Abstract

The development of new lithium permselective membranes for lithium recovery, in particular, when this recovery is coupled with LiOH production in a single membrane electrolysis device, is an important challenge. Two series of modified Nafion-based membranes were produced. The CEM-1 series was obtained by co-deposition polydopamine (PDA) and polyethylenimine (PEI); the CEM-2 series was prepared in a similar way, however, it differed by the addition of Mil-53-Al as metal organic framework. Modifications were made at different PDA/PEI concentrations and different time of preparation. Diffusion permeability, transport number, area resistance and conductivity of modified and pristine Nafion 117 membranes were determined. It was observed that PDA/PEI modifying layer increases membrane resistance, but the presence of Mil-53-Al reduces resistance. Two modified samples and the pristine Nafion 117 membrane were tested in membrane electrolysis process. It was found that at high current density (2650 A m-2) one of the samples (CEM-1-B) has manifested permselectivity towards Li+: the Li+/Mn+ separation factor of this sample was 30 % higher than that of Nafion 117 for Mn+ = Mg2+, Ca2+ and Na+. The lithium purity of the obtained LiOH was 97.8 % for CEM-1-B versus 97.3 % for pristine Nafion 117.