Co-reporter:Muhammad Ahmad, Sitong Liu, Nasir Mahmood, Asif Mahmood, Muhammad Ali, Maosheng Zheng, Jinren Ni
Bioresource Technology 2017 Volume 234(Volume 234) pp:
Publication Date(Web):1 June 2017
DOI:10.1016/j.biortech.2017.03.076
•Size of FPUF carrier significantly alters micro-environments for SND.•Middle sized carriers enhance nitrogen removal in micro-aerobic bioreactors.•Optimal sized carrier allows habitats of both nitrifiers and denitrifiers.•Ca. brocadia strongly co-aggregated with other bacteria in middle layer of carrier.•Smaller or larger carriers limit effective zones for denitrifiers or mass transfer.In this study, effects of porous carrier’s size (polyurethane-based) on microbial characteristics were systematically investigated in addition to nitrogen removal performance in six microaerobic bioreactors. Among different sized carriers (50, 30, 20, 15,10, 5 mm), 15 mm carrier showed highest nitrogen removal (98%) due to optimal micro-environments created for aerobic nitrifiers in outer layer (0–7 mm), nitrifiers and denitrifiers in middle layer (7–10 mm) and anaerobic denitrifiers in inner layer (10–15 mm). Candidatus brocadia, a dominant anammox bacteria, was solely concentrated close to centroid (0–70 μm) and strongly co-aggregated with other bacterial communities in the middle layer of the carrier. Contrarily, carriers with a smaller (<15 mm) or larger size (>15 mm) either destroy the effective zone for anaerobic denitrifiers or damage the microaerobic environments due to poor mass transfer. This study is of particular use for optimal design of carriers in enhancing simultaneous nitrification-denitrification in microaerobic wastewater treatment processes.Download high-res image (403KB)Download full-size image
Co-reporter:Mengyao Gui;Qian Chen;Tao Ma;Maosheng Zheng
Applied Microbiology and Biotechnology 2017 Volume 101( Issue 4) pp:1717-1727
Publication Date(Web):16 November 2016
DOI:10.1007/s00253-016-7984-8
Effects of heavy metals on aerobic denitrification have been poorly understood compared with their impacts on anaerobic denitrification. This paper presented effects of four heavy metals (Cd(II), Cu(II), Ni(II), and Zn(II)) on aerobic denitrification by a novel aerobic denitrifying strain Pseudomonas stutzeri PCN-1. Results indicated that aerobic denitrifying activity decreased with increasing heavy metal concentrations due to their corresponding inhibition on the denitrifying gene expression characterized by a time lapse between the expression of the nosZ gene and that of the cnorB gene by PCN-1, which led to lower nitrate removal rate (1.67∼6.67 mg L−1 h−1), higher nitrite accumulation (47.3∼99.8 mg L−1), and higher N2O emission ratios (5∼283 mg L−1/mg L−1). Specially, promotion of the nosZ gene expression by increasing Cu(II) concentrations (0∼0.05 mg L−1) was found, and the absence of Cu resulted in massive N2O emission due to poor synthesis of N2O reductase. The inhibition effect for both aerobic denitrifying activity and denitrifying gene expression was as follows from strongest to least: Cd(II) (0.5∼2.5 mg L−1) > Cu(II) (0.5∼5 mg L−1) > Ni(II) (2∼10 mg L−1) > Zn(II) (25∼50 mg L−1). Furthermore, sensitivity of denitrifying gene to heavy metals was similar in order of nosZ > nirS ≈ cnorB > napA. This study is of significance in understanding the potential application of aerobic denitrifying bacteria in practical wastewater treatment.
Co-reporter:Dong Xu;Sitong Liu;Qian Chen
AMB Express 2017 Volume 7( Issue 1) pp:40
Publication Date(Web):15 February 2017
DOI:10.1186/s13568-017-0336-y
The microbial community diversity in anaerobic-, anoxic- and oxic-biological zones of a conventional Carrousel oxidation ditch system for domestic wastewater treatment was systematically investigated. The monitored results of the activated sludge sampled from six full-scale WWTPs indicated that Proteobacteria, Chloroflexi, Bacteroidetes, Actinobacteria, Verrucomicrobia, Acidobacteria and Nitrospirae were dominant phyla, and Nitrospira was the most abundant and ubiquitous genus across the three biological zones. The anaerobic-, anoxic- and oxic-zones shared approximately similar percentages across the 50 most abundant genera, and three genera (i.e. uncultured bacterium PeM15, Methanosaeta and Bellilinea) presented statistically significantly differential abundance in the anoxic-zone. Illumina high-throughput sequences related to ammonium oxidizer organisms and denitrifiers with top50 abundance in all samples were Nitrospira, uncultured Nitrosomonadaceae, Dechloromonas, Thauera, Denitratisoma, Rhodocyclaceae (norank) and Comamonadaceae (norank). Moreover, environmental variables such as water temperature, water volume, influent ammonium nitrogen, influent chemical oxygen demand (COD) and effluent COD exhibited significant correlation to the microbial community according to the Monte Carlo permutation test analysis (p < 0.05). The abundance of Nitrospira, uncultured Nitrosomonadaceae and Denitratisoma presented strong positive correlations with the influent/effluent concentration of COD and ammonium nitrogen, while Dechloromonas, Thauera, Rhodocyclaceae (norank) and Comamonadaceae (norank) showed positive correlations with water volume and temperature. The established relationship between microbial community and environmental variables in different biologically functional zones of the six representative WWTPs at different geographical locations made the present work of potential use for evaluation of practical wastewater treatment processes.
Co-reporter:Yujiao Long, Hongna Li, Xuan Xing, Jinren Ni
Chemical Engineering Journal 2017 Volume 325(Volume 325) pp:
Publication Date(Web):1 October 2017
DOI:10.1016/j.cej.2017.05.067
•Simple addition of Fe2+ greatly enhanced M. aeruginosa removal in BDD-CF system.•Enhancement with Fe2+ was dominated by heterogeneous electro-Fenton mechanism.•Electrochemical reduction on CF cathode sustained the cycle of Fe(III)/Fe(II).•Fe2+ addition intensified the lipid peroxidation and degradation of microcystin.•The added Fe could be easily recycled due to its complete deposition on CF cathode.This study presented a significant enhanced removal of Microcystis aeruginosa by simple addition of Fe2+ at circumneutral pH in the electrochemical system with boron-doped diamond (BDD) anode and carbon felt (CF) cathode. Results showed that over 99.9% of the M. aeruginosa cells were removed in 60 min when 0.2 mM Fe2+ was added to the system. The pseudo-first order rate constant for BDD-CF-Fe2+ system was almost 15 times higher than that (0.005 min−1) for BDD-CF system. The excellent performance of the BDD-CF-Fe2+ system over the BDD-CF system was observed over a wide range of pH from 3 to 9. Based on the evolution of Fe2+/Fe3+, pH, H2O2 and OH, mechanism of enhanced removal of M. aeruginosa was revealed in the BDD-CF-Fe2+ system. H2O2 was electrochemically generated through reduction of dissolved oxygen on the surface of the CF cathode, and the added Fe2+ was rapidly adsorbed and precipitated also on the CF cathode. Comparisons of BDD-CF-Fe2+, BDD-CF-Fe3+ and BDD-CF-Fe2+/Fe3+ systems proved that the electrochemical reduction of Fe(III) to Fe(II) could guarantee the sustainable cycle between Fe(II) and Fe(III). Through heterogeneous electro-Fenton reactions, much higher amount of OH would be continuously generated compared with the BDD-CF system. Thereby, the lipid peroxidation on the cell membrane of M. aeruginosa was intensified through the addition of Fe2+. Moreover, the degradation of intracellular microcystin was remarkably accelerated, and the extracellular microcystin was controlled more safely due to Fe2+ addition. This study provided an alternative method to enhance the electrochemical mitigation of cyanobacteria-polluted waters.
Co-reporter:Mengyao Gui;Qian Chen
Applied Microbiology and Biotechnology 2017 Volume 101( Issue 12) pp:5139-5147
Publication Date(Web):01 March 2017
DOI:10.1007/s00253-017-8191-y
This paper presents the effect of NaCl on aerobic denitrification by a novel aerobic denitrifier strain Achromobacter sp. GAD-3. Results indicated that the aerobic denitrification process was inhibited by NaCl concentrations ≥20 g L−1, leading to lower nitrate removal rates (1.67∼4.0 mg L−1 h−1), higher nitrite accumulation (50.2∼87.4 mg L−1), and increasing N2O emission ratios (13∼72 mg L−1/mg L−1). Poor performance of aerobic denitrification at high salinity was attributed to the suppression of active microbial biomass and electron donating capacity of strain GAD-3. Further studies on the corresponding inhibition of the denitrifying gene expression by higher salinities revealed the significant sensitivity order of nosZ (for N2O reductase) > cnorB (for NO reductase) ≈ nirS (for cytochrome cd(1) nitrite reductase) > napA (for periplasmic nitrate reductase), accompanied with a time-lapse expression between nosZ and cnorB based on reverse transcription and real-time quantitative polymerase chain reaction (RT-qPCR) analysis. The insights into the effect of NaCl on aerobic denitrification are of great significance to upgrade wastewater treatment plants (WWTPs) containing varying levels of salinity.
Co-reporter:Yao Yue;Adrian Chappell;Mengtian Huang;Yichu Wang;Alistair G. L. Borthwick;Kristof Van Oost;Shilong Piao;Tianhong Li;Philippe Ciais;Tao Wang
PNAS 2016 Volume 113 (Issue 24 ) pp:6617-6622
Publication Date(Web):2016-06-14
DOI:10.1073/pnas.1523358113
Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study
attempts to quantify the lateral transport of soil carbon and consequent land−atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion
rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced
180 ± 80 Mt C⋅y−1 of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y−1, equivalent to 8–37% of the terrestrial carbon sink previously assessed in China. Interestingly, the “hotspots,” largely
distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m−2⋅y−1), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after
the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced
CO2 in the terrestrial budget, hence reducing the level of uncertainty.
Co-reporter:Wen Liu, Xiao Zhao, Ting Wang, Jie Fu and Jinren Ni
Journal of Materials Chemistry A 2015 vol. 3(Issue 34) pp:17676-17684
Publication Date(Web):24 Jul 2015
DOI:10.1039/C5TA04521E
A novel flower-like titanate nanomaterial (titanate nanoflowers, TNFs) was synthesized through a hydrothermal method using nano-anatase and sodium hydroxide, and used for mercury(II) removal from aqueous solution. The large surface area (187.32 m2 g−1) and low point of zero charge (3.04) of TNFs facilitated the adsorption of cations. Adsorption experiments indicated that TNFs could quickly capture 98.2% of Hg(II) from solution within 60 min at pH 5. The maximum adsorption capacity of Hg(II) was as large as 454.55 mg g−1 calculated by the Langmuir isotherm model. Moreover, selective adsorption of Hg(II) by TNFs was observed with the coexistence of other conventional cations (i.e., Na+, K+, Mg2+ and Ca2+) even at 10 times concentration of Hg(II). XRD analysis indicated that the prepared TNFs were a kind of tri-titanate composed of an edge-sharing triple [TiO6] octahedron and interlayered Na+/H+, and ion-exchange between Hg2+ and Na+ was the primary adsorption mechanism. Furthermore, it was interesting that the basic crystal structure of TNFs, tri-titanate (Ti3O72−), transformed into hexa-titanate (Ti6O132−) after adsorption, resulting in the trapping of Hg(II) into the lattice tunnel of this hexa-titanate. Desorption experiments also confirmed the irreversible adsorption due to Hg(II) trapped in TNFs, which achieved safe disposal of this highly toxic metal in practical application.
Co-reporter:Wen Liu, Xiao Zhao, Alistair G. L. Borthwick, Yanqi Wang, and Jinren Ni
ACS Applied Materials & Interfaces 2015 Volume 7(Issue 35) pp:19726
Publication Date(Web):August 24, 2015
DOI:10.1021/acsami.5b05263
Fe-deposited titanate nanotubes (Fe-TNTs) with high photocatalytic activity and adsorptive performance were synthesized through a one-step hydrothermal method. Initial As(III) oxidation followed by As(V) adsorption by Fe-TNTs could simultaneously remove these two toxic pollutants from aqueous solutions. The apparent rate constant value for photo-oxidation of As(III) under UV irradiation by Fe-TNTs was almost 250 times that of unmoidified TNTs. Under visible light, the Fe-TNTs also exhibited enhanced photocatalytic activity after Fe was deposited. Fe3+ located in the interlayers of TNTs acted as temporary electron- or hole-trapping sites, and attached α-Fe2O3 played the role of a charge carrier for electrons transferred from TNTs. These two effects inhibited electron–hole pair recombination thus promoting photocatalysis. Moreover, the As(V) adsorptive performance of Fe-TNTs also improved, owing to the presence of additional adsorption sites, α-Fe2O3, as well as increased pHPZC. Furthermore, Fe-TNTs exhibited good photocatalytic and adsorptive performace even after 5 reuse cycles. The present tests, concerning an initial As(III) photocatalysis and subsequent As(V) adsorption process, highlight the feasibility and importance of Fe used to modify TNTs. This study proposes a feasible method to simultaneously remove As(III) and As(V) from contaminated water using a novel Ti-based nanomaterial.Keywords: As; dual-enhanced; Fe-deposited; photocatalytic activity; titanate nanotubes; visible light
Co-reporter:Xuezhao Li, Wen Liu, Jinren Ni
Microporous and Mesoporous Materials 2015 Volume 213() pp:40-47
Publication Date(Web):1 September 2015
DOI:10.1016/j.micromeso.2015.04.018
•Short-cut hydrothermal synthesis of TNTs by nano-anatase and NaOH was achieved.•Similar crystal array of anatase and tri-titanate greatly reduced reaction time.•Longer Ti–O–Ti bond in anatase than in rutile lead to easier breakage of the bond.•Over 90% reaction time was saved for TNTs synthesis as an excellent adsorbent.•Abundant –ONa sites on TNTs guaranteed excellent adsorption performance.Conventional hydrothermal synthesis of titanate nanotubes (TNTs) by P25 TiO2 and NaOH has been blamed for its long reaction time (continuous heating for three days). This paper presented a short-cut hydrothermal synthesis of TNTs by nano-anatase and NaOH, which significantly reduced the reaction time from 72 to 6 h while the other experimental conditions were same. Essential interpretation of such a surprising reduction of reaction time was given in terms of TEM, XRD and FTIR analysis. It indicates that the transformation from anatase to sodium tri-titanate nanotubes includes the following three steps: (1) aggregation of spherical anatase particles (0–1 h), (2) morphologic transformation to titanate nanosheets with fewer visible anatase crystal arrays (1–3 h), and (3) crimping of tri-titanate nanosheets and a final generation of TNTs (3–6 h). Further comparison with TNTs synthesis process from P25 TiO2 (ca. 80% of anatase and 20% of rutile) indicates that the rate-limiting step for breakage of Ti–O–Ti bond is largely controlled by crystal array of the concerned nanomaterials. The as-prepared TNTs are proved to exhibit similar Cd adsorption capacity compared with conventional TNTs based on batch adsorption experiments. The widely distributed anatase in nature as well as its over 90% reaction time saving in TNTs preparation process under facile conditions makes the proposed short-cut synthesis of great potential in engineering applications.
Co-reporter:Wen Liu, Pan Zhang, Alistair G.L. Borthwick, Hao Chen, Jinren Ni
Journal of Colloid and Interface Science 2014 Volume 423() pp:67-75
Publication Date(Web):1 June 2014
DOI:10.1016/j.jcis.2014.02.030
•TNTs show large adsorption capacities for both Tl(I) and Tl(III).•Ion-exchange between Tl+ and Na+ is the primary mechanism for Tl(I) adsorption.•Ion-exchange plays the main role in adsorption at low Tl(III) concentration.•Co-precipitation of Tl(OH)3 and TNTs is dominant at high Tl(III) concentration.•TNTs can be re-used efficiently after HNO3 desorption and NaOH regeneration.Hydrothermally-synthesized titanate nanotubes (TNTs) are found to be excellent at adsorption of highly toxic thallium ions. Uptake of both thallium ions is very fast in the first 10 min. The adsorption isotherm of Tl(I) follows the Langmuir model with maximum adsorption capacity of 709.2 mg g−1. Ion-exchange between Tl+ and Na+ in the interlayers of TNTs is the primary mechanism for Tl(I) adsorption. Excess Tl+ undergoes further exchange with H+. The adsorption mechanism is different for Tl(III), and involves either ion-exchange with Na+ at low Tl(III) concentration or co-precipitation in the form of Tl(OH)3 with TNTs at high Tl(III) concentration. XPS analysis indicates that the ion-exchange process does not change the basic skeleton [TiO6] of TNTs, whereas Tl(OH)3 precipitation increases the percentage composition of O within the surface hydroxyl groups. XRD analysis also confirms the formation of Tl(OH)3 on TNTs at high initial concentration of Tl(III). Coexisting Na+ and Ca2+ hardly inhibit adsorption, indicating good selectivity for thallium by TNTs. Furthermore, TNTs can be reused efficiently after HNO3 desorption and NaOH regeneration, making TNTs a promising material to remove thallium from wastewaters. This study also confirms that co-precipitation is another important adsorption mechanism for easily hydrolytic metals by TNTs.
Co-reporter:Wen Liu, Alistair G.L. Borthwick, Xuezhao Li, Jinren Ni
Microporous and Mesoporous Materials 2014 Volume 186() pp:168-175
Publication Date(Web):1 March 2014
DOI:10.1016/j.micromeso.2013.12.010
•Titanate transformed into anatase but not rutile via wet chemical reaction.•The transition process was an in situ rearrangement of unit structure [TiO6].•Modified TNTs showed both high photocatalytic and adsorptive performance.•Modified TNTs could simultaneously remove heavy metals and organic pollutants.Anatase-covered titanate nanotubes (TiNTs) with high photocatalytic and adsorptive performance characteristics were prepared through wet chemical reaction. TEM and XRD analysis revealed that the morphology and composition of the modified TiNTs were directly related to the ambient pH and temperature conditions of the reaction. Lower pH and higher temperature tended to enhance the transition from titanate to anatase; moreover, the transition process involved an in situ rearrangement of the primary structural unit [TiO6]. The photocatalytic performance of modified TiNTs depended on the amount of TiO2 transformed from titanate, whereas the adsorptive property was primarily determined by the tubular titanate structure. TiNTs modified under optimal conditions of pH 2 and 120 °C (TiNTs-120-2) not only exhibited high photocatalytic degradation rate for methyl orange (0.568 × 10−2 min−1), but also possessed a considerable capacity for adsorption of methylene blue (195.31 mg/g). Based on their excellent photocatalysis and adsorption properties, TiNTs-120-2 could simultaneously remove methyl orange, methylene blue, Pb2+, and phenol initially present in a compound pollution system, and the materials could be efficiently reused after a simple further treatment. In addition, TiNT-120-2 is well suited to sedimentation, and so has strong potential for application as an easily separable and recoverable material.
Co-reporter:Wen Liu, Weiling Sun, Yunfei Han, Muhammad Ahmad, Jinren Ni
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2014 Volume 452() pp:138-147
Publication Date(Web):20 June 2014
DOI:10.1016/j.colsurfa.2014.03.093
•TNMs with titanate phase showed large adsorption capacity for Cd(II) and Cu(II).•NaOH concentration affected morphology, crystal phase and composition of TNMs.•Ion-exchange between metal ion and Na+ was the main adsorption mechanism.•Na content of TNMs showed a good correlation with the adsorption capacity.•Na content was responsible for adsorption capacity of TNMs but not surface area.A series of titanate nanomaterials (TNMs) were synthesized via hydrothermal reaction under different NaOH concentrations (4–15 mol/L), and then used to remove Cu(II) and Cd(II) from aqueous solution. Transmission electron microscope (TEM) revealed that the morphology of the TNMs successively presented as nano-granules, nanoplates, nanotubes, nanosheets and nano-blocks with increasing NaOH concentration. X-ray diffraction (XRD) analysis indicated that the crystal phase of the TNMs changed as mixture of TiO2 and crystalline titanate, pure titanate and amorphous phase with increasing NaOH concentration. The TNMs which possessed titanate phase presented excellent adsorption performance, with maximum adsorption capacity of ca. 120 mg/g and 210 mg/g for Cu(II) and Cd(II) respectively. Moreover, the adsorption capacity showed a good correlation with the sodium content of TNMs, with R2 of 0.994 and 0.986 for Cu(II) and Cd(II) respectively. Therefore, the primary adsorption mechanism was ion-exchange between Na+ and metal ions, thus ONa groups were the main adsorption sites. Other mechanisms like ion-exchange with H+ and complexation by OH also could not be ignored. Furthermore, specific surface area and average pore diameter was found to have no definite relationship with adsorption capacity for the TNMs with titanate phase.
Co-reporter:Guanjun Niu, Wen Liu, Ting Wang, Jinren Ni
Journal of Colloid and Interface Science 2013 Volume 401() pp:133-140
Publication Date(Web):1 July 2013
DOI:10.1016/j.jcis.2013.03.037
•A two-step SN2 reaction performed for amino grafting on TNTs in pure water.•Five times larger of Cr(VI) adsorption onto TNTs-RNH2 than that of TNTs.•Good reuse of TNTs-RNH2 by simple desorption of Cr(VI) at pH 10.Unlike the complex reaction of grafting amino groups using harmful organic solvents, we proposed an environmental friendly method for effective amino grafting on titanate nanotubes (TNTs) with 2-Bromoethylamine hydrobromide (2-Bh) through a two-step SN2 reaction in pure water solution. The amino-modified titanate nanotubes (TNTs-RNH2) were characterized by Transmission electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. Under optimal conditions, the molar ratio of NaOH/2-Bh was 1.2 for step 1 and 1.3 for step 2 with corresponding reaction time of 12 h and 24 h, respectively. The adsorption isotherm of Cr(VI) onto TNTs-RNH2 well fits Langmuir model with maximal adsorption capacity of 69.1 mg/g, which is almost five times larger than that of fresh TNTs. The slight decrease in adsorption capacity with NO3- concentration was attributed to competition from ions, suppression of electric double layer and changes of Cr(VI) speciation. The wide adsorption pH range was due to much larger point of zero charge (8.2) and electrostatic attraction between positively charged TNTs-RNH2 and Cr(VI) with different speciations. The products could be well reused due to simple desorption at pH 10 with about 20% loss of the adsorption capacity after three recycles without any regeneration treatment.Graphical abstract
Co-reporter:Wen Liu, Weiling Sun, Alistair G.L. Borthwick, Jinren Ni
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2013 Volume 434() pp:319-328
Publication Date(Web):5 October 2013
DOI:10.1016/j.colsurfa.2013.05.010
•Aggregation highly related to microstructure and composition of the nanomaterials.•Micro-heterogeneity of TNs–TiO2 led to smaller size but higher sedimentation rate.•Electrical reversal for charge of TNs and TNs–TiO2 occurred when increasing Ca2+.•HA caused aggregation energy barrier while Ca2+ acted as ion bridge when co-existed.Aggregation and sedimentation are of significant importance to the safe applications of nanomaterials. In this study, aggregation and sedimentation of three homologous nanomaterials, titanium dioxide (TiO2), titanate nanotubes (TNs), and titanate nanotubes–TiO2 (TNs–TiO2) were systematically studied under various aqueous conditions. The influences of pH, ionic strength (Na+ and Ca2+) and natural organic matter (humic acid, HA) on aggregate size, zeta potential and sedimentation rate were totally investigated. It was found that maximum aggregation invariably occurred at pH close to point of zero charge. However, the three nanomaterials underwent different aggregation processes, even though aggregation was always greatly enhanced with increasing ionic strength in either Na+ or Ca2+ solutions. In Ca2+ solutions, the aggregate size of TiO2 tended to increase solely with increasing ionic strength, while the size of TNs and TNs–TiO2 increased initially before decreasing, due to the surface charge changing from negative to positive at high ionic strengths. The aggregation energy barrier was enhanced considerably by HA, thus inhibiting aggregation. TNs and TNs–TiO2 exhibited a greater energy barrier transition than TiO2 due to their higher adsorption capacity for HA, and moreover, the co-existence of Ca2+ also exhibited ion bridge effects on aggregation. Different microstructure and chemical composition of the nanomaterials resulted in different aggregation and sedimentation behaviors, and the micro-heterogeneity of TNs–TiO2 led to smaller size but higher sedimentation rate than TNs.
Co-reporter:Xiuping Zhu, Jinren Ni
Electrochimica Acta 2011 Volume 56(Issue 28) pp:10371-10377
Publication Date(Web):1 December 2011
DOI:10.1016/j.electacta.2011.05.062
Boron-doped diamond (BDD) electrodes are promising anode materials in electrochemical treatment of wastewaters containing bio-refractory organic compounds due to their strong oxidation capability and remarkable corrosion stability. In order to further improve the performance of BDD anode system, electrochemical degradation of p-nitrophenol were initially investigated at the BDD anode in the presence of zero-valent iron (ZVI). The results showed that under acidic condition, the performance of BDD anode system containing zero-valent iron (BDD-ZVI system) could be improved with the joint actions of electrochemical oxidation at the BDD anode (39.1%), Fenton's reaction (28.5%), oxidation–reduction at zero-valent iron (17.8%) and coagulation of iron hydroxides (14.6%). Moreover, it was found that under alkaline condition the performance of BDD-ZVI system was significantly enhanced, mainly due to the accelerated release of Fe(II) ions from ZVI and the enhanced oxidation of Fe(II) ions. The dissolved oxygen concentration was significantly reduced by reduction at the cathode, and consequently zero-valent iron corroded to Fe(II) ions in anaerobic highly alkaline environments. Furthermore, the oxidation of released Fe(II) ions to Fe(III) ions and high-valent iron species (e.g., FeO2+, FeO42−) was enhanced by direct electrochemical oxidation at BDD anode.
Co-reporter:Hongna Li, Xiuping Zhu, Jinren Ni
Electrochimica Acta 2011 Volume 56(Issue 27) pp:9789-9796
Publication Date(Web):30 November 2011
DOI:10.1016/j.electacta.2011.08.053
Electrochemical process in chloride-free electrolytes was proved to be powerful in disinfection due to the strong oxidants produced in the electrolysis and no formation of disinfection byproducts (DBPs). In this study, disinfection experiments were conducted by electrochemical treatment compared with ordinary and advanced methods (ozonation, chlorination and monochloramination), with Escherichia coli (E. coli) K-12, Staphylococcus aureus (S. aureus) A106, Bacillus subtilis (BST) and an isolated Bacillus as the representative microorganisms. Firstly, factor tests were performed on E. coli to obtain the optimal conditions of the four disinfection procedures. At their respective optimal condition, CT (concentration of disinfectant × contact time) value of a 4-log E. coli inactivation was 33.5, 1440, 1575, 1674 mg min L−1 for electrochemical process, ozonation, chlorination and monochloramination, respectively. It was demonstrated that the disinfection availability was in the following order: electrochemical process > ozonation > chlorination > monochloramination, which could be attributed to the hydroxyl radical generated in the electrolysis, with strong oxidizing ability and non-selectivity compared with the other three disinfectants. Moreover, the disinfection efficacy of the four disinfection procedures was compared for four different bacteria. It was found that the disinfection efficacy was similar for the selected four bacteria in electrochemical process, while in the other three treatments inactivation of the two Bacillus was much slower than E. coli and S. aureus. As a result, the non-selectivity of electrochemical disinfection with BDD anode to different kinds of microorganisms was further proved, which was primarily controlled by the hydroxyl radicals existed in the free state. For each bacterium, the order of disinfection availability of the four processes was consistent. Finally, scanning electron microscopy (SEM) was implemented to observe the cell morphology. It was shown that cell surface damage was more obvious in electrochemical system with strong oxidants compared with that after ozone treatment, while the integrity of cells were not affected in weak oxidizing chlorine and monochloramine.Highlights► Electrochemical, O3, NaClO and NH2Cl were compared at respective optimal condition. ► Disinfection efficacy was similar for different bacteria in electrolysis. ► Harsh Bacillus was inactivated more difficult in O3, NaClO and NH2Cl system. ► Efficient disinfection of electrolysis was attributed to nonselectivity of •OH. ► Cell surface damage was more obvious in electrochemical process than the others.
Co-reporter:Xiuping Zhu, Jinren Ni, Junjun Wei, Pan Chen
Electrochimica Acta 2011 Volume 56(Issue 25) pp:9439-9447
Publication Date(Web):30 October 2011
DOI:10.1016/j.electacta.2011.08.032
Scale-up of boron-doped diamond (BDD) anode system is critical to the practical application of electrochemical oxidation in bio-refractory organic wastewater treatment. In this study, the scale-up of BDD anode system was investigated on batch-mode electrochemical oxidation of phenol simulated wastewater. It was demonstrated that BDD anode system was successfully scaled up by 121 times without performance deterioration based on the COD and specific energy consumption (Esp) models in bath mode. The COD removal rate and Esp for the scaled-up BDD anode system through enlarging the total anode area while keeping similar configuration, remained at the similar level as those before being scaled up, under the same area/volume value, current density, retention time and wastewater characteristics. The COD and Esp models used to describe the smaller BDD anode system satisfactorily predicted the performance of the scaled-up BDD anode system. Under the suitable operating conditions, the COD of phenol simulated wastewater was reduced from 540 mg l−1 to 130 mg l−1 within 3 h with an Esp of only 34.76 kWh m−3 in the scaled-up BDD anode system. These results demonstrate that BDD anode system is very promising in practical bio-refractory organic wastewater treatment.
Co-reporter:Xiuping Zhu, Jinren Ni, Xuan Xing, Hongna Li, Yi Jiang
Electrochimica Acta 2011 Volume 56(Issue 3) pp:1270-1274
Publication Date(Web):1 January 2011
DOI:10.1016/j.electacta.2010.10.073
In order to enhance the performance of boron-doped diamond (BDD) anode system, activated carbon is added into BDD anode system to construct a three-dimensional electrode system. The degradation rates of p-nitrophenol and COD were significantly improved by 2–7 times compared to two-dimensional BDD anode system. More importantly, the synergy between electrochemical oxidation and activated carbon adsorption was observed. Investigations revealed that the synergy was not only resulted from direct electrochemical oxidation at activated carbon, but also from electro-catalysis of activated carbon to indirect electrochemical oxidation mediated by hydroxyl radicals. Although oxygen was reduced to hydrogen peroxide at the activated carbon surface, but the oxidation of hydrogen peroxide was not the main reason for the improvement of three-dimensional electrode system due to its relative weak oxidation capacity. Instead, the decomposition of hydrogen peroxide to hydroxyl radicals at catalysis of activated carbon played an important role on the enhancement of three-dimensional electrode system.
Co-reporter:Lin Xiong, Weiling Sun, Ye Yang, Cheng Chen, Jinren Ni
Journal of Colloid and Interface Science 2011 Volume 356(Issue 1) pp:211-216
Publication Date(Web):1 April 2011
DOI:10.1016/j.jcis.2010.12.059
Titanate nanotubes were synthesized with hydrothermal reaction using TiO2 and NaOH as the precursors and subsequent calcination at 400 °C for 2 h. The products were characterized with SEM and XRD. Adsorption and photocatalysis of methylene blue over titanate nanotubes and TiO2 were investigated. The results indicated that titanate nanotubes exhibited a better photocatalytic degradation of methylene blue in a simultaneous adsorption and photodegradation system than that in equilibrium adsorption followed by a photodegradation system, whereas TiO2 showed no significant differences in photocatalytic activity in the two systems. The methylene blue overall removal efficiency over TNTs in the first system even exceeded that over TiO2. The different catalytic performances of titanate nanotubes in the two systems were tentatively attributed to different effects of adsorption of methylene blue, i.e., the promoting effect in the former and the inhibition effect in the latter. Decantation experiments showed that the titanate nanotube photocatalyst could be easily separated from the reaction medium by sedimentation. Thus titanate nanotubes with high sedimentation rates and concurrent adsorption represent a new catalyst system with a strong potential for commercial applications.Graphical abstractTitanate nanotubes (TNTs) exhibited a better photocatalytic degradation of methylene blue in a simultaneous adsorption and photodegradation system (A + P) than that in equilibrium adsorption followed by photodegradation system (A/P)..Research highlights► We study the effect of adsorption on photocatalysis of methylene blue over titanate nanotubes. ► Titanate nanotubes show higher photodegradation of methylene blue with lower adsorption. ► Too high adsorption may inhibit the photocatalytic activity of titanate nanotubes. ► Titanate nanotubes exhibit better sedimentation properties than TiO2.
Co-reporter:Chen Zhong;Baogang Zhang;Lingcai Kong;An Xue
Journal of Chemical Technology and Biotechnology 2011 Volume 86( Issue 3) pp:406-413
Publication Date(Web):
DOI:10.1002/jctb.2531
Abstract
BACKGROUND: The conventional treatment of molasses wastewater has many disadvantages including intensive energy requirements, excessive chemicals consumption and large quantities of waste generation. The microbial fuel cell (MFC) is a promising technology for power generation along with wastewater treatment. However, low power output and high construction costs limit the scale-up and field implementation of MFCs. In this study, a novel anaerobic baffled stacking microbial fuel cell (ABSMFC) composed of four units was constructed and used to treat molasses wastewater.
RESULTS: The ABSMFC was operated at three different organic loading rates (OLRs) and the highest average power density of 115.5 ± 2.7 mW m−2 was achieved for the four units at an OLR of 3.20 kg COD m−3 d−1. Accordingly, 50–70% of total COD removal efficiency was accomplished. Power generation was further improved in terms of voltage or current by connecting units in series or parallel. The low voltage loss (8.1%) during series connection resulted from low parasitic current of adjacent units.
CONCLUSION: The ABSMFC is effective for molasses wastewater treatment. It can promote current or voltage output and minimize energy loss during series connection. This is a promising scalable architecture and can be combined with other existing wastewater treatment technologies. Copyright © 2010 Society of Chemical Industry
Co-reporter:Hongna Li, Xiuping Zhu, Jinren Ni
Electrochimica Acta 2010 Volume 56(Issue 1) pp:448-453
Publication Date(Web):15 December 2010
DOI:10.1016/j.electacta.2010.08.055
Electrochemical disinfection in chloride-free electrolyte has attracted more and more attention due to advantages of no production of disinfection byproducts (DBPs), and boron-doped diamond (BDD) anode with several unique properties has shown great potential in this field. In this study, inactivation of Escherichia coli (E. coli) was investigated in Na2SO4 electrolyte using BDD anode. Firstly, disinfection tests were carried on at different current density. The inactivation rate of E. coli and also the concentration of hydroxyl radical (OH) increased with the current density, which indicated the major role of OH in the disinfection process. At 20 mA cm−2 the energy consumption was the lowest to reach an equal inactivation. Moreover, it was found that inactivation rate of E. coli rose with the increasing Na2SO4 concentration and they were inactivated more faster in Na2SO4 than in NaH2PO4 or NaNO3 electrolyte even in the presence of OH scavenger, which could be attributed to the oxidants produced in the electrolysis of SO42−, such as peroxodisulfate (S2O82−). And the role of S2O82− was proved in the disinfection experiments. These results demonstrated that, besides hydroxyl radical and its consecutive products, oxidants produced in SO42− electrolysis at BDD anode played a role in electrochemical disinfection in Na2SO4 electrolyte.
Co-reporter:Xiuping Zhu, Jinren Ni, Hongna Li, Yi Jiang, Xuan Xing, Alistair G.L. Borthwick
Electrochimica Acta 2010 Volume 55(Issue 20) pp:5569-5575
Publication Date(Web):1 August 2010
DOI:10.1016/j.electacta.2010.04.072
The effects of low-frequency (40 kHz) ultrasound are investigated with regard to the effectiveness and mechanisms of electrochemical oxidation of p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) at BDD (boron-doped diamond) and PbO2 anodes. Although ultrasound improved the disappearance rates of p-substituted phenols at both the BDD and PbO2 anodes, the degree of enhancement varied according to the type of p-substituted phenol and type of anode under consideration. At the BDD anode, the %Increase values were in the range 73–83% for p-substituted phenol disappearance and in the range 60–70% for COD removal. However, at the PbO2 anode, the corresponding %Increase values were in the range 50–70% for disappearance of p-substituted phenols and only 5–25% for COD removal, much lower values than obtained at the BDD anode. Further investigations on the influence of ultrasound on the electrochemical oxidation mechanisms at BDD and PbO2 anodes revealed that the different increase extent were due to the specialized electrochemical oxidation mechanisms at these two anodes. The hydroxyl radicals were mainly free at the BDD electrodes with a larger reaction zone, but adsorbed at the PbO2 electrodes with a smaller reaction zone. Therefore, the enhancement due to ultrasound was greater at the BDD anode than at the PbO2 anode.
Co-reporter:Bin Zhao, Huazhang Zhao, Jinren Ni
Separation and Purification Technology 2010 Volume 72(Issue 3) pp:250-255
Publication Date(Web):11 May 2010
DOI:10.1016/j.seppur.2010.02.013
Donnan dialysis has been proven to be effective in removing ionic contaminants from water. In this paper, the effects of nitrate, sulfate, phosphate, bicarbonate, and silicate on the arsenate (As(V)) removal by Donnan dialysis have been systematically studied compared to that of chloride. In order to interpret the different interaction phenomena and identify potential underlying mechanisms, both the simultaneous transfer of these accompanying components and their influence on the ion exchange reaction between the arsenate ions and the anion exchange membrane have also been investigated. In the presence of nitrate, sulfate, or phosphate, their competition with As(V) for the functional groups in the membrane dominated the average flux of As(V) through the membrane within the first 2 h of the batch dialytic process. However, the overall removal of As(V) mainly depended on the dialytic kinetics of these accompanying anions when the batch dialysis lasted as long as 24 h. The presence of bicarbonate increased the solution pH and the fraction of HAsO42− ions; as a result, the transfer of As(V) was accelerated. At neutral pH, the undissociated silicate exhibited negligible inhibition on the As(V) removal. The arsenic concentration remaining in feed solutions at 24 h was less than 50 μg L−1 in all tests except in the presence of phosphate. The current results indicate that Donnan dialysis successfully removes the arsenate ions from groundwater containing various accompanying components. This feature makes it an attractive alternative for the As(V) removal point-of-use (POU) technologies in rural areas.
Co-reporter:Yuling Zhu;Wen Huang
Bioprocess and Biosystems Engineering 2010 Volume 33( Issue 5) pp:647-655
Publication Date(Web):2010 June
DOI:10.1007/s00449-009-0390-1
Based on the response surface methodology, an effective microbial system for diosgenin production from enzymatic pretreated Dioscorea zingiberensis tubers with Trichoderma reesei was studied. The fermentation medium was optimized with central composite design (35) depended on Plackett–Burmann design which identified significant impacts of peptone, K2HPO4 and Tween 80 on diosgenin yield. The effects of different fermentation conditions on diosgenin production were also studied. Four parameters, i.e. incubation period, temperature, initial pH and substrate concentration were optimized using 45 central composite design. The highest diosgenin yield of 90.57% was achieved with 2.67% (w/v) of peptone, 0.29% (w/v) of K2HPO4, 0.73% (w/v) of Tween 80 and 9.77% (w/v) of substrate, under the condition of pH 5.8, temperature 30 °C. The idealized incubation time was 6.5 days. After optimization, the product yield increased by 33.70% as compared to 67.74 ± 1.54% of diosgenin yield in not optimized condition. Scale-up fermentation was carried out in a 5.0 l bioreactor, maximum diosgenin yield of 90.17 ± 3.12% was obtained at an aeration of 0.80 vvm and an agitation rate of 300 rpm. The proposed microbial system is clean and effective for diosgenin production and thus more environmentally acceptable than the traditional acid hydrolysis.
Co-reporter:Wei Liu;Wen Huang;WeiLing Sun;YuLing Zhu
World Journal of Microbiology and Biotechnology 2010 Volume 26( Issue 7) pp:1171-1180
Publication Date(Web):2010 July
DOI:10.1007/s11274-009-0285-y
A commercial cellulase was first assessed to be effective in hydrolyzing glycosyl at the C-3 and C-26 positions in steroidal saponins from yellow ginger (Dioscorea zingiberensis C. H. Wright) to diosgenin, a very important chemical in the pharmaceutical industry. The effect of different parameters on enzyme hydrolysis was further investigated by systematically varying them. The highest yield was achieved when the hydrolysis ran at 55°C and pH 5.0 with an enzyme to substrate ratio of 15 × 103 U/g. The biotransformed products identified using TLC and HPLC confirmed that the cellulase was capable of releasing diosgenin from steroidal saponins. Moreover, the biotransformation process was explored by LC-MS and LC-MS/MS analysis. Enzymatic hydrolysis together with 40 % of the original sulphuric acid used increased the diosgenin yield by 15.4 ± 2.7% than traditional method. Therefore, the commercial cellulase may serve as a promising tool for industrial diosgenin production and for further use in saponin modification.
Co-reporter:Bao-Gang Zhang;Shun-Gui Zhou;Hua-Zhang Zhao
Bioprocess and Biosystems Engineering 2010 Volume 33( Issue 2) pp:187-194
Publication Date(Web):2010 February
DOI:10.1007/s00449-009-0312-2
Sulfide and vanadium (V) are pollutants commonly found in wastewaters. A novel approach has been investigated using microbial fuel cell (MFC) technologies by employing sulfide and V(V) as electron donor and acceptor, respectively. This results in oxidizing sulfide and deoxidizing V(V) simultaneously. A series of operating parameters as initial concentration, conductivity, pH, external resistance were carefully examined. The results showed that these factors greatly affected the performance of the MFCs. The average removal rates of about 82.2 and 26.1% were achieved within 72 h operation for sulfide and V(V), respectively, which were accompanied by the maximum power density of about 614.1 mW m−2 under all tested conditions. The products generated during MFC operation could be deposited, resulting in removing sulfide and V(V) from wastewaters thoroughly.
Co-reporter:Yu-Ling Zhu;Wen Huang;Jin-Ren Ni;Wei Liu
Applied Microbiology and Biotechnology 2010 Volume 85( Issue 5) pp:1409-1416
Publication Date(Web):2010 February
DOI:10.1007/s00253-009-2200-8
In order to develop a clean and effective approach for producing the valuable drug diosgenin from Dioscorea zingiberensis tubers, two successive processes, enzymatic saccharification and microbial transformation, were used. With enzymatic saccharification, 98.0% of starch was excluded from the raw herb, releasing saponins from the network structure of starch. Subsequently, the treated tubers were fermented with Trichoderma reesei under optimal conditions for 156 h. During microbial transformation, glycosidic bonds, which link β-d-glucose or α-l-rhamnose with aglycone at the C-3 position in saponins, were broken down effectively to give a diosgenin yield of 90.6 ± 2.45%, 42.4% higher than that obtained from bioconversion of raw tubers directly. Scaled up fermentation was conducted in a 5.0-l bioreactor and gave a diosgenin yield of 91.2 ± 3.21%. This is the first report on the preparation of diosgenin from herbs through microbial transformation as well as utilizing other available components in the raw material, providing an environmentally friendly alternative to diosgenin production.
Co-reporter:Xiuping Zhu, Jinren Ni
Electrochemistry Communications 2009 Volume 11(Issue 2) pp:274-277
Publication Date(Web):February 2009
DOI:10.1016/j.elecom.2008.11.023
This study initially demonstrates that the electricity generated by a microbial fuel cell (MFC) can be used to in situ generate H2O2 at a carbon felt cathode. In the presence of scrap iron, H2O2 further reacts with Fe2+ to produce hydroxyl radicals. Attributed to the oxidation of H2O2 and hydroxyl radicals, and the oxidation–reduction of scrap iron, p-nitrophenol was significantly removed in the cathode chamber of the MFC. The p-nitrophenol was completely degraded after 12 h, and about 85% of TOC was removed after 96 h. Simultaneously, a maximum power density (143 mW m−2) was generated by the MFC. It is concluded that a MFC not only can generate electricity and degrade biodegradable compounds, but also remove bio-refractory pollutants.
Co-reporter:Baogang Zhang;Huazhang Zhao;Chunhong Shi;Shungui Zhou
Journal of Chemical Technology and Biotechnology 2009 Volume 84( Issue 12) pp:1780-1786
Publication Date(Web):
DOI:10.1002/jctb.2244
Abstract
BACKGROUND: Sulfide-containing wastewater (also containing organics) and vanadium(V)-containing wastewater exist widely and can be treated in microbial fuel cells (MFCs) based on their chemical conditions. A novel process has been investigated using MFC technologies by employing sulfide, organics and V(V) as electron donors and acceptor, respectively.
RESULTS: Electrons produced by oxidation of sulfide and organics in the anode compartment were transferred to the anode surface, then flowed to the cathode through an external circuit, where they were consumed to reduce V(V). Sulfide and total organics removal approached 84.7 ± 2.8% and 20.7 ± 2.1%, with a V(V) reduction rate of 25.3 ± 1.1%. The maximum power output obtained was 572.4 ± 18.2 mW m−2. The effects of the microbes on electricity generation as well as the products of sulfide oxidation and V(V) reduction were also evaluated and analyzed.
CONCLUSION: This process achieves both sulfide and V(V) removal with electricity generation simultaneously, providing an economical route for treating these kinds of wastewaters. Copyright © 2009 Society of Chemical Industry
Co-reporter:Xiaojia He;Shaozu Wu;Dongkang Fu
Journal of Chemical Technology and Biotechnology 2009 Volume 84( Issue 3) pp:427-434
Publication Date(Web):
DOI:10.1002/jctb.2057
Abstract
BACKGROUND: This paper describes the reuse of paper sludge, an industrial solid waste, for the preparation of sodium carboxymethyl cellulose (CMC). The process includes pretreatment, basification and etherification.
RESULTS: The optimal pretreatment condition involved the addition of 6.7% hydrochloric acid to the paper sludge for 30 min at 70 °C. The order of factors influencing the effect of reaction was: etherification temperature > sodium hydroxide dose > basification temperature > etherification time > sodium chloroacetate dose. The optimal preparation condition of CMC was: mpapersludge: msodiumhydroxide: msodiumchloroacetate = 0.9:0.8:1.15; basification at 40 °C; etherification at 60 °C for 1 h. Under these conditions, certified CMC with viscosity less than 20 mPa· s, DS more than 0.50 and purity more than 90% was produced. The results of Fourier transform infrared (FTIR) and X-ray diffraction (XRD) spectra analyses indicated that the product has characteristics of high degree of substitution (DS) and low crystallinity. The coated paper using CMC prepared from paper sludge as a water retention agent can meet the quality standards of GB/T 10335.1-2005.
CONCLUSION: Preparation of CMC from paper sludge can be considered a feasible alternative, generating value-added product and contributing to solving environmental problems resulting from paper sludge. Copyright © 2008 Society of Chemical Industry
Co-reporter:Xiuping Zhu, Meiping Tong, Shaoyuan Shi, Huazhang Zhao and Jinren Ni
Environmental Science & Technology 2008 Volume 42(Issue 13) pp:4914-4920
Publication Date(Web):May 21, 2008
DOI:10.1021/es800298p
Electrochemical oxidation of p-nitrophenol was examined using different anodic materials, including Ti/boron-doped diamond (BDD), Ti/SnO2−Sb/PbO2, and Ti/SnO2−Sb anodes. The results demonstrated that Ti/BDD anodes had a much stronger mineralization performance than the other two anodes. Furthermore, it was found that hydroxyl radicals could mainly exist as free hydroxyl radicals at BDD anodes, which could react with organic compounds effectively. This implied that the dominant mechanism for a much higher mineralization capacity of BDD anodes would be attributed to the existence of free hydroxyl radicals in the BDD anode cell rather than adsorbed hydroxyl radicals on the BDD anode. To further corroborate this hypothesis, electrochemical oxidation of p-substituted phenols (p-nitrophenol, p-hydroxybenzaldehyde, phenol, p-cresol, and p-methoxyphenol) was examined at the Ti/BDD, Ti/SnO2−Sb/PbO2, and Ti/SnO2−Sb anodes, respectively. The study revealed that for Ti/BDD electrodes, the degradation rate of p-substituted phenols (k) increased with the increase of Hammett’s constant (σ), which confirmed the dominance of free hydroxyl radicals at BDD anodes and its effective reaction with organics therein. For Ti/SnO2−Sb/PbO2 electrodes, the degradation rate of p-substituted phenols (k) increased with the increase of initial surface concentration Γ (representing the adsorption capacity of phenols to electrode surface), which indicated that organic compounds mainly reacted with adsorbed hydroxyl radicals at PbO2 anodes. For Ti/SnO2−Sb electrodes, however, k increased with the increase of the integrated parameter S (representing the effects of both σ and Γ), which implied that organic compounds reacted with both adsorbed hydroxyl radicals and free hydroxyl radicals at SnO2 anodes.
Co-reporter:Li Fan, Shunni Zhu, Dongqi Liu, Jinren Ni
Dyes and Pigments 2008 Volume 78(Issue 1) pp:34-38
Publication Date(Web):2008
DOI:10.1016/j.dyepig.2007.10.004
Sphingomonas herbicidovorans FL decolorized 1-amino-4-bromoanthraquinone-2-sulfonic acid and grew with it as the sole carbon source. The maximum rate of decolorization was achieved during the exponential growth phase of the bacterial strain. Of the total organic carbon ∼52% could be removed, coupled with the partial release of ammonia, bromine and sulfate. Analysis of metabolites using gas chromatography–mass spectrometry and liquid chromatography–mass spectrometry showed that phthalic acid was the metabolic intermediate and which may serve as the growth substrate for the bacteria. The end product was either 2-amino-3-hydroxy-5-bromobenzenesulfonic acid or 2-amino-4-hydroxy-5-bromobenzenesulfonic acid. A possible metabolic pathway is proposed.
Co-reporter:Lina Xu, Huazhang Zhao, Shaoyuan Shi, Guangzhi Zhang, Jinren Ni
Dyes and Pigments 2008 Volume 77(Issue 1) pp:158-164
Publication Date(Web):2008
DOI:10.1016/j.dyepig.2007.04.004
A simulated wastewater containing the monoazo dye C.I. Acid Orange 7 was electrolytically treated using a three-dimensional electrode reactor equipped with granular activated carbon as particle electrode. The activated carbon fiber cathode was more effective than either a graphite or a stainless steel cathode due to its larger surface area which was beneficial to the electrogeneration of H2O2. Under the reaction conditions of 20 V and 3.0 g L−1 Na2SO4 at pH 3.0, decrease in the COD of up to 80%, and in the TOC by up to 72% were achieved and almost the complete decolorization of the dye was secured after 180 min electrolysis. Furthermore, decay of the dye followed a pseudo-first-order reaction in the first 60 min treatment. The three-dimensional electrode system generated more hydroxyl radicals than a two-dimensional system due to the formation of microelectrodes under applied high potential.
Co-reporter:Shunni Zhu
Journal of Chemical Technology and Biotechnology 2008 Volume 83( Issue 3) pp:317-324
Publication Date(Web):
DOI:10.1002/jctb.1812
Abstract
BACKGROUND: Coking wastewater is a major pollutant, produced in large quantities in many countries worldwide. This study investigates the performance of a combined system for treating coking wastewater. The system is based on an upflow blanket filter (UBF) with a biological aerated filter (BAF). Efficiency is assessed according to organic pollutants and nitrogen removal.
RESULTS: It was found that hydraulic retention time (HRT) had a greater influence on the removal efficiency of NH3-N than chemical oxygen demand (COD). The BAF facilitated simultaneous carbonaceous removal and nitrification, depending on the reactor height. The system removed 81.5% of COD and 96.4% of NH3-N when the total HRT was 46.7 h (15.4 h for UBF and 31.3 h for BAF). Gas chromatography/mass spectrometry analysis indicated that the main components of the coking wastewater were phenols and nitrogenous heterocyclic compounds. Certain refractory compounds decomposed in the anaerobic section, resulting in the production of intermediates. Although most organics present in the influent were absent from the final effluent, a few residual contaminants could not be fully eliminated by the system.
CONCLUSION: The experimental results show that the present system is feasible for the treatment of coking wastewater. Copyright © 2007 Society of Chemical Industry
Co-reporter:Ming Chang;Shun-Gui Zhou;Na Lu;Jin-Ren Ni
World Journal of Microbiology and Biotechnology 2008 Volume 24( Issue 4) pp:441-447
Publication Date(Web):2008 April
DOI:10.1007/s11274-007-9491-7
Production of Bacillus thuringiensis (Bt) based bioinsecticide was studied by using starch processing wastewater (SPW) as a raw material. Results indicated that the nutrients contained in SPW were sufficient for growth, sporulation and δ-endotoxin production of Bacillusthuringiensis subsp. kurstaki (Btk). The final cell counts and spore counts achieved in SPW medium were 72% and 107% respectively higher than those in the soybean meal based commercial medium. Higher δ-endotoxin yield of 2.67 mg mL−1 and higher entomotoxicity of 1,050 IU μL−1 were also obtained in SPW medium as compared with the commercial medium at the end of fermentation. The morphological observations also revealed that the fermentation cycle of Btk could be shortened in this new medium. This process provides solutions for safe SPW disposal and production of high potency and low cost bioinsecticide.
Co-reporter:Lei Yao;ZhengFang Ye;ZhongYou Wang
Science Bulletin 2008 Volume 53( Issue 6) pp:948-953
Publication Date(Web):2008 March
DOI:10.1007/s11434-008-0103-1
Experimental studies were conducted on the feasibility of aerobic granular biomass as a novel type of biosorbent for Pb2+ removal. The results show that the initial pH, Pb2+ concentration (C0) and biomass concentration (X0) affected the biosorption process significantly. Both the Freundlich and Langmuir isotherm models describe the biosorption process accurately, with correlation coefficients of 0.932 and 0.959 respectively. The Pb2+ biosorption kinetics is interpreted as having two stages, with the second stage described reasonably well by a Lagergren pseudo-second order model. Moreover, the surface change of granular biomass after the Pb2+ biosorption process appears to be caused by ion exchange and metal chelation according to the analysis results of Environmental Scanning Electron Microscopy (ESEM) and Energy Dispersive X-ray Spectroscopy (EDX).
Co-reporter:Dongkang Fu, Shaozu Wu, Xiaojia He, Jinren Ni
Colloids and Surfaces A: Physicochemical and Engineering Aspects 2008 Volume 326(Issue 3) pp:122-128
Publication Date(Web):1 September 2008
DOI:10.1016/j.colsurfa.2008.05.021
Two types of dispersants for calcium carbonate were synthesized by condensation polymerization. One was the acrylic homopolymer (Dispersant-A), and the other was copolymer of acrylic acid with unsaturated esters (Dispersant-B). For the former, the optimal synthesizing parameters were determined: ammonium persulfate of 4.0% as the initiator; isopropanol/water of 1.25 as the chain-transfer, and sodium hydroxide as the neutralization agent. For the latter, the proper weight ratio of unsaturated ester/acrylic acid was found to be 1:4. Comparison was made between the dispersants and the popular products such as Acumer9400 synthesized in US, SP40M produced in Taipei, and SN5040 from Japan. Dispersion experiments for 3000-mesh calcium carbonate showed that Dispersant-B had the highest dispersing capability of the four dispersants. The dispersing capability of Dispersant-A was close to that of Acumer9400, but higher than that of SP40M at the dosage range of 1.2–2.0‰. Dispersant-B and SN5040 were the suitable dispersants for the dispersion of nanometer calcium carbonate. The grinding experiment of 325-mesh calcium carbonate revealed a logarithmic relation between the weight percentage of fine particles and the cumulative specific energy input. Moreover, a power-low function was well established between the median size and the cumulative specific energy input.
Co-reporter:Jiangtao Kong, Shaoyuan Shi, Lingcai Kong, Xiuping Zhu, Jinren Ni
Electrochimica Acta 2007 Volume 53(Issue 4) pp:2048-2054
Publication Date(Web):31 December 2007
DOI:10.1016/j.electacta.2007.09.003
PbO2 electrodes doped with rare earth oxides (Re-PbO2), including Er2O3, Gd2O3, La2O3 and CeO2, were prepared by anodic codeposition in order to investigate the effect of rare earth oxide dopants on the properties of PbO2 electrodes. The physicochemical properties of the Re-PbO2 electrodes were analyzed by spectral methods and electrochemical measurements. The surface morphology of the Re-PbO2 electrodes held the characteristics of the dopants and the crystal grain of PbO2. The crystal structure of the PbO2 electrodes was also influenced by doping with different rare earth oxides. The presence of Er2O3 and La2O3 in the PbO2 films could enhance the direct anodic oxidation, which was helpful to mineralize 4-chlorophenol. The 4-chlorophenol decay on the Re-PbO2 electrodes was analyzed and good fitting was found using the relation for the pseudo-first order reaction. Of the electrodes examined, the Er-PbO2 electrode exhibited the best performance for the degradation of 4-chlorophenol. The removal rates of COD and 4-chlorophenol during the 9 h electrolysis at a current density of 20 mA cm−2 were 80.7 and 100%, respectively, with the current efficiency being 16.0–10.1%.
Co-reporter:Peng-Peng Hao, Jin-Ren Ni, Wei-Ling Sun, Wen Huang
Food Chemistry 2007 Volume 105(Issue 4) pp:1732-1737
Publication Date(Web):2007
DOI:10.1016/j.foodchem.2007.04.058
A simple, sensitive and accurate analytical method for quantification of tertiary butylhydroquinone (TBHQ) in edible vegetable oil was established by liquid chromatography/ion trap mass spectrometry (LC/ITMS). After extraction, 5 μl of the extracts was directly injected into LC/ITMS for TBHQ determination. Ethanol was selected as the extraction solvent. The optimized fragmentation amplitude was 1.70 V and electrospray ionization (ESI) was more suitable than atmospheric pressure chemical ionization (APCI) for TBHQ detection. The calibration curve showed good linearity (R2 = 0.9990) and recoveries from spiked samples ranged from 81.9% to 110.5%. Relative standard deviations of intra-day and inter-day were in the ranges 2.5–5.7% and 3.9–13.8%, respectively. The procedure allows the detection of 0.3 mg/kg TBHQ in edible vegetable oil. Typical edible vegetable oils in the market were detected for TBHQ by the proposed method. As results, TBHQ was detected in blend oil, soybean salad oil and camellia oil samples.
Co-reporter:Xue-Ying Mao, Jin-Ren Ni, Wei-Ling Sun, Peng-Peng Hao, Li Fan
Food Chemistry 2007 Volume 103(Issue 4) pp:1282-1287
Publication Date(Web):2007
DOI:10.1016/j.foodchem.2006.10.041
Yak (Bos grunniens) milk casein derived from Qula, a kind of acid curd cheese from northwestern China, was hydrolysed with alcalase. The hydrolysates collected at different hydrolysis times (0 min, 60 min, 120 min, 180 min, 240 min, 300 min, 360 min) were assayed for the inhibitory activity of angiotensin-I-converting enzyme (ACE), and the one obtained at 240 min hydrolysis showed the highest ACE inhibitory activity. The active hydrolysate was further consecutively separated by ultrafiltration with 10 kDa and then with 6 kDa molecular weight cut-off membranes into different parts, and the 6 kDa permeate showed the highest ACE-inhibiting activity. This active fraction was further purified to yield two novel ACE-inhibiting peptides, whose amino acid sequences were Pro–Pro–Glu–Ile–Asn (PPEIN)(κ-CN; f156–160) and Pro–Leu–Pro–Leu–Leu (PLPLL) (β-CN; f136–140), respectively. The molecular weight and IC50 value of the peptides were 550 Da and 566.4 Da, and 0.29 ± 0.01 mg/ml and 0.25 ± 0.01 mg/ml, respectively.
Co-reporter:Jun Zhu, Huazhang Zhao, Jinren Ni
Separation and Purification Technology 2007 Volume 56(Issue 2) pp:184-191
Publication Date(Web):15 August 2007
DOI:10.1016/j.seppur.2007.01.030
Electrocoagulation (EC) is an effective process to remove fluoride from water, but few of scientific literatures explore its inside mechanism. A new approach was used in this study to investigate fluoride distribution in the EC defluoridation process, which divided the fluoride into three parts: remained in water, removed by electrodes, and adsorbed on hydroxide aluminum flocs. The fluoride distribution was investigated in terms of several critical parameters such as pH, charge loading, current density and initial fluoride concentration. The experimental results showed that the removal by electrodes was primarily responsible for the high defluoridation efficiency, and the adsorption by hydroxide aluminum flocs gave a secondary effect. The parameters affected the efficiencies of defluoridation in a way of changing the fluoride distribution in the EC process. A chemical complex of Aln(OH)mFk3n−m−k was formulated to explain the mechanism inside the EC defluoridation process. The new approach provides a detailed insight of the electrocondensation effect, which helps to gain more scientific comprehension about the cooperation between electrochemical and chemical ways occurring inside the EC process.
Co-reporter:Nan Xu;Weiling Sun
Water, Air, & Soil Pollution 2007 Volume 184( Issue 1-4) pp:207-216
Publication Date(Web):2007 September
DOI:10.1007/s11270-007-9409-x
The sorption of hydrophobic organic pollutants on soils or sediments has been widely studied. However, more attention in the previous studies has been paid to sorption mechanism and effects of relevant environmental factors, few studies were reported on effects of heavy metals on the sorption of hydrophobic organic pollutants. In this paper, sorption of phthalate esters (diethyl phthalate, DEP, and di-n-butyl phthalate, DnBP) and copper on the Yellow River sediment was investigated with particular attention to the effects of copper on the phthalate sorption. The experimental results show that the sorption isotherms of phthalates could be reasonably described by the Freundlich equation. Higher sorption equilibrium constant was obtained for DnBP due to its greater hydrophobicity. The existence of copper would enhance the sorption of DnBP. Moreover, strong sorption of copper to sediment were found and attributed to abundant carbonates in the Yellow River sediment. After carbonates were removed, notable effects of copper on the phthalate sorption were observed due to the decrease of copper sorption and the increase of aqueous copper concentration. With 153 mg l−1 copper added, the partition coefficient decreases by 52% for DEP and increases by 79% for DnBP. Primary factors that may influence interaction between the sorption of copper and DEP and DnBP were also investigated, such as complexation between copper and phthalate, and phthalate hydrophobicity. The complexation between phthalate esters and copper was substantiated by polarogram and fluorescence spectrograph, and the calculated mol ratio of complexation (copper : phthalate) was found to be 2:1.
Co-reporter:Ming Chang;Shun-gui Zhou;Na Lu;Jin-ren Ni
Water, Air, & Soil Pollution 2007 Volume 186( Issue 1-4) pp:75-84
Publication Date(Web):2007 November
DOI:10.1007/s11270-007-9466-1
Sewage sludge is a cost-effective media for the production of Bacillus thuringiensis (Bt) based biopesticides. To enhance the entomotoxicity of the fermentation broth, pretreatments of sewage sludge by alkali and ultrasonic were applied in this study. Effects of alkaline and ultrasonic pretreatments on the soluble COD (SCOD) and total COD (TCOD) were evaluated by altering the alkali addition dose and the ultrasonic specific energy. Suitable pretreatment conditions were optimized with 5 g l−1 sodium hydroxide (NaOH) for alkaline treatment and 1.2 × 105 kJ kg−1 of total solid for ultrasonic treatment. Fermentations of raw and pretreated sludge for biopesticides were carried out in a bench scale fermentor. Results revealed that both pretreatments were effective for Bt growth and metabolism. Higher viable cells (VC) and viable spores (VS) counts, δ-endotoxin yields and entomotoxicity were achieved in the pretreated sludge. The enhancement was attributed to more available nutrients and better oxygen transfer. Moreover, ultrasonic pretreated sludge was superior to alkaline pretreated sludge for δ-endotoxin production and entomotoxicity owing to its higher soluble C/N ratio and finer particles.
Co-reporter:Haidong Zhou, Jinren Ni, Wen Huang, Jiandong Zhang
Separation and Purification Technology 2006 Volume 52(Issue 1) pp:29-38
Publication Date(Web):November 2006
DOI:10.1016/j.seppur.2006.03.011
This work examined the use of a two-stage tangential flow filtration process for the separation of hyaluronic acid from fermentation broth. Microfiltration (MF) membranes (0.45, 0.20 μm in pore diameter) and ultrafiltration (UF) membranes (MWCO 300, 100 kDa), made from polyvinylidene fluoride, were used to achieve the separation in series. Operating conditions of each stage were firstly optimized to give the best separation. Then, the two-stage membrane process was undertaken with two separating schemes: the first using MF followed by UF with pure water as diafiltrate, the second similar to the first except permeate from previous UF stage as diafiltrate for MF stage. The optimal conditions were transmembrane pressure 0.1 MPa, crossflow velocity 1.25 m/s, solution pH 4.0 and enhanced ionic strength 0.25 mol/l NaCl for MF membranes, and 0.15 MPa, 1.25 m/s, pH 7.0 and 0.1–0.25 mol/l NaCl for UF membranes, respectively. The two schemes could effectively separate and purify HA with above 77% overall yield and about 1000 purification factor. The second scheme seemed to be more effective for its higher overall yield (89%) and saving water.
Co-reporter:Jinren Ni, Liying Sun, Tianhong Li, Zheng Huang, Alistair G.L. Borthwick
Journal of Environmental Management (October 2010) Volume 91(Issue 10) pp:1930-1942
Publication Date(Web):1 October 2010
DOI:10.1016/j.jenvman.2010.02.010
An understanding of flood impact in terms of sustainability is vital for long-term disaster risk reduction. This paper utilizes two important concepts: conventional insurance related flood risk for short-term damage by specific flood events, and long-term flood impact on sustainability. The Insurance Related Flood Risk index, IRFR, is defined as the product of the Flood Hazard Index (FHI) and Vulnerability. The Long-term Flood Impact on Sustainability index, LFIS, is the ratio of the flood hazard index to the Sustainable Development Index (SDI). Using a rapid assessment approach, quantitative assessments of IRFR and LFIS are carried out for 2339 counties and cities in mainland China. Each index is graded from ‘very low’ to ‘very high’ according to the eigenvalue magnitude of cluster centroids. By combining grades of FHI and SDI, mainland China is then classified into four zones in order to identify regional variations in the potential linkage between flood hazard and sustainability. Zone I regions, where FHI is graded ‘very low’ or ‘low’ and SDI is ‘medium’ to ‘very high’, are mainly located in western China. Zone II regions, where FHI and SDI are ‘medium’ or ‘high’, occur in the rapidly developing areas of central and eastern China. Zone III regions, where FHI and SDI are ‘very low’ or ‘low’, correspond to the resource-based areas of western and north-central China. Zone IV regions, where FHI is ‘medium’ to ‘very high’ and SDI is ‘very low’ to ‘low’, occur in ecologically fragile areas of south-western China. The paper also examines the distributions of IRFR and LFIS throughout mainland China. Although 57% of the counties and cities have low IRFR values, 64% have high LFIS values. The modal values of LFIS are ordered as Zone I < Zone II ≈ Zone III < Zone IV; whereas the modal values of IRFR are ordered as Zone I < Zone III < Zone IV < Zone II. It is recommended that present flood risk policies be altered towards a more sustainable flood risk management strategy in areas where LFIS and IRFR vary significantly, with particular attention focused on Zone IV regions, which presently experience poverty and a deteriorating eco-system.
Co-reporter:Hui Li, Jinren Ni, Wei Liu, Yuling Zhu
Resources, Conservation and Recycling (October 2010) Volume 54(Issue 12) pp:1145-1151
Publication Date(Web):1 October 2010
DOI:10.1016/j.resconrec.2010.03.008
Conventional process in saponin industry resulted in severe environmental problems in China. Millions of tons of high strength wastewater discharged to the ambient rivers and threatened the safety of local drinking water and the major function as drinking water source of the ambitious South-to-North Water Transfer Project. In this paper, cleaner production alternatives for saponin industry were investigated with material flow analysis (MFA) with particular attention to pollutants reduction through starch transformation. Simulation experiments were conducted to evaluate the two proposed schemes primarily in terms of recycling principle characterized by reduce, reuse and recycle. Quantitative evaluation was carried out from four aspects including resource conservation, pollution reduction, starch recycling efficiency and diosgenin yield. The experimental results showed that starch recycle was an effective measure for the cleaner production of saponin industry, and especially the starch recycle before acid hydrolysis (scheme I) would greatly alleviate the load to acid hydrolysis and reduce pollution at the source. By recycling starch, both schemes could reduce 45–50% of pollutants and 32–35% of wastewater comparing with the conventional process, besides, about 64% (scheme I) and 75% (scheme II) of starch could be utilized and thus extra profit which was more than 20,000 RMB yuan/t diosgenin could be achieved. Starch recycle before acid hydrolysis (in scheme I) would result in a saving of 40% sulfuric acid and a lowering of 50% material intensity, while the starch recycle after acid hydrolysis (in scheme II) would have much less contribution to the reduction of both material intensity and pollutants. Therefore, starch recycling should be implemented with priority at the earlier stage of the whole processing system.
Co-reporter:Qian Chen, Jinren Ni
Journal of Bioscience and Bioengineering (May 2012) Volume 113(Issue 5) pp:619-623
Publication Date(Web):1 May 2012
DOI:10.1016/j.jbiosc.2011.12.012
Characteristics of ammonium removal by a newly isolated heterotrophic nitrification–aerobic denitrification bacterium Agrobacterium sp. LAD9 were systematically investigated. Succinate and acetate were found to be the most favorable carbon sources for LAD9. Response surface methodology (RSM) analysis demonstrated that maximum removal of ammonium occurred under the conditions with an initial pH of 8.46, C/N ratio of 8.28, temperature of 27.9°C and shaking speed of 150 rpm, where temperature and shaking speed produced the largest effect. Further nitrogen balance analysis revealed that 50.1% of nitrogen was removed as gas products and 40.8% was converted to the biomass. Moreover, the occurrence of aerobic denitrification was evidenced by the utilization of nitrite and nitrate as nitrogen sources, and the successful amplifications of membrane bound nitrate reductase and cytochrome cd1 nitrite reductase genes from strain LAD9. Thus, the nitrogen removal in strain LAD9 was speculated to comply with the mechanism of heterotrophic nitrification coupled with aerobic denitrification (NH4+–NH2OH–NO2−–N2O–N2), in which also accompanied with the mutual transformation of nitrite and nitrate. The findings can help in applying appropriate controls over operational parameters in systems involving the use of this kind of strain.
Co-reporter:Liying Sun, Jinren Ni, Alistair G.L. Borthwick
Journal of Environmental Management (March–April 2010) Volume 91(Issue 4) pp:1021-1031
Publication Date(Web):1 March 2010
DOI:10.1016/j.jenvman.2009.12.015
This paper presents an approach for rapid assessment of sustainability for Mainland China based on a multilayer index system. Efficient assessment is conducted with the basic mapping units at county and city levels. After evaluating a comprehensive sustainable development index, SDI, for each unit, five rankings of sustainability are determined, and a zonation map produced. Regional characteristics and differences are interpreted through macro-analysis of the spatial variation in SDI. A sensitivity analysis is performed by which the weights of the sub-indices are altered by ±20%, and SDI re-evaluated; the resulting grades remain the same, thus confirming the robustness of the technique. Moreover, the accuracy of the proposed approach is indirectly validated by comparison with assessment results from an alternative systems analysis method. It is found that major conurbations such as Beijing have relatively high levels of sustainability, whereas provinces in central and western China require investment to improve their sustainability.
Co-reporter:Hua-Zhang Zhao, Wei Yang, Jun Zhu, Jin-Ren Ni
Chemosphere (March 2009) Volume 74(Issue 10) pp:1391-1395
Publication Date(Web):1 March 2009
DOI:10.1016/j.chemosphere.2008.11.062
The defluoridation efficiency (εF) of electrocoagulation (EC) is closely related to the pH level of the F−-containing solution. The pH level usually needs to be adjusted by adding acid in order to obtain the highest εF for the F−-containing groundwater. The use of combined EC (CEC), which is the combination of chemical coagulation with EC, was proposed to remove fluoride from drinking water for the first time in this study. The optimal scheme for the design and operation of CEC were obtained through experiments on the treatment of F−-containing groundwater. It was found, with OH− being the only alkalinity of the raw water, that the highest efficiency would be obtained when the molar ratio of alkalinity and fluoride to Al(III) (γAlkalinity+F) was controlled at 3.0. However, when the raw water contained HCO3- alkalinity, a correction coefficient was needed to correct the concentration of HCO3- to obtain the optimal defluoridation condition of γAlkalinity+F = 3.0 for CEC. The correction coefficient of HCO3- concentration was concluded as 0.60 from the experiment. For the practical F−-containing groundwater treatment, CEC can achieve similar εF as an acid-adding EC process. The consumption of aluminum electrode was decreased in CEC. The energy consumption also declined greatly in CEC, which is less than one third of that in the acid-adding EC process.
Co-reporter:Mengyao Gui, Qian Chen, Jinren Ni
Bioresource Technology (July 2017) Volume 235() pp:
Publication Date(Web):1 July 2017
DOI:10.1016/j.biortech.2017.03.131
•SMX (≥2 μg/L) restrained aerobic denitrification by strain PCN-1.•Suppression of SMX on ETSA (electron transport system activity) was observed.•SMX inhibited denitrifying gene expression in order of nosZ > cnorB > nirS > napA.•SMX led to a time-lapse expression between nosZ and cnorB.Sulfamethoxazole (SMX), as a common sulfonamide antibiotic, was reported to affect conventional anaerobic denitrification. This study presented effects of SMX on aerobic denitrification by an aerobic denitrifier strain Pseudomonas stutzeri PCN-1. Results demonstrated serious inhibition of N2O reduction as SMX reached 4 μg/L, leading to higher N2O emission ratio (251-fold). Increase of SMX (∼8 μg/L) would induce highest nitrite accumulation (95.3 mg/L) without reduction, and severe inhibition of nitrate reduction resulted in lower nitrate removal rate (0.15 mg/L/h) as SMX reached 20 μg/L. Furthermore, corresponding inhibition of SMX on denitrifying genes expression (nosZ > nirS > cnorB > napA) was found with a time-lapse expression between nosZ and cnorB. Meanwhile, the decline in electron transport activity and active microbial biomass of strain PCN-1 was revealed. The insight into mechanism of SMX influence on aerobic denitrifier is of particular significance to upgrade nitrogen removal process in antibiotics-containing wastewater treatment plant.Download high-res image (180KB)Download full-size image
Co-reporter:Li Fan, Shunni Zhu, Dongqi Liu, Jinren Ni
International Biodeterioration & Biodegradation (January 2009) Volume 63(Issue 1) pp:88-92
Publication Date(Web):1 January 2009
DOI:10.1016/j.ibiod.2008.07.004
A novel isolate of Sphingomonas herbicidovorans could decolorize 1-amino-4-bromoanthraquinone-2-sulfonic acid (bromoamine acid, BAA), an intermediate of anthraquinone dyes, and grow with it as the sole source of carbon. The strain was identified by 16S rRNA gene sequencing and physiological-biochemical test. The optimal condition for both decolorization and cell growth was found at temperature of 30 °C and pH 7.0, respectively. Furthermore, the decolorization efficiency could be enhanced with higher shaking speed. The percentage of BAA decolorization could be over 98% within 24 h even for the initial concentration greater than 1000 mg l−1. The decolorization kinetics could be reasonably described by the Monod equation. Additional carbon sources such as glucose could enhance the decolorization rate. During the decolorization process, the molecular of BAA cleaved, releasing phthalic acid and an end product which might be benzene derivative substituted by amino, bromo, hydroxyl and sulfonate groups according to the infrared spectral analysis.
Co-reporter:Yuling Zhu, Wen Huang, Jinren Ni
Journal of Cleaner Production (February 2010) Volume 18(Issue 3) pp:242-247
Publication Date(Web):1 February 2010
DOI:10.1016/j.jclepro.2009.10.012
This study proposes a new approach for diosgenin production from Dioscorea zingiberensis C. H. Wright tubers with respect to resources utilization and clean production. This process consisted of two successive parts, i.e., recovery of starch from raw material, and microbial hydrolysis of the residue to produce diosgenin by Trichoderma reesei. In the first step, about 75.4% of hemicellulose and 98.0% of starch were removed from the tubers. In the second step, about 90.2% of diosgenin was released from saponins by T. reesei at 30 °C, at an aeration of 0.80 vvm and agitation rate of 300 rpm in a 5.0 L bioreactor. Significant reduction of pollutant production was detected by replacing the traditional approach with the proposed new method. About 99.2% of reducing sugar, 99.4% of chemical oxygen demand, 99.2% of total organic carbon, 100% of SO42−, and 100% of acid was reduced in the new processing wastewater.
Co-reporter:Peng HAN, Jin-Ren NI, Ke-Bin HOU, Chi-Yuan MIAO, Tian-Hong LI
International Journal of Sediment Research (December 2011) Volume 26(Issue 4) pp:403-415
Publication Date(Web):1 December 2011
DOI:10.1016/S1001-6279(12)60001-8
A self-organizing model was developed for simulating rill erosion process on slopes with particular attention to the role of gravitational erosion. For a complete simulation circle, processes such as precipitation, infiltration, runoff, scouring, gravitational erosion and elevation variation were fully considered. Precipitation time (or runoff time) was regarded as iteration benchmark in the model. To specify the contribution of gravitational erosion to the process of rill formation and development, a gravitational erosion module was inserted into the model. Gravitational erosion in rill development was regarded as a Gaussian random process. A model was calibrated by our experimental data, and further validated satisfactorily with 22 runs of experimental results from different investigators. Systematic comparison was made between sediment yields with and without consideration of gravitational erosion module. It was demonstrated that the model could reasonably simulate the rill erosion process under a variety of slope gradients, rainfall intensities and soil conditions upon the gravitational erosion being considered. However, the role of gravitational erosion on sediment yields in rill systems varies significantly under different conditions, although it is of the utmost importance in steeper slopes. The process of gravitational erosion in rill development was studied by a newly-defined parameter ω, which is defined as the volume ratio of gravitational erosion over hydraulic-related erosion. The gravitational contribution to the total erosion could be over 50% for the rill systems with higher rainfall intensity and steeper slopes.
Co-reporter:Chiyuan Miao, Jinren Ni, Alistair G.L. Borthwick, Lin Yang
Global and Planetary Change (April 2011) Volume 76(Issues 3–4) pp:196-205
Publication Date(Web):1 April 2011
DOI:10.1016/j.gloplacha.2011.01.008
Water discharge and sediment load have changed continuously during the last half century in the Yellow River basin, China. In the present paper, data from 7 river gauging stations and 175 meteorological stations are analyzed in order to estimate quantitatively the contributions of human activities and climate change to hydrological response. Coefficients of water discharge (Cw) and sediment load (Cs) are calculated for the baseline period of 1950s–1960s according to the correlations between the respective hydrological series and regional precipitation. Consequently, the natural water discharge and natural sediment load time series are reconstructed from 1960s–2008. Inter-annual impacts are then separated from the impacts of human activities and climate change on the hydrological response of different regions of the Yellow River basin. It is found that human activities have the greatest influence on changes to the hydrological series of water discharge and sediment load, no matter whether the effect is negative or positive. Moreover, the impact of human activities is considerably greater on water discharge than sediment load. During 1970–2008, climate change and human activities respectively contribute 17% and 83% to the reduction in water discharge, and 14% and 86% to the reduction in sediment yield in the Upper reaches of Yellow River basin; The corresponding relative contributions in the Middle reaches are 71% and 29% to reductions in water discharge, and 48% and 52% to reductions in sediment load. Moreover, it is observed that the impacts of human activities on the whole basin are enhanced with time. In the 2000s, the impact of human activities exceeds that of climate change in the 2000s, with human activities directly responsible for 55% and 54% of the reductions in water discharge and sediment load in the whole basin.Research highlights► Coefficients of water discharge and sediment load are involved; ► Natural water discharge and natural sediment load time series are reconstructed; ► The impacts of human activities is greater on water discharge than sediment load; ► The impacts of human activities on the whole basin are enhanced with time; ► In the 2000s, the impact of human activities directly responsible for 55% and 54% of the reductions in water discharge and sediment load in the whole basin.
Co-reporter:Bin Zhao, Huazhang Zhao, Jinren Ni
Chemical Engineering Journal (15 May 2010) Volume 160(Issue 1) pp:170-175
Publication Date(Web):15 May 2010
DOI:10.1016/j.cej.2010.03.033
Donnan dialysis is an ion exchange membrane process driven by an electrochemical potential gradient that is capable of removing ionic contaminants from water. To better understand and simulate arsenate (As(V)) removal by Donnan dialysis, a simple model focusing on intermembrane ionic diffusion at steady state was developed based on the Nernst–Planck equation in this study. Using experimental data from independent ion exchange reaction experiments and dialysis experiments, the self-diffusion coefficient of As(V) in the anion exchange membrane was calculated. This value was on the order of 10−8 m2 h−1 and related to the system pH and membrane type. The As(V) removal by Donnan dialysis (feed solution: 1 L, 1.3 × 10−2 mol As m−3 (1000 μg As L−1) with 10 mol m−3 NaCl; stripping solution: 1 L, 100 mol m−3 NaCl) was conducted with different types of membrane at different system pH. At the end of the 12-h dialysis, the removal efficiency was lowest (35%) for the heterogeneous membrane at pH 4.5 and highest (95%) for the homogeneouse membrane at pH 9.2. Higher ion-membrane affinity, higher intermembrane ionic mobility, and thinner membrane thickness facilitated the As(V) transfer according to the model results. Using the calculated membrane phase self-diffusion coefficients and the corresponding distribution coefficients of As(V) between the membrane and the solution, the present model successfully predicted the As(V) removal profiles of different dialytic conditions.
Co-reporter:Lin Xiong, Ye Yang, Jiaxing Mai, Weiling Sun, Chaoying Zhang, Dapeng Wei, Qing Chen, Jinren Ni
Chemical Engineering Journal (15 January 2010) Volume 156(Issue 2) pp:313-320
Publication Date(Web):15 January 2010
DOI:10.1016/j.cej.2009.10.023
Calcined titanate nanotubes were synthesized with hydrothermal treatment of the commercial TiO2 (Degussa P25) followed by calcination. The morphology and structures of as-prepared samples were investigated by transmission electron microscopy, X-ray diffraction and N2 adsorption/desorption. The samples exhibited a tubular structure and a high surface area of 157.9 m2/g. The adsorption of methylene blue onto calcined titanate nanotubes was studied. The adsorption kinetics was evaluated by the pseudo-first-order, pseudo-second-order and Weber's intraparticle diffusion model. The pseudo-second-order model was the best to describe the adsorption kinetics, and intraparticle diffusion was not the rate-limiting step. The equilibrium adsorption data were analyzed with three isotherm models (Langmuir model, Freundlich model and Temkin model). The best agreement was achieved by the Langmuir isotherm with correlation coefficient of 0.993, corresponding to maximum adsorption capacity of 133.33 mg/g. The adsorption mechanism was primarily attributed to chemical sorption involving the formation of methylene blue-calcined titanate nanotubes nanocomposite, associated with electrostatic attraction in the initial bulk diffusion.
Co-reporter:Jun Zhu, Huazhang Zhao, Jinren Ni
Separation and Purification Technology (15 August 2007) Volume 56(Issue 2) pp:184-191
Publication Date(Web):15 August 2007
DOI:10.1016/j.seppur.2007.01.030
Electrocoagulation (EC) is an effective process to remove fluoride from water, but few of scientific literatures explore its inside mechanism. A new approach was used in this study to investigate fluoride distribution in the EC defluoridation process, which divided the fluoride into three parts: remained in water, removed by electrodes, and adsorbed on hydroxide aluminum flocs. The fluoride distribution was investigated in terms of several critical parameters such as pH, charge loading, current density and initial fluoride concentration. The experimental results showed that the removal by electrodes was primarily responsible for the high defluoridation efficiency, and the adsorption by hydroxide aluminum flocs gave a secondary effect. The parameters affected the efficiencies of defluoridation in a way of changing the fluoride distribution in the EC process. A chemical complex of Aln(OH)mFk3n−m−k was formulated to explain the mechanism inside the EC defluoridation process. The new approach provides a detailed insight of the electrocondensation effect, which helps to gain more scientific comprehension about the cooperation between electrochemical and chemical ways occurring inside the EC process.
Co-reporter:Wen Liu, Xiao Zhao, Ting Wang, Jie Fu and Jinren Ni
Journal of Materials Chemistry A 2015 - vol. 3(Issue 34) pp:NaN17684-17684
Publication Date(Web):2015/07/24
DOI:10.1039/C5TA04521E
A novel flower-like titanate nanomaterial (titanate nanoflowers, TNFs) was synthesized through a hydrothermal method using nano-anatase and sodium hydroxide, and used for mercury(II) removal from aqueous solution. The large surface area (187.32 m2 g−1) and low point of zero charge (3.04) of TNFs facilitated the adsorption of cations. Adsorption experiments indicated that TNFs could quickly capture 98.2% of Hg(II) from solution within 60 min at pH 5. The maximum adsorption capacity of Hg(II) was as large as 454.55 mg g−1 calculated by the Langmuir isotherm model. Moreover, selective adsorption of Hg(II) by TNFs was observed with the coexistence of other conventional cations (i.e., Na+, K+, Mg2+ and Ca2+) even at 10 times concentration of Hg(II). XRD analysis indicated that the prepared TNFs were a kind of tri-titanate composed of an edge-sharing triple [TiO6] octahedron and interlayered Na+/H+, and ion-exchange between Hg2+ and Na+ was the primary adsorption mechanism. Furthermore, it was interesting that the basic crystal structure of TNFs, tri-titanate (Ti3O72−), transformed into hexa-titanate (Ti6O132−) after adsorption, resulting in the trapping of Hg(II) into the lattice tunnel of this hexa-titanate. Desorption experiments also confirmed the irreversible adsorption due to Hg(II) trapped in TNFs, which achieved safe disposal of this highly toxic metal in practical application.
![THIAZOLO[4,5-F]QUINOLINE, 2-METHYL- (9CI)](http://img.cochemist.com/ccimg/38500/38463-33-1.png)
![THIAZOLO[4,5-F]QUINOLINE, 2-METHYL- (9CI)](http://img.cochemist.com/ccimg/38500/38463-33-1_b.png)
