Cr(VI) reduction performance of KNbO₃/SnS₂ composite photocatalysts

To solve the adverse effects of heavy metal ions of hexavalent chromium on the human body and environmental pollution, the KNbO₃ pure phase was synthesized by the hydrothermal method with potassium hydroxide and niobium oxide as raw materials for 12 hours at 180 ℃. Based on synthesizing pure phase KNbO₃, tin chloride pentahydrate, and thioacetamide raw materials were added, and KNbO₃/SnS₂ composite photocatalysts with high visible light catalytic activity were synthesized after hydrothermal treatment at 190 ℃ for 6 hours. The crystal structure, micromorphology and chemical valence of the prepared samples were characterized by XRD, SEM, TEM, XPS, and UV-Vis DRS, and the photocatalytic activity of the samples for hexavalent chromium reduction was tested. UV-visible diffuse reflection spectra show that the synthesized KNbO₃/SnS₂ composite photocatalysts have an optical bandgap of about 2.21 eV. Experimental results show that all KNbO₃/SnS₂ composite photocatalysts have high visible light catalytic activity, and show the highest visible light catalytic activity when the KNbO₃/SnS₂ ratio reaches 1∶3. After 40 minutes of illumination, the reduction efficiency of Cr(VI) aqueous solution reaches 95.4%, indicating that the synthesis of KNbO₃/SnS₂ composite photocatalyst can improve the utilization rate of visible light and enhance the effective separation of photogenerated electron-hole pairs, thereby improving the photocatalytic efficiency of the composite catalyst.