Removal of chromium from contaminated water using BiVO4/In2S3/S-rGO Z-scheme heterojunction

Hexavalent chromium (Cr (VI)), a highly toxic and carcinogenic heavy metal released from different industrial and mining activities, is difficult to remove effectively. In this study, a Z-scheme heterostructure was designed between BiVO4 and In2S3 to inhibit rapid recombination of photogenerated charge carriers, reduce photo-corrosion of In2S3 NMs, and enhance visible light absorption for efficient Cr (VI) removal from contaminated water. Application of sulphur-doped reduced graphene oxide (S-rGO) was used to increase charge-carrier mobility, promote nucleation, and provide anchoring sites for BiVO4 and In2S3. The BiVO4/In2S3/S-rGO nanocomposite was prepared using a simple hydrothermal technique. The morphological, structural, and electrical characterizations of the prepared nanomaterials (NMs) were performed using FTIR, XRD, FE-SEM, EDX, photoluminescence, UV-DRS, and electrochemical Mott–Schottky measurements. Results demonstrated that the nanocomposite could achieve 91% removal of Cr (VI) from an initial concentration of 25 mg/L within 3 h under solar light irradiation. Furthermore, the efficiency of Cr (VI) reduction by the Z-scheme nanocomposite was increased to 2.5-fold compared to the individual NMs. The Cr (VI) reduction profile best fitted with Langmuir–Hinshelwood (LH) kinetics, and the photocatalysis rate constant (kr) and LH adsorption equilibrium constant (K) were determined to be 0.136 min− 1 and 0.329 L/mg, respectively. The BiVO4/In2S3/S-rGO nanocomposite exhibits excellent recyclability for up to 3 cycles. Thus, the BiVO4/In2S3/S-rGO nanocomposite could be used as a prospective solar-light-driven photocatalytic system for the removal of Cr (VI) from contaminated wastewater.