Insights into the generation of multiple reactive species in UV254/PMS/I− system and their roles for degradation of phenolic and non-phenolic pollutants

An innovative technology for the removal of phenolic and non-phenolic organic pollutants from aqueous solution was developed by combining UV 254 irradiation, peroxymonosulfate (PMS), and iodide ions (I − ). Effects of pH, ratio of [I − ]/[PMS], initial concentration of pollutant, dissolved organic matter (DOM) and typical inorganic constituents of environmental water on the degradation of studied pollutants with UV 254 /PMS/I − system were examined. The results showed that pH and [I − ]/[PMS] exhibited significant impact on the degradation of pollutants during UV 254 /PMS/I − process. As the ratio of [I − ]/[PMS] increased from 0.1 to 10.0, the removal efficiencies of phenolic pollutants remarkably increased, but those of non-phenolic pollutants decreased. The DOM at high concentration obviously inhibited the degradation of pollutants during UV 254 /PMS/I − process. Meanwhile, the occurrence of NO 3 − can slightly enhance the degradation of pollutants, and SO 4 2− , Cl − , and HCO 4 − ions had no significant effects on UV 254 /PMS/I − system. The abundant reactive species including OH, SO 4 − , and I /I 2 − during UV 254 /PMS/I − process were generated based on electron spin resonance, fluorescence spectroscopy and steady-state concentration analysis. Quenching experimental results indicated that I /I 2 − can selectively degrade phenolic pollutants via one-electron oxidation. This study provided a reference for the application of reactive radicals involved oxidative technique in water purification .