Synergistic Modification of ZnIn ₂ S ₄ with Biochar and Europium for Enhanced Photocatalytic Antibiotic Degradation

The widespread presence and persistence of organic pollutants in aquatic environments have raised serious concerns worldwide due to their adverse ecological and health impacts. Therefore, there is an urgent need to develop efficient and sustainable degradation technologies. In this study, a novel photocatalyst composed of rice straw biochar and rare-earth europium comodified ZnIn2S4 was synthesized. The degradation efficiency of pristine ZnIn2S4 for metronidazole (MNZ) under visible light reached 70.5%. Subsequent modification with rice straw biochar and rare-earth europium resulted in a highly efficient degradation performance, achieving a degradation efficiency of 99.8%. Notably, the composite also demonstrated effective MNZ degradation under natural sunlight. Mechanistic investigations revealed that the comodification with rice straw biochar and europium synergistically enhances light absorption, facilitating charge separation. This study offers a feasible strategy for the rational design of highly efficient photocatalysts and underscores their potential for practical applications in antibiotic-contaminated water treatment.