Efficient degradation of lindane in aqueous solution by iron (II) and/or UV activated peroxymonosulfate

Abstract

Abstract Degradation of lindane, a highly persistent and potentially carcinogenic pesticide, by iron (II) activated peroxymonosulfate (Fe 2+ /HSO 5 − ) was investigated. The efficiency of this process was found to increase with UV light irradiation, probably due to an improved regeneration of Fe 2+ for a fast generation of highly reactive OH and SO 4 − . A greater mineralization and dechlorination efficiency was also observed by UV/Fe 2+ /HSO 5 − , with a 92.2% total organic carbon removal and 96.4% chloride ion release after 180 min UV illumination. Removal of lindane by such a photochemical process was further promoted with increasing the initial concentration of either Fe 2+ (10–1000 μM) or HSO 5 − (50–1000 μM). The initial degradation rate of lindane increased while the observed pseudo first - order rate constant ( k obs ) decreased with increasing the initial concentration of lindane. Higher pH (>4) resulted in a lower efficiency of UV/Fe 2+ /HSO 5 − , attributable to the complexation or precipitation of Fe 2+ /Fe 3+ . A Fe 2+ level of 50 and 500 μM showed a comparable effect on lindane mineralization, probably due to the scavenging of SO 4 − and OH or the faster decomposition of the oxidant by excess Fe 2+ . Additionally, potential activation of Fe 2+ /HSO 5 − by fluorescence light was evaluated. Despite an enhanced degradation of lindane, no significant mineralization of lindane was observed. The results indicate that UV/Fe 2+ /HSO 5 − is effective and has a strong application potential for the degradation of lindane and other chlorinated pesticides.