Fabrication of magnetic CuFe2O4@PBC composite and efficient removal of metronidazole by the photo-Fenton process in a wide pH range

CuFe 2 O 4 -coated pretreated biochars (CuFe 2 O 4 @PBC) were synthesized for the first time via a facile method by impregnating and calcinating Cu–Fe-ethanol solution to activate H 2 O 2 for the degradation of metronidazole (MNZ) at a wide pH range. CuFe 2 O 4 @PBC samples were characterized by XRD, SEM , VSM, XPS , and BET. The results showed that CuFe 2 O 4 coating, which is evenly distributed on the surface of HNO 3 -pretreated biochar, can provide more active sites to enable CuFe 2 O 4 @PBC to be activated by visible light. The introduction of biochar by impregnating and calcinating method effectively suppressed the aggregation of CuFe 2 O 4 and maintained its high surface area and pore structure. CuFe 2 O 4 @PBC composite can be separated easily by an external magnetic field . The PBC-400CuFe sample calcined under 400 °C showed superior photo-Fenton catalytic ability in MNZ degradation at a wide pH range (pH = 3–7) and exhibited high-efficiency degradation of about 96.3% with the dosage concentration of catalyst 0.4 g/L in the presence of H 2 O 2 at pH 3.0 within 60 min. While, at pH 7.0, the PBC-400CuFe material removed 91.1% MNZ within 120 min, and the degradation efficiency was still higher than that of traditional Fenton reaction and some Fenton-like reaction. The PBC-400CuFe showed good stability. After 5 times of repeated use, its removal rate was still above 89.1%. This study confirmed that O 2 • - and h + are both important radicals, but the •OH played a key role in the visible photo/CuFe 2 O 4 @PBC- H₂O₂ system. The results indicate that CuFe 2 O 4 @PBC is highly suitable for the wastewaters with high MNZ content under mild conditions.