Artificial humic acid mediated Fe(II) regeneration to restart Fe(III)/PMS for the degradation of atrazine

The degradation efficiency of organic contaminants using Fenton-like system based on Fe(II) and peroxymonosulfate (PMS) has been hindered by the rapid transformation from Fe(II) to Fe(III) and the slow regeneration of Fe(II). To address this challenge, artificial humic acid (AHA) derived from biomass was incorporated into Fe(III)/PMS system to build AHA/Fe(III)/PMS system. The results demonstrated that the degradation rate of atrazine (ATZ) in AHA/Fe(III)/PMS system (98.83%) is significantly superior to those in Fe(III)/PMS (16.51%) and AHA/PMS system (41.76%) within 90 min. Furthermore, Fe(II) measurement experiments revealed that AHA exhibited more significant iron-reducing potential. The analysis of FTIR, 3D-EEM, and liquid NMR indicated that AHA possessed more structures with reductive potential in comparison to commercial humic acid (CHA) and humic acid extracted from lignite (LHA). The results of persistent free radicals indicated that CHA possessed oxidative potential, which also accounted for the lowest Fe(II) concentration in those system containing CHA. Furthermore, quenching experiments, EPR analysis, and PMSO probe analysis have indicated the presence of reactive species such as •OH, SO₄^•-, and Fe(IV) within AHA/Fe(III)/PMS system. The degradation products from ATZ were identified and determined to exhibit reduced toxicity relative to parent compound. Collectively, these findings presented an in-depth understanding to reactivate Fe(III)/PMS system, offering a promising alternative strategy for efficient degradation of organic pollutants in water treatment processes.