Abstract
The aim of the present work is to study the separation of lithium from salt lake brines by NF and LPRO. NF90 membrane compared to the XLE a LPRO membrane appeared more efficient for Li+ extraction due to its higher hydraulic permeability to pure water and 0.1M NaCl solution, its lower critical pressure (Pc=0), its higher selectivity between monovalent ions (40%) obtained at low operating transmembrane pressure (below 15bar) and its lower average roughness (105±10nm) decreasing the propensity to be fouled. NF90 exhibited 100% rejection of magnesium in the first step separation from brine diluted ten times as 15% for Li+, with a final separation of 85% between Mg2+/Li+. The permeability to the diluted brine is 0.7L.h−1.m−2.bar−1 usable to size full scale experiments, but the fouling mechanism has to be discovered in the future work. In a second step we have not succeeded to separate totally Li+ and Na+ in the permeate obtained before (15% of separation only between Li+ and Na+). To solve this problem, we did dialysis. We obtained a total separation between Li+ and Na+ with a diffusion flux (4.42 10−7mol.s−1.m−2 at 20°C) for NaCl 0.1M 5 times higher for NF90 vs XLE.
•Separation of Mg2+/Li+ by nanofiltration vs low pressure reverse osmosis membranes•Nanofiltration fouling by salt lake brines diluted 10 times•Dialysis with nanofiltration for a total separation Na+/Li+