Rapid Selective Circumneutral Degradation of Phenolic Pollutants Using Peroxymonosulfate–Iodide Metal-Free Oxidation: Role of Iodine Atoms

The development of environmentally friendly, oxidation-selective advanced oxidation processes (AOPs) for water decontamination is important for resource recovery, carbon dioxide abatement, and cost savings. In this study, we developed an innovative AOP using a combination of peroxymonosulfate (PMS) and iodide ions (I^–) for the selective removal of phenolic pollutants from aqueous solutions. The results showed that nearly 100% degradation of phenol, bisphenol A, and hydroquinone was achieved after reaction for 4 min in the presence of 65 μM PMS and 50 μM I^–. PMS-I^– oxidation had a wide effective pH range, with the best performance achieved under circumneutral conditions. The ratio between [PMS] and [I^–] influenced the degradation, and the optimal ratio was approximately 1.00 for the degradation of the phenols. Neither sulfate nor hydroxyl radicals were found to be the active species in PMS-I^– oxidation. Instead, we found evidence that iodide atoms were the dominant oxidants. In addition, both Cl^– and Br^– also promoted the degradation of phenol in PMS solution. The results of this work may promote the application of reactive halogen species in water treatment.