Frontiers of Environmental Science & Engineering

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ISSN 2095-2201 (Print)
ISSN 2095-221X (Online)
CN 10-1013/X
Postal Subscription Code 80-973
Formerly Known as Frontiers of Environmental Science & Engineering in China
2019 Impact Factor: 4.053
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Redox reactions of iron and manganese oxides in complex systems Collection
Jianzhi Huang, Huichun Zhang
Front. Environ. Sci. Eng..  2020, 14 (5): 76.
Abstract   HTML   PDF (1089KB)

• Mechanisms of redox reactions of Fe- and Mn-oxides were discussed.

• Oxidative reactions of Mn- and Fe-oxides in complex systems were reviewed.

• Reductive reaction of Fe(II)/iron oxides in complex systems was examined.

• Future research on examining the redox reactivity in complex systems was suggested.

Conspectus Redox reactions of Fe- and Mn-oxides play important roles in the fate and transformation of many contaminants in natural environments. Due to experimental and analytical challenges associated with complex environments, there has been a limited understanding of the reaction kinetics and mechanisms in actual environmental systems, and most of the studies so far have only focused on simple model systems. To bridge the gap between simple model systems and complex environmental systems, it is necessary to increase the complexity of model systems and examine both the involved interaction mechanisms and how the interactions affected contaminant transformation. In this Account, we primarily focused on (1) the oxidative reactivity of Mn- and Fe-oxides and (2) the reductive reactivity of Fe(II)/iron oxides in complex model systems toward contaminant degradation. The effects of common metal ions such as Mn2+ , Ca2+, Ni2+, Cr3+ and Cu2+, ligands such as small anionic ligands and natural organic matter (NOM), and second metal oxides such as Al, Si and Ti oxides on the redox reactivity of the systems are briefly summarized.

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Magnetotactic bacteria: Characteristics and environmental applications
Xinjie Wang, Yang Li, Jian Zhao, Hong Yao, Siqi Chu, Zimu Song, Zongxian He, Wen Zhang
Front. Environ. Sci. Eng..  2020, 14 (4): 56.
Abstract   HTML   PDF (1268KB)

• Magnetotactic bacteria (MTB) synthesize magnetic nanoparticle within magnetosomes.

• The morphologic and phylogenetic diversity of MTB were summarized.

• Isolation and mass cultivation of MTB deserve extensive research for applications.

• MTB can remove heavy metals, radionuclides, and organic pollutants from wastewater.

Magnetotactic bacteria (MTB) are a group of Gram-negative prokaryotes that respond to the geomagnetic field. This unique property is attributed to the intracellular magnetosomes, which contains membrane-bound nanocrystals of magnetic iron minerals. This review summarizes the most recent advances in MTB, magnetosomes, and their potential applications especially the environmental pollutant control or remediation. The morphologic and phylogenetic diversity of MTB were first introduced, followed by a critical review of isolation and cultivation methods. Past research has devoted to optimize the factors, such as oxygen, carbon source, nitrogen source, nutrient broth, iron source, and mineral elements for the growth of MTB. Besides the applications of MTB in modern biological and medical fields, little attention was made on the environmental applications of MTB for wastewater treatment, which has been summarized in this review. For example, applications of MTB as adsorbents have resulted in a novel magnetic separation technology for removal of heavy metals or organic pollutants in wastewater. In addition, we summarized the current advance on pathogen removal and detection of endocrine disruptor which can inspire new insights toward sustainable engineering and practices. Finally, the new perspectives and possible directions for future studies are recommended, such as isolation of MTB, genetic modification of MTB for mass production and new environmental applications. The ultimate objective of this review is to promote the applications of MTB and magnetosomes in the environmental fields.

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Identifying factors that influence soil heavy metals by using categorical regression analysis: A case study in Beijing, China
Jun Yang, Jingyun Wang, Pengwei Qiao, Yuanming Zheng, Junxing Yang, Tongbin Chen, Mei Lei, Xiaoming Wan, Xiaoyong Zhou
Front. Environ. Sci. Eng..  2020, 14 (3): 37.
Abstract   HTML   PDF (6214KB)

• A method was proposed to identify the main influence factors of soil heavy metals.

• The influence degree of different environmental factors was ranked.

• Parent material, soil type, land use and industrial activity were main factors.

• Interactions between some factors obviously affected soil heavy metal distribution.

Identifying the factors that influence the heavy metal contents of soil could reveal the sources of soil heavy metal pollution. In this study, a categorical regression was used to identify the factors that influence soil heavy metals. First, environmental factors were associated with soil heavy metal data, and then, the degree of influence of different factors on the soil heavy metal contents in Beijing was analyzed using a categorical regression. The results showed that the soil parent material, soil type, land use type, and industrial activity were the main influencing factors, which suggested that these four factors were important sources of soil heavy metals in Beijing. In addition, population density had a certain influence on the soil Pb and Zn contents. The distribution of soil As, Cd, Pb, and Zn was markedly influenced by interactions, such as traffic activity and land use type, industrial activity and population density. The spatial distribution of soil heavy metal hotspots corresponded well with the influencing factors, such as industrial activity, population density, and soil parent material. In this study, the main factors affecting soil heavy metals were identified, and the degree of their influence was ranked. A categorical regression represents a suitable method for identifying the factors that influence soil heavy metal contents and could be used to study the genetic process of regional soil heavy metal pollution.

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Cited: WebOfScience(2)
Enhanced carbon tetrachloride degradation by hydroxylamine in ferrous ion activated calcium peroxide in the presence of formic acid
Wenchao Jiang, Ping Tang, Zhen Liu, Huan He, Qian Sui, Shuguang Lyu
Front. Environ. Sci. Eng..  2020, 14 (2): 18.
Abstract   HTML   PDF (769KB)

• Complete CT degradation was achieved by employing HA to CP/Fe(II)/FA process.

• Quantitative detection of Fe(II) regeneration and HO• production was investigated.

• Benzoic acid outcompeted FA for the reaction with HO•.

• CO2 was the dominant reductive radical for CT removal.

• Effects of solution matrix on CT removal were conducted.

Hydroxyl radicals (HO•) show low reactivity with perchlorinated hydrocarbons, such as carbon tetrachloride (CT), in conventional Fenton reactions, therefore, the generation of reductive radicals has attracted increasing attention. This study investigated the enhancement of CT degradation by the synergistic effects of hydroxylamine (HA) and formic acid (FA) (initial [CT] = 0.13 mmol/L) in a Fe(II) activated calcium peroxide (CP) Fenton process. CT degradation increased from 56.6% to 99.9% with the addition of 0.78 mmol/L HA to the CP/Fe(II)/FA/CT process in a molar ratio of 12/6/12/1. The results also showed that the presence of HA enhanced the regeneration of Fe(II) from Fe(III), and the production of HO• increased one-fold when employing benzoic acid as the HO• probe. Additionally, FA slightly improves the production of HO•. A study of the mechanism confirmed that the carbon dioxide radical (CO2), a strong reductant generated by the reaction between FA and HO•, was the dominant radical responsible for CT degradation. Almost complete CT dechlorination was achieved in the process. The presence of humic acid and chloride ion slightly decreased CT removal, while high doses of bicarbonate and high pH inhibited CT degradation. This study helps us to better understand the synergistic roles of FA and HA for HO• and CO2 generation and the removal of perchlorinated hydrocarbons in modified Fenton systems.

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Increasing prevalence of antibiotic resistance genes in manured agricultural soils in northern China
Nan Wu, Weiyu Zhang, Shiyu Xie, Ming Zeng, Haixue Liu, Jinghui Yang, Xinyuan Liu, Fan Yang
Front. Environ. Sci. Eng..  2020, 14 (1): 1.
Abstract   HTML   PDF (1062KB)

• Manure application increased the abundances of ARGs and MGEs in agricultural soils.

• Five classes of ARGs and two MGEs were prevalent in manured and unfertilized soils.

• Genera Pseudomonas and Bacteroidetes might be the dominant hosts of intI1 and ermF.

• The abundances of ARGs positively correlated with TC, TN, OM, Cu, Zn, Pb and MGEs.

Land application of manure tends to result in the dissemination of antibiotic resistance in the environment. In this study, the influence of long-term manure application on the enrichment of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in agricultural soils was investigated. All the analyzed eight ARGs (tetA, tetW, tetX, sulI, sulII, ermF, aac(6’)-Ib-cr and blaTEM) and two MGEs (intI1 and Tn916/1545) were detected in both the manured and control soils, with relative abundances ranging from 10-6 to 10-2. Compared with the control soil, the relative abundances of ARGs and MGEs in manured soils were enriched 1.0–18.1 fold and 0.6–69.1 fold, respectively. High-throughput sequencing analysis suggested that at the phylum level, the bacteria carrying intI1 and ermF might be mainly affiliated with Proteobacteria and Bacteroides, respectively. The dominant genera carrying intI1 and ermF could be Pseudomonas and Bacteroides, independent of manure application. Correlation analysis revealed that ARGs had strong links with soil physicochemical properties (TC, TN, and OM), heavy metals (Cu, Zn and Pb) and MGEs, indicating that the profile and spread of ARGs might be driven by the combined impacts of multiple factors. In contrast, soil pH and C/N exhibited no significant relationships with ARGs. Our findings provide evidence that long-term manure application could enhance the prevalence and stimulate the propagation of antibiotic resistance in agricultural soils.

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Cited: WebOfScience(4)
G-CNTs/PVDF mixed matrix membranes with improved antifouling properties and filtration performance Collection
Xiaoyan Guo, Chunyu Li, Chenghao Li, Tingting Wei, Lin Tong, Huaiqi Shao, Qixing Zhou, Lan Wang, Yuan Liao
Front. Environ. Sci. Eng..  2019, 13 (6): 81.
Abstract   HTML   PDF (1819KB)

A novel nanocomposite OMWCNT-A-GO was synthesized by conjugating OMWCNT and GO.

The P-OMWCNT-A-GO membrane was fabricated by non-solvent induced phase inversion.

The P-OMWCNT-A-GO exhibits the best water flux, BSA rejection and flux recovery.

It should be due to the enhanced membrane pore size, porosity and hydrophilicity.

Although carbon nanomaterials have been widely used as effective nanofillers for fabrication of mixed matrix membranes (MMMs) with outstanding performances, the reproducibility of the fabricated MMMs is still hindered by the non-homogenous dispersion of these carbon nanofillers in membrane substrate. Herein, we report an effective way to improve the compatibility of carbon-based nanomaterials with membrane matrixes. By chemically conjugating the oxidized CNTs (o-CNTs) and GO using hexanediamine as cross-linker, a novel carbon nanohybrid material (G-CNTs) was synthesized, which inherited both the advanced properties of multi-walled carbon nanotubes (CNTs) and graphene oxide (GO). The G-CNTs incorporated polyvinylidene fluoride (PVDF) MMMs (G-CNTs/PVDF) were fabricated via a non-solvent induced phase separation (NIPS) method. The filtration and antifouling performances of G-CNTs/PVDF were evaluated using distillate water and a 1 g/L bovine serum albumin (BSA) aqueous solution under 0.10 MPa. Compared to the MMMs prepared with o-CNTs, GO, the physical mixture of o-CNTs and GO and pure PVDF membrane, the G-CNTs/PVDF membrane exhibited the highest water flux up to 220 L/m2/h and a flux recovery ratio as high as 90%, as well as the best BSA rejection rate. The excellent performances should be attributed to the increased membrane pore size, porosity and hydrophilicity of the resulted membrane. The successful synthesis of the novel nanohybrid G-CNTs provides a new type of nanofillers for MMMs fabrication.

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Cited: WebOfScience(6)
Oxidant or catalyst for oxidation? The role of manganese oxides in the activation of peroxymonosulfate (PMS)
Jianzhi Huang, Huichun Zhang
Front. Environ. Sci. Eng..  2019, 13 (5): 65.
Abstract   HTML   PDF (371KB)

Manganese oxides (MnOx) have been demonstrated to be effective materials to activate Oxone (i.e., PMS) to degrade various contaminants. However, the contribution of direct oxidation by MnOx to the total contaminant degradation under acidic conditions was often neglected in the published work, which has resulted in different and even conflicting interpretations of the reaction mechanisms. Here, the role of MnOx (as both oxidants and catalysts) in the activation of Oxone was briefly discussed. The findings offered new insights into the reaction mechanisms in PMS-MnOx and provided a more accurate approach to examine contaminant degradation for water/wastewater treatment.

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Cited: WebOfScience(4)
Combined Fenton process and sulfide precipitation for removal of heavy metals from industrial wastewater: Bench and pilot scale studies focusing on in-depth thallium removal
Huosheng Li, Hongguo Zhang, Jianyou Long, Ping Zhang, Yongheng Chen
Front. Environ. Sci. Eng..  2019, 13 (4): 49.
Abstract   HTML   PDF (2023KB)

Addition of alkali to pH 10 is effective for precipitation of precipitable metals.

Fenton treatment is effective for substantial removal of Tl, Cd, Cu, Pb, and Zn.

Sulfide precipitation is a final step for removal of trace Tl, Cd, Cu, Pb, and Zn.

Bench and pilot studies demonstrated the effectiveness of this combined technique.

Thallium (Tl) in industrial wastewater is a public health concern due to its extremely high toxicity. However, there has been limited research regarding Tl removal techniques and engineering practices to date. In this investigation, bench and pilot studies on advanced treatment of industrial wastewater to remove Tl to a trace level were conducted. The treatment process involved a combination of hydroxide precipitation, Fenton oxidation, and sulfide precipitation. While hydroxide precipitation was ineffective for Tl+ removal, it enabled the recovery of approximately 70%–80% of Zn as Zn hydroxide in alkaline conditions. The Fenton process provided good Tl removal (>95%) through oxidation and precipitation. Tl was then removed to trace levels (<1.0 µg/L) via sulfide precipitation. Effective removal of other heavy metals was also achieved, with Cd<13.4 µg/L, Cu<39.6 µg/L, Pb<5.32 µg/L, and Zn<357 µg/L detected in the effluent. X-ray photoelectron spectroscopy indicated that Tl2S precipitate formed due to sulfide precipitation. Other heavy metals were removed via the formation of metal hydroxides during hydroxide precipitation and Fenton treatment, as well as via the formation of metal sulfides during sulfide precipitation. This combined process provides a scalable approach for the in-depth removal of Tl and other heavy metals from industrial wastewater.

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Cited: Crossref(6) WebOfScience(16)
Influence of hydraulic retention time on behavior of antibiotics and antibiotic resistance genes in aerobic granular reactor treating biogas slurry Collection
Jie Liao, Chaoxiang Liu, Lin Liu, Jie Li, Hongyong Fan, Jiaqi Ye, Zhichao Zeng
Front. Environ. Sci. Eng..  2019, 13 (3): 31.
Abstract   HTML   PDF (1385KB)

Longer HRT can enhance degradation rate of sulfamethoxazole in granular reactor.

Longer HRT can reduce accumulated concentrations of TCs and QNs in sludge.

Longer HRT may have increased relative abundances of ARGs in aerobic granules.

The behavior of antibiotics and the corresponding resistance genes in aerobic granular reactors for treating biogas slurry under different hydraulic retention times (10.7 h, R1; 8 h, R2) was investigated in this study. The results indicated that the hydraulic retention time could affect the effluent concentrations and removal efficiencies of sulfonamides. The average removal rates of tetracyclines, fluoroquinolones, and sulfonamides were 63%, 46%, and 90% in R1, and 62%, 46%, and 86% in R2, respectively. Although the removal efficiencies of tetracyclines and fluoroquinolones were similar in both reactors, the respective accumulated concentrations of tetracyclines and fluoroquinolones in R1 were 7.00 and 11.15 µg/g SS, which were lower than those in R2 (8.92 and 13.37 µg/g SS, respectively). The difference in the relative abundance of target antibiotic resistance genes between both reactors was not significant, yet the average relative abundances of all target resistance genes in R1 were higher than those in R2 after 45 days of operation. The results of this study suggested that a longer hydraulic retention time could enhance the antibiotic removal ability of aerobic granular sludge, yet it may also increase the risk of surplus sludge utilization from a resistance genes point of view.

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Cited: WebOfScience(3)
Effective removal of Cd2+ and Pb2+ pollutants from wastewater by dielectrophoresis-assisted adsorption
Qinghao Jin, Chenyang Cui, Huiying Chen, Jing Wu, Jing Hu, Xuan Xing, Junfeng Geng, Yanhong Wu
Front. Environ. Sci. Eng..  2019, 13 (2): 16.
Abstract   HTML   PDF (353KB)

Dielectrophoresis (DEP) process could enhance the removal the Cd2+ and Pb2+ with less absorbent.

The removal rates of both Cd2+ and Pb2+ increased with the increase of voltage.

The overall removal rate of Cd2+ and Pb2+ in the binary system is higher than that of Cd2+ or Pb2+ in the single system.

DEP could cause considerable changes of the bentonite particles in both surface morphology and microstructure.

Dielectrophoresis (DEP) was combined with adsorption (ADS) to simultaneously and effectively remove Cd2+ and Pb2+ species from aqueous solution. To implement the process, bentonite particles of submicro-meter size were used to first adsorb the heavy metal ions. These particles were subsequently trapped and removed by DEP. The effects of the adsorbent dosage, DEP cell voltage and the capture pool numbers on the removal rate were investigated in batch processes, which allowed us to determine the optimal experimental conditions. The high removal efficiency, 97.3% and 99.9% for Cd2+ and Pb2+, respectively, were achieved when the ions are coexisting in the system. The microstructure of bentonite particles before and after ADS/DEP was examined by scanning electron microscopy. Our results suggest that the dielectrophoresis-assisted adsorption method has a high capability to remove the heavy metals from wastewater.

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Cited: Crossref(1) WebOfScience(3)
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