Facile synthesis and synergistic mechanism of CoFe2O4@three-dimensional graphene aerogels towards peroxymonosulfate activation for highly efficient degradation of recalcitrant organic pollutants

Magnetic CoFe2O4 is a promising heterogeneous catalyst with great separation and catalytic performance on peroxymonosulfate (PMS) activation. However, for extremely recalcitrant organic pollutants (e.g. Benzotriazole (BTA)), CoFe2O4/PMS system exhibits much low catalytic performance and high metal ion leaching. As such, CoFe2O4 supported on three-dimensional graphene aerogels (CoFe2O4@3DG) was synthesized via facile hydrothermal method. It turns out that 3DG as supporter significantly enhances specific surface area, redox activity and electron transfer of composite. The degradation rate constant in the CoFe2O4@3DG/PMS system (0.0203 min−1) is 15 times higher than that in the CoFe2O4/PMS system (0.0013 min−1). It results from synergistic activation of PMS by CoFe2O4 and 3DG to generate multiple reactive oxygen species (•OH, SO4−•, O2−• and 1O2). Particularly, high graphitization structure and low oxygen groups content of 3DG facilitate PMS adsorption on its surface and electron transfer from BTA to PMS. Ultimately, BTA is degraded into CO2, NH3 and intermediates through benzene and triazole ring-opening reactions. Moreover, CoFe2O4@3DG/PMS system displays good stability and recyclability. Therefore, this study provides a new way to improve CoFe2O4 activity for extremely recalcitrant organic pollutants degradation and new insights into synergistic activation of PMS by CoFe2O4 and 3DG, which further advances cobalt-based catalysts in heterogeneous catalysis. [Display omitted] •CoFe2O4@3DG as good PMS activator is synthesized via one-step hydrothermal process.•3DG enhances the surface area, redox activity and electron transfer of composite.•CoFe2O4 dominates the generation of •OH, SO4−• and O2−• in PMS activation.•3DG mediates non-radical pathway (electron transfer and 1O2) in PMS activation.•Three degradation pathways of BTA by ROS attacking are proposed.