Catalytic Degradation of Ciprofloxacin in Aqueous Solution by Peroxymonosulfate Activated with a Magnetic CuFe2O4@Biochar Composite

A magnetic copper ferrite and biochar composite (CuFe₂O₄@BC) catalyst was prepared by an improved sol-gel calcination method and initially used for the removal of antibiotics ciprofloxacin (CIP) by activated peroxymonosulfate (PMS). Using CuFe₂O₄@BC as the activator, 97.8% CIP removal efficiency could be achieved in 30 min. After a continuous degradation cycle, CuFe₂O₄@BC catalyst still exhibited great stability and repeatability and could also be quickly recovered by an external magnetic field. Meanwhile, the CuFe₂O₄@BC/PMS system presented good stability for metal ion leaching, which was far less than the leaching of metal ions in the CuFe₂O₄/PMS system. Moreover, the effects of various influencing factors, such as initial solution pH, activator loading, PMS dosage, reaction temperature, humic acid (HA), and the inorganic anions were explored. The quenching experiments and the electron paramagnetic resonance (EPR) analysis manifested that hydroxyl radical (•OH), sulfate radical (SO₄^•-), superoxide radical (O₂^•-), and singlet oxygen (¹O₂) were generated in the CuFe₂O₄@BC/PMS system, while ¹O₂ and O₂^•- are mainly involved in the degradation process. The synergistic effect between CuFe₂O₄ and BC enhanced the structural stability and electrical conductivity of the material, which promoted the bonding between the catalyst and PMS, resulting in the enhanced catalytic activity of CuFe₂O₄@BC. This indicates that CuFe₂O₄@BC activating PMS is a promising remediation technique for CIP-contaminated water.