Identifying the evolution of primary oxidation mechanisms and pollutant degradation routes in the electro-cocatalytic Fenton-like systems

Herein, electro-catalysis (EC) as the electron donor to accelerate the continuable Fe(III)/Fe(II) cycles in different inorganic peroxides (i.e., peroxymonosulfate (PMS), peroxydisulfate (PDS) and hydrogen peroxide (HP)) activation systems were established. These electro-cocatalytic Fenton-like systems exhibited an excellent degradation efficiency of sulfamethoxazole (SMX). A series of analytical and characterization methods including quenching experiments, probe experiments, and electron paramagnetic resonance spectrometry (EPR) were implemented to systematically sort out the source and yield of reactive oxygen species (ROS). A wide kind of ROS including hydroxyl radical ((OH)-O-center dot), singlet oxygen (O-1(2)), and sulfate radical (SO4 center dot- )(,) which contributed 38%, 37%, and 24% were produced in EC/Fe(III)/PMS system, respectively. (OH)-O-center dot was the dominant ROS in both EC/Fe(III)/ PDS and EC/Fe(III)/HP processes. According to the analysis of SMX degradation routes and biotoxicity, abundant degradation pathways were identified in EC/Fe(III)/PMS process and lower environmental impact was achieved in EC/Fe(III)/HP process. The diversiform ROS of EC/Fe(III)/PMS system makes it exhibit greater environmental adaptability in complex water matrixes and excellent low-energy consumption performance in many organic pollutants degradation. Continuous flow treatment experiments proved that the three systems have great sus-tainability and practical application prospect. This work provides a strong basis for constructing suitable systems to achieve different treatment requirements.

Automated summary

In this study, sustainable Fe(III)/Fe(II) cycles in different inorganic peroxides activation systems were accelerated by using electro-catalysis (EC) as the electron donor. The electro-cocatalytic Fenton-like systems exhibited excellent degradation efficiency of sulfamethoxazole (SMX). Various reactive oxygen species (ROS) including hydroxyl radical ((OH)-O-center dot), singlet oxygen (O-1(2)), and sulfate radical (SO4 center dot-) were produced in EC/Fe(III)/PMS system, contributing to 38%, 37%, and 24% respectively. The dominant ROS in EC/Fe(III)/ PDS and EC/Fe(III)/HP processes was (OH)-O-center dot. The study provides a strong basis for constructing suitable systems to achieve different treatment requirements.