title: Kinetics of reductive dechlorination of 1,2,3,4-TCDD in the presence of zero-valent zinc.
abstract: Polychlorinated dibenzo-p-dioxins (PCDDs) are toxic and widespread persistent organic pollutants (POPs). Cost-effective technologies for destroying or detoxifying PCDDs are in high demand. The overall purpose of this study was to develop a zero-valent zinc based technology for transforming toxic PCDDs to less- or non-toxic forms. We measured the dechlorination rates of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) in the presence of zero-valent zinc under aqueous conditions, identified the daughter compounds of the reaction, and constructed possible pathways for the reactions. The reaction rates of daughter compounds with zero-valent zinc were also measured independently. Our results showed that the zero-valent zinc is a suitable candidate for reducing PCDDs. Reductive dechlorination of 1,2,3,4-TCDD was stepwise and complete to dibenzo-p-dioxin (DD) mainly via 1,2,4-trichlorodibenzo-p-dioxin (1,2,4-TrCDD), 1,3-dichlorodibenzo-p-dioxin (1,3-DCDD), 1-chlorodibenzo-p-dioxin (1-MCDD) to DD and via 1,2,4-TrCDD, 2,3-dichlorodibenzo-p-dioxin (2,3-DCDD), 2-chlorodibenzo-p-dioxin (2-MCDD) to DD. In each separate system, the observed half-lives of 1,2,3,4-TCDD, 1,2,3-TrCDD, 1,2,4-TrCDD, 1,2-DCDD, 1,3-DCDD, 1,4-DCDD and 2,3-DCDD are 0.56, 2.62, 5.71, 24.93, 41.53, 93.67 and 169.06 h respectively. The tendency of rate constant follows TCDD>TrCDD>DCDD. Our results suggest that zero-valent zinc is a suitable candidate for rapidly reducing highly chlorinated PCDDs to less or non-chlorinated daughter products.
authors.affiliation: Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Wushan, Guangzhou 510640, People's Republic of China.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Wang
authors.forename: Weilin
authors.initials: W
authors.lastname: Huang
authors.forename: Donna E
authors.initials: DE
authors.lastname: Fennell
authors.forename: Ping'an
authors.initials: P
authors.lastname: Peng
mesh_terms: D002713:Chlorine / Q000737:chemistry*; D004787:Environmental Pollution / Q000517:prevention & control*; D007700:Kinetics; D008956:Models, Chemical; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000737:chemistry; D014867:Water / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
chemical_list: D000072317:Polychlorinated Dibenzodioxins; D014867:Water; D002713:Chlorine; C092155:1,2,3,4-tetrachlorodibenzodioxin; D015032:Zinc