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

CuFe2O4-coated pretreated biochars (CuFe2O4@PBC) were synthesized for the first time via a facile method by impregnating and calcinating Cu-Fe-ethanol solution to activate H2O2 for the degradation of metronidazole (MNZ) at a wide pH range. CuFe2O4@PBC samples were characterized by XRD, SEM, VSM, XPS, and BET. The results showed that CuFe2O4 coating, which is evenly distributed on the surface of HNO3-pretreated biochar, can provide more active sites to enable CuFe2O4@PBC to be activated by visible light. The introduction of biochar by impregnating and calcinating method effectively suppressed the aggregation of CuFe2O4 and maintained its high surface area and pore structure. CuFe2O4@PBC composite can be separated easily by an external magnetic field. The PBC-400CuFe sample calcined under 400 degrees 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 H2O2 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(center dot-) and h(+) are both important radicals, but the center dot OH played a key role in the visible photo/CuFe2O4@PBC-H2O2 system. The results indicate that CuFe2O4@PBC is highly suitable for the wastewaters with high MNZ content under mild conditions.

Automated summary

In this study, CuFe2O4-coated pretreated biochars were synthesized for the first time, showing significant degradation efficiency for metronidazole under visible light, high stability, and easy separation characteristics. The results confirm the key role of center dot OH radical in the visible photo/CuFe2O4@PBC-H2O2 system, making CuFe2O4@PBC highly suitable for wastewater treatment with high MNZ content under mild conditions.