Adjusting radical/non-radical species ratio in MnO2/CoFe2O4 activated peroxymonosulfate system through changing inner-outer positioning for enhanced endocrine disrupting chemicals degradation: A comparative study

Herein, binary composite catalysts based on MnO 2 and CoFe 2 O 4 were prepared to degrade bisphenol A (BPA) and dimethyl phthalate (DMP) by coupling with peroxymonosulfate (PMS), in which CoFe 2 O 4 was located either at the outer (MnO 2 @CoFe 2 O 4 ) or at the inner (CoFe 2 O 4 @MnO 2 ) positioning. The catalysts possessed higher degradation efficiency than both pristine CoFe 2 O 4 and MnO 2 , in which MnO 2 @CoFe 2 O 4 provided the highest PMS activation capability. The positioning of each component influenced significantly the variety and intensity of the generated reactive oxidative species, in which MnO 2 @CoFe 2 O 4 generated more hydroxyl radical ( OH) whereas CoFe 2 O 4 @MnO 2 generated more non-radical singlet oxygen ( 1 O 2 ). Therefore, MnO 2 @CoFe 2 O 4 could degrade both BPA and DMP with high degradation rate, while CoFe 2 O 4 @MnO 2 only exhibited promising degradation efficiency towards BPA since DMP was inert to 1 O 2 . Comparatively, CoFe 2 O 4 @MnO 2 had better catalytic stability and water matrix adaptability than MnO 2 @CoFe 2 O 4 when degrading BPA, since OH was vulnerable water with complicated compositions. This study provides a new insight for the design and selection of composite catalyst towards the degradation of organic pollutants with discrepant structures and properties.