vol. 4(Issue 4) pp:1414-1422
Publication Date(Web):07 Dec 2015
DOI:10.1039/C5TA08400H
While the synthesis of heterogeneous catalysts is well established, it is extremely challenging to fabricate complex hollow structures with mixed transition metal oxides. Herein, we report a facile in situ growth process of SiO2@Fe3O4@MnO2, followed by an etching method to synthesize a hierarchical hollow structure, namely Fe3O4@MnO2 ball-in-ball hollow spheres (Fe3O4@MnO2 BBHs). The as-prepared Fe3O4@MnO2 BBHs were applied to degrade methylene blue (MB) by catalytic generation of active radicals from peroxymonosulfate (PMS), exhibiting the merits of excellent catalytic performance, easy separation, good stability and recyclability. In this architecture, the degradation process can be divided into three layers. The outer hierarchical MnO2 nanosheets could accumulate and transport the pollutants by electrostatic interactions and catalyze the generation of active radicals for degradation. Both the inner MnO2 nanosheets and the outer Fe3O4 hollows could produce active radicals to accelerate the pollutant degradation. The active catalytic sites also existed in the inner Fe3O4 hollows, which could further degrade the highly concentrated pollutants in the hollows. This work provides new strategies for the controllable synthesis of complex hollow structures and their application in environmental remediation.
Co-reporter:Yidong Zou, Xiangxue Wang, Yuejie Ai, Yunhai Liu, Jiaxing Li, Yongfei Ji, and Xiangke Wang
Environmental Science & Technology 2016 Volume 50(Issue 7) pp:3658-3667
Publication Date(Web):March 15, 2016
DOI:10.1021/acs.est.6b00255
Graphene oxide (GO) has attracted considerable attention because of its remarkable enhanced adsorption and multifunctional properties. However, the toxic properties of GO nanosheets released into the environment could lead to the instability of biological system. In aqueous phase, GO may interact with fine mineral particles, such as chloridion intercalated nanocrystallined Mg/Al layered double hydroxides (LDH–Cl) and nanocrystallined Mg/Al LDHs (LDH–CO3), which are considered as coagulant molecules for the coagulation and removal of GO from aqueous solutions. Herein the coagulation of GO on LDHs were studied as a function of solution pH, ionic strength, contact time, temperature and coagulant concentration. The presence of LDH–Cl and LDH–CO3 improved the coagulation of GO in solution efficiently, which was mainly attributed to the surface oxygen-containing functional groups of LDH–Cl and LDH–CO3 occupying the binding sites of GO. The coagulation of GO by LDH–Cl and LDH–CO3 was strongly dependent on pH and ionic strength. Results of theoretical DFT calculations indicated that the coagulation of GO on LDHs was energetically favored by electrostatic interactions and hydrogen bonds, which was further evidenced by FTIR and XPS analysis. By integrating the experimental results, it was clear that LDH–Cl could be potentially used as a cost-effective coagulant for the elimination of GO from aqueous solutions, which could efficiently decrease the potential toxicity of GO in the natural environment.
Co-reporter:Xuemei Ren, Qunyan Wu, Huan Xu, Dadong Shao, Xiaoli Tan, Weiqun Shi, Changlun Chen, Jiaxing Li, Zhifang Chai, Tasawar Hayat, and Xiangke Wang
Environmental Science & Technology 2016 Volume 50(Issue 17) pp:9361-9369
Publication Date(Web):August 1, 2016
DOI:10.1021/acs.est.6b02934
This study establishes the relationship between the graphene oxide (GO) colloidal behavior and the co-adsorption of Cd(II) and phosphate (P(V)) on GO. Results reveal that the interactions among GO, Cd(II), and P(V) exhibit a significant dependence on solution chemistry and addition sequences and that these interactions subsequently affect the GO colloidal behavior. The GO aggregation is pH-dependent at pH < 4.0 and depends apparently on the binding ability of Cd(II) to GO at pH > 4.0. When the components were added simultaneously, the presence of P(V) enhances the GO binding capacity toward Cd(II), confirmed by theoretical calculation, resulting in the greater destabilizing influence of Cd(II) + P(V) on GO than Cd(II) at pH 3.0–9.5, while the formation of Cd3(PO4)2 precipitate leads to a lower destabilizing influence of Cd(II) + P(V) on GO than Cd(II) at pH > 9.5. Both pH and addition sequence affect the destabilizing ability of Cd(II) + P(V). These new insights are expected to provide valuable information not only for the application of GO as a potential adsorbent in multicomponent systems for heavy metal ion and oxyanion co-removal but also for the fate and risk assessment of GO after serving as heavy metal ion and oxyanion carrier.
Co-reporter:Yubing Sun, Zhen-Yu Wu, Xiangxue Wang, Congcong Ding, Wencai Cheng, Shu-Hong Yu, and Xiangke Wang
Environmental Science & Technology 2016 Volume 50(Issue 8) pp:4459
Publication Date(Web):March 21, 2016
DOI:10.1021/acs.est.6b00058
The adsorption mechanism of U(VI) and Eu(III) on carbonaceous nanofibers (CNFs) was investigated using batch, IR, XPS, XANES, and EXAFS techniques. The pH-dependent adsorption indicated that the adsorption of U(VI) on the CNFs was significantly higher than the adsorption of Eu(III) at pH < 7.0. The maximum adsorption capacity of the CNFs calculated from the Langmuir model at pH 4.5 and 298 K for U(VI) and Eu(III) were 125 and 91 mg/g, respectively. The CNFs displayed good recyclability and recoverability by regeneration experiments. Based on XPS and XANES analyses, the enrichment of U(VI) and Eu(III) was attributed to the abundant adsorption sites (e.g., −OH and −COOH groups) of the CNFs. IR analysis further demonstrated that −COOH groups were more responsible for U(VI) adsorption. In addition, the remarkable reducing agents of the R-CH2OH groups were responsible for the highly efficient adsorption of U(VI) on the CNFs. The adsorption mechanism of U(VI) on the CNFs at pH 4.5 was shifted from inner- to outer-sphere surface complexation with increasing initial concentration, whereas the surface (co)precipitate (i.e., schoepite) was observed at pH 7.0 by EXAFS spectra. The findings presented herein play an important role in the removal of radionuclides on inexpensive and available carbon-based nanoparticles in environmental cleanup applications.
Co-reporter:Yidong Zou, Xiangxue Wang, Ayub Khan, Pengyi Wang, Yunhai Liu, Ahmed Alsaedi, Tasawar Hayat, and Xiangke Wang
Environmental Science & Technology 2016 Volume 50(Issue 14) pp:7290
Publication Date(Web):June 22, 2016
DOI:10.1021/acs.est.6b01897
The presence of heavy metals in the industrial effluents has recently been a challenging issue for human health. Efficient removal of heavy metal ions from environment is one of the most important issues from biological and environmental point of view, and many studies have been devoted to investigate the environmental behavior of nanoscale zerovalent iron (NZVI) for the removal of toxic heavy metal ions, present both in the surface and underground wastewater. The aim of this review is to show the excellent removal capacity and environmental remediation of NZVI-based materials for various heavy metal ions. A new look on NZVI-based materials (e.g., modified or matrix-supported NZVI materials) and possible interaction mechanism (e.g., adsorption, reduction and oxidation) and the latest environmental application. The effects of various environmental conditions (e.g., pH, temperature, coexisting oxy-anions and cations) and potential problems for the removal of heavy metal ions on NZVI-based materials with the DFT theoretical calculations and EXAFS technology are discussed. Research shows that NZVI-based materials have satisfactory removal capacities for heavy metal ions and play an important role in the environmental pollution cleanup. Possible improvement of NZVI-based materials and potential areas for future applications in environment remediation are also proposed.
Co-reporter:Dadong Shao, Xiangxue Wang, Xiaolin Wang, Sheng Hu, Tasawar Hayat, Ahmed Alsaedi, Jiaxing Li, Suhua Wang, Jun Hu and Xiangke Wang
RSC Advances 2016 vol. 6(Issue 57) pp:52076-52081
Publication Date(Web):18 May 2016
DOI:10.1039/C6RA10817B
A magnetic nanocomposite of zero valent iron (ZVI)/poly(amidoxime) (PAO) was prepared by polymerization of acrylonitrile on the ZVI surface, followed by hydroxylamine (NH2OH) treatment to convert the cyano group (–CN) into an amidoxime group (AO). The characterization results showed that PAO-stabilized ZVI magnetic composite (denoted as ZVI/PAO) was prepared successfully. ZVI/PAO was used as an adsorbent for the separation of U(VI) from solutions. The effect of environmental conditions on U(VI) adsorption onto ZVI/PAO was studied in detail. U(VI) adsorption on the ZVI/PAO surface reached equilibrium within 3 h, and the adsorption process is well described by the pseudo-second-order kinetics model. Adsorption isotherms of U(VI) on the ZVI/PAO surface can be well fitted by the Langmuir model, and the maximum adsorption capacity was calculated to be 206 mg g−1 at T = 298 K and pH = 5.0. Experimental results highlighted the application of ZVI/PAO as an adsorbent for the efficient separation of U(VI) and reduction of U(VI) to U(IV) from aqueous solutions.
Co-reporter:Shouwei Zhang, Jiaxing Li, Xiangke Wang, Yongshun Huang, Meiyi Zeng and Jinzhang Xu
Journal of Materials Chemistry A 2015 vol. 3(Issue 18) pp:10119-10126
Publication Date(Web):23 Mar 2015
DOI:10.1039/C5TA00635J
1D Ag@AgVO3 nanowire/graphene/protonated g-C3N4 nanosheet (Ag@AgVO3/rGO/PCN) heterojunctions are fabricated via a simple electrostatic self-assembly process followed by a photochemical reduction method. In this hybrid structure, 1D Ag@AgVO3 nanowires penetrate through 2D nanosheets (graphene and PCN), forming a 3D hybrid photocatalyst, which is applied as an efficient visible light driven photocatalyst for organic pollutant degradation. Its enhanced photocatalytic activity is ascribed to the well-known electronic conductivity of 2D graphene, the intense visible light absorption of 1D Ag@AgVO3 nanowires, large surface areas and rapid photogenerated charge interface transfer and separation. Our results provide a facile way to fabricate hierarchical g-C3N4-based photocatalysts in a controlled manner and highlight promising prospects by adopting an integrative 1D and 2D nanomaterial strategy to design more efficient semiconductor-based composite photocatalysts with high photocatalytic activities and a wide spectral response toward environmental and energy applications.
Co-reporter:He Chen, Xiangxue Wang, Jiaxing Li and Xiangke Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 11) pp:6073-6081
Publication Date(Web):30 Jan 2015
DOI:10.1039/C5TA00299K
Well-structured cotton derived porous carbon (CDPC) and cotton derived porous carbon oxide (CDPCO) were fabricated via a facile and economic alkaline etching method and were used as adsorbents for waste water cleanup. As a carbon source, natural cotton waste was dehydrated with sodium hydroxide at low temperatures and further etched at high temperatures in a thermal treatment process. The synthesized CDPCO exhibited an excellent adsorption performance of organic pollutants and heavy metal ions such as methylene blue, 1-naphthylamine, Cd(II) and Co(II) in aqueous solutions. The adsorption mechanism was investigated via FT-IR analysis and controlled experiments, and it was concluded that the organic pollutant removal was affected by the molecular size of the organic pollutants and the ionic interactions between the pollutants and adsorbents. The adsorption of heavy metal ions was dependent on the interactions between the heavy metal ions and functional groups on the adsorbents’ surfaces. The adsorption process fitted the Langmuir model better than the Freundlich model. Our results suggested that CDPC could be a favorable adsorbent for the removal of organic pollutants and heavy metal ions from aqueous solutions.
Co-reporter:Yingguo Zhao, Xiangxue Wang, Jiaxing Li and Xiangke Wang
Polymer Chemistry 2015 vol. 6(Issue 30) pp:5376-5384
Publication Date(Web):18 May 2015
DOI:10.1039/C5PY00540J
Amidoxime-functionalized mesoporous silica has been prepared by the self-assembly co-condensation of tetraethoxysilane (TEOS) and 2-cyanoethyltriethoxysilane (CTES). By varying the molar ratio of CTES, a series of sorbents with different densities of organic groups have been obtained and applied to eliminate U(VI) ions from aqueous solutions. Sorption isotherms and kinetics have been investigated to discuss the influence of organic group densities on the sorption performance. Organic functionalization has a dual influence on both sorption capacities and sorption rates. The sorption capacity increases with the initial increase of organic group density until it reaches the maximum and then decreases with further increase of organic functionalization. The optimal dosage corresponds to the balance between the structural porosities of the sorbent and the loading contents of organic functional groups. Sorption mechanisms have been examined using the X-ray photoelectron spectra and Fourier transformed infrared spectra of sorbents before and after uranium sorption, and the results indicate that the sorption is mainly attributed to the formation of surface complexes between U(VI) and the amidoxime groups.
Co-reporter:Juan Wei, Zheng Guo, Xing Chen, Dong-Dong Han, Xiang-Ke Wang, and Xing-Jiu Huang
Analytical Chemistry 2015 Volume 87(Issue 3) pp:1991
Publication Date(Web):January 12, 2015
DOI:10.1021/ac504449v
Detection of Cr(VI) by electrochemical methods generally focuses on noble-metal-modified electrodes in strong acid solution using voltammetric techniques. In this work, we report a new strategy to detect Cr(VI) as HCrO4– at pH 5.0 in drinking water using electrochemical impedance spectroscopy. The strategy is based on the high-affinity and specific binding of crown ethers (i.e., azacrown) to HCrO4–, which forms sandwich complexes between them via hydrogen bonds and moiety interactions with K+ captured by azacrown on its self-assembled Au electrode surface. This then blocks the access of redox probes (Fe(CN)63–/4–) to the self-assembled Au electrode, further resulting in an increase in the electron transfer resistance. This method offers a detection limit of 0.0014 ppb Cr(VI) with a sensitivity of 4575.28 kΩ [log c (ppb)]−1 over the linear range of 1–100 ppb (R2 = 0.994) at pH 5.0. In addition, the azacrown self-assembled Au electrode has good selectivity for Cr(VI) with good stability and low interferences. This approach can be performed on spiked Cr(VI) as well as real samples. To the best of our knowledge, this is the first example of electrochemical impedimetric sensing that allows ultrasensitive and ultraselective detection of Cr(VI).
Co-reporter:Zhongxiu Jin, Xiangxue Wang, Yubing Sun, Yuejie Ai, and Xiangke Wang
Environmental Science & Technology 2015 Volume 49(Issue 15) pp:9168-9175
Publication Date(Web):July 10, 2015
DOI:10.1021/acs.est.5b02022
Adsorption of 4-n-nonylphenol (4-n-NP) and bisphenol A (BPA) on magnetic reduced graphene oxides (rGOs) as a function of contact time, pH, ionic strength and humic acid were investigated by batch techniques. Adsorption of 4-n-NP and BPA were independent of pH at 3.0- 8.0, whereas the slightly decreased adsorption was observed at pH 8.0–11.0. Adsorption kinetics and isotherms of 4-n-NP and BPA on magnetic rGOs can be satisfactorily fitted by pseudo-second-order kinetic and Freundlich model, respectively. The maximum adsorption capacities of magnetic rGOs at pH 6.5 and 293 K were 63.96 and 48.74 mg/g for 4-n-NP and BPA, respectively, which were significantly higher than that of activated carbon. Based on theoretical calculations, the higher adsorption energy of rGOs + 4-n-NP was mainly due to π–π stacking and flexible long alkyl chain of 4-n-NP, whereas adsorption of BPA on rGOs was energetically favored by a lying-down configuration due to π–π stacking and dispersion forces, which was further demonstrated by FTIR analysis. These findings indicate that magnetic rGOs is a promising adsorbent for the efficient elimination of 4-n-NP/BPA from aqueous solutions due to its excellent adsorption performance and simple magnetic separation, which are of great significance for the remediation of endocrine-disrupting chemicals in environmental cleanup.
Co-reporter:Xiangxue Wang, Shubin Yang, Weiqun Shi, Jiaxing Li, Tasawar Hayat, and Xiangke Wang
Environmental Science & Technology 2015 Volume 49(Issue 19) pp:11721-11728
Publication Date(Web):September 15, 2015
DOI:10.1021/acs.est.5b02679
Herein the sorption of Eu(III) and 243Am(III) on multiwalled carbon nanotubes (CNTs) are studied, and the results show that Eu(III) and 243Am(III) could form strong inner-sphere surface complexes on CNT surfaces. However, the sorption of Eu(III) on CNTs is stronger than that of 243Am(III) on CNTs, suggesting the difference in the interaction mechanisms or properties of Eu(III) and 243Am(III) with CNTs, which is quite different from the results of Eu(III) and 243Am(III) interaction on natural clay minerals and oxides. On the basis of the results of density functional theory calculations, the binding energies of Eu(III) on CNTs are much higher than those of 243Am(III) on CNTs, indicating that Eu(III) could form stronger complexes with the oxygen-containing functional groups of CNTs than 243Am(III), which is in good agreement with the experimental results of higher sorption capacity of CNTs for Eu(III). The oxygen-containing functional groups contribute significantly to the uptake of Eu(III) and 243Am(III), and the binding affinity increases in the order of ≡S—OH < ≡S—COOH < ≡S—COO–. This paper highlights the interaction mechanism of Eu(III) and 243Am(III) with different oxygen-containing functional groups of CNTs, which plays an important role for the potential application of CNTs in the preconcentration, removal, and separation of trivalent lanthanides and actinides in environmental pollution cleanup.
Co-reporter:Yubing Sun, Shubin Yang, Yue Chen, Congcong Ding, Wencai Cheng, and Xiangke Wang
Environmental Science & Technology 2015 Volume 49(Issue 7) pp:4255
Publication Date(Web):March 11, 2015
DOI:10.1021/es505590j
The adsorption and desorption of U(VI) on graphene oxides (GOs), carboxylated GOs (HOOC-GOs), and reduced GOs (rGOs) were investigated by batch experiments, EXAFS technique, and computational theoretical calculations. Isothermal adsorptions showed that the adsorption capacities of U(VI) were GOs > HOOC-GOs > rGOs, whereas the desorbed amounts of U(VI) were rGOs > GOs > HOOC-GOs by desorption kinetics. According to EXAFS analysis, inner-sphere surface complexation dominated the adsorption of U(VI) on GOs and HOOC-GOs at pH 4.0, whereas outer-sphere surface complexation of U(VI) on rGO was observed at pH 4.0, which was consistent with surface complexation modeling. Based on the theoretical calculations, the binding energy of [G···UO2]2+ (8.1 kcal/mol) was significantly lower than those of [HOOC-GOs···UO2]2+ (12.1 kcal/mol) and [GOs-O···UO2]2+ (10.2 kcal/mol), suggesting the physisorption of UO22+ on rGOs. Such high binding energy of [GOs-COO···UO2]+ (50.5 kcal/mol) revealed that the desorption of U(VI) from the −COOH groups was much more difficult. This paper highlights the effect of the hydroxyl, epoxy, and carboxyl groups on the adsorption and desorption of U(VI), which plays an important role in designing GOs for the preconcentration and removal of radionuclides in environmental pollution cleanup applications.
Co-reporter:Wencheng Song, Xiangxue Wang, Qi Wang, Dadong Shao and Xiangke Wang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 1) pp:398-406
Publication Date(Web):03 Nov 2014
DOI:10.1039/C4CP04289A
Polyacrylamide (PAM) grafted graphene oxide (denoted as PAM/GO) was synthesized by the plasma-induced polymerization technique and applied as an adsorbent for the simultaneous removal of radionuclides from radioactive wastewater. The interactions of PAM/GO with the radionuclides U(VI), Eu(III) and Co(II) were studied, along with their sorption kinetics. The results indicated that radionuclide sorption on PAM/GO was affected by the solution pH and ionic strength. The maximum sorption capacities of U(VI), Eu(III) and Co(II) on PAM/GO (0.698, 1.245 and 1.621 mmol g−1, respectively) at pH = 5.0 ± 0.1 and T = 295 K were much higher than those of radionuclides on GO and other adsorbents. The thermodynamic data (ΔH0, ΔS0 and ΔG0) calculated from the temperature-dependent sorption isotherms suggested that the sorption of radionuclides on PAM/GO was a spontaneous and endothermic process. These results indicate that PAM/GO is a promising material for the control of radionuclide pollution.
Co-reporter:Xiubing Huang, Guixia Zhao and Xiangke Wang
RSC Advances 2015 vol. 5(Issue 62) pp:49973-49978
Publication Date(Web):01 Jun 2015
DOI:10.1039/C5RA08670A
A facile thermal reduction method has been proposed for the fabrication of reduced graphene oxide/metal (e.g., Cu, Co, Ni) nanoparticle hybrid composites at 500 °C for 90 minutes under flowing argon due to the release of reductive gas by thermolysis of graphene oxide. The loading amount and dispersion of metal nanoparticles could be easily controlled via the mass ratio of graphene oxide/metal nitrate precursor and the calcination temperature. The results show that with the increase of graphene oxide/metal nitrate mass ratio, it is easier to obtain pure metallic nanoparticles with high dispersion and small nanoparticle size.
Co-reporter:Juan Wei, Jianbo He, Changlun Chen and Xiangke Wang
Analytical Methods 2015 vol. 7(Issue 13) pp:5641-5648
Publication Date(Web):01 Jun 2015
DOI:10.1039/C5AY00928F
Catechin is a polyphenol antioxidant which can be found in great abundance in the leaves of tea plants. In this study, catechin was electrodeposited on an activated carbon paste electrode for electrocatalytic determination of two neurotransmitters, dopamine (DA) and serotonin (ST). The voltammetric conditions for electrode preparation in catechin solution were optimized as follows: phosphate buffer at pH 7.4, catechin concentration of 1.0 mM, potential window of 0.2–1.6 V (vs. Ag/AgCl/KClsat), scan rate of 50 mV s−1 and cycle number of 15. The prepared electrode showed high electrocatalytic activity for the oxidation of both DA and ST. The highest electrocatalytic activity for DA oxidation was observed in the physiological pH (7.4) buffer solution. Amperometric detection under stirring achieved a current sensitivity of 10.29 nA nM−1 cm−2 to DA in the linear concentration range of 10–780 nM, and 4.81 nA nM−1 cm−2 to ST in the range of 30–2340 nM, with the lowest detection limits of 0.5 and 3 nM for DA and ST, respectively. The resulting biosensor was successfully used to quantify DA and ST in commercial samples with high sensitivity and good stability. In addition, the fact that the oxidized catechin can effectively promote the electron transfer processes of DA and ST may help in understanding the role of catechin in nervous excitement.
Co-reporter:Dr. Shubin Yang;Dr. Changlun Chen;Dr. Yue Chen;Jiaxing Li;Dr. Dongqi Wang;Dr. Xiangke Wang;Dr. Wenping Hu
ChemPlusChem 2015 Volume 80( Issue 3) pp:480-484
Publication Date(Web):
DOI:10.1002/cplu.201402284
Abstract
The individual and competitive adsorption of PbII, NiII, and SrII on graphene oxides (GOs) was investigated by experimental and density functional theory (DFT) studies. Experimental results indicate that 1) in all the single, binary, and ternary metal-ion adsorption systems, the sequence of maximum adsorption capacities is PbII>NiII>SrII on GOs; 2) the desorption hysteresis of metal ions from GOs shows the adsorption affinity in the same sequence: PbII>NiII>SrII. For the first time, DFT calculations indicate that 1) PbII and NiII prefer to interact with the COH group, whereas SrII interacts with COH and COC comparably, and 2) PbII can easily abstract the OH group from the GOs to form the much more stable Pb(OH)–GO complex. These findings are very important and useful for understanding the mechanisms of heavy-metal-ion adsorption on GOs and assessing the adsorption of coexisting heavy-metal ions on GOs.
Co-reporter:Dr. Tao Wen;Dr. Xi-Lin Wu;Dr. Shouwei Zhang; Xiangke Wang; An-Wu Xu
Chemistry – An Asian Journal 2015 Volume 10( Issue 3) pp:595-601
Publication Date(Web):
DOI:10.1002/asia.201403295
Abstract
Herein we present a simple method for fabricating core–shell mesostructured CuO@C nanocomposites by utilizing humic acid (HA) as a biomass carbon source. The electrochemical performances of CuO@C nanocomposites were evaluated as an electrode material for supercapacitors and lithium-ion batteries. CuO@C exhibits an excellent capacitance of 207.2 F g−1 at a current density of 1 A g−1 within a potential window of 0–0.46 V in 6 M KOH solution. Significantly, CuO electrode materials achieve remarkable capacitance retentions of approximately 205.8 F g−1 after 1000 cycles of charge/discharge testing. The CuO@C was further applied as an anode material for lithium-ion batteries, and a high initial capacity of 1143.7 mA h g−1 was achieved at a current density of 0.1 C. This work provides a facile and general approach to synthesize carbon-based materials for application in large-scale energy-storage systems.
Co-reporter:Shouwei Zhang, Meiyi Zeng, Jiaxing Li, Jie Li, Jinzhang Xu and Xiangke Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 12) pp:4391-4397
Publication Date(Web):06 Jan 2014
DOI:10.1039/C3TA14604A
A facile and scalable in situ synthetic strategy (simultaneous template–graphitization) was developed to fabricate carbon-stabilized Fe/Fe3C nanoparticles, which were homogeneously embedded in porous carbon sheets (PMCS) as an excellent adsorbent for wastewater treatment. In the synthesis, the graphitic catalyst precursor (Fe(NO3)3) and template agent (Al(NO3)3) were introduced simultaneously into the agar hydrogel through the coordination of the metal precursor with the functional groups of agar, thus resulting in simultaneous realization of the template and graphitization of the carbon source under heat treatment. The PMCS with high surface area (1023.2 m2 g−1) exhibited high adsorption capacities and fast adsorption rates toward dyes. Using methylene blue (MB), methyl orange (MO) and crystal violet (CV) as model pollutants, the maximum adsorption capabilities for MB, MO, and CV reached 1615.9, 1062.4 and 1728.3 mg g−1, respectively. Moreover, the possibility of magnetic separation also facilitated its application in wastewater treatment on a large scale. This multifunctional material can potentially be used as a super adsorbent to efficiently remove pollutants from wastewater.
Co-reporter:Guixia Zhao, Tao Wen, Juan Zhang, Jiaxing Li, Huanli Dong, Xiangke Wang, Yuguo Guo and Wenping Hu
Journal of Materials Chemistry A 2014 vol. 2(Issue 4) pp:944-948
Publication Date(Web):24 Oct 2013
DOI:10.1039/C3TA13535G
In this manuscript, we have proposed a new facile method for the synthesis of pure Cr2O3 nanosheets without foreign templates for the first time. We used Na2CrO4 and graphene oxide as the oxidant and reductant templates, respectively, in a hydrothermal reaction in order to synthesize porous Cr(OH)3 nanosheet precursors. By controlling the proportion of graphene oxide and Cr(VI), the carbon framework could be partially retained, resulting in graphene-divided porous Cr(OH)3 nanosheets. After calcination at 700 °C, these graphene oxide-derived Cr(OH)3 nanosheets were transformed into pure Cr2O3 nanosheets or interconnected graphene–Cr2O3 nanomaterials. The graphene–Cr2O3 nanosheets exhibited an excellent rate capability and cycling performance as an anode material in lithium ion batteries (LIB), as well as a high reversible capacity of 850 mA h g−1 at a current density of 200 mA g−1, which is the highest capacity reported for Cr2O3 anode materials.
Co-reporter:Shouwei Zhang, Jiaxing Li, Xiangke Wang, Yongshun Huang, Meiyi Zeng, and Jinzhang Xu
ACS Applied Materials & Interfaces 2014 Volume 6(Issue 24) pp:22116
Publication Date(Web):November 26, 2014
DOI:10.1021/am505528c
A novel efficient Ag@AgCl/g-C3N4 plasmonic photocatalyst was synthesized by a rational in situ ion exchange approach between exfoliated g-C3N4 nanosheets with porous 2D morphology and AgNO3. The as-prepared Ag@AgCl-9/g-C3N4 plasmonic photocatalyst exhibited excellent photocatalytic performance under visible light irradiation for rhodamine B degradation with a rate constant of 0.1954 min–1, which is ∼41.6 and ∼16.8 times higher than those of the g-C3N4 (∼0.0047 min–1) and Ag/AgCl (∼0.0116 min–1), respectively. The degradation of methylene blue, methyl orange, and colorless phenol further confirmed the broad spectrum photocatalytic degradation abilities of Ag@AgCl-9/g-C3N4. These results suggested that an integration of the synergetic effect of suitable size plasmonic Ag@AgCl and strong coupling effect between the Ag@AgCl nanoparticles and the exfoliated porous g-C3N4 nanosheets was superior for visible-light-responsive and fast separation of photogenerated electron–hole pairs, thus significantly improving the photocatalytic efficiency. This work may provide a novel concept for the rational design of stable and high performance g-C3N4-based plasmonic photocatalysts for unique photochemical reaction.Keywords: Ag@AgCl/g-C3N4; heterostructures; ion exchange; photocatalysis; plasmonic photocatalyst; visible light
Co-reporter:Rui Hu, Dadong Shao and Xiangke Wang
Polymer Chemistry 2014 vol. 5(Issue 21) pp:6207-6215
Publication Date(Web):07 Jul 2014
DOI:10.1039/C4PY00743C
Graphene oxide/polypyrrole (GO/PPy) composites were synthesized via a dielectric barrier discharge (DBD) plasma technique in nitrogen conditions, and characterized by scanning electron microscopy (SEM), Raman spectroscopy, thermal gravimetric analysis (TGA), Fourier transformed infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). The sorption of U(VI) ions on GO/PPy composites from aqueous solutions was investigated as a function of contact time, pH, ionic strength and U(VI) initial concentrations. The sorption capacity of U(VI) on GO/PPy composites was much higher than those of U(VI) on GO, PPy and many other materials of today. The sorption of U(VI) on GO/PPy composites obeyed the Langmuir model, and was mainly attributed to surface complexation via the coordination of U(VI) ions with oxygen- and nitrogen-containing functional groups. The selectivity sorption of U(VI) ions on GO/PPy composites in the presence of other metal ions (i.e., Co(II), Ni(II), Cd(II), Sr(II), Zn(II)) indicated an overall preference for U(VI) ions. Moreover, the GO/PPy composites could be regenerated through the desorption of adsorbed U(VI) ions by using 1.0 M HCl solution, and cycling reused without an obvious decrease of sorption capacity. All these performances indicate that GO/PPy composites are suitable materials for the highly selective removal and preconcentration of U(VI) ions from aqueous solutions in environmental pollution management.
Co-reporter:Xiaoli Tan, Ming Fang, Xuemei Ren, Huiyang Mei, Dadong Shao, and Xiangke Wang
Environmental Science & Technology 2014 Volume 48(Issue 22) pp:13138-13145
Publication Date(Web):October 23, 2014
DOI:10.1021/es503570y
The formation of mixed metal precipitates has been identified as a significant mechanism for the immobilization and elimination of heavy metal ions. Silicate is present in natural systems ubiquitously, which may interfere with metal uptake on the mineral surface and thereby influences the solubility of the precipitate. Herein, kinetic sorption and dissolution experiments combined with extended X-ray absorption fine structure spectroscopy (EXAFS) were performed to elucidate the effect of silicate on the formation of Ni precipitates at the γ-Al2O3 surfaces. The uptake of Ni on γ-Al2O3 decreased with increasing amounts of silicate coated onto the γ-Al2O3 surface. Results of EXAFS analyses suggested the formation of Ni–Al layered double hydroxide (LDH) phases. The surface coating of silicate on γ-Al2O3 reduced Al release and finally resulted in a high Ni:Al ratio due to a lower extent of Al substitution into the precipitates. The presence of silicate prevented the growth of the precipitates and led to the formation of less stable Ni–Al LDH. The influence of silicate on the precipitate formation provided the evidence for the growth relationship between the precipitate and mineral substrate in the real environment. Increased rates of proton-promoted dissolution of Ni surface precipitates were mainly attributed to higher Ni:Al ratios in Ni–Al LDH precipitates formed in the presence of silicate.
Co-reporter:Xuemei Ren, Jiaxing Li, Xiaoli Tan, Weiqun Shi, Changlun Chen, Dadong Shao, Tao Wen, Longfei Wang, Guixia Zhao, Guoping Sheng, and Xiangke Wang
Environmental Science & Technology 2014 Volume 48(Issue 10) pp:5493-5500
Publication Date(Web):April 22, 2014
DOI:10.1021/es404996b
To assess the environmental behavior and impact of graphene oxide (GO) on living organisms more accurately, the aggregation of GO and its deposition on Al2O3 particles were systematically investigated using batch experiments across a wide range of solution chemistries. The results indicated that the aggregation of GO and its deposition on Al2O3 depended on the solution pH and the types and concentrations of electrolytes. MgCl2 and CaCl2 destabilized GO because of their effective charge screening and neutralization, and the presence of NaH2PO4 and poly(acrylic acid) (PAA) improved the stability of GO with the increase in pH values as a result of electrostatic interactions and steric repulsion. Specifically, the dissolution of Al2O3 contributed to GO aggregation at relatively low pH or high pH values. Results from this study provide critical information for predicting the fate of GO in aquatic-terrestrial transition zones, where aluminum (hydro)oxides are present.
Co-reporter:Qi Wang, Xiao Zuo and Xiangke Wang
Dalton Transactions 2014 vol. 43(Issue 34) pp:12961-12966
Publication Date(Web):19 Jun 2014
DOI:10.1039/C4DT01114G
A facile in situ plasma synthesis of graphene-based Pt nanoparticles is presented. For comparison, chemical reduction was also used. Ar plasma was capable of reducing Pt precursors into well dispersed Pt nanoparticles on graphene. The electrocatalytic activities of the two as-prepared catalysts were tested, and then they were used as anodes for methanol electro-oxidation in a DMFC. The catalyst prepared by the plasma approach showed higher catalytic activity for methanol electro-oxidation. The plasma technique is also suitable for the fabrication of other functional carbon based metal composites for their applications in multidisciplinary areas.
Co-reporter:Shouwei Zhang, Xiangxue Wang, Jiaxing Li, Tao Wen, Jinzhang Xu and Xiangke Wang
RSC Advances 2014 vol. 4(Issue 108) pp:63110-63117
Publication Date(Web):04 Nov 2014
DOI:10.1039/C4RA10189H
N-doped magnetic porous carbon (N-MPC) was prepared by a simple, one-step simultaneous activation-graphitization and activation route. The as-prepared N-MPC had an interconnected hierarchical structure and magnetic properties, with an ultrahigh surface area of ∼2148.42 m2 g−1 and a high pore volume of ∼1.26 cm3 g−1. The N-MPC composites had excellent dye removal capacities (1284.09 mg g−1 for methylene blue, 819.39 mg g−1 for rhodamin B, 376.29 mg g−1 for victoria blue and 565.41 mg g−1 for methyl orange) and also had a high reducing ability for Cr(VI). These properties were attributed to the low isoelectric point, high surface area, the aggregation of dyes on N-MPC surface and the metallic Ni(0) embedded in the unique structure. Moreover, the magnetic separation also facilitated its application in wastewater treatment on a large scale. Our results showed that the N-MPC composites have a superb removal capability of Cr(VI) and dyes from water, with important potential practical applications for wastewater clean-up. In addition, the ultrahigh surface area and large pore volume of N-MPC has great potential in many future applications, such as lithium ion batteries, supercapacitors and in photocatalysis.
Co-reporter:Shouwei Zhang;Jiaxing Li;Meiyi Zeng;Jie Li; Jinzhang Xu; Xiangke Wang
Chemistry - A European Journal 2014 Volume 20( Issue 31) pp:9805-9812
Publication Date(Web):
DOI:10.1002/chem.201400060
Abstract
Bandgap narrowing and a more positive valence band (VB) potential are generally considered to be effective methods for improving visible-light-driven photocatalysts because of the significant enhancement of visible-light absorption and oxidation ability. Herein, an approach is reported for the synthesis of a novel visible-light-driven high performance polymer photocatalyst based on band structure control and nonmetal and metal ion codoping, that is, C and Fe-codoped as a model, by a simple thermal conversion method. The results indicate that compared to pristine graphitic carbon nitride (g-C3N4), C+Fe-codoped g-C3N4 shows a narrower bandgap and remarkable positively shifted VB; as a result the light-absorption range was expanded and the oxidation capability was increased. Experimental results show that the catalytic efficiency of C+Fe-codoped g-C3N4 for photodegradation of rhodamine B (RhB) increased 14 times, compared with pristine g-C3N4 under visible-light absorption at λ>420 nm. The synergistic enhancement in C+Fe-codoped g-C3N4 photocatalyst could be attributed to the following features: 1) C+Fe-codoping of g-C3N4 tuned the bandgap and improved visible-light absorption; 2) the porous lamellar structure and decreased particle size could provide a high surface area and greatly improve photogenerated charge separation and electron transfer; and 3) both increased electrical conductivity and a more positive VB ensured the superior electron-transport property and high oxidation capability. The results imply that a high-performance photocatalyst can be obtained by combining bandgap control and doping modification; this may provide a basic concept for the rational design of high performance polymer photocatalysts with reasonable electronic structures for unique photochemical reaction.
Co-reporter:Xiaoli Tan, Xuemei Ren, Changlun Chen, Xiangke Wang
TrAC Trends in Analytical Chemistry 2014 Volume 61() pp:107-132
Publication Date(Web):October 2014
DOI:10.1016/j.trac.2014.06.010
•Analysis of the mechanism of interaction of lanthanides at solid surfaces.•We describe analytical approaches to speciation of lanthanides.•We summarize advantages and disadvantages of different analytical approaches.•We look forward to new analytical approaches to speciation of lanthanides.We review the analysis of lanthanide speciation at solid-water interfaces. We summarize the various mechanisms of lanthanide interaction with sorbent surfaces, such as surface complexation, precipitation and surface-induced redox reactions. There are a wide variety of available analytical techniques for understanding the speciation of lanthanides on surfaces and the reaction mechanisms of sorption. We also review recent advances in the utilization of quantum chemistry that widen the scope of lanthanide speciation studies. We review, summarize and discuss in detail the speciation of lanthanides, mainly Eu(III), at natural or synthetic mineral surfaces, and the available analytical techniques. We aim to collate valuable information about recent results for surface speciation analysis of lanthanides at solid-water interfaces.
Co-reporter:WenCheng Song;DaDong Shao;SongSheng Lu
Science China Chemistry 2014 Volume 57( Issue 9) pp:1291-1299
Publication Date(Web):2014 September
DOI:10.1007/s11426-014-5119-6
Cyclodextrin-modified graphene oxide nanosheets (denoted as CD/GO) were synthesized by an in-situ polymerization method and characterized by as well as Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and potentiometric acid-base titration. The characterization results indicated that CD was successfully grafted onto GO surfaces by forming a chemical bond. Mutual effects on the simultaneous removal of hexavalent uranium and humic acid by CD/GO from aqueous solution were investigated. The results indicated that U(VI) and humic acid (HA) sorption on CD/GO were greatly affected by pH and ionic strength. The presence of HA enhanced U(VI) sorption at low pH and reduced U(VI) sorption at high pH, whereas the presence of U(VI) enhanced HA sorption. The surface adsorbed HA acted as a “bridge” between U(VI) and CD/GO, and formed strong inner-sphere surface complexes with U(VI). Sorption isotherms of U(VI) or HA on CD/GO could be well fitted by the Langmuir model. This work highlights that CD/GO can be used as a promising material in the enrichment of U(VI) and HA from wastewater in U(VI) and humic substances obtained by environmental pollution cleanup.
Co-reporter:Kun Xie;Xiang-xue Wang;Zheng-jie Liu
Journal of Zhejiang University-SCIENCE A 2014 Volume 15( Issue 8) pp:671-680
Publication Date(Web):2014 August
DOI:10.1631/jzus.A1400133
The removal of arsenic from aqueous solution is crucial to human health and environmental pollution. Herein, flower-like α-Fe2O3 nanostructures were synthesized via a template-free microwave-assisted solvothermal technique, and were applied as adsorbents for the removal of arsenic (As(V)) from aqueous solutions. The results indicated that the synthesized flower-like α-Fe2O3 showed excellent sorption properties and had a maximum sorption capacity of 47.64 mg/g for As(V). Meanwhile, the experimental results of photodegradation of methylene blue (MB) indicated that the as-synthesized flower-like α-Fe2O3 exhibited very high photocatalytic performance for the photodegradation of MB and that the as-obtained flower-like α-Fe2O3 nanostructures were suitable materials in wastewater treatment.研究花状氧化铁的制备并探讨其对砷的吸附性能和亚甲基蓝的催化性能。1. 合成了花状氧化铁; 2. 发现Langmuir 模型能更好地模拟砷的吸附过程; 3. 发现花状氧化铁对亚甲基蓝有很好的催化降解性能。1. 使用扫描电镜、 投射电镜、 X 射线衍射和BET 比表面及孔径分析仪对合成的花状氧化铁进行表征; 2. 采用静态实验法研究砷的吸附性能及亚甲基蓝的催化行为。1. 采用一种低成本的溶剂热法合成了花状氧化铁; 2. 合成的花状氧化铁有着较大的比表面积并对砷有着很好的吸附性能, 并且吸附率随着pH 的增加而降低。 同时发现Langmuir 模型能更好地模拟砷的吸附过程; 3. 亚甲基蓝的初始浓度和花状氧化铁的用量对催化性能影响较为明显, 花状氧化铁有较好的重复利用性; 4. 合成的花状氧化铁可以应用于大批废水的处理。
Co-reporter:DaDong Shao;JiaXing Li
Science China Chemistry 2014 Volume 57( Issue 11) pp:1449-1458
Publication Date(Web):2014 November
DOI:10.1007/s11426-014-5195-7
The development of efficient materials for high extraction of uranium (UO22+) from seawater is critical for nuclear energy. Poly(amidoxime)-reduced graphene oxide (PAO/rGO) composites with excellent adsorption capability for UO22+ were synthesized by in situ polymerization of acrylonitrile monomers on GO surfaces, followed by amidoximation treatment with hydroxylamine. The adsorption capacities of PAO/rGO composites for UO22+ reached as high as 872 mg/g at pH 4.0. The excellent tolerance of these composites for high salinity and their regeneration-reuse properties can be applied in the nuclear-fuel industry by high extraction of trace UO22+ ions from seawater.
Co-reporter:Jie Li, Changlun Chen, Shouwei Zhang and Xiangke Wang
Environmental Science: Nano 2014 vol. 1(Issue 5) pp:488-495
Publication Date(Web):10 Jul 2014
DOI:10.1039/C4EN00044G
This study investigated the influence of the structure characteristics of carbon nanotubes (CNTs), such as surface oxygen-containing functional groups, specific surface area (SSA) and concentration of defects, on the adsorption–desorption hysteresis of a metal cation (Cu(II)) and two oxoanions (As(V) and Cr(VI)), from single, double and multi-walled CNTs (SWCNTs, DWCNTs and MWCNTs), and two oxidized MWCNTs with different oxygen concentrations (MWCNTs-O1, 2.51 wt% O and MWCNTs-O2, 3.5 wt% O). Oxygen-containing functional groups contributed to an increase in the adsorption capacity for Cu(II) from aqueous solutions, but a decrease in adsorption capacity for Cr(VI) and As(V). The order of adsorption capacities based on CNT SSA was MWCNTs-O2 > MWCNTs-O1 > MWCNTs > DWCNTs > SWCNTs, which was consistent with the order of CNT defect contents. Desorption hysteresis index (HI) values for Cu(II) increased as the number of functional groups increased. For Cr(VI) and As(V), however, HI values decreased as the number of functional groups increased. HI values decreased with an increase in metal ion surface coverage on CNTs. There may be a shift in the mechanisms of metal ion adsorption by CNTs, from more irreversible to more reversible processes, with an increase in adsorbed metal ions. An understanding of the desorption hysteresis of heavy metal ions is important and useful for the application and risk assessment of CNTs in the natural environment.
Co-reporter:Jie Li ; Changlun Chen ; Juan Wei ; Jiaxing Li
The Journal of Physical Chemistry C 2014 Volume 118(Issue 49) pp:28440-28447
Publication Date(Web):November 18, 2014
DOI:10.1021/jp509182g
Graphene oxides (GOs) were reduced by H2/Ar plasma. Changes in the atom composition and structural properties of reduced GOs (rGOs) were studied as a function of the ratio of H2 to Ar, treatment time, and discharge power by using X-ray photoelectron spectroscopy. The results suggested that the removal of oxygen-containing functional groups and the improvement of electrochemical performance were affected by the ratio of H2 to Ar, treatment time, and discharge power. After plasma treatment, the rGO electrode showed excellent electrochemical stability and an enhanced specific capacitance of 185.2 F g–1 at a scan rate of 100 mV s–1. The present work suggests that H2/Ar plasma treatment provides a reliable method for GO reduction, which can benefit the efficient production of graphene-based electrode materials.
Co-reporter:Shouwei Zhang, Wenqing Xu, Meiyi Zeng, Jie Li, Jiaxing Li, Jinzhang Xu and Xiangke Wang
Journal of Materials Chemistry A 2013 vol. 1(Issue 38) pp:11691-11697
Publication Date(Web):25 Jul 2013
DOI:10.1039/C3TA12767B
Novel hierarchical core–shell iron oxide@magnesium silicate magnetic nanorods (HIO@MgSi) were fabricated via a versatile sol–gel process through hydrothermal reaction. They contain magnetic iron oxide (Fe3O4) cores and hierarchical shells (MgSi) made of ultrathin nanosheets (ca. 5 nm). Using methylene blue as a model compound, the HIO@MgSi nanorods showed fast adsorption kinetics and a superb adsorption capacity. 99.3% of methylene blue was adsorbed onto the surface of the HIO@MgSi nanorods in 40 min contact time. A maximum adsorption capacity of 2020.20 mg g−1 was achieved after 4 h. This study indicated that HIO@MgSi nanorods can be used as a potential super adsorbent to remove cationic organic pollutants effectively and rapidly from large volumes of industrial wastewater or drinking water.
Co-reporter:Tao Wen, Xilin Wu, Xiaoli Tan, Xiangke Wang, and Anwu Xu
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 8) pp:3304
Publication Date(Web):March 25, 2013
DOI:10.1021/am4003556
In this Article, we report a remarkably simple and efficient method for the preparation of layered double hydroxides and graphene oxide (LDHs/GO) nanocomposites with varying GO amounts via a hydrothermal process. The graphene nature in the resulting LDHs/GO nanocomposites was confirmed by X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy, field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), N2 adsorption-desorption, and X-ray photoelectron spectroscopy (XPS). The LDHs/GO nanocomposites exhibited swelling behavior in water and forming a gel. The adsorption performance of the LDHs/GO nanocomposites was evaluated for the removal of arsenate (As(V)) from aqueous solutions, and the results showed that the ratio of GO to LDHs in the nanocomposites significantly affected the adsorption capacity. Higher and lower amounts of GO in LDHs/GO nanocomposites showed lower adsorption capacity of As(V). A maximum adsorption capacity of 183.11 mg/g (2.44 mmol/g) was achieved on the LDHs/GO containing 6.0% GO due to the higher Brunauer–Emmett–Teller (BET) surface area than other samples. Owing to their high uptake capability of As(V), water-swellable LDHs/GO nanocomposites are expected to have potential applications as adsorbents for As(V) polluted water cleanup.Keywords: adsorption; As(V); layered double hydroxides/graphene oxide; nanocomposites;
Co-reporter:Shouwei Zhang, Jiaxing Li, Meiyi Zeng, Guixia Zhao, Jinzhang Xu, Wenping Hu, and Xiangke Wang
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 23) pp:12735
Publication Date(Web):November 19, 2013
DOI:10.1021/am404123z
Water-soluble magnetic-functionalized graphitic carbon nitride (g-C3N4) composites were synthesized successfully by in situ decorating spinel ZnFe2O4 nanoparticles on g-C3N4 sheets (CN-ZnFe) through a one-step solvothermal method. The magnetic properties of CN-ZnFe can be effectively controlled via tuning the coverage density and the size of ZnFe2O4 nanoparticles. The results indicate that the CN-ZnFe exhibits excellent photocatalytic efficiency for methyl orange (MO) and fast separation from aqueous solution by magnet. Interestingly, the catalytic performance of the CN-ZnFe is strongly dependent on the loading of ZnFe2O4. The optimum activity of 160CN-ZnFe photocatalyst is almost 6.4 and 5.6 times higher than those of individual g-C3N4 and ZnFe2O4 toward MO degradation, respectively. By carefully investigating the influence factors, a possible mechanism is proposed and it is believed that the synergistic effect of g-C3N4 and ZnFe2O4, the smaller particle size, and the high solubility in water contribute to the effective electron–hole pairs separation and excellent photocatalytic efficiency. This work could provide new insights that g-C3N4 sheets function as good support to develop highly efficient g-C3N4-based magnetic photocatalysts in environmental pollution cleanup.Keywords: charge separation; degradation; g-C3N4/ZnFe2O4; highly water dispersible; photocatalytic activity; tunable magnetic properties;
Co-reporter:Yubing Sun, Dadong Shao, Changlun Chen, Shubin Yang, and Xiangke Wang
Environmental Science & Technology 2013 Volume 47(Issue 17) pp:9904-9910
Publication Date(Web):July 31, 2013
DOI:10.1021/es401174n
Graphene oxide-supported polyaniline (PANI@GO) composites were synthesized by chemical oxidation and were characterized by SEM, Raman and FT-IR spectroscopy, TGA, potentiometric titrations, and XPS. The characterization indicated that PANI can be grafted onto the surface of GO nanosheets successfully. The sorption of U(VI), Eu(III), Sr(II), and Cs(I) from aqueous solutions as a function of pH and initial concentration on the PANI@GO composites was investigated. The maximum sorption capacities of U(VI), Eu(III), Sr(II), and Cs(I) on the PANI@GO composites at pH 3.0 and T = 298 K calculated from the Langmuir model were 1.03, 1.65, 1.68, and 1.39 mmol·g–1, respectively. According to the XPS analysis of the PANI@GO composites before and after Eu(III) desorption, nitrogen- and oxygen-containing functional groups on the surface of PANI@GO composites were responsible for radionuclide sorption, and that radionuclides can hardly be extracted from the nitrogen-containing functional groups. Therefore, the chemical affinity of radionuclides for nitrogen-containing functional groups is stronger than that for oxygen-containing functional groups. This paper focused on the application of PANI@GO composites as suitable materials for the preconcentration and removal of lanthanides and actinides from aqueous solutions in environmental pollution management in a wide range of acidic to alkaline conditions.
Co-reporter:Shouwei Zhang, Wenqing Xu, Meiyi Zeng, Jiaxing Li, Jinzhang Xu and Xiangke Wang
Dalton Transactions 2013 vol. 42(Issue 37) pp:13417-13424
Publication Date(Web):01 Jul 2013
DOI:10.1039/C3DT51492G
Wide spectral responsive 3D hierarchical CdS/α-Fe2O3 heterojunction nanocomposites were synthesized through a facile chemical bath method under mild conditions, and used for the reduction of Cr(VI) into Cr(III) under visible light irradiation. The effects of CdS/α-Fe2O3 molar ratio in the nanocomposites on the crystal phases, microstructures, optical absorption properties, and photocatalytic reduction of Cr(VI) were investigated comparatively. It was found that the as-synthesized CdS/α-Fe2O3 nanocomposites with a suitable CdS content (e.g., the molar ratio of Fe:Cd = 1.25:3) had not only high visible-light-driven photocatalytic activity in the Cr(VI) reduction, but also good photocatalytic stability. The enhanced photocatalytic activity can be ascribed to some CdS nanoparticles closely contacting the α-Fe2O3 microflowers to form a heterojunction structure. These tight heterojunctions of the photocatalysts result in an efficient electron–hole pairs separation at the interface, followed by fast diffusion of photogenerated charge between CdS and α-Fe2O3, which is beneficial for separating the photogenerated carriers in space and improving the photocatalytic activity.
Co-reporter:Xiaoli Tan, Xuemei Ren, Jiaxing Li and Xiangke Wang
RSC Advances 2013 vol. 3(Issue 42) pp:19551-19559
Publication Date(Web):12 Aug 2013
DOI:10.1039/C3RA42853B
We herein report density functional investigations of uranyl adsorption on γ-Al2O3 surfaces. By applying periodic slab models, we report the possible configurations of uranyl adsorbed on the (100) and (110) surfaces of γ-Al2O3 by calculations using density functional theory. The above mentioned two surfaces are expected to be highly reactive and adsorb metal ions preferentially. We explored bidentate inner-sphere adsorption complexes of uranyl at short-bridge sites, AlOO, and long-bridge sites, AlOAlO(H). The results indicate several favorable adsorption configurations which fit the available TRLFS and EXAFS data well. Comparison of key calculated structure parameters with available experimental data suggests an extension of the prevailing interpretation and implies that a set of uranyl complexes may coexist on the edge surfaces of γ-Al2O3.
Co-reporter:Guixia Zhao, Jiaxing Li, Xuemei Ren, Jun Hu, Wenping Hu and Xiangke Wang
RSC Advances 2013 vol. 3(Issue 31) pp:12909-12914
Publication Date(Web):10 May 2013
DOI:10.1039/C3RA40942B
In this paper, a facile one-step method towards manganese oxide nanosheets is described which uses graphene oxide as a self-sacrificial template. A redox reaction between graphene oxide nanosheets and KMnO4 results in the formation of few-layer MnO2 nanosheets due to the in situ replacement of the carbon framework by edge-sharing [MnO6] octahedra. It is also demonstrated that these MnO2 nanosheets show high activity for the oxidative degradation of methylene blue (MB) dye, in which the MB dye can be decomposed into small molecule fragments through fast demethylation, followed by aromatic ring cracking, and partial mineralization into inorganic ions in a short time. We expect that the few-layer MnO2 nanosheets may be envisaged as a new non-toxic material for the treatment of organic dye-containing wastewater, and its application for the oxidation of other organic pollutants in environmental pollution cleanup.
Co-reporter:Shouwei Zhang, Jiaxing Li, Tao Wen, Jinzhang Xu and Xiangke Wang
RSC Advances 2013 vol. 3(Issue 8) pp:2754-2764
Publication Date(Web):18 Dec 2012
DOI:10.1039/C2RA22495J
Uniform three-dimensional (3D) flowerlike Fe3O4@NiO hierarchical architectures were synthesized by a simple and direct solvothermal route without any linker shell. The shell thickness and hierarchical structure of the microspheres can be tuned by adjusting the reaction duration. The size of the hierarchical microspheres is 250–300 nm and the shell is composed of several nanoflakes with a thickness of 20–30 nm and a width of 50–60 nm. The microspheres possess high specific surface area of 125.63 m2 g−1 and high saturation magnetization, which allows them to have strong removal ability and are easily separated from solution by magnetic separation method. The microspheres are applied as adsorbents for As(V) and Cr(VI) ions removal from wastewater, and exhibit a high adsorption capacity with an adsorption capacity of ∼117.6 mg g−1 for As(V) and 184.2 mg g−1 for Cr(VI), which is mainly attributed to the large specific surface area and hierarchical structures of Fe3O4@NiO hierarchical microspheres. This work provides a promising approach for the design and synthesis of multifunctional microspheres, which can be used for water treatment, as well as having other potential applications in a variety of biomedical fields including drug delivery and biosensors.
Co-reporter:Dr. Qi Wang;Dr. Jiaxing Li;Dr. Ye Song ; Xiangke Wang
Chemistry – An Asian Journal 2013 Volume 8( Issue 1) pp:225-231
Publication Date(Web):
DOI:10.1002/asia.201200782
Abstract
High-quality reduced graphene, termed PG, has been synthesized by a simple, low-cost, and green plasma approach, and applied as adsorbent to remove 4,4′-dichloribiphenyl (4,4′-DCB) from aqueous solutions. As a comparison, the adsorption of 4,4′-DCB on graphene oxide (GO) and multiwalled carbon nanotubes (MWCNTs) was also studied under the same experimental conditions. PG performs significantly better with regard to 4,4′-DCB adsorption than GO and MWCNTs, or any reported nanomaterials, with a maximum adsorption capacity (qmax) of 1552 mg g−1 at pH 7.0. The high affinity of 4,4′-DCB to PG is mainly a result of strong π–π interactions, as also confirmed by DFT calculations. The results reveal that PG sheets hold promise for the removal of persistent organic pollutants. We expect possible applications of this fast and mild plasma technique in the fabrication of nanomaterials and envisage their use in a variety of advanced chemical processes.
Co-reporter:Xi-Lin Wu, Tao Wen, Hong-Li Guo, Shubin Yang, Xiangke Wang, and An-Wu Xu
ACS Nano 2013 Volume 7(Issue 4) pp:3589
Publication Date(Web):April 2, 2013
DOI:10.1021/nn400566d
As a newly developed material, carbon gels have been receiving considerable attention due to their multifunctional properties. Herein, we present a facile, green, and template-free route toward sponge-like carbonaceous hydrogels and aerogels by using crude biomass, watermelon as the carbon source. The obtained three-dimensional (3D) flexible carbonaceous gels are made of both carbonaceous nanofibers and nanospheres. The porous carbonaceous gels (CGs) are highly chemically active and show excellent mechanical flexibility which enable them to be a good scaffold for the synthesis of 3D composite materials. We synthesized the carbonaceous gel-based composite materials by incorporating Fe3O4 nanoparticles into the networks of the carbonaceous gels. The Fe3O4/CGs composites further transform into magnetite carbon aerogels (MCAs) by calcination. The MCAs keep the porous structure of the original CGs, which allows the sustained and stable transport of both electrolyte ions and electrons to the electrode surface, leading to excellent electrochemical performance. The MCAs exhibit an excellent capacitance of 333.1 F·g–1 at a current density of 1 A·g–1 within a potential window of −1.0 to 0 V in 6 M KOH solution. Meanwhile, the MCAs also show outstanding cycling stability with 96% of the capacitance retention after 1000 cycles of charge/discharge. These findings open up the use of low-cost elastic carbon gels for the synthesis of other 3D composite materials and show the possibility for the application in energy storage.Keywords: aerogel; carbon materials; hydrogel; mechanical properties; supercapacitors
Co-reporter:Yubing Sun;Shubin Yang;Guixia Zhao;Qi Wang
Chemistry – An Asian Journal 2013 Volume 8( Issue 11) pp:2755-2761
Publication Date(Web):
DOI:10.1002/asia.201300496
Abstract
Graphene has attracted increasing attention in multidisciplinary studies because of its unique physical and chemical properties. Herein, the adsorption of polycyclic aromatic hydrocarbons (PAHs), such as naphthalene (NAP), anthracene (ANT), and pyrene (PYR), on reduced graphene oxides (rGOs) and graphene oxides (GOs) as a function of pH, humic acid (HA), and temperature were elucidated by means of a batch technique. For comparison, nonpolar and nonporous graphite were also employed in this study. The increasing of pH from 2 to 11 did not influence the adsorption of PAHs on rGOs, whereas the suppressed adsorption of NAP on rGOs was observed both in the presence of HA and under high-temperature conditions. Adsorption isotherms of PAHs on rGOs were in accordance with the Polanyi–Dubinin–Ashtahhov (PDA) model, providing evidence that pore filling and flat surface adsorption were involved. The saturated adsorbed capacities (in mmol g−1) of rGOs for PAHs calculated from the PDA model significantly decreased in the order of NAP>PYR>ANT, which was comparable to the results of theoretical calculations. The pore-filling mechanism dominates the adsorption of NAP on rGOs, but the adsorption mechanisms of ANT and PYR on rGOs are flat surface adsorption.
Co-reporter:Shouwei Zhang;Dr. Jiaxing Li;Haihong Niu;Dr. Wenqing Xu; Jinzhang Xu; Wenping Hu; Xiangke Wang
ChemPlusChem 2013 Volume 78( Issue 2) pp:192-199
Publication Date(Web):
DOI:10.1002/cplu.201200272
Abstract
Three-dimensional SnO2/α-Fe2O3 semiconductor hierarchical nanoheterostructures were synthesized for photocatalysis through a low-cost and environmentally friendly hydrothermal strategy, by crystallographic-oriented epitaxial growth of SnO2 on three-dimensional α-Fe2O3 flowerlike hierarchical nanostructures. In this photocatalyst, visible-light-active Fe2O3 flowerlike hierarchical nanostructures were used as a medium to absorb photons and convert them into photogenerated charges, and SnO2 nanoparticles were used as charge collectors to transport the photogenerated charges. The SnO2/α-Fe2O3 semiconductor hierarchical nanoheterostructures exhibited excellent visible-light photocatalytic ability for the degradation of methylene blue; this was attributed to the large specific surface area, wide visible-light absorption range, and efficient electron–hole pair separation properties of the SnO2/α-Fe2O3 nanoheterostructures. The SnO2/α-Fe2O3 material showed improved separation of photogenerated electron–hole pairs owing to the potential-energy differences between SnO2 and α-Fe2O3, and therefore exhibited enhanced photocatalytic activity. This paper highlights the SnO2/α-Fe2O3 semiconductor hierarchical nanoheterostructures as potentially more environmentally friendly materials for use in organic pollutant degradation for environmental pollution cleanup operations.
Co-reporter:Guixia Zhao, Jiaxing Li, Lang Jiang, Huanli Dong, Xiangke Wang and Wenping Hu
Chemical Science 2012 vol. 3(Issue 2) pp:433-437
Publication Date(Web):14 Oct 2011
DOI:10.1039/C1SC00722J
A facile method to synthesize layered manganese oxide nanosheets was developed for the first time by using graphene oxide as a template. The in situ replacement of carbon atoms on the graphene oxide framework by edge-shared [MnO6] octahedra provides a new methodology to synthesize graphene-based two-dimensional nanomaterials. The transformation of graphene oxide into δ-type MnO2 nanosheets results in an especially high surface area (157 m2 g−1), which is the highest value amongst today's MnO2 nanomaterials. Moreover, the MnO2 nanosheets demonstrated prominent capacitance (∼1017 F g−1 at a scan rate of 3 mV s−1, and ∼1183 F g−1 at a current density of 5 A g−1) and remarkable rate capability (∼244 F g−1 at a high scan rate of 50 mV s−1 and ∼559 F g−1 at a high current density of 25 A g−1), indicating their promise in high energy and power density pseudosupercapacitors.
Co-reporter:Shubin Yang, Xilin Wu, Changlun Chen, Huanli Dong, Wenping Hu and Xiangke Wang
Chemical Communications 2012 vol. 48(Issue 22) pp:2773-2775
Publication Date(Web):18 Jan 2012
DOI:10.1039/C2CC16565A
This work reports a new graphene-based composite for supercapacitor material, and the maximum specific capacitance of 1760.72 F g−1 at a scan rate of 5 mV s−1, with excellent cycling stability.
Co-reporter:Shitong Yang, Pengfei Zong, Xuemei Ren, Qi Wang, and Xiangke Wang
ACS Applied Materials & Interfaces 2012 Volume 4(Issue 12) pp:6891
Publication Date(Web):November 26, 2012
DOI:10.1021/am3020372
In this study, humic acid-coated Fe3O4 magnetic nanoparticles (Fe3O4@HA MNPs) were synthesized using a chemical coprecipitation method and characterized in detail. The XRD analysis results showed that HA coating did not change the phase of Fe3O4 cores. The TEM image suggested that Fe3O4@HA MNPs had nearly uniform size without the observation of aggregation. The Fe3O4@HA MNPs were stable in solution and could be easily separated from aqueous solution using a magnetic separation method. A batch technique was adopted to investigate the removal efficiency of Fe3O4@HA MNPs toward Eu(III) under various environmental conditions. The kinetic process of Eu(III) sorption on Fe3O4@HA MNPs reached equilibrium within <30 min. The fast sorption kinetics and high sorption amount were attributed to the plentiful surface sites provided by the surface-coated HA macromolecules. The Fe3O4@HA MNPs was able to remove ∼99% of Eu(III) in aqueous solution at pH 8.5. Except for SO42– anions, the coexisting electrolyte ions had no significant competition effects on the removal of Eu(III) by Fe3O4@HA MNPs. The obvious sorption–desorption hysteresis suggested that the removal of Eu(III) was dominated by inner-sphere surface complexation. The sorption isotherm agreed well with the Langmuir model, having a maximum sorption capacity of 6.95 × 10–5 mol g–1. The leaching test showed that the Eu(III)-loaded Fe3O4@HA colloids were capable to maintain high thermodynamic stability for long aging times. The findings herein suggested that Fe3O4@HA MNPs could be potentially used as a highly effective material for the enrichment and preconcentration of radionuclide Eu(III) or other trivalent lanthanides/actinides in geological repositories or in nuclear waste management.Keywords: Eu(III); Fe3O4@HA MNPs; geological repository; magnetic separation; material stability; sorption reversibility;
Co-reporter:Yubing Sun, Qi Wang, Changlun Chen, Xiaoli Tan, and Xiangke Wang
Environmental Science & Technology 2012 Volume 46(Issue 11) pp:6020-6027
Publication Date(Web):May 2, 2012
DOI:10.1021/es300720f
The interaction mechanism between Eu(III) and graphene oxide nanosheets (GONS) was investigated by batch and extended X-ray absorption fine structure (EXAFS) spectroscopy and by modeling techniques. The effects of pH, ionic strength, and temperature on Eu(III) adsorption on GONS were evaluated. The results indicated that ionic strength had no effect on Eu(III) adsorption on GONS. The maximum adsorption capacity of Eu(III) on GONS at pH 6.0 and T = 298 K was calculated to be 175.44 mg·g–1, much higher than any currently reported. The thermodynamic parameters calculated from temperature-dependent adsorption isotherms suggested that Eu(III) adsorption on GONS was an endothermic and spontaneous process. Results of EXAFS spectral analysis indicated that Eu(III) was bound to ∼6–7 O atoms at a bond distance of ∼2.44 Å in the first coordination shell. The value of Eu–C bond distance confirmed the formation of inner-sphere surface complexes on GONS. Surface complexation modeling gave an excellent fit with the predominant mononuclear monodentate >SOEu2+ and binuclear bidentate (>SO)2Eu2(OH)22+ complexes. This paper highlights the application of GONS as a suitable material for the preconcentration and removal of trivalent lanthanides and actinides from aqueous solutions in environmental pollution management.
Co-reporter:Yubing Sun, Changlun Chen, Xiaoli Tan, Dadong Shao, Jiaxing Li, Guixia Zhao, Shubin Yang, Qi Wang and Xiangke Wang
Dalton Transactions 2012 vol. 41(Issue 43) pp:13388-13394
Publication Date(Web):03 Sep 2012
DOI:10.1039/C2DT31510F
Mesoporous Al2O3 was intercalated into an expanded graphite (EG) interlayer to prepare mesoporous Al2O3/EG composites. The basal spacing of mesoporous Al2O3/EG composites was enlarged as compared to raw graphite from the X-ray diffraction analysis. The massive surface functional groups and wedge-shaped pores were observed in terms of potentiometric acid–base titration analysis and scanning electron microscope, respectively. The pH-dependent adsorption of Eu(III) on mesoporous Al2O3/EG composites was evidently independent of ionic strength. The maximum adsorption capacity of Eu(III) on mesoporous Al2O3/EG composites at pH 6.0 and T = 293 K was calculated to be 5.14 mg g−1. Desorption kinetics and cyclic operation results showed that mesoporous Al2O3/EG composites presented high hydrothermal stability in aqueous solution. The thermodynamic parameters suggested that Eu(III) adsorption on mesoporous Al2O3/EG composites is an endothermic and a spontaneous process. The decrease of Eu–O bond distance with the increasing pH demonstrated that the adsorption mechanism between Eu(III) and mesoporous Al2O3/EG composites would shift from outer-sphere surface complexation to inner-sphere surface complexation in terms of extended X-ray absorption fine structure spectroscopy analysis.
Co-reporter:Jun Hu, Xiaoli Tan, Xuemei Ren and Xiangke Wang
Dalton Transactions 2012 vol. 41(Issue 35) pp:10803-10810
Publication Date(Web):29 Jun 2012
DOI:10.1039/C2DT31057K
The influence of humic acid (HA) on Ni(II) sorption to Ca-montmorillonite was examined by using a combination of batch sorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The sorption of Ni(II) on HA–montmorillonite hybrids is strongly dependent on pH and temperature. At low pH, the sorption of Ni(II) is mainly dominated by Ni–HA–montmorillonite and outer-sphere surface complexation. The EXAFS results indicate that the first coordination shell of Ni(II) consists of ∼6 O atoms at the interatomic distances of ∼2.04 Å in an octahedral structure. At high pH, binary Ni–montmorillonite surface complexation is the dominant sorption mechanism. EXAFS analysis indicates the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5, while a Ni–Al layered double hydroxide (LDH) phase at the Ca-montmorillonite surface formed with pH 8.5. At pH 10.0, the dissolved HA–Ni(II) complexation inhibits the precipitation of Ni hydroxide, and Ni–Al LDH phase forms. The rise of temperature increases the sorption capacity of Ni(II), and promotes Ni–Al LDH phase formation and the growth of crystallites. The results are important to evaluate the physicochemical behavior of Ni(II) in the natural environment.
Co-reporter:Guodong Sheng, Yimin Li, Xin Yang, Xuemei Ren, Shitong Yang, Jun Hu and Xiangke Wang
RSC Advances 2012 vol. 2(Issue 32) pp:12400-12407
Publication Date(Web):08 Oct 2012
DOI:10.1039/C2RA21623J
The magnetic graphene oxide (MGO) composites were prepared by coprecipitation of FeCl3·6H2O and FeCl2·4H2O on graphene oxide (GO) nanosheets and characterized in detail. The Fe3O4 was uniformly deposited on the surface of GO. The synthesized MGO composites were used as a versatile adsorbent for As(V) removal from aqueous solutions. The results showed that the adsorption of As(V) on MGO is an endothermic process and the adsorption kinetic fitted the pseudo-second-order model well. The MGO composites had a good adsorption capability for As(V) removal and the adsorption isotherms were described by the Langmuir model better than by the Freundlich model. The adsorption of As(V) on MGO decreased with ascending pH due to the electrostatic interaction. In addition, the adsorption of As(V) on MGO was greatly affected by the nature and concentration of coexisting cations and anions. The presence of coexisting anions showed an inhibiting effect on As(V) adsorption, which was more efficient at low pH, whereas the presence of coexisting cations showed an enhancing effect on As(V) adsorption, which was more efficient at high pH. The results of this work indicated that the combination of the excellent adsorption capacity of GO and the magnetic properties of Fe3O4 nanoparticles is very important in drinking water treatment due to the easy magnetic separation of MGO from aqueous solutions.
Co-reporter:Yubing Sun, Changlun Chen, Dadong Shao, Jiaxing Li, Xiaoli Tan, Guixia Zhao, Shubin Yang and Xiangke Wang
RSC Advances 2012 vol. 2(Issue 27) pp:10359-10364
Publication Date(Web):05 Sep 2012
DOI:10.1039/C2RA21713A
Adsorption of ionizable aromatic compounds (IACs) such as 1-naphthylamine and 1-naphthol on Humic acid (HA)-coated graphene oxide nanosheets (GONs), multiwalled carbon nanotubes (MWCNTs), activated carbon (AC), and flake graphite (FG) were investigated by the batch techniques. The adsorption of 1-naphthylamine on four HA-coated carbonaceous adsorbents was weakly depended on pH, whereas the adsorption of 1-naphthol on these HA-coated carbonaceous adsorbents evidently increased with increasing pH from 2.0 to 8.0. The maximum adsorption capacity of HA-coated carbonaceous adsorbents for IACs was in the order of GONs≫MWCNTs>AC>FG, indicating that the GONs can be regarded as a suitable material for the preconcentration and removal of IACs from aqueous solution in environmental pollution management. The main adsorption mechanism between carbonaceous adsorbents and IACs is the hydrophobic effect. This observation is of great implication for the removal of IACs by HA-coated carbonaceous adsorbents in environmental applications.
Co-reporter:Guixia Zhao, Tao Wen, Changlun Chen and Xiangke Wang
RSC Advances 2012 vol. 2(Issue 25) pp:9286-9303
Publication Date(Web):26 Jul 2012
DOI:10.1039/C2RA20990J
As a fascinating two-dimensional carbon allotrope, graphene has triggered a ‘gold rush’ all over scientific research areas especially since the Nobel Prize for Physics in 2010. To exploit the prominent properties of graphene-based nanomaterials, two important problems are focused in this review: one is the synthesis of these graphene-based nanomaterials with different kinds of well-defined structures, and the other is the effective application of them as active nanomaterials in functional devices or processes. In this critical review, from the viewpoint of chemistry and materials, we give a brief overview of the recent significant advances in the synthesis of graphene-based nanomaterials and their applications in energy-related areas and environmental pollution remediation areas, including supercapacitors, lithium ion batteries, solar cells, adsorption, and degradation of organic/inorganic pollutants from large volumes of aqueous solutions in environmental pollution cleanup. The main challenges and perspectives of the materials for future research are also discussed.
Co-reporter:Xin Yang, Changlun Chen, Jiaxing Li, Guixia Zhao, Xuemei Ren and Xiangke Wang
RSC Advances 2012 vol. 2(Issue 23) pp:8821-8826
Publication Date(Web):26 Jul 2012
DOI:10.1039/C2RA20885G
Graphene oxide (GO) and reduced graphene oxide (RGO) were both decorated with iron oxide nanoparticles and were characterized by scanning and transmission electron microscopy, powder X-ray diffraction, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The adsorption of Pb(II), 1-naphthol, and 1-naphthylamine, as representatives of inorganic and organic pollutants, on GO-iron oxides and RGO-iron oxides was investigated. The results showed that the GO-iron oxide material was a good adsorbent for Pb(II) but not for 1-naphthol and 1-naphthylamine due to oxygen-containing groups on the surface, whereas the RGO-iron oxide material was a good adsorbent for 1-naphthol and 1-naphthylamine but not for Pb(II). The adsorption of 1-naphthol and 1-naphthylamine on RGO-iron oxides was an endothermic and spontaneous process. Both materials can be easily separated by magnetic separation.
Co-reporter:Jun Hu;Shitong Yang
Journal of Chemical Technology and Biotechnology 2012 Volume 87( Issue 5) pp:673-681
Publication Date(Web):
DOI:10.1002/jctb.2764
Abstract
BACKGROUND: The adsorption of Cu(II) on β-cyclodextrin (β-CD) modified multiwall carbon nanotubes/iron oxides (denoted as MWCNT/IO/CD) as a function of contact time, pH, adsorbent content, temperature, fulvic acid (FA) and initial Cu(II) concentrations was investigated using a batch technique under ambient conditions.
RESULTS: The adsorption of Cu(II) was strongly dependent on pH, adsorbent content, temperature and FA. A positive effect of FA on Cu(II) adsorption was found at pH < 6.5, whereas a negative effect was observed at pH > 6.5. Different effects of FA/Cu(II) concentrations on Cu(II) and FA adsorption were observed, indicating enhanced Cu(II) adsorption on FA bound MWCNT/IO/CD, whereas FA adsorption was decreased in the presence of Cu(II) ions. The adsorption isotherms were well fitted by the linear isotherm model. The adsorption thermodynamic parameters calculated from temperature dependent adsorption isotherms suggested that the adsorption of Cu(II) on MWCNT/IO/CD was an endothermic and spontaneous process.
CONCLUSIONS: MWCNT/IO/CD is a promising magnetic material for the preconcentration and separation of Cu(II) ions from aqueous solutions in environmental pollution cleanup. Copyright © 2011 Society of Chemical Industry
Co-reporter:Dr. Qi Wang;Mingming Song;Dr. Changlun Chen; Wenping Hu; Xiangke Wang
ChemPlusChem 2012 Volume 77( Issue 6) pp:432-436
Publication Date(Web):
DOI:10.1002/cplu.201200070
Co-reporter:XueMei Ren;ShiTong Yang;XiaoLi Tan;ChangLun Chen
Science China Chemistry 2012 Volume 55( Issue 9) pp:1752-1759
Publication Date(Web):2012 September
DOI:10.1007/s11426-012-4694-7
The interaction between radionuclides and solid/water interfaces is important to understand the physicochemical processes of radionuclides in the natural environment. Herein, the interaction of 60Co(II) with TiO2 in aqueous solution as a function of pH and ionic strength was studied by using batch technique combined with surface complexation model and density functional theory (DFT) calculations. The batch experimental results showed that the adsorption of 60Co(II) was dependent on pH and independent of ionic strength, indicating the formation of inner-sphere surface complexes on TiO2 surfaces. The results of surface complexation models and DFT calculations indicated that the surface species of 60Co(II) adsorbed on TiO2 followed the trend: B structure (i.e., 60Co(II) was linked to one bridge oxygen site) was the dominant surface species at low pH, and TT structure (i.e., 60Co(II) was linked to two terminal oxygen sites) became the important surface complex at neutral and alkaline pH values. These results demonstrated that a multi-technique approach could lead to definitive information on the structures of adsorbed 60Co(II) at the molecular level at the TiO2/water interfaces, as well as realistic models to rationalize and accurately evaluate the macroscopic manifestations of radionuclide adsorption phenomena.
Co-reporter:Kui Lü;GuiXia Zhao
Science Bulletin 2012 Volume 57( Issue 11) pp:1223-1234
Publication Date(Web):2012 April
DOI:10.1007/s11434-012-4986-5
Graphene is an interesting two-dimensional carbon allotrope that has attracted considerable research interest because of its unique structure and physicochemical properties. Studies have been conducted on graphene-based nanomaterials including modified graphene, graphene/semiconductor hybrids, graphene/metal nanoparticle composites, and graphene-complex oxide composites. These nanomaterials inherit the unique properties of graphene, and the addition of functional groups or the nanoparticle composites on their surfaces improves their performance. Applications of these materials in pollutant removal and environmental remediation have been explored. From the viewpoint of environmental chemistry and materials, this paper reviews recent important advances in synthesis of graphene-related materials and their application in treatment of environmental pollution. The roles of graphene-based materials in pollutant removal and potential research are discussed.
Co-reporter:Guixia Zhao;Lang Jiang;Yudong He;Jiaxing Li;Huanli Dong;Wenping Hu
Advanced Materials 2011 Volume 23( Issue 34) pp:3959-3963
Publication Date(Web):
DOI:10.1002/adma.201101007
Co-reporter:Xi-Lin Wu, Lei Wang, Chang-Lun Chen, An-Wu Xu and Xiang-Ke Wang
Journal of Materials Chemistry A 2011 vol. 21(Issue 43) pp:17353-17359
Publication Date(Web):23 Sep 2011
DOI:10.1039/C1JM12678D
A composite material, containing magnetite particles, graphene and layered double hydroxides (LDHs) was fabricated through a simple two-step reaction. Graphene was used as the matrix for supporting magnetite particles and LDH nanoplates. The synthesized magnetite-graphene-LDH (MGL) composites were characterized by field emission scanning electron microscopic (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transformed infrared (FTIR) spectroscopy, N2adsorption-desorption, and X-ray photoelectron spectroscopy (XPS). The MGL composites were applied to remove arsenate from aqueous solutions and could be easily separated by magnetic separation process. The results showed enhanced adsorption capacity of arsenate on the MGL as compared to that of pure Mg/Al LDHs. The surface area of MGL is greatly enhanced through the incorporation of magnetite particles and graphene, which provides more active sites for arsenate uptake. Moreover, LDHs were hybridized with mechanically and chemically stable graphene materials, providing an accessible diffusion pathway in the macropore domain, and therefore their adsorption capacity was enhanced. The fast and efficient adsorption of arsenate from solution to MGL suggests that the MGL composites are potential and suitable materials in the preconcentration of arsenate from large volumes of aqueous solutions in wastewater treatment.
Co-reporter:Shubin Yang, Jun Hu, Changlun Chen, Dadong Shao, and Xiangke Wang
Environmental Science & Technology 2011 Volume 45(Issue 8) pp:3621-3627
Publication Date(Web):March 11, 2011
DOI:10.1021/es104047d
This paper examines the adsorption of Pb(II) and a natural organic macromolecular compound (humic acid, HA) on polyacrylamide (PAAM) -grafted multiwalled carbon nanotubes (denoted as MWCNTs/PAAM), prepared by an N2-plasma-induced grafting technique. The mutual effects of HA/Pb(II) on Pb(II) and HA adsorption on MWCNTs/PAAM, as well as the effects of pH, ionic strength, HA/Pb(II) concentrations, and the addition sequences of HA/Pb(II) were investigated. The results indicated that Pb(II) and HA adsorption were strongly dependent on pH and ionic strength. The presence of HA led to a strong increase in Pb(II) adsorption at low pH and a decrease at high pH, whereas the presence of Pb(II) led to an increase in HA adsorption. The adsorbed HA contributed to modification of adsorbent surface properties and partial complexation of Pb(II) with the adsorbed HA. Different effects of HA/Pb(II) concentrations and addition sequences on Pb(II) and HA adsorption were observed, indicating different adsorption mechanisms. After adsorption of HA on MWCNTs/PAAM, the adsorption capacity for Pb(II) was enhanced at pH 5.0; the adsorption capacity for HA was also enhanced after Pb(II) adsorption on MWCNTs/PAAM. These results are important for estimating and optimizing the removal of metal ions and organic substances by use of MWCNT/PAAM composites.
Co-reporter:Guodong Sheng, Shitong Yang, Jiang Sheng, Jun Hu, Xiaoli Tan, and Xiangke Wang
Environmental Science & Technology 2011 Volume 45(Issue 18) pp:7718-7726
Publication Date(Web):August 19, 2011
DOI:10.1021/es202108q
Sequestration of Ni(II) on diatomite as a function of time, pH, and temperature was investigated by batch, XPS, and EXAFS techniques. The ionic strength-dependent sorption at pH < 7.0 was consistent with outer-sphere surface complexation, while the ionic strength-independent sorption at pH = 7.0–8.6 was indicative of inner-sphere surface complexation. EXAFS results indicated that the adsorbed Ni(II) consisted of ∼6 O at RNi–O ≈ 2.05 Å. EXAFS analysis from the second shell suggested that three phenomena occurred at the diatomite/water interface: (1) outer-sphere and/or inner-sphere complexation; (2) dissolution of Si which is the rate limiting step during Ni uptake; and (3) extensive growth of surface (co)precipitates. Under acidic conditions, outer-sphere complexation is the main mechanism controlling Ni uptake, which is in good agreement with the macroscopic results. At contact time of 1 h or 1 day or pH = 7.0–8.0, surface coprecipitates occur concurrently with inner-sphere complexes on diatomite surface, whereas at contact time of 1 month or pH = 10.0, surface (co)precipitates dominate Ni uptake. Furthermore, surface loading increases with temperature increasing, and surface coprecipitates become the dominant mechanism at elevated temperature. The results are important to understand Ni interaction with minerals at the solid–water interface, which is helpful to evaluate the mobility of Ni(II) in the natural environment.
Co-reporter:Guixia Zhao, Jiaxing Li, Xuemei Ren, Changlun Chen, and Xiangke Wang
Environmental Science & Technology 2011 Volume 45(Issue 24) pp:10454-10462
Publication Date(Web):November 9, 2011
DOI:10.1021/es203439v
Graphene has attracted multidisciplinary study because of its unique physicochemical properties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using the modified Hummers method, and were used as sorbents for the removal of Cd(II) and Co(II) ions from large volumes of aqueous solutions. The effects of pH, ionic strength, and humic acid on Cd(II) and Co(II) sorption were investigated. The results indicated that Cd(II) and Co(II) sorption on graphene oxide nanosheets was strongly dependent on pH and weakly dependent on ionic strength. The abundant oxygen-containing functional groups on the surfaces of graphene oxide nanosheets played an important role on Cd(II) and Co(II) sorption. The presence of humic acid reduced Cd(II) and Co(II) sorption on graphene oxide nanosheets at pH < 8. The maximum sorption capacities (Csmax) of Cd(II) and Co(II) on graphene oxide nanosheets at pH 6.0 ± 0.1 and T = 303 K were about 106.3 and 68.2 mg/g, respectively, higher than any currently reported. The thermodynamic parameters calculated from temperature-dependent sorption isotherms suggested that Cd(II) and Co(II) sorptions on graphene oxide nanosheets were endothermic and spontaneous processes. The graphene oxide nanosheets may be suitable materials in heavy metal ion pollution cleanup if they are synthesized in large scale and at low price in near future.
Co-reporter:Guixia Zhao, Xuemei Ren, Xing Gao, Xiaoli Tan, Jiaxing Li, Changlun Chen, Yuying Huang and Xiangke Wang
Dalton Transactions 2011 vol. 40(Issue 41) pp:10945-10952
Publication Date(Web):14 Sep 2011
DOI:10.1039/C1DT11005E
Few-layered graphene oxide (FGO) was synthesized from graphite by using the modified Hummers method, and was characterized by scanning electron microscopy, atomic force microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. The prepared FGO was used to adsorb Pb(II) ions from aqueous solutions. The abundant oxygen-containing groups on the surfaces of FGO played an important role in Pb(II) ion adsorption on FGO. The adsorption of Pb(II) ions on FGO was dependent on pH values and independent of ionic strength. The adsorption of Pb(II) ions on FGO was mainly dominated by strong surface complexation. From the adsorption isotherms, the maximum adsorption capacities (Csmax) of Pb(II) ions on FGO calculated from the Langmuir model were about 842, 1150, and 1850 mg g−1 at 293, 313, and 333 K, respectively, higher than any currently reported. The FGO had the highest adsorption capacities of today's nanomaterials. The thermodynamic parameters calculated from the temperature dependent adsorption isotherms indicated that the adsorption of Pb(II) ions on FGO was a spontaneous and endothermic process.
Co-reporter:XiaoLi Tan, Jun Hu, Gilles Montavon and XiangKe Wang
Dalton Transactions 2011 vol. 40(Issue 41) pp:10953-10960
Publication Date(Web):14 Sep 2011
DOI:10.1039/C1DT10740B
The sorption speciation of Ni(II) on Ca-montmorillonite was evaluated using a combination of batch experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy and modeling. The pH and temperature at the aqueous-montmorillonite interface affects both the extent of Ni(II) sorption as well as the local atomic structure of the adsorbed Ni(II) ions. At 0.001 mol L−1 Ca(NO3)2 and low pH, the study reveals that the majority of Ni(II) is adsorbed in the interlayers of Ca-montmorillonite coordinated by six water molecules in an octahedron as an outer-sphere complex. At higher pH, inner-sphere surface complexes are formed. The Ni–Si/Al distances (RNi–Al = 3.00 Å, RNi–Si1 = 3.10 Å and RNi–Si2 = 3.26 Å) determined by EXAFS confirm the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5 and 8.5. At pH 10.0, the Ni–Ni/Si distances (RNi–Ni = 3.07 Å and RNi–Si = 3.26 Å) indicates the formation of Ni-phyllosilicate precipitates. A rise in temperature promotes inner-sphere complexation, which in turn leads to an increase in Ni(II) sorption on Ca-montmorillonite. Sorption edges are fitted excellently by surface complexation model (SCM) with the aid of surface species determined from EXAFS spectroscopy.
Co-reporter:Guodong Sheng;Jiang Sheng;Shitong Yang
Journal of Radioanalytical and Nuclear Chemistry 2011 Volume 289( Issue 1) pp:
Publication Date(Web):2011 July
DOI:10.1007/s10967-011-1053-7
The effects of pH, ionic strength, competing ions and initial metal concentrations on the uptake behavior and mechanism of radioactive Ni(II) onto MnO2 was investigated using a combination of classical macroscopic methods and the extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The results indicated that the uptake of Ni(II) on MnO2 is obviously dependent on pH but independent of ionic strength, which suggested that the uptake of Ni(II) onto MnO2 is attributed to an inner-sphere surface complex rather than an outer-sphere surface complex. EXAFS analysis shows that the hydrated Ni(II) is adsorbed through six-fold coordination with an average Ni–O interatomic distance of 2.04 ± 0.01 Å. It can be inferred from the EXAFS analysis that the inner-sphere surface complex of Ni(II) onto MnO2 is involved in both edge-sharing and corner-sharing linkages. Both the macroscopic uptake data and the molecular level evidence of Ni(II) surface speciation at the MnO2-water interfaces should be factored into better prediction of the bioavailability and mobility of Ni(II) in soil and water environment.
Co-reporter:Shouwei Zhang ; Haihong Niu ; Yan Lan ; Cheng Cheng ; Jinzhang Xu
The Journal of Physical Chemistry C 2011 Volume 115(Issue 44) pp:22025-22034
Publication Date(Web):October 3, 2011
DOI:10.1021/jp206267x
Carbon nanotubes (CNTs) have attracted much interest because of their special physicochemical properties. Herein, O2 plasma-treated CNTs (denoted as PS-CNTs) are incorporated within a TiO2 matrix (denoted as PS-CNTs/TiO2) as photoanodes in dye-sensitized solar cells (DSSCs). The PS-CNTs/TiO2 composites provide more uniform holes and rough surface over the photoanode and also provide a greater degree of dye adsorption and lower levels of charge recombination, as compared to either chemical modified CNTs/TiO2 (denoted as CM-CNTs/TiO2) or TiO2 alone. The high dispersion of TiO2 on PS-CNTs can improve the electron conduction paths, leads to high electron transfer efficiency, and thereby results in the high performance of the DSSC devices. Herein, the PS-CNTs/TiO2-based working photoanode demonstrates a conversion efficiency of 6.34% in DSSCs, which is ∼75% higher than that of conventional TiO2-based devices.
Co-reporter:Mancheng Liu ; Changlun Chen ; Jun Hu ; Xilin Wu
The Journal of Physical Chemistry C 2011 Volume 115(Issue 51) pp:25234-25240
Publication Date(Web):November 28, 2011
DOI:10.1021/jp208575m
A magnetite/graphene oxide (M/GO) composite was synthesized via a chemical reaction with a magnetite particle size of 10–15 nm and was developed for the removal of heavy metal ions from aqueous solutions. The composite was characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. The sorption of Co(II) on the M/GO composite was carried out under various conditions, that is, contact time, sorbent content, pH, ionic strength, foreign ions, and temperature. The sorption isotherms of Co(II) on the M/GO composite could be described well by the Langmuir model. The thermodynamic parameters (ΔH0, ΔS0, and ΔG0) calculated from the temperature-dependent isotherms indicated that the sorption reaction of Co(II) on the M/GO composite was an endothermic and spontaneous process. M/GO can be separated and recovered by magnetic separation. Results show that the magnetic M/GO composite is a promising sorbent material for the preconcentration and separation of heavy metal ions from aqueous solutions.
Co-reporter:Changlun Chen, Bo Liang, Di Lu, Akihisa Ogino, Xiangke Wang, Masaaki Nagatsu
Carbon 2010 Volume 48(Issue 4) pp:939-948
Publication Date(Web):April 2010
DOI:10.1016/j.carbon.2009.10.033
Multiwall carbon nanotubes (MWCNTs) were modified by using a microwave-excited NH3/Ar surface-wave plasma. Changes in the atom composition and structural properties of the modified MWCNTs were studied as a function of gas flow rate, treatment time, microwave power, and bias voltage by using X-ray photoelectron spectroscopy and Raman spectroscopy. The results suggest that nitrogen-containing groups were introduced on the surfaces of the MWCNTs and that the concentration of primary amino groups was affected by gas flow rate, microwave power, and bias voltage. The contact angle of water on the modified MWCNTs decreased and the hydrophilicity of the modified MWCNTs was improved. The surface morphology and structure of the MWCNTs were not destroyed by the plasma treatment.
Co-reporter:Dadong Shao ; Jun Hu ; Changlun Chen ; Guodong Sheng ; Xuemei Ren
The Journal of Physical Chemistry C 2010 Volume 114(Issue 49) pp:21524-21530
Publication Date(Web):November 11, 2010
DOI:10.1021/jp107492g
Aniline molecules were grafted onto multiwalled carbon nanotubes (MWCNTs) by using a plasma-induced grafting technique. The polyaniline (PANI) grafted MWCNTs (PANI/MWCNTs) were characterized by using ultraviolet−visible spectrophotometry, X-ray photoelectron spectroscopy, Raman spectroscopy, thermogravimetric analysis−differential thermal analysis, and field-emission scanning electron microscopy. The results indicated that the magnetic composite consisting of PANI/MWCNTs was synthesized. The application of PANI/MWCNTs for the removal of aniline and phenol from aqueous solutions was investigated under ambient conditions. The grafted PANI on MWCNTs contributed to the enhancement of the adsorption capacity because of the strong conjugate effect between PANI and organic pollutants. PANI/MWCNTs can be separated and recovered from aqueous solution by magnetic separation. The results show that PANI/MWCNTs are a promising magnetic material for the preconcentration and separation of organic pollutants from large volumes of aqueous solutions in environmental pollution cleanup.
Co-reporter:Dadong Shao, Xuemei Ren, Jun Hu, Yixue Chen, Xiangke Wang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2010 360(1–3) pp: 74-84
Publication Date(Web):
DOI:10.1016/j.colsurfa.2010.02.013
Co-reporter:Jun Hu, Dadong Shao, Changlun Chen, Guodong Sheng, Jiaxing Li, Xiangke Wang and Masaaki Nagatsu
The Journal of Physical Chemistry B 2010 Volume 114(Issue 20) pp:6779-6785
Publication Date(Web):May 3, 2010
DOI:10.1021/jp911424k
The magnetic composite of β-cyclodextrin grafted onto multiwalled carbon nanotubes/iron oxides (denoted as MWCNTs/iron oxides/CD) was synthesized using the plasma-induced grafting technique and was developed for the removal of inorganic and organic pollutants from aqueous solutions. The characteristic results of Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), powder X-ray diffraction (XRD), and thermogravimetric analysis (TGA) showed that β-CD was grafted onto the MWCNTs/iron oxides. The grafted β-CD on the MWCNTs/iron oxides contributed to an enhancement of the adsorption capacity because of the strong abilities of the multiple hydroxyl groups and the inner cores of the hydrophobic cavity in β-CD to form complexes with metal ions and organic pollutants. MWCNTs/iron oxides/CD can be separated and recovered from solution by magnetic separation. The adsorption of Pb(II) on MWCNTs/iron oxides/CD was found to be dependent on pH, and the adsorption of 1-naphthol was found to be independent of pH. The results show that the magnetic composite of MWCNTs/iron oxides/CD is a promising composite material for the preconcentration and separation of inorganic and organic pollutants from aqueous solutions in environmental pollution cleanup.
Co-reporter:Q. H. Fan, X. L. Tan, J. X. Li, X. K. Wang, W. S. Wu and G. Montavon
Environmental Science & Technology 2009 Volume 43(Issue 15) pp:5776-5782
Publication Date(Web):June 23, 2009
DOI:10.1021/es901241f
The effects of pH, ionic strength, and temperature on sorption of Eu(III) on attapulgite were investigated in the presence and absence of fulvic acid (FA) and humic acid (HA). The results indicated that the sorption of Eu(III) on attapulgite was strongly dependent on pH and ionic strength, and independent of temperature. In the presence of FA/HA, Eu(III) sorption was enhanced at pH < 4, decreased at pH range of 4−6, and then increased again at pH > 7. The X-ray photoelectron spectroscopy (XPS) analysis suggested that the sorption of Eu(III) might be expressed as ≡X3Eu0, ≡SwOHEu3+, and ≡SOEu−OOC−/HA in the ternary Eu/HA/attapulgite system. The extended X-ray absorption fine structure (EXAFS) analysis of Eu−HA complexes indicated that the distances of d(Eu−O) decreased from 2.415 to 2.360 Å with increasing pH from 1.76 to 9.50, whereas the coordination number (N) decreased from ∼9.94 to ∼8.56. Different complexation species were also found for the different addition sequences of HA and Eu(III) to attapulgite suspension. The results are important to understand the influence of humic substances on Eu(III) behavior in the natural environment.
Co-reporter:C. L. Chen, X. K. Wang and M. Nagatsu
Environmental Science & Technology 2009 Volume 43(Issue 7) pp:2362
Publication Date(Web):February 18, 2009
DOI:10.1021/es803018a
This paper examines the interaction between Eu(III) and a multiwall carbon nanotube (MWCNT)/iron oxide magnetic composite in the absence and presence of poly(acrylic acid) (PAA). PAA was used as a surrogate for natural organic matter. The effects of pH, initial Eu(III) concentration, and PAA on Eu(III) adsorption on the magnetic composite were investigated using a batch technique. Percentage adsorption of Eu(III) on the magnetic composite increased with increasing pH and decreased with initial Eu(III) concentration. PAA adsorption on the magnetic composite decreased with increasing pH and was not obviously affected by the presence of Eu(III). The presence of PAA resulted in strong enhancement of Eu(III) adsorption below pH 4.5. However, above pH 5, an increase in soluble Eu−PAA complexes resulted in a decrease in Eu(III) adsorption on the magnetic composite. With increasing PAA concentrations, maximum adsorption of Eu(III) decreased and the adsorption “edge” shifted toward a lower pH range. Obvious difference of Eu(III)/PAA addition sequences on Eu(III) adsorption was observed above pH 4. The Freundlich model fitted Eu(III) adsorption isotherms very well in the absence and presence of PAA. These results are important for estimating and optimizing the removal of organic and inorganic pollutants by the magnetic composite.
Co-reporter:Xiaoli Tan, Qiaohui Fan, Xiangke Wang and Bernd Grambow
Environmental Science & Technology 2009 Volume 43(Issue 9) pp:3115
Publication Date(Web):March 24, 2009
DOI:10.1021/es803431c
The sorption of Eu(III) on anatase and rutile was studied as a function of ionic strength, humic acid (HA, 7.5 mg/L), and electrolyte anions over a large range of pH (2−12). The presence of HA significantly affected Eu(III) sorption to anatase and rutile. The sorption of Eu(III) on anatase and rutile was independent of ionic strength. Results of an X-ray photoelectron spectroscopy (XPS) analysis showed that Eu(III) was chemically present within the near-surface of TiO2 due to the formation of ≡SOEu and ≡SOHAEu complexes. An extended X-ray absorption fine structure (EXAFS) technique was applied to characterize the local structural environment of the adsorbed Eu(III), and the results indicated that Eu(III) was bound to about seven or eight O atoms at a distance of about 2.40 Å. The functional groups of surface-bound HA were expected to be involved in the sorption process. The measured Eu−Ti distance confirmed the formation of inner-sphere sorption complexes on a TiO2 surface.
Co-reporter:D.D. Shao, Q.H. Fan, J.X. Li, Z.W. Niu, W.S. Wu, Y.X. Chen, X.K. Wang
Microporous and Mesoporous Materials 2009 Volume 123(1–3) pp:1-9
Publication Date(Web):1 July 2009
DOI:10.1016/j.micromeso.2009.03.043
ZSM-5 zeolite is characterized by XRD, FT-IR and acid–base titration in detail. The results show that the sorption site distribution of ZSM-5 zeolite is affected by ionic strength obviously; the main sorption site are =XNa, =SOH and =SO− in all pH ranges. The sorption experiments of Eu(III) on ZSM-5 zeolite indicate that the sorption is strongly dependent on pH value and on ionic strength (ranged from I = 0.001 to 0.05 mol/L NaClO4) under ambient conditions. The sorption edges of Eu(III) on ZSM-5 zeolite in 0.1 and 0.01 mol/L NaClO4 and the sorption isotherm in 0.01 mol/L NaClO4, respectively, were modeled using a quasi-mechanistic sorption model (1-site protolysis non electrostatic surface complexation and cation exchange (1-SPNE SC/CE) model). The Eu(III) sorption edges in different ionic strengths could be modeled in the pH range 3–10 using cation exchange reactions for Eu3+/Na+ and three surface complexation reactions on the sorption sites by forming =SOEu, =SOEu(OH)+ and =SOEu(OH)2 inner-sphere surface complexes successively. The Eu(III)/ZSM-5 zeolite EXAFS analysis indicates that Eu(III) on ZSM-5 zeolite can be simulated (R = 0.045) by assuming a number of coordination oxygen N = 7.7(5) at d(Eu–O) = 2.31Å (σ = 0.01 Å).
Co-reporter:Dadong Shao, Xiangke Wang, Qiaohui Fan
Microporous and Mesoporous Materials 2009 Volume 117(1–2) pp:243-248
Publication Date(Web):1 January 2009
DOI:10.1016/j.micromeso.2008.06.026
Photocatalytic reduction of Cr(VI) to Cr(III) in aqueous solution containing ZnO or ZSM-5 zeolite under ambient condition was studied by using oxalate as model organic compound in the natural environment. ZSM-5 zeolite was characterized by X-ray diffraction (XRD), and point of zero net proton charge (PZNPC) titration. The effect of illumination time, mass content of catalyst (m/V), Cr(VI) initial concentrations, pH, ionic strength, and oxalate concentrations on the photocatalytic reduction of Cr(VI) was determined. The results indicate that the PZNPC of ZSM-5 zeolite is at pH 3.6 ± 0.1. At C[Cr(VI)(initial)] = 2.00 × 10−4 mol/L, pH 7.5 ± 0.1 and after illumination time of 24 h, the reduction of Cr(VI) were 1.1 × 10−5 mol/L (no ZSM-5 zeolite, 4.0 × 10−3 mol/L oxalate) and 1.0 × 10−5 mol/L (0.4 g/L ZSM-5 zeolite, no oxalate), respectively; whereas the reduction of Cr(VI) achieved 1.0 × 10−4 mol/L in the presence of 0.4 g/L ZSM-5 zeolite and 4.0 × 10−3 mol/L oxalate. The removal of Cr(VI) from solution is dependent on pH value. The results are important for the application of zeolites in the treatment of Cr(VI) polluted solution in the natural environment.
Co-reporter:DaDong Shao;Di Xu;SuoWei Wang;QiaoHui Fang
Science China Chemistry 2009 Volume 52( Issue 3) pp:362-371
Publication Date(Web):2009 March
DOI:10.1007/s11426-008-0145-x
MX-80 bentonite was detected using acid-based titration, XRD and FTIR in detail. The sorption behavior of 63Ni(II) from aqueous solution to MX-80 bentonite was investigated as a function of solid content, ionic strength and pH by using batch technique. The experimental data of 63Ni(II) sorption on MX-80 bentonite was obtained using the diffuse layer model (DLM) with the aid of FITEQL 3.1 program. The results indicated that the sorption of 63Ni(II) on MX-80 bentonite was mainly dominated by surface complexation, and cation exchange also contributed partly to 63Ni(II) sorption at low pH values. The sorption isotherms were simulated by Langmuir and Freundlich models, and the results indicated that Freundlich isotherm model fitted the sorption data better than the Langmuir isotherm model. The results are crucial to evaluate the sorption and migration of radionickel in MX-80 bentonite.
Co-reporter:Changlun Chen, Bo Liang, Akihisa Ogino, Xiangke Wang and Masaaki Nagatsu
The Journal of Physical Chemistry C 2009 Volume 113(Issue 18) pp:7659-7665
Publication Date(Web):April 14, 2009
DOI:10.1021/jp9012015
In this work, oxygen-containing groups were introduced onto multiwall carbon nanotubes (MWCNTs) by using microwave-excited Ar/O2 surface-wave plasma (SWP) treatment. The changes of the atomic contents and structure properties of MWCNTs as a function of gas flow rate, treatment time, and plasma power were analyzed using X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. A mechanism of MWCNT oxidation was proposed, based on XPS analysis, which showed how oxygen-containing groups, such as C−O, C═O, and O−C═O, were generated on the surfaces of MWCNTs. The surface morphology of MWCNTs was observed by field emission scanning electron microscopy (FE-SEM). The results indicated that Ar/O2 plasma treatment greatly enhanced the content of oxygen, modified structure properties, induced more surface defects, and improved the dispersion of MWCNTs in aqueous solution. The integrity of the nanotube patterns was not damaged.
Co-reporter:Guodong Sheng, Suowei Wang, Jun Hu, Yi Lu, Jiaxing Li, Yunhui Dong, Xiangke Wang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2009 Volume 339(1–3) pp:159-166
Publication Date(Web):1 May 2009
DOI:10.1016/j.colsurfa.2009.02.016
To better understand the application of diatomite as an adsorbent for the removal of Pb(II) from heavy metal-contaminated water, in this paper, diatomite was used to adsorb Pb(II) from aqueous solution under various conditions. The results demonstrated that the adsorption of Pb(II) was strongly dependent on ionic strength at pH < 7.0, outer-sphere surface complexation or ion exchange may be the main adsorption mechanism of Pb(II) on diatomite at low pH values. No drastic difference of Pb(II) adsorption was observed at pH > 7.0, and the adsorption at high pH values was mainly dominated via inner-sphere surface complexation. The presence of HA/FA showed great influence on Pb(II) adsorption on diatomite. The adsorption of Pb(II) on diatomite was dependent on foreign ions (herein K+, Na+, ClO4−, NO3− and Cl−) in solution at pH < 8.0, and was independent of foreign ions at pH > 8.0. The thermodynamic parameters (i.e., ΔH°, ΔS°, ΔG°) were evaluated from the temperature dependent adsorption isotherms. The results indicated that the adsorption process of Pb(II) on diatomite was spontaneous and endothermic in nature.
Co-reporter:Jun Hu;Di Xu;Lei Chen
Journal of Radioanalytical and Nuclear Chemistry 2009 Volume 279( Issue 3) pp:701-708
Publication Date(Web):2009 March
DOI:10.1007/s10967-007-7252-6
MX-80 bentonite is considered as one of the best backfill materials for high-level radioactive nuclear waste. Herein, the bentonite is characterized by using XRD and FTIR techniques. Sorption of radionickel to MX-80 bentonite in the presence/absence of humic acid (HA) or fulvic acid (FA) as a function of pH is investigated. The results indicate that the presence of HA or FA decreases the sorption of Ni2+ obviously. The different experimental processes do not affect the sorption of nickel to FA/HA bound bentonite. The sorption of Ni2+ on FA/HA-bound bentonite decreases with the increasing FA/HA content in the systems. The mechanism of nickel sorption is also discussed in detail.
Co-reporter:Dadong Shao, Zhongqing Jiang, Xiangke Wang, Jiaxing Li and Yuedong Meng
The Journal of Physical Chemistry B 2009 Volume 113(Issue 4) pp:860-864
Publication Date(Web):January 7, 2009
DOI:10.1021/jp8091094
Carboxymethyl cellulose (CMC) is grafted on multiwalled carbon nanotubes (MWCNT) by using plasma techniques. The CMC grafted MWCNT (MWCNT-g-CMC) is characterized by using Fourier transform infrared spectra (FT-IR), Raman spectra, powder X-ray diffraction (XRD), thermogravimetric analysis (TGA)−differential thermal analysis (DTA), scanning electron microscopy (SEM), and N2-BET methods in detail. The application of MWCNT-g-CMC in the removal of UO22+ from aqueous solution is investigated. MWCNT-g-CMC has much higher sorption ability in the removal of UO22+ than raw MWCNT. The MWCNT-g-CMC is a suitable material in the preconcentration and solidification of heavy metal ions from large volume of aqueous solutions.
Co-reporter:Xiaoli Tan, Ming Fang, Changlun Chen, Shaoming Yu, Xiangke Wang
Carbon 2008 Volume 46(Issue 13) pp:1741-1750
Publication Date(Web):November 2008
DOI:10.1016/j.carbon.2008.07.023
Batch experiments were conducted to elucidate the adsorption of a widely used anionic surfactant (sodium dodecylbenzene sulfonate (SDBS)) and nickel on multiwalled carbon nanotubes (MWCNTs). Counterion effect on the removal of SDBS and nickel by using MWCNTs was also studied. The microscopic changes of MWCNTs before and after nickel and SDBS adsorption were characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). X-ray photoelectron spectroscopy (XPS) was performed to study the adsorption mechanism of nickel at a molecular level. The spectroscopic analysis indicated that the adsorption mechanism was mainly attributed to chemical interaction between nickel and the surface functional groups of MWCNTs and surface adsorbed SDBS. The adsorbed SDBS on MWCNTs could lead to the modification of the MWCNT surfaces and partial complexation of nickel with SDBS adsorbed on MWCNTs. MWCNTs are efficient material in the removal of SDBS and nickel from large volume of wastewater.
Co-reporter:X. L. Tan, X. K. Wang, H. Geckeis and TH. Rabung
Environmental Science & Technology 2008 Volume 42(Issue 17) pp:6532-6537
Publication Date(Web):August 1, 2008
DOI:10.1021/es8007062
To identify the effect of humic acid (HA) and fulvic acid (FA) on the sorption mechanism of Eu(III) on organic−inorganic colloids in the environment at a molecular level, surface adsorbed/complexed Eu(III) on hydrous alumina, HA-, and FA-hydrous alumina hybrids were characterized by using X-ray photoelectron spectroscopy (XPS) and time-resolved laser fluorescence spectroscopy (TRLFS). The experiments were performed in 0.1 mol/L KNO3 or 0.1 mol/L NaClO4 under ambient conditions. The pH values were varied between 2 and 11 at a fixed Eu(III) concentration of 6.0 × 10−7 mol/L and 4.3 × 10−5 mol/L. The different Eu(III)/FA(HA)/hydrous alumina complexes were characterized by their fluorescence emission spectra ((5D0→7F1)/(5D0→7F2)) and binding energy of Eu(III). Inner-sphere surface complexation may contribute mainly to Eu(III) sorption on hydrous alumina, and a ternary surface complex is formed at the HA/FA-hydrous alumina hybrid surfaces. The sorption and species of Eu(III) in ternary Eu-HA/FA-hydrous alumina systems are not dominated by either HA/FA or hydrous alumina, but are dominated by both HA/FA and hydrous alumina. The results are important for understanding the sorption mechanisms and the nature of surface adsorbed Eu(III) species and trivalent chemical homologues of Eu(III) in the natural environment.
Co-reporter:Changlun Chen, Jun Hu, Di Xu, Xiaoli Tan, Yuedong Meng, Xiangke Wang
Journal of Colloid and Interface Science 2008 Volume 323(Issue 1) pp:33-41
Publication Date(Web):1 July 2008
DOI:10.1016/j.jcis.2008.04.046
Co-reporter:Q.H. Fan, D.D. Shao, J. Hu, W.S. Wu, X.K. Wang
Surface Science 2008 Volume 602(Issue 3) pp:778-785
Publication Date(Web):1 February 2008
DOI:10.1016/j.susc.2007.12.007
Attapulgite was investigated to remove Ni2+ from aqueous solutions because of its strong sorption ability. Herein, the sample of attapulgite was modified with ammonium citrate tribasic (ACT) and used as an adsorbent to remove Ni2+ from aqueous solutions. XRD and FTIR analysis indicated that ACT was successfully grafted on attapulgite surfaces. The results indicated that ACT–attapulgite was better than bare attapulgite in the removal of Ni2+ from aqueous solutions. Sorption of Ni2+ on ACT–attapulgite was mainly dominated by ion exchange or outer-sphere complexes at low pH values, and by inner-sphere complexes or surface precipitation at high pH values. The thermodynamic data indicated that the sorption of Ni2+ to ACT–attapulgite hybrids was an endothermic process and was enhanced with increasing temperature. ACT–attapulgite is a suitable material for the preconcentration of Ni2+ from large volume of solutions and can be used in wastewater treatment because of its negative surface charge and large surface areas.
Co-reporter:X.L. Tan, P.P. Chang, Q.H. Fan, X. Zhou, S.M. Yu, W.S. Wu, X.K. Wang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2008 Volume 328(1–3) pp:8-14
Publication Date(Web):1 October 2008
DOI:10.1016/j.colsurfa.2008.06.022
Sorption of Pb(II) from aqueous solution to Na-rectorite was studied under ambient conditions using batch technique. The effect of pH, ionic strength, humic acid and fulvic acid on the sorption of Pb(II) to Na-rectorite was also investigated. The results indicated that sorption of Pb(II) was strongly dependent on pH values. The sorption was dependent on ionic strength at low pH values, but independent of ionic strength at high pH values. Outer-sphere complexes were formed on the surface of rectorite at low pH values, whereas inner-sphere complexes were formed at high pH values. The presence of humic acid and/or fulvic acid enhanced the sorption of Pb(II) at low pH values, but decreased the sorption at high pH values. The thermodynamic values of enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) were calculated from the temperature dependent sorption isotherms. The results indicated that the sorption was endothermic and spontaneous process and the sorption increased with increasing temperature.
Co-reporter:Pengpeng Chang, Xiangke Wang, Shaoming Yu, Wangsuo Wu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2007 Volume 302(1–3) pp:75-81
Publication Date(Web):20 July 2007
DOI:10.1016/j.colsurfa.2007.01.040
Removal of Ni(II) from aqueous solutions by sorption onto Na-rectorite was investigated under ambient conditions. Experiments were carried out as a function of mass content, pH, ionic strength and temperature. The results indicated that the sorption of Ni(II) was strongly dependent on pH value and ionic strength. Sorption of Ni(II) increased with increasing pH and decreasing ionic strength. The sorption of Ni(II) on Na-rectorite was mainly dominated by cation exchange at acidic conditions, whereas surface complexation was the main sorption mechanism at neutral to alkaline pH values. The effect of temperature on Ni(II) sorption on Na-rectorite was negligible at low pH (∼pH < 6), whereas the effect of temperature was obvious at pH > 6. The thermodynamic parameters (ΔH, ΔS, and ΔG) for Ni(II) sorption onto Na-rectorite were calculated from the temperature dependence, and the results suggested that the sorption reaction was endothermic.
Co-reporter:Changlun Chen, Xiangke Wang, Hui Jiang, Wenping Hu
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2007 Volume 302(1–3) pp:121-125
Publication Date(Web):20 July 2007
DOI:10.1016/j.colsurfa.2007.02.014
Humic substances (HSs) can be easily adsorbed on natural solid surface and thereby affect the physicochemical behavior of metal ions in the natural environment. The influence of HSs is mainly attributed to the macromolecular structures and shapes of solution soluble and surface adsorbed HSs. Herein, to our knowledge, we firstly use both AFM and SEM to image and to compare the macromolecular structures of humic acid on the basal-plane surface of mica and silicon. Under our experimental conditions, spherical colloids are formed at low pH and high salt concentrations, while network or linear structures are formed at high pH and low salt concentrations. The shapes of HA are heterogeneous under different natural environmental conditions. The knowledge of macromolecular structures and shapes of HA in the natural environment is significant for the evaluation of metal ions’ behavior in HA–metal ion–mineral ternary systems.
Co-reporter:Changlun Chen, Xueliang Li, Donglin Zhao, Xiaoli Tan, Xiangke Wang
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2007 Volume 302(1–3) pp:449-454
Publication Date(Web):20 July 2007
DOI:10.1016/j.colsurfa.2007.03.007
The adsorption kinetics of Th(IV) on oxidized multi-wall carbon nanotubes (MWCNTs) was investigated at initial Th(IV) concentrations 32.32 and 64.64 μmol/L. The kinetic process was described by a pseudo-second-order rate model very well. The adsorption thermodynamics of Th(IV) on oxidized MWCNTs was carried out at 293 ± 2, 303 ± 2, and 323 ± 2 K, respectively, and the thermodynamic parameters, such as equilibrium constant (K0), standard free energy changes (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°), were obtained. The Langmuir model described the data better than the Freundlich isotherm model. Desorption studies indicated that Th(IV) adsorption was reversible and Th(IV) ions could be desorbed from the surface of carbon nanotubes by adjusting the pH values. Oxidized MWCNTs may be a promising candidate for the preconcentration and solidification of Th(IV), or its analogue actinides from large volumes.
Co-reporter:Xiaoli Tan, Xiangke Wang, Ming Fang, Changlun Chen
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2007 Volume 296(1–3) pp:109-116
Publication Date(Web):15 March 2007
DOI:10.1016/j.colsurfa.2006.09.032
The removal of Th(IV) from aqueous solution by using nanoparticles of anatase is studied under ambient conditions. The sorption of Th(IV) on TiO2 increases markedly at pH 1.5–4 and then maintains level with increasing pH values. The presence of HA/FA enhances the sorption of Th(IV) on TiO2 at low pH values. The Langmuir, Freundlich, Redlich-Peterson and Dubini-Radushkevich models are used to simulate the sorption isotherms, respectively. The results suggest that the sorption of Th(IV) on TiO2 occurs mainly by surface complexation. The adsorbed Th(IV) is very difficult to be desorbed from the solid surface. The results of XRD and Raman analysis indicate that the matrix of TiO2 does not undergo any structural change after the sorption of Th(IV) ions. The Ti-O-H stretching occurred in the IR spectral region of 1000–1300 cm−1 for the hydrated TiO2 samples is responsible for sorption of metal binding, and provides indirect evidence for the surface complexation mechanism.
Co-reporter:Xiangke Wang, Xiang Zhou, Jinzhou Du, Wenping Hu, Changlun Chen, Yixue Chen
Surface Science 2006 Volume 600(Issue 2) pp:478-483
Publication Date(Web):15 January 2006
DOI:10.1016/j.susc.2005.10.045
The association of organic–inorganic colloid-borne trace elements was investigated. Radionuclide 152+154Eu(III) was chosen as a representative and chemical homologue for trivalent lanthanide and actinide ions present in radioactive nuclear waste. Effect of pH and contact time of organic–inorganic/Eu(III) on the kinetic dissociation of Eu(III) from HA–Al2O3 colloids was studied. The kinetic desorption behavior of sorbed 152+154Eu(III) from humic acid–γ-Al2O3 colloids was studied at pH values of 4.5 ± 0.2, 5.3 ± 0.2 and 6.5 ± 0.2, respectively, by the addition of the chelating resin. The experimental results suggest that the fractions of irreversible sorption of radionuclide 152+154Eu(III) to HA–Al2O3 colloids increase with increasing pH values, and are independent of aging time. At least two different species, “weak” and “strong” dissociation fractions, are required to simulate the kinetic desorption of 152+154Eu(III) from HA–Al2O3 colloids. The species of Eu(III) sorbed on HA–Al2O3 colloids move from “weak” sites to “strong” sites with increasing aging time, whereas the fractions of irreversible sorption are independent of aging time. The results are important for the evaluation of radionuclides’ behavior in the environment.
Co-reporter:Changlun Chen, Donglin Zhao, Xiangke Wang
Materials Chemistry and Physics 2006 Volume 97(Issue 1) pp:156-161
Publication Date(Web):10 May 2006
DOI:10.1016/j.matchemphys.2005.08.001
The influence of the addition of amorphous tantalum oxide (Ta2O5) on electrochemical capacitor performance of molybdenum nitride(Mo2N) was investigated.γ-Mo2N/Ta2O5 composite electrode materials have been synthesized using temperature-programmed reduction (TPR) the mixture of MoO3 and amorphous Ta2O5 with ammonia gas. The materials were physically and chemically characterized by X-ray diffraction (XRD), scanning electron microcopy (SEM), and cyclic voltammetry (CV). Typical CV characterization of the materials indicated fast kinetics for charge–discharge process as well as good kinetic reversibility. The addition of amorphous tantalum oxide not only increased the electrochemical capacitance value of the materials, but also widened its potential stability window.
Co-reporter:Xiangke Wang, Xiaoli Tan, Changlun Chen, Lei Chen
Journal of Nuclear Materials 2005 Volume 345(2–3) pp:184-191
Publication Date(Web):15 October 2005
DOI:10.1016/j.jnucmat.2005.05.015
The ‘in-diffusion’ method was used to study the diffusion behavior of radionuclide 137Cs in compacted bentonite using a capillary. The results (distribution coefficient, Kd, apparent and effective diffusion coefficients, Da and De) derived from the capillary method are in good agreement with the literature data, and fit the Fick’s second law very well. The experiments were carried out at 3.3 × 10−3 and 3.3 × 10−5mol/l cesium, pH 3–12, ionic strength 0.1 M NaClO4, and at room temperature. The results suggest that the diffusion of cesium in compacted bentonite is dependent on solution concentrations and pH values. In agreement with the literatures, the Kd values derived from the capillary experiments are in most cases lower than those derived from batch experiments: the Kd values are about one-half to one-third the values of those from batch experiments. The interlaminary space plays a very important role to the sorption, diffusion and transport of Cs+ in compacted bentonite. The effective diffusion coefficient is higher than that of other nuclides in compacted bentonite, and the diffusion of cesium in compacted bentonite may be dominated by the surface diffusion.
Co-reporter:Changlun Chen, Jianbo He, Di Xu, Xiaoli Tan, Xiang Zhou, Xiangke Wang
Sensors and Actuators B: Chemical 2005 Volume 107(Issue 2) pp:866-871
Publication Date(Web):29 June 2005
DOI:10.1016/j.snb.2004.12.037
A novel electrochemical sensor based on nano-Au colloid modified on Pt disk microelectrode was developed for determination of carbon monoxide (CO). The catalytic activation of nano-Au colloid modified on Pt disk microelectrode as substrate was investigated in different supporting electrolyte solutions by cyclic voltammetry and constant potential transient method. The result shows that nano-Au colloid modified on Pt disk microelectrode exhibited strong catalytic effect toward the electrochemical oxidation of CO in 0.5 mol l−1 HClO4. As compared with the bare Pt disk microelectrode, the nano-Au colloid modified on Pt disk microelectrode can greatly decrease the overpotential and obviously increase the current of CO oxidation. The current–time curve recorded under conditions of constant potential and various CO concentrations suggests that current response depends linearly on CO concentration. A linear equation I (μA) = 0.00917 (μg ml−1) + 0.151 with a correlation coefficient of 0.9938 is obtained over the concentration range 0.756 μg ml−1 at potential +800 mV relative to Ag/AgCl reference electrode. The detection limit is 0.65 μg ml−1 and the relative standard deviation is 5.3% (n = 5) at room temperature.
Co-reporter:Shitong Yang, Jiaxing Li, Yi Lu, Yixue Chen, Xiangke Wang
Applied Radiation and Isotopes (September 2009) Volume 67(Issue 9) pp:
Publication Date(Web):1 September 2009
DOI:10.1016/j.apradiso.2009.03.118
Bentonite has been widely studied in nuclear waste management because of its special physicochemical properties. In this work, the sorption of Ni(II) from aqueous solution onto GMZ bentonite as a function of contact time, pH, ionic strength, foreign ions, humic acid (HA) and temperature was investigated under ambient conditions. The results indicated that the pseudo-second-order rate equation simulated the kinetic sorption process well. The sorption of Ni(II) on GMZ bentonite was strongly dependent on pH and on ionic strength. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation and ion exchange with Na+/H+ on GMZ bentonite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. A positive effect of HA on Ni(II) sorption was found at pH<8, whereas a negative effect was observed at pH>8. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of Ni(II) at three different temperatures: 303.15, 318.15 and 333.15 K. The thermodynamic parameters (ΔH0, ΔS0 and ΔG0) of Ni(II) sorption on GMZ bentonite at the three different temperatures were calculated from the temperature-dependent sorption isotherms. The results indicated that the sorption process of Ni(II) on GMZ bentonite was endothermic and spontaneous. Experimental results indicate that GMZ bentonite is a suitable sorbent for pre-concentration and solidification of Ni(II) from large volume solutions.
Co-reporter:Xiaoli Tan, Changlun Chen, Shaoming Yu, Xiangke Wang
Applied Geochemistry (September 2008) Volume 23(Issue 9) pp:
Publication Date(Web):1 September 2008
DOI:10.1016/j.apgeochem.2008.07.008
Sorption of Ni2+ on Na-rectorite as a function of contact time, temperature, pH and fulvic acid (FA)/humic acid (HA) was studied under ambient conditions. A pseudo-second-order rate equation was used to simulate the kinetic sorption. The removal of Ni2+ increased with increasing pH. The presence of FA/HA enhanced the sorption of Ni2+ at low pH values, whereas no drastic effect of FA/HA on Ni2+ uptake to rectorite was found at high pH values. The diffuse layer model (DLM) fitted the experimental data of Ni2+ sorption in the absence and presence of FA/HA very well with the aid of FITEQL 3.2. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were used to simulate the sorption isotherms of Ni2+ at different temperatures. The thermodynamic data (ΔH0, ΔS0, ΔG0) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of Ni2+ on rectorite was spontaneous and endothermic. The sorption and species of Ni2+ on rectorite in the presence and absence of FA/HA was also investigated and characterized by XPS. The spectroscopic analysis indicated no drastic structural changes of Na-rectorite and the sorption of Ni2+ mainly occurred on the surface and at the edge position of Na-rectorite.
Co-reporter:D. Xu, X.L. Tan, C.L. Chen, X.K. Wang
Applied Clay Science (September 2008) Volume 41(Issues 1–2) pp:37-46
Publication Date(Web):September 2008
DOI:10.1016/j.clay.2007.09.004
Co-reporter:D.L. Zhao, S.J. Feng, C.L. Chen, S.H. Chen, D. Xu, X.K. Wang
Applied Clay Science (September 2008) Volume 41(Issues 1–2) pp:17-23
Publication Date(Web):September 2008
DOI:10.1016/j.clay.2007.09.012
Co-reporter:Guodong Sheng, Jun Hu, Xiangke Wang
Applied Radiation and Isotopes (October 2008) Volume 66(Issue 10) pp:1313-1320
Publication Date(Web):October 2008
DOI:10.1016/j.apradiso.2008.03.005
Co-reporter:Di Xu, Xiang Zhou, Xiangke Wang
Applied Clay Science (May 2008) Volume 39(Issues 3–4) pp:133-141
Publication Date(Web):May 2008
DOI:10.1016/j.clay.2007.05.006
Co-reporter:Ling Yin, Pengyi Wang, Tao Wen, Shujun Yu, Xiangxue Wang, Tasawar Hayat, Ahmed Alsaedi, Xiangke Wang
Environmental Pollution (July 2017) Volume 226() pp:125-134
Publication Date(Web):1 July 2017
DOI:10.1016/j.envpol.2017.03.078
•TNWs was fabricated at relative low temperature and exhibited excellent sorption capacity.•Ca2+, PO43-, SO42- and CO32- influenced the sorption performance of U(VI) onto TNWs to varying degrees.•TNWs performed a high cycling performance for U(VI) sorption and could achieve equilibrium rapidly.Uranium(VI) has become one of the most potential contaminants due to its productive and irreversibility impact on the surrounding environment. Titanate nanowires (TNWs) have attracted significant attention because of its high ion exchange ability and facile synthesis. Herein the TNWs were synthesized, and the morphology and structure of TNWs were investigated by Fourier transformed infrared spectroscopy, scanning electron microscope, transmission electron microscope, X-ray diffraction and X-ray photoelectron spectroscopy in detail. The application of TNWs in U(VI) removal was studied under various environmental conditions using batch technique, and the results indicated that the sorption of U(VI) on TNWs was strongly affected by pH and weakly affected by ionic strength. The presence of PO43- and CO32- could overwhelmingly influence U(VI) interaction with TNWs, which was mainly attributed to the formation of anionic and electro-neutral complexes. From the Langmuir model simulation, the maximum sorption capacities were calculated to be 358, 384, and 410 mg g−1 at the temperatures of 298 K, 313 K and 328 K, respectively. The thermodynamic results revealed that the interaction process was spontaneous and endothermic. The extraordinary ion exchange capacity and facile synthesis under mild conditions made TNWs promising materials for the potential application in the efficient elimination of U(VI) or other lanthanides and actinides from aqueous solutions in the environmental radioactive pollution cleanup.Download high-res image (346KB)Download full-size image
Co-reporter:S.M. Yu, C.L. Chen, P.P. Chang, T.T. Wang, S.S. Lu, X.K. Wang
Applied Clay Science (February 2008) Volume 38(Issues 3–4) pp:219-226
Publication Date(Web):February 2008
DOI:10.1016/j.clay.2007.03.008
Co-reporter:Changlun Chen, Xiangke Wang
Applied Radiation and Isotopes (February 2007) Volume 65(Issue 2) pp:155-163
Publication Date(Web):February 2007
DOI:10.1016/j.apradiso.2006.07.003
Co-reporter:C.L. Chen, X.K. Wang
Applied Geochemistry (February 2007) Volume 22(Issue 2) pp:
Publication Date(Web):1 February 2007
DOI:10.1016/j.apgeochem.2006.11.010
The sorption of Th(IV) onto γ-Al2O3 in the absence and presence of soil humic acid (HA)/fulvic acid (FA) was studied by batch technique. The influence of pH from 2 to 12, ionic strength from 0.01 M to 0.1 M KNO3, soil HA/FA concentrations from 2.5 mg/L to 17.5 mg/L, and foreign cations (Li+, Na+, K+) and anions (NO3-, Cl−) on the sorption of Th(IV) onto γ-Al2O3 was also tested. The sorption isotherms of Th(IV) were determined at pH 3.50 (±0.02) and analyzed with the linear, Freundlich, and Langmuir sorption models, respectively. The results demonstrated that the sorption of Th(IV) onto γ-Al2O3 increases steeply with increasing pH from 2 to 4. HA/FA was shown to enhance Th(IV) sorption at low pH, but to reduce Th(IV) sorption at high pH. It was assumed that the significantly positive influence of HA/FA on Th(IV) sorption onto γ-Al2O3 at pH 2–4 is attributable to the strong surface binding of HA/FA on γ-Al2O3 and subsequently to the formation of ternary surface complexes such as SO–O–HA–Th or SO–O–FA–Th. The results also demonstrated that the sorption is strongly dependent on the concentration of HA/FA, and slightly dependent on ionic strength. The sorption of Th(IV) onto γ-Al2O3 was also dependent on foreign ions in solution under the experimental conditions.
Co-reporter:Di Xu, Changlun Chen, Xiaoli Tan, Jun Hu, Xiangke Wang
Applied Geochemistry (December 2007) Volume 22(Issue 12) pp:
Publication Date(Web):1 December 2007
DOI:10.1016/j.apgeochem.2007.08.003
The sorption of Th(IV) on Na-rectorite as a function of pH, ionic strength, temperature, soil humic acid (HA) and foreign ions was studied by using a batch technique under ambient conditions. The results indicated that the sorption of Th(IV) on Na-rectorite is strongly depended on pH, ionic strength and temperature. The presence of HA enhanced Th(IV) sorption at low pH and had no obvious effect on Th(IV) sorption at high pH. The sorption of Th(IV) decreased with increasing temperature, indicating that the sorption process of Th(IV) on rectorite was exothermic. Sodium-rectorite and HA were characterized by acid–base titration to obtain the pKa, and the constant capacitance model (CCM) modeled the sorption data very well with the aid of FITEQL 3.2. HA/Th(IV) addition sequences affected Th(IV) sorption in the ternary systems. The sorption of Th(IV) on Na-rectorite may be dominated by surface complexation, while cation exchange also contributes partly to the sorption.
Co-reporter:Xiaoli Tan, Xiangke Wang, Changlun Chen, Aihua Sun
Applied Radiation and Isotopes (April 2007) Volume 65(Issue 4) pp:375-381
Publication Date(Web):April 2007
DOI:10.1016/j.apradiso.2006.10.014
Co-reporter:Shujun Yu, Xiangxue Wang, Zhongshan Chen, Jian Wang, Suhua Wang, Tasawar Hayat, Xiangke Wang
Journal of Hazardous Materials (5 January 2017) Volume 321() pp:111-120
Publication Date(Web):5 January 2017
DOI:10.1016/j.jhazmat.2016.09.009
•TAL and PAL are prepared via one-step hydrothermal method.•TAL and PAL present high removal capacity for aniline from aqueous solutions.•The interaction mechanisms are hydrogen bond and electrostatic interaction.Aniline is toxic and hard to be degraded, and thereby causes the environmental pollution seriously. Herein, a practical and green hydrothermal method was applied to fabricate terephthalic acid and pyromellitic acid intercalated layered double hydroxides (LDH) (named as TAL and PAL) for aniline efficient removal. The sorption of aniline on LDH-based materials were investigated at different experimental conditions, and the results indicated that aniline sorption on LDH, TAL and PAL were strongly dependent on pH and independent of ionic strength. The maximum sorption capacities of aniline on TAL and PAL at pH 5.0 and 293 K were 90.4 and 130.0 mg/g, respectively, which were significantly higher than that of aniline on LDH (52.6 mg/g). Based on the BET, FTIR and XPS analysis, the higher sorption capacities of TAL and PAL were mainly due to high surface area and basal spacing as well as the abundant functional groups (e.g. –COO−). The interactions of aniline with TAL and PAL were mainly dominated by hydrogen bonds and electrostatic interactions. Such a facile synthesis method, efficient removal performance and superior reusability indicated that the aromatic acid modified LDH materials had potential application for efficient treatment of organic pollutants in environmental pollution cleanup.Higher affinity of aniline for PAL and TAL than LDHDownload high-res image (160KB)Download full-size image
Co-reporter:Shitong Yang, Guodong Sheng, Xiaoli Tan, Jun Hu, Jinzhou Du, Gilles Montavon, Xiangke Wang
Geochimica et Cosmochimica Acta (1 November 2011) Volume 75(Issue 21) pp:6520-6534
Publication Date(Web):1 November 2011
DOI:10.1016/j.gca.2011.08.024
The uptake mechanisms of Ni(II) on mordenite were investigated by macroscopic experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy. The results demonstrated that Ni(II) could be retained via different mechanisms, depending on pH, ionic strength, temperature, etc. At low pH, the uptake of Ni(II) is primarily dominated by cation exchange and/or outer-sphere surface complexation. The interatomic distances of Ni–O (∼2.05 Å) and the coordination number (∼6.0) are similar to those of Ni(II)(aq) reference sample, suggesting that Ni(II) is present in an [Ni(H2O)6]2+ octahedral environment at low pH. With increasing pH, the uptake of Ni(II) on mordenite tends to form inner-sphere surface complexes and precipitation/co-precipitation at high pH. The uptake of Ni(II) on mordenite becomes more favorable with increasing temperature, and the EXAFS spectra analysis show a trend from outer-sphere surface complexation at low temperature to inner-sphere surface complexation at high temperature. The addition of HA/FA increases Ni(II) uptake at low pH and decreases Ni(II) uptake at high pH. Enhanced Ni(II) uptake is attributed to the formation of “ligand-bridging” ternary surface complexes that are adsorbed on mordenite surface, while reduction is attributed to the formation of soluble Ni(II)–HA/FA complexes in solution that compete with uptake processes. The findings presented in this study are important toward a molecular-level description of Ni(II) uptake processes at the water–mineral interface.
Co-reporter:Wencheng Song, Xiangxue Wang, Tao Wen, Shujun Yu, Yidong Zou, Yubing Sun, Tasawar Hayat, and Xiangke Wang
ACS Omega Volume 1(Issue 5) pp:899-906
Publication Date(Web):November 11, 2016
DOI:10.1021/acsomega.6b00260
Arsenic (As) contamination in aqueous solutions has become an increasing public concern due to the immense harm to human health. Herein, bioaccumulation of arsenate (As(V)) by Rhizopus oryzae in aqueous systems was investigated under different environmental conditions, such as different pH’s, ionic strengths, mycelia dosages, mycelia growths, and temperatures. The results showed that As(V) could be bioaccumulated efficiently by R. oryzae, and the maximum bioaccumulation capacity of As(V) in R. oryzae was 52.4 mg/g at T = 299 K, which was much higher than that for other biomaterials under similar conditions. R. oryzae generated a higher content of thiol compounds under As(V) stress to immobilize As(V) from aqueous solutions. X-ray absorption near-edge spectroscopy analysis indicated that As(V) was partly reduced to As(III) with increasing contact time, which increased As(V) bioaccumulation in mycelia. In addition, extended X-ray absorption fine structure analysis showed that the As–S complex played an important role in As(V) immobilization by mycelia. This study provided an in-depth investigation of intracellular As speciation and coordination in R. oryzae on the molecular scale, which was crucial to understand the interaction mechanisms of As(V) with fungi during environmental cleanup.Topics: Fungi; Ionic strength; Organometallic chemistry; Toxicology; Waste management; X-ray spectroscopy;
Co-reporter:
Analytical Methods (2009-Present) 2015 - vol. 7(Issue 13) pp:NaN5648-5648
Publication Date(Web):2015/06/01
DOI:10.1039/C5AY00928F
Catechin is a polyphenol antioxidant which can be found in great abundance in the leaves of tea plants. In this study, catechin was electrodeposited on an activated carbon paste electrode for electrocatalytic determination of two neurotransmitters, dopamine (DA) and serotonin (ST). The voltammetric conditions for electrode preparation in catechin solution were optimized as follows: phosphate buffer at pH 7.4, catechin concentration of 1.0 mM, potential window of 0.2–1.6 V (vs. Ag/AgCl/KClsat), scan rate of 50 mV s−1 and cycle number of 15. The prepared electrode showed high electrocatalytic activity for the oxidation of both DA and ST. The highest electrocatalytic activity for DA oxidation was observed in the physiological pH (7.4) buffer solution. Amperometric detection under stirring achieved a current sensitivity of 10.29 nA nM−1 cm−2 to DA in the linear concentration range of 10–780 nM, and 4.81 nA nM−1 cm−2 to ST in the range of 30–2340 nM, with the lowest detection limits of 0.5 and 3 nM for DA and ST, respectively. The resulting biosensor was successfully used to quantify DA and ST in commercial samples with high sensitivity and good stability. In addition, the fact that the oxidized catechin can effectively promote the electron transfer processes of DA and ST may help in understanding the role of catechin in nervous excitement.
Co-reporter:Qi Wang, Xiao Zuo and Xiangke Wang
Dalton Transactions 2014 - vol. 43(Issue 34) pp:NaN12966-12966
Publication Date(Web):2014/06/19
DOI:10.1039/C4DT01114G
A facile in situ plasma synthesis of graphene-based Pt nanoparticles is presented. For comparison, chemical reduction was also used. Ar plasma was capable of reducing Pt precursors into well dispersed Pt nanoparticles on graphene. The electrocatalytic activities of the two as-prepared catalysts were tested, and then they were used as anodes for methanol electro-oxidation in a DMFC. The catalyst prepared by the plasma approach showed higher catalytic activity for methanol electro-oxidation. The plasma technique is also suitable for the fabrication of other functional carbon based metal composites for their applications in multidisciplinary areas.
Co-reporter:Yubing Sun, Changlun Chen, Xiaoli Tan, Dadong Shao, Jiaxing Li, Guixia Zhao, Shubin Yang, Qi Wang and Xiangke Wang
Dalton Transactions 2012 - vol. 41(Issue 43) pp:NaN13394-13394
Publication Date(Web):2012/09/03
DOI:10.1039/C2DT31510F
Mesoporous Al2O3 was intercalated into an expanded graphite (EG) interlayer to prepare mesoporous Al2O3/EG composites. The basal spacing of mesoporous Al2O3/EG composites was enlarged as compared to raw graphite from the X-ray diffraction analysis. The massive surface functional groups and wedge-shaped pores were observed in terms of potentiometric acid–base titration analysis and scanning electron microscope, respectively. The pH-dependent adsorption of Eu(III) on mesoporous Al2O3/EG composites was evidently independent of ionic strength. The maximum adsorption capacity of Eu(III) on mesoporous Al2O3/EG composites at pH 6.0 and T = 293 K was calculated to be 5.14 mg g−1. Desorption kinetics and cyclic operation results showed that mesoporous Al2O3/EG composites presented high hydrothermal stability in aqueous solution. The thermodynamic parameters suggested that Eu(III) adsorption on mesoporous Al2O3/EG composites is an endothermic and a spontaneous process. The decrease of Eu–O bond distance with the increasing pH demonstrated that the adsorption mechanism between Eu(III) and mesoporous Al2O3/EG composites would shift from outer-sphere surface complexation to inner-sphere surface complexation in terms of extended X-ray absorption fine structure spectroscopy analysis.
Co-reporter:He Chen, Xiangxue Wang, Jiaxing Li and Xiangke Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 11) pp:NaN6081-6081
Publication Date(Web):2015/01/30
DOI:10.1039/C5TA00299K
Well-structured cotton derived porous carbon (CDPC) and cotton derived porous carbon oxide (CDPCO) were fabricated via a facile and economic alkaline etching method and were used as adsorbents for waste water cleanup. As a carbon source, natural cotton waste was dehydrated with sodium hydroxide at low temperatures and further etched at high temperatures in a thermal treatment process. The synthesized CDPCO exhibited an excellent adsorption performance of organic pollutants and heavy metal ions such as methylene blue, 1-naphthylamine, Cd(II) and Co(II) in aqueous solutions. The adsorption mechanism was investigated via FT-IR analysis and controlled experiments, and it was concluded that the organic pollutant removal was affected by the molecular size of the organic pollutants and the ionic interactions between the pollutants and adsorbents. The adsorption of heavy metal ions was dependent on the interactions between the heavy metal ions and functional groups on the adsorbents’ surfaces. The adsorption process fitted the Langmuir model better than the Freundlich model. Our results suggested that CDPC could be a favorable adsorbent for the removal of organic pollutants and heavy metal ions from aqueous solutions.
Co-reporter:Guixia Zhao, Tao Wen, Juan Zhang, Jiaxing Li, Huanli Dong, Xiangke Wang, Yuguo Guo and Wenping Hu
Journal of Materials Chemistry A 2014 - vol. 2(Issue 4) pp:NaN948-948
Publication Date(Web):2013/10/24
DOI:10.1039/C3TA13535G
In this manuscript, we have proposed a new facile method for the synthesis of pure Cr2O3 nanosheets without foreign templates for the first time. We used Na2CrO4 and graphene oxide as the oxidant and reductant templates, respectively, in a hydrothermal reaction in order to synthesize porous Cr(OH)3 nanosheet precursors. By controlling the proportion of graphene oxide and Cr(VI), the carbon framework could be partially retained, resulting in graphene-divided porous Cr(OH)3 nanosheets. After calcination at 700 °C, these graphene oxide-derived Cr(OH)3 nanosheets were transformed into pure Cr2O3 nanosheets or interconnected graphene–Cr2O3 nanomaterials. The graphene–Cr2O3 nanosheets exhibited an excellent rate capability and cycling performance as an anode material in lithium ion batteries (LIB), as well as a high reversible capacity of 850 mA h g−1 at a current density of 200 mA g−1, which is the highest capacity reported for Cr2O3 anode materials.
Co-reporter:Shouwei Zhang, Wenqing Xu, Meiyi Zeng, Jie Li, Jiaxing Li, Jinzhang Xu and Xiangke Wang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 38) pp:NaN11697-11697
Publication Date(Web):2013/07/25
DOI:10.1039/C3TA12767B
Novel hierarchical core–shell iron oxide@magnesium silicate magnetic nanorods (HIO@MgSi) were fabricated via a versatile sol–gel process through hydrothermal reaction. They contain magnetic iron oxide (Fe3O4) cores and hierarchical shells (MgSi) made of ultrathin nanosheets (ca. 5 nm). Using methylene blue as a model compound, the HIO@MgSi nanorods showed fast adsorption kinetics and a superb adsorption capacity. 99.3% of methylene blue was adsorbed onto the surface of the HIO@MgSi nanorods in 40 min contact time. A maximum adsorption capacity of 2020.20 mg g−1 was achieved after 4 h. This study indicated that HIO@MgSi nanorods can be used as a potential super adsorbent to remove cationic organic pollutants effectively and rapidly from large volumes of industrial wastewater or drinking water.
Co-reporter:Wencheng Song, Xiangxue Wang, Qi Wang, Dadong Shao and Xiangke Wang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 1) pp:NaN406-406
Publication Date(Web):2014/11/03
DOI:10.1039/C4CP04289A
Polyacrylamide (PAM) grafted graphene oxide (denoted as PAM/GO) was synthesized by the plasma-induced polymerization technique and applied as an adsorbent for the simultaneous removal of radionuclides from radioactive wastewater. The interactions of PAM/GO with the radionuclides U(VI), Eu(III) and Co(II) were studied, along with their sorption kinetics. The results indicated that radionuclide sorption on PAM/GO was affected by the solution pH and ionic strength. The maximum sorption capacities of U(VI), Eu(III) and Co(II) on PAM/GO (0.698, 1.245 and 1.621 mmol g−1, respectively) at pH = 5.0 ± 0.1 and T = 295 K were much higher than those of radionuclides on GO and other adsorbents. The thermodynamic data (ΔH0, ΔS0 and ΔG0) calculated from the temperature-dependent sorption isotherms suggested that the sorption of radionuclides on PAM/GO was a spontaneous and endothermic process. These results indicate that PAM/GO is a promising material for the control of radionuclide pollution.
Co-reporter:Xi-Lin Wu, Lei Wang, Chang-Lun Chen, An-Wu Xu and Xiang-Ke Wang
Journal of Materials Chemistry A 2011 - vol. 21(Issue 43) pp:NaN17359-17359
Publication Date(Web):2011/09/23
DOI:10.1039/C1JM12678D
A composite material, containing magnetite particles, graphene and layered double hydroxides (LDHs) was fabricated through a simple two-step reaction. Graphene was used as the matrix for supporting magnetite particles and LDH nanoplates. The synthesized magnetite-graphene-LDH (MGL) composites were characterized by field emission scanning electron microscopic (FE-SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HR-TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier transformed infrared (FTIR) spectroscopy, N2adsorption-desorption, and X-ray photoelectron spectroscopy (XPS). The MGL composites were applied to remove arsenate from aqueous solutions and could be easily separated by magnetic separation process. The results showed enhanced adsorption capacity of arsenate on the MGL as compared to that of pure Mg/Al LDHs. The surface area of MGL is greatly enhanced through the incorporation of magnetite particles and graphene, which provides more active sites for arsenate uptake. Moreover, LDHs were hybridized with mechanically and chemically stable graphene materials, providing an accessible diffusion pathway in the macropore domain, and therefore their adsorption capacity was enhanced. The fast and efficient adsorption of arsenate from solution to MGL suggests that the MGL composites are potential and suitable materials in the preconcentration of arsenate from large volumes of aqueous solutions in wastewater treatment.
Co-reporter:Shouwei Zhang, Meiyi Zeng, Jiaxing Li, Jie Li, Jinzhang Xu and Xiangke Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 12) pp:NaN4397-4397
Publication Date(Web):2014/01/06
DOI:10.1039/C3TA14604A
A facile and scalable in situ synthetic strategy (simultaneous template–graphitization) was developed to fabricate carbon-stabilized Fe/Fe3C nanoparticles, which were homogeneously embedded in porous carbon sheets (PMCS) as an excellent adsorbent for wastewater treatment. In the synthesis, the graphitic catalyst precursor (Fe(NO3)3) and template agent (Al(NO3)3) were introduced simultaneously into the agar hydrogel through the coordination of the metal precursor with the functional groups of agar, thus resulting in simultaneous realization of the template and graphitization of the carbon source under heat treatment. The PMCS with high surface area (1023.2 m2 g−1) exhibited high adsorption capacities and fast adsorption rates toward dyes. Using methylene blue (MB), methyl orange (MO) and crystal violet (CV) as model pollutants, the maximum adsorption capabilities for MB, MO, and CV reached 1615.9, 1062.4 and 1728.3 mg g−1, respectively. Moreover, the possibility of magnetic separation also facilitated its application in wastewater treatment on a large scale. This multifunctional material can potentially be used as a super adsorbent to efficiently remove pollutants from wastewater.
Co-reporter:Shouwei Zhang, Jiaxing Li, Xiangke Wang, Yongshun Huang, Meiyi Zeng and Jinzhang Xu
Journal of Materials Chemistry A 2015 - vol. 3(Issue 18) pp:NaN10126-10126
Publication Date(Web):2015/03/23
DOI:10.1039/C5TA00635J
1D Ag@AgVO3 nanowire/graphene/protonated g-C3N4 nanosheet (Ag@AgVO3/rGO/PCN) heterojunctions are fabricated via a simple electrostatic self-assembly process followed by a photochemical reduction method. In this hybrid structure, 1D Ag@AgVO3 nanowires penetrate through 2D nanosheets (graphene and PCN), forming a 3D hybrid photocatalyst, which is applied as an efficient visible light driven photocatalyst for organic pollutant degradation. Its enhanced photocatalytic activity is ascribed to the well-known electronic conductivity of 2D graphene, the intense visible light absorption of 1D Ag@AgVO3 nanowires, large surface areas and rapid photogenerated charge interface transfer and separation. Our results provide a facile way to fabricate hierarchical g-C3N4-based photocatalysts in a controlled manner and highlight promising prospects by adopting an integrative 1D and 2D nanomaterial strategy to design more efficient semiconductor-based composite photocatalysts with high photocatalytic activities and a wide spectral response toward environmental and energy applications.
Co-reporter:Jie Li, Qiaohui Fan, Yijin Wu, Xiangxue Wang, Changlun Chen, Zhiyong Tang and Xiangke Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 5) pp:NaN1746-1746
Publication Date(Web):2015/12/23
DOI:10.1039/C5TA09132B
Potentially toxic metals and dyes commonly coexist in industrial wastewaters, posing a serious threat to public health and the environment and making the treatment more challenging. Herein, we report a novel magnetic polydopamine (PDA)–LDH (MPL) bifunctional material, which is fabricated by an easy and green approach for the simultaneous removal of potentially toxic metals and anionic dyes. In this assembly, both PDA and LDHs are expected to capture these pollutants. In a mono-component system, the removal behaviors showed heterogeneous removal capacities of 75.01, 624.89 and 584.56 mg g−1 for Cu(II), methyl orange (MO) and Congo red (CR), respectively. Interestingly, the presence of CR and MO enhanced the removal of Cu(II) significantly in the Cu(II)–dye binary system. However, the presence of Cu(II) had no significant effect on dyes. Based on the characterization results including X-ray diffraction (XRD) analysis, Fourier transformed infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and elemental mapping, the removal of Cu(II) was mainly controlled by bonding with surface functional groups (hydroxyl, catechol, imine and amine groups), coupled with isomorphic substitution and surface precipitation. In summary, such a green and facile synthesis method, efficient removal performance and superior reusability suggest that the MPL assemblies have practical application potential for integrative and efficient treatment of coexisting toxic pollutants.
Co-reporter:Jie Li, Changlun Chen, Shouwei Zhang and Xiangke Wang
Environmental Science: Nano 2014 - vol. 1(Issue 5) pp:NaN495-495
Publication Date(Web):2014/07/10
DOI:10.1039/C4EN00044G
This study investigated the influence of the structure characteristics of carbon nanotubes (CNTs), such as surface oxygen-containing functional groups, specific surface area (SSA) and concentration of defects, on the adsorption–desorption hysteresis of a metal cation (Cu(II)) and two oxoanions (As(V) and Cr(VI)), from single, double and multi-walled CNTs (SWCNTs, DWCNTs and MWCNTs), and two oxidized MWCNTs with different oxygen concentrations (MWCNTs-O1, 2.51 wt% O and MWCNTs-O2, 3.5 wt% O). Oxygen-containing functional groups contributed to an increase in the adsorption capacity for Cu(II) from aqueous solutions, but a decrease in adsorption capacity for Cr(VI) and As(V). The order of adsorption capacities based on CNT SSA was MWCNTs-O2 > MWCNTs-O1 > MWCNTs > DWCNTs > SWCNTs, which was consistent with the order of CNT defect contents. Desorption hysteresis index (HI) values for Cu(II) increased as the number of functional groups increased. For Cr(VI) and As(V), however, HI values decreased as the number of functional groups increased. HI values decreased with an increase in metal ion surface coverage on CNTs. There may be a shift in the mechanisms of metal ion adsorption by CNTs, from more irreversible to more reversible processes, with an increase in adsorbed metal ions. An understanding of the desorption hysteresis of heavy metal ions is important and useful for the application and risk assessment of CNTs in the natural environment.
Co-reporter:XiaoLi Tan, Jun Hu, Gilles Montavon and XiangKe Wang
Dalton Transactions 2011 - vol. 40(Issue 41) pp:NaN10960-10960
Publication Date(Web):2011/09/14
DOI:10.1039/C1DT10740B
The sorption speciation of Ni(II) on Ca-montmorillonite was evaluated using a combination of batch experiments, extended X-ray absorption fine structure (EXAFS) spectroscopy and modeling. The pH and temperature at the aqueous-montmorillonite interface affects both the extent of Ni(II) sorption as well as the local atomic structure of the adsorbed Ni(II) ions. At 0.001 mol L−1 Ca(NO3)2 and low pH, the study reveals that the majority of Ni(II) is adsorbed in the interlayers of Ca-montmorillonite coordinated by six water molecules in an octahedron as an outer-sphere complex. At higher pH, inner-sphere surface complexes are formed. The Ni–Si/Al distances (RNi–Al = 3.00 Å, RNi–Si1 = 3.10 Å and RNi–Si2 = 3.26 Å) determined by EXAFS confirm the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5 and 8.5. At pH 10.0, the Ni–Ni/Si distances (RNi–Ni = 3.07 Å and RNi–Si = 3.26 Å) indicates the formation of Ni-phyllosilicate precipitates. A rise in temperature promotes inner-sphere complexation, which in turn leads to an increase in Ni(II) sorption on Ca-montmorillonite. Sorption edges are fitted excellently by surface complexation model (SCM) with the aid of surface species determined from EXAFS spectroscopy.
Co-reporter:Guixia Zhao, Xuemei Ren, Xing Gao, Xiaoli Tan, Jiaxing Li, Changlun Chen, Yuying Huang and Xiangke Wang
Dalton Transactions 2011 - vol. 40(Issue 41) pp:NaN10952-10952
Publication Date(Web):2011/09/14
DOI:10.1039/C1DT11005E
Few-layered graphene oxide (FGO) was synthesized from graphite by using the modified Hummers method, and was characterized by scanning electron microscopy, atomic force microscopy, powder X-ray diffraction, X-ray photoelectron spectroscopy and Raman spectroscopy. The prepared FGO was used to adsorb Pb(II) ions from aqueous solutions. The abundant oxygen-containing groups on the surfaces of FGO played an important role in Pb(II) ion adsorption on FGO. The adsorption of Pb(II) ions on FGO was dependent on pH values and independent of ionic strength. The adsorption of Pb(II) ions on FGO was mainly dominated by strong surface complexation. From the adsorption isotherms, the maximum adsorption capacities (Csmax) of Pb(II) ions on FGO calculated from the Langmuir model were about 842, 1150, and 1850 mg g−1 at 293, 313, and 333 K, respectively, higher than any currently reported. The FGO had the highest adsorption capacities of today's nanomaterials. The thermodynamic parameters calculated from the temperature dependent adsorption isotherms indicated that the adsorption of Pb(II) ions on FGO was a spontaneous and endothermic process.
Co-reporter:Shouwei Zhang, Wenqing Xu, Meiyi Zeng, Jiaxing Li, Jinzhang Xu and Xiangke Wang
Dalton Transactions 2013 - vol. 42(Issue 37) pp:NaN13424-13424
Publication Date(Web):2013/07/01
DOI:10.1039/C3DT51492G
Wide spectral responsive 3D hierarchical CdS/α-Fe2O3 heterojunction nanocomposites were synthesized through a facile chemical bath method under mild conditions, and used for the reduction of Cr(VI) into Cr(III) under visible light irradiation. The effects of CdS/α-Fe2O3 molar ratio in the nanocomposites on the crystal phases, microstructures, optical absorption properties, and photocatalytic reduction of Cr(VI) were investigated comparatively. It was found that the as-synthesized CdS/α-Fe2O3 nanocomposites with a suitable CdS content (e.g., the molar ratio of Fe:Cd = 1.25:3) had not only high visible-light-driven photocatalytic activity in the Cr(VI) reduction, but also good photocatalytic stability. The enhanced photocatalytic activity can be ascribed to some CdS nanoparticles closely contacting the α-Fe2O3 microflowers to form a heterojunction structure. These tight heterojunctions of the photocatalysts result in an efficient electron–hole pairs separation at the interface, followed by fast diffusion of photogenerated charge between CdS and α-Fe2O3, which is beneficial for separating the photogenerated carriers in space and improving the photocatalytic activity.
Co-reporter:Jun Hu, Xiaoli Tan, Xuemei Ren and Xiangke Wang
Dalton Transactions 2012 - vol. 41(Issue 35) pp:NaN10810-10810
Publication Date(Web):2012/06/29
DOI:10.1039/C2DT31057K
The influence of humic acid (HA) on Ni(II) sorption to Ca-montmorillonite was examined by using a combination of batch sorption experiments and extended X-ray absorption fine structure (EXAFS) spectroscopy technique. The sorption of Ni(II) on HA–montmorillonite hybrids is strongly dependent on pH and temperature. At low pH, the sorption of Ni(II) is mainly dominated by Ni–HA–montmorillonite and outer-sphere surface complexation. The EXAFS results indicate that the first coordination shell of Ni(II) consists of ∼6 O atoms at the interatomic distances of ∼2.04 Å in an octahedral structure. At high pH, binary Ni–montmorillonite surface complexation is the dominant sorption mechanism. EXAFS analysis indicates the formation of mononuclear complexes located at the edges of Ca-montmorillonite platelets at pH 7.5, while a Ni–Al layered double hydroxide (LDH) phase at the Ca-montmorillonite surface formed with pH 8.5. At pH 10.0, the dissolved HA–Ni(II) complexation inhibits the precipitation of Ni hydroxide, and Ni–Al LDH phase forms. The rise of temperature increases the sorption capacity of Ni(II), and promotes Ni–Al LDH phase formation and the growth of crystallites. The results are important to evaluate the physicochemical behavior of Ni(II) in the natural environment.
Co-reporter:Guixia Zhao, Jiaxing Li, Lang Jiang, Huanli Dong, Xiangke Wang and Wenping Hu
Chemical Science (2010-Present) 2012 - vol. 3(Issue 2) pp:NaN437-437
Publication Date(Web):2011/10/14
DOI:10.1039/C1SC00722J
A facile method to synthesize layered manganese oxide nanosheets was developed for the first time by using graphene oxide as a template. The in situ replacement of carbon atoms on the graphene oxide framework by edge-shared [MnO6] octahedra provides a new methodology to synthesize graphene-based two-dimensional nanomaterials. The transformation of graphene oxide into δ-type MnO2 nanosheets results in an especially high surface area (157 m2 g−1), which is the highest value amongst today's MnO2 nanomaterials. Moreover, the MnO2 nanosheets demonstrated prominent capacitance (∼1017 F g−1 at a scan rate of 3 mV s−1, and ∼1183 F g−1 at a current density of 5 A g−1) and remarkable rate capability (∼244 F g−1 at a high scan rate of 50 mV s−1 and ∼559 F g−1 at a high current density of 25 A g−1), indicating their promise in high energy and power density pseudosupercapacitors.
Co-reporter:Shubin Yang, Xilin Wu, Changlun Chen, Huanli Dong, Wenping Hu and Xiangke Wang
Chemical Communications 2012 - vol. 48(Issue 22) pp:NaN2775-2775
Publication Date(Web):2012/01/18
DOI:10.1039/C2CC16565A
This work reports a new graphene-based composite for supercapacitor material, and the maximum specific capacitance of 1760.72 F g−1 at a scan rate of 5 mV s−1, with excellent cycling stability.
Co-reporter:Shouwei Zhang, Qiaohui Fan, Huihui Gao, Yongshun Huang, Xia Liu, Jiaxing Li, Xijin Xu and Xiangke Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 4) pp:NaN1422-1422
Publication Date(Web):2015/12/07
DOI:10.1039/C5TA08400H
While the synthesis of heterogeneous catalysts is well established, it is extremely challenging to fabricate complex hollow structures with mixed transition metal oxides. Herein, we report a facile in situ growth process of SiO2@Fe3O4@MnO2, followed by an etching method to synthesize a hierarchical hollow structure, namely Fe3O4@MnO2 ball-in-ball hollow spheres (Fe3O4@MnO2 BBHs). The as-prepared Fe3O4@MnO2 BBHs were applied to degrade methylene blue (MB) by catalytic generation of active radicals from peroxymonosulfate (PMS), exhibiting the merits of excellent catalytic performance, easy separation, good stability and recyclability. In this architecture, the degradation process can be divided into three layers. The outer hierarchical MnO2 nanosheets could accumulate and transport the pollutants by electrostatic interactions and catalyze the generation of active radicals for degradation. Both the inner MnO2 nanosheets and the outer Fe3O4 hollows could produce active radicals to accelerate the pollutant degradation. The active catalytic sites also existed in the inner Fe3O4 hollows, which could further degrade the highly concentrated pollutants in the hollows. This work provides new strategies for the controllable synthesis of complex hollow structures and their application in environmental remediation.
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