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•The sluggish regeneration of Fe3+ ions limits the Fe-based materials from widespread AOP application.•The electron-rich MoS42– centre feed electrons to accelerate the regeneration of Fe3+ ions.•The fast regeneration of Fe3+ ions at LDH backbone influences both the stability and efficiency of the MoS4-LDH/PMS system.
The Fe-based materials were considered very attractive for the treatment of wastewater using peroxymonosulfate (PMS) activation. However, the difficulties to restore the active Fe2+ oxidation state restrict them to attained sustainable efficiency. In this work, a new strategy was introduced to accelerate the regeneration of Fe2+ state through constructing an electron-rich MoS42− centre in the inter-layers of FeMgAl layered double hydroxide (MoS4-LDH) catalyst. The dual centre MoS4-LDH catalyst was found more efficient as clear from the observed atrazine (ATZ) degradation rate of 0.117 min−1, 100 times higher than the Fe3+/PMS or 25–50 times higher than the Fe based single centre NO3-LDH/PMS, CO3-LDH/PMS or S2O4-LDH/PMS systems, respectively. This boosted efficiency was related to the electron-rich MoS42− centre which allows the constant electron transfer to reduce the electron-deficient Fe3+ center at MoS4-LDH surface and thereby accelerating the Fe2+/Fe3+ redox cycle during reaction. Furthermore, the MoS4-LDH/PMS system exhibited a broader effective pH (3.0–9.0), good stability and minimum influence of background electrolyte or organic matter. The degradation pathway of ATZ based on free radical (SO4– and OH), involving the redox cycles of Fe3+/Fe2+ and Mo6+/Mo4+ was proposed for the activation of PMS. This work highlighted the essential role of MoS42− moiety, to accelerate the Fe3+ reduction at the surface of the LDH catalyst through the continuous feeding of electrons.