High photocatalytic activity of zinc metatitanate materials for phenol photodegradation

In this work, we synthesized zinc metatitanate (ZnTiO₃) through a sol-gel method strictly using a 1:1 mol ratio of zinc nitrate and titanium(IV) isopropoxide as the precursors. The calcination temperature was set to 700, 900, and 1100 °C to give ZM-700, ZM-900, and ZM-1100, respectively. These ZM materials were characterized using X-ray diffractometer (XRD), diffuse reflectance ultraviolet-visible (DR UV-vis), Fourier transform infrared (FTIR), and fluorescence spectroscopies. The XRD analyses showed that the ZM-700 contained both cubic-ZnTiO₃ and rhombohedral-ZnTiO₃ phases with a small part of ZnO, while the ZM-900 contained cubic-ZnTiO₃ and cubic-Zn₂TiO₄. In contrast to the ZM-700 and the ZM-900, the ZM-1100 contained cubic-Zn₂TiO₄ and rutile TiO₂ as the main phases with a very small part of the ZnTiO₃ phase. The formation of these crystal phases was also supported by their DR UV-vis spectra, FTIR analysis, and fluorescence spectra. Photocatalytic degradation of phenol was carried out under UV light irradiation for 1–24 h. The kinetic study revealed that the reaction followed first-order, in which the reaction rate constants were 0.0351, 0.0323, 0.0298 h⁻¹ for the ZM-700, ZM-900, and ZM-1100, respectively. This study demonstrated that the formation of ZnTiO₃ was crucial to obtain high photocatalytic activity on the ZM materials. (paper)