Pyrite enables persulfate activation for efficient atrazine degradation

Persulfate (PS) is widely used for environmental remediation, but its organic contaminant removal performance strongly depends on its activation. In this study, we demonstrate that pyrite (FeS₂) can more effectively activate PS than the commonly used FeSO₄ for atrazine degradation. When 3.0 mM of PS and 4.2 mM of iron salts were used, the atrazine degradation efficiency of FeS₂/PS was 1.4 times that of FeSO₄/PS, while the amount of consumed PS in case of FeS₂ was only 53% of that by FeSO₄. The better PS activation performance of FeS₂ could be attributed to its slow and sustainable release of dissolved Fe(II), inhibiting the quenching reaction between •SO₄^-/•OH and Fe(II) ions, and thus producing more reactive oxygen species for the atrazine degradation. More importantly, the surface bound Fe(II) of FeS₂ could activate molecular oxygen to generate superoxide radical (•O₂^-), which could further promote the effective decomposition of PS by accelerating the Fe(III)/Fe(II) redox cycle. This study unravels the roles of dissolved Fe(II) and surface bound Fe(II) on the persulfate activation, and provides a promising heterogeneous persulfate activator for pollutant control and environmental remediation.