The role of reactive phosphate species in the abatement of micropollutants by activated peroxymonosulfate in the treatment of phosphate-rich wastewater

This study investigated the mechanisms of forming reactive species to degrade micropollutants through the activation of peroxymonosulfate (PMS) by phosphate, a prevalent ion in wastewater. Considering the density functional theory results, the formation of hydrogen bonds between phosphate and PMS molecules might be the crucial step in the overall reactions, which prefers producing ^⋅OH and reactive phosphate species (RPS, namely H₂PO₄^⋅, HPO₄^⋅−, and PO₄^⋅2−) to yielding SO₄^⋅−. Besides, in the phosphate (5 mM)/PMS system at pH = 8, HPO₄^⋅− was modeled to be the dominant radical with a steady-state concentration of 3.6 × 10⁻¹² M, which was 666 and 773 times higher than those of ^⋅OH and SO₄^⋅−. The contributions of ¹O₂, ^⋅OH, SO₄^⋅−, and RPS to the micropollutant decomposition in phosphate/PMS were studied, and RPS were found to be selective for micropollutants with electron-donating moieties (such as phenolic and aniline groups). Additionally, the degradation pathways of bisphenol A, diclofenac, ibuprofen, and atrazine in phosphate/PMS were proposed according to the detected transformation products. Cytotoxicity analysis was carried out to evaluate the potential environmental impacts resulting from the degradation of micropollutants by phosphate/PMS. This study confirmed the significance of RPS for micropollutant degradation during PMS-based treatment in phosphate-rich scenarios.