Synergistic effect of PMS activation by Fe0@Fe3O4 anchored on N, S, O co-doped carbon composite for degradation of sulfamethoxazole

High efficient activator is highly desired in the field of persulfate-based advanced oxidation process. In comparison with the previous studies, this study adopted nitrogen, sulfur and oxygen co-doped carbon material to support Fe-0 encapsulate in Fe3O4 to prepare iron-based modified carbon composite (Fe-0@Fe3O4-MC) by a facile two-step pyrolysis. Fe-0@Fe3O4-MC was then used for degradation of sulfamethoxazole. The results showed that Fe-0@Fe3O4-MC had superior catalytic activity for PMS activation due to the synergistic effect of iron-based compound and modified carbon. In the presence of 0.1 g/L of Fe-0@Fe3O4-MC, SMX (0.04 mM) could be completely degraded within 120 mM at pH 3.4 and 3 mM of PMS. The SMX degradation followed pseudo first-order kinetic model, with the rate constant of 0.12 min(-1), and the mineralization of SMX achieved 48.4%. Sulfate radicals dominated in the SMX degradation. In addition to Fe-0 and Fe3O4, carbon defects, graphitic N, sulfur and FeN4 also contributed to PMS activation. Fe-0 oxidation was the rate-limiting step for PMS activation. Dissolved oxygen made a minor contribution to Fe-0 oxidation. The intermediate products of SMX degradation were identified, and two pathways of SMX degradation were proposed. The influencing factors on SMX degradation were studied, including pH, temperature, PMS concentration, Fe-0@Fe3O4-MC dosage, chloridion, carbonate and humic acids, and the influencing mechanism was discussed. This study could provide an efficient PMS activator for the degradation of emerging organic pollutants in water and wastewater.

Automated summary

This study adopted nitrogen, sulfur and oxygen co-doped carbon material to support Fe-0 encapsulate in Fe3O4 to prepare efficient iron-based modified carbon composite. The composite showed superior catalytic activity for PMS activation and successfully degraded sulfamethoxazole, with sulfate radicals dominating in the degradation process. In addition to Fe-0 and Fe3O4, carbon defects, graphitic N, sulfur and FeN4 also contributed to PMS activation.