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

• Successful synthesis of composites based on reduced graphene oxide and TiO2
• Efficient photocatalytic degradation of risperidone under Vis and UV irradiation
• The transformation of risperidone progressed through the formation of harmful compounds
• With TiO2–rGO reduction of toxicity and mineralization were faster achieved than with bare TiO2

In the present study reduced graphene oxide—TiO2 composites were synthesized at two different ratios (1:10 and 1:5) through a hydrothermal method using graphene oxide and commercial P25 as starting materials. Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray diffraction (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 the produced composites. The photocatalytic performance of TiO2–rGO catalysts was evaluated under artificial solar light and visible light in distilled water, as well as, different surface waters (at natural pH) with respect to risperidone (antipsychotic drug) degradation. Irrespectively of the irradiated aqueous matrix, the photocatalytic efficiency of the tested composite materials under simulated solar light and visible light irradiation was higher compared to bare TiO2–P25 (reference catalyst).The identification of intermediate compounds, the assessment of mineralization and the evaluation of toxicity were performed as well. LC/HRMS was brought to bear in assessing the temporal course of the photocatalyzed process. Along with risperidone decomposition, the formation of twenty intermediate compounds (TPs) occurred in the presence of TiO2. Irradiation of risperidone in the presence of the hybrid material resulted in the identification of thirty-four TPs. The transformation of risperidone progressed through the formation of compounds more harmful than the drug itself, as assessed by the measurement of acute toxicity, evaluated using the Vibrio fischeri bacteria test. When employing TiO2–rGO, all the identified transformation products were quicker degraded compared to TiO2–P25. At the same time both the reduction of toxicity and mineralization were faster achieved than with bare TiO2–P25.

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