An Efficient Simultaneous Degradation of Sulfamethoxazole and Trimethoprim by Photoelectro-Fenton Process Under Non-Modified pH Using a Natural Citric Acid Source: Study of Biodegradability, Ecotoxicity and Antibacterial Activity

Abstract In this work, the photoelectro-Fenton system was evaluated as an alternative for the degradation of sulfamethoxazole and trimethoprim at unmodified pH by using citric acid present in extracts from a natural source as organic residues (orange and lemon peels). The addition of natural citric acid showed an efficient degradation of the antibiotics similarly to the efficiency by adding commercial reagent citric acid. The observed high efficiencies and rate constants are attributed to the increment of ferrous ion in the solution due to the fast conversion of iron form its ferric to ferrous state leading to the Fenton reaction and so increasing the hydroxyl radicals production. Although the addition of citric acid present in the extracts slightly increases the organic matter of the solutions, the degradation of the antibiotics was achieved simultaneously and efficiently, converting the photoelectro-Fenton process with the addition of natural citric acid into an alternative ecological system and sustainable for water contaminated with pharmaceutics. Additionally, the high biodegradable character and low ecotoxicity of the treated solutions were determined by a modified Zahn Wellens test and a bioassay with D. magna, respectively. Finally, simultaneous degradation of sulfamethoxazole and trimethoprim was reached after only 45 min of treatment in which the antibacterial activity was completely eliminated, suggesting that degradation products do not represent any environmental risk nor human health.