Literature Review on Li⁺/Na⁺ and Li⁺/K⁺ Separation Processes Compatible with Multistage MSED/NF Lithium Extraction System

Abstract

Demand for lithium, a major battery component, is increasing in the ongoing clean energy transition. To increase potential sources, lithium extraction from geothermal brines is being researched. Extracting Li⁺ from brine is difficult as there are other ions present as well. Mg²⁺ and Ca²⁺ are about the same size as Li⁺, but they can be separated out using membrane-based desalination processes like monovalent-selective electrodialysis (MSED) or nanofiltration (NF). The Lienhard Research Group has developed a multistage MSED or NF system to extract lithium from brine. This system still must address the separation of Li⁺ from Na⁺ and K⁺; this separation increases the purity of the final product.

This thesis reviews the literature on the Li⁺/Na⁺ and Li⁺/K⁺ separation processes of solvent extraction (SX) and lithium-composite membranes (LCM). SX is used today in other industrial metal separation processes and has potential in this context; LCMs are still early in technological development. SX literature reveals some promising extractants and process parameters that yield high selectivities S(Li⁺/Na⁺) & S(Li⁺/K⁺) and high lithium recovery rates. Next steps would include evaluating the desired S values, recovery rate values, and costs for the designed system and potentially experimenting with SX systems if those specifications are met.