Selective lithium extraction from salt-lake brine using LATP-incorporated cellulose membranes in electrically driven systems

Abstract

The extraction of lithium (Li*) from salt-lake brine has gained increasing attention owing to the abundance of Li* resources. However, low Li* concentrations and the presence of high levels of impurity ions have rendered the extraction process challenging. This study introduces a Li*-selective membrane composed of Li1.3Al0.3Ti1.7(PO4)3 (LATP) incorporated into a cellulose acetate (CA) matrix, employed within an electrically-driven system. The membrane demonstrated high ionic conductivity (0.677 mScm-1 at 300 K) and a low activation energy (0.15 eV) for Li*, outperforming competing ions such as K*, Na*, Mg2*, and Ca2*. In binary solution tests, the membrane achieved Li* fluxes of up to 64.3 mmolm-2h-1 and a selectivity of 39.4 for Li*/Mg2*. In simulated salt-lake brine experiments, a low current (-200 mu A) was found to be more effective for Li* separation, with the highest selectivity observed at 467.3 for Li*/Mg2*. Additionally, a two-step extraction process was designed to further remove competing ions, successfully reducing the initial concentrations of Na*, K*, Mg2*, and Ca2* from 6430, 1084, 619, and 45 ppm to 0.3, 15.2, 0.2, and 0.4 ppm in the permeate, respectively. The highest selectivity achieved in this process was 543.6 for Li*/Na*. These findings indicate that the LATP/CA membrane is a promising Li*-selective membrane for electrically driven systems, contributing to more sustainable Li extraction processes.