Preliminary study on recovering lithium chloride from lithium-containing waters by nanofiltration

Process assessment experiment was carried out to investigate the applicability of nanofiltration (NF) for recovering lithium chloride from lithium-containing waters. A Desal-5 DL membrane element was adopted to treat diluted bittern containing lithium chloride and large concentrations of magnesium, boron and sulfate. The mass transfer and separating mechanism of the process were discussed qualitatively. It was suggested that ionic fractionations were governed by the combination of Donnan exclusion, dielectric exclusion and steric hindrance. At higher concentrations, steric hindrance became remarkable due to the formation of ion pairs, ion clusters and molecules. Experimental results showed that the DL membrane exhibited satisfactory rejection of sulfate and moderate rejection of magnesium but poor rejection of boron. For recovering lithium, DL performed economically poorly compared to electrodialysis.