Evaporation–Extraction Membrane Process for the Extraction of Lithium from Salt Lakes

In this paper, the process of film distillation with a porous condensing surface (FD-PCS) is studied as applied to the tasks of concentration of lithium-containing solutions. Concentration of solutions is a part of a three-stage lithium extraction cycle that includes softening of the brine by the precipitation of Ca²⁺/Mg²⁺ cations with sodium carbonate (calculated in PHREEQC) followed by an integrated system consisting of a membrane distillation unit and a crystallizer (deposition of NaCl) and membrane extraction (extraction of Li⁺). The productivity flows of the film distillation module are investigated (4.15–7.49 kg m⁻² h⁻¹ at the temperatures of heating of the evaporation surface of 60 and 80°C, respectively). The complex operation of the three-stage system is modeled in Simulink/MATLAB. The modeling of the process based on the experimental and published data shows a higher efficiency of film distillation with a porous condensing surface in comparison with membrane distillation with a porous condensing surface (4.2 kg of lithium versus 1.4 kg over two months of stationary operation of the system).