Visible-Light-Driven Photocatalytic Degradation of Xanthate in Flotation by g-C₃N₄/ZnIn₂S₄ Heterojunction: Experimental and DFT Studies

Graphitic carbon nitride (g-C₃N₄) and zinc indium sulfide (ZnIn₂S₄) were combined to form CN/ZIS composite materials via a hydrothermal method. The CN/ZIS composites were extensively characterized before they were used for photocatalytic degradation of sodium isobutyl xanthate (SIBX). Results revealed that 3CN/ZIS outperformed other materials, as evidenced by SIBX degradation efficiency of about 8.16 and 5.46 times greater than that of g-C₃N₄ and ZnIn₂S₄, respectively. The improved activity results from the combination of g-C₃N₄ and ZnIn₂S₄. The synergistic effect leads to an enlarged surface area, stronger light absorption, more efficient charge carrier separation, and reduced recombination rates. The mechanisms behind the photocatalytic degradation of SIBX using CN/ZIS were then proposed based on density functional theory (DFT) calculations, band structure analysis, and oxidation-reduction potential. The results verified the successful construction of a Type-II heterojunction between g-C₃N₄ and ZnIn₂S₄. Furthermore, cyclic experiments demonstrate that 3CN/ZIS maintains high degradation efficiency after five cycles, indicating strong chemical stability and promising industrial potential.