Processo de fotocatálise solar para remoção do azul de metileno assistido por ZnO/CuO

Abstract

Environmental concern regarding water pollution is of utmost relevance. The textile sector, since the Industrial Revolution, has been degrading aquatic biota with its improper discharge of toxic elements in effluents. Nowadays, conventional processes for dye remediation exist; however, they are not efficient, as they tend to only minimize the toxicity of the dyes, changing the phase of the element without fully demineralizing it, in addition to having high costs. Therefore, one of the alternatives for solving this problem is to use advanced oxidative processes, particularly the discoloration process via solar photocatalysis, assisted by semiconductors such as zinc and copper oxides, which utilize solar energy to degrade improperly discharged dyes. The objective of this work was to use copper and zinc oxides and their heterojunctions in the photocatalytic degradation of methylene blue dye, using solar energy. In this research, the photocatalysts were obtained by the hydrothermal method and were tested in their pure form and in the proportions of 80%ZnO/20%CuO and 20%ZnO/80%CuO. The oxides were characterized by X-ray diffraction, infrared absorption spectrum with Fourier transform, scanning electron microscopy, ultraviolet and visible absorption spectrum, and Brunauer-Emmett-Teller surface area analysis. According to the presented bandgaps, the materials possess photocatalytic properties in the ultraviolet and visible regions. The best efficiencies found were for the 80%ZnO/20%CuO and pure ZnO, across all pH ranges, resulting in 100% decontamination using ultraviolet radiation. In an open environment using solar radiation, the best efficiencies were found for the 80%ZnO/20%CuO at pH 5.7 and unchanged, along with pure ZnO at pH 9, resulting in 100% discoloration. The results demonstrate that the materials are promising for the remediation of methylene blue dye, and this research contributes to the Sustainable Development Goals (SDGs) in terms of ensuring environmental sustainability, improving water treatment (SDG 6), developing advanced technologies (SDG 9), harnessing solar energy (SDG 13), and preserving biodiversity (SDG 15).