Sunlight-Driven Degradation of Alprazolam and Amitriptyline by Application of Binary Zinc Oxide and Tin Oxide Powders

Abstract

In recent years, much attention has been paid to pharmaceuticals as potential toxic bioactive substances in the worldwide environment. These compounds are continuously introduced into the surroundings in small concentrations, which certainly affects the quality of water, ecosystem, and the general health of living organisms. Photocatalysis is a promising technique for treating pharmaceutically active compounds as organic pollutants over traditional technologies. This study proposes the application of photocatalysts composed of zinc oxide (ZnO) and tin oxide (SnO2), synthesized using a solid-state method, for the photocatalytic degradation of two selected psychoactive drugs, amitriptyline (AMI) and alprazolam (ALP), under simulated solar and UV irradiation in an aqueous system. The newly synthesized photocatalysts were characterized using the following techniques: SEM/EDS, XRD, DLS, and UV/Vis spectroscopy. The obtained data confirmed the successful synthesis and the possible photocatalytic application of the new materials. Concerning the photocatalytic evaluation, the main results indicate that the highest removal efficiency of AMI and ALP was reached in the presence of ZnO/SnO2 synthesized in a molar ratio of 2:1 and calcined at 700 °C, under 1.0 mg/mL catalyst loading. Based on the reutilization findings, it can be concluded that the mentioned photocatalyst had not lost its efficiency after three successive runs for the photodegradation of ALP. Additionally, pure ZnO powders showed the highest activity after calcination at 500 °C, in the case of both examined pollutants. The experiments with tert-butanol, sodium fluoride, and ethylenediaminetetraacetic acid suggested that the relative contribution of various reactive species changed in the following order: positively charged holes > OHfree• > OHads•.