Synergistic effects of HSO₅ ⁻ in the gamma radiation driven process for the removal of chlorendic acid: A new alternative for water treatment

Removal of chlorendic acid, an emerging water pollutant and potential carcinogenic, was investigated by gamma radiation in the absence and presence of peroxymonosulfate (PMS, HSO₅ ⁻). The removal of chlorendic acid (1.40 μM initial concentration) by gamma radiation was promoted with PMS, i.e., 95% compared to 82% in the absence of PMS, at an absorbed dose of 1000 Gy. The removal of chlorendic acid by gamma-ray/PMS process was due to ^[rad]OH and SO₄ ^[rad]−. Second-order rate constants of 5.90 × 10⁹, 1.75 × 10⁹, and 2.05 × 10⁹ M⁻¹ s⁻¹ for chlorendic acid with e_aq ⁻, ^[rad]OH, and SO₄ ^[rad]−, respectively, were determined. The removal efficiency of chlorendic acid was promoted with increasing initial PMS concentration and decreasing initial target contaminant concentration. The removal of chlorendic acid by gamma-ray/PMS was inhibited in the presence of CO₃ ²⁻, NO₂ ⁻, p-CBA, m-TA, and alcohols. The presence of Fe²⁺, Cu⁺, and Fe³⁺ with gamma-ray/PMS promoted removal efficiency of chlorendic acid from 78% to 99, 94, and 89%, respectively, at 592 Gy. The degradation of chlorendic acid by ^[rad]OH and SO₄ ^[rad]− was found to be initiated at the carboxylate group as could be revealed from nature of the transformation by-products. Nevertheless, this study concluded that gamma-ray/PMS is of practical importance in treatment of natural water containing chlorendic acid, as potential detoxification of chlorendic acid solution can be revealed from 83% loss of chloride ion at 3000 Gy. In addition, gamma-ray/PMS process achieved efficient removal of chlorendic acid even in the presence of commonly found inorganic ions in natural water.