Effectiveness of Advanced Oxidation Processes (AOPs) and adsorption on natural materials for the removal of sildenafil from aqueous phases

Pharmaceuticals represent a large part of the trace organic micropollutants. Most of them reach sewage treatment plants, either metabolised or not. For most of these, occurrence, risk assessment and ecotoxicological data are unavailable. Therefore, it is difficult to predict their health effects on humans and living organisms. In recent years, the widespread use of sildenafil citrate, a drug for erectile dysfunction, has attracted a great deal of attention due to its high use rate, its commercialisation through legal and illegal routes, and its unpredictable use disposal and its potential unknown effects on wildlife and the environment. This study focuses on the removal efficiency of sildenafil by different AOPs and natural adsorption materials. Functionalised bentonite and a local rocky material were tested. Three oxidants were the degradation agents: hydrogen peroxide (H2O2), peroxymonosulfate (PMS) and peroxydisulfate (PS). The degradation processes of sildenafil were studied with particular attention to potentially toxic photo transformation products. They were identified by LC–ESI–MS and confirmed by MS/MS. Subsequently, other experiments assessed the toxicity of sildenafil and its phototransformation products on Daphnia magna and Vibrio fisheri. Results showed that AOPs combined with adsorption on natural materials are essential processes to remove such drugs and their transformation products from aquatic bodies.