Electrospun nanofiber membrane of dibenzo 14-crown-4-ether polyimide for efficient selective lithium recovery from discarded lithium-ion batteries

To meet the growing demand for lithium resources, it is ideal to develop a green and efficient approach for recovering lithium resources from discarded lithium-ion batteries. In this work, nanofiber membranes of 14-crown-4-ether polyimide (14C4PI) (Mn = 33 kDa) with the crown ether loading of 1.38 mmol g−1 in the main chain were fabricated by electrospinning and the structure of the nanofiber membrane was regulated by tuning the electrospinning parameters. The selectivity adsorption of 14C4PI nanofiber membrane was investigated in the simulated extract of discarded lithium-ion batteries. The results showed that the 14C4PI-12 nanofiber membrane with a high specific surface area of 41.27 m2/g and a diameter of 122.7 nm was successfully prepared under the operating conditions (polymer concentration of 12 wt%, voltage of 30 kV, flow speed of 1 mL h−1, tip-to-collector of 100 mm). The 14C4PI-12 nanofiber membrane displayed a high equilibrium adsorption capacity for Li+ (Qm = 40.17 mg g−1). The adsorption of Li+ onto the membrane was proven to be monolayer chemical adsorption confirmed by adsorption kinetics and isotherm models. The calculated equilibrium adsorption rate (EAR) was up to 70 % and the complex-ratio of crown ether in 14C4PI to Li+ was 1.46:1, whose theoretical value is 1:1. Meanwhile, the selective separation factor of Li+ to Na+, K+, Mn2+, Co2+, and Ni2+ were up to 52.3, 54.97, 48.82, 41.05 and 35.04, respectively, which were much higher than that obtained from other selective adsorption method reported in literatures. The density functional theory (DFT) calculations confirm that the superior selectivity of 14C4PI to Li+ is attributed to the higher Gibbs free energy change of 14C4PI-Li+ complexation (−113.99 kcal mol−1). To sum up, this work provides an efficient method to fabricate crown ether functional polymer nanofiber membrane for recycling lithium resources.