Selective Extraction of Lithium Cations from Mixture of Alkali Metal Chlorides Using Electrobaromembrane Process

The problem of low-reagent separation of Na⁺, K⁺, and Li⁺ cations is becoming increasingly important in connection with the search for new technologies for the extraction of lithium from brines and the recovery of this valuable element from already used energy sources. This paper presents the results of testing the electrobaromembrane process, in which the gradients of the electric field and pressure field are directed in opposite directions. The experiments were carried out in a laboratory flow cell, the desalting and concentration chambers of which are separated by a track-etched membrane and limited by MA-41 anion-exchange membranes. The working area of each membrane is 30 cm². The processed solution contains 70, 75, and 55 mmol/L of LiCl, KCl, and NaCl, respectively. It has been shown that at a current density of 11.7 mA/cm² and a pressure difference of 0.20 bar in the desalting circuit, it is possible to ensure an accumulation rate of Li⁺ cations equal to 0.05 mol/(m² h), and a rate of loss of Na⁺ and K⁺ cations from this circuit, equal to –0.09 and –0.25 mol/(m² h), respectively. Factors that can influence the efficiency of separation of Li⁺ and Na⁺, K⁺ are considered.