Enhanced degradation of sulfamethoxazole in water by biochar loading and multiple free and non-free radicals cooperating in the FeS@BC/PS system.

The excessive consumption of sulfamethoxazole (SMX), a pharmaceutical antibiotic, poses significant environmental hazards. The FeS-persulfate (FeS-PS) system has been employed for SMX remediation because of its excellent performance. However, FeS tends to agglomerate and become passivated, negatively impacting its activation performance. In this study, the incorporation of FeS into biochar (BC) effectively reduced agglomeration and enhanced the catalytic performance. The PS activated by FeS@BC loaded at a mass ratio of 1:1 exhibited the highest SMX removal efficiency (92.5%). The free radicals (·OH, SO, and O) and non-free radicals (O and Fe(IV)) were identified during PS activation. The removal of SMX was found to be dependent on the contribution of ·OH, SO, O and Fe(IV), rather than O. Additionally, the presence of C-O-Fe in FeS@BC, which formed the framework of the primary battery, contributed to the enhanced degradation of SMX. The toxicity prediction results demonstrated a significant reduction in the toxicity of the transformation byproducts. Hence, the mechanism of PS activation was explored through FeS@BC, proposing novel strategies for developing advanced and efficient approaches to SMX removal.