Efficient enrichment and selective recovery of rare earths from sulfate leachate of ion-adsorption type rare earth ore by extraction with HPOAc

Abstract

The efficient enrichment and separation of rare earth elements (REEs) from sulfate leachates of ion-adsorption type rare earth ore (IATREO) is still a challenge. This work presents a novel extractant 2-(bis((2-ethylhexyl)oxy)phosphoryl)-2-hydroxyacetic acid (HPOAc) for the selective extraction and efficient enrichment of REEs from sulfate leachates of IATREO. HPOAc exhibits higher extraction ability for all fifteen REEs(III) than naphthenic acid (NA) at pHini = 1.56. Furthermore, it has no drawbacks of di-(2-ethylhexyl) phosphoric acid (P204) and 2-ethylhexyl phosphoric acid mono-2-ethylhexylester (P507) such as weak extraction ability towards light REEs(III) and high stripping acidity for heavy REEs(III). It has better separation performance for metal ion impurities than P204 and P507, especially for the typical impurity Al(III). Furthermore, the HPOAc system has better phase separation behavior and extraction phenomena. A simulated operation with two-stage counter-current extraction and single-stage stripping of REEs was carried out using unsaponified HPOAc. The recovery of REEs reaches 98.7 %. The concentration of REEs increases from 0.44 to 130.35 g/L, indicating a nearly 300-fold increase. Furthermore, the content of REEs increases from 77.8 wt% to 97.6 wt%. So HPOAc has the potential to selectively recover REEs from sulfate leachates of IATREO.