Efficient photooxidation processes for the removal of sildenafil from aqueous environments: A comparative study

The erectile dysfunction drug sildenafil has attracted a great deal of attention in recent years due to its widespread legal and illegal use around the world and its increasing use by young people for recreational rather than medical purposes. Due to sildenafil's high stability in various environmental conditions and its accumulation or phototransformation in receiving waters, this dangerous trend poses a significant risk to both human health and the environment. Therefore, in-depth studies are needed to find innovative methods for completely removing sildenafil from the aquatic environment while limiting the formation of more toxic derivatives. This study investigated the efficacy of photooxidation processes for removing sildenafil and its potentially toxic derivatives from water. Distilled water and synthetic wastewater were treated with three different oxidants: peroxymonosulfate (PMS), persulfate (PS) hydrogen peroxide (H2O2), and a heterogeneous catalyst, TiO2. The investigation also considered the formation of potentially toxic phototransformation products, performing a tentative structural identification by LC-ESI-MS and MSn. The results proved that the Sunlight/PMS system is the most effective for entirely and environmentally friendly removal of this drug and its transformation products from aqueous environments, achieving complete degradation in distilled water and synthetic wastewater after 80 and 130 minutes of irradiation, respectively. Toxicity testing with Vibrio fisheri confirmed the non-toxic nature of the phototransformed products. This study highlights the potential of Sunlight/PMS photooxidation as a promising strategy for mitigating the environmental risks associated with sildenafil contamination.