One-pot synthesis of MnFe2O4 functionalized magnetic biochar by the sol-gel pyrolysis method for diclofenac sodium removal

Magnetic biochar adsorbents often suffer from the uneven distribution and shedding problems of nanoparticles. In this study, a one-pot sol-gel pyrolysis method was proposed to synthesize a MnFe2O4 functionalized magnetic sawdust-based biochar (MnFe2O4@SBC) for efficient removal of diclofenac sodium (DCF). The MnFe2O4@SBC was characterized by XRD, Raman, VSM, TG-DSC, SEM, TEM, BET, FTIR and XPS. The results demonstrated that the combination of sol-gel and sawdust effectively led to a homogeneous distribution of MnFe2O4 on biochar and the MnFe2O4@SBC possessed a much richer pore structure and functional groups than the original biochar. A systematic comparison of MnFe2O4@SBC with commercial activated carbon (CAC) was conducted by analyzing the effects of initial pH, adsorbent dosage, coexisting ions, contact time and temperature on their adsorption performance. Based on the adsorption isotherm study, the maximum adsorption capacity of MnFe2O4@SBC was predicted to be 352.17 mg/g, which was almost 3.5 times that of CAC. Selectivity adsorption study and real water-based removal experiment further demonstrated the satisfactory adsorption selectivity and applicability of MnFe2O4@SBC for DCF. This study reveals that the one-pot sol-gel pyrolysis is a promising method for synthesizing excellent magnetic biochar adsorbents.