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Huang C, Zeng Y, Luo X, Ren Z, Tian Y, Mai B. Comprehensive exploration of the ultraviolet degradation of polychlorinated biphenyls in different media. THE SCIENCE OF THE TOTAL ENVIRONMENT 2021; 755:142590. [PMID: 33059143 DOI: 10.1016/j.scitotenv.2020.142590] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 09/21/2020] [Accepted: 09/22/2020] [Indexed: 06/11/2023]
Abstract
As one of the most important natural transformation processes, photodegradation deserves more attention and research. In the current work, we comprehensively explored the photochemical behaviors of polychlorinated biphenyls (PCBs) in n-hexane (Hex), methanol/water, and silica gel under UV-irradiation. Photodegradation rates were found to be faster in methanol/water than in Hex. All of the three photochemical systems generated sigmatropic rearrangement products. The dominant photodegradation pathways were dechlorination, dechlorination/methoxylation/hydroxylation, and hydroxylation in Hex, methanol/water, and silica gel systems, respectively. Furthermore, some new photodegradation products, such as polychlorinated biphenyl ethers, polychlorinated dibenzofurans, polychlorinated biphenylenes, and methylated polychlorinated biphenyls, are reported for the first time. These findings would provide deeper insight into the phototransformation behaviors of PCBs.
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Affiliation(s)
- Chenchen Huang
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yanhong Zeng
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
| | - Xiaojun Luo
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Zihe Ren
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Yankuan Tian
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
| | - Bixian Mai
- State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China
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2
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Chen J, Wu N, Qu R, Xu X, Shad A, Pan X, Yao J, Bin-Jumah M, Allam AA, Wang Z, Zhu F. Photodegradation of polychlorinated diphenyl sulfides (PCDPSs) under simulated solar light irradiation: Kinetics, mechanism, and density functional theory calculations. JOURNAL OF HAZARDOUS MATERIALS 2020; 398:122876. [PMID: 32768816 DOI: 10.1016/j.jhazmat.2020.122876] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2019] [Revised: 04/27/2020] [Accepted: 04/27/2020] [Indexed: 06/11/2023]
Abstract
The direct photolysis of 25 individual polychlorinated diphenyl sulfides (PCDPSs) substituted with 1-7 chlorine atoms was investigated using a 500-W Xe lamp. Photolysis of PCDPSs followed pseudo-first-order kinetics, with the higher chlorinated diphenyl sulfides generally degrading faster than the lower chlorinated congeners. A quantitative structure-activity relationship model to predict the photolysis rates of PCDPSs was developed using 16 fundamental quantum chemical descriptors. We found that the substitution pattern for chlorine atoms, the dipole moment, and ELUMO - EHOMO were major factors in the photolysis of PCPDSs. The reaction kinetics, products, and photodegradation pathways of 2,2',3',4,5-pentachlorodiphenyl sulfide (PeCDPS) suggest hydroxylation, direct photooxidation, the C-S bond cleavage reaction, and hydroxyl substitution were mainly involved in the photodegradation process, leading to the formation of 13 intermediates, detected by an electrospray time-of-flight mass spectrometer. The initial reaction sites of PCDPSs under photolysis were rationalized by density functional theory calculations. Anions (Cl-, SO42-, NO3-, and HCO3-) and Co2+ had no influence on the removal of PeCDPS, while Fe3+, Cu2+, and HA decreased the photolysis efficiency of PeCDPS. This report is the first to develop a logk quantitative structure-property relationships (QSPR) model of 25 PCDPSs and to describe mechanistic pathways for the photolysis of PeCDPS.
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Affiliation(s)
- Jing Chen
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Jiangsu Nanjing 210023, PR China
| | - Nannan Wu
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Jiangsu Nanjing 210023, PR China
| | - Ruijuan Qu
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Jiangsu Nanjing 210023, PR China
| | - Xinxin Xu
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Jiangsu Nanjing 210023, PR China
| | - Asam Shad
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Jiangsu Nanjing 210023, PR China
| | - Xiaoxue Pan
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Jiangsu Nanjing 210023, PR China
| | - Jiayi Yao
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Jiangsu Nanjing 210023, PR China
| | - May Bin-Jumah
- Biology Department, Faculty of Science, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia
| | - Ahmed A Allam
- Department of Zoology, Faculty of Science, Beni-suef University, Beni-suef 65211, Egypt
| | - Zunyao Wang
- State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Jiangsu Nanjing 210023, PR China.
| | - Feng Zhu
- Jiangsu Provincial Center for Disease Control and Prevention, NO.172 Jiangsu Road, Jiangsu Nanjing 210023, PR China.
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3
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Jiang H, Dang C, Liu W, Wang T. Radical attack and mineralization mechanisms on electrochemical oxidation of p-substituted phenols at boron-doped diamond anodes. CHEMOSPHERE 2020; 248:126033. [PMID: 32004882 DOI: 10.1016/j.chemosphere.2020.126033] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/20/2019] [Revised: 01/24/2020] [Accepted: 01/24/2020] [Indexed: 06/10/2023]
Abstract
Degradation of phenols with different substituent groups (including -OCH3, -CHO, -NHCOCH3, -NO2, and -Cl) at boron-doped diamond (BDD) anodes has been studied previously based on the removal efficiency and •OH detection. Innovatively, formations of CO2 gas and various inorganic ions were examined to probe the mineralization process combined with quantitative structure-activity relationship (QSAR) analysis. As results, all phenols were efficiently degraded within 8 h with high COD removal efficiency. Three primary intermediates (hydroquinone, 1,4-benzoquinone and catechol) were identified during electrochemical oxidation and degradation pathway was proposed. More importantly, CO2 transformation efficiency ranked as: no N or Cl contained phenols (p-CHO, p-OCH3 and Ph) > N-contained phenols (p-NHCOCH3 and p-NO2) > Cl-contained phenols (p-Cl and o,p-Cl). Carbon mass balance study suggested formation of inorganic carbon (H2CO3, CO32- and HCO3-) and CO2 after organic carbon elimination. Inorganic nitrogen species (NH4+, NO3- and NO2-) and chlorine species (Cl-, ClO3- and ClO4-) were also formed after N- and Cl-contained phenols mineralization, while no volatile nitrogen species were detected. The phenols with electron-withdrawing substituents were easier to be oxidized than those with electron-donating substituents. QSAR analysis indicated that the reaction rate constant (k1) for phenols degradation was highly related to Hammett constant (∑σo,m,p) and energy gap (ELUMO - EHOMO) of the compound (R2 = 0.908), which were key parameters on evaluating the effect of structural moieties on electronic character and the chemical stability upon radical attack for a specific compound. This study presents clear evidence on mineralization mechanisms of phenols degradation at BDD anodes.
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Affiliation(s)
- Huan Jiang
- College of Environmental Sciences and Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, 100871, China
| | - Chenyuan Dang
- College of Environmental Sciences and Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, 100871, China
| | - Wen Liu
- College of Environmental Sciences and Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, 100871, China; The Beijing Innovation Center for Engineering Science and Advanced Technology (BIC-ESAT), Peking University, Beijing, 100871, China; Beijing Engineering Research Center for Advanced Wastewater Treatment, Department of Environmental Engineering, Peking University, Beijing, 100871, China
| | - Ting Wang
- College of Environmental Sciences and Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing, 100871, China; Beijing Engineering Research Center for Advanced Wastewater Treatment, Department of Environmental Engineering, Peking University, Beijing, 100871, China.
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4
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Jiang Y, Zhu X, Xing X. Electrochemical Oxidation of Phenolic Compounds at Boron-Doped Diamond Anodes: Structure–Reactivity Relationships. J Phys Chem A 2017; 121:4326-4333. [DOI: 10.1021/acs.jpca.7b02630] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yi Jiang
- Department
of Energy, Environmental and Chemical Engineering, Washington University in St. Louis, St. Louis, Missouri 63130, United States
- Department
of Environmental Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, China
| | - Xiuping Zhu
- Department
of Civil and Environmental Engineering, Louisiana State University, Baton
Rouge, Louisiana 70803, United States
- Department
of Environmental Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, China
| | - Xuan Xing
- College
of Life and Environmental Sciences, Minzu University of China, Beijing 100081, China
- Department
of Environmental Engineering, Peking University, The Key Laboratory of Water and Sediment Sciences, Ministry of Education, Beijing 100871, China
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5
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Sun Y, Zhang Q, Wang W. Products, mechanism, and kinetics of OH radical-initiated oxidation degradation of 2,4,4′-trichlorobiphenyl in the atmosphere. RSC Adv 2016. [DOI: 10.1039/c6ra07878h] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
To better understand the behavior, fate and oxidation products of polychlorinated biphenyls (PCBs) in the atmosphere, probing the atmospheric oxidation mechanism and kinetic properties of PCBs is of crucial importance.
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Affiliation(s)
- Yanhui Sun
- Environment Research Institute
- Shandong University
- Jinan 250100
- P. R. China
- College of Environment and Safety Engineering
| | - Qingzhu Zhang
- Environment Research Institute
- Shandong University
- Jinan 250100
- P. R. China
| | - Wenxing Wang
- Environment Research Institute
- Shandong University
- Jinan 250100
- P. R. China
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6
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Gupta S, Basant N, Rai P, Singh KP. Modeling the binding affinity of structurally diverse industrial chemicals to carbon using the artificial intelligence approaches. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2015; 22:17810-17827. [PMID: 26160122 DOI: 10.1007/s11356-015-4965-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Accepted: 06/25/2015] [Indexed: 06/04/2023]
Abstract
Binding affinity of chemical to carbon is an important characteristic as it finds vast industrial applications. Experimental determination of the adsorption capacity of diverse chemicals onto carbon is both time and resource intensive, and development of computational approaches has widely been advocated. In this study, artificial intelligence (AI)-based ten different qualitative and quantitative structure-property relationship (QSPR) models (MLPN, RBFN, PNN/GRNN, CCN, SVM, GEP, GMDH, SDT, DTF, DTB) were established for the prediction of the adsorption capacity of structurally diverse chemicals to activated carbon following the OECD guidelines. Structural diversity of the chemicals and nonlinear dependence in the data were evaluated using the Tanimoto similarity index and Brock-Dechert-Scheinkman statistics. The generalization and prediction abilities of the constructed models were established through rigorous internal and external validation procedures performed employing a wide series of statistical checks. In complete dataset, the qualitative models rendered classification accuracies between 97.04 and 99.93%, while the quantitative models yielded correlation (R(2)) values of 0.877-0.977 between the measured and the predicted endpoint values. The quantitative prediction accuracies for the higher molecular weight (MW) compounds (class 4) were relatively better than those for the low MW compounds. Both in the qualitative and quantitative models, the Polarizability was the most influential descriptor. Structural alerts responsible for the extreme adsorption behavior of the compounds were identified. Higher number of carbon and presence of higher halogens in a molecule rendered higher binding affinity. Proposed QSPR models performed well and outperformed the previous reports. A relatively better performance of the ensemble learning models (DTF, DTB) may be attributed to the strengths of the bagging and boosting algorithms which enhance the predictive accuracies. The proposed AI models can be useful tools in screening the chemicals for their binding affinities toward carbon for their safe management.
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Affiliation(s)
- Shikha Gupta
- Environmental Chemistry Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow, 226 001, India
| | - Nikita Basant
- KanbanSystems Pvt. Ltd., Laxmi Nagar, Delhi, 110092, India
| | - Premanjali Rai
- Environmental Chemistry Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow, 226 001, India
| | - Kunwar P Singh
- Environmental Chemistry Division, CSIR-Indian Institute of Toxicology Research, Post Box 80, Mahatma Gandhi Marg, Lucknow, 226 001, India.
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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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8
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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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Wang S, Hao C, Gao Z, Chen J, Qiu J. Theoretical investigation on photodechlorination mechanism of polychlorinated biphenyls. CHEMOSPHERE 2014; 95:200-205. [PMID: 24055025 DOI: 10.1016/j.chemosphere.2013.08.066] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2013] [Revised: 08/07/2013] [Accepted: 08/16/2013] [Indexed: 06/02/2023]
Abstract
Photodechlorination is a key process affecting the fate and effect of polychlorinated biphenyls (PCBs) in the environment. However, there are still numerous gaps in our knowledge, which become apparent in photodechlorination mechanism of PCBs. We investigated the conformations of 35 PCB congeners in the ground state and the first triplet excited state (T1), and predicted the photodechlorination pathway of the PCBs by calculating bond dissociation energies of the C-Cl bonds and activation energies of the C-Cl bond dissociation in the excited T1 state. Results show that the torsional degree of the two benzene rings of the PCBs depends on the number of ortho chlorines because of steric effect in the ground state. The two benzene rings of the PCBs with low photoreactivity tend to be coplanar and their torsional degree becomes lower in the excited T1 state compared with those in the ground state. The serious deformation and non-coplane of the benzene rings of some PCBs (e.g. PCB138) in the excited T1 state reduces the conjugation between the two benzene rings, implying that these PCBs have high photoreactivity. The dissociation of the C-Cl bond is the rate-determining step in the photodechlorination reactions of PCBs when the hydrogen donor is methanol. The main photodechlorination pathways predicted in this study are in good agreement with previous experimental results. Our results have provided new insights into mechanism of PCBs photodechlorination, which could be useful in the future in utilizing quantum chemistry calculation in investigating the environmental behavior and fate of organic pollutants.
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Affiliation(s)
- Se Wang
- State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024, China
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10
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Yue C, Li LY. Filling the gap: estimating physicochemical properties of the full array of polybrominated diphenyl ethers (PBDEs). ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2013; 180:312-323. [PMID: 23796874 DOI: 10.1016/j.envpol.2013.05.029] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2013] [Revised: 05/18/2013] [Accepted: 05/20/2013] [Indexed: 06/02/2023]
Abstract
Physicochemical properties of PBDE congeners are important for modeling their transport, but data are often missing. The quantitative structure-property relationship (QSPR) approach is utilized to fill this gap. Individual research groups often report piecemeal properties through experimental measurements or estimation techniques, but these data seldom satisfy fundamental thermodynamic relationships because of errors. The data then lack internal consistency and cannot be used directly in environmental modeling. This paper critically reviews published experimental data to select the best QSPR models, which are then extended to all 209 PBDE congeners. Properties include aqueous solubility, vapor pressure, Henry's law constant, octanol-water partition coefficient and octanol-air partition coefficient. Their values are next adjusted to satisfy fundamental thermodynamic equations. The resulting values then take advantage of all measurements and provide quick references for modeling and PBDE-contaminated site assessment and remediation. PCBs are also compared with respect to their properties and estimation methods.
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Affiliation(s)
- Chaoyang Yue
- Department of Civil Engineering, University of British Columbia, 6250 Applied Science Lane, Vancouver, BC, Canada, V6T 1Z4
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11
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He Z, Sun J, Wei J, Wang Q, Huang C, Chen J, Song S. Effect of silver or copper middle layer on the performance of palladium modified nickel foam electrodes in the 2-chlorobiphenyl dechlorination. JOURNAL OF HAZARDOUS MATERIALS 2013; 250-251:181-189. [PMID: 23454456 DOI: 10.1016/j.jhazmat.2013.02.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Revised: 01/08/2013] [Accepted: 02/01/2013] [Indexed: 06/01/2023]
Abstract
To enhance the activity of chemi-deposited palladium/nickel foam (Pd/Ni) electrodes used for an electrochemical dechlorination process, silver or copper was deposited electrochemically onto the nickel foam substrate (to give Ag/Ni or Cu/Ni) before the chemical deposition of palladium. The physicochemical properties of the resulting materials (Pd/Ni, Pd/Ag/Ni and Pd/Cu/Ni) were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and their electrochemical catalytic activities were evaluated by monitoring the electrochemical dechlorination of 2-chlorobiphenyl (2-CB) in strongly alkaline methanol/water solution. The results show that the Pd/Ag/Ni and Pd/Cu/Ni electrodes had consistently higher electrocatalytic activities and current efficiencies (CEs) compared with the untreated Pd/Ni electrode. The Pd/Ag/Ni electrode exhibited the highest activity. The dechlorination was also studied as a function of Pd loading, the Ag or Cu interlayer loadings, and the current density. The Pd loading and the interlayer loadings both had positive effects on the dechlorination reaction. Increasing the current density increased the reaction rate but reduced the CE. The improvement of the electrocatalytic activities of the Pd/Ni electrode by applying the interlayer of Ag or Cu resulted from the enlargement of the effective surface area of the electrode and the adjustment of the metal-H bond energy to the appropriate value, as well as the effective adsorption of 2-CB on Ag. Moreover, the high catalytic activity of the Pd/Ag/Ni electrode was maintained after six successive cyclic experiments, whereas Pd/Cu/Ni electrodes deactivate severely under the same conditions.
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Affiliation(s)
- Zhiqiao He
- College of Biological and Environmental Engineering, Zhejiang University of Technology, Hangzhou 310032, People's Republic of China
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12
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Chen L, Shen C, Zhou M, Tang X, Chen Y. Accelerated photo-transformation of 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) in water by dissolved organic matter. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2013; 20:1842-1848. [PMID: 22948567 DOI: 10.1007/s11356-012-1112-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2012] [Accepted: 07/24/2012] [Indexed: 06/01/2023]
Abstract
The ubiquitous dissolved organic matter (DOM) has an important influence on transformation of organic contaminants through the production of reactive substances, such as (•)OH, (1)O(2), and (3)DOM*. The photolysis of a higher chlorinated polychlorinated biphenyl (PCB) congener (2,2',4,4',5,5'-hexachlorobiphenyl, PCB 153) under simulated sunlight in presence of humic acid (HA) was investigated. Degradation of PCB 153 was accelerated significantly by the addition of HA, with a rate constant of 0.0214, 0.0413, and 0.0358 h(-1) in the initial 18 h of irradiation in presence of 1, 5, and 20 mg/L HA, respectively. The main photodegradation products analyzed by gas chromatography mass spectrometry were 4-hydroxy-2,2',4',5,5'-pentaCB and 2,4,5-trichlorobenzoic acid. Main reactive species involved were determined by the electron spin-resonance spectroscopy, including (1)O(2) and (•)OH. Special scavengers were added to elucidate the photolysis mechanisms. By using the specific scavengers, it turned out that (•)OH accounted for 29.3 % of the degradation, and the intra-DOM reactive species ((1)O(2), (•)OH, and (3)DOM*) accounted for 59.6 % of the degradation. Photo-transformation sensitized by DOM, which involves both aqueous and intra-DOM reactions of PCBs with reactive species, may be one of the most important mechanisms for natural attenuation of PCBs.
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Affiliation(s)
- Lei Chen
- College of Environmental and Resource Sciences, Zhejiang University, 388 Yuhangtang Road, Hangzhou, 310058, People's Republic of China
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13
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Chen L, Tang X, Shen C, Chen C, Chen Y. Photosensitized degradation of 2,4',5-trichlorobiphenyl (PCB 31) by dissolved organic matter. JOURNAL OF HAZARDOUS MATERIALS 2012; 201-202:1-6. [PMID: 22169245 DOI: 10.1016/j.jhazmat.2011.10.061] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 10/25/2011] [Accepted: 10/25/2011] [Indexed: 05/31/2023]
Abstract
The presence of dissolved organic matter (DOM) in aquatic system has an important influence on the phototransformation of organic contaminants through the production of reactive substances, such as hydroxyl radicals (OH), singlet oxygen ((1)O(2)), and DOM triplet states ((3)DOM) under solar irradiation. Addition of 5mg/L of Humic acid sodium (HA), Suwannee River NOM (SRNOM) and Nordic Reservoir NOM (NRNOM) all accelerated the photodegradation of 2,4',5-trichlorobiphenyl (PCB 31) significantly, with a pseudo-first-order rate constant of 0.0933, 0.0651 and 0.0486 in the initial 12h, respectively. HA and SRNOM, the allochthonous DOM, showed higher reactivity in the photolysis of PCB 31. The maximum photodegradation rate was observed in 5mg/L of DOM solution. The roles of the reactive substances were studied by the inhibitory experiments, which suggested that OH and intra-DOM (1)O(2) were more important for the photolysis of PCB 31 than other reactive substances, accounting for 35.1% and 47.1% of the degradation, respectively. The main degradation products of PCB 31 detected by GC-MS were 4-chlorobenzoic acid, 2,5-dichlorobenzoic acid, hydroxy-2,5-dichlorobenzoic acid, 4-hydroxy-2',5'-dichlorobiphenyls and hydroxy-trichlorobiphenyls. The degradation pathways were accordingly proposed. Photosensitized degradation by DOM, especially the intra-DOM reactions, may be a very important mechanism for the transformation of PCBs and other hydrophobic organic contaminants in the environment.
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Affiliation(s)
- Lei Chen
- College of Environmental & Resource Sciences of Zhejiang University, Hangzhou 310029, People's Republic of China
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14
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Fatemi MH, Chahi ZG. QSPR-based estimation of the half-lives for polychlorinated biphenyl congeners. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2012; 23:155-168. [PMID: 22224473 DOI: 10.1080/1062936x.2011.645876] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
In this study, the depuration half-lives of 62 polychlorinated biphenyl (PCB) congeners in juvenile rainbow trout (Oncorhynchus mykiss) were estimated from their structural features based on QSPR methodology. A genetic algorithm (GA) was applied as a variable subset selection strategy and QSPR models established upon multiple linear regression (MLR), multilayer perceptron neural network (MLP NN) and support vector regression (SVR) procedures. Robustness and predictive stability of the constructed models were evaluated through internal and external validation methods. The high numerical values of [Formula: see text] and [Formula: see text], and low RMSE in the case of the MLP NN model, confirm the supremacy of this model as well as nonlinear dependency of molecular structural features to the PCB congeners half-lives. In the best developed QSPR model the following four descriptors are used; lopping centric index (Lop), mean topological charge index of order 1 (JGI1), Geary autocorrelation lag-8/weighted by atomic Sanderson electronegativities (GATS8e) and highest eigenvalue of Burden matrix/weighted by atomic masses (BEHm3). Analysis of the descriptors involved in these models revealed that 2D molecular structural features, compactness and electronegativities are the main factors contributing to the half-lives of PCBs. The structural information presented in this work can be used for further evaluation of half-lives of PCBs and other similar structural compounds in the environment.
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Affiliation(s)
- M H Fatemi
- Chemometrics Laboratory, Faculty of Chemistry, University of Mazandaran, Babolsar, Iran.
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15
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Suh YW, Buettner GR, Venkataraman S, Treimer SE, Robertson LW, Ludewig G. UVA/B-induced formation of free radicals from decabromodiphenyl ether. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2009; 43:2581-2588. [PMID: 19452920 PMCID: PMC2685467 DOI: 10.1021/es8022978] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Polybrominated diphenyl ether (PBDE) flame retardants are ubiquitous in the environment and in humans. A deca-bromodiphenyl ether mixture (deca-BDE) is the dominating commercial PBDE product today. Deca-BDE is degraded by UV to PBDEs with fewer bromines. We hypothesized that photodegradation of deca-BDE results in the formation of free radicals. We employed electron paramagnetic resonance (EPR) with spin trap agents to examine the free radicals formed from UV irradiation of a deca-BDE mixture (DE-83R). The activating wavelength for deca-BDE photochemistry was in the UVA to UVB range. The yields of radicals from irradiated deca-BDE in tetrahydrofuran, dimethylformamide, and toluene were about 9-, 4-, and 7-fold higher, respectively, than from irradiated solvent alone. Radical formation increased with deca-BDE concentration and irradiation time. The quantum yield of radical formation of the deca-BDE mixture was higher than with an octa-BDE mixture (DE-79; approximately 2-fold), decabromobiphenyl (PBB 209; approximately 2-fold), decachlorobiphenyl (PCB 209; approximately 3-fold), and diphenyl ether (DE; approximately 6-fold), indicating the positive effects of bromine and an ether bond on radical formation. Analysis of hyperfine splittings of the spin adducts suggests that radical formation is initiated or significantly enhanced by debromination paired with hydrogen abstraction from the solvents. To our knowledge this is the first study that uses EPR to demonstrate the formation of free radicals during the photolytic degradation of PBDEs. Our findings strongly suggestthe potential of negative consequences due to radical formation during UV exposure of PBDEs in biological systems.
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Affiliation(s)
- Yang-won Suh
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA 52242, USA
| | - Garry R. Buettner
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA 52242, USA
- Free Radical and Radiation Biology Program, ESR Facility, The University of Iowa, Iowa City, IA 52242, USA
| | - Sujatha Venkataraman
- Free Radical and Radiation Biology Program, ESR Facility, The University of Iowa, Iowa City, IA 52242, USA
| | | | - Larry W. Robertson
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA 52242, USA
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA 52242, USA
| | - Gabriele Ludewig
- Department of Occupational and Environmental Health, The University of Iowa, Iowa City, IA 52242, USA
- Interdisciplinary Graduate Program in Human Toxicology, The University of Iowa, Iowa City, IA 52242, USA
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