Effect of Calcination Temperature on the Morphology, Crystallinity, and Photocatalytic Activity of ZnO/TiO2 in Selenite Photoreduction from Aqueous Phase

In this study, ZnO/TiO2 was synthesized using the sol-gel method. The effect of calcination temperature was investigated on the morphology, crystal size, and influence on the photoreduction of selenite from the aqueous phase. The ZnO/TiO2 was calcined at 150 C, ̊ 350 C, ̊ and 500 ̊C for 2 hours. The samples were characterized using SEM/EDX, XRD, and FT-IR for morphology/elemental composition, crystal structure/size, and functional group. The crystallite sizes were found to be 21.61 nm, 22.22 nm, and 24.80 nm for the temperatures, respectively. The composite morphology was found to be agglomerated granular particles that increase in agglomeration as the temperature increases. EDS results give the composition of Ti, Zn, and O2 in all samples, indicating the presence of ZnO and TiO2. XRD spectra were used to confirm the hexagonal and tetrahedral phase structure of the ZnO and TiO2. Photocatalysis experiment was conducted at pH 4 and 1 mg/L ZnO/TiO2 with 20 ppm initial concentration for 22 hrs under UV-irradiation. The catalyst calcined at 150 C̊ showed 100% photoreduction of selenite to total selenium, while samples calcined at 350 C̊ and 500 C̊ showed 79% and 17%, respectively.