In-situ Synthesis of Acid-Resistant Composites for Highly Selective Rare Earth Element Separation

Project Overview

Rare earth elements (REEs) are critical components for some of the key clean energy technologies that power the nation's transition to clean energy future. Unfortunately, the supply of these materials is far from assured with the majority of the deposits being abroad and/or controlled by hostile foreign interests. Thus, increasing the efficiency and volume of domestic supply is critical for the nation's energy security and its clean energy future. One of the major obstacles on this path is the low efficiency of the current REE separation strategies and lack of new technologies that deliver enhanced REE separations.

The objective of this project was to test the feasibility of synthesizing a new composite material that combines a sophisticated porous material (MOF) with the nanostructured electrically-conductive membrane material (MXene) that would enable high efficiency electric field-assisted adsorption/desorption based REE separation. We synthesized this composite material and evaluated its performance with respect to the concentration and the pH of the feed solution and achieved a Eu/Dy selectivity of 3.52 at pH 2.05 which falls short of the prediction posed in this feasibility study. However, this selectivity is higher than most of the reported literature values and significant considering the importance of these particular REEs in clean energy technologies. We also see a clear increase in the adsorption capacity of the composite material with the application of the electric field which is enabled by the conductive MXene layer. Moreover, ~80-95% adsorbed ion recovery was achieved during the desorption process by applying a reverse (positive) voltage to the composite membrane system which emphasizes the importance of the electrically active system for REE adsorption/recovery.

Mission Impact

This project supports the Lawrence Livermore National Laboratory mission of Climate and Energy Security. Results enable the design of new selective REE separation materials that will lead to increased domestic critical materials supply that will ultimately provide greater production of energy efficient devices (solar panels and wind turbines). Additionally, the increased REE production will create a global strategic advantage to bolster technological competition which aligns our project with the mission of Multi-Domain Deterrence.