The degradation profile of high molecular weight textile reactive dyes: A daylight induced photocatalytic activity of ZnO/carbon quantum dot photocatalyst

Abstract

Advancement in developing daylight-induced photocatalyst has received enormous potential to degrade textile toxic dyes. In textile industry, while processing to fabricate an appealing color shade on cotton fabrics, it is inevitable to use mixture of high molecular weight (HMW) reactive dyes. Indeed, most of the recent reports mainly focused on degrading low molecular weight (Mol.wt: <400) dyes including methyl orange, methylene blue, malachite green and rhodamine dyes. However, it is hard to find reports on degrading HMW textile dyes particularly under daylight irradiation. Herein, three different HMW reactive dyes such as reactive orange (RO, Mol.wt: 762.04) reactive red (RR, Mol.wt: 1469.98), and reactive blue (RB, Mol.wt: 2248.57) were chosen to investigate the real time photocatalytic performance using zinc oxide/carbon quantum dots (ZnO/C-dots) under daylight irradiation. The maximum dye degradation of 85 % of RO dye was achieved after 8 h of daylight irradiation. The total time required for complete degradation of an individual HMW dye also measured. The impact of pH and amount of photocatalysts towards the degradation profile of HMW dyes were examined and compared the degradation profile with relevant reports. The formation of OH and holes are the main active reactive species for the ZnO/C-dots photocatalyst to degrade HMW dyes under daylight irradiation. Thus, it is confirmed that the ZnO/C-dot photocatalyst can be useful for real-time wastewater treatment in textile industry to degrade HMW dyes under daylight irradiation.