title: Thermal degradation of hexachlorobenzene in the presence of calcium oxide at 340-400 °C.
abstract: Hexachlorobenzene (HCB) in the milligram range was co-heated with calcium oxide (CaO) powder in sealed glass ampoules at 340-400 °C. The heated samples were characterized and analyzed by Raman spectroscopy, elemental analysis, gas chromatography/mass spectrometry, ion chromatography, and thermal/optical carbon analysis. The degradation products of HCB were studied at different temperatures and heated times. The amorphous carbon was firstly quantitatively evaluated and was thought to be important fate of the C element of HCB. The yield of amorphous carbon in products increased with heating time, for samples treated for 8h at 340, 380 °C and 400 °C, the value were 17.5%, 34.8% and 50.2%, respectively. After identification of the dechlorination products, the HCB degradation on CaO at 340-400 °C was supposed to through dechlorination/polymerization pathway, which is induced by electron transfer, generate chloride ions and form high-molecular weight intermediates with significant levels of both hydrogen and chlorine, and finally form amorphous carbon. Higher temperature was beneficial for the dechlorination/polymerization efficiency. The results are helpful for clarifying the reaction mechanism for thermal degradation of chlorinated aromatics in alkaline matrices.
authors.affiliation: School of Environment, Tsinghua University, Beijing 100084, China. Electronic address: yinkq06@mails.tsinghua.edu.cn.
authors.forename: Keqing
authors.initials: K
authors.lastname: Yin
authors.forename: Xingbao
authors.initials: X
authors.lastname: Gao
authors.forename: Yifei
authors.initials: Y
authors.lastname: Sun
authors.forename: Lei
authors.initials: L
authors.lastname: Zheng
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
mesh_terms: D017610:Calcium Compounds / Q000737:chemistry*; D004785:Environmental Pollutants / Q000032:analysis / Q000737:chemistry*; D006581:Hexachlorobenzene / Q000032:analysis / Q000737:chemistry*; D006358:Hot Temperature; D017745:Incineration; D008956:Models, Chemical; D010087:Oxides / Q000737:chemistry*
chemical_list: D017610:Calcium Compounds; D004785:Environmental Pollutants; D010087:Oxides; D006581:Hexachlorobenzene; C016538:lime
keywords: Calcium oxide; Hexachlorobenzene; Polymerization; Thermal degradation