Influence of ZnO content in mixed oxides catalysts applied in the photocatalytic degradation of atrazine

Abstract

Atrazine (2-chloro-4-ethylamino-6-isopropylamino-s-triazine) is an herbicide widely used in agricultural crops and has aroused worldwide concern for high potential pollution in soil, sediments, water and food. As the conventional methods for the persistent degradation of organic compounds are not very efficient, new technologies have been developed to remove those, especially those that use advanced oxidation processes (AOPs) and between AOPs, there is a heterogeneous photocatalysis. In this sense, the use of photocatalysts for water decontamination with organic materials is shown as an efficient alternative due to its oxidative properties.The photocatalytic process involves the activation by sunlight or artificial light of a semiconductor material, resulting in total or partial mineralization of these contaminants. This study aims to evaluate the performance of the mixed oxide catalysts (ZnO/TiO2), with different ZnO contents (5, 8, 10, and 15 wt. %) in the photocatalytic degradation of atrazine in aqueous phase using UV radiation. The catalysts were prepared by wet impregnation and characterized by specific surface area (BET method), pore diameter and pore volume, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The photocatalytic reactions were conducted in a batch-type reactor and the reaction products were analyzed by high-performance liquid chromatography (HPLC) and UV-Vis spectrophotometry at a wavelength of 221nm in order to evaluate the behavior of atrazine throughout the reaction. The results showed that catalysts containing 5%ZnO/TiO2 and 10%ZnO/TiO2 were the most efficient presenting a complete degradation of atrazine and a partial mineralization of the products. The degradation of atrazine after 10 minutes of reaction was 97.5 wt.% for the 5%ZnO/TiO2 catalyst and 94 wt.% for the 10%ZnO/TiO2 catalyst.