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 MnO2 and CoFe2O4 were prepared to degrade bisphenol A (BPA) and dimethyl phthalate (DMP) by coupling with peroxymonosulfate (PMS), in which CoFe2O4 was located either at the outer (MnO2@CoFe2O4) or at the inner (CoFe2O4@MnO2) positioning. The catalysts possessed higher degradation efficiency than both pristine CoFe2O4 and MnO2, in which MnO2@CoFe2O4 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 MnO2@CoFe2O4 generated more hydroxyl radical (OH) whereas CoFe2O4@MnO2 generated more non-radical singlet oxygen (1O2). Therefore, MnO2@CoFe2O4 could degrade both BPA and DMP with high degradation rate, while CoFe2O4@MnO2 only exhibited promising degradation efficiency towards BPA since DMP was inert to 1O2. Comparatively, CoFe2O4@MnO2 had better catalytic stability and water matrix adaptability than MnO2@CoFe2O4 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.