Impact of heat treatment and composition of ZnO-TiO2 nanoparticles for photocatalytic oxidation of an azo dye

TiO2-ZnO mixed oxide nanoparticles were synthesized by precipitation of zinc nitrate and titanium tetrachloride as precursors and then heat treated using two techniques: hydrothermal and calcination. The particles were characterized using XRD, BET, UV diffuse reflectance, and potential techniques. Additionally, the particles were tested for their ability to induce the photocatalytic oxidation and adsorption of Procion Red MX-5B dye. The highest photocatalytic oxidation was observed for nanoparticulate mixed oxides that were near 100% ZnO or TiO2. These materials did not have the highest specific surface areas, yet it is believed that their near-neutral potentials and ideal band gap energies contributed to their higher photocatalytic activities. XRD patterns indicated that sintering and increased crystallinity occurred for the calcined TiO2 samples.