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)-O-.) and sulfate radical (SO4.-), non-radicals mechanism including singlet oxygen (O-1(2)) 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)-O-., 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.

Automated summary

In this study, an electrochemical system was used as a co-catalyst to enhance the activation of peroxymonosulfate for efficient degradation of Sulfamethoxazole. The collaboration of radicals and non-radicals oxidation was found to be responsible for the degradation, with singlet oxygen and Fe(IV) surprisingly involved in the system. The relative contributions of various reactive oxygen species were calculated, and multiple degradation pathways for Sulfamethoxazole were proposed.