Hydroxylamine promoted hydroxyl radical production and organic contaminants degradation in oxygenation of pyrite

The heterogeneous Fenton-like process using pyrite (FeS2) is increasingly recognized as a promising advanced oxidation process for removal of organic contaminants. However, the slow regeneration of Fe(II) limits the generation of reactive oxygen species for environment implication. To overcome this drawback, hydroxylamine was applied to enhance the reactivity of FeS2 to degrade organic contaminants under oxic conditions. Results showed that hydroxylamine facilitated the regeneration of Fe(II) on FeS2 surface to promote reactive oxygen species generation, thereby efficiently degrading different organic contaminants. The underlying mechanism was further elucidated that the presence of hydroxylamine enhanced electron transfer from FeS2 to O2 to produce superoxide radicals (O2•-), hydrogen peroxide (H2O2) and hydroxyl radical (HO•) via Fenton-like pathways, which induced the rapid degradation of organic contaminants (e.g., sulfamethoxazole (SMX)). The reactivity of FeS2 for organic contaminant degradation changed negligibly after seven cycles in the presence of hydroxylamine. The effects of pH and inorganic anions on SMX degradation were also clarified in details. The finding of this study would provide a novel strategy to enhance the contaminants degradation by FeS2-based advanced oxidation technologies for environmental remediation.