| Summary: | Ion concentration polarization (ICP) is a promising mechanism for concentrating and/or separating charged molecules. This work simulates the extraction of Li<sup>+</sup> ions in a diluted high Mg<sup>2+</sup>/Li<sup>+</sup> ratio salt lake brines based on free flow ICP focusing (FF-ICPF). The model solution of diluted brine continuously flows through the system with Li<sup>+</sup> slightly concentrated and Mg<sup>2+</sup> significantly removed by ICP driven by external pressure and perpendicular electric field. In a typical case, our results showed that this system could focus Li<sup>+</sup> concentration by ~1.28 times while decreasing the Mg<sup>2+</sup>/Li<sup>+</sup> ratio by about 85% (from 40 to 5.85). Although Li<sup>+</sup> and Mg<sup>2+</sup> ions are not separated as an end product, which is preferably required by the lithium industry, this method is capable of decreasing the Mg<sup>2+</sup>/Li<sup>+</sup> ratio significantly and has great potential as a preprocessing technology for lithium extraction from salt lake brines.
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