Preparation of PSf-g-BN15C5/NWF composite membrane with sponge-like pore structure for lithium isotopes adsorptive separation

Abstract

Polysulfone-graft-monoazabenzo-15-crown-5 ether (PSf-g-BN15C5) was synthesized via nucleophilic substitution reaction and used to prepare PSf-g-BN15C5/non-woven fabrics (NWF) composite membrane for lithium isotopes adsorptive separation by non-induced phase separation (NIPS). The influences of polymer concentration, additive and coagulation bath temperature on membrane properties were systematically explored. A solid–liquid dynamic extraction method was employed to investigate the lithium isotopes separation of the composite membrane. Results showed that the PSf-g-BN15C5/NWF composite membrane with a sponge-like pore structure, the porosity of 69% and the pure water flux of 1433 L/m2/h were obtained under the conditions: PSf-g-BN15C5 polymer concentration of 14 wt%, DMF as solvent and water as a non-solvent in coagulation bath at 60 °C. Moreover, it was found that the lithium isotopes equilibrium separation factor obtained from the membrane with immobilization amount (IA) of 0.81 mmol/g was up to 1.052 ± 0.002, which was much higher than that obtained from the traditional liquid–liquid extraction system of H2O-LiI/BN15C5-CHCl3 (1.007 ± 0.002) and the solid–liquid static extraction using PSf-g-BN15C5 polymer (1.014 ± 0.002) as extractant. In brief, the composite membrane has a great potential application in the development of a green-friendly adsorptive separation method for lithium isotopes.