Degradation of highly chlorinated pesticide, lindane, in water using UV/persulfate: kinetics and mechanism, toxicity evaluation, and synergism by HO.

Sulfate radical-advanced oxidation processes (SR-AOPs) are emerging technologies for decomposing organic pollutants in water. This study investigated the efficiency of UV/persulfate (UV/SO) process to degrade lindane in water, showing 93.2% lindane removal ([lindane] = 3.43 μM, [SO] = 100 μM) at a UV fluence of 720 mJ/cm. The lindane degradation followed first order kinetics and mechanistic studies suggested H-abstraction by SO and Cl removal via C-Cl bond cleavage by UV-C light. Toxicity assessment using ECOSAR program showed toxicity gradually decreased and eventually no significant toxicity remained when all by-products vanished at high UV dose. Removal efficiency of lindane decreased from 93.2% to 38.4, 45.5, 56.0, 84.3 and 88.6%, by adding 1.0 mg/L humic acid or 1.0 mM CO, HCO, Cl or SO, respectively. Coupling of HO with UV/SO showed a significant synergistic effect with 99.0% lindane removal at a UV fluence of 600 mJ/cm, using [SO] = [HO] = 50 μM while UV/HO resulted in only 36.6% lindane removal ([lindane] = 3.43 μM, [HO] = 100 μM) at a UV fluence of 720 mJ/cm. The results indicate that SR-AOP has potential for consideration as a remedial technology to treat persistent chlorinated pesticides such as lindane in contaminated water.