Activation of peroxymonosulfate by sp2-hybridized microalgae-derived carbon for ciprofloxacin degradation: Importance of pyrolysis temperature

Abstract

Microalgae can be harmful to natural water in a variety of ways, and how to deal with this problem has received much attention. Magnetic nitrogen-doped microalgae-derived carbon (Fe-N@MC) was successfully prepared by pyrolysis under different temperatures. The sp2-hybridized carbon and CO bond structure were strongly dependent on the pyrolysis temperature, and Fe-N@MC500 had a higher ratio of sp2-hybridized carbon than other counterparts. The surface morphology and structure analysis indicated that the Fe3O4 was successfully anchored into the carbon layer for magnetic separation. Ciprofloxacin (CIP) was selected as the indicator to test the catalytic performance. In the presence of peroxymonosulfate (PMS), the degradation efficiencies of nano-Fe3O4, N@MC500 and Fe-N@MC500 for CIP were 46.8%, 79.8% and 92.6% within 120 min. Under different reaction conditions (PMS dosage, pH, temperature), Fe-N@MC500 composite was shown to have superior efficiency and stability. Radical quenching experiments and electron spin resonance (ESR) indicated that singlet oxygen (1O2) was dominant in the reaction supplemented by OH and SO4−. It is believed that PMS could work as both acceptor and donor for efficient activation by sp2-hybird carbon structure and CO bond. This study successfully provides a feasible method for the synthesis of recycled Fe-N@MC with microalgae as a renewable carbon feedstock to deal with antibiotics.