Effect of Impurity Ions in the Electrosorption Lithium Extraction Process: Generation and Restriction of “Selective Concentration Polarization”

Electrosorption is a promising method to extract lithium from wastewater/brine with low energy consumption and is environmentally friendly. In this work, a rocking chair electrode system of LiMn2O4/Li1–xMn2O4 was developed for the efficient extraction of lithium from a lithium-containing solution with different impurity ions. A new concept of "selective concentration polarization" was proposed to explain the effect of impurity cations on the lithium extraction process. It showed a depletion zone of Li+ and enrichment zone of impurity cations on the same side of the film electrode simultaneously, which hindered the electrosorption process of lithium in terms of steric hindrance and internal voltage. Meanwhile, by adding stirring in the source solution, the selective concentration polarization could be restricted and the lithium extraction rate was improved by 40%–60%. It also resulted in a higher current efficiency and higher separation efficiency than those with a static electric field. The order of the negative effects of cations is Mg2+ > Na+ > Ca2+ > K+. These observations might provide some experimental and theoretical reference for the process intensification in the selective electrosorption or selective membrane separation processes.