This research studied on the synthesis and characterization of nanosized TiO₂, ZnO, and ZnO/TiO₂ composites by hydrothermal process. The effect of preparation parameters i.e. type of precursors, type and concentration of precipitants, precipitation pH, molar ratios of Zn:Ti on properties and photocatalytic activity of the obtained products were performed. The ZnO/TiO₂ composites were prepared by impregnation of TiO₂ powders such as ST-01, P-25, and synthesized from TiOSO₄ precursor in ZnSO₄ solution via hydrothermal process at 150 °C for 6 h with various molar ratios of Zn:Ti (0.5:1, 0.4:1, 0.3:1, 0.2:1, 0.1:1). The obtained composite particles were characterized for phase, microstructure, morphology, specific surface area, and zeta potential. It was demonstrated that the composite prepared from TiO₂ (ST-01) and ZnSO4 solution at 0.1:1 molar ratio of Zn:Ti had the highest photocatalytic activity for degradation of methylene blue solution. The increasing in Zn:Ti ratio had resulted in drastically decrease in its photocatalytic activity due to the agglomeration of ZnO on TiO₂ particles. From the results, it was obtained that preparation of the ZnO/TiO₂ composites was not beneficial to enhance the photoreactivity, since the specific surface area and zeta potential are important factors responding for photocatalytic efficiency.
