Solid-phase extraction and separation of heavy rare earths from chloride media using P227-impregnated resins

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, pHequilibrium–lgD 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 pHequilibrium–lgD 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 βLu/Yb, βYb/Tm, βTm/Er, and βEr/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.