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

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 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 Kapp value for Zn-AgIn5S8/CdS/SrGO (Kapp = 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.