Mechanistic insights into fluoranthene degradation: Activation of peroxymonosulfate by mackinawite and pyrite in aqueous solution and soil slurry

Abstract

The slow regeneration of Fe(II) in conventional Fenton and Fenton-like systems poses significant limitations for sustained and continuous generation of reactive oxygen species (ROS), which is critical for effective pollutant degradation. This study investigates the use of iron sulfide minerals—specifically, mackinawite (FeS) and pyrite (FeS₂)—as both activators and reductants in peroxymonosulfate (PMS)-based Fenton-like systems to enhance Fe(II) regeneration and improve pollutant degradation efficiency. Results demonstrate that over 90 % of fluoranthene (FLT) was degraded within 60 min using the PMS/FeS and PMS/FeS₂ systems. Reactive species including SO₄⁻•, HO•, and ¹O₂ were generated in both systems, with SO₄⁻• playing a primary role in FLT degradation, while ¹O₂ contributed partially to the process. Both FeS and FeS₂ maintained structural stability during PMS activation, with surface Fe(II) oxidized to Fe(III) and reductive sulfur species (S²⁻ in FeS and S₂²⁻ in FeS₂) facilitating the Fe(III)/Fe(II) cycle before ultimately converting to SO₄²⁻. These systems demonstrated robust performance across diverse water matrices, achieving excellent FLT degradation in actual groundwater and soil slurry, underscoring the promising application potential of PMS/FeS and PMS/FeS₂ systems for remediating FLT-contaminated environments.