Self-cycling of Fe(II)/Fe(III) and the important role of Fe(IV) in promoting efficient degradation of atrazine (ATZ) in a wider pH range

Abstract

The Fe(II)/Fe(III)@C catalysts were prepared by doping Fe2+ into MIL-101(Fe) as a template at high temperature. Through systematic and comprehensive characterization (SEM, XRD, FTIR, etc.), it was demonstrated that Fe elements were uniformly attached to the particle surface, providing excellent active sites for activation of peroxymonosulfate (PMS), and were successfully used for the degradation of atrazine (ATZ) in water. The effects of different environmental factors on the degradation of ATZ were investigated, and it was found that ATZ was still efficiently degraded (>95%) in a wide pH range (pH of 3–9). After quenching as well as ESR spectroscopic detection jointly suggested the contribution of substances that play a role in the system: 1O2 (71%) > ∙OH (32%) > SO4∙− (25%) > Fe(IV) (12.5%)> O2∙− (7%). After PMSO was used as a probe, the important role of Fe(IV) in the system was verified. Furthermore, the intermediates in the degradation of ATZ were detected by GC-MS and their toxicity was analyzed. Finally, two pathways of Fe(II)↔Fe(III) cycling were proposed in combination with the above experimental and computational contents, and multiple cycle tests including different contaminant tests were performed to verify the application potential of Fe(II)/Fe(III)@C-system. This work provides a research basis for the activation of MOF-derived carbon-based catalysts for the degradation of organic pollutants by PMS.