Degradation of emerging pollutants in water under solar irradiation using novel TiO2-ZnO/clay nanoarchitectures

Emerging water pollutants, such as pharmaceuticals, are currently under study due to the increasing concern on the risks they pose on humans and the environment. Herein, solar photocatalytic technology is used for the degradation of model pharmaceuticals, including acetaminophen (ACE) and antipyrine (ANT), with novel TiO2-ZnO/clay nanoarchitectures. These photocatalysts are based on the heterojunction between TiO2-ZnO semiconductors and a delaminated layered clay. The structural, electronic and textural features of the photocatalysts were characterized by different techniques. The degradation rate has been checked under different conditions, including target compound and catalyst concentrations, intensity of the solar light and the combination of pharmaceuticals. ANT showed a higher degradation rate than ACE and in both cases the degradation was favored at low concentrations. The disappearance of both compounds was well described by a simple pseudo-first-order rate equation. Although both target compounds were almost completely removed, some TOC was still remaining corresponding to short-chain carboxylic acids and unidentified by-products with very low significance in terms of ecotoxicity. Scavengers were used to learn on the radical mechanism of the reaction and different behavior was observed for each target compound. The results of this study prove the ability and stability after several operation cycles of these novel photocatalysts to promote the degradation of these pollutants under solar light irradiation. (C) 2016 Elsevier B.V. All rights reserved.