The separation and recovery of dysprosium (Dy) and neodymium (Nd) from waste Nd magnet was investigated using a solvent-impregnated resin loaded with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester. The leaching solution obtained from the magnet contained Dy and Nd, together with a large amount of iron (Fe). Since Fe suppressed the adsorption of Dy and Nd, ascorbic acid was added to the leaching solution to reduce Fe(III) to Fe(II), enabling their selective adsorption. Although the separation of Dy and Nd was difficult using the conventional frontal separation mode in column operation, the separation was achieved in the gradient elution mode. The proposed separation and recovery process, based on a connected column system, yielded Dy with a purity of 98.9 wt% and a recovery yield of 96.9%, and Nd with a purity of 96.2 wt% and a recovery yield of 95.6%.

Vanadium is widely used in industry as a steel alloying element and catalyst. Due to the uneven distribution of vanadium resources, its recovery from spent vanadium materials has become increasingly important. In this study, we extracted vanadium (V) from acidic media, using the bifunctional ionic liquid [P₆₆₆₁₄][D2EHPA], consisting of Cyphos IL 101 ([P₆₆₆₁₄][Cl]) and bis(2-ethylhexyl)phosphoric acid (D2EHPA), as the extractant. The extractability of vanadium using this bifunctional ionic liquid was slightly higher than that using Cyphos IL 101 alone or a simple mixture of Cyphos IL 101 and D2EHPA. The species of vanadium extracted at high hydrochloric acid concentrations was ([P₆₆₆₁₄][D2EHPA])₂(HVOCl₃). The vanadium extracted in the organic phase was quantitatively recovered using 1 mol/L aqueous ammonia.

Pillararenes are a series of novel macrocyclic compounds discovered in the 2000s. However, solvent extraction based on ion exchange using pillararene derivatives is currently limited. Recently, a pillar[6]arene hexaacetic acid derivative (OctP[6]CH₂COOH) has been developed as a new acidic extractant. In this study, the extraction of amino acid esters using OctP[6]CH₂COOH was investigated. The extraction of tryptophan methyl ester using OctP[6]CH₂COOH was much greater than that using the 6-fold equivalent monomer analog. The extraction of more hydrophobic cationic guests was relatively high. This process is based on a proton exchange reaction. The results of slope analysis and Job plot analysis confirmed the formation of a 1:1 complex between OctP[6]CH₂COOH and the guest cation.

Novel phosphoric and phosphonic acid type ion exchange resins were synthesized as impregnation type resins and surface functional group type resins in the present work, and their adsorption and separation abilities for rare earth metals were investigated. The impregnation type resins were synthesized using 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC-88A) as a porogen during the synthesis of polymer beads, while the surface functional group type resins were synthesized by immobilizing the phosphoric acid ester ligand onto polymer beads. All ion exchange resins exhibited adsorption ability for dysprosium. The separation abilities for dysprosium and europium with the impregnation type resins were consistent with those with the conventional solvent-impregnated resin containing PC-88A, while almost no selectivity was obtained with the surface functional group type resins. The impregnation type resin can be applied to column operation, and the selective adsorption of dysprosium over neodymium can be achieved by combining a scrubbing method.

In this study, the ionic liquid methyl trioctylammonium di-(2-ethylhexyl) phosphate (A336P204) was prepared to extract magnesium (Mg) from brine with a high Mg/lithium (Li) ratio. The effects of the extraction time, the pH of the initial aqueous phase, the volume fraction of ionic liquid in the organic phase, and the phase ratio on the extraction efficiencies of Mg²⁺ and Li⁺ were investigated. Under the optimal conditions, the single extraction efficiencies of Mg²⁺ and Li⁺ were 90.5% and 11.5%, respectively. The stripping efficiency of Mg²⁺ reached 93.3% using 1 mol/L HCl as a stripping agent with a volume ratio of the aqueous phase to the organic phase of 2. A336P204 has good cyclic stability, indicating its high potential for Mg²⁺ extraction from Mg²⁺-rich solutions.