Photodegradation of Xanthate Using a Bi₂Fe₄O₉/ZnIn₂S₄ Heterojunction: Experimental and DFT Studies

Bi2Fe4O9/ZnIn2S4 (BFO/ZIS) composites are synthesized by using a facile impregnation method and tested for the photocatalytic degradation of xanthate for the first time. The effects of multiple parameters, including catalyst dosage and the pH value of solution, on xanthate photodegradation are investigated systematically. Furthermore, the photocatalytic mechanisms of BFO/ZIS are proposed based on various characterizations and density functional theory calculations. Results show that the degradation efficiency of 30BFO/ZIS is 98.25% during 90 min of visible light irradiation, which is 2.63 and 2.89 times higher than that of pure ZIS and BFO, respectively. This is mainly because the type II heterojunction formed between BFO and ZIS improves the separation of photogenerated carriers. Furthermore, the xanthate photodegradation efficiency of 30BFO/ZIS decreases slightly from 98.25 to 92.86% after four cycles, indicating its excellent durability and stability. Finally, the chemical oxygen demand (COD) removal efficiency of 30BFO/ZIS is up to 81.06%, exhibiting a high degree of mineralization.