Effects and kinetics of chlorine dioxide for removal of Benzo[a]pyrene in water

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 (ClO ₂) 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 ClO ₂ as an oxidant for BaP degradation. We examined degradation kinetics and effects of ClO ₂ dosage, reaction time, and pH on the BaP removal by ClO ₂. Results demonstrated that ClO ₂ could remove BaP effectively. ClO ₂ 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 ClO ₂ 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 ClO ₂ 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 ClO ₂ 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.