Caracterização e avaliação do catalisador ZnO/CuO na degradação do azul de metileno utilizando a fotocatálise solar

• Autor(a) principal: Cahino, Arthur Marinho
• Data de Publicação: 2019
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFPB
• Texto Completo: https://repositorio.ufpb.br/jspui/handle/123456789/16977
• topic: Fotocatálise solar; Método Pechini; Óxidos inorgânicos; Semicondutores acoplados; Solar photocatalysis; Pechini method; Inorganic oxides; Coupled semiconductors; Fotocatálise; CNPQ::ENGENHARIAS

Advanced oxidative processes (AOPs) stand out as an alternative to the treatment of industrial effluents due to their efficient removal of pollutants with high chemical stability and low biodegradability. Among the AOPs, solar photocatalysis encompasses the set of chemical reactions that occur in the presence of solar radiation and are capable of degrading a wide range of pollutants through the generation of highly reactive hydroxyl radicals. In this regard, catalysts based on the combination of zinc oxide and copper oxide were synthesized in the 80:20 mass ratio by the Pechini method and tested for dye removal by means of heterogeneous catalysis combined with solar radiation, using methylene blue as model effluent. The catalysts samples were characterized using X-ray diffraction (XRD), X-ray fluorescence (XRF), textural analysis by absorption and desorption of liquid nitrogen by the BET/JBH method, infrared spectroscopy (FTIR), UV-Vis absorption spectroscopy for the band gap calculation and scanning electron microscopy (SEM). Experimental planning was carried out in order to define the best conditions for kinetic studies. Finally, the reuse of the catalyst was tested using the best condition found in the experimental designs. The total mass loss was 50%, which stabilized after the temperature of 550 °C. The average crystallite size obtained was 26.21; 28.21 and 35.91 nm for the calcined samples, respectively. The FRX was effective in determining the elements present in the catalyst, consisting of 75% zinc oxide and 25% copper oxide. The values of surface area were of 7.54; 7.19 and 3.92 m2/g, respectively. Infrared spectroscopy identified transmittance peaks in the range of 460 cm-1 corresponding to the Zn-O and Cu-O bonding bands. The values of band gaps found allowed to conclude that the catalysts are in the ultraviolet range, but that also occurs the activation of the catalyst in the visible range. The micrographs allow to conclude that as the calcination temperature increases, the particles become more agglomerated, interfering in the photocatalysis. The experimental design was important to define the best study condition: calcination temperature of 500 ºC, 20 mg/L of methylene blue, 30 mg/L of H2O2 and pH 6. The degradation kinetics proved the process efficiency with H2O2 addition (removal of 92% after 300 minutes), but mainly demonstrated the effectiveness of photocatalysis performance (removal of 76% after 300 minutes). Comparative studies were performed between the mixed catalyst and the pure ZnO and CuO catalysts, synthesized by the Pechini method, and it was verified that the pure oxides do not have degradation efficiency similar to the mixed oxide. The catalyst was reused and, after four cycles, it was found that the mixed catalyst was not affected. The results allow to propose that there is viability in the application of solar photocatalysis in the treatment of methylene blue with ZnO/CuO.