REE and Aqueous Sulfate

Breakthrough in REE and aqueous sulfate chemistry simulation

The OLI MSE model predicts phase equilibria
for rare earth elements in multicomponent sulfate solutions.
Andre Anderko will present this work at the Symposium for Thermophysical Properties on 25 - 29 June 2018


As part of OLI Systems' participation in the Critical Materials Institute (CMI) and using the OLI MSE electrolyte thermodynamic framework, OLI has developed the thermodynamic parameters that predicts phase equilibria in aqueous systems containing rare earth sulfates, sulfuric acid and/or sodium sulfate. Systematic trends are revealed as a function of crystal cationic radii for the solubility of double Na-REE sulfate salts. This work is unique for this chemistry.


Significance and impact


The OLI MSE model provides a computational foundation for the recovery of REEs in the form of sparingly soluble Na-REE sulfate salts and for the optimization of  hydrometallurgical processes involving REEs. In particular, the recovery is linked with the solubility of the double salts, which reaches a minimum for Pr and increases for heavier REEs.

Details and next steps

The OLI MSE model reproduces solid solubilities, vapor-liquid equilibria, and caloric properties

This work elucidates the complex topology of solid-liquid equilibrium phase diagrams and provides the most probable prediction of the stable and metastable hydrates that form for each rare earth sulfate

Going forward, this work will be extended to REE carbonates, hydroxides, and phosphates and applied to separation processes

Phase diagram of the  Ce3(SO4)2 – H2O system

Solubilities of Na2REE2(SO4)4 systems

OLI Systems participation in the Critical Materials Institute

The Critical Materials Institute (CMI) stated mission is "to assure supply chains of materials critical to clean energy technologies—enabling innovation in U.S. manufacturing and enhancing U.S. energy security." This work is being done over the past five years by a group of 350 scientist spanning 4 USA Department of Energy National Laboratories, 7 universities and 11 industrial partners. OLI Systems is one of  the 11 industrial partners, in a key role, using the OLI MSE electrolyte thermodynamic framework to bringing essential simulation capability for the chemistries being studied by the CMI team. 

Learn more about the CMI at 


International Symposium for Thermophysical Properties

Boulder, CO on 24 - 29 June 2018
Andre Anderko will be chairing the first two sessions on Properties of Electrolyte Systems on 25 June, and will be presenting the paper below in the third session


Rare-Earth Elements in Aqueous Sulfate Systems: Thermodynamic Modeling of Binary and Multicomponent Systems in Wide Concentration Ranges

Guarav Das, PhD, Malgorzata Lencka, PhD, Ali Eslamimanesh, PhD, Peiming Wang, PhD & Andre Anderko, PhD, OLI Systems, Inc.
 Rik Riman, PhD, Rutgers University, Peter Rock, PhD, University of California Davis

A comprehensive model has been developed for calculating thermodynamic properties and phase equilibria in binary and multicomponent aqueous systems containing rare earth element sulfates. The model encompasses yttrium and all lanthanides except promethium. The model has been parameterized and verified using a database that includes solid-liquid equilibria, osmotic coefficients, enthalpies of dilution and heat capacities of solutions. The computational framework is based on the previously developed Mixed-Solvent Electrolyte (MSE) model. Phase equilibria have been accurately reproduced for binary rare earth sulfate – water systems and for ternary mixtures that additionally include sulfuric acid and/or sodium sulfate. Solid-liquid phase diagrams have been generated to provide a convenient summary of the solubility of stable and metastable hydrated solid phases. Analysis of the stability of solid hydrates reveals systematic trends within the rare earth series. Rare-earth elements can be recovered from solution in the form of sparingly soluble double sodium - rare earth – sulfate salts. It has been shown that the solubility of the double salts reaches a minimum for praseodymium and appreciably increases for heavier rare earth elements, thus making the separation via precipitation most effective for praseodymium and neodymium and less effective for heavier elements.