UV-activated peroxymonosulfate for haloacetamides degradation: Kinetics and reaction pathways

Abstract

Haloacetamides (HAcAms) is ubiquitously found in drinking water, which exhibits strong cytotoxicity and genotoxicity compared with conventional disinfection byproducts (DBPs). Herein, the degradation of HAcAms containing dichloroacetamide (DCAcAm) and trichloroacetamide (TCAcAm) by UV/peroxymonosulfate (PMS) process was studied. Degradation kinetics of DCAcAm and TCAcAm conformed to the first-order model, and the corresponding reaction constants were 2.27 × 10⁻³ and 1.94 × 10⁻³ s⁻¹, respectively. The degradation rate raised with the increment of PMS dosage. During the investigation of water matrices including Cl^–, HCO₃^–, and humic acid (HA), HCO₃^– and HA inhibited the degradation process whereas the influence of Cl^– on the degradation was negligible. As evidenced by trapping test, •OH played the crucial role in the degradation of HAcAms. During the UV/PMS process, dechlorination was the main process. TCAcAm could be oxidized to DCAcAm and acetamide, and further mineralized to Cl^–, CO₂, H₂O, NO₂^–, and NO₃^–. Our results demonstrated that UV/PMS could be an effective technique to degrade HAcAms in dinking water.