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 and SO₄^-. 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 μM) or HSO₅^- (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/Fe²⁺/HSO₅^-, attributable to the complexation or precipitation of Fe²⁺/Fe³⁺. A Fe²⁺ level of 50 and 500 μM showed a comparable effect on lindane mineralization, probably due to the scavenging of SO₄^- and OH 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.