Lanthanum hydroxide modified magnetic bone biochar for enhanced phosphate removal: Performance and mechanism...

This study innovatively converted waste bovine bone into magnetic porous biochar (BBC) through ZnCl₂-activated pyrolysis, followed by one-step ball-milling co-loading of Fe₃O₄ and La compounds to synthesize La(OH)₃-, La₂(CO₃)₃-, and La₂O₃-modified adsorbents (marked as LH@MBC, LC@MBC, LO@MBC). The optimized LH@MBC achieved an unprecedented phosphate adsorption capacity of 557.4 mg/g, significantly exceeding LC@MBC (63.9 mg/g) and LO@MBC (48.7 mg/g), with rapid equilibrium within 90 min and robust tolerance to coexisting anions (Cl^-, NO₃^-, SO₄^2-, and CO₃^2-). Characterization confirmed phosphate removal via inner-sphere LaOP complexation, electrostatic attraction, and ligand exchange. Notably, LH@MBC exhibited high saturation magnetization (14.04 emu/g) for easy magnetic recovery and retained 73.2% capacity after 2 regeneration cycles, demonstrating superior potential for real wastewater treatment. This research presented a sustainable approach for simultaneous waste valorization and phosphate resource recovery via synergistic ball-milling modification.