In this work photo-electro-Fenton (PEF) processes using a dimensionally stable anode-gas diffusion electrode (DSA-GDE) system under light emission diodes (LED)-type radiation were used in the degradation of the angiotensin-II-receptor antagonists (ARA II), valsartan (VAL), and losartan (LOS), which are used in the treatment of hypertension diseases, and are considered among the emerging contaminants (ECs). Organic acids as citric, tartaric, and oxalic acids were used as complexing agents of iron ions in order to maintain the performance of the Fenton reaction at near-neutral pH value. The results show that at 3.42 mA/cm after 90 min of electro-Fenton (EF) treatment, degradation of 70% of VAL and 100% of LOS were observed. Total degradation of VAL and LOS was reached with a PEF process at the same time with mineralization of 30%. When citric and tartaric acids were used instead of oxalic acid, similar results were obtained, i.e., total degradation of both compounds, LOS and VAL, after 90 min of treatment. The degradation performance can be attributed to the increase of the initial dissolved iron in the system, facilitating the Fe/Fe turnover in the catalytic photo-Fenton reaction and consequently, hydroxyl radical (OH) production. In addition, the increased photo-activity of the complexes can be associated with their high capability to complex Fe and to promote ligand-to-metal charge transfer, which is of key importance to feed Fe to the Fenton process. The results show that the system evaluated was more efficient to eliminate sartan family compounds using LED lighting in comparison with traditional UV-A lamps used in this kind of work. Moreover, three transformation products of VAL degradation and two transformation products of LOS degradation were identified by high-resolution mass spectrometry (HRMS) using hybrid quadrupole-time-of-flight (QTOF) MS and, at the end of the PEF system, the several organic compounds accumulated and no mineralized were effectively treated in a subsequent aerobic biological system.
In this work, the photoelectro-Fenton system was evaluated as an alternative for the degradation of sulfamethoxazole and trimethoprim at unmodi ed 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 e cient degradation of the antibiotics similarly to the e ciency by adding commercial reagent citric acid. The observed high e ciencies 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 e ciently, 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 modi ed 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.
HighlightsSMX and TMP were simultaneously degraded with the PEF process by citric acid addition. E ciency in the degradation was maintained with lemon and orange peels extract.Complete degradation of SMX and TMP increased the biodegradability of the treated solutions.The treated SMX-TMP solutions showed lower ecotoxicity.
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