Revisiting the contribution of Fe^(Ⅳ)O^(2+)in Fe(Ⅱ)/peroxydisulfate system

Recent studies have proposed that the high-valent iron species(such as Fe^(Ⅳ)O^(2+))rather than sulfate radical(SO_(4)^(·-))and hydroxyl radical(·OH)are the main reactive oxidant species(ROS)in Fe(Ⅱ)/peroxydisulfate(PDS)system with the methyl phenyl sulfoxide(PMSO)as the Fe^(Ⅳ)O^(2+)probe.However,many operational factors may interfere with the accuracy of this method,so the contribution of Fe^(Ⅳ)O^(2+)calculated by this method is controversial.In this study,the possible effect of Fe(Ⅱ)concentration,pollutant type,reducing agent,or coexisted anions on Fe^(Ⅳ)O^(2+)production and its corresponding contribution to the removal of target pollutants in the Fe(Ⅱ)/PDS system were investigated in detail,and the intrinsic mechanisms involved were also explored.This study shows that ROS generation is a complex process in the Fe(Ⅱ)/PDS system,and multiple combinatorial approaches are urgently required to deeply explore the contribution of ROS to the elimination of target contaminants.