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Yang J, Zhang BT, Tian L, Die Q, Wang F, Fu H, Yang Y, Huang Q. Free radical formation via BDE-209 thermolysis in the precalciner of a cement kiln: Simulation and DFT study. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 905:167145. [PMID: 37730046 DOI: 10.1016/j.scitotenv.2023.167145] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 09/01/2023] [Accepted: 09/14/2023] [Indexed: 09/22/2023]
Abstract
To deeply understand the formation mechanism of polybrominated dibenzo-p-dioxins/furans (PBDD/Fs) in the thermal disposal process of polybrominated diphenyl ether (PBDE)-containing waste, this paper studied the formation pathways of key intermediates (free radicals, FRs) in the formation process of PBDD/Fs. BDE-209, the most common PBDE in the environment, was selected as the object of study to analyze FR formation by simulating the key conditions such as temperature (850 °C) and Fe-based materials when PBDE-containing waste entering cement kiln precalciner. Electron paramagnetic resonance (EPR) spectroscopy and density functional theory (DFT) calculations were used to study the reaction. The result of simulation experiments revealed carbon-centered radicals, and DMPO-OH analysis further confirmed the generation of FRs. The findings confirmed previous calculations predicting the existence of radical intermediates during the formation of PBDD/Fs from BDE-209. DFT calculations revealed the existence of an inner ortho-position CBr bond in BDE-209. The priority order of the bond breaking of BDE-209 was ether bond, inner ortho-position CBr bond, and outside ortho-position CBr bond. BDE-209 can further form three kinds of FRs, namely, oxygen-centered radicals of single benzene rings, carbon-centered radicals of single benzene rings, and carbon-centered radicals of double benzene rings. The specific processes of FR formation were inferred: high-temperature homogeneous cleavage of chemical bonds, electron transfer, and chemisorption, where electron transfer and chemisorption may be more important pathways. The proposed inner ortho-position cleavage within BDE-209 provides new insights into the degradation of PBDEs and the formation of PBDD/Fs; the results regarding BDE-209 generation radicals further elucidate the synthesis mechanism of dioxins, which is important for controlling dioxin generation and emission during the treatment and disposal of waste containing PBDEs.
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Affiliation(s)
- Jinzhong Yang
- State Key Laboratory of Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; State Environmental Protection Key Laboratory of Hazardous Waste Identification and Risk Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; College of Water Sciences, Beijing Normal University, Beijing 100875, China
| | - Bo-Tao Zhang
- College of Water Sciences, Beijing Normal University, Beijing 100875, China
| | - Lu Tian
- State Key Laboratory of Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; State Environmental Protection Key Laboratory of Hazardous Waste Identification and Risk Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Qingqi Die
- State Key Laboratory of Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; State Environmental Protection Key Laboratory of Hazardous Waste Identification and Risk Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Fei Wang
- State Key Laboratory of Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; State Environmental Protection Key Laboratory of Hazardous Waste Identification and Risk Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Haihui Fu
- State Key Laboratory of Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; State Environmental Protection Key Laboratory of Hazardous Waste Identification and Risk Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
| | - Yufei Yang
- State Key Laboratory of Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; State Environmental Protection Key Laboratory of Hazardous Waste Identification and Risk Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
| | - Qifei Huang
- State Key Laboratory of Environmental Benchmarks and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China; State Environmental Protection Key Laboratory of Hazardous Waste Identification and Risk Control, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
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Khan AUH, Naidu R, Dharmarajan R, Fang C, Shon H, Dong Z, Liu Y. The interaction mechanisms of co-existing polybrominated diphenyl ethers and engineered nanoparticles in environmental waters: A critical review. J Environ Sci (China) 2023; 124:227-252. [PMID: 36182134 DOI: 10.1016/j.jes.2021.10.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2021] [Revised: 10/13/2021] [Accepted: 10/13/2021] [Indexed: 06/16/2023]
Abstract
This review focuses on the occurrence and interactions of engineered nanoparticles (ENPs) and brominated flame retardants (BFRs) such as polybrominated diphenyl ethers (PBDEs) in water systems and the generation of highly complex compounds in the environment. The release of ENPs and BFRs (e.g. PBDEs) to aquatic environments during their usage and disposal are summarised together with their key interaction mechanisms. The major interaction mechanisms including electrostatic, van der Waals, hydrophobic, molecular bridging and steric, hydrogen and π-bonding, cation bridging and ligand exchange were identified. The presence of ENPs could influence the fate and behaviour of PBDEs through the interactions as well as induced reactions under certain conditions which increases the formation of complex compounds. The interaction leads to alteration of behaviour for PBDEs and their toxic effects to ecological receptors. The intermingled compound (ENPs-BFRs) would show different behaviour from the parental ENPs or BFRs, which are currently lack of investigation. This review provided insights on the interactions of ENPs and BFRs in artificial, environmental water systems and wastewater treatment plants (WWTPs), which are important for a comprehensive risk assessment.
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Affiliation(s)
- Anwar Ul Haq Khan
- Global Centre for Environmental Remediation (GCER), College of Engineering Science and Environment, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), ATC Building, The University of Newcastle, Callaghan, NSW 2308, Australia.
| | - Ravi Naidu
- Global Centre for Environmental Remediation (GCER), College of Engineering Science and Environment, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), ATC Building, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Raja Dharmarajan
- Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), ATC Building, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Cheng Fang
- Global Centre for Environmental Remediation (GCER), College of Engineering Science and Environment, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), ATC Building, The University of Newcastle, Callaghan, NSW 2308, Australia
| | - Hokyong Shon
- School of Civil and Environmental Engineering, University of Technology Sydney (UTS), City Campus, Broadway, NSW 2007, Australia
| | - Zhaomin Dong
- School of Space and Environment, Beihang University, Beijging 100191, China
| | - Yanju Liu
- Global Centre for Environmental Remediation (GCER), College of Engineering Science and Environment, The University of Newcastle, Callaghan, NSW 2308, Australia; Cooperative Research Centre for Contamination Assessment and Remediation of the Environment (CRC CARE), ATC Building, The University of Newcastle, Callaghan, NSW 2308, Australia.
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Yang J, Yu H, Xie Z, Yang Y, Zheng X, Zhang J, Huang Q, Wen T, Wang J. Pathways and influential factors study on the formation of PBDD/Fs during co-processing BDE-209 in cement kiln simulation system. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2020; 192:110246. [PMID: 32028153 DOI: 10.1016/j.ecoenv.2020.110246] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 01/19/2020] [Accepted: 01/22/2020] [Indexed: 06/10/2023]
Abstract
The thermal processes of cement kilns are sources of polybrominated dibenzofurans and dioxins (PBDD/Fs); however, when co-processing decabromodiphenyl ether (BDE-209) soil in cement kilns, very few reports have investigated the mechanism of PBDD/Fs formation from BDE-209. Therefore, the pathways and factors that influence the formation of PBDD/Fs were investigated using Box-Behnken design (BBD) of the response surface methodology (RSM) at lab-scale. The PBDEs, HBr/Br2 and PBDD/Fs emissions in flue gas from the simulated thermal process were analyzed using gas chromatography/mass spectroscopy (GC/MS), high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS), and ion chromatography (IC). Density functional theory (DFT) was also used to further discuss the formation of PBDD/Fs. The major products of BDE-209 thermal decomposition in flue gas were 97.1% HBr/Br2 (a.v. 26.6%/70.6%) > 2.7% PBDEs >0.2% PBDD/Fs. Formation of precursors were the main pathways for PBDD/Fs, and those precursors were dominated by higher-brominated PBDEs (heptã deca-BDEs); debromination of BDE-209 was also a crucial pathway for the formation of PBDD/Fs throughout the thermal process. Interestingly, it was easier to form HpBDD/Fs from OBDD/Fs than from PBDEs. The O2 percentage and interaction factors of O2 percentage, temperature, and CaCO3 percentage have the largest influence on PBDD/Fs emissions and formation.
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Affiliation(s)
- Jinzhong Yang
- College of Water Sciences, Beijing Normal University, Beijing, 100875, PR China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China.
| | - Haibin Yu
- China National Environmental Monitoring Centre, Beijing, 100012, PR China.
| | - Zhen Xie
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China.
| | - Yufei Yang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China.
| | - Xiaoyan Zheng
- China National Environmental Monitoring Centre, Beijing, 100012, PR China.
| | - Jingxing Zhang
- China National Environmental Monitoring Centre, Beijing, 100012, PR China.
| | - Qifei Huang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China.
| | - Tao Wen
- MOE Key Laboratory of Resources and Environmental System Optimization, College of Environmental Science and Engineering, North China Electric Power University, Beijing, 102206, PR China.
| | - Jianyuan Wang
- State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, PR China.
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Wei L, Zhou B, Xiao K, Yang B, Yu G, Li J, Zhu C, Zhang J, Duan H. Highly efficient degradation of 2,2',4,4'-tetrabromodiphenyl ether through combining surfactant-assisted Zn 0 reduction with subsequent Fenton oxidation. JOURNAL OF HAZARDOUS MATERIALS 2020; 385:121551. [PMID: 31708290 DOI: 10.1016/j.jhazmat.2019.121551] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Revised: 10/13/2019] [Accepted: 10/24/2019] [Indexed: 06/10/2023]
Abstract
2,2',4,4'-tetrabromodiphenyl ether (BDE47) was difficult to be rapidly degraded by common reductive debromination or oxidative decomposition. In this study, the debromination via surfactant-assisted zero valent zinc (Zn0) reduction and subsequent Fenton oxidation was combined to completely degrade BDE47. Firstly, Zn0 integrated with surfactants including cetyltrimethylammonium chloride (CTAC), polyethylene glycol dodecyl ether (Brij35), or 1-dodecanesulfonic acid sodium salt (SDS) were evaluated for their reactivity to debrominate BDE47. CTAC-assisted Zn0 system presented the highest removal efficiency of 98.6% for BDE47 (C0 = 5 mg/L) under the optimized conditions including 0.3 g/L of Zn0 particles and 0.05 g/L of CTAC at 25 °C and pH 4.0 during 1-h reaction. Subsequently, the debromination products as low-brominated BDEs were attacked by hydroxyl radicals (•OH) from Fenton reagent, which were decomposed into short-chain carboxylic acids and even mineralized within 2-h oxidation. In addition, HPLC, GC-MS, LC-MS/MS, and IC were employed to detect intermediates during this reaction/oxidation process and the pathways of debromination and oxidation were proposed according to carbon and bromine balance. The above combination achieved the complete degradation of BDE47 via a relative low-cost method to rapidly remove PBDEs, which provide a new approach for the effective treatment of halogenated organic pollutants.
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Affiliation(s)
- Liyan Wei
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, PR China
| | - Biao Zhou
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, PR China
| | - Ke Xiao
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, PR China
| | - Bo Yang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, PR China.
| | - Gang Yu
- School of Environment, POPs Research Center, Tsinghua University, Beijing 100084, PR China
| | - Juying Li
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, PR China
| | - Caizhen Zhu
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, PR China
| | - Junmin Zhang
- College of Chemistry and Environmental Engineering, Shenzhen University, Shenzhen 518060, PR China
| | - Huabo Duan
- Smart City Research Institute, College of Civil Engineering, Shenzhen University, Shenzhen 518060, PR China
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Wang R, Tang T, Feng S, Chen X, Dang D, Huang K, Tao X, Yin H, Dang Z, Lu G. Experimental and theoretical investigations on debromination pathways of polybrominated biphenyls (PBBs) under ultraviolet light. CHEMOSPHERE 2018; 212:1-7. [PMID: 30130655 DOI: 10.1016/j.chemosphere.2018.08.063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/27/2018] [Revised: 07/29/2018] [Accepted: 08/13/2018] [Indexed: 06/08/2023]
Abstract
Polybrominated biphenyls (PBBs) are brominated flame retardants that are widely used in textiles and electronic products. Recently, many researches have been devoted to determining their concentrations in food and in the environment. Yet, their degradation behavior has been less investigated and is not well understood. Here, we have investigated the debromination pathways of PBBs by (UV) light in the case of 2,4,5-tribrominated biphenyl (PBB-29). Our investigation indicates that para-bromine substituent on PBB-29 was preferentially removed. By means of density functional theory (DFT), we found that the energies of the debromination products, the CBr bond length in the excited state (S1), the Mulliken charge of bromine in S1, and the lowest unoccupied molecular orbital (LUMO) in S1 correlated well with the debromination pathways of PBBs. Further, LUMO-based prediction of PBB debromination pathways in S1 suggests that the bromine substituent on all brominated positions (i.e. ortho-, meta- and para-) can be preferentially removed, as the debromination sequence is not based on the brominated position but on the specific brominated arrangement pattern. In addition, reductive debromination preferentially occurs on the benzene ring that has the highest number of bromine substituents. This study provided useful descriptors to predict the debromination pathways of PBBs, and the theoretical result greatly improve our understanding of photolytic debromination of PBBs.
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Affiliation(s)
- Rui Wang
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Ting Tang
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Siyuan Feng
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Xingwei Chen
- School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China
| | - Dai Dang
- School of Chemical Engineering and Light Industry, Guangdong University of Technology, Guangzhou 510006, China
| | - Kaibo Huang
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China
| | - Xueqin Tao
- College of Environmental Science and Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China
| | - Hua Yin
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou, 510006, China
| | - Zhi Dang
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou, 510006, China
| | - Guining Lu
- School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou, 510006, China.
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Lei M, Guo S, Wang Z, Zhu L, Tang H. Ultrarapid and Deep Debromination of Tetrabromodiphenyl Ether over Noble-Metal-Free Cu/TiO 2 Nanocomposites under Mild Conditions. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2018; 52:11743-11751. [PMID: 30207447 DOI: 10.1021/acs.est.8b03202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Fast and deep debromination of polybrominated diphenyl ethers (PBDEs) under mild conditions is a challenge in the field of pollution control. A strategy was developed to achieve it by exploiting Cu/TiO2 composites as a noble-metal-free catalyst. Toward the debromination of 2,2',4,4'-tetrabromodiphenyl ether (BDE47) as a typical PBDE, the use of Cu/TiO2 as a catalyst and hydrazine hydrate (N2H4·H2O) as a reducing agent yielded a degradation removal of 100% and a debromination efficiency of 87.7% in 3 s. A complete debromination of BDE47 at 1500 mg L-1 was possible by successively adding N2H4·H2O. A debromination pathway involving active H atom species was proposed for the catalytic transfer hydrogenation (CTH) of PBDEs according to the identified degradation intermediates. A mechanism was further clarified by density functional theory calculations: electrons are delivered from N2H4·H2O to the metallic Cu atom via a coordination of N in N2H4·H2O with Cu atoms. The electron-trapped Cu atom interacts with adsorbed BDE47 to form a transition complex, and then the debromination of this complex occurs on the surface of Cu nanoparticles due to the hydrogen donation of N2H4·H2O through the CTH process. The new method provides a highly efficient method to remove brominated pollutants.
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Affiliation(s)
- Ming Lei
- Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science , South-Central University for Nationalities , Wuhan 430074 , People's Republic of China
| | - Shun Guo
- School of Chemistry and Chemical Engineering , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China
| | - Zhiying Wang
- Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science , South-Central University for Nationalities , Wuhan 430074 , People's Republic of China
| | - Lihua Zhu
- School of Chemistry and Chemical Engineering , Huazhong University of Science and Technology , Wuhan 430074 , People's Republic of China
| | - Heqing Tang
- Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Resources and Environmental Science , South-Central University for Nationalities , Wuhan 430074 , People's Republic of China
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Tang T, Lu G, Wang R, Chen H, Fang Y, Huang K, Zheng J, Zou M, Tao X, Yin H, Dang Z. Debromination of polybrominated diphenyl ethers (PBDEs) by zero valent zinc: Mechanisms and predicting descriptors. JOURNAL OF HAZARDOUS MATERIALS 2018; 352:165-171. [PMID: 29609148 DOI: 10.1016/j.jhazmat.2018.03.038] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/30/2017] [Revised: 03/15/2018] [Accepted: 03/20/2018] [Indexed: 06/08/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) are a class of brominated flame retardants that are ubiquitous in the environment. The physical and chemical properties of PBDEs make them difficult to degrade, with the conventional remediation methods being relatively inefficient. In this study, the reactivity of zero valent zinc (ZVZ) toward 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) was evaluated under aqueous solution. First-order rate constants (kobs) for BDE-47 disappearance increased with decreased pH, which is attributed to the dissolution of surface zinc oxides that promote the contact between the active site on zinc surface and BDE molecules. The kobs of ten investigated PBDEs in ZVZ system are positively correlated with the energy of lowest unoccupied orbitals (ELUMO) of PBDEs (R2 = 0.902). The debromination pathways of BDE-47 in ZVZ system are: BDE-47 → BDE-28 → BDE-15 → BDE-3 → DE, which is the same to the debromination pathways of BDE-47 in zero valent iron (ZVI) in previous study. In addition, the singly occupied molecular orbitals (SOMOs) of the BDE anions can well reflect the actual debromination pathways of PBDEs by comparing the size of the CBr antibonding characterized lobes. Our results suggest that the debromination of PBDEs by ZVZ is based on the electron transfer mechanism, and the SOMOs of BDE anions can be used to predict the debromination pathways of untested PBDEs.
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Affiliation(s)
- Ting Tang
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Guining Lu
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China; Guangdong Provincial Engineering and Technology Research Center for Environmental Risk Prevention and Emergency Disposal, Guangzhou, 510006, China.
| | - Rui Wang
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Huan Chen
- School of Environmental Science and Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou, 510225, China
| | - Yingcong Fang
- School of Pharmaceutical Science and Technology, Dalian University of Technology, Dalian, 116012, China
| | - Kaibo Huang
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Jiayi Zheng
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Mengyao Zou
- School of Environmental Science and Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou, 510225, China
| | - Xueqin Tao
- School of Environmental Science and Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou, 510225, China
| | - Hua Yin
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China
| | - Zhi Dang
- School of Environment and Energy, South China University of Technology, Guangzhou, 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China
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Wang S, Chen S, Wang Y, Low A, Lu Q, Qiu R. Integration of organohalide-respiring bacteria and nanoscale zero-valent iron (Bio-nZVI-RD): A perfect marriage for the remediation of organohalide pollutants? Biotechnol Adv 2016; 34:1384-1395. [DOI: 10.1016/j.biotechadv.2016.10.004] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Revised: 09/18/2016] [Accepted: 10/15/2016] [Indexed: 12/19/2022]
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Li L, Hu J, Shi X, Fan M, Luo J, Wei X. Nanoscale zero-valent metals: a review of synthesis, characterization, and applications to environmental remediation. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2016; 23:17880-900. [PMID: 27094266 DOI: 10.1007/s11356-016-6626-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2016] [Accepted: 04/04/2016] [Indexed: 05/21/2023]
Abstract
Engineered nanoscale zero-valent metals (NZVMs) representing the forefront of technologies have been considered as promising materials for environmental remediation and antimicrobial effect, due to their high reducibility and strong adsorption capability. This review is focused on the methodology for synthesis of bare NZVMs, supported NZVMs, modified NZVMs, and bimetallic systems with both traditional and green methods. Recent studies have demonstrated that self-assembly methods can play an important role for obtaining ordered, controllable, and tunable NZVMs. In addition to common characterization methods, the state-of-the-art methods have been developed to obtain the properties of NZVMs (e.g., granularity, size distribution, specific surface area, shape, crystal form, and chemical bond) with the resolution down to subnanometer scale. These methods include spherical aberration corrected scanning transmission electron microscopy (Cs-corrected STEM), electron energy-loss spectroscopy (EELS), and near edge X-ray absorption fine structure (NEXAFS). A growing body of experimental data has proven that nanoscale zero-valent iron (NZVI) is highly effective and versatile. This article discusses the applications of NZVMs to treatment of heavy metals, halogenated organic compounds, polycyclic aromatic hydrocarbons, nutrients, radioelements, and microorganisms, using both ex situ and in situ methods. Furthermore, this paper briefly describes the ecotoxicological effects for NZVMs and the research prospects related to their synthesis, modification, characterization, and applications.
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Affiliation(s)
- Lingyun Li
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001, People's Republic of China
| | - Jiwei Hu
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001, People's Republic of China.
| | - Xuedan Shi
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001, People's Republic of China
| | - Mingyi Fan
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001, People's Republic of China
| | - Jin Luo
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, 550001, People's Republic of China
| | - Xionghui Wei
- Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, People's Republic of China
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10
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Li L, Hu J, Shi X, Ruan W, Luo J, Wei X. Theoretical Studies on Structures, Properties and Dominant Debromination Pathways for Selected Polybrominated Diphenyl Ethers. Int J Mol Sci 2016; 17:ijms17060927. [PMID: 27322242 PMCID: PMC4926460 DOI: 10.3390/ijms17060927] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 06/01/2016] [Accepted: 06/03/2016] [Indexed: 12/03/2022] Open
Abstract
The B3LYP/6-311+G(d)-SDD method, which considers the relativistic effect of bromine, was adopted for the calculations of the selected polybrominated diphenyl ethers (PBDEs) in the present study, in which the B3LYP/6-311+G(d) method was also applied. The calculated values and experimental data for structural parameters of the selected PBDEs were compared to find the suitable theoretical methods for their structural optimization. The results show that the B3LYP/6-311+G(d) method can give the better results (with the root mean square errors (RMSEs) of 0.0268 for the C–Br bond and 0.0161 for the C–O bond) than the B3LYP/6-311+G(d)-SDD method. Then, the B3LYP/6-311+G(d) method was applied to predict the structures for the other selected PBDEs (both neutral and anionic species). The lowest unoccupied molecular orbital (LUMO) and the electron affinity are of a close relationship. The electron affinities (vertical electron affinity and adiabatic electron affinity) were discussed to study their electron capture abilities. To better estimate the conversion of configuration for PBDEs, the configuration transition states for BDE-5, BDE-22 and BDE-47 were calculated at the B3LYP/ 6-311+G(d) level in both gas phase and solution. The possible debromination pathway for BDE-22 were also studied, which have bromine substituents on two phenyl rings and the bromine on meta-position prefers to depart from the phenyl ring. The reaction profile of the electron-induced reductive debromination for BDE-22 were also shown in order to study its degradation mechanism.
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Affiliation(s)
- Lingyun Li
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
| | - Jiwei Hu
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
| | - Xuedan Shi
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
| | - Wenqian Ruan
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
| | - Jin Luo
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
| | - Xionghui Wei
- Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
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Lei M, Wang N, Zhu L, Tang H. Peculiar and rapid photocatalytic degradation of tetrabromodiphenyl ethers over Ag/TiO2 induced by interaction between silver nanoparticles and bromine atoms in the target. CHEMOSPHERE 2016; 150:536-544. [PMID: 26546118 DOI: 10.1016/j.chemosphere.2015.10.048] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2015] [Revised: 09/23/2015] [Accepted: 10/13/2015] [Indexed: 06/05/2023]
Abstract
As a typical moderately-brominated diphenylethers, 2,2',4,4'-tetrabromodiphenyl ether (BDE47) is hardly debrominated by a conventional TiO2-mediated photocatalysis. However, its reductive debromination was rapid achieved over silver nanoparticle-loaded TiO2 (Ag/TiO2) in UV-irradiated anoxic acetonitrile-water within 13 min. An "Ag-promoted electron transfer and C-Br cleavage" concept was proposed based on experimental results and density functional theory calculations. Ag(0) exerted affinity interaction with bromine atoms, and the storing of electrons on Ag(0) increased the binding interaction, which elongated the C-Br bond of BDE47 and facilitated its cleavage. The initiating of the BDE47 debromination on Ag(0) required an induction period to enrich a critical amount of electrons, leading to a stronger driving force for both injecting electron to BDE47 and stretching the C-Br bond. Stronger photo-excitation, higher polar solvent, and a moderate Ag(0) load strengthened the interfacial electron transfer over Ag/TiO2, and thereby shortening the induction time and accelerating the BDE47 degradation.
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Affiliation(s)
- Ming Lei
- College of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, PR China
| | - Nan Wang
- College of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, PR China.
| | - Lihua Zhu
- College of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, 430074, PR China
| | - Heqing Tang
- Key Laboratory of Catalysis and Materials Science of the State Ethnic Affairs Commission and Ministry of Education, College of Chemistry and Materials Science, South-Central University for Nationalities, Wuhan, 430074, PR China
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12
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Santos MSF, Alves A, Madeira LM. Chemical and photochemical degradation of polybrominated diphenyl ethers in liquid systems - A review. WATER RESEARCH 2016; 88:39-59. [PMID: 26465809 DOI: 10.1016/j.watres.2015.09.044] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2015] [Revised: 07/24/2015] [Accepted: 09/27/2015] [Indexed: 06/05/2023]
Abstract
Polybrominated diphenyl ethers (PBDEs) are brominated flame retardants which have received a great deal of attention due to their persistence, potential to bioaccumulate and possible toxic effects. PBDEs have been globally detected in humans, wildlife and environment, highlighting the urgency of looking for effective removal technologies to mitigate their spread and accumulation in the environment. Among all environmental compartments, the water has raised particular attention. This paper aims to provide information about the suitability of the main degradation processes investigated to date (photolysis, zerovalent iron and TiO2 photocatalysis) for the degradation of PBDEs in water matrices. The most relevant criteria behind the design of a system for such purpose are discussed in detail for each individual process. The comparative analysis suggests that the oxidative degradation by TiO2 is the most appropriated technology to treat waters contaminated with PBDEs because higher debromination and mineralization degrees are achieved, preventing the formation/accumulation of lower brominated PBDE congeners and promoting the cracking of aromatic cores.
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Affiliation(s)
- Mónica S F Santos
- LEPABE - Laboratory for Process, Environmental, Biotechnology and Energy Engineering, Faculty of Engineering, University of Porto, R. Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal.
| | - Arminda Alves
- LEPABE - Laboratory for Process, Environmental, Biotechnology and Energy Engineering, Faculty of Engineering, University of Porto, R. Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal
| | - Luis M Madeira
- LEPABE - Laboratory for Process, Environmental, Biotechnology and Energy Engineering, Faculty of Engineering, University of Porto, R. Dr. Roberto Frias, s/n, 4200-465 Porto, Portugal.
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Luo J, Hu J, Wei X, Fu L, Li L. Dehalogenation of persistent halogenated organic compounds: A review of computational studies and quantitative structure-property relationships. CHEMOSPHERE 2015; 131:17-33. [PMID: 25765260 DOI: 10.1016/j.chemosphere.2015.02.013] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2014] [Revised: 12/20/2014] [Accepted: 02/03/2015] [Indexed: 06/04/2023]
Abstract
Dehalogenation is one of the highly important degradation reactions for halogenated organic compounds (HOCs) in the environment, which is also being developed as a potential type of the remediation technologies. In combination with the experimental results, intensive efforts have recently been devoted to the development of efficient theoretical methodologies (e.g. multi-scale simulation) to investigate the mechanisms for dehalogenation of HOCs. This review summarizes the structural characteristics of neutral molecules, anionic species and excited states of HOCs as well as their adsorption behavior on the surface of graphene and the Fe cluster. It discusses the key physiochemical properties (e.g. frontier orbital energies and thermodynamic properties) calculated at various levels of theory (e.g. semiempirical, ab initio, density functional theory (DFT) and the periodic DFT) as well as their connections to the reactivity and reaction pathway for the dehalogenation. This paper also reviews the advances in the linear and nonlinear quantitative structure-property relationship models for the dehalogenation kinetics of HOCs and in the mathematical modeling of the dehalogenation processes. Furthermore, prospects of further expansion and exploration of the current research fields are described in this article.
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Affiliation(s)
- Jin Luo
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, PR China
| | - Jiwei Hu
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, PR China.
| | - Xionghui Wei
- Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, PR China
| | - Liya Fu
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, PR China
| | - Lingyun Li
- Guizhou Provincial Key Laboratory for Information Systems of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, PR China
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Luo J, Hu J, Wei X, Li L, Huang X. Excited States and photodebromination of selected polybrominated diphenyl ethers: computational and quantitative structure--property relationship studies. Int J Mol Sci 2015; 16:1160-78. [PMID: 25569092 PMCID: PMC4307296 DOI: 10.3390/ijms16011160] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2014] [Accepted: 12/24/2014] [Indexed: 12/16/2022] Open
Abstract
This paper presents a density functional theory (DFT)/time-dependent DFT (TD-DFT) study on the lowest lying singlet and triplet excited states of 20 selected polybrominateddiphenyl ether (PBDE) congeners, with the solvation effect included in the calculations using the polarized continuum model (PCM). The results obtained showed that for most of the brominated diphenyl ether (BDE) congeners, the lowest singlet excited state was initiated by the electron transfer from HOMO to LUMO, involving a π–σ* excitation. In triplet excited states, structure of the BDE congeners differed notably from that of the BDE ground states with one of the specific C–Br bonds bending off the aromatic plane. In addition, the partial least squares regression (PLSR), principal component analysis-multiple linear regression analysis (PCA-MLR), and back propagation artificial neural network (BP-ANN) approaches were employed for a quantitative structure-property relationship (QSPR) study. Based on the previously reported kinetic data for the debromination by ultraviolet (UV) and sunlight, obtained QSPR models exhibited a reasonable evaluation of the photodebromination reactivity even when the BDE congeners had same degree of bromination, albeit different patterns of bromination.
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Affiliation(s)
- Jin Luo
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
| | - Jiwei Hu
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
| | - Xionghui Wei
- Department of Applied Chemistry, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
| | - Lingyun Li
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
| | - Xianfei Huang
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang 550001, China.
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15
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Gan N, Zhang J, Lin S, Long N, Li T, Cao Y. A Novel Magnetic Graphene Oxide Composite Absorbent for Removing Trace Residues of Polybrominated Diphenyl Ethers in Water. MATERIALS 2014; 7:6028-6044. [PMID: 28788175 PMCID: PMC5456175 DOI: 10.3390/ma7086028] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 05/29/2014] [Accepted: 08/08/2014] [Indexed: 11/30/2022]
Abstract
The purpose of the study was to develop a facile method for the fabrication of a stable and reusable magnetic graphene composite absorbent to remove trace levels of polybrominated diphenyl ethers in water treatment. The poly cationic Fe3O4@PDDA (poly(diallyldimethyl ammonium chloride) (PDDA)) core-shell structured nanoparticles were first synthesized, and then, DNA was laid on the surface of graphene oxide (GOx) to prepare the polyanionic GOx@DNA composite. The above materials were then mixed together and adhered together through sol-gel technology. Thus, the Fe3O4@PDDA/GOx@DNA composite absorbent was prepared. Its performance was tested by disperse solid phase extraction and gas chromatography/mass spectrometric (GC/MS) for removing six kinds of indicative polybrominated diphenyl ethers (BDEs) in water samples. The removal percentages of several real samples for six kinds of BDEs (BDE17, BDE28, BDE 71, BDE 47, BDE 66, BDE 100) at the ng/mL order of magnitude were in the range of 88.2%–99.1%. The removal percentage still reached 80.0% when the adsorbent was reused at least 20 times. The results suggested that the magnetic absorbent can obviously remove trace levels of BDEs from large volumes of aqueous solutions in environmental pollution cleanup with high removal efficiency.
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Affiliation(s)
- Ning Gan
- The State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211, Zhejiang, China.
| | - Jiabing Zhang
- The State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211, Zhejiang, China.
| | - Shaichai Lin
- The State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211, Zhejiang, China.
| | - Nengbing Long
- The State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211, Zhejiang, China.
| | - Tianhua Li
- The State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211, Zhejiang, China.
| | - Yuting Cao
- The State Key Laboratory Base of Novel Functional Materials and Preparation Science, Faculty of Material Science and Chemical Engineering of Ningbo University, Ningbo 315211, Zhejiang, China.
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Li L, Chang W, Wang Y, Ji H, Chen C, Ma W, Zhao J. Rapid, Photocatalytic, and Deep Debromination of Polybrominated Diphenyl Ethers on Pd-TiO2: Intermediates and Pathways. Chemistry 2014; 20:11163-70. [DOI: 10.1002/chem.201402477] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Indexed: 11/08/2022]
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Kim EJ, Kim JH, Kim JH, Bokare V, Chang YS. Predicting reductive debromination of polybrominated diphenyl ethers by nanoscale zerovalent iron and its implications for environmental risk assessment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2014; 470-471:1553-1557. [PMID: 23928371 DOI: 10.1016/j.scitotenv.2013.07.038] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/12/2013] [Accepted: 07/12/2013] [Indexed: 06/02/2023]
Abstract
The reductive debromination of polybrominated diphenyl ethers (PBDEs) by nanoscale zerovalent iron (nZVI) has proven to be a successful remediation approach. This study simulates the congener profiles and overall ecotoxicological impact of PBDE debromination by nZVI. The relationship between the calculated redox potential values and PBDE debromination rates was sufficiently strong to generate a satisfactory predictive capacity, which was further used to develop a quantitative structure-activity relationship (QSAR) model for the determination of the PBDE debromination patterns and dominant pathways. The predicted results of deca-BDE debromination showed that it would completely disappear within 30 days, but its lower brominated products, particularly tri- to penta-homologues, could exist in the environment even after 5 years. Formation and accumulation of more toxic, low brominated congeners through deca-BDE debromination suggest that deca-BDE may pose prolonged environmental risks. Changes in the toxic equivalent (TEQ) values during deca-BDE debromination parallel the occurrence and transformation of specific low brominated congeners with dioxin-like potency.
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Affiliation(s)
- Eun-Ju Kim
- School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea
| | - Jae-Hwan Kim
- School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea
| | - Ji-Hun Kim
- School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea
| | - Varima Bokare
- School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea
| | - Yoon-Seok Chang
- School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784, Republic of Korea.
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Electron-induced reductive debromination of 2,3,4-tribromodiphenyl ether: a computational study. J Mol Model 2013; 19:3333-8. [DOI: 10.1007/s00894-013-1868-y] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Accepted: 04/23/2013] [Indexed: 10/26/2022]
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Luo J, Hu J, Zhuang Y, Wei X, Huang X. Theoretical study on the radical anions and reductive dechlorination of selected polychlorinated dibenzo-p-dioxins. CHEMOSPHERE 2013; 91:765-770. [PMID: 23499218 DOI: 10.1016/j.chemosphere.2013.02.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Revised: 02/01/2013] [Accepted: 02/09/2013] [Indexed: 06/01/2023]
Abstract
For the effective use of remediation technologies for PCDDs contamination, it is essential to study the reactivity and dechlorination pathways of these compounds. In this study, density functional theory (DFT) calculations (B3LYP/6-31+G(d), B3LYP/6-311+G(d,p)) were performed to investigate the neutrals and different anionic states of selected PCDD congeners. The calculated adiabatic electron affinities and frontier orbital energies of the PCDD congeners (in gas-phase and in solution) are significantly correlated with the reported dechlorination rate constants, showing that this kind of reductive cleavage reaction is kinetically controlled by the electron transfer step. The predicted major dechlorination pathways of 1,2,3,4-TeCDD and its daughter products based on the energies of the anionic states were found to be satisfactorily consistent with the reported experimental results. Simulation of the 1,2,3,4-TeCDD dechlorination process showed that not only the dechlorination regioselectivity but also the reactivity of the PCDDs played an important role in the distribution of dechlorinated products. An exponential correlation was found between the sum of the concentration of the PCDD congeners and the reaction time in the simulation, indicating that the time required for the conversion of the PCDD congeners to the fully dechlorinated product (dibenzo-p-dioxin) might not be significantly dependent on the initial concentration of 1,2,3,4-TeCDD.
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Affiliation(s)
- Jin Luo
- Guizhou Provincial Key Laboratory for Information System of Mountainous Areas and Protection of Ecological Environment, Guizhou Normal University, Guiyang, PR China
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