Photocatalytic transformation of the antipsychotic drug risperidone in aqueous media on reduced graphene oxide—TiO2 composites

tIn the present study reduced graphene oxide—TiO2composites were synthesized at two different ratios(1:10 and 1:5) through a hydrothermal method using graphene oxide and commercial P25 as start-ing materials. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-raydiffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET surface area and ultraviolet–visible(UV–vis) absorption spectroscopy were employed to investigate the morphology and properties of theproduced composites. The photocatalytic performance of TiO2–rGO catalysts was evaluated under artifi-cial solar light and visible light in distilled water, as well as, different surface waters (at natural pH) withrespect to risperidone (antipsychotic drug) degradation. Irrespectively of the irradiated aqueous matrix,the photocatalytic efficiency of the tested composite materials under simulated solar light and visiblelight irradiation was higher compared to bare TiO2–P25 (reference catalyst).The identification of intermediate compounds, the assessment of mineralization and the evaluationof toxicity were performed as well. LC/HRMS was brought to bear in assessing the temporal course ofthe photocatalyzed process. Along with risperidone decomposition, the formation of twenty intermediatecompounds (TPs) occurred in the presence of TiO2. Irradiation of risperidone in the presence of the hybridmaterial resulted in the identification of thirty-four TPs. The transformation of risperidone progressedthrough the formation of compounds more harmful than the drug itself, as assessed by the measurementof acute toxicity, evaluated using the Vibrio fischeri bacteria test. When employing TiO2–rGO, all theidentified transformation products were quicker degraded compared to TiO2–P25. At the same time boththe reduction of toxicity and mineralization were faster achieved than with bare TiO2–P25.