Degradação de oxibenzona por processos oxidativos avançados

Abstract

Oxybenzone (BP-3) is an ultraviolet (UV) filter widely used in sunscreens and cosmetic products. Its occurrence in aquatic environments has raised increasing concern due to its persistence in the environment and its potential toxic effects on aquatic organisms. In this context, Advanced Oxidation Processes (AOPs) have emerged as a promising alternative for the removal of this contaminant. Therefore, this study aimed to evaluate the degradation of oxybenzone using the persulfate/UV (K2S2O8/UV) system by investigating the influence of the initial contaminant concentration, the BP-3:K2S2O8 molar ratio, and the solution pH, as well as assessing the performance of the degradation process in a real water matrix. The experiments were carried out in a photochemical reactor under UV-C irradiation, and the degradation was monitored by UV-Vis spectrophotometry. Initially, BP-3 solutions with concentrations ranging from 1 to 5 mg L−1 were evaluated, and the concentration of 4 mg L−1 was selected because it provided an adequate analytical response and enabled the monitoring of BP-3 degradation throughout the entire reaction period. The experimental conditions that resulted in the highest BP-3 degradation in deionized water were a BP-3:K2S2O8 molar ratio of 1:800 and the degradation process carried out at the natural pH of the solution (≈ 5.6), achieving approximately 75.0% degradation after 120 minutes of reaction. The kinetic data showed an excellent fit to the pseudo-first-order model (R2 = 0.9893), resulting in an apparent rate constant of 0.0116 min−1 and a half-life of 59.6 minutes. When the same experimental conditions were applied to a BP-3 solution prepared with raw water, the degradation efficiency decreased to 69.5%, with an apparent rate constant of 0.00872 min−1 and a half-life of 79.4 minutes, indicating that naturally occurring constituents in the water matrix reduced the reaction rate and the availability of reactive oxidizing species without significantly compromising the degradation efficiency. These results demonstrate that the K2S2O8/UV system has significant potential for the degradation of oxybenzone in aqueous matrices, representing a promising alternative for the treatment of emerging contaminants.