Mitigation of caffeine micropollutants in wastewater through Ag-doped ZnO photocatalyst: mechanism and environmental impacts.

Micropollutants, such as caffeine (M-CF), pose a significant threat to ecosystems and human health through water and food sources. The utilization of metal oxide-based photocatalysts has proven to be an effective treatment method for the removal of organic pollutants. This study explores the efficacy of Ag-doped ZnO (Ag/ZnO) for removing M-CF from wastewater. The characterization of Ag/ZnO underscores the crucial role of band gap energy in the photocatalytic degradation process. This parameter influences the separation of electrons and holes (e/h) and the generation of reactive radicals. Under solar light, Ag/ZnO demonstrated markedly superior photocatalytic activity, achieving an impressive degradation efficiency of approximately 93.4%, in stark contrast to the 53.2% occurred by ZnO. Moreover, Ag/ZnO exhibited a remarkable degradation efficiency of M-CF in wastewater, reaching 83.5%. A key advantage of Ag/ZnO lies in its potential for recovery and reuse in subsequent treatments, contributing to a reduction in operational costs for industrial wastewater treatment. Impressively, even after five cycles, Ag/ZnO maintained a noteworthy photodegradation rate of M-CF at 78.6%. These results strongly suggest that Ag/ZnO presents a promising solution for the removal of micropollutants in wastewater, with potential scalability for industrial and large-scale applications.