Sustainable Fe(III)/Fe(II) cycles triggered by co-catalyst of weak electrical current in Fe(III)/peroxymonosulfate system: Collaboration of radical and non-radical mechanisms

Herein, an electrochemical (EC) system was applied as “co-catalyst” to enhance the activation of peroxymonosulfate (EC/Fe(III)/PMS) for efficient Sulfamethoxazole (SMX) degradation. The cathodic reduction reaction can facilitate electron transfer to Fe(III) and trigger the sustainable Fe(III)/Fe(II) redox cycle. Unexpectedly, in addition to hydroxyl radical (•OH) and sulfate radical (SO4•−), non-radicals mechanism including singlet oxygen (1O2) and Fe(IV) were also found involved in EC/Fe(III)/PMS system. The degradation of SMX in EC/Fe(III)/PMS system was accomplished by the collaboration of radicals and non-radicals oxidation. The generation routes and mechanisms of involved reactive oxygen species (ROS) were explored. The relative contributions of •OH, SO4•−, and nonradical species for the degradation of SMX were calculated to 4.75 %, 25.31 %, and 69.94 %, respectively. Besides, multiple degradation pathways of SMX were proposed by identifying the formed byproducts. The EC/Fe(III)/PMS process could efficiently degrade SMX under the influence of co-existing ions and inactivate pathogens in the wastewater.