title: Thermal dechlorination of heavily PCB-contaminated soils from a sealed site of PCB-containing electrical equipment.
abstract: A large amount of soils are contaminated by leakage of polychlorinated biphenyls (PCBs) from sealed-up PCB-containing electrical equipment in China. Thermal dechlorination of soils contaminated with PCBs at a level of 108 mg g(-1) and PCB77 (3,3',4,4'-tetrachlorobiphenyl) as a model isomer in conjunction with calcium oxide was investigated in this study. The PCB dechlorination rate improved with increased temperature and time. The highest dechlorination rate was 85.3 %, and temperature was the main influencing factor. Pentachlorobiphenyl and tetrachlorobiphenyl in soils decreased or disappeared in response to treatment at 350 and 400 °C for 4 h, while monochlorinated biphenyl and biphenyl were detected after the reaction, indicating the presence of a dechlorination/hydrogenation pathway. Discrepancy in chlorine balance was observed after low-temperature thermal dechlorination. The species of dechlorination products were identified as amorphous carbon containing a crystalline graphite plane structure and a carbonyl group-containing polymerized product, demonstrating the existence of a dechlorination/polymerization pathway. The yield of amorphous carbon and high-molecular-weight intermediates increased with heating time. The results showed that the discrepancy in chlorine balance was because of the generation of polymerized products and undetected intermediates.
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China. gaoxb@craes.org.cn.
authors.forename: Xingbao
authors.initials: X
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.|School of River and Ocean Engineering, Chongqing Jiaotong University, Chongqing, 400074, China.
authors.forename: Bingjing
authors.initials: B
authors.lastname: Ji
authors.affiliation: State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
authors.forename: Qifei
authors.initials: Q
authors.lastname: Huang
mesh_terms: D002681:China; D002713:Chlorine / Q000737:chemistry; D059029:Electronic Waste / Q000009:adverse effects / Q000032:analysis; D004784:Environmental Monitoring; D054879:Halogenation; D006358:Hot Temperature; D011078:Polychlorinated Biphenyls / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*
chemical_list: D012987:Soil; D012989:Soil Pollutants; D002713:Chlorine; D011078:Polychlorinated Biphenyls; C028451:3,4,3',4'-tetrachlorobiphenyl
keywords: Chlorine balance; Contaminated soils; Hydrogenation; Polychlorinated biphenyls; Polymerization; Thermal dechlorination