Yang Bin,Wu Suo-Zhi,Liu Xin-Yu,Yan Zeng-Xin,Liu Yu-Xue,Li Qi-Song,Yu Feng-Shan,Wang Jun-Lian
Abstract A solid-phase extraction resin SIRs-P227/XAD-7HP was prepared by impregnating extractant P227 onto macroporous resin XAD-7HP beads. SIRs-P227/XAD-7HP beads were characterized by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS). The adsorption kinetics, particle size effect, adsorption isotherm, pH equilibrium –lg D relationship (where D is distribution coefficient), desorption, adsorption selectivity for heavy rare earths, and impurity ions were studied. The results showed that the adsorption kinetics of Lu(III) on the SIRs-P227/XAD-7HP beads fitted the Morris–Weber model best. The adsorbance decreased as the particle size increased. The pH equilibrium –lg D relationship fitted well with a straight line, and the slope was 1.56. The experimental data fitted well with Langmuir adsorption. The calculated maximum adsorption capacity was 23.8 mg·g −1 , while the experimental datum was 22.7 mg·g −1 at the given conditions. The adsorbed Lu(III) can be easily stripped by 0.1 mol·L −1 HCl. The adsorption selectivity of SIRs-P227/XAD-7HP for heavy REs exhibited the following order: Lu > Yb > Tm > Er > Ho. The adjacent heavy rare earth (RE) separation factors β Lu/Yb , β Yb/Tm , β Tm/Er , and β Er/Ho were 1.57, 3.00, 3.03, and 2.23, respectively, at liquid/solid ratio (L/S) equal to 3:20. The adsorption selectivity for impurity ions exhibited the following order: Fe > Lu > Tm > Zn > Mg > Ca > Ho > Co > Ni > Cu > Al. Graphic abstract
Incomplete stripping and high acidity consumption were the major drawbacks for the separation of heavy rare earth elements (HREEs) by the popular extractant 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (P507). This article studied di-(2-ethylhexyl) phosphinic acid (P227) from thermodynamics and kinetics theoretical researches to cascade extraction simulations for the separation of HREEs. P227 was capable of complete stripping for HREEs with low acidity, and had high organic REE loading with clear and fast phase separation. Constant interfacial area cell with laminar flow was implemented to reveal the different kinetics mechanisms for the extraction and stripping of Lu 3+ . The multi-stages of cascade extraction simulation designed for the separation between Er 3+ /Tm 3+ could be of great significance for practical application. Corresponding products with high purity at both exits obtained successfully via the simulation. All these will provide the promising industrial applications of P227 with more fundamental data and guidance.
Ruiyi Sun,Fan Li,Yu Xie,Na Sui,Yong Li,Junlian Wang
In this study, two γ-carbon-substituted dialkylphosphinic acids—symmetrical di-(3,5,5-trimethylhexyl)phosphinic acid (P355) and unsymmetrical (2-ethylhexyl)(3,5,5-trimethylhexyl)phosphinic acid (P227-355)—were synthesized via a precise free radical addition method. Their chemical structures were fully characterized using ESI-HRMS,1H NMR,31P NMR, and FT-IR. Their middle REE extraction/separation performance, anti-emulsification behavior, and underlying mechanisms were investigated. Key results showed that P355 had better Dy saturation capacity (357.51 mg/L) and good selectivity for middle REEs (their average value ofβN + 1/N= 3.18), while P227-355 showed higher back-extraction efficiency (≈90% Dy stripping at ≥0.02 mol/L H2SO4). Methyln-pentyl ketone (MNPK) eliminated emulsification and boosted saturation capacity (324.18 mg/L Sm and 357.51 mg/L Dy for P355). Mechanistically, the extraction followed cation exchange (Sm3++ 2(HL)2↔ Sm·L3·(HL) + 3H+); MNPK formed hydrogen-bonded associates (HL·MNPK) with free extractants, slightly reducing the effective concentration of (HL)2but not altering the core cation exchange mechanism.
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