Obtenção de ZnO na forma de peças para aplicação em fotocatálise

Abstract

Photocatalysis is a promising alternative to decontamination of wastewater containing dyes. However, efforts are necessary in direction of catalyst immobilization that allow its removal from the media and reuse. ZnO based photocatalysts were obtained by pressing (by applying different pressures) and slip casting (by using different deflocculant concentration), with heat treatment at 800 °C. The obtained samples were characterized by apparent porosity, apparent density, x-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The physical and structural properties of the samples are directly correlated with the conformation method. The samples photocatalytic performance were attested by the photocalytic degradation of 5 to 50 mg/L Rhodamine B (RB) solution under UVC radiation. The samples obtained by slip casting showed reaction rate constant between 1,68x10-2 min-1 and 1,87x10-2 min-1, while the pressed samples showed reaction rate constant between 9,9x10-3 min-1 and 1,16x10-2 min-1. Thus, the samples obtained by slip casting showed better photocatalytic performance in relation to the pressed samples, which can be justified by the difference of apparent porosity between them. By means of undergoing multiple degradation cycles it could be verified that the samples obtained by slip casting show stability in regards of photocatalytic performance, while the pressed samples had a performance decrease after the third cycle. By varying the dye concentration, it was observed that the produced samples showed loss in discoloration efficiency with initial dye concentration increase, although the amount of degraded dye increased with initial dye concentration increase until the optimal concentration of 40 mg/L for pressed samples and 30 mg/L for samples obtained by slip casting.