Synergetic inhibition of PCDD/F formation from pentachlorophenol by mixtures of urea and calcium oxide

Qianqian Li; Liewu Li; Guijin Su; Xinchen Huang; Yanhui Zhao; Binke Li; Xue Miao; Minghui Zheng

doi:10.1016/j.jhazmat.2016.05.090

Synergetic inhibition of PCDD/F formation from pentachlorophenol by mixtures of urea and calcium oxide

J Hazard Mater. 2016 Nov 5:317:394-402. doi: 10.1016/j.jhazmat.2016.05.090. Epub 2016 Jun 1.

Authors

Qianqian Li¹, Liewu Li¹, Guijin Su², Xinchen Huang¹, Yanhui Zhao¹, Binke Li¹, Xue Miao¹, Minghui Zheng¹

Affiliations

¹ 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.
² 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. Electronic address: gjsu@rcees.ac.cn.

PMID: 27318736
DOI: 10.1016/j.jhazmat.2016.05.090

Abstract

Chlorophenols are structurally similar to PCDD/Fs and have been considered as highly potential precursors for PCDD/Fs formation. The suppressing effects of PCDD/F formation from pentachlorophenol (PCP) were investigated on various mass ratios of CaO and urea. The total concentration of 2,3,7,8-PCDD/Fs, mostly dominated by OCDD, was determined to be 48.58-10186ng/mg in inhibitor-reaction systems, being much lower than that in blank reaction system (75654ng/mg). Interestingly, compared with pure CaO and urea reaction system, the concentration and TEQ of formed 2,3,7,8-PCDD/Fs in mixed urea/CaO reaction system were lower, especially with 5-20% urea reaction systems being respectively at decrease by 96.5-99.4% and 99.2-99.7%. The suppression efficiency of TEQ in 5-20% urea reaction systems could be always approximately 100% under 250-350°C. These results suggested that mixed inhibitors, especially 5-20% urea inhibitors, have a synergetic inhibition effect for PCDD/Fs formation from PCP. Mixed inhibitor generated several intermediates, involving CO2, H2O, NH3, Ca(OH)2, CaCO3, HNCO, biuret and ammelide. The complex between PCP and Ca, N-doped species, lower chlorinated phenols and benzenediol, and organic acids were also determined. Synergetic inhibition mechanism may be attributed to accelerated facilitation of acid-base reaction and N doping. The decomposition of PCP itself also contributes to prevent PCDD/Fs formation.

Keywords: CaO; PCDD/Fs; Pentachlorophenol; Synergetic suppression; Urea.