Treatment of chromium-contaminated water using a highly efficient, novel ternary synergistic S–rGO–BiOBr–In2S3 heterojunction

Abstract

The goal of the current study is to form a Z-scheme heterojunction between narrow band gap In₂S₃ (indium sulphide) and wide band gap BiOBr (bismuth oxobromide) to minimize the photoinduced charge carrier recombination and increase the visible light harvesting capacity of the nanocomposite for Cr(VI) elimination from polluted water. The exfoliated and corrugated S-doped rGO (sulphur-doped graphene oxide) were used to enhance the surface area and conductivity, encourage nucleation, and act as anchor sites for interfacial contact between BiOBr and In₂S₃ to facilitate efficient charge transfer. In this work, a BiOBr–In₂S₃–SrGO nanocomposite was successfully synthesized by a facile hydrothermal method. The optical and physicochemical properties of the synthesized nanomaterials (NMs) were characterized using XRD, FTIR, FE-SEM, EDAX, HRTEM, XPS, UV-DRS, Raman and photoluminescence spectroscopy. The results reveal that almost 96.6% Cr(VI) removal was achieved from an initial Cr(VI) dose of 100 mg L⁻¹ by the nanocomposite within 2 h under the illumination of solar light. On the other hand, the Cr(VI) reduction was limited to 33.4% and 30.9% using the individual NMs of BiOBr and In₂S₃, respectively. The reduction of Cr(VI) follows pseudo-first-order kinetics. The calculated apparent rate constant (K_app) of the nanocomposite was 3 times more than the individual NMs of BiOBr and In₂S₃, with an excellent recycling activity.