Photocatalytic degradation of methyl green dye in aqueous solution over natural clay-supported ZnO-TiO2 catalysts

A ZnO-TiO2/clay photcatalyst was prepared using a natural Tunisian clay as support. Its activity was assayed in the photocatalytic degradation of methyl green in aqueous solutions, in the presence of UVA irradiation. The photocatalyst was synthesized using a metal organic chemical vapor deposition (MOCVD) with Ti (OPri)4 deposed on the natural Na+-clay, followed by a modified sol-gel synthesis method for introduction. The sample was then characterized by scanning electronic microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), N2 adsorption, X-ray diffraction (XRD) and titration for the determination of the zero point charge (pHZPC). The activity tests showed that the photodegradation efficiency for ZnO-TiO2/clay is higher than for the TiO2/clay catalyst, clearly pointing to a promoting effect of ZnO. The influence of operational parameters such as pH, catalyst dosage, initial dye concentration, UV irradiation intensity, as well as the influence of the presence of different oxidants was evaluated. Almost complete mineralization was obtained upon 30 min of light irradiation in the presence of the ZnO-TiO2/clay catalyst.