Lithium extraction from high magnesium salt lake brine with an integrated membrane technology

• Integrated membrane system effectively separated Li + from high Mg 2+ solution. • Separation factor SF Li/Mg can reach above 15. • The Mg 2+ /Li + ratio was reduced from 30 to 1.9. • Rejection of magnesium was achieved about 95% Lithium extraction is a great challenge from the high magnesium content salt solution. In this work, an integrated polyamide tight ultrafiltration (UF) and nanofiltration (NF) membranes are systematically investigated to separate Li + from a high magnesium salt solution. Tight ultrafiltration UA001 and nanofiltration NF270 membranes in the integrated-cascade system not only increased Li + permeation to 82.5% but also enhanced the high Mg 2+ retention to 94.6% from the ternary salt solution of LiCl and MgCl 2 . The solution-diffusion transport model was also developed to calculate the real retention of Li + and Mg 2+ , under constant pressure mode. The separation efficiency SF Li/Mg for the ternary salt solution of LiCl+MgCl 2 +H 2 O was more than 15 at a constant pressure of 25 bars with an integrated membrane process, which was higher as compared to single-stage UF and NF270 membranes. Moreover, the high Mg 2+ /Li + ratio was also reduced from 30 to 1.9 in the integrated-cascade membrane process.