title: Rapid dechlorination of polychlorinated dibenzo-p-dioxins by bimetallic and nanosized zerovalent iron.
abstract: Polychlorinated dibenzo-p-dioxins and furans (PCDD/Fs), especially the 2,3,7,8-substituted congeners, are extremely toxic, persistent, and recalcitrant to remediation. Dechlorination of PCDD/Fs by zerovalent iron (ZVI) is thermodynamically feasible, but useful rates of reaction have not been previously reported. Here we show that ZVI (both micro- and nanosized ZVI, without palladization) dechlorinates PCDD congeners with four or more chlorines in aqueous systems, but the reaction is too slow to achieve complete dechlorination within a practical period of time. In contrast, palladized nanosized ZVI (Pd/nFe) rapidly dechlorinates PCDDs, including the mono- to tetra-chlorinated congeners. The rate of 1,2,3,4-tetrachloro dibenzo-p-dioxin (1,2,3,4-TeCDD) degradation using Pd/nFe was about 3 orders of magnitude faster than 1,23,4-TeCDD degradation using unpalladized ZVI. The distribution of products obtained from dechlorination of 1,2,3,4-TeCDD suggests that palladization shifts the pathways of contaminant degradation toward a greater role of H atom transfer rather than electron transfer.
authors.affiliation: School of Environmental Science and Engineering, Pohang University of Science and Technology (POSTECH), Pohang, 790-784, South Korea.
authors.forename: Ji-Hun
authors.initials: JH
authors.lastname: Kim
authors.forename: Paul G
authors.initials: PG
authors.lastname: Tratnyek
authors.forename: Yoon-Seok
authors.initials: YS
authors.lastname: Chang
mesh_terms: D002713:Chlorine / Q000737:chemistry; D004785:Environmental Pollutants / Q000737:chemistry*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007501:Iron / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry*; D000072317:Polychlorinated Dibenzodioxins / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D004785:Environmental Pollutants; D000072317:Polychlorinated Dibenzodioxins; D002713:Chlorine; D007501:Iron