Synthesis of ZnO nanostructures using sublimation–condensation and sol-gel methods: Evaluation of the photocatalytic degradation activity of industrial dye

Abstract

ZnO nanostructures were prepared by sublimation–condensation (ZnO-SPVD) technique and sol-gel method (ZnO-SG). The produced materials were used in a photocatalytic degradation of a pollutant (gentian violet) at different operational conditions. The materials were characterized by X-ray diffraction (XRD) and Raman spectra techniques (RS). The obtained results indicated that the photocatalytic activity was correlated to the particle sizes of catalysts. The catalyst prepared by the physical method (ZnO-SPVD) exhibited a higher photoactivity to degrade GV dye than the catalyst prepared by the chemical method (ZnO-SG). In the presence of each of ZnO-SPVD or ZnO-SG, the experiments were carried out to investigate the factors that influence the photocatalytic degradation of GV, such as the adsorption amount, pH of dye solution, electron acceptors (H2O2), and presence of inorganic species commonly present in real wastewaters (HCO−3 ). The experimental results showed that adsorption on the surface of both samples was an important parameter controlling the photocatalytic activity. For both catalysts, the degradation rate in alkaline medium was higher than that in natural and acidic one. The presence of the H2O2 and HCO−3 ions increased the effectiveness of the photodegradation.