Functionalization of hierarchical porous carbon materials for adsorption of light rare earth ions

Abstract

Hierarchical porous carbon modified with multiple carbonyl ligands (HPC-1) was synthesized for the selective extraction of light rare earth elements. The material was fabricated through a dual-template strategy combined with KOH activation to enhance the specific surface area, followed by surface ligand modification. Structural integrity after activation and functionalization was confirmed by SEM and TEM analyses, while FTIR, XPS and TGA collectively verified the covalent bonding of carbonyl groups. Adsorption studies revealed rapid equilibrium kinetics and enhanced light rare earth element selectivity, achieving a saturation capacity of 29.11 mg g⁻¹. FTIR and XPS verified the chemical anchoring of the carbonyl ligand and the coordination mechanism with rare earths, and it was speculated that the metal ions in this system were coordinated with tridentate ligands (e.g., carbonyl and pyridine N), accompanied by physical adsorption in some of the micropores. Density functional theory (DFT) calculations of the difference in binding energies of the ligands and ions further revealed the mechanism of adsorption selectivity. Compared to conventional porous carbons, HPC-1 demonstrates superior acidic stability, reduced column backpressure, and improved reusability, effectively addressing critical challenges in solid–liquid extraction systems. The synergistic combination of hierarchical porosity and tailored surface chemistry establishes HPC-1 as a promising platform for selective light rare earth element recovery.