title: Rapid transformation of 1,2,3,4-TCDD by Pd/Fe catalysts.
abstract: This study investigated reductive dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin (1,2,3,4-TCDD) in the presence of Pd/Fe, Cu/Fe and Ni/Fe bimetallic catalysts or zero-valent iron (ZVI) under aqueous and ambient temperature conditions. It was found that the Pd/Fe catalyst can rapidly transform 1,2,3,4-TCDD to chlorine-free dibenzo-p-dioxin (DD) with >95% of conversion and half lives on the order of 5h, whereas Cu/Fe, Ni/Fe and ZVI were not reactive over 10d. The dechlorination of 1,2,3,4-TCDD in the Pd/Fe systems was found to be stepwise, with 1,2,3-tri (TrCDD), 1,2-di (DCDD), and mono-(MCDD) chlorodibenzo-p-dioxins as the three intermediate products at low concentrations and DD as the final and dominant product. The reaction rate of 1,2,3,4-TCDD dechlorination appeared to decrease as the coverage of palladium on iron particle surface increases from 0.0060 mol% to 0.0228 mol%. Compared to our prior study of reductive dechlorination of 1,2,3,4-TCDD with zero valent zinc (ZVZ) as the reductant, the reactions with Pd/Fe bimetallic materials were relatively slower for TCDD, but much faster for TrCDDs and DCDDs, yielding DD as the major product. The study suggested that Pd/Fe bimetallic catalyst-based reactions may be suitable for rapid decontamination of polychlorinated dibenzo-p-dioxin/dibenzofuran (PCDD/F) polluted soils and sediments.
authors.affiliation: CAS Key Laboratory of Marginal Sea Geology, South China Sea Institute of Oceanography, Chinese Academy of Sciences, Guangzhou 510301, China.
authors.forename: Zhiyuan
authors.initials: Z
authors.lastname: Wang
authors.forename: Weilin
authors.initials: W
authors.lastname: Huang
authors.forename: Ping'an
authors.initials: P
authors.lastname: Peng
authors.forename: Donna E
authors.initials: DE
authors.lastname: Fennell
mesh_terms: D002384:Catalysis; D004147:Dioxins / Q000737:chemistry; D052918:Environmental Restoration and Remediation; D019015:Geologic Sediments / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000737:chemistry; D013696:Temperature
chemical_list: D004147:Dioxins; D000072317:Polychlorinated Dibenzodioxins; D010165:Palladium; D007501:Iron; C092155:1,2,3,4-tetrachlorodibenzodioxin; C020887:dibenzo(1,4)dioxin