Deposition of zinc oxide on zinc plates for photocatalytic removal of dyes in aqueous system

Abstract

This research involves modification of Zn pure and Zn alloy plates to be utilized for dye removal. The modification is aimed to produce ZnO layer on the surface of Zn pure and Zn alloy plates. Sand blasting technique is used to remove a naturally formed oxide layer on Zn pure and Zn alloy plates. The sand blasting technique is also intended to produce a curved groove site to strengthen the ZnO layer formed on the surface of modified Zn pure and Zn alloy plates. The modification of Zn pure and Zn alloy plates consist of three different methods, electrolysis, immersing in H2O2 and heating. Based on the analysis of DR UV-Vis, SEM and XRD, all three modification methods successfully produced ZnO layer on Zn pure and Zn alloy plates. The formation of ZnO layer is different in thickness and electrolysis is chosen as the best technique for the ZnO layer production. Methylene blue dye (20 ppm, pH 6.56) is utilized as a sample solution to study the removal activity of modified Zn pure and Zn alloy plates. Results obtained from UV-Vis spectra shows that the percentage of methylene blue removal by modified Zn pure plate and was 81.9% and 70.0% respectively Zn alloy plate. Results also showed that adsorption and photocatalysis are involved in the removal of methylene blue dye. Adsorption becomes a major contributor for the removal of methylene blue dye where it contributes 50% of methylene blue removal and photocatalysis only contributes 30% of methylene blue removal. It was also observed that desorption of the methylene blue will occur if the plates are placed in beaker containing distilled water. Modified Zn pure and Zn alloy plates have a “weak adsorption” and “strong desorption” characteristics. The “weak adsorption” and “strong desorption” behaviours of the modified Zn pure and Zn alloy was utilized to create an integrated chemical for application in wastewater treatment in textile industry. This system combines adsorption and photocatalysis techniques for the removal of dye molecules in textile wastewater. The main benefit of this system is that it can separate the dye molecules from wastewater by weak adsorption and transferred dye molecule into a special tank by “strong desorption”. The transferred dye molecules could be recycled and used again by the factories.