Recent advances in solar-enhanced homogeneous water decontamination and disinfection: A review

Homogeneous solar/oxidant systems have emerged as cost-effective treatments for removing organic micropollutants and disinfecting pathogenic bacteria in water. However, detailed discussions regarding the effectiveness and mechanisms for water decontamination and disinfection have not been conducted yet. This paper reviewed and compared the decontamination and disinfection performance of homogeneous solar/oxidant systems, including solar-activated hydrogen peroxide, peroxydisulfate, peroxymonosulfate, chlorine, peracetic acid, ferrate, and periodate. The activation mechanisms of different oxidants by sunlight are summarized, where oxidants were activated under solar irradiation to produce multiple reactive species to remove micropollutants and inactivate bacteria. Notably, different reactive species promoted different conversion pathways for micropollutants, and the in silico toxicity predictions suggested the non-overlooked transformation-derived risks from the degradation products of micropollutants. Furthermore, the economic cost analysis of all solar/oxidant systems studied suggested that the overall costs were acceptable, while some other factors in practical applications needed to be reconsidered. Finally, research perspectives on solar-based oxidation technologies in terms of water decontamination and disinfection were provided. In summary, this review facilitates an understanding of the fundamental principles and oxidizing mechanisms of different solar/oxidant systems in water and wastewater treatment.