Nanofotocatalisadores de ZnO dopados com cério para tratamento de efluentes da indústria têxtil pernambucana

Abstract

The state of Pernambuco has one of the largest textile centers in Brazil, and as the entire textile industry uses a large volume of water in the dyeing and finishing stages, the laundries and the textile sector have greatest potential for contamination of effluents due to the amount of organic matter generated, creating various environmental and social problems. In recent decades, photocatalytic processes have stood out as an alternative for the treatment of effluents with high organic load, using semiconductors as photocatalysts, in particular zinc oxide (ZnO). In this sense, the objective of this dissertation was to synthesize Zn(1-x)CexO nanoparticles with x= 0, 0.005, 0.01, 0.02, 0.03, 0.04 and 0.05, by the microwave-assisted hydrothermal method and evaluate their efficiency as photocatalysts. Synthesis was performed at 120°C for a time of 32 minutes in alkaline NaOH 3M solution. The samples were obtained in powder form and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Visible spectroscopy (UV-VIS) measurements. SEM images showed that the particles are constituted by nanoplates with average thickness between 41 and 87 nm, and width between 329 and 741 nm, forming a three-dimensional cluster with a perimeter between 11 and 46 μm. XRD technique showed that all samples have a hexagonal wurtzite type crystalline structure of ZnO. For samples with Ce content greater than 1%, peaks referring to the cubic phase of CeO2 were identified. UV-VIS spectra showed a reduction in the optical band gap of the samples with the increase in cerium content. In the photocatalytic tests all synthesized samples were able to fully degrade the methylene blue dye after 30 min. An increase in photocatalytic efficiency was verified with increasing Ce content up to 1%, due to the creation of intermediate states in the band gap optimizing the removal power of the photocatalyst.