| Summary: | A series of the magnetic CuFe<sub>2</sub>O<sub>4</sub>-loaded corncob biochar (CuFe<sub>2</sub>O<sub>4</sub>@CCBC) materials was obtained by combining the two-step impregnation of the corncob biochar with the pyrolysis of oxalate. CuFe<sub>2</sub>O<sub>4</sub>@CCBC and the pristine corncob biochar (CCBC) were characterized using XRD, SEM, VSM, BET, as well as pH<sub>ZPC</sub> measurements. The results revealed that CuFe<sub>2</sub>O<sub>4</sub> had a face-centered cubic crystalline phase and was homogeneously coated on the surface of CCBC. The as-prepared CuFe<sub>2</sub>O<sub>4</sub>@CCBC(5%) demonstrated a specific surface area of 74.98 m<sup>2</sup>·g<sup>−1</sup>, saturation magnetization of 5.75 emu·g<sup>−1</sup> and pH<sub>ZPC</sub> of 7.0. The adsorption dynamics and thermodynamic behavior of Pb(II) on CuFe<sub>2</sub>O<sub>4</sub>@CCBC and CCBC were investigated. The findings indicated that the pseudo-second kinetic and Langmuir equations suitably fitted the Pb(II) adsorption by CuFe<sub>2</sub>O<sub>4</sub>@CCBC or CCBC. At 30 °C and pH = 5.0, CuFe<sub>2</sub>O<sub>4</sub>@CCBC(5%) displayed an excellent performance in terms of the process rate and adsorption capacity towards Pb(II), for which the theoretical rate constant (k<sub>2</sub>) and maximum adsorption capacity (<i>q</i><sub>m</sub>) were 7.68 × 10<sup>−3</sup> g·mg<sup>−1·</sup>·min<sup>−1</sup> and 132.10 mg·g<sup>−1</sup> separately, which were obviously higher than those of CCBC (4.38 × 10<sup>−3</sup> g·mg<sup>−1</sup>·min<sup>−1</sup> and 15.66 mg·g<sup>−1</sup>). 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 Pb<sup>2+</sup> for H<sup>+</sup> in Fe/Cu–OH and –COOH to form the inner surface complexes. Overall, the magnetic CuFe<sub>2</sub>O<sub>4</sub>-loaded biochar presents a high potential for use as an eco-friendly adsorbent to eliminate the heavy metals from the wastewater streams.
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