Obtenção de catalisadores heterogêneos ZnO:Si para aplicação na degradação do pesticida Aldrin

Abstract

In an agriculture-centered economy, pesticides are widely used, making the removal of these compounds from the environment an essential prerequisite due to their toxic nature and chemical biological stability. For instance is Aldrin, a persistent organic pollutant that is bioaccumulative, photosensitive to artificial light, and highly toxic. According to the literature, treatments for contaminated effluents can occur by physical, biological, or chemical processes. In this context, heterogeneous photocatalysis has emerged as an efficient chemical process using simple and mixed oxide semiconductors. The present study aimed to prepare binary oxides based on Zn1-xSixO (x=0.10, 0.20, and 0.30) by the polymeric precursor method for application in the photocatalytic degradation of the pesticide Aldrin. The materials were characterized by X-ray Diffraction (XRD), Infrared Spectroscopy (IR), UV-Visible Absorption Spectroscopy, RAMAN Spectroscopy, Scanning Electron Microscopy (SEM), surface area measurement by nitrogen adsorption using the BrunauerEmmett-Teller method (BET) and zeta potential to determine the charge(ZCP). The mixed metal oxides were successfully obtained, as confirmed by XRD patterns and ICDD data for ZnO and SiO2. The calculated band gap values of the materials from the UV-vis absorption spectra ranged from 2.88 eV to 2.92 eV, favoring excitation energy with UVC lamp (4.9 eV). Regarding the photocatalytic tests for Aldrin degradation, all three compositions showed degradation response, with the sample with the lowest Si content exhibiting the best performance (40%) at a slightly acidic pH of 5.7 compared to the other samples. On the other hand, at a basic pH of 10.2, the Zn0.80Si0.20O and Zn0.70Si0.30O samples showed 92% and 96% degradation, respectively, in a reaction time of 4 hours. The Zn0.70Si0.30O sample stood out, showing 94% degradation of Aldrin in a 2-hour reaction. Additionally, ZCP studies were crucial in evaluating the surface charges and material behavior concerning pH and their interactions with the polluted solution medium.