High-efficiency lithium isotope separation in an electrochemical system with 1-butyl-3-methylimidazolium dicyanamide, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and diethyl carbonate as the solvents
By Zhang, Zongliang; Murali, Arun; Sarswat, Prashant K.; Free, Michael L.
Published in Separation and Purification Technology
Separation and Purification Technology
2020
Abstract
Traditional Li isotope separation methods such as the column exchange process are environmentally hazardous because of the mercury involved. In this research, a high-efficiency Li isotope separation technique with a separation coefficient of 1.054 was developed based on the diffusion and migration of Li isotopes in various solvents. In many solutions, the difference in the diffusion coefficient is small; therefore, the separation effect is not satisfactory. However, due to their unique physical and chemical properties, ionic liquids such as 1-Butyl-3-methylimidazolium dicyanamide and 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide and some organic solvents such as diethyl carbonate show higher differences in Li isotope diffusion coefficients and mobilities, hence they can be used to achieve the efficient separation of Li isotopes. The isotope separation with four Li salts (LiBF4, LiCl, LiBr, and LiI) in the three solvents was investigated utilizing these differences. The results show that some Li salts can achieve excellent separation effect in ionic liquids and organic solvents. The corresponding model simulation results also show that the separation effect increases with the increase of the diffusion coefficient difference, and the higher separation coefficient may be realized by searching for the solvent with more differences in the Li isotope diffusion coefficients and mobilities.