Study on the Adsorption of CuFe₂O₄-Loaded Corncob Biochar for Pb(II)

A series of the magnetic CuFe₂O₄-loaded corncob biochar (CuFe₂O₄@CCBC) materials was obtained by combining the two-step impregnation of the corncob biochar with the pyrolysis of oxalate. CuFe₂O₄@CCBC and the pristine corncob biochar (CCBC) were characterized using XRD, SEM, VSM, BET, as well as pH_ZPC measurements. The results revealed that CuFe₂O₄ had a face-centered cubic crystalline phase and was homogeneously coated on the surface of CCBC. The as-prepared CuFe₂O₄@CCBC(5%) demonstrated a specific surface area of 74.98 m²·g^-1, saturation magnetization of 5.75 emu·g^-1 and pH_ZPC of 7.0. The adsorption dynamics and thermodynamic behavior of Pb(II) on CuFe₂O₄@CCBC and CCBC were investigated. The findings indicated that the pseudo-second kinetic and Langmuir equations suitably fitted the Pb(II) adsorption by CuFe₂O₄@CCBC or CCBC. At 30 °C and pH = 5.0, CuFe₂O₄@CCBC(5%) displayed an excellent performance in terms of the process rate and adsorption capacity towards Pb(II), for which the theoretical rate constant (k₂) and maximum adsorption capacity (q_m) were 7.68 × 10^-3 g·mg^-1··min^-1 and 132.10 mg·g^-1 separately, which were obviously higher than those of CCBC (4.38 × 10^-3 g·mg^-1·min^-1 and 15.66 mg·g^-1). The thermodynamic analyses exhibited that the adsorption reaction of the materials was endothermic and entropy-driven. The XPS and FTIR results revealed that the removal mechanism could be mainly attributed to the replacement of Pb²⁺ for H⁺ in Fe/Cu-OH and -COOH to form the inner surface complexes. Overall, the magnetic CuFe₂O₄-loaded biochar presents a high potential for use as an eco-friendly adsorbent to eliminate the heavy metals from the wastewater streams.