Heterogeneous degradation of organic contaminants by peracetic acid activated with FeCo2S4 modified g-C3N4: Identification of reactive species and catalytic mechanism

In this study, a novel Fe/Co bimetallic spinel sulfide (FeCo2S4) modified g-C3N4 composite (FeCo2S4-CN) was prepared by a hydrothermal method and firstly applied as a catalyst for the activation of peracetic acid (PAA) at neutral pH. The efficient rhodamine B (RhB) degradation in FeCo2S4-CN/PAA system indicated that PAA was successfully activated by FeCo2S4-CN. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) results indicated that g-C3N4 carrier could anchor FeCo2S4 particles with good dispersion. The X-ray photoelectron spectroscopy (XPS) analysis suggested that the surface ≡Co(II) and ≡Fe(II) could activate PAA to form CH3C(O)O• and •OH, synchronously yielding ≡Co(III) and ≡Fe(III). Meanwhile, the surface ≡Co(III) and ≡Fe(III) could also react with PAA to generate CH3C(O)OO• as well as ≡Co(II) and ≡Fe(II), resulting in the redox cycles of ≡Co(II)/≡Co(III) and ≡Fe(II)/≡Fe(III). Besides, the presence of S2- in FeCo2S4-CN was favorable to these redox cycles. Radical scavenging experiments confirmed that organic radicals (i.e., CH3C(O)O• and CH3C(O)OO•) were the primary reactive species for RhB degradation in FeCo2S4-CN/PAA system. This system also exhibited a high removal efficiency for various organic contaminants, suggesting its potential application in degrading refractory pollutants.