Synergistic effect of Zn-AgIn5S8/CdS Z-scheme heterojunction and S-doped rGO for efficient removal of chromium from contaminated water

Abstract

This study aimed to synthesize a Zn-AgIn₅S₈/CdS/SrGO nanocomposite for Cr(VI) removal from contaminated water under solar irradiation. To prevent photo corrosion of CdS, a Z-scheme heterojunction was formed between CdS and Zn-AgIn₅S₈. The introduction of Ag²⁺ plasmonic materials extended the light absorption range and stabilized the photocatalyst. Further, to improve the catalytic surface area, electrical conductivity, and minimize the rate of electron and hole pair recombination, the Zn-AgIn₅S₈/CdS Z-scheme heterojunction was loaded onto S-doped rGO. The morphological and structural analysis of the synthesized nanomaterials (NMs) was done using various techniques, including XRD, FT-IR, UV-vis DRS, FESEM, TEM, EDAX, photoluminescence, and Raman spectroscopy. Results revealed that the Zn-AgIn₅S₈/CdS/SrGO nanocomposite removed 85% of Cr(VI) at an initial concentration of 50 mg L⁻¹ in 180 min when exposed to solar irradiation. The simulated first-order kinetic model fitted to the experimental data for Cr(VI) reduction by the nanocomposite exhibits a high correlation coefficient (R² ≥ 0.97) and the K_app value for Zn-AgIn₅S₈/CdS/SrGO (K_app = 0.0114 min⁻¹) is around 1.6 times larger than that of bare ZnAgIn₅S₈. Moreover, Zn-AgIn₅S₈/CdS/SrGO heterojunctions show excellent reusability up to 4 cycles. Further, the possible photocatalytic mechanism of Cr(VI) reduction has been proposed. Therefore, the Zn-AgIn₅S₈/CdS/SrGO nanocomposite could serve as an alternative photocatalyst system driven by solar light for Cr(VI) reduction.