A carbon-based solid acid catalyst was prepared by simultaneous carbonization and sulfonation of distillers’ grain with concentrated sulfuric acid. Response surface methodology was adopted to determine the optimal preparation conditions such as sulfuric acid concentration, preparation temperature and preparation time. This catalyst was characterized by XRD, FT-IR, TG, XPS, elemental analysis, N2 adsorption/desorption and acid-base titration methods. The catalytic performance was evaluated under a certain condition in the esterification of acetic acid and n-butanol as a probe reaction. The conversion of acetic acid was 97.6% when the sulfuric acid concentration of 85 wt%, preparation temperature of 20 °C, and preparation time of 1.4 h. The high catalytic activity of this catalyst may be attributed to the higher acid density of 1.73 mmol/g by NaOH titration. The catalyst performance will weaken with the increase of reuse times, but it could be regenerated by treatment with concentrated sulfuric acid (85 wt%).

Carbon dots (CDs) are a new type of fluorescent carbon nanoparticles (CNPs). In comparison with conventional semiconductor quantum dots and organic dyes, CDs not only have the advantages of non-toxicity and high biocompatibility, but also have excellent water solubility, an adjustable luminous range, high photostability, an absence of light flicker, easy functionality, rich sources of cheap raw materials, easy large-scale syntheses and other excellent characteristics. These excellent properties endow CDs with great potential in many fields, such as environmental monitoring, sensors, catalysis, energy, light-emitting devices, cell markers and biological imaging. With these excellent properties, as well as important applications, CDs have attracted widespread attention in recent years. This article reviews recent progress in CDs in terms of their rational synthesis, tunable optical properties, and analytical applications and put forward the developmental trend of CDs.

α-Fe2O3 particle supported on diatomite (α-Fe2O3/diatomite composite) was prepared at room temperature by the chemical precipitation method using ferrous sulphate as the raw material and diatomite as supporter. α-Fe2O3/diatomite composite was characterized by XRD, FE-SEM, FT-IR and DRS. The result showed that α-Fe2O3 was uniformly loaded on the diatomite. The photocatalytic activity was investigated under visible light toward degradation of Rhodamine 6G aqueous solution and the effects of various experimental factors on Rhodamine 6G degradation were investigated. Compared with the α-Fe2O3, α-Fe2O3/diatomite composite had significantly enhanced activity in the degradation of Rhodamine 6G under visible light irradiation. Besides, the photostability of catalysts was also investigated. The experimental results indicated that the prepared composite is a promising material for the wastewater treatment for its good catalytic performance property and long-term stability.

Cu2O/Na-bentonite (Cu2O/NB) composites were firstly synthesized by a simple deposition method. The morphology and composition of the prepared catalysts were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) spectroscopy, Brunauer–Emmett–Teller (BET) specific surface area. The results show that the Cu2O microparticles can be immobilized on the surface of the NB. Visible-light photocatalytic properties of the Cu2O/NB composites were evaluated using methyl orange (MO) as a model pollutant and the effects of various experimental factors on MO decolorization were investigated. Cu2O/NB composites demonstrated a much higher photocatalytic activity than the pure Cu2O particles under similar experimental conditions.

•ChNTs were functionalized by surface grafting with MPTMS•ChNTs-SH were characterized by XRD, FTIR, XPS, SEM, TEM and N2 adsorption-desorption•The adsorption was fitted by pseudo-second order kinetic model and interpreted by the Langmuir equation•ChNTs-SH could significantly enhance the adsorption capacity for Pb(II) and Cd(II) in comparison with ChNTsChrysotile nanotubes (ChNTs) synthesized under hydrothermal conditions were functionalized by surface grafting in toluene with 3-mercaptopropyltrimethoxysilane (MPTMS). The mercapto functionalized ChNTs (ChNTs-SH) were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption–desorption. The adsorption of Pb(II) and Cd(II) on ChNTs-SH was investigated systematically by evaluating the effects of contact time, adsorbent dosage, initial pH and temperature. Initial pH could play an important role on the adsorption of Pb(II) and Cd(II) onto ChNTs-SH. The adsorption kinetics and isotherms of Pb(II) and Cd(II) on ChNTs-SH indicated that the kinetic data of adsorption reactions were well described by the pseudo-second-order model (R2 = 0.9960 and 0.9970, respectively) and the adsorption isotherms were fitted well by the Langmuir model (qm Pb(II) = 83.96 mg/g, qm Cd(II) = 39.23 mg/g at 298 ± 1 K). The thermodynamic parameters (ΔG, ΔH and ΔS) indicated that the adsorption process of Pb(II) and Cd(II) on ChNTs-SH was spontaneous and endothermic. ChNTs-SH could obviously improve the adsorption capacity for Pb(II) by 225.4% and for Cd(II) by 123.5% as compared with ChNTs. Overall, ChNTs-SH could provide a potential remedy for heavy metal contamination in wastewater.

Surface-Enhanced Raman Scattering (SERS) spectroscopy has become one of the most widely pursued spectroscopic tools, as a powerful and extremely sensitive analytical technique with applications in chemical production, biochemistry, and environmental monitoring, owing to its production of unique spectroscopic fingerprints, high sensitivity, and non-destructive data acquisition. The key obstacle for the application of SERS-based sensors is the lack of robust and simple fabrication strategies for renewable SERS substrates with huge and stable Raman enhancement. The rational design of SERS sensors with defined physical and chemical properties is vital for successful applications in many analytical fields. This highlight will summarize current advances in the design and the employment of nanostructured materials in SERS substrates, especially from the dimensional point of view. We will then talk about synthesis methods and the novel properties of these nanostructured materials with their potential applications in SERS.

The development and innovation of strategies for the fabrication of oriented nanostructures has been among the hot research topics in the field of nanoscience because of the novel properties of these nano-arrays, that differ drastically from their bulk counterparts, and their potential applications in many areas including the chemical, physical, biological and engineering fields. Herein, we have demonstrated an extremely simple procedure for the fabrication of a forest of oriented silver nanowires at ambient temperature in aqueous solution without a hard template. The oriented silver nanowire arrays exhibit better field emission performance than that of a single nanowire or non-oriented nanowires. By variation of the experimental parameters, the diameter and length of the oriented Ag nanowires can be tuned accordingly. The successful fabrication of a forest of the oriented nanowires under mild conditions without a template not only provides an efficient route to selectively control the preparation of oriented nano-arrays, but also provides new insights into the underlying surfactant-mediated mechanism of nano- and micro-architectures. This strategy might be extended to fabricate other metal and semiconductor nanocrystal arrays and widen their potential applications in many fields.

The simulated radionuclide Eu(III) was separated effectively by using the in-situ synthesis of hydrotalcite. The optimal conditions of pH, Mg/(Eu+Al) molar ratio, and initial Eu(III) concentration for separating Eu(III) and achieving a single hydrotalcite phase were investigated systematically and determined to be 10, 3.0, and 600 mg L−1, respectively. Under the optimal separation conditions, the removal percentage of Eu(III) reached 99.8%. The characterization results suggested that Eu(III) was incorporated into the crystal lattice of hydrotalcite completely and fully immobilized in the structure of spinel by calcining, and the morphology of the synthetic hydrotalcite containing Eu(III) was in hexagonal platelet-like sheet.

The acid-activated sepiolite (ASEP) was prepared by physical purification and acid activation of natural sepiolite, and was characterized by XRD, FT-IR, SEM and N2 adsorption–desorption. The prepared ASEP was applied for the sorption of 60Co(II) from aqueous solutions. The sorption of 60Co(II) from aqueous solutions by ASEP was investigated as a function of contact time, solid content, pH, ionic strength, foreign ions, humic acid (HA) and temperature. The results indicated that the sorption of 60Co(II) on ASEP was strongly dependent on pH values. At low pH, the sorption of 60Co(II) was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation or surface precipitation was the main sorption mechanism at high pH. The presence of HA increased the sorption of 60Co(II) on ASEP at low pH values, and reduced the sorption at high pH values. The Langmuir and Freundlich models were applied to simulate the sorption of 60Co(II) at three temperatures of 298, 318 and 338 K. The thermodynamic parameters (\( \Updelta G^\circ ,\,\;\Updelta S^\circ \) and \( \Updelta H^\circ \)) calculated from the temperature dependent sorption isotherms indicated that the sorption of 60Co(II) on ASEP was an endothermic and spontaneous process. ASEP has a great application potential for cost-effective disposal of 60Co(II) from large volumes of aqueous solutions.

The simulated radionuclides Sr and Nd were simultaneously separated from high level liquid waste (HLLW) using in situ hydrotalcite synthesis. The optimum conditions of removal of Sr and Nd determined by acid–base titration, single factor test and X-ray powder diffraction (XRD) are that the initial CNd(III), initial CSr(II), pH range and (Sr + Mg)/(Nd + Al) molar ratio are 70, 90 mg L−1, 10–11 and around 3, respectively. Both the removal rates of Sr and Nd could reach more than 99 % under these conditions. The synthetic samples were characterized by XRD, Fourier transform infrared spectroscopy, scanning electron microscope. The results indicate that as-synthesized samples possess single hydrotalcite phase, which confirms that Sr and Nd separated from HLLW are all embedded into the crystal lattice of Sr–Nd-HTlcs. In addition, the morphology of Sr–Nd-HTlcs is in hexagonal platelet-like sheets and the particle size is about 1 μm. From the XRD patterns of Sr–Nd-HTlc calcination product, we only observe the phases of spinel and MgO and don’t find the phases of SrO and Nd2O3, which show that Sr and Nd embedded into the crystal lattice of Sr–Nd-HTlc still occur in the structure of spinel.

The bentonite/iron oxide magnetic composites were prepared by co-precipitation method, and characterized by Fourier transform infrared spectroscopy, X-ray powder diffraction and scanning electron microscope. The prepared bentonite/iron oxide magnetic composites were used as a sorbent for the removal of Co(II) ions from radioactive wastewater. The results demonstrated that the sorption of Co(II) was strongly dependent on pH and ionic strength at low pH values. The sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange at low pH whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The presence of iron oxide in the composites also contributes to the sorption of Co(II) ions on the magnetic composites. The experimental data were well described by Langmuir model. The thermodynamic parameters (∆G°, ∆S°, ∆H°) calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on bentonite/iron oxide magnetic composites was an endothermic and spontaneous processes.

The mesoporous molecular sieves (Al-MCM-41) are synthesized with montmorillonite as silica–alumina source by hydrothermal method. The application of Al-MCM-41 for the adsorption of Th(IV) from aqueous solution is studied by batch technique. The effects of contact time, solid content, pH, ionic strength, foreign ions, and temperature are determined, and the results indicate that the adsorption of Th(IV) to Al-MCM-41 is strongly dependent on pH values but independent of ionic strength. The adsorption isotherms are simulated by D–R and Freundlich models well. The thermodynamic parameters (ΔH0, ΔS0, ΔG0) are calculated from the temperature dependent adsorption isotherms at 293, 313 and 333 K, respectively, and the results suggest that the adsorption of Th(IV) on Al-MCM-41 is a spontaneous and endothermic process. Al-MCM-41 is a suitable material for the preconcentration of Th(IV) from large volumes of aqueous solutions.

Prepared chrysotile nanotubes (ChNTs) were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), N2 adsorption•desorption, X-ray photoelectron spectrometer (XPS) and Fourier transform infrared spectroscopy (FTIR). ChNTs were employed to investigate the influence of various experimental parameters on thorium adsorption. Some isotherm and kinetic models were applied to analyze the experimental data among which the Langmuir and pseudo-second-order models were better than others. The pH and ionic strength results indicated that adsorption of Th(IV) on ChNTs was strongly affected by pH values and ionic strength. The possible adsorption mechanism was studied by FTIR and XPS techniques. It was found that both electrostatic interaction and surface complexation mechanisms played important roles in adsorption process.

•Magnetic chrysotile nanotubes were synthesized under hydrothermal conditions.•The products have preferable saturation magnetization (12.78 A m2 kg−1).•Adsorption behavior had been studied for the Pb(II), Cd(II) and Cr(III).•The products remain higher adsorption capacity toward heavy metal ions than ChNTs.In view of increasing attention of magnetic materials in the field of separation science and technology, we prepared a kind of magnetic material (magnetic chrysotile nanotubes, viz., magnetic ChNTs) by the doped method. Different experimental conditions were studied using different characterization analysis. The characterization results showed that the prepared samples had hollow structure and preferable saturation magnetization. Magnetic ChNTs could be effectively separated from aqueous solutions by a permanent magnet. The adsorption kinetics and isotherms of magnetic ChNTs for Pb(II), Cd(II) and Cr(III) were fitted well by the pseudo-second-order model and Langmuir model, respectively. The possible adsorption mechanism was discussed mainly according to characterizations (FTIR, XPS) and experiments, which together suggested that Pb(II), Cd(II) and Cr(III) adsorption on magnetic ChNTs most possibly involved electrostatic interaction and surface complexation.