Enhanced Fe(III)/Fe(II) Cycle by Lattice Sulfur for Continuous Fenton Reactions

The Fenton reaction is usually limited by the sluggish regeneration of Fe(II). In this article, we developed a Fenton system that uses metal sulfides (MS_x) and diluted Fe(III) to activate H₂O₂, and the enhanced mechanism of the Fe(III)/Fe(II) cycle in the presence of sulfides was investigated. The lattice sulfur of MS_x can donate electrons to reduce Fe(III) into Fe(II) and is partially oxidized to SO₄^2– during H₂O₂ activation. •OH and ¹O₂ are the primary reactive oxygen species for pollutant removal. Meanwhile, low-cost iron-based sulfide (FeS_x) is selected for scale-up experiments in a fixed-bed reactor, which can maintain 100% atrazine degradation over 240 h. Additionally, the Fukui function is employed to analyze the selective degradation pathway of atrazine, and the biological toxicity of the organic intermediates is also assessed. The novel FeS_x/Fe(III) system provides a potential alternative to the traditional Fenton reaction.