Rare Earth Metal Ions Adsorption Using 2-[2-Oxo-2-(1-pyrrolidinyl)ethoxy]acetic acid/Sodium Alginate Gel

In this research, adsorbents synthesized from natural sodium alginate polymers incorporated with varying concentrations of 2-[2-oxo-2-(1-pyrrolidinyl)ethoxy]acetic acid (PYRDGA) were investigated. Analyses of adsorption properties indicated that the pristine sodium alginate gel (SAG) demonstrated adsorption capacities of 222.4, 202.6, 199.1 and 398.0 mg g −1 for La, Gd, Y, and Sc, respectively. The composite gel infused with PYRDGA at a 1:1 ratio exhibited adsorption values of 278.2, 270.6, 283.2 and 374.9 mg g −1 for the same elements. Across all synthesized gels, an optimal pH of 5 was identified for the adsorption of rare earth element (REE) 3+ ions. The introduction of the extractant PYRDGA notably reduced the gel's selectivity towards Cu, Pb, Cd, and Cr. Spectroscopic analyses highlighted the critical involvement of C=O and C–O functional groups in the adsorption mechanisms. Kinetic assessments suggested the applicability of R–P model, inferring that the rare earth ions' adsorption onto the gels could be characterized by uniform or non-uniform monolayer surface adsorption. Furthermore, thermodynamic evaluations were conducted for various gels against REE 3+ ions at 298.15 K. Among the eluents analyzed, the most efficient recovery of REE 3+ was observed with 0.1 M HCl/CaCl 2。