Reactivity and reaction mechanisms of sulfate radicals with lindane: An experimental and theoretical study

Abstract

Advanced oxidation technologies (AOTs) have been intensely used to eliminate various organic pollutants in engineering waters. In this context, we investigated the kinetics and mechanisms of the sulfate radical (SO4-)−mediated degradation of lindane in UV/peroxydisulfate system, and compared results with previous studies on SO4-–based AOTs for destruction of lindane. The second order rate constant (k) value between SO4- and lindane was determined to be (8.95 ± 0.29) × 106 M−1 s−1via competition kinetics using p–cyanobenzoic acid as reference compound, which is close to the theoretically calculated value of 4.41 × 107 M−1 s−1, that was performed at SMD/M05−2X/6–311++G**//M05−2X/6–31+G** level of theory using density functional theory (DFT) approach. H−atom abstraction pathway was calculated to be thermodynamically favorable and kinetically dominant. In the combined experimental and theoretical study, we aim for a better understanding on the degradation kinetics and mechanisms of lindane, serving as a starting point for more attention to SO4-−mediated degradation kinetics of cycloaliphatic compounds in future.