Effects and Kinetics of Chlorine Dioxide for Removal of Benzo[a]pyrene in Water

Abstract

Benzo[a]pyrene (BaP) is one of the persistent organic pollutants (POPs) existing widely in the environment and presenting great threats to ecosystems. Chlorine dioxide (ClO2) has been adopted as an effective alternative to chlorine for disinfection in potable water treatment. In this study, a series of experiments were conducted to investigate the feasibility of using ClO2 as an oxidant for BaP degradation. We examined degradation kinetics and effects of ClO2 dosage, reaction time, and pH on the BaP removal by ClO2. Results demonstrated that ClO2 could remove BaP effectively. ClO2 dosage and reaction time were found to have a significant impact on BaP removal, whereas pH only affected slightly in the range of 3.2–9.7. Under optimal reaction conditions, the removal efficiency could reach an extremely high level of 99.8% within 30 min at a ClO2 dosage of 5 mg/L, temperature of 20°C, and pH 7.2 for the BaP samples with initial concentration of 10 μg/L. The reaction between ClO2 and BaP followed a second-order kinetic, and the corresponding rate constant was determined to be 7.795 L/(mol·s). The predominant end products of BaP degradation by ClO2 were characterized as quinine derivatives. This study not only provides a feasible chemical method to efficiently degrade BaP in water treatment, but also suggests a new strategy to promote the development of technologies for POPs reduction in the environment.