(705f) Deep Eutectic Solvents and Ionic Liquids for Extraction of Rare Earth Elements from Coal Ash

Authors: 
Roth, E. - Presenter, National Energy Technology Laboratory
Granite, E. J. - Presenter, U.S. Department of Energy, National Energy Technology Laboratory

Deep eutectic solvents (DESs) are a relatively new class of ionic liquids (IL) that differ from traditional

ionic liquids by mixing a hydrogen bond donor with a salt. One of the first deep eutectic solvents studied in

depth was a 2:1 mixture of urea and choline chloride. An interesting property of this DES is its ability to

dissolve metal oxides. The low volatility, inexpensive starting materials and ability to dissolve metal oxides

could make deep eutectic solvents an interesting solvent for recovery of rare earth elements (REEs).

Additionally, ionic liquids alone also have many interesting solvent properties and could provide a novel

separation method for the recovery of REEs from many solid fossil fuel sources specifically coal ash. However,

some ionic liquids are potentially very expensive, and would need to be cycled many times for an economical

extraction process.

This study reports preliminary data on the total amount of rare earth elements extracted from a sample of

coal ash using a DES (choline chloride and urea) and an ionic liquid. Specifically, an ionic liquid with a

reactive carboxylic group was synthesized and studied. The percentage of each REE extracted is reported and

measured using Inductively Coupled Plasma Mass Spectrometry (ICP-MS). The viscosity and percentage of

water, which are known to affect the kinetics of dissolution, will also be reported. Other parameters that are

also important to consider are contact time, reactor configuration, extraction temperature, ratio of solvent to coal

ash, stirring speed (mixing), pH, and the recovery of REEs from the solvent (regeneration of solvent), will also

be discussed.