Mechanochemically synthesized sulfidated magnetite: A novel activator of permonosulfate for Fe(IV) dominated degradation of atrazine

Abstract

Magnetite has been recognized as a highly promising material for persulfate activation. As well, sulfidation has been shown to enhance the activation ability of iron-based materials utilized in various advanced oxidation processes. However, the conventional liquid-based preparation method limits their activity and scalability. In order to address these issues, this study introduces a novel mechanochemical (high energy ball milling) approach to prepare sulfidated magnetite (S-Fe3O4BM) using for the first time. The properties of S-Fe3O4BM were evaluated for their ability to activate peroxymonosulfate (PMS) and degrade atrazine. Such a system could rapidly degrade atrazine in 180 s, which is approximately 80 % less time compared to previous studies. Among the tested samples, S-Fe3O4BM milled for 12 h showed the highest catalytic stability, achieving a 95 % degradation when reused for 3 times. Competition kinetics experiments revealed that only 9.38 % of the degradation was attributable to radicals, while Fe(IV) played a predominant role. Thermodynamic calculations highlighted the high favorability (ΔG ≪ 0) of the reaction pathway involving Fe(IV). Furthermore, the sizes of reactive species generated in the system explained the distinct distribution of intermediates in each process.