Separation of yttrium from ion-adsorbed-rare-earth deposit leachates using N,N-di(2-ethylhexyl)-diglycolamic acid (HDEHDGA): Preliminary experimental and molecular dynamics simulation studies

Abstract

The separation of yttrium (Y) from heavy rare-earth elements (HREEs) is a major issue for ion-adsorbed rare-earth deposits. This study describes a new extraction system to develop efficient separation of Y from HREEs in a chloride medium using diglycolamic acid as the extractant. The extraction performance of N,N-di(2-ethylhexyl)-diglycolamic acid (HDEHDGA) for mixed REEs of an ion-adsorbed rare-earth deposit was investigated. The extraction order of the REEs in the HDEHDGA system followed a positive sequence, and the extraction behavior of Y resembled that of the middle REEs. Compared with naphthenic acid (NA) and sec-octylphenoxy acetic acid (CA12), HDEHDGA exhibited better separation performance for HREEs (Ho-Lu) and Y. The separation factors of Ho/Y, Er/Y, Tm/Y, Yb/Y, and Lu/Y in the Y-enriched solution were 4.41, 4.29, 3.77, 3.26, and 3.11, respectively. Combined slope analysis and electrospray ionization–high-resolution mass spectroscopy (ESI-HRMS) results identified cation exchange as the extraction mechanism of RE³⁺. Furthermore, the molecular dynamics simulation results provided new insights into the dynamic behaviors of Y³⁺ and Yb³⁺ extraction and revealed that the interaction of HDEHDGA with Yb³⁺ was stronger than that with Y³⁺. In addition, the loading capacity and recyclability of HDEHDGA were evaluated. This study highlights the potential of the HDEHDGA system for the separation of Y from HREEs.