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

Degradation of lindane, a highly persistent and potentially carcinogenic pesticide, by iron (II) activated peroxymonosulfate (Fe2+/HSO5-) was investigated. The efficiency of this process was found to increase with UV light irradiation, probably due to an improved regeneration of Fe2+ for a fast generation of highly reactive (OH)-O-center dot and SO4 center dot-. A greater mineralization and dechlorination efficiency was also observed by UV/Fe2+/HSO5-, 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 Fe2+ (10-1000 mu M) or HSO5- (50-1000 mu M). The initial degradation rate of lindane increased while the observed pseudofirst-order rate constant (k(obs)) decreased with increasing the initial concentration of lindane. Higher pH (>4) resulted in a lower efficiency of UV/Fe2+/HSO5-, attributable to the complexation or precipitation of Fe2+/Fe3+. A Fe2+ level of 50 and 500 mu M showed a comparable effect on lindane mineralization, probably due to the scavenging of SO4 center dot- and (OH)-O-center dot or the faster decomposition of the oxidant by excess Fe2+. Additionally, potential activation of Fe2+/HSO5- by fluorescence light was evaluated. Despite an enhanced degradation of lindane, no significant mineralization of lindane was observed. The results indicate that UV/Fe2+/HSO5- is effective and has a strong application potential for the degradation of lindane and other chlorinated pesticides. (C) 2015 Elsevier B.V. All rights reserved.