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 REE3+ ions at 298.15 K. Among the eluents analyzed, the most efficient recovery of REE3+ was observed with 0.1 M HCl/CaCl2.