Degradation of benzimidazoles by photoperoxidation: metabolites detection and ecotoxicity assessment using Raphidocelis subcapitata microalgae and Vibrio fischeri

Benzimidazoles (BZ) are among the most used drugs to treat parasitic diseases in both human and veterinary medicine. In this study, solutions fortified with albendazole (ABZ), fenbendazole (FBZ), and thiabendazole (TBZ) were subjected to photoperoxidation (UV/H2O2). The hydroxyl radicals generated by the process removed up to 99% of ABZ, and FBZ, in the highest dosage of H2O2 (i.e., 1.125 mmol L-1; 4.8 kJ L-1). In contrast, 20% of initial TBZ concentration remained in the residual solution. In the first 5 min of reaction (i.e., up to 0.750 mmol L-1 of H2O2), formation of the primary metabolites of ABZ-ricobendazole (RBZ), albendazole sulfone (ABZ-SO2), and oxfendazole (OFZ)-was observed. However, these reaction products were converted after the reaction time was doubled. The residual ecotoxicity was investigated using the Raphidocelis subcapitata microalgae and the marine bacteria Vibrio fischeri. The results for both microorganisms evidence that the residual solutions are less harmful to these microorganisms. However, after 30 min of reaction, the treated solution still presents a toxic effect for V. fischeri, meaning that longer reaction times are required to achieve an innocuous effluent. (AU)