Nanofiltration Membrane Characterization and Application: Extracting Lithium in Lepidolite Leaching Solution

This study concerns the feasibility of extracting lithium and separating aluminum from lepidolite leaching solution by nanofiltration. Four commercial nanofiltration (NF) membranes (DK, DL, NF270, and Duracid NF) were chosen to investigate ion separation performance in simulated lepidolite leaching solution. Membranes were characterized according to FT-IR, hydrophobicity, zeta potential, morphology, thickness, pore size, and hydraulic permeability to reveal the effect of membrane properties on separation. NF membranes were investigated including the retention ratio of SO₄^2- and Li+, the separation efficiency of Li⁺/Al³⁺, and the effect of other cations (K⁺, Na⁺, Ca²⁺) on the separation of Li⁺/Al³⁺. The results show that DK membrane displayed the appropriate permeate flux and extremely high Li⁺/Al³⁺ separation efficiency with a separation factor of 471.3 compared with other NF membranes owing to its pore size, smooth membrane surface, and appropriate zeta potential. Overall, it is found that nanofiltration has a superior separation efficiency of lithium and aluminum, which may bring deep insights and open an avenue to offer a feasible strategy to extract lithium from lepidolite leaching solution in the future.