Frontiers of Environmental Science & Engineering

ISSN 2095-2201

ISSN 2095-221X(Online)

CN 10-1013/X

2015 Impact Factor: 1.799

Cover Story   2017, Volume 11 Issue 6
Silicon(Si) is a widely applied photovoltage material in solar energy harvesting. However, the spontaneous oxidation process of pristine Si limits its application as photocatalyst or electrode in aqueous solution or moist air. Covering a protection layer on Si surface is an effective approach to overcome this disadvantage. In this paper, α-Fe2O3 is demonstrated to be an excellent alternative as a protection material. Compared with Si itself, the optical absorption and photocurrent density of α-Fe2O3 coated Si improved 2 times and 4 times, respectively, and its onset potential for hydrogen evolution moved positively about 0.4 V. These improved performances could be ascribed to the enhanced photogenerated-charge-separation efficiency deriving from built-in electric field at the interface between Si and α-Fe2O3. In this work, the application of Si materials as photocatalysts or electrodes in aqueous solution or moist air can be promoted. This could be further beneficial to utilizing in solar water splitting to produce hydrogen, CO2 reduction and pollutants degradation (e.g. dehalogenation).
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RESEARCH ARTICLE
Formation of disinfection byproducts from accumulated soluble products of oleaginous microalga after chlorination
Yu Liu, Qiao Zhang, Yu Hong
Front. Environ. Sci. Eng.. 2017, 11 (6): 1-.  
https://doi.org/10.1007/s11783-017-0938-2

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SAP mainly are aromatic proteins and soluble microbial by-product-like.

[DBP] increased with cultivation time and [SAP] increasing.

The formation potential trend of DBP is as follows: TCM>DCAA>TCAA.

When microalgae are simultaneously applied for wastewater treatment and lipid production, soluble algal products (SAP) should be paid much attention, as they are important precursors for formation of disinfection byproducts (DBPs), which have potential risks for human health. Chlorella sp. HQ is an oleaginous microalga that can generate SAP during growth, especially in the exponential phase. This study investigated the contribution of SAP from Chlorella sp. HQ to DBP formation after chlorination. The predominant DBP precursors from SAP were identified with the 3D excitation-emission matrix fluorescence. After chlorination, a significant reduction was observed in the fluorescence intensity of five specific fluorescence regions, particularly aromatic proteins and soluble microbial by-product-like regions, accompanied with slight shifting of the peak. The produced DBPs were demonstrated to include trihalomethanes and haloacetic acids. As the algal cultivation time was extended in wastewater, the accumulated SAP strengthened the formation of DBPs. The trend for DBP formation was as follows: chloroform>dichloroacetic acid>trichloroacetic acid.

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Development and characterization of an anaerobic microcosm for reductive dechlorination of PCBs
Dawei Liang, Shanquan Wang
Front. Environ. Sci. Eng.. 2017, 11 (6): 2-.  
https://doi.org/10.1007/s11783-017-0939-1

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A robust PCB-dechlorinating sediment-free enrichment culture is developed.

This enrichment culture can extensively dechlorinate a PCB mixture Aroclor 1260.

This culture effectively catalyzes major meta-PCBs dechlorination.

This study facilitates the exploration of PCB dechlorinators for bioremediation.

The toxic and recalcitrant polychlorinated biphenyls (PCBs) adversely affect human and biota by bioaccumulation and biomagnification through food chain. In this study, an anaerobic microcosm was developed to extensively dechlorinate hexa- and hepta-CBs in Aroclor 1260. After 4 months of incubation in defined mineral salts medium amended PCBs (70 mmol·L1) and lactate (10 mmol·L1), the culture dechlorinated hexa-CBs from 40.2% to 8.7% and hepta-CBs 33.6% to 11.6%, with dechlorination efficiencies of 78.3% and 65.5%, respectively (all in moL ratio). This dechlorination process led to tetra-CBs (46.4%) as the predominant dechlorination products, followed by penta- (22.1%) and tri-CBs (5.4%). The number of meta chlorines per biphenyl decreased from 2.50 to 1.41. Results of quantitative real-time PCR show that Dehalococcoides cells increased from 2.39 × 105±0.5 × 105 to 4.99 × 107±0.32 × 107 copies mL1 after 120 days of incubation, suggesting that Dehalococcoides play a major role in reductive dechlorination of PCBs. This study could prove the feasibility of anaerobic reductive culture enrichment for the dehalogenation of highly chlorinated PCBs, which is prior to be applied for in situ bioremediation of notorious halogenated compounds.

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Comparison of different algicides on growth of Microcystis aeruginosa and microcystin release, as well as its removal pathway in riverways
Naiyu Wang, Kai Wang, Can Wang
Front. Environ. Sci. Eng.. 2017, 11 (6): 3-.  
https://doi.org/10.1007/s11783-017-0940-8

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Aluminum silicate is the most effective algicide on Microcystis aeruginosa control.

Algicides increased MC-LR concentration by disrupting M. aeruginosa cells.

Acute biotoxicity and extracellular MC-LR concentration were positively correlated.

MC-LR was mainly removed by benthal sludge and UV-rays under natural conditions.

Eutrophication with a large number of Microcystis aeruginosa commonly occurs worldwide, thereby threatening the aquatic ecosystem and human health. In this study, four kinds of algicides were tested to explore their influence on cell density and chlorophyll-a of M. aeruginosa. Results showed that aluminum silicate agent, which inhibited more than 90% cell growth compared with the control group, demonstrated the strongest inhibition effect immediately on M. aeruginosa growth. Furthermore, the production and release of microcystin (MC)-LR were investigated. Aluminum silicate, CuSO4, and Emma-11 were more effective than pyrogallic acid in disrupting the cells of M. aeruginosa, thereby increasing the extracellular MC-LR concentration. Aluminum silicate caused the highest extracellular MC-LR concentration of more than 45 mg·L1. Biotoxicity was also detected to evaluate the environmental risks of MC-LR release, which were related to the usages of different algicides. Extracellular MC-LR concentration mostly increased when the biotoxicity of algae solution increased. The experiments were also designed to reveal the effects of physical conditions in riverways, such as natural sunlight, aeration and benthal sludge, on MC-LR degradation. These findings indicated that UV rays in sunlight, which can achieve a MC-LR removal efficiency of more than 15%, played an important role in MC-LR degradation. Among all the physical pathways of MC-LR removal, benthal sludge adsorption presented the optimal efficiency at 20%.

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Performance evaluation of circulating fluidized bed incineration of municipal solid waste by multivariate outlier detection in China
Hua Tao, Pinjing He, Yi Zhang, Wenjie Sun
Front. Environ. Sci. Eng.. 2017, 11 (6): 4-.  
https://doi.org/10.1007/s11783-017-0945-3

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Reducing load change frequency is more important than magnitude for performance.

Overloading is more often than underloading. The frequent overloading is 0% to 30%.

Heterogeneous property of MSW can be magnified by the frequent load changes.

Appropriate MSW storage capacity may buffer and reduce the frequency of load change.

This first nationwide survey was conducted to evaluate the overall performance of the circulating fluidized bed (CFB) incineration of municipal solid waste (MSW) in 2014-2015 in China. Total 23 CFB incineration power plants were evaluated. The data for monthly average flue gas emission of particles, CO, NOx, SO2 and HCl were collected over 12 consecutive months. The data were analyzed to assess the overall performance of CFB incineration by applying the Mahalanobis distance as a multivariate outlier detection method. Although the flue gas emission parameters had met the Chinese national emission standards, there were 11 total outliers (abnormal behavior) detected in 6 out of 23 CFB incineration power plants from the perspective of the MSW incineration performance. The results demonstrate that it is more important for a better performance of CFBs to reduce the frequencies of the MSW load changes, rather than the magnitudes of the MSW load changes, particularly reducing the frequencies in the range of 10% and more of the load changes, under the same and stable conditions. Furthermore, the overloading occurs more often than the underloading during the operation of the CFB incineration power plants in China. The frequent overloading is 0% to 30% of the designed capacity. To achieve the stable performance of CFBs in practice, an appropriately designed MSW storage capacity is suggested to build in a plant to buffer and reduce the frequency of the load changes.

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Assessment of leaching behavior and human bioaccessibility of rare earth elements in typical hospital waste incineration ash in China
Chunfeng Wang, Guanfei Chen, Yanchen Zhu, Dan Yao, Wanfeng Wang, Lianjun Wang
Front. Environ. Sci. Eng.. 2017, 11 (6): 5-.  
https://doi.org/10.1007/s11783-017-0946-2

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• Leaching behavior and human bioaccessibility of REEs in HWI ashes were assessed.

• LREE leached amounts were higher than those of HREEs via both leaching tests.

• REEs were extracted to the higher level by PBET method compared to leaching test.

• Bioaccessibility results depend commonly on pH value and chelating role.

• Synergetic effects of contaminants in HWI ashes need further investigation.

Leaching behavior and gastrointestinal bioaccessibility of rare earth elements (REEs) from hospital waste incineration (HWI) fly and bottom ash samples collected from Beijing and Nanjing Cities were assessed. In the same ash sample, the leaching concentrations of individual REEs determined by the Toxicity Characteristic Leaching Procedure (TCLP) were higher than those detected by the European standard protocol (EN-type test), thereby suggesting that the low pH value of leaching solution was an important factor influencing the leachability of REE. The REE bioaccessibility results, which were evaluated using the physiologically based extraction test (PBET), indicated that REEs were highly absorbed during gastric phase by dissolution; and subsequently precipitated and/or re-adsorbed in small intestinal phase. The relative amounts of the total REEs extracted by the TCLP method, EN-type test and PBET test were compared. In addition to the pH value of extraction solutions, the chelating role of REEs with organic ligands used in the PBET method was also an important parameter affecting REE adsorption in human body. Additionally, this study showed that REEs were extracted by these methods as concomitants of heavy metals and anions (NO3, F, SO42, and Cl) from HWI ash, which probably caused the remarkably complex toxicity on human body by the exposure pathway.

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Impact of food to microorganism ratio and alcohol ethoxylate dosage on methane production in treatment of low-strength wastewater by a submerged anaerobic membrane bioreactor
Yulun Nie, Xike Tian, Zhaoxin Zhou, Yu-You Li
Front. Environ. Sci. Eng.. 2017, 11 (6): 6-.  
https://doi.org/10.1007/s11783-017-0947-1

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Efficient methane recovery was obtained when the F/M ratio was below 0.357.

AE was efficiently degraded and converted into CH 4 by anaerobic microbes.

Microbe could cope with the stress of AE by producing more EPS and SMP.

F/M ratio of 1.054 decrease the methane production potential significantly.

The methane production activity of sludge was inhibited at a higher AE dosage.

The effects of food to microorganism (F/M) ratio and alcohol ethoxylate (AE) dosage on the methane production potential were investigated in treatment of low-strength wastewater by a submerged anaerobic membrane bioreactor (SAnMBR). The fate of AE and its acute and/or chronic impact on the anaerobic microbes were also analyzed. The results indicated that AE had an inhibitory effect to methane production potential (lag-time depends on the AE dosage) and the negative effect attenuated subsequently and methane production could recover at F/M ratio of 0.088–0.357. VFA measurement proved that AE was degraded into small molecular organic acids and then converted into methane at lower F/M ratio (F/M<0.158). After long-term acclimation, anaerobic microbe could cope with the stress of AE by producing more EPS (extracellular polymeric substances) and SMP (soluble microbial products) due to its self-protection behavior and then enhance its tolerance ability. However, the methane production potential was considerably decreased when AE was present in wastewater at a higher F/M ratio of 1.054. Higher AE amount and F/M ratio may destroy the cell structure of microbe, which lead to the decrease of methane production activity of sludge and methane production potential.

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Roles of glutathione and L-cysteine in the biomimetic green synthesis of CdSe quantum dots
Ling-Li Li, Yin-Hua Cui, Jie-Jie Chen, Han-Qing Yu
Front. Environ. Sci. Eng.. 2017, 11 (6): 7-.  
https://doi.org/10.1007/s11783-017-0948-0

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CdSe QDs were synthesized with CdCl2, Na2SeO3 and bio-thiols under mild conditions.

Compared with L-cysteine, glutathione was superior for CdSe QDs formation.

Cd2+ binding capacity of glutathione contributed to the CdSe QDs formation.

Biological synthesis of quantum dots (QDs) as an environmental-friendly and facile preparation method has attracted increasing interests. However, it is difficult to distinguish the roles of bio-thiols in QDs synthesis process because of the complex nature in organisms. In this work, the CdSe QDs synthesis conditions in organisms were reconstructed by using a simplified in vitro approach to uncover the roles of two small bio-thiols in the QDs formation. CdSe QDs were synthesized with glutathione (GSH) and L-cysteine (Cys) respectively. Compared with Cys at the same molar concentration, the CdSe QDs synthesized by GSH had a larger and broader particle size distribution with improved optical properties and crystal structure. Furthermore, quantum chemical calculations indicate that the stronger Cd2+ binding capacity of GSH contributed a lot to the CdSe QDs formation despite of the greater capability Cys for selenite reduction. This work clearly demonstrates the different roles of small thiols in the Cd2+ stabilization in the environment and biomimetic QDs synthesis process.

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Comparison of sequential with intimate coupling of photolysis and biodegradation for benzotriazole
Shunan Shan, Yuting Zhang, Yining Zhang, Lanjun Hui, Wen Shi, Yongming Zhang, Bruce E. Rittmann
Front. Environ. Sci. Eng.. 2017, 11 (6): 8-.  
https://doi.org/10.1007/s11783-017-0953-3

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Intimately coupling UV photolysis accelerated benzotriazone (BTA) biodegradation.

Photolysis of BTA generated four products: AP, PHZ, FA, and MA.

FA and MA accelerated BTA biodegradation, as they produced internal electron donor.

AP and PHZ slowed BTA biodegradation, as they competed for internal electron donor.

AP and PHZ did not accumulate during the intimately coupling process.

Benzotriazole (BTA) is an emerging contaminant that also is a recalcitrant compound. Sequential and intimate coupling of UV-photolysis with biodegradation were investigated for their impacts on BTA removal and mineralization in aerobic batch experiments. Special attention was given to the role of its main photolytic products, which were aminophenol (AP), formic acid (FA), maleic acid (MA), and phenazine (PHZ). Experiments with sequential coupling showed that BTA biodegradation was accelerated by photolytic pretreatment up to 9 min, but BTA biodegradation was slowed with longer photolysis. FA and MA accelerated BTA biodegradation by being labile electron-donor substrates, but AP and PHZ slowed the rate because of inhibition due to their competition for intracellular electron donor. Because more AP and PHZ accumulated with increasing photolysis time, their inhibitory effects began to dominate with longer photolysis time. Intimately coupling photolysis with biodegradation relieved the inhibition effect, because AP and PHZ were quickly biodegraded and did not accumulate, which accentuated the beneficial effect of FA and MA.

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Transport and selectivity of indium through polymer inclusion membrane in hydrochloric acid medium
Xiaorong Meng, Conghui Wang, Pan Zhou, Xiaoqiang Xin, Lei Wang
Front. Environ. Sci. Eng.. 2017, 11 (6): 9-.  
https://doi.org/10.1007/s11783-017-0950-6

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The mass transfer of PIM to In(III) is of high efficiency.

The separation selectivity of In(III)/Cu(II) is related to the pH value and Cl concentration of the feed phase.

The mass transfer of In(III) is controlled by chemical interaction.

The stability of the membrane is improved by increasing the membrane thickness.

In the present paper, a polymer inclusion membrane (PIM) containing polyvinyl chloride (PVC), and bis-(2-ethylhexyl) phosphate (D2EHPA) which was used as extracting agent was used for the recovery of In(III) ions in hydrochloric acid medium. The effects of carrier concentration, feed phase pH, strip phase HCl concentration, temperature on the transport, and the membrane’s stability and thickness were examined. And the conditions for the selective separation of In(III) and Cu(II) were optimized. The results showed that the transport of In(III) across PIM was consistent with the first order kinetics equation, and also it was controlled by both the diffusion of the metal complex in the membrane and the chemical reaction at the interface of the boundary layers. The transport flux (J0) was inversely proportional to the membrane thickness, however, the transport stability improved as the membrane thickness increased. The transport flux of In(III) and Cu(II) was decreased by excessive acidity of feed phase and high concentration of Cl. The selectivity separation coefficient of In(III)/Cu(II) was up to 34.33 when the original concentration of both In(III) and Cu(II) was 80 mg·L−1 as well as the pH of the feed phase and the concentration of Cl in the adjusting context were0.6 and 0.5 mol·L−1, respectively. Within the range of pH= 1–3, the separation selectivity of In(III)/Cu(II) reached the peak in the case when the Cl concentration was 0.7 mol·L−1 .

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Feasibility of bubble surface modification for natural organic matter removal from river water using dissolved air flotation
Yulong Shi, Jiaxuan Yang, Jun Ma, Congwei Luo
Front. Environ. Sci. Eng.. 2017, 11 (6): 10-.  
https://doi.org/10.1007/s11783-017-0954-2

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Surface modified bubbles were produced in DAF pump saturation system.

Hydrophobic NOM was preferentially removed by chitosan modified bubbles.

Removal of hydrophilic NOM was improved with an increase in chitosan charge density.

Chitosan modified bubbles performed efficiently in THMFP and HAAFP control.

A novel, functionalized bubble surface can be obtained in dissolved air flotation (DAF) by dosing chemicals in the saturator. In this study, different cationic chemicals were used as bubble surface modifiers, and their effects on natural organic matter (NOM) removal from river water were investigated. NOM in the samples was fractionated based on molecular weight and hydrophobicity. The disinfection byproduct formation potentials of each fraction and their removal efficiencies were also evaluated. The results showed that chitosan was the most promising bubble modifier compared with a surfactant and a synthetic polymer. Tiny bubbles in the DAF pump system facilitated the adsorption of chitosan onto microbubble surfaces. The hydrophobic NOM fraction was preferentially removed by chitosan-modified bubbles. Decreasing the recycle water pH from 7.0 to 5.5 improved the removal of hydrophilic NOM with low molecular weight. Likewise, hydrophilic organic compounds gave high dihaloacetic acid yields in raw water. An enhanced reduction of haloacetic acid precursors was obtained with recycle water at pH values of 5.5 and 4.0. The experimental results indicate that NOM fractions may interact with bubbles through different mechanisms. Positive bubble modification provides an alternative approach for DAF to enhance NOM removal.

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Effects of Pd doping on N2O formation over Pt/BaO/Al2O3 during NOx storage and reduction process
Mingxin Dong, Jun Wang, Jinxin Zhu, Jianqiang Wang, Wulin Wang, Meiqing Shen
Front. Environ. Sci. Eng.. 2017, 11 (6): 11-.  
https://doi.org/10.1007/s11783-017-0976-9

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• The NOx reduction ability of Pt/BaO/Al2O3 can be improved by Pd doping.

• Pd-Ba interaction inhibits the NO dissociation over Pd sites.

• (Pt/BaO/Al2O3+Pd/Al2O3) exhibits superior NSR performance.

• (Pt-Pd/BaO/Al2O3+Al2O3) is proved to be an unwished Pd-modified catalyst.

• The N2O formation mechanism over Pd-modified catalyst is provided.

N2O is a powerful greenhouse gas and plays an important role in destructing the ozone layer. This present work investigated the effects of Pd doping on N2O formation over Pt/BaO/Al2O3 catalyst. Three types of catalysts, Pt/BaO/Al2O3, Pt/Pd mechanical mixing catalyst (Pt/BaO/Al2O3+Pd/Al2O3) and Pt-Pd co-impregnation catalyst (Pt-Pd/BaO/Al2O3) were prepared by incipient wetness impregnation method. These catalysts were first evaluated in NSR activity tests using H2/CO as reductants and then carefully characterized by BET, CO chemisorption, CO-DRIFTs and H2-TPR techniques. In addition, temperature programmed reactions of NO with H2/CO were conducted to obtain further information about N2O formation mechanism. Compared with Pt/BaO/Al2O3, (Pt/BaO/Al2O3+Pd/Al2O3) produced less N2O and more NH3 during NOx storage and reduction process, while an opposite trend was found over (Pt-Pd/BaO/Al2O3+Al2O3). Temperature programmed reactions of NO with H2/CO results showed that Pd/Al2O3 component in (Pt/BaO/Al2O3+Pd/Al2O3) played an important role in NO reduction to NH3, and the formed NH3 could reduce NOx to N2 leading to a decrease in N2O formation. Most of N2O formed over (Pt-Pd/BaO/Al2O3+Al2O3) was originated from Pd/BaO/Al2O3 component. H2-TPR results indicated Pd-Ba interaction resulted in more difficult-to-reduce PdOx species over Pd/BaO/Al2O3, which inhibits the NO dissociation and thus drives the selectivity to N2O in NO reduction.

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Assessing human bioaccessibility of trace contaminants in size-fractionated red mud, derived precipitates and geopolymeric blocks
Chunfeng Wang, Yanchen Zhu, Dan Yao, Guanfei Chen, Lianjun Wang
Front. Environ. Sci. Eng.. 2017, 11 (6): 12-.  
https://doi.org/10.1007/s11783-017-0956-0

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PBET values of size-fractionated red mud were depended on pH and chelating role.

MGS results extracted was significantly higher than those by ALF for RM38 samples.

High bioaccessibility values were obtained for derived precipitates using PBET.

High PBET values of the geopolymeric blocks should raise social concerns.

The objective of this study was to provide insight into human exposure to trace contaminants bearing red mud, derived precipitates and geopolymeric blocks due to inhalation contact and/or hand-to-mouth ingestion. The in vitro bioaccessibility behavior of trace contaminants was investigated with the PBET (physiologically based extraction test), ALF (artificial lysosomal fluid) and MGS (modified Gamble’ solution) methods. The results showed that total contents of trace contaminants and operation parameters, such as pH and chelating properties of simulated gastrointestinal phases (PBET), played a joint role in controlling the bioaccessibility efficacy for size-fractionated red mud particles. As for airborne particles (<38 µm size fractions), trace contaminants concentrations extracted by MGS was significantly higher than those by ALF. Additionally, higher bioaccessibility (PBET) values of Cu, Pb, Zn, As, V and U were obtained from red mud derived precipitates compared with those of red mud itself. Even though short-term and long-term leaching values of trace contaminants were relatively lower in the prepared geopolymeric blocks, the health risk could be significantly higher due to the more pronounced bioaccessibility characteristics.

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Covering α-Fe2O3 protection layer on the surface of p-Si micropillar array for enhanced photoelectrochemical performance
Jing Gu, Hongtao Yu, Xie Quan, Shuo Chen
Front. Environ. Sci. Eng.. 2017, 11 (6): 13-.  
https://doi.org/10.1007/s11783-017-0957-z

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SiMP/α-Fe2O3 improved photoeletrochemical stability of Si.

Optical absorption and photocurrent density of SiMP/α-Fe2O3 improved 2 and 4 times.

Enhanced photogenerated charge separation derived from built-in electric field.

Few papers with respect to the α-Fe2O3-covering-Si photocathode had been published.

The spontaneous oxidation process of pristine silicon (Si) limits its application as photocatalyst or electrode in aqueous solution or moist air. Covering a protection layer on Si surface is an effective approach to overcome this disadvantage. In this paper, α-Fe2O3 is demonstrated to be an excellent alternative as a protection material. α-Fe2O3 layer was deposited around each p-type Si micropillar (SiMP) in well-ordered array by chemical bath deposition method. The diameter of SiMP was 5 mm and the thickness of α-Fe2O3 layer was about 20 nm. The photoeletrochemical stability of SiMP/α-Fe2O3 was proved by 10 circles cyclic voltammetry testing. Compared with SiMP, its optical absorption and photocurrent density improved 2 times and 4 times, respectively, and its onset potential for hydrogen evolution moved positively about 0.4 V. These improved performances could be ascribed to the enhanced photogenerated-charge-separation efficiency deriving from built-in electric field at the interface between Si and α-Fe2O3. The above results show an effective strategy to utilize Si material as photocatalyst or electrode in aqueous solution or moist air.

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Competition for electrons between reductive dechlorination and denitrification
Lifeng Cao, Weihua Sun, Yuting Zhang, Shimin Feng, Jinyun Dong, Yongming Zhang, Bruce E. Rittmann
Front. Environ. Sci. Eng.. 2017, 11 (6): 14-.  
https://doi.org/10.1007/s11783-017-0959-x

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Simultaneous reductive dechlorination and denitrification occurred simultaneously in VBBR.

The mechanism of the mutual inhibition between TCP and nitrate or nitrite was identified clearly.

Declorination was more sensitive to competitive inhibition than either denitrification.

Nitrite had a smaller inhibitory impact on TCP reduction than nitrate.

Both reactions proceed more rapidly if the oxidized nitrogen is nitrite instead of nitrate.

All reactions could be accelerated by exogenous electron donors, and especially for TCP reduction.

It is common that 2,4,6-trichlorophenol (TCP) coexists with nitrate or nitrite in industrial wastewaters. In this work, simultaneous reductive dechlorination of TCP and denitrification of nitrate or nitrite competed for electron donor, which led to their mutual inhibition. All inhibitions could be relieved to a certain degree by augmenting an organic electron donor, but the impact of the added electron donor was strongest for TCP. For simultaneous reduction of TCP together with nitrate, TCP’s removal rate value increased 75% and 150%, respectively, when added glucose was increased from 0.4 mmol·L–1 to 0.5 mmol·L–1 and to 0.76 mmol·L–1. For comparison, the removal rate for nitrate increased by only 25% and 114% for the same added glucose. The relationship between their initial biodegradation rates versus their initial concentrations could be represented well with the Monod model, which quantified their half-maximum-rate concentration (KS value), and KS values for TCP, nitrate, and nitrite were larger with simultaneous reduction than independent reduction. The increases in KS are further evidence that competition for the electron donor led to mutual inhibition. For bioremediation of wastewater containing TCP and oxidized nitrogen, both reduction reactions should proceed more rapidly if the oxidized nitrogen is nitrite instead of nitrate and if readily biodegradable electron acceptor is augmented.

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Preparation and characterization of a novel microorganism embedding material for simultaneous nitrification and denitrification
Ming Zeng, Ping Li, Nan Wu, Xiaofang Li, Chang Wang
Front. Environ. Sci. Eng.. 2017, 11 (6): 15-.  
https://doi.org/10.1007/s11783-017-0961-3

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CD enhances the hydrophilic property of traditional PVA-SA gel solution.

CD increases the density of embedded microorganism and micro porosity of bead.

CD makes the maximum endogenous respiration rate being high.

30-1.7-CD contributes the highest total inorganic nitrogen removal efficiency.

Comamonas sp. mainly realize the simultaneous nitrification and denitrification.

A novel microorganism embedding material was prepared to enhance the biological nitrogen removal through simultaneous nitrification and denitrification. Polyvinyl alcohol (PVA), sodium alginate (SA) and cyclodextrin (CD) were used to compose gel bead with embedded activated sludge. The effects of temperature, CD addition and concentrations of PVA and SA on nitrogen removal were evaluated. Results show that the gel bead with CD addition at 30°C contributed to the highest nitrogen removal efficiency and nitrogen removal rate of 85.4% and 2.08 mg·(L·h)?1, respectively. Meanwhile, negligible NO3? and NO2? were observed, proving the occurrence of simultaneous nitrification and denitrification. The High-Throughput Sequencing confirms that the microbial community mainly contained Comamonadaceae in the proportion of 61.3%. Overall, CD increased gel bead’s porosity and resulted in the high specific endogenous respiration rate and high nitrogen removal efficiency, which is a favorable additional agent to the traditional embedding material.

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Impact of dissolved oxygen on the production of nitrous oxide in biological aerated filters
Qiang He, Yinying Zhu, Guo Li, Leilei Fan, Hainan Ai, Xiaoliu Huangfu, Hong Li
Front. Environ. Sci. Eng.. 2017, 11 (6): 16-.  
https://doi.org/10.1007/s11783-017-0964-0

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The dominant Cloacibacterium normanense may be responsible for N2O production.

N2O concentrations varied along the biofilm depth depending on the DO levels.

Low DO concentration leads to high N2O production rate.

Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and microelectrode technology were employed to evaluate the Nitrous oxide (N2O) production in biological aerated filters (BAFs) under varied dissolved oxygen (DO) concentrations during treating wastewater under laboratory scale. The average yield of gasous N2O showed more than 4-fold increase when the DO levels were reduced from 6.0 to 2.0 mg·L1, indicating that low DO may drive N2O generation. PCR-DGGE results revealed that Nitratifractor salsuginis were dominant and may be responsible for N2O emission from the BAFs system. While at a low DO concentration (2.0 mg·L1), Flavobacterium urocaniciphilum might play a role. When DO concentration was the limiting factor (reduced from 6.0 to 2.0 mg·L1) for nitrification, it reduced NO2-N oxidation as well as the total nitrification. The data from this study contribute to explain how N2O production changes in response to DO concentration, and may be helpful for reduction of N2O through regulation of DO levels.

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Optimization of microwave pretreatment of lignocellulosic waste for enhancing methane production: Hyacinth as an example
Bai-Hang Zhao, Jie Chen, Han-Qing Yu, Zhen-Hu Hu, Zheng-Bo Yue, Jun Li
Front. Environ. Sci. Eng.. 2017, 11 (6): 17-.  
https://doi.org/10.1007/s11783-017-0965-z

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The physical structure of hyacinth was disrupted by microwave pretreatment.

Methane production increased by 38.3% with microwave pretreatment.

The maximum methane production and maximum methane production rate were optimized.

Mechanism of enhanced methane production by microwave pretreatment was analyzed.

The effect of microwave pretreatment on the anaerobic degradation of hyacinth was investigated using response surface methodology (RSM). The components of lignin and the other constituents of hyacinth were altered by microwave pretreatment. Comparison of the near-infrared spectra of hyacinth pretreated by microwave irradiation and water-heating pretreatment revealed that no new compounds were generated during hyacinth pretreatment by microwave irradiation. Atomic force microscopy observations indicated that the physical structures of hyacinth were disrupted by microwave pretreatment. The yield of methane per gram of the microwave-irradiated substrate increased by 38.3% as compared to that of the substrate pretreated via water-heating. A maximum methane yield of 221 mL·g-sub–1 was obtained under the optimum pretreatment conditions (substrate concentration (PSC) = 20.1 g·L–1 and pretreatment time (PT) = 14.6 min) using RSM analysis. A maximum methane production rate of 0.76 mL·h–1·g-sub–1 was obtained by applying PSC= 9.5 g·L–1 and PT= 11 min. Interactive item coefficient analysis showed that methane production was dependent on the PSC and PT, separately, whereas the interactive effect of the PSC and PT on methane production was not significant. The same trend was also observed for the methane production rate.

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PM10 emissions from industrial coal-fired chain-grate boilers
Xinghua Li, Junzan Han, Lei Duan
Front. Environ. Sci. Eng.. 2017, 11 (6): 18-.  
https://doi.org/10.1007/s11783-017-0966-y

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PM in submicron mode emitted from raw coal burning contribute to 33 % of PM10.

PM in submicron mode from briquette coal burning contribute to 86 % of PM10.

Collection efficiency of muticlones and scrubbers is 34% for submicron particle.

Peak of submicron mode in normal operation period is larger than start-up period.

Industrial coal-fired boiler is an important air pollutant emission source in China. The chain-grate boiler is the most extensively used type of industrial coal-fired boiler. An electrical low-pressure impactor, and a Dekati® Low Pressure Impactor were applied to determine mass and number size distributions of PM10 at the inlet and the outlet of the particulate emission control devices at six coal-fired chain-grate boilers. The mass size distribution of PM10 generated from coal-fired chain-grate boilers generally displays a bimodal distribution that contains a submicron mode and a coarse mode. The PM in the submicron mode for burning with raw coal contributes to 33%±10 % of PM10 emissions, much higher than those for pulverized boilers. And the PM in the submicron mode for burning with briquette contributes up to 86 % of PM10 emissions. Multiclones and scrubbers are not efficient for controlling PM10 emission. Their average collection efficiencies for sub-micron particle and super-micron particle are 34% and 78%, respectively. Operating conditions of industrial steam boilers have influence on PM generation. Peak of the submicron mode during normal operation period is larger than the start-up period.

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Improvement of sludge dewaterability with modified cinder via affecting EPS
Weichao Ma, Lei Zhao, Huiling Liu, Qianliang Liu, Jun Ma
Front. Environ. Sci. Eng.. 2017, 11 (6): 19-.  
https://doi.org/10.1007/s11783-017-0967-x

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The organic matters decreased during the conditioning with cinders.

The modified cinder could improve the dewaterability via affecting EPS.

Variation of EPS disintegrated sludge floc especially for ACMC addition.

ACMC promoted the reconstruction of sludge floc as skeleton builder via adsorption.

The reconstruction mechanisms included charge neutralization, adsorption bridging.

The relationship between the improvement of sludge dewaterability and variation of organic matters has been studied in the process of sludge pre-conditioning with modified cinder, especially for extracellular polymeric substances (EPS) in the sludge. During the conditioning process, the decreases of total organic carbon (TOC) and soluble chemical oxygen demand (SCOD) were obviously in the supernatant especially for the acid modified cinder (ACMC), which could be attributed to the processes of adsorption and sweeping. The reduction of polysaccharide and protein in supernatant indicated that ACMC might adsorb EPS so that the tightly bound EPS (TB-EPS) decreased in sludge. In the case of ACMC addition with 24 g·L−1, SRF of the sludge decreased from 7.85 × 1012 m·kg−1 to 2.06 × 1012 m·kg−1, and the filter cake moisture decreased from 85% to 60%. The reconstruction of “floc mass” was confirmed as the main sludge conditioning mechanism. ACMC promoted the dewatering performance through the charge neutralization and adsorption bridging with the negative EPS, and provided firm and dense structure for sludge floc as skeleton builder. The passages for water quick transmitting were built to avoid collapsing during the high-pressure process.

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Role of membrane and compound properties in affecting the rejection of pharmaceuticals by different RO/NF membranes
Yang-ying Zhao, Fan-xin Kong, Zhi Wang, Hong-wei Yang, Xiao-mao Wang, Yuefeng F. Xie, T. David Waite
Front. Environ. Sci. Eng.. 2017, 11 (6): 20-.  
https://doi.org/10.1007/s11783-017-0975-x

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Rejection of pharmaceuticals (PhACs) followed the order NF90 ≈ ESPA1>NF270>HL.

Electrostatic effect had an important role in PhAC rejection by loose NF membranes.

Effect of adsorption on rejection followed the order HL>ESPA1>NF270>NF90.

High hydrogen bond formation potential of PhACs impaired the rejection by HL.

This study was conducted to assess the merits and limitations of various high-pressure membranes, tight nanofiltration (NF) membranes in particular, for the removal of trace organic compounds (TrOCs). The performance of a low-pressure reverse osmosis (LPRO) membrane (ESPA1), a tight NF membrane (NF90) and two loose NF membranes (HL and NF270) was compared for the rejection of 23 different pharmaceuticals (PhACs). Efforts were also devoted to understand the effect of adsorption on the rejection performance of each membrane. Difference in hydrogen bond formation potential (HFP) was taken into consideration. Results showed that NF90 performed similarly to ESPA1 with mean rejection higher than 95%. NF270 outperformed HL in terms of both water permeability and PhAC rejection higher than 90%. Electrostatic effects were more significant in PhAC rejection by loose NF membranes than tight NF and LPRO membranes. The adverse effect of adsorption on rejection by HL and ESPA1 was more substantial than NF270 and NF90, which could not be simply explained by the difference in membrane surface hydrophobicity, selective layer thickness or pore size. The HL membrane had a lower rejection of PhACs of higher hydrophobicity (log D>0) and higher HFP (>0.02). Nevertheless, the effects of PhAC hydrophobicity and HFP on rejection by ESPA1 could not be discerned. Poor rejection of certain PhACs could generally be explained by aspects of steric hindrance, electrostatic interactions and adsorption. High-pressure membranes like NF90 and NF270 have a high promise in TrOC removal from contaminated water.

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20 articles