1
|
Zhang C, Geng X, Zhu L, Xia D, Li X, Sun Y. Br-to-Cl Transformation Guided the Formation of Polyhalogenated Dibenzo- p-dioxins/Dibenzofurans. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2024. [PMID: 39096310 DOI: 10.1021/acs.est.4c06328] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/05/2024]
Abstract
Polyhalogenated dibenzo-p-dioxins/dibenzofurans (PXDD/Fs) are commonly released into the environment as byproducts of combustion processes, accompanied by flue gases. Chlorinated (Cl) and brominated (Br) precursors play crucial roles in forming PXDD/Fs. However, the specific contributions of Cl-precursors and Br-precursors to PXDD/Fs formation have not been fully elucidated. Herein, we demonstrate that the formation of Br-precursors can increase the fraction of polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) congeners substituted at specific positions, such as 1,2,3,4,6,7,8-HpCDD, OCDD, 2,3,4,7,8-PeCDF, and 2,3,4,6,7,8-HxCDF. This is attributed to the electrophilic chlorination reaction of the Br-precursors, which includes the Br-to-Cl transformation pathway, following the principle of regioselectivity. The observed formation of polybrominated/chlorinated dibenzo-p-dioxins/benzofurans (PBCDD/Fs) from 1,2-dibromobenzene (1,2-DiBBz) as a Br precursor provides direct evidence supporting the proposed Br-to-Cl transformation. Quantum chemical calculations are employed to discuss the principle of regioselectivity in the Br-to-Cl transformation, clarifying the priority of the position for electrophilic chlorination. Additionally, the concentration of PCDD/Fs formed from 1,2-DiBBz is 1.6 μg/kg, comparable to that of polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) (2.4 μg/kg), highlighting the potential of brominated organic pollutants as precursors for PCDD/Fs formation. This study provides three potential pathways for PCDD/Fs formation from Br-precursors, establishing a theoretical foundation for elucidating the formation mechanism of PXDD/Fs in the coexistence of Cl and Br.
Collapse
Affiliation(s)
- Congcong Zhang
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Xuan Geng
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Lingfeng Zhu
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Dan Xia
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Xiang Li
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Yifei Sun
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
- Research Center for Advanced Energy and Carbon Neutrality, Beihang University, Beijing 100191, PR China
- School of Environmental Science and Engineering, Hainan University, Haikou 570228, PR China
| |
Collapse
|
2
|
Wang X, Hadizadeh MH, Wang W, Hu Y, Zhou Y, Xu F, Sun Y, Wang W. DFT and AIMD insights into heterogeneous dissociation of 2-chlorothiophenol on CuO(111) surface: Impact of H 2O and OH. CHEMOSPHERE 2024; 359:142228. [PMID: 38705407 DOI: 10.1016/j.chemosphere.2024.142228] [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: 02/24/2024] [Revised: 04/29/2024] [Accepted: 05/01/2024] [Indexed: 05/07/2024]
Abstract
Copper oxides are vital catalysts in facilitating the formation of polychlorinated thianthrenes/dibenzothiophenes (PCTA/DTs) through heterogeneous reactions in high-temperature industrial processes. Chlorothiophenols (CTPs) are the most crucial precursors for PCTA/DT formation. The initial step in this process is the metal-catalyzed production of chlorothiophenoxy radicals (CTPRs) from CTPs via dissociation reactions. This work combines density functional theory (DFT) calculations with ab initio molecular dynamics (AIMD) simulations to explore the formation mechanism of the adsorbed 2-CTPR from 2-CTP, with the assistance of CuO(111). Our study demonstrates that flat adsorption configurations of 2-CTP on the CuO(111) surface are more stable than vertical configurations. The CuO(111) surface acts as a strong catalyst, facilitating the dissociation of 2-CTP into the adsorbed 2-CTPR. Surface oxygen vacancies enhance the adsorption of 2-CTP on the CuO(111) surface, while moderately suppressing the dissociation of 2-CTP. More importantly, water molecules and surface hydroxyl groups actively promote the dissociation of 2-CTP. Specifically, water directly participates in the reaction through "water bridge", enabling a barrier-free process. This research provides molecular-level insights into the heterogeneous generation of dioxins with the catalysis of metal oxides in fly ash from static and dynamic aspects, providing novel approaches for reducing dioxin emissions and establishing dioxin control strategies.
Collapse
Affiliation(s)
- Xiaotong Wang
- Environment Research Institute, Shandong University, Qingdao, 266237, China
| | - Mohammad Hassan Hadizadeh
- Environment Research Institute, Shandong University, Qingdao, 266237, China; International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at the Microscale, and Synergetic Innovation Center of Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, 230026, China
| | - Wei Wang
- Environment Research Institute, Shandong University, Qingdao, 266237, China
| | - Yongxia Hu
- Environment Research Institute, Shandong University, Qingdao, 266237, China
| | - Ying Zhou
- Environment Research Institute, Shandong University, Qingdao, 266237, China
| | - Fei Xu
- Environment Research Institute, Shandong University, Qingdao, 266237, China; Shenzhen Research Institute of Shandong University, Shenzhen, 518057, China.
| | - Yanhui Sun
- College of Environment and Safety Engineering, Qingdao University of Science & Technology, Qingdao, 266042, China
| | - Wenxing Wang
- Environment Research Institute, Shandong University, Qingdao, 266237, China
| |
Collapse
|
3
|
Zhang C, Bai Z, Liu X, Xia D, Li X, Long J, Sun Z, Li Y, Sun Y. Co-incineration of medical waste in municipal solid waste incineration increased emission of chlorine/brominated organic pollutants. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 937:173544. [PMID: 38802016 DOI: 10.1016/j.scitotenv.2024.173544] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/13/2024] [Revised: 05/23/2024] [Accepted: 05/24/2024] [Indexed: 05/29/2024]
Abstract
Co-incineration of medical waste (MW) in municipal solid waste incinerators (MSWIs) is a crucial disposal method for emergency disposal of MW and the management of MW in small and medium-sized towns. This study aims to analyze and compare the levels and distribution patterns of chlorine/brominated dioxins and their precursors in fly ash from MSWIs and medical waste incinerators (MWIs) while also focusing on identifying the new pollution concerns that may arise from the co-incineration of municipal solid waste (MSW) mixed with MW (MSW/MW). The concentration of chlorobenzene (CBzs), polychlorinated biphenyls (PCBs) and polychlorinated dibenzo-p-dioxins/dibenzofurans (PCDD/Fs) in fly ash from co-incineration of MSW/MW are 887.4, 134.4 and 27.6 μg/kg, respectively, which are 5.1, 2.0 and 2.9 times higher than that from MSWIs. The levels of polybrominated dibenzo-p-dioxins/dibenzofurans (PBDD/Fs) are about three orders of magnitude lower than that of PCDD/Fs. For the fly ash from MSWIs, the predominant PCDD/Fs congener is OCDD, which prefers synthesis and adsorption on fine-grained fly ash. For fly ash from MWIs, the major PCDD/Fs congeners are 1, 2, 3, 4, 6,7, 8-HpCDF, and OCDF, which prefer synthesis and adsorption on coarse-grained fly ash. Correlation analysis exhibited that both 1,2,3-TriCBz and 1,2,4-TriCBz in fly ash have a markedly linear correlation with PCDD/Fs and PCBs, but PBDD/Fs shows a poor negative correlation with PCDD/Fs.
Collapse
Affiliation(s)
- Congcong Zhang
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Ziang Bai
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Xingshuang Liu
- School of Environmental Science and Engineering, Hainan University, Haikou 570228, PR China
| | - Dan Xia
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Xiang Li
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China
| | - Jisheng Long
- Shanghai SUS Environment Co., LTD., Shanghai 201703, PR China
| | - Zhongtao Sun
- Shanghai SUS Environment Co., LTD., Shanghai 201703, PR China
| | - Yaojian Li
- Headquarters, China Tianying Inc., Jiangsu 226600, PR China
| | - Yifei Sun
- School of Energy and Power Engineering, Beihang University, Beijing 100191, PR China; School of Environmental Science and Engineering, Hainan University, Haikou 570228, PR China.
| |
Collapse
|
4
|
Wang X, Han Y, Hadizadeh MH, Wang W, Zhang Q, Hu Y, Xu F, Sun Y, Wang W. Periodic DFT calculations for the heterogeneous formation of 2-chlorothiophenoxy radical from 2-chlorothiophenol on Cu(111) surface in fly ash. ECOTOXICOLOGY AND ENVIRONMENTAL SAFETY 2024; 274:116186. [PMID: 38471341 DOI: 10.1016/j.ecoenv.2024.116186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 02/26/2024] [Accepted: 03/05/2024] [Indexed: 03/14/2024]
Abstract
Copper plays a crucial role in the heterogenous dissociation of chlorothiophenols (CTPs) to form chlorothiophenoxy radicals (CTPRs), which is the initial and critical step in the formation of polychlorinated thianthrenes/dibenzothiophenes (PCTA/DTs). Here, first-principles calculations were performed to investigate the activity of Cu(111) surface towards the formation of adsorbed 2-CTPR from 2-CTP. The interaction between 2-CTP and Cu(111) surface was explored to find stable adsorption configurations. Besides, the decomposition routes of 2-CTP on the Cu(111) surface were further explored. Moreover, the effects of water on the formation of absorbed 2-CTPR on the Cu(111) surface were examined. Our results demonstrate that the flat adsorption of 2-CTP on the surface with adsorption energy in the range of -33.21 kcal/mol to -28.37 kcal/mol is more stable than the vertical adsorption with adsorption energy ranging from -23.53 kcal/mol to -13.38 kcal/mol. The Cu(111) surface catalyzes the conversion of 2-CTP into the adsorbed 2-CTPR with a modest energy barrier of 9.46 kcal/mol. Furthermore, water molecules exhibit stronger catalytic activity in this process with a decreased energy barrier of 5.87 kcal/mol through "water bridge" and hydrogen bonding. Specifically, the water accepts the hydrogen atom from 2-CTP and donates another hydrogen to the surface via "water bridge". This research provides a molecular-level understanding of the heterogeneous formation of PCTA/DTs by fly ash, suggesting novel approaches for control strategy and legislation of dioxin analogues.
Collapse
Affiliation(s)
- Xiaotong Wang
- Environment Research Institute, Shandong University, Qingdao 266237, China
| | - Yanan Han
- Environment Research Institute, Shandong University, Qingdao 266237, China
| | | | - Wei Wang
- Environment Research Institute, Shandong University, Qingdao 266237, China
| | - Qi Zhang
- Environment Research Institute, Shandong University, Qingdao 266237, China
| | - Yongxia Hu
- Environment Research Institute, Shandong University, Qingdao 266237, China
| | - Fei Xu
- Environment Research Institute, Shandong University, Qingdao 266237, China; Shenzhen Research Institute of Shandong University, Shenzhen 518057, China.
| | - Yanhui Sun
- College of Environment and Safety Engineering, Qingdao University of Science & Technology, Qingdao 266042, China
| | - Wenxing Wang
- Environment Research Institute, Shandong University, Qingdao 266237, China
| |
Collapse
|
5
|
Wang M, Liu G, Yang L, Zheng M. Framework of the Integrated Approach to Formation Mechanisms of Typical Combustion Byproducts─Polyhalogenated Dibenzo- p-dioxins/Dibenzofurans (PXDD/Fs). ENVIRONMENTAL SCIENCE & TECHNOLOGY 2023; 57:2217-2234. [PMID: 36722466 DOI: 10.1021/acs.est.2c08064] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Understanding the mechanisms through which persistent organic pollutants (POPs) form during combustion processes is critical for controlling emissions of POPs, but the mechanisms through which most POPs form are poorly understood. Polyhalogenated dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) are typical toxic POPs, and the formation mechanisms of PXDD/Fs are better understood than the mechanisms through which other POPs form. In this study, a framework for identifying detailed PXDD/Fs formation mechanisms was developed and reviewed. The latest laboratory studies in which organic free radical intermediates of PXDD/Fs have been detected in situ and isotope labeling methods have been used to trace transformation pathways were reviewed. These studies provided direct evidence for PXDD/Fs formation pathways. Quantum chemical calculations were performed to determine the rationality of proposed PXDD/Fs formation pathways involving different elementary reactions. Many field studies have been performed, and the PXDD/Fs congener patterns found were compared with PXDD/Fs congener patterns obtained in laboratory simulation studies and theoretical studies to mutually verify the dominant PXDD/Fs formation mechanisms. The integrated method involving laboratory simulation studies, theoretical calculations, and field studies described and reviewed here can be used to clarify the mechanisms involved in PXDD/Fs formation. This review brings together information about PXDD/Fs formation mechanisms and provides a methodological framework for investigating PXDD/Fs and other POPs formation mechanisms during combustion processes, which will help in the development of strategies for controlling POPs emissions.
Collapse
Affiliation(s)
- Mingxuan Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, People's Republic of China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
| | - Guorui Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, People's Republic of China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- School of the Environment, Hangzhou Institute for Advanced Study, University of the Chinese Academy of Sciences, Hangzhou 310024, People's Republic of China
| | - Lili Yang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, People's Republic of China
| | - Minghui Zheng
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, People's Republic of China
- College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China
- School of the Environment, Hangzhou Institute for Advanced Study, University of the Chinese Academy of Sciences, Hangzhou 310024, People's Republic of China
| |
Collapse
|
6
|
Liu X, Liu G, Liu S, Qin L, Lin B, Wang M, Yang L, Zheng M. Free radical mechanism of toxic organic compound formations from o-chlorophenol. JOURNAL OF HAZARDOUS MATERIALS 2023; 443:130367. [PMID: 36444078 DOI: 10.1016/j.jhazmat.2022.130367] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 11/07/2022] [Accepted: 11/07/2022] [Indexed: 06/16/2023]
Abstract
Organic free radical intermediates are pivotal to our understanding of toxic chemicals formation from chlorophenols that widely exist in thermal processes. However, in most cases, multiple free radical intermediates exist and produce complex spectra that are hard to deconvolute. Identification of free radical intermediates is the current difficulty for detailed formation mechanisms of toxic products from chlorophenols. In this study, a universal bottom-up method was developed to identify the organic free radical intermediates. Candidate organic free radicals were firstly speculated according to the critical parameters obtained from experimental electron paramagnetic resonance (EPR) spectra and the calculated bond dissociation energies of precursors. Their theoretical spectra were then used retrospectively to justify the accordance with the experimental EPR spectra. Identification of the organic free radicals provides straightforward evidence for the formation pathways of pollutants from chlorophenol. Internal factors influencing formation of radical intermediates and the toxic products were also studied, including the ortho effect of the precursor, spin densities of the organic free radical intermediates, and steric hindrance effects of the molecular intermediates. In combination of the experimental results and theoretical calculations, detailed formation mechanisms of toxic pollutants intermediating by organic free radicals from thermal oxidation of chlorophenol were strongly evidenced.
Collapse
Affiliation(s)
- Xiaoyun Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guorui Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; School of the Environment, Hangzhou Institute for Advanced Study, University of the Chinese Academy of Sciences, Hangzhou 310024, China
| | - Shuting Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Linjun Qin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Bingcheng Lin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; School of the Environment, Hangzhou Institute for Advanced Study, University of the Chinese Academy of Sciences, Hangzhou 310024, China
| | - Mingxuan Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lili Yang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China.
| | - Minghui Zheng
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, P.O. Box 2871, Beijing 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049, China; School of the Environment, Hangzhou Institute for Advanced Study, University of the Chinese Academy of Sciences, Hangzhou 310024, China
| |
Collapse
|
7
|
Liu S, Liu G, Yang L, Liu X, Wang M, Qin L, Zheng M. Metal-Catalyzed Formation of Organic Pollutants Intermediated by Organic Free Radicals. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2022; 56:14550-14561. [PMID: 36168137 DOI: 10.1021/acs.est.2c05892] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Metal compounds play important roles in the formation of organic pollutants during thermal-related processes. However, the metal-catalyzed predominant organic pollutants have not previously been characterized nor have any detailed catalytic mechanisms been clarified. Here, we preciously distinguished the multiple organic free radical intermediates on metal catalyst surfaces during the organic pollutant formation through laboratory and theoretical studies. Differences between the organic free radical intermediate species, concentrations, and formation mechanisms under the catalysis of different metal compounds were investigated. The results were verified mutually with the differed characteristics of organic pollutant products. CuO predominantly catalyzed the formation of highly chlorinated phenoxy radical intermediates and dioxins. High proportions of semiquinone radicals and oxygen-containing derivatives were found on ZnO surfaces. Differently, methyl-substituted phenoxy radicals and long-chain products formed on Al2O3 surfaces. The results will be instructive for the target emission control of priority organic pollutants during thermal-related processes rich in different metal compounds.
Collapse
Affiliation(s)
- Shuting Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Guorui Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310000, China
| | - Lili Yang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Xiaoyun Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Mingxuan Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Linjun Qin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Minghui Zheng
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310000, China
| |
Collapse
|
8
|
Yin R, Chen J, Mi J, Liu H, Yan T, Shan L, Lang J, Li J. Breaking the Activity–Selectivity Trade-Off for Simultaneous Catalytic Elimination of Nitric Oxide and Chlorobenzene via FeVO 4–Fe 2O 3 Interfacial Charge Transfer. ACS Catal 2022. [DOI: 10.1021/acscatal.2c00161] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Affiliation(s)
- Rongqiang Yin
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Jianjun Chen
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Jinxing Mi
- State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Haiyan Liu
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Tao Yan
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Liang Shan
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Junyu Lang
- School of Physical Science and Technology, Shanghai Tech University, Shanghai 201210, China
| | - Junhua Li
- State Key Joint Laboratory of Environment Simulation and Pollution Control, School of Environment, Tsinghua University, Beijing 100084, China
| |
Collapse
|
9
|
Liu X, Yang L, Liu G, Zheng M. Formation of Environmentally Persistent Free Radicals during Thermochemical Processes and their Correlations with Unintentional Persistent Organic Pollutants. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2021; 55:6529-6541. [PMID: 33956443 DOI: 10.1021/acs.est.0c08762] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Attention is increasingly being paid to environmentally persistent free radicals (EPFRs), which are organic pollutants with the activities of free radicals and stabilities of organic pollutants. EPFRs readily form during thermal processes through the decomposition of organic precursors such as phenols, halogenated phenols, and quinone-type molecules, which are also important precursors of toxic unintentionally produced persistent organic pollutants (UPOPs). We have found that EPFRs are important intermediates for UPOP formation during thermal-related processes. However, interest in EPFRs is currently mostly focused on the toxicities and formation mechanisms of EPFRs themselves. Little information is available on the important roles EPFRs play in toxic UPOP formation during thermal processes. Here, we review the mechanisms involved in EPFR formation and transformation into UPOPs during thermal processes. The review is focused on typical EPFRs, including cyclopentadiene, phenoxy, and semiquinone radicals. The reaction temperature, metal species present, and oxygen concentration strongly affect EPFR and UPOP formation during thermal-related processes. Gaps in current knowledge and future directions for research into EPFR and UPOP formation, transformation, and control are presented. Understanding the relationships between EPFRs and UPOPs will allow synergistic control strategies to be developed for thermal-related industrial sources of EPFRs and UPOPs.
Collapse
Affiliation(s)
- Xiaoyun Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
| | - Lili Yang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, China
| | - Guorui Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310000, China
| | - Minghui Zheng
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Science, Chinese Academy of Sciences, Beijing 100085, China
- College of Resource and Environment, University of Chinese Academy of Sciences, Beijing 100049, China
- School of Environment, Hangzhou Institute for Advanced Study, UCAS, Hangzhou 310000, China
| |
Collapse
|
10
|
Unveiling the importance of reactant mass transfer in environmental catalysis: Taking catalytic chlorobenzene oxidation as an example. CHINESE CHEM LETT 2021. [DOI: 10.1016/j.cclet.2020.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
|
11
|
Li H, Liu W, Lu A, Li C, Die Q, Lei R, Wu X. PCDD/Fs emissions from secondary copper production synergistically controlled by fabric filters and desulfurization. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2021; 270:116065. [PMID: 33221088 DOI: 10.1016/j.envpol.2020.116065] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Revised: 11/08/2020] [Accepted: 11/09/2020] [Indexed: 06/11/2023]
Abstract
The effects of fabric filters and desulfurization systems during secondary copper smelting on polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) concentrations, emission coefficients, and profiles were studied in an oxygen-rich smelting furnace and an anode furnace. In the anode furnace, the toxic equivalent (TEQ) concentration ranges were 0.106-1.04 ng World Health Organization (WHO)-TEQ/m3 at the fabric filters inlet and 0.027-0.17 ng WHO-TEQ/m3 at the outlet. For the oxygen-rich smelting furnace, the TEQ concentration ranges were 1.21-1.93 and 0.010-0.019 ng WHO-TEQ/m3 at the desulfurization system inlet and outlet, respectively. The TEQs in the outlet stack gases of the desulfurization system from the anode furnace were 0.0041-0.016 ng WHO-TEQ/m3. It is likely that PCDD/Fs that were taken away from the stack gases were adsorbed by the fly ash and gypsum. Solid residues were the dominant release routes for PCDD/Fs. PCDD/Fs congener and homologue profiles of stack gases from different smelting stages were similar. The contributions of more chlorinated homologues from the anode furnace decreased observably after the stack gases passed through the fabric filters. However, the desulfurization process did not greatly change the PCDD/Fs homologue profiles. Overall, both the fabric filters and desulfurization systems showed excellent removal efficiencies for PCDD/Fs in the stack gases, which reduced the TEQ emissions to well below the 0.5 ng WHO-TEQ/m3 to achieve standard discharge.
Collapse
Affiliation(s)
- Haifeng Li
- Beijing Municipal Key Laboratory of Agriculture Environment Monitoring, Beijing Research Center for Agricultural Standards and Testing, Beijing, 100097, China; Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Wenbin Liu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; Hangzhou Institute for Advanced Study, UCAS, Hangzhou, 310024, China; University of Chinese Academy of Sciences, Beijing, 100049, China.
| | - Anxiang Lu
- Beijing Municipal Key Laboratory of Agriculture Environment Monitoring, Beijing Research Center for Agricultural Standards and Testing, Beijing, 100097, China
| | - Cheng Li
- Beijing Municipal Key Laboratory of Agriculture Environment Monitoring, Beijing Research Center for Agricultural Standards and Testing, Beijing, 100097, China
| | - Qingqi Die
- Beijing Municipal Key Laboratory of Agriculture Environment Monitoring, Beijing Research Center for Agricultural Standards and Testing, Beijing, 100097, China
| | - Rongrong Lei
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Xiaolin Wu
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China; University of Chinese Academy of Sciences, Beijing, 100049, China
| |
Collapse
|
12
|
Chen T, Sun C, Wang T, Lomnicki S, Zhan M, Li X, Lu S, Yan J. Formation of DF, PCDD/Fs and EPFRs from 1,2,3-trichlorobenzene over metal oxide/silica surface. WASTE MANAGEMENT (NEW YORK, N.Y.) 2020; 118:27-35. [PMID: 32882539 DOI: 10.1016/j.wasman.2020.08.024] [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: 09/09/2019] [Revised: 08/12/2020] [Accepted: 08/17/2020] [Indexed: 06/11/2023]
Abstract
The formation of dibenzofuran (DF), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and environmentally persistent free radicals (EPFRs) from 1,2,3-trichlorobenzene (1,2,3-TrCBz) over metal oxide / silica surface were investigated using a tubular furnace. PCDD/Fs increased exponentially from 250 to 550 °C over copper oxide / silica surface and PCDD/Fs had the maximum growth from 400 to 450 °C. The ratio of PCDD / PCDF was much less than 1, especially when the temperature raised from 450 to 550 °C. Pentachlorianated dibenzo-p-furan (PeCDF) dominated among the homologues, which contributed 45-61% to the total PCDD/Fs. Two peaks of the yield of DF occurred at 400 °C and 500 °C respectively. Furthermore, the oxygen contents have different effects for PCDD and PCDF formation, and low oxygen could promote PCDD production, especially for tetrachlorinated dibenzo-p-dioxin (TCDD). More PCDF were formed on the oxygen rich condition, indicating that the oxygen promoted the chlorination of DF. Iron oxides are better than copper oxides to catalyze the formation of PCDD/Fs from 1,2,3-TrCBzs at 350 °C, especially for PCDF. The major EPFRs on the catalysts were formed with g values in the range of 2.0040 to 2.0049, which were phenoxy radicals and semiquinone occurred with higher g value of 2.0075 when the temperature increased to 550 °C, and more EPFRs were produced with the temperature increasing. The addition of iron oxides reduced the spins concentrations of oxygen-centered radicals but increase the spins concentrations of signals with lower g values. The different possible formation pathways of PCDD and PCDF from 1,2,3-TrCBz over metal oxide surface were also proposed.
Collapse
Affiliation(s)
- Tong Chen
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China.
| | - Chen Sun
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
| | - Tianjiao Wang
- Everbright Envirotech (China) Ltd. Institute of Incineration Technology, Nanjing 211106, China
| | - Slawo Lomnicki
- Louisiana State University, Chemistry Department, 232 Choppin Hall, Baton Rouge, LA 70803, USA
| | - Mingxiu Zhan
- College of Metrology and Measurement Engineering, China Jiliang University, Hangzhou 310018, China.
| | - Xiaodong Li
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
| | - Shengyong Lu
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
| | - Jianhua Yan
- State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China
| |
Collapse
|
13
|
Tang J, Ma S, Liu R, Yue C, Li G, Yu Y, Yang Y, An T. The pollution profiles and human exposure risks of chlorinated and brominated PAHs in indoor dusts from e-waste dismantling workshops: Comparison of GC-MS, GC-MS/MS and GC × GC-MS/MS determination methods. JOURNAL OF HAZARDOUS MATERIALS 2020; 394:122573. [PMID: 32278123 DOI: 10.1016/j.jhazmat.2020.122573] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2020] [Revised: 03/05/2020] [Accepted: 03/19/2020] [Indexed: 06/11/2023]
Abstract
The toxicities of some chlorinated and brominated polycyclic aromatic hydrocarbons (X-PAHs) are higher than their corresponding parent PAHs. However, the identification and quantitation of X-PAHs in environment are still changeable and limitedly reported. To develop a robust method for routine analysis of X-PAHs in environmental samples, the determination of 34 X-PAHs was performed and compared using different instruments, including gas chromatography-mass spectrometry (GC-MS), gas chromatography-tandem mass spectrometry (GC-MS/MS) in both electron ionization (EI) and negative chemical ionization (NCI) modes, and comprehensive two-dimensional gas chromatograph-tandem mass spectrometer (GC × GC-MS/MS). GC-EI-MS/MS possessed the highest sensitivity with method detection limits of 2.00-40.0 and 2.00-20.0 pg/g dry weight (dw) for Cl-PAHs and Br-PAHs, respectively. This validated method was then applied to analyze X-PAHs in indoor dusts from a typical e-waste dismantling workshop, and the concentrations of Σ18Br-PAHs (8.80-399 ng/g dw) were higher than Σ16Cl-PAHs (7.91-137 ng/g dw). The toxicity equivalency quantities (TEQs) of Cl-PAHs at e-waste dismantling workshop and Br-PAHs at raw materials crushing workshop showed the highest values of 176 and 453 pg·TEQ/g, respectively. Cl-PAHs and Br-PAHs posed a potential health risk to workers through dust ingestion in workshops. Further attention should be payed to the formation mechanism of X-PAHs and the health risk.
Collapse
Affiliation(s)
- Jian Tang
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China
| | - Shengtao Ma
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China; Synergy Innovation Institute of GDUT, Shantou, 515100, China
| | - Ranran Liu
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China
| | - Congcong Yue
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China
| | - Guiying Li
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China; Synergy Innovation Institute of GDUT, Shantou, 515100, China
| | - Yingxin Yu
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China
| | - Yan Yang
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China; Synergy Innovation Institute of GDUT, Shantou, 515100, China
| | - Taicheng An
- Guangdong Key Laboratory of Environmental Catalysis and Health Risk Control, Guangzhou Key Laboratory of Environmental Catalysis and Pollution Control, School of Environmental Science and Engineering, Institute of Environmental Health and Pollution Control, Guangdong University of Technology, Guangzhou, 510006, China.
| |
Collapse
|
14
|
Chang J, Pan W, Liu X, Xue Q, Fu J, Zhang A. The formation of PBDFs from the ortho-disubstituted phenol precursors: A comprehensive theoretical study on the PBDD/Fs formation from 2,4,6-tribromophenol. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 713:136657. [PMID: 31958733 DOI: 10.1016/j.scitotenv.2020.136657] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 01/08/2020] [Accepted: 01/10/2020] [Indexed: 06/10/2023]
Abstract
Bromophenols are known as direct precursors of the notorious polybrominated dibenzo-p-dioxin/dibenzofurans (PBDD/Fs). There is a long-held viewpoint that only the more toxic dioxin-type products could be formed from the ortho-disubstituted phenols, totally contrary to the experimental observations that both PBDDs and PBDFs are generated. To tackle the issue, the gaseous formation mechanism of PBDD/Fs from 2,4,6-tribromophenol (TBP), a typical ortho-disubstituted phenol, was investigated in this study. Firstly, the reactions between TBP and the active H radical produce three key radical species including the bromophenoxyl radical, the substituted phenyl radical and phenoxyl diradical. The self- and cross-combinations of these radical species and TBP yield not only the dioxin-type products 1,3,6,8-TeBDD and 1,3,7,9-TeBDD, but also the brominated dibenzofurans 1,3,6,8-TeBDF and 2,4,6,8-TeBDF. Notably, the reactions involving the phenyl C sites in the substituted phenyl and phenoxyl diradicals are demonstrated to be both thermodynamically and kinetically more favorable than those involving the bromophenoxyl radical and the TBP molecule. Most importantly, the findings of the present work are of great importance as it provides feasible pathways to form less toxic dibenzofuran-type products from the ortho-disubstituted phenols. These results will improve the understanding of the PBDD/Fs formation mechanism from phenol precursors.
Collapse
Affiliation(s)
- Jiamin Chang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, PR China
| | - Wenxiao Pan
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China
| | - Xian Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, PR China
| | - Qiao Xue
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China
| | - Jianjie Fu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China
| | - Aiqian Zhang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, PR China; Institute of Environment and Health, Jianghan University, Wuhan 430056, PR China.
| |
Collapse
|
15
|
Pan B, Li H, Lang D, Xing B. Environmentally persistent free radicals: Occurrence, formation mechanisms and implications. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 248:320-331. [PMID: 30802746 DOI: 10.1016/j.envpol.2019.02.032] [Citation(s) in RCA: 92] [Impact Index Per Article: 18.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/08/2019] [Revised: 02/10/2019] [Accepted: 02/11/2019] [Indexed: 05/23/2023]
Abstract
Environmentally persistent free radicals (EPFRs) are defined as organic free radicals stabilized on or inside particles. They are persistent because of the protection by the particles and show significant toxicity to organisms. Increasing research interests have been attracted to study the potential environmental implications of EPFRs. Because of their different physical forms from conventional contaminants, it is not applicable to use the commonly used technique and strategy to predict and assess the behavior and risks of EPFRs. Current studies on EPFRs are scattered and not systematic enough to draw clear conclusions. Therefore, this review is organized to critically discuss the current research progress on EPFRs, highlighting their occurrence and transport, generation mechanisms, as well as their environmental implications (including both toxicity and reactivity). EPFR formation and stabilization as affected by the precursors and environmental factors are useful breakthrough to understand their formation mechanisms. To better understand the major differences between EPFRs and common contaminants, we identified the unique processes and/or mechanisms related to EPFRs. The knowledge gaps will be also addressed to highlight the future research while summarizing the research progress. Quantitative analysis of the interactions between organic contaminants and EPFRs will greatly improve the predictive accuracy of the multimedia environmental fate models. In addition, the health risks will be better evaluated when considering the toxicity contributed by EFPRs.
Collapse
Affiliation(s)
- Bo Pan
- Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, Yunnan, China; Yunnan Provincial Key Laboratory of Soil Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, Yunnan, China
| | - Hao Li
- Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, Yunnan, China; Yunnan Provincial Key Laboratory of Soil Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, Yunnan, China; Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA, 01003, United States
| | - Di Lang
- Faculty of Environmental Science & Engineering, Kunming University of Science & Technology, Kunming, 650500, Yunnan, China; Yunnan Provincial Key Laboratory of Soil Carbon Sequestration and Pollution Control in Soils, Kunming, 650500, Yunnan, China
| | - Baoshan Xing
- Stockbridge School of Agriculture, University of Massachusetts, Amherst, MA, 01003, United States.
| |
Collapse
|
16
|
Chen Q, Sun H, Mu Z, Wang Y, Li Y, Zhang L, Wang M, Zhang Z. Characteristics of environmentally persistent free radicals in PM 2.5: Concentrations, species and sources in Xi'an, Northwestern China. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2019; 247:18-26. [PMID: 30650344 DOI: 10.1016/j.envpol.2019.01.015] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 01/03/2019] [Accepted: 01/04/2019] [Indexed: 05/07/2023]
Abstract
Environmentally persistent free radicals (EPFRs) are a new class of environmental risk substances that can stably exist in atmospheric particles and pose a potential threat to human health. In this study, electron paramagnetic resonance (EPR) spectroscopy was used to study the concentration levels, species characteristics, and sources of EPFRs in PM2.5 in Xi'an in 2017. The results showed that the concentrations of EPFRs in PM2.5 in Xi'an in 2017 ranged from 9.8 × 1011 to 6.9 × 1014 spins/m3. The highest concentration of EPFRs occurred in winter when the average concentration was 2.1 × 1014 spins/m3. The lowest concentration of EPFRs occurred in autumn when the average concentration was 7.0 × 1013 spins/m3. According to the annual average atmospheric concentration of EPFRs, the amount of EPFRs inhaled by people in Xi'an is equivalent to approximately 5 cigarettes per person per day and approximately 23 cigarettes per person per day in winter when haze occurs. The results of the study on the EPFR characteristics show that the EPFRs in PM2.5 in Xi'an are mainly C-center organic radicals that are primarily non-decaying types, accounting for approximately 75% and 85% of total concentration of EPFRs in autumn and winter, respectively. Finally, a correlation analysis was used to explore the origins of EPFRs in PM2.5. Significant positive correlations were found between EPFRs and SO2, NO2 and the thermally derived OC3 and OC4 carbonaceous components. The results suggested that coal-fired and traffic may be important sources of EPFRs in PM2.5 in Xi'an. In addition, EPFRs are significantly positively correlated with O3 in summer, suggesting that some EPFRs may also originate from secondary processes. This study provides important basic data and evidence for further assessments of the potential health risks of EPFRs in PM2.5 and the development of effective air pollution control measures.
Collapse
Affiliation(s)
- Qingcai Chen
- School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China.
| | - Haoyao Sun
- School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China
| | - Zhen Mu
- School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China
| | - Yuqin Wang
- School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China
| | - Yanguang Li
- Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits, MLR, Xi'an, 710054, China; Xi'an Center of Geological Survey, China Geological Survey, Xi'an, 710054, China
| | - Lixin Zhang
- School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China
| | - Mamin Wang
- School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China
| | - Zimeng Zhang
- School of Environmental Science and Engineering, Shaanxi University of Science and Technology, Xi'an, 710021, China
| |
Collapse
|
17
|
Li H, Liu W, Tang C, Lei R, Zhu W. Emission profiles and formation pathways of 2,3,7,8-substituted and non-2,3,7,8-substituted polychlorinated dibenzo-p-dioxins and dibenzofurans in secondary copper smelters. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 649:473-481. [PMID: 30176459 DOI: 10.1016/j.scitotenv.2018.08.279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2018] [Revised: 08/15/2018] [Accepted: 08/21/2018] [Indexed: 06/08/2023]
Abstract
Secondary copper smelting production is one of the largest polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) emission sources in the world. However, the formations and emissions of non-2,3,7,8-PCDD/Fs have rarely been studied. Toxicology and metabolism studies have proved that non-2,3,7,8-PCDD/Fs may also be toxic to mammals. To better explore the pathways and mechanisms involved in transformation among non-2,3,7,8-PCDD/F and 2,3,7,8-PCDD/F congeners, their full picture was investigated in stack gas and fly ash samples collected in typical secondary copper smelting plants. The concentration ranges for 2,3,7,8-PCDD/Fs and non-2,3,7,8-PCDD/Fs in the stack gas samples were 0.09-5.24 ng/Nm3 and 0.11-7.47 ng/Nm3, respectively. The corresponding concentration ranges in the fly ash samples were 20-2712 ng/g and 2.7-818 ng/g. PCDD/F emissions were mainly from the oxidation stage, and these emissions contributed to 42.6-44.8% of the total emissions from the secondary copper smelting processes. Lower chlorinated PCDD/Fs partitioned more into the stack gas, whereas higher chlorinated PCDD/Fs were more likely to concentrate in the fly ash. Non-2,3,7,8-PCDD/Fs were more likely than 2,3,7,8-PCDD/Fs to associate with the gas phase. Chlorination transformation may occur among PCDD congeners, including 2,3,7,8-PCDD and non-2,3,7,8-PCDD congeners.
Collapse
Affiliation(s)
- Haifeng Li
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No.18, Shuangqing Road, Beijing 100085, China; University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049, China
| | - Wenbin Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No.18, Shuangqing Road, Beijing 100085, China; University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049, China.
| | - Chen Tang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No.18, Shuangqing Road, Beijing 100085, China
| | - Rongrong Lei
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No.18, Shuangqing Road, Beijing 100085, China; University of Chinese Academy of Sciences, No.19A, Yuquan Road, Beijing 100049, China
| | - Wen Zhu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, No.18, Shuangqing Road, Beijing 100085, China
| |
Collapse
|
18
|
Potter PM, Guan X, Lomnicki SM. Synergy of iron and copper oxides in the catalytic formation of PCDD/Fs from 2-monochlorophenol. CHEMOSPHERE 2018; 203:96-103. [PMID: 29614415 PMCID: PMC5911412 DOI: 10.1016/j.chemosphere.2018.03.118] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Revised: 03/12/2018] [Accepted: 03/17/2018] [Indexed: 05/30/2023]
Abstract
Transition metal oxides present in waste incineration systems have the ability to catalyze the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) through surface reactions involving organic dioxin precursors. However, studies have concentrated on the catalytic effects of individual transition metal oxides, while the complex elemental composition of fly ash introduces the possibility of synergistic or inhibiting effects between multiple, catalytically active components. In this study, we have tested fly ash surrogates containing different ratios (by weight) of iron (III) oxide and copper (II) oxide. Such Fe2O3/CuO mixed-oxide surrogates (in the Fe:Cu ratio of 3.5, 0.9 and 0.2 ) were used to study the cooperative effects between two transition metals that are present in high concentrations in most combustion systems and are known to individually catalyze the formation of PCDD/Fs. The presence of both iron and copper oxides increased the oxidative power of the fly ash surrogates in oxygen rich conditions and led to extremely high PCDD/F yields under pyrolytic conditions (up to >5% yield) from 2-monochlorophenol precursor. PCDD/F congener profiles from the mixed oxide samples are similar to results obtained from only CuO, however the total PCDD/F yield increases with increasing Fe2O3 content. Careful analysis of the reaction products and changes to the oxidation states of active metals indicate the CuO surface sites are centers for reaction while the Fe2O3 is affecting the bonds in CuO and increasing the ability of copper centers to form surface-bound radicals that are precursors to PCDD/Fs.
Collapse
Affiliation(s)
- Phillip M Potter
- Department of Environmental Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Xia Guan
- Department of Environmental Sciences, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Slawomir M Lomnicki
- Department of Environmental Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| |
Collapse
|
19
|
Bai ST, Chang SH, Duh JM, Sung FH, Su JS, Chang MB. Characterization of PCDD/Fs and dioxin-like PCBs emitted from two woodchip boilers in Taiwan. CHEMOSPHERE 2017; 189:284-290. [PMID: 28942254 DOI: 10.1016/j.chemosphere.2017.09.080] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 09/14/2017] [Accepted: 09/17/2017] [Indexed: 06/07/2023]
Abstract
This study investigates the formation and removal of PCDD/Fs and dl-PCBs in two woodchips boilers during different operating periods. Results indicate that combustion condition affects PCDD/F and dl-PCB formation within the woodchip combustion process. PCDD/F and dl-PCB concentrations during the start-up period are much higher than those measured during normal operation and shut-down periods due to unstable combustion. PCDD/F and dl-PCB concentrations at APCDs inlet of Plant A are significantly higher than that of Plant B due to the lower combustion temperature (500-850 °C) compared with Plant B (850-925 °C). Major PCDD/F congeners at APCDs inlet of both plants during normal operation are O8CDD, 1,2,3,4,6,7,8-H7CDD and 1,2,3,4,6,7,8-H7CDF, while major dl-PCBs are TeCB-77, PeCB-118 and PeCB-126. The removal efficiencies of PCDD/F and PCBs achieved with the APCDs of Plant A are 95.6% and 88.6%, respectively, while those of Plant B are 99.3% and 94.9%. Possibly, the AC concentration of Plant A exceeds the optimal AC concentration and, PCDD/Fs and dl-PCBs might be formed because the AC injected can supply additional reaction area and carbon source. Also, this may be due to different operating temperatures of APCDs, which affects removal efficiency of PCDD/F and dl-PCB congeners. The emission factors (PCDD/Fs + dl-PCBs) of Plants A and B are calculated as 17.86 and 1.25 μg I-TEQ/ton, respectively. Concentrations of PCDD/Fs in the BF ash of Plants A and B during normal operation are measured as 98.57 and 38.06 ng I-TEQ/g, which are significantly higher than the standard limit (1.0 ng I-TEQ/g) promulgated by Taiwan EPA.
Collapse
Affiliation(s)
- Shih Ting Bai
- Graduate Institute of Environmental Engineering, National Central University, Jhongli, 32001, Taiwan, ROC
| | - Shu Hao Chang
- Graduate Institute of Environmental Engineering, National Central University, Jhongli, 32001, Taiwan, ROC
| | - Jing Min Duh
- Research Laboratories of Green Energy and Environment, Industrial Technology Research Institute, Hsinchu, 32001, Taiwan, ROC
| | - Fu Hsiang Sung
- Research Laboratories of Green Energy and Environment, Industrial Technology Research Institute, Hsinchu, 32001, Taiwan, ROC
| | - Jhen Sheng Su
- Section of Air Quality Protection, Department of Environmental Protection, Taoyuan City Government, Taoyuan, 32001, Taiwan, ROC
| | - Moo Been Chang
- Graduate Institute of Environmental Engineering, National Central University, Jhongli, 32001, Taiwan, ROC.
| |
Collapse
|
20
|
Feld-Cook EE, Bovenkamp-Langlois L, Lomnicki SM. Effect of Particulate Matter Mineral Composition on Environmentally Persistent Free Radical (EPFR) Formation. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:10396-10402. [PMID: 28817261 PMCID: PMC5778880 DOI: 10.1021/acs.est.7b01521] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Environmentally Persistent Free Radicals (EPFRs) are newly discovered, long-lived surface bound radicals that form on particulate matter and combustion borne particulates, such as fly ash. Human exposure to such particulates lead to translocation into the lungs and heart resulting in cardio-vascular and respiratory disease through the production of reactive oxygen species. Analysis of some waste incinerator fly ashes revealed a significant difference between their EPFR contents. Although EPFR formation occurs on the metal domains, these differences were correlated with the altering concentration of calcium and sulfur. To analyze these phenomena, surrogate fly ashes were synthesized to mimic the presence of their major mineral components, including metal oxides, calcium, and sulfur. The results of this study led to the conclusion that the presence of sulfates limits formation of EPFRs due to inhibition or poisoning of the transition metal active sites necessary for their formation. These findings provide a pathway toward understanding differences in EPFR presence on particulate matter and uncover the possibility of remediating EPFRs from incineration and hazardous waste sites.
Collapse
Affiliation(s)
- Elisabeth E. Feld-Cook
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Lisa Bovenkamp-Langlois
- Center for Advanced Microstructures & Devices (CAMD), Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Slawo M. Lomnicki
- Department of Environmental Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| |
Collapse
|
21
|
Pan W, Fu J, Zhang A. Theoretical study on the formation mechanism of pre-intermediates for PXDD/Fs from 2-Bromophenol and 2-Chlorophenol precursors via radical/molecule reactions. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2017; 225:439-449. [PMID: 28302335 DOI: 10.1016/j.envpol.2017.03.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 02/13/2017] [Accepted: 03/02/2017] [Indexed: 06/06/2023]
Abstract
This study investigates reaction pathways for the formation of pre-PXDD/F intermediates via a radical/molecule mechanism. Thermodynamic and kinetic parameters for the combination reactions of 2-bromophenol (2-BP) and 2-chlorophenol (2-CP) precursors with key radical species including the phenoxy radicals, the phenyl radicals and the phenoxyl diradicals were calculated in detail. The couplings of phenoxy radicals with 2-B(C)P tend to produce pre-PXDD intermediates of halogenated o-phenoxyphenol. The combinations of phenyl and phenoxyl diradicals with 2-B(C)P produce two types of structures, i.e., dihydroxybiphenyl and o-phenoxyphenyl, which exclusively act as prestructures of PXDFs. These condensation reactions, especially those involving the phenyl C atom sites in phenyl and phenoxyl diradicals, are proven to be both thermodynamically and kinetically favorable and are nearly comparable with the corresponding steps involved in the radical/radical reactions. Most importantly, reactions of phenyl and phenoxyl diradicals with halogenated phenols solely lead to the formation of PXDFs, which to some extent provides a plausible explanation for the high PXDF-to-PXDD ratios in the real environment. Therefore, our study reveals the pivotal role of the radical/molecule mechanism in homogeneous gas-phase PXDD/F formation, especially in PXDF formation. The present results fill in a knowledge gap that has hitherto existed regarding dioxin formation and improve our understanding of PXDD/F formation characteristics in the environment.
Collapse
Affiliation(s)
- Wenxiao Pan
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China
| | - Jianjie Fu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, PR China
| | - Aiqian Zhang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, PR China; College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100190, PR China.
| |
Collapse
|
22
|
Yang L, Liu G, Zheng M, Zhao Y, Jin R, Wu X, Xu Y. Molecular Mechanism of Dioxin Formation from Chlorophenol based on Electron Paramagnetic Resonance Spectroscopy. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2017; 51:4999-5007. [PMID: 28358500 DOI: 10.1021/acs.est.7b00828] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Few studies have investigated the free radical intermediates involved in the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) from chlorophenol. This study clarified the reaction pathways during thermochemical formation of PCDDs from 2,3,6-trichlorophenol (TCP) over a Cu(II)O/silica matrix, which was used to simulate fly ash, at 298-523 K. The reaction was studied using electron paramagnetic resonance (EPR) spectroscopy and theoretical calculations. In situ EPR indicated the TCP radical (TCPR) formed by hydrogen abstraction of TCP. Five elementary processes including dimerization of TCPR, ortho-chloride abstraction, Smiles rearrangement, ring closure, and intra-annular elimination of Cl were proposed to occur during formation of PCDDs. The proposed mechanism was further confirmed by the detection of PCDD products from thermochemical experiments in a tube furnace. Several dominant congeners, including 1,2,6,9-tetrachlorodibenzo-p-dioxin (TeCDD), 1,2,6,7-TeCDD, 1,2,8,9-TeCDD, and 1,4,6,9-TeCDD were detected by gas chromatography/quadrupole time-of-flight mass spectrometry, and further confirmed by gas chromatography/high resolution mass spectrometry. The detected PCDD products agree with the proposed PCDD formation mechanism. Relatively high temperatures were found to lead to dechlorination of TCPR to form phenoxy radicals in addition to PCDD/Fs. These radicals will be attached to particles, which will increase their lifetimes. These reactions were further verified by molecular orbital theory calculations. The discovery of persistent phenoxy radicals is of environmental significance because of their potential toxicity. The details of this mechanism could be used for controlling PCDD/F formation during industrial thermal processes.
Collapse
Affiliation(s)
- Lili Yang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Guorui Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Minghui Zheng
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Yuyang Zhao
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Rong Jin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Xiaolin Wu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Yang Xu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| |
Collapse
|
23
|
Zhan MX, Fu JY, Havukainen J, Chen T, Li XD, Yan JH, Buekens A. Recycling ash into the first stage of cyclone pre-heater of cement kiln. WASTE MANAGEMENT (NEW YORK, N.Y.) 2016; 56:229-237. [PMID: 27389860 DOI: 10.1016/j.wasman.2016.06.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2016] [Revised: 04/10/2016] [Accepted: 06/18/2016] [Indexed: 06/06/2023]
Abstract
Fly ash collected from the bag filter could be recycled into the first stage of the cyclone pre-heater of the cement kiln, resulting in the possible enrichment of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). In this study, soxhlet fly ash (SFA) and raw meal (RM) were selected as the basis for the PCDD/F formation experiments. The levels of 2,3,7,8-PCDD/Fs formed on the SFA and RM were observed to be 2550pg/g (157pg I-TEQ/g) and 1142pg/g (55pg I-TEQ/g), respectively. While less 2,3,7,8-PCDD/Fs was detected when SFA was mixed with RM, suggesting that recycling cement kiln ash would not largely increase the concentration of PCDD/Fs in flue gas. Furthermore, the possible influencing factors on the PCDD/F formation were also investigated. The formation of 2,3,7,8-PCDD/Fs was up to 10,871pg/g (380pg I-TEQ/g) with the adding of CuCl2, which was much higher than the results of CuO and activated carbon. Most importantly, the homologue, congener and gas/particle distribution of PCDD/Fs indicated that de novo synthesis was the dominant PCDD/F formation pathway for SFA. Lastly, principal component analysis (PCA) was also conducted to identify the relationship between the compositions of reactant and the properties of PCDD/Fs produced.
Collapse
Affiliation(s)
- Ming-Xiu Zhan
- State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, China
| | - Jian-Ying Fu
- China United Engineering Corporation, Hangzhou 310052, China
| | - Jouni Havukainen
- Lappeenranta University of Technology, Laboratory of Environmental Engineering, P.O. Box 20, FI-53851 Lappeenranta, Finland
| | - Tong Chen
- State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, China.
| | - Xiao-Dong Li
- State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, China
| | - Jian-Hua Yan
- State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, China
| | - Alfons Buekens
- State Key Laboratory of Clean Energy Utilization, Institute for Thermal Power Engineering, Zhejiang University, China
| |
Collapse
|
24
|
Wang M, Liu G, Jiang X, Zheng M, Yang L, Zhao Y, Jin R. Thermochemical Formation of Polybrominated Dibenzo-p-Dioxins and Dibenzofurans Mediated by Secondary Copper Smelter Fly Ash, and Implications for Emission Reduction. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:7470-7479. [PMID: 27347728 DOI: 10.1021/acs.est.6b02119] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Heterogeneous reactions mediated by fly ash are important to polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/Fs) formation. However, the formation of polybrominated dibenzo-p-dioxins and dibenzofurans (PBDD/Fs) through heterogeneous reactions is not yet well understood. Experiments were performed to investigate the thermochemical formation of PBDD/Fs at 150-450 °C through heterogeneous reactions on fly ash from a secondary copper smelter. The maximum PBDD/F concentration was 325 times higher than the initial PBDD/F concentration in the fly ash. The PBDD/F concentration after the experiment at 150 °C was five times higher than the initial concentration. PBDD/Fs have not previously been found to form at such a low temperature. Secondary-copper-smelter fly ash clearly promoted PBDD/F formation, and this conclusion was supported by the low activation energies that were found in Arrhenius's law calculations. Thermochemical formation of PBDD/Fs mediated by fly ash deposited in industrial facilities could explain "memory effects" that have been found for PCDD/Fs and similar compounds released from industrial facilities. Abundant polybrominated diphenyl ethers (PBDEs) that were formed through fly ash-mediated reactions could be important precursors for PBDD/Fs also formed through fly ash-mediated reactions. The amounts of PBDEs that formed through fly ash-mediated reactions suggested that secondary copper smelters could be important sources of reformed PBDEs.
Collapse
Affiliation(s)
- Mei Wang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Guorui Liu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Xiaoxu Jiang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Minghui Zheng
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Lili Yang
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Yuyang Zhao
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| | - Rong Jin
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences , P.O. Box 2871, Beijing 100085, China
- University of Chinese Academy of Sciences , Beijing 100049, China
| |
Collapse
|
25
|
Dugas TR, Lomnicki S, Cormier SA, Dellinger B, Reams M. Addressing Emerging Risks: Scientific and Regulatory Challenges Associated with Environmentally Persistent Free Radicals. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2016; 13:ijerph13060573. [PMID: 27338429 PMCID: PMC4924030 DOI: 10.3390/ijerph13060573] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/06/2016] [Revised: 05/25/2016] [Accepted: 05/31/2016] [Indexed: 12/30/2022]
Abstract
Airborne fine and ultrafine particulate matter (PM) are often generated through widely-used thermal processes such as the combustion of fuels or the thermal decomposition of waste. Residents near Superfund sites are exposed to PM through the inhalation of windblown dust, ingestion of soil and sediments, and inhalation of emissions from the on-site thermal treatment of contaminated soils. Epidemiological evidence supports a link between exposure to airborne PM and an increased risk of cardiovascular and pulmonary diseases. It is well-known that during combustion processes, incomplete combustion can lead to the production of organic pollutants that can adsorb to the surface of PM. Recent studies have demonstrated that their interaction with metal centers can lead to the generation of a surface stabilized metal-radical complex capable of redox cycling to produce ROS. Moreover, these free radicals can persist in the environment, hence their designation as Environmentally Persistent Free Radicals (EPFR). EPFR has been demonstrated in both ambient air PM2.5 (diameter < 2.5 µm) and in PM from a variety of combustion sources. Thus, low-temperature, thermal treatment of soils can potentially increase the concentration of EPFR in areas in and around Superfund sites. In this review, we will outline the evidence to date supporting EPFR formation and its environmental significance. Furthermore, we will address the lack of methodologies for specifically addressing its risk assessment and challenges associated with regulating this new, emerging contaminant.
Collapse
Affiliation(s)
- Tammy R Dugas
- Department of Comparative Biomedical Sciences, LSU School of Veterinary Medicine, Baton Rouge, LA 70803, USA.
| | - Slawomir Lomnicki
- Department of Environmental Sciences, Louisiana State University and A & M College, Baton Rouge, LA 70803, USA.
| | - Stephania A Cormier
- Department of Pediatrics, University of Tennessee Health Sciences Center and Children's Foundation Research Institute, Le Bonheur Children's Hospital, Memphis, TN 38103, USA.
| | - Barry Dellinger
- Department of Chemistry, Louisiana State University and A & M College, Baton Rouge, LA 70803, USA.
| | - Margaret Reams
- Department of Environmental Sciences, Louisiana State University and A & M College, Baton Rouge, LA 70803, USA.
| |
Collapse
|
26
|
Wang SJ, He PJ, Lu WT, Shao LM, Zhang H. Amino Compounds as Inhibitors of De Novo Synthesis of Chlorobenzenes. Sci Rep 2016; 6:23197. [PMID: 27034259 PMCID: PMC4817035 DOI: 10.1038/srep23197] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 03/02/2016] [Indexed: 11/09/2022] Open
Abstract
The inhibitory effects of four amino compounds on the formation of chlorobenzenes (CBzs)--dioxin precursors and indicators, and the inhibitory mechanisms were explored. The results show NH4H2PO4 can decrease the total yields of CBzs (1,2di-CBz, 1,3di-CBz, 1,4di-CBz, penta-CBz and hexa-CBz) by 98.1%±1.6% and 96.1%±0.7% under air and nitrogen flow. The inhibitory effects indicated by the total yields of CBzs follow the order NH4H2PO4 > NH4HF2 > (NH4)2SO4 > NH4Br under air flow and NH4H2PO4 ≈ (NH4)2SO4 ≈ NH4HF2 >NH4Br under nitrogen flow. The inhibition mechanism revealed by thermal analysis that CuCl2 was converted to CuPO3 by reacting with NH4H2PO4 below 200 °C, which can block the transfer of chlorine and formation of C-Cl bonds at 350 °C. The effects of the other three inhibitors were weaker because their reactions with CuCl2, which form other copper compounds, and the reaction of CuCl2 with carbon, which forms C-Cl bonds, were almost simultaneous and competitive. Oxygen influenced the yield of CBzs obviously, and the total yield of five CBzs sharply increased with oxygen. Because of their high efficiency, low environmental impact, low cost, and availability, amino compounds--especially NH4H2PO4--can be utilized as inhibitors of CBzs during incineration.
Collapse
Affiliation(s)
- Si-Jia Wang
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China.,Institute of Waste Treatment and Reclamation, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China
| | - Pin-Jing He
- Institute of Waste Treatment and Reclamation, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China.,Centre for the Technology Research and Training on Household Waste in Small Towns &Rural Area, Ministry of Housing and Urban-Rural Development of P. R. China, 1239 Siping Road, Shanghai 200092, P. R. China
| | - Wen-Tao Lu
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China.,Institute of Waste Treatment and Reclamation, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China
| | - Li-Ming Shao
- Institute of Waste Treatment and Reclamation, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China.,Centre for the Technology Research and Training on Household Waste in Small Towns &Rural Area, Ministry of Housing and Urban-Rural Development of P. R. China, 1239 Siping Road, Shanghai 200092, P. R. China
| | - Hua Zhang
- State Key Laboratory of Pollution Control and Resources Reuse, Tongji University, 1239 Siping Road, Shanghai 200092, P. R. China
| |
Collapse
|
27
|
Potter PM, Dellinger B, Lomnicki SM. Contribution of aluminas and aluminosilicates to the formation of PCDD/Fs on fly ashes. CHEMOSPHERE 2016; 144:2421-6. [PMID: 26615490 PMCID: PMC4695248 DOI: 10.1016/j.chemosphere.2015.11.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2015] [Revised: 10/28/2015] [Accepted: 11/03/2015] [Indexed: 05/23/2023]
Abstract
Chlorinated aromatics undergo surface-mediated reactions with metal oxides to form Environmentally Persistent Free Radicals (EPFRs) which can further react to produce polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs). Previous work using laboratory-made fly ash surrogates composed of transition metal oxides deposited on silica powder has confirmed their ability to mimic fly ash in the production of PCDD/Fs. However, little is known about the propensity of aluminas and aluminosilicates, other components of fly ash, to form PCDD/Fs. A fly ash sample containing both alumina and mullite, an aluminosilicate, was tested for PCDD/F formation ability and compared to PCDD/F yields from the thermal degradation of 2-monochlorophenol (2-MCP) precursor over γ-alumina, α-alumina, and mullite. A packed-bed flow reactor was used to investigate the thermal degradation of 2-MCP over the various catalysts at 200-600 °C. Fly ash gave similar PCDD/F yields to surrogates made with similar transition metal content. γ-alumina, which is thermodynamically unfavorable, was very catalytically active and gave low PCDD/F yields despite a high destruction of 2-MCP. Mullite and α-alumina, the thermodynamically favorable form of alumina, yielded higher concentrations of dioxins and products with a higher degree of chlorine substitution than γ-alumina. The data suggest that certain aluminas and aluminosilicates, commonly found in fly ash, are active catalytic surfaces in the formation of PCDD/Fs in the post-flame cool zones of combustion systems and should be considered as additional catalytic surfaces active in the process.
Collapse
Affiliation(s)
- Phillip M Potter
- Department of Chemistry, Louisiana State University, Baton Rouge, LA, USA
| | - Barry Dellinger
- Department of Chemistry, Louisiana State University, Baton Rouge, LA, USA
| | - Slawomir M Lomnicki
- Department of Environmental Sciences, Louisiana State University, Baton Rouge, LA, USA.
| |
Collapse
|
28
|
Patterson MC, Thibodeaux CA, Kizilkaya O, Kurtz RL, Poliakoff ED, Sprunger PT. Electronic signatures of a model pollutant-particle system: chemisorbed phenol on TiO₂(110). LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:3869-3875. [PMID: 25774565 PMCID: PMC4407492 DOI: 10.1021/acs.langmuir.5b00030] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Environmentally persistent free radicals (EPFRs) are a class of composite organic/metal oxide pollutants that have recently been discovered to form from a wide variety of substituted benzenes chemisorbed to commonly encountered oxides. Although a qualitative understanding of EPFR formation on particulate metal oxides has been achieved, a detailed understanding of the charge transfer mechanism that must accompany the creation of an unpaired radical electron is lacking. In this study, we perform photoelectron spectroscopy and electron energy loss spectroscopy on a well-defined model system-phenol chemisorbed on TiO2(110) to directly observe changes in the electronic structure of the oxide and chemisorbed phenol as a function of adsorption temperature. We show strong evidence that, upon exposure at high temperature, empty states in the TiO2 are filled and the phenol HOMO is depopulated, as has been proposed in a conceptual model of EPFR formation. This experimental evidence of charge transfer provides a deeper understanding of the EPFR formation mechanism to guide future experimental and computational studies as well as potential environmental remediation strategies.
Collapse
Affiliation(s)
- Matthew C. Patterson
- Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803
- Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803
| | - Chad A. Thibodeaux
- Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803
| | - Orhan Kizilkaya
- Center for Advanced Microstructures and Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, LA 70806
| | - Richard L. Kurtz
- Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803
- Center for Advanced Microstructures and Devices, Louisiana State University, 6980 Jefferson Highway, Baton Rouge, LA 70806
| | - E. D. Poliakoff
- Department of Chemistry, Louisiana State University, 232 Choppin Hall, Baton Rouge, LA 70803
| | - Phillip T. Sprunger
- Department of Physics and Astronomy, Louisiana State University, 202 Nicholson Hall, Baton Rouge, LA 70803
| |
Collapse
|
29
|
Li Y, Wang H, Jiang L, Zhang W, Li R, Chi Y. HCl and PCDD/Fs emission characteristics from incineration of source-classified combustible solid waste in fluidized bed. RSC Adv 2015. [DOI: 10.1039/c5ra08722h] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Adding different quantities of CaO in combustible solid waste can inhibit the production of PCDD/Fs during incineration.
Collapse
Affiliation(s)
- Yanji Li
- Clean Energy Key Laboratory of Liaoning
- Shenyang Aerospace University
- Shenyang 110136
- China
- State Key Laboratory Clean Energy Utilization
| | - Huihui Wang
- Clean Energy Key Laboratory of Liaoning
- Shenyang Aerospace University
- Shenyang 110136
- China
| | - Lu Jiang
- Clean Energy Key Laboratory of Liaoning
- Shenyang Aerospace University
- Shenyang 110136
- China
| | - Wei Zhang
- Clean Energy Key Laboratory of Liaoning
- Shenyang Aerospace University
- Shenyang 110136
- China
| | - Rundong Li
- Clean Energy Key Laboratory of Liaoning
- Shenyang Aerospace University
- Shenyang 110136
- China
| | - Yong Chi
- State Key Laboratory Clean Energy Utilization
- Zhejiang University
- Hangzhou 310027
- China
| |
Collapse
|
30
|
Nganai S, Dellinger B, Lomnicki S. PCDD/PCDF ratio in the precursor formation model over CuO surface. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2014; 48:13864-70. [PMID: 25372621 PMCID: PMC4255659 DOI: 10.1021/es504253w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The discrepancies between polychlorinated dibenzo-p-dioxin to polychlorinated dibenzofuran (PCDD to PCDF) ratios in laboratory and field studies in the exhaust of combustion sources are not fully explained by available formation models. In this paper we present the results of experimental studies of the surface mediated formation of PCDD/F at the conditions mimicking the combustion cool zone from a mixture of 1,2-dichlorobenzene (1,2-DCBz) and 2-monochlorophenol (2-MCP) over a model surface consisting of 5% CuO/Silica. The PCDD to PCDF ratio was found to be strongly dependent on the ratio of chlorinated benzenes to chlorinated phenols and oxygen content. The higher the 1,2-DCBz to 2-MCP ratio, the lower the PCDD to PCDF ratio. PCDFs are formed predominantly from chlorinated benzenes, while chlorinated phenols are responsible for majority of PCDDs. These laboratory results are in general agreement with full-scale measurement and can be used to improve predictive models of PCDD/F formation.
Collapse
Affiliation(s)
- Shadrack Nganai
- Louisiana
State University, Department of Chemistry, 232 Choppin Hall, Baton Rouge, Louisiana 70803, United States
| | - Barry Dellinger
- Louisiana
State University, Department of Chemistry, 232 Choppin Hall, Baton Rouge, Louisiana 70803, United States
| | - Slawo Lomnicki
- Louisiana
State University, Department of Environmental
Sciences, 1251 Energy, Coast and Environment
Building, Baton Rouge, Louisiana 70803, United States
- E-mail:
| |
Collapse
|
31
|
Ryu JY, Kim DH, Jang SH. Is chlorination one of the major pathways in the formation of polychlorinated naphthalenes (PCNs) in municipal solid waste combustion? ENVIRONMENTAL SCIENCE & TECHNOLOGY 2013; 47:2394-2400. [PMID: 23373612 DOI: 10.1021/es304735n] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
The chlorination patterns of unsubstituted naphthalene were studied using a laminar flow reactor with a 1 cm particle bed of 0.5% (mass) copper(II) chloride (CuCl2) mixed with silicon dioxide (SiO2), operated over a temperature range of 100 to 400 °C and at gas velocities of 2.7 and 0.32 cm/s. The polychlorinated naphthalene (PCN) yield increased until a temperature reached at 250 °C, where a peak yield of 3.07% (percent of naphthalene input, carbon basis) was observed. All PCN homologue groups, mono- through octa-chlorinated naphthalenes, were observed. To test the hypothesis that PCNs in combustion processes are formed via chlorination pathways, the PCN homologue and isomer patterns from the experiments were compared with those observed in municipal solid waste combustion (MSW) incinerators. PCN congeners with 1,4-substituents dominated formation in the naphthalene chlorination experiments, whereas 2,3-substituents were major congeners in both MSW combustion flue gas and fly ash samples. These results suggest that contrary to the hypothesis, chlorination is not a primary PCN formation route in either the flue gas or fly ash from MSW combustion. Even so, naphthalene chlorination pathways presented in this paper provide an improved means for evaluating PCN formation mechanisms in combustion processes.
Collapse
Affiliation(s)
- Jae-Yong Ryu
- Division for Industrial and Environmental Research, Korea Atomic Energy Research Institute (KAERI) , 1266, Sinjeong-dong, Jeongeup-si, Jeollabuk-do, 580-185, Korea
| | | | | |
Collapse
|
32
|
Hu J, Zheng M, Nie Z, Liu W, Liu G, Zhang B, Xiao K. Polychlorinated dibenzo-p-dioxin and dibenzofuran and polychlorinated biphenyl emissions from different smelting stages in secondary copper metallurgy. CHEMOSPHERE 2013; 90:89-94. [PMID: 23040645 DOI: 10.1016/j.chemosphere.2012.08.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Accepted: 08/02/2012] [Indexed: 06/01/2023]
Abstract
Secondary copper production has received much attention for its high emissions of polychlorinated dibenzo-p-dioxin and dibenzofuran (PCDD/F) reported in previous studies. These studies focused on the estimation of total PCDD/F and polychlorinated biphenyl (PCB) emissions from secondary copper smelters. However, large variations in PCDD/F and PCB emissions reported in these studies were not analyzed and discussed further. In this study, stack gas samples at different smelting stages (feeding-fusion, oxidation and deoxidization) were collected from four plants to investigate variations in PCDD/F and PCB emissions and characteristics during the secondary copper smelting process. The results indicate that PCDD/F emissions occur mainly at the feeding-fusion stage and these emissions contribute to 54-88% of the total emissions from the secondary copper smelting process. The variation in feed material and operating conditions at different smelting stages leads to the variation in PCDD/F emissions during the secondary copper smelting process. The total PCDD/F and PCB discharge (stack gas emission+fly ash discharge) is consistent with the copper scrap content in the raw material in the secondary copper smelters investigated. On a production basis of 1 ton copper, the total PCDD/F and dl-PCB discharge was 102, 24.8 and 5.88 μg TEQ t(-1) for the three plants that contained 100%, 30% and 0% copper scrap in their raw material feed, respectively.
Collapse
Affiliation(s)
- Jicheng Hu
- State Key Laboratory of Environmental Chemistry and Ecotoxicology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | | | | | | | | | | | | |
Collapse
|
33
|
Herring MP, Potter PM, Wu H, Lomnicki S, Dellinger B. Fe 2O 3 nanoparticle mediated molecular growth and soot inception from the oxidative pyrolysis of 1-methylnaphthalene. PROCEEDINGS OF THE COMBUSTION INSTITUTE. INTERNATIONAL SYMPOSIUM ON COMBUSTION 2013; 34:1749-1757. [PMID: 25530732 PMCID: PMC4269167 DOI: 10.1016/j.proci.2012.07.057] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
Abstract
While it is well documented iron oxide can reduce soot through burnout in the oxidative regions of flames, it may also impact molecular growth and particle inception. The role of Fe2O3 nanoparticles in mass growth of soot from 1-methylnapthalene (1-MN) was studied in a dual-zone, high-temperature flow reactor. An iron substituted, dendrimer template was oxidized in the first zone to generate ~5 nm Fe2O3 nanoparticles, which were seeded into the second zone of the flow reactor containing 1-MN at 1100°C and ϕ = 1.4-5.0. Enhanced molecular growth in the presence of Fe2O3 nanoparticles resulted in increased yields of polycyclic aromatic hydrocarbons (PAH) and soot compared to purely gas-phase reactions of 1-MN at identical fuel-air equivalence ratios. This also resulted in an increase in soot-number concentration and a slight shift to smaller particles with increasing addition (from no addition to 3 mM) of Fe2O3. Introduction of Fe2O3 nanoparticles resulted in the formation of stabilization of environmentally persistent free radicals (EPFRs), including benzyl, phenoxyl, or semiquinone-type radicals as well as carbon-centered radicals, such as cyclopentadienyl or a delocalized electron in a carbon matrix. At the high concentrations in the flow reactor, these resonance-stabilized free radicals can undergo surface-mediated, radical-radical, molecular growth reactions which may contribute to molecular growth and soot particle inception.
Collapse
Affiliation(s)
- M. Paul Herring
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Phillip M. Potter
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Hongyi Wu
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Slawomir Lomnicki
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
| | - Barry Dellinger
- Department of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA
| |
Collapse
|
34
|
Kibet J, Khachatryan L, Dellinger B. Molecular products and radicals from pyrolysis of lignin. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2012; 46:12994-13001. [PMID: 23131040 DOI: 10.1021/es302942c] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Thermal degradation of lignin under two reaction regimes (pyrolysis in N(2) and oxidative pyrolysis in 4% O(2) in N(2)) has been investigated in a tubular, isothermal, flow-reactor over the temperature range 200-900 °C at a residence time of 0.2 s. Two experimental protocols were adopted: (1) Partial pyrolysis in which the same lignin sample was continuously pyrolyzed at each temperature and (2) conventional pyrolysis, in which new lignin samples were pyrolyzed at each pyrolysis temperature. The results identified common relationships between the two modes of experiments, as well as some differences. The majority of products from partial pyrolysis peaked between 300 and 500 °C, whereas for conventional pyrolysis reaction products peaked between 400 and 500 °C. The principal products were syringol (2,6-dimethoxy phenol), guaiacol (2-methoxy phenol), phenol, and catechol. Of the classes of compounds analyzed, the phenolic compounds were the most abundant, contributing over 40% of the total compounds detected. Benzene, styrene, and p-xylene were formed in significant amounts throughout the entire temperature range. Interestingly, six ringed polycyclic aromatic hydrocarbons were formed during partial pyrolysis. Oxidative pyrolysis did not result in large differences from pyrolysis; the main products still were syringol, guaiacol, phenol, the only significant difference being the product distribution peaked between 200 and 400 °C. For the first time, low temperature matrix isolation electron paramagnetic resonance was successfully interfaced with the pyrolysis reactor to elucidate the structures of the labile reaction intermediates. The EPR results suggested the presence of methoxyl, phenoxy, and substituted phenoxy radicals as precursors for formation of major products; syringol, guaiacol, phenols, and substituted phenols.
Collapse
Affiliation(s)
- J Kibet
- Department of Chemistry, Louisiana State University, Baton Rouge, Louisiana 70803, USA
| | | | | |
Collapse
|