Fe(III) hydrolysis-driven Fe(III)/Fe(IV) redox couple for iron sludge-free Fenton-like oxidation

Conventional Fe(II/III) cyclically mediated Fenton processes exhibit strict acid pH-dependence and excessive iron sludge output due to sluggish Fe(III) reduction. Here, we leverage the intrinsic hydrolysis of Fe(III) to strategically modulate its hydroxyl coordination, achieving efficient contaminant degradation through peroxymonosulfate (PMS) activation. Theoretical and experimental results show that hydroxyl coordination accelerates electron transport from Fe(III) to PMS, lowering the energy barrier for simultaneously generating Fe(IV) and sulfate radical. Moreover, Fe(IV) further oxidizes contaminants with Fe(III) regeneration, promoting sustained and complete PMS decomposition via Fe(III/IV) redox couple. Based on this mechanism, a Fe(III)-cycled Fenton-like process operating under neutral conditions was developed for the effective treatment of actual wastewater without iron sludge output. Techno-economic analysis and life cycle assessment confirm its enhanced economic viability and environmental sustainability compared to the conventional Fenton process. This work provides an iron sludge-free and acid pH-independent Fenton-like oxidation strategy for water decontamination. This study reveals that Fe(III) hydrolysis can establish the Fe(III)/Fe(IV) redox couple to activate peroxymonosulfate under neutral conditions. This enables an iron sludge-free and acid pH-independent Fenton-like process for water decontamination.