Preparation of polydentate phosphonate-functionalized adsorbent for selective extraction of rare earth ions in harsh acidic solution

Abstract

Developing adsorbents capable of extracting rare earth element (REE) in harsh acidic solution is a challenging issue in the recycle of REE from secondary resources. In this work, porous polystyrene resin was facile modified with tris(2-aminoethyl)amine followed by methylenebis(phosphonic dichloride) to create a polydentate phosphonate-functionalized adsorbent for this purpose. The adsorption properties of four REE ions (Ce³⁺, Nd³⁺, Gd³⁺, and Dy³⁺) were investigated in terms of affinity constants, selectivity, and recovery. The adsorption mechanism of adsorbent for REE ions is regarded as the strong chelation interaction provided by the phosphonate ligand, which was verified by the experiments of acid and salt effects, thermodynamic and kinetic analysis. By using the diluted digest solution of a permanent magnet as model of strong acidic sample (1 mol/L HCl), the batch adsorption method generates high recovery ranging from 58.1 to 100% toward five REE ions (Y³⁺, Ce³⁺, Nd³⁺, Gd³⁺, and Dy³⁺), while the simulated continuous column bed enhances their total contents from 35.4% in the original digest solution to 88.9% in the eluent. In conclusion, the adsorbent indicates an excellent extraction ability in harsh acidic solution, and the recycle of REE using this adsorbent can predictably reduce alkali consumption to neutralize digest solution of secondary resources and improve greenness in manufacture.

Graphical Abstract