Highly efficient peroxymonosulfate activation by CoFe2O4@attapulgite–biochar composites: Degradation properties and mechanism insights

Sulfate radical-based advanced oxidation processes (SR-AOPs) have been considered as a promising approach for degrading organic pollutants. Herein, CoFe2O4 anchored on attapulgite-biochar composites (CoFe2O4@ATP–BC) were synthesized by a sol-gel co-pyrolysis method and showed excellent catalytic performance, reusability and stability in activating peroxymonosulfate (PMS) for the degradation of Rhodamine B (RhB). The effects of PMS concentration, catalyst dosage, temperature, initial pH, NOM and inorganic ions on the removal of RhB were investigated. The radical quenching experiments and electron paramagnetic resonance (EPR) measurement confirmed that 1O2, O2∙− and surface-bound ∙OH and SO4∙− were major reactive oxygen species (ROS) in the RhB degradation by CoFe2O4@ATP–BC/PMS system, indicating that radical and non-radical degradation pathways were both involved. The possible catalytic mechanism of PMS by CoFe2O4@ATP–BC was proposed including the interface reaction and bulk reaction. The main degradation intermediates were identified by liquid chromatograph-mass spectrometry (LC-MS), and three possible degradation pathways of RhB were deduced accordingly. In general, the CoFe2O4@ATP–BC/PMS system provided fundamentals of theoretical and applied research to further develop supported bimetallic oxides for advanced oxidation treatment of organic wastewater.