Gibbs Energy Minimization Model for Solvent Extraction with Application to Rare-Earths Recovery

Abstract

The emergence of technologies in which rare-earth elements provide critical functionality has increased the demand for these materials, with important implications for supply security. Recycling provides an option for mitigating supply risk and for creating economic value from the resale of recovered materials. While solvent extraction is a proven technology for rare-earth recovery and separation, its application often requires extensive trial-and-error experimentation to estimate parameter values and determine experimental design configurations. We describe a modeling strategy based on Gibbs energy minimization that incorporates parameter estimation for required thermodynamic properties as well as process design for solvent extraction and illustrate its applicability to rare earths separation. Visualization analysis during parameter estimation revealed a linear relationship between the standard enthalpies of the extractant and respective organo-metal complexes, analogous to the additivity principle for predicting molar volumes of organic compounds. Establishing this relationship reduced the size of the parameter estimation problem and yielded good agreement between model predictions and reported equilibrium extraction data, validating the property estimates for the organic phase species. Design exploration and optimization results map the space of feasible solvent extraction column configurations and identify the set of optimal design parameter values that meet recovery and purity targets.

Efficient Recovery of End-of-Life NdFeB Permanent Magnets by Selective Leaching with Deep Eutectic Solvents

“…The gap between the high industrial demand for REEs in magnets and their low relative abundance in carbonatite deposits requires new resources of these elements other than traditional REE ores . Recycling REEs from end-of-life materials generated from the production and consumption provides an option for closing the material flow loop, diversifying supply sources, and creating added economic value . However, less than 1% REEs used today are recycled, given the challenge of collecting and low efficiencies in the recycling processes. , …”

“…7 Recycling REEs from end-of-life materials generated from the production and consumption provides an option for closing the material flow loop, diversifying supply sources, and creating added economic value. 8 However, less than 1% REEs used today are recycled, given the challenge of collecting and low efficiencies in the recycling processes. 9,10 Various technologies have been developed to recover REEs from end-of-life magnets, including hydrometallurgy, electrochemistry, gas-phase extraction, membrane separation, bio-logical extraction, and pyrometallurgy.…”

A systematic analysis of the costs and environmental impacts of critical materials recovery from hybrid electric vehicle batteries in the U.S.

“…(1994b) , in which hydrochloric acid is used as a leaching agent. The solvent extraction process is based on the REE recovery process described in Iloeje et al. (2019) .…”

“…The solvent extraction process model used in this study is described in earlier work (Chukwunwike O. Iloeje et al., 2019 ), with an open-source implementation available on Github (C. O Iloeje 2019 ).…”

Solvent extraction process design using deep reinforcement learning

“…The Evaluate column routine encapsulates an iterative process for predicting equilibrium compositions via Gibbs energy minimization. [ 14,15 ] This routine comprises a three‐step process that, for each stage, (i) loads the stage input streams; (ii) minimizes Gibbs energy of the multiphase, multi‐component system to predict equilibrium compositions; and (iii) updates stage outlet streams, which subsequently become input streams for adjacent stages. The process continues until it fully populates a new vector of stage compositions, Y' .…”