Influence of the preparation method and ZnO/(ZnO + TiO2) weight ratio on the physicochemical and photocatalytic properties of ZnO-TiO2 nanomaterials

In this work, ZnO-TiO2 nanomaterials with various ZnO/(ZnO+ TiO2) weight ratios (0.1-0.9) were synthesized by using sol-gel and precipitation methods The influence of the ZnO weight ratio (R) and the preparation method on the structural, optical, morphological and photocatalytic properties of the prepared nanomaterials has been studied. The obtained physicochemical characterization results indicated that the crystalline structure, the morphological and the optical properties of the ZnO-TiO2 nanomaterials are strongly influenced by the preparation method as well as the ZnO weight ratio. The results of the photocatalytic degradation of Methyl Orange (MO) in the presence of the synthesized photocatalysts and UV-A light irradiation showed the existence of two domains of ZnO weight ratio. The first is between 0.2 and 0.5 in which the ZnO-TiO2 nanomaterials prepared by sol-gel method exhibited the lowest MO conversion values in comparison with those prepared by precipitation method. These low MO conversion values were due to the intervention of a combination of various parameters that are the particles' agglomeration, the poor crystallinity and the high E-g values. The second corresponds to R >= 0.67 in which the sol-gel method leads to the fabrication of ZnO-TiO2 materials with better photocatalytic efficiencies. The kinetic study showed that the Zn(Pr)-Ti-0.1 sample exhibited the best final MO conversion (99.5%) with the highest apparent rate constant value (0.01763 mn(-1)).