Development of biochar-based magnetic adsorbent for enhanced Pb(II) ions removal.

Waster decontamination by Pb(II) is a critical issue that threatens the environmental and human health. Ferrite nanoparticles NCCF, Ni₀.₆Co₀.₁Cu₀.₃Fe₂O₄, loaded on biochar (BC) in different ratios, 0.2 and 0.5 g, are prepared using the hydrothermal technique. X-ray diffraction (XRD), FT-IR spectroscopy, surface area measurements and vibrating sample magnetometer (VSM) are carried out to study the structural, surface characterizations and magnetic properties. XRD pattern identify single phase spinel formation. Biochar has negligible effect on the ferrite crystal structure but reduces lattice strain and promotes structural ordering, mainly through defect formation rather than structural modification. FT-IR indicates that the cubic spinel type has been efficiently deposited on the biochar surface. BET analysis showed that the surface area and pore volume of ferrite are increased at lower biochar loading. VSM analysis revealed that the incorporation of biochar into the ferrite structure decreases the saturation magnetization while preserving moderate coercivity. The prepared samples are used as biosorbents for Pb(II) ions removal from aqueous solutions. Studying the effect of the solution pH revealed that the addition of biochar into the ferrite structure improves adsorption effectiveness under acidic conditions. The adsorption follows the pseudo second order kinetics, implying a chemisorption mechanism through a complexation of surface functional groups. The Freundlich model best explained the adsorption behavior, indicating heterogeneous adsorption sites. The incorporation of biochar significantly enhanced the adsorption capacity, reaching a maximum adsorption capacity of 398.4 mg g⁻¹ for NCCF/BC-0.2, which is substantially higher than those of bare NCCF and BC. In addition, the prepared composites demonstrated good regeneration ability and maintained high Pb(II) removal efficiency in the presence of competing metal ions.