Lithium and magnesium separation from brines by hybrid capacitive deionization

Presented work deals with the problem of separating lithium and magnesium from brines. A similar size of ionic radius characterizes the Li+ and Mg2+; hence, separating these elements could be problematic. The hybrid capacitive deionization (HCDI) with lithium‑manganese‑titanium oxides was employed as a potential process for separating lithium and magnesium ions from aqueous solutions. During the investigation, the thermodynamics factors were determined. The enthalpy of activation, the entropy of activation and the Gibbs energy of activation for accumulation Li+ and Mg2+ by Eyring-Polanyi and energy activation by Arrhenius equations were calculated for explanation the separation phenomenon. Next, the HCDI for binary and multicomponent solutions were conducted. The critical role in achieving high βLi/Mg plays the activity coefficient of the initial feed, and the value of a voltage applied in constant voltage electric mode. With the increasing value of brines' activity coefficient, the separation factor βLi/Mg lift when the concentration of lithium ions decreases. HCDI with LMTO material adsorbed lithium ions with βLi/Mg at 2.14 and released Li+ with over 70% efficiency. The proposed HCDI process employed LMTO sorptive material could be considered a potential method for separating lithium and magnesium from lithium sources.