Heterogeneous Photocatalytic Oxidation and Detoxification of Simulated Agricultural Wastewater Contaminated with Boscalid Fungicide Using g-C3N4 Catalyst

Abstract

In the present study, the photocatalytic oxidation and detoxification of aqueous matrices contaminated with boscalid using g-C3N4 catalyst and UV-A light was investigated. The UV-A/g-C3N4 process was found to achieve higher than 83% removal of boscalid in both matrices, with h+ and O2•− being the main species. UHPLC-HRMS analysis allowed the identification of five TPs, while the main degradation pathways involved hydroxylation, cyclization, and dechlorination. Scenedesmus rubescens microalgae species was exposed to boscalid solutions and lake water spiked with the fungicide before the photocatalytic treatment and inhibition in the growth rate was observed. An increase in the toxicity was also observed during the first stages of the treatment. The results from the in silico study correlate with the observed evolution of ecotoxicity during the application of the process, as some of the identified TPs were found to be toxic or very toxic for aquatic organisms. However, prolonged application of the process can lead to detoxification. It was also observed that the g-C3N4 catalyst can retain its photochemical stability and activity after at least three cycles. However, a slight decrease in the activity was observed when repeated another two times. This study demonstrated that the suggested photocatalytic process can both decrease the harmful effects of boscalid as well as effectively lower its concentration in water.