Gamma radiolytic decomposition of endosulfan in aerated solution: the role of carbonate radical

The present study elaborates the removal of endosulfan, an emerging water pollutant and potential carcinogenic, in aerated solution. The influence of Cl⁻, NO₃ ⁻, NO₂ ⁻, CO₃ ²⁻, HCO₃ ⁻, SO₃ ²⁻, and humic acid was assessed on the radiolytic degradation of endosulfan. A strong inhibition on the radiolytic degradation of endosulfan was observed in the presence of NO₃ ⁻, NO₂ ⁻, and SO₃ ²⁻. Instead, a slight increase in the removal efficiency of endosulfan was observed at high concentrations of CO₃ ²⁻ and HCO₃ ⁻. The formation of CO₃ ^•− in radiolytic degradation of endosulfan in the presence of CO₃ ²⁻ and HCO₃ ⁻ was demonstrated by adding SO₃ ²⁻ that rapidly react with CO₃ ^•−. The results indicate that CO₃ ^•− formed from the reactions of CO₃ ²⁻ and HCO₃ ⁻ and commonly found in natural water can play an important role in the degradation of endosulfan and other sulfur containing electron-rich compounds. The study showed faster degradation of endosulfan at lower concentration compared to high concentration and removal was found to follow pseudo-first-order kinetic. Endosulfan ether was found as the main degradation product and degradation pathway was found to be initiated at the S=O bond of endosulfan. The efficiency of gamma irradiation in the removal of endosulfan was examined in terms of formation of short chain organic acids and chloride ion accumulation.