Photocatalytic degradation of hexavalent chromium and different staining dyes by ZnO in aqueous medium under UV light

Abstract

In this study, ZnO catalyst were synthesized using zinc nitrate and Terminalia arjuna bark extract under microwave irradiation. This ZnO catalyst prepared through phytochemical route was characterized by UV–Vis spectra, FTIR, XRD, XPS, TG/DSC, FE-SEM, and BET specific surface area. The photocatalytic degradation of Cr(VI) and dyes viz., toluidine blue o (TBO), safranin o (SFO) and calcon carboxylic acid (CCA) in aqueous solution was carried out using ZnO catalyst under UV light irradiation (250 W). The XPS of ZnO used for Cr(VI) degradation confirmed the adsorbed Cr(III) on its surface. When 5 ppm (1 L) of Cr(VI) or dyes were treated with 0.1 g of photocatalyst (ZnO), the degradation was found to be 68% Cr(VI), 94% TBO, 87% SFO and 92% CCA in about 300, 190, 310 and 260 min, respectively, based on the estimation of their concentration using UV–Vis spectra. The dye degradation followed pseudo first-order kinetics. The degradation of TBO, SFO and CCA were also confirmed from LC-MS analysis.