Phosphogypsum-Supported CoFe2O4 for Peroxymonosulfate Activation and Bisphenol AF Degradation: Performance and Mechanistic Assessment

Bisphenol AF (BPAF), a highly persistent fluorinated substitute for bisphenol A with endocrine-disrupting risks, resists conventional water treatment. To simultaneously address recalcitrant fluorinated pollutant removal and phosphogypsum (PG) valorization, we synthesized a CoFe2O4@PG composite catalyst via sol-gel using industrial PG as support, and applied it to activate peroxymonosulfate (PMS) for BPAF degradation. CoFe2O4 was successfully loaded onto PG, forming densely packed quasi-spherical aggregates. Under optimal conditions, the 10% CoFe2O4@PG/PMS system removed 99.17% of BPAF within 60 min, outperforming CoFe2O4/PMS and confirming that PG loading enhances catalytic activity. The system tolerated pH variations; Cl− had some interference, while CO32−, SO42−, and HPO42− showed limited effects. The Co(II)/Co(III) and Fe(II)/Fe(III) redox cycles play a key role in the activation of PMS to generate reactive oxygen species (ROS), with the sulfate radical (SO4•−) and singlet oxygen (1O2) being the primary reactive species. The catalyst exhibited broad pH adaptability, anti-interference, and cycling stability; after five cycles, removal decreased by only 15.48%, and metal leaching complied with Chinese national standards. This work offers a new strategy for fluorinated-pollutant remediation and PG valorization.