Lignin-derived biochar to support CoFe2O4: Effective activation of peracetic acid for sulfamethoxazole degradation

The conversion of biomass wastes to highly efficient biochar-based catalysts has attracted more and more attention because it meets the environmental protection concept of waste recycling. In this work, a novel magnetic catalyst (CoFe2O4@BC) was developed by using alkaline lignin, the dominant by-products of papermaking industry, as feedstock for biochar. More importantly, PAA (CH3C(=O) OOH) was successfully activated by CoFe2O4@BC nanoparticles for sulfamethoxazole (SMX) elimination. The catalytic activity of CoFe2O4@BC on PAA activation was systematically studied. When PAA was 825 μM and CoFe2O4@BC was 100 mg/L, 10 mg/L SMX could be completely degraded. The cycle of Co3+/Co2+ of CoFe2O4@BC prompted the generation of acetyl(per)oxyl groups (CH3C(O)O• and CH3C(O)OO•), which were believed to be the dominant reactive substances for SMX degradation. The degradation of SMX was promoted under near-neutral pH conditions, and was inhibited when humic acid and HCO3− were added, while the Cl− showed a negligible influence. According to the analysis of oxidation products, three main transformation pathways of SMX were illustrated. The remarkable stability and magnetic separability of CoFe2O4@BC make it have a wider application prospect in the treatment of various wastewater.