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

Abstract

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 C showed 100% photoreduction of selenite to total selenium, while samples calcined at 350 C and 500 C showed 79% and 17%, respectively.

Agricultural Wastewater Treatment Using Oil Palm Waste Activated Hydrochar for Reuse in Plant Irrigation: Synthesis, Characterization, and Process Optimization

“…To investigate the interaction of the HRT and MLSS parameters, to forecast the optimal operating conditions and their impact on response, i.e., BOD 5 and COD removal, quadratic model equations generated by RSM were developed, as shown by Equations ( 9) and (10).…”

“…COD removal (%) = + 68.03 + 2.80A − 1.61B − 1.17AB − 5.24A 2 + 0.1774B 2 (10) where A and B represent HRT and MLSS, respectively. In Equations ( 9) and ( 10), the positive sign denotes a positive relationship between the component and adsorption capacity, whereas a negative sign denotes an antagonistic impact [36].…”

“…However, the primary issue with most of the above-mentioned solutions is the restriction of the footprint on the current wastewater treatment plant [9]. Biological methods may be a good choice, but it is impossible to reach the regulatory limitations of discharge for this effluent with current procedures [10]. Scientists have been paying close attention to the use of combined activated sludge and biosorption techniques since waste management systems began to change globally owing to the imminent danger of global climate change and other environmental challenges [11,12].…”