Oxidative paraben removal with chlorine dioxide: Reaction kinetics and mechanism

Abstract

This study investigated the reactivity and mechanism of paraben oxidization by chlorine dioxide. Degradation kinetics of methylparaben (MeP) and propylparaben (PrP) followed pseudo-first-order kinetics, and were studied in a pH range of 4.0–7.0 at 15 ± 1 °C. The kapp values were 84.3 M−1·s−1 and 83.2 M−1·s−1 for MeP and PrP, respectively, when pH value was 5.0 and the temperature was 15 ± 1 °C. The rate constants depended on the solution pH, temperature, humic acid, and HCO3– concentrations. At pH values of 4–5.0, kapp increased slowly, while at a pH value of 7.0, kapp increased rapidly. The reaction rate constants increased with increasing temperature. Furthermore, the reaction rate was inhibited by humic acid addition, while the reaction rate increased after addition of HCO3–. Two main degradation products were identified by GC–MS and the reaction pathways were proposed.