EDTA promoted Cr(VI) reduction in semiconductor/insulator photocatalyst: Performance, mechanistic insight and DFT calculation

Abstract

Here, a novel CdS/BaCO3 composite catalyst was fabricated by a simple chemical precipitation method. The optical and photoelectrochemical characterizations suggest that the charge separation and transportation in CdS/BaCO3 are significantly enhanced, compared to that in CdS. As a results, the optimized CdS/BaCO3 shows superior hexavalent chromium (Cr(VI)) degradation rates, which is 76.4 times higher than that of CdS. More interestingly, the adding of trace EDTA (Ethylene Diamine Tetraacetic Acid) further promote the photocatalytic Cr(VI) removal ratio of CdS/BaCO3 to 99 %, at a significantly enhanced rate (0.247/min) 236.87 and 114.22 times more than that of CdS and EDTA. In combination with DFT theoretical calculations, the analysis on band levels suggests that under visible light, the interband states of Ba2+ of BaCO3 inhibit the recombination of electron-hole pairs in CdS and improves the electron transmission efficiency and the formation of a complex between EDTA and the composite catalyst, which increase of active groups and the generation of H2O2 in the solution for boosting Cr(VI) reduction. The design of small-molecule-promoted insulators/semiconductor heterojunctions for enhancing Cr(VI) degradation offers broad application prospects in environmental remediation.