Selective extraction of lithium ions by phosphoroxy-functionalized ionogels from the mother liquor of Li2CO3

Functionalized ionic liquids (FILs), as novel extractants, offer a promising way for the effective separation of Li+, but are limited by their high viscosity which increases the mass transfer resistance and hinders their practical application in industry. To overcome the above problem, this work develops a phosphoroxy-functionalized ionogels (PFIG) with a high specific surface area, hydroxyl-rich groups and porous structure, which was formed by introducing highly hydrophilic [N4444][DEHP] into a silica gel substrate via the sol-gel method. The PFIG can take advantage of the beneficial properties of each component, including the nature of the solid carrier and the Li+ selective extraction ability of [N4444][DEHP]. The high extraction rate of Li+ up to 80.4 % was attained when the content of [N4444][DEHP] in the PFIG composite was 7 mL, which may be due to the strong chelation between [N4444][DEHP] and Li+ and the excellent hydrophilicity of the substrate to increase the mass transfer. Moreover, the competitive extraction experiments indicated that PFIG-7 had excellent high selectivity. Therefore, PFIG-7 has great potential application for lithium recovery from the mother liquor of Li2CO3.