Adsorption and photodegradation as processes enabling the removal of antiviral drug ritonavir from the aquatic environment

The presence of antiviral drugs in the aquatic environment raises serious concerns due to the potential risk associated with their biological activity and potential metabolites, which themselves may have negative interactions with living organisms.This study systematically explores the removal of the antiviral drug ritonavir (RTR) using a photochemically induced advanced oxidation process.In this work, solar light-driven photolysis, homogeneous photocatalysis induced by sunlight in the presence of HO, and photocatalysis in the presence of TiO were tested.Under solar light irradiance (500 W/m), the removal of ritonavir is limited to 15% in Milli-Q (MQ) water and 38% in tap water (TW), with corresponding rate constants (k) of 0.0009 min and 0.0026 min, respectively.The influence of HO was further examined and showed that exposure to artificial light (500 W/m) resulted in the concentration of RTR in MQ water dropping below the limit of detection (LOD) at doses of 125.0, 250.0, and 500.0L, achieving complete degradation at 100%.The highest pseudo degradation rate was observed at a 500 L HO dose (k = 0.1439), with an R value of 0.9844.Additionally, the photocatalytic activity of pure TiO (10.0 mg/L) on ritonavir in MQ water was investigated under dark conditions and solar light.The results demonstrated immediate and complete adsorption of RTR, reaching 100% on the TiO surface, with an adsorption capacity of 3.9952 mg/g.It is assumed that photochemical degradation of the antiviral drug was minimal in TiO, but the adsorption process on the photocatalyst surface dominated.Hence, the kinetic parameters of this process were calculated.Under solar light, the TiO surface retained 72% of the RTR, with a maximum adsorption capacity (qmax) of 3.7580 mg/g, suggesting cyclical sorption and desorption processes occurred until an equilibrium state was established.These findings highlight the efficacy of this method in addressing the issue of antiviral drug residues in an aqueous environment but also indicate that the heterogeneous photocatalysis process may not always be feasible, especially in cases where there is a high affinity of a given substance for sorption on the photocatalyst surface.However, the drug itself is susceptible to decomposition when the source of hydroxyl radicals is HO.