Enhanced degradation of the UV filter phenylbenzimidazole sulfonic acid in water via UV-activated percarbonate

Abstract

The emergence of UV filters in aquatic environments is a significant environmental concern because of their persistent nature and potential toxicity to ecosystems. However, an efficient treatment for eliminating UV filters from water has yet to be discovered. In this study, a UV-activated sodium percarbonate (UV/SPC) process was explored for the degradation of a commonly used UV filter: phenylbenzimidazole sulfonic acid (PBSA). Owing to the synergistic effect in the UV/SPC process, PBSA was completely removed from the water within 15 minutes. On the basis of the results from the EPR and probe experiments, the reactive species •OH, CO₃•^–, O₂•^–, and ¹O₂ were involved in PBSA degradation. During the UV/SPC reaction, PBSA underwent several main pathways, including i) hydroxylation, ii) oxidation, iii) imidazoline ring cleavage, iv) desulfonation, and v) benzene ring cleavage, further transforming into byproducts. Moreover, no obvious Microtox® toxicity was observed after UV/SPC treatment. The crucial parameters that affected PBSA degradation were the solution pH, SPC concentration and initial PBSA concentration. In addition, the pseudo-first-order rate constant (k_obs) decreased as the pH and PBSA concentration increased, whereas it increased with increasing SPC concentration. Additionally, in real water systems, PBSA was completely removed within 50 minutes by UV/SPC. In this work, comprehensive data on the mechanism of PBSA degradation and a promising treatment method for removing PBSA from water were provided.