Simultaneous removal of Cr(VI) and phenol contaminants using Z-scheme bismuth oxyiodide/reduced graphene oxide/bismuth sulfide system under visible-light irradiation

Abstract

An all-solid-state Z-scheme system containing Bi-based semiconductors bismuth oxyiodide (BiOI) and bismuth sulfide (Bi₂S₃) was constructed on reduced graphene oxide (rGO) sheets through an electrostatic self-assembly method to simultaneously remove aqueous Cr(VI) and phenol. In this Z-scheme that mimicked natural photosynthesis, photoinduced electrons in the conduction band (CB) of BiOI were transferred through rGO and reacted with photoinduced holes in the valence band (VB) of Bi₂S₃, which significantly increased its photocatalytic activity. The reduction and oxidation reactions were performed on Bi₂S₃ and BiOI photocatalysts, respectively. Furthermore, complex contaminants of coexisting heavy metal Cr(VI) and organic phenol were treated using the system under visible-light irradiation. Results showed that Cr(VI) reduction and phenol oxidation were achieved efficiently with optimum reductive and oxidative efficiencies up to 73% and 95% under visible-light irradiation, respectively. This work provided a promising method of simultaneously removing heavy metals and organic pollutants by using a Z-scheme system with enhanced photocatalytic activity.

Keywords: BiOI/rGO/Bi(2)S(3); Cr(VI) reduction; Phenol degradation; Visible-light photocatalysis; Z-scheme photocatalytic system.