Rapid Dechlorination of Pentachlorophenol by Zero-valent Zinc Metal
Abstract:New interest in the reactions of reducing metals has been created by contemporary concerns with environmental protection. Iron is widely used to dechlorinate chlorinated organic compounds. However, iron may result in passivation of the metals or affect the reactivities of metal surfaces through fouling. Thus, another candidate of reducing metal, zinc, was chosen to investigate the ability of dechlorination in our study. Dechlorination of chlorinated phenol (CPs) occurred in corrosion phase of zinc under anaerobic conditions, and decreasing pH increased the reduction rate obviously. Pentachlorophenol (PCP) degradation in acid solution quickly occurred in several hours, but the stepwise dechlorination substantially became slower. The predominant products were 2,3,4,6-tetrachlorophenol (2,3,4,6-TeCP), 2,3,5,6-tetrachlorophenol (2,3,5,6-TeCP), 2,3,6-trichlorophenol (2,3,6-TCP), 2,4,6-trichlorophenol (2,4,6-TCP). From the pseudo-first-order rate constants for CPs reactions show the dechlorination rates by zinc were directly proportional to the degree of chlorination. Dechlorination of CPs under passive phase of zinc was not observed. It shows a passivating film of Zn(OH)2, which acts as a kinetic barrier to prevent reductive dechlorination of CPs.
Document Type: Research Article
Publication date: 2000-01-01
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