Preparation of a novel ion-imprinted membrane using sodium periodate-oxidized polydopamine as the interface adhesion layer for the direction separation of Li+ from spent lithium-ion battery leaching solution

In this paper, a novel ion-imprinted membrane (SP-IIM) was prepared by combining graft polymerization with chemical modification and from polydopamine (PDA) oxidized by sodium periodate (SP-PDA) as the interface adhesion layer. The PDA was oxidized by sodium periodate at pH 5.0, causing it to undergo extensive cross-linking within the adhesion layer to provide better chemical stability for improving the reusability of the membrane. The flaky microstructure of the SP-PDA provided more surface area for the loading of 12-Crown-4 (12C4). The optimal adsorption capacity of the SP-IIM for Li+ was 42.58 mg·g−1 after incubating the membrane in a 200 mg·L–1 solution of Li+ for 180 min. The kinetics and isotherm data of the adsorption of Li+ onto the SP-IIM were fitted to pseudo-second-order kinetics and Langmuir model, respectively. Through selective adsorption experiments, the optimal selective separation factors of Li+/Mn2+, Li+/Co2+, Li+/Ni2+ were 6.71, 5.84 and 3.03, respectively. Density functional theory (DFT) calculations were performed on the coordination of metal cations (Li+, Mn2+, Co2+, and Ni2+) by 12C4, the results of which showed that the weak binding of Li+ to 12C4, as well as the favorable dehydration of Li+, made it easier for Li+ to be coordinated by 12C4 in a multicomponent solution containing Li+, Mn2+, Co2+, and Ni2+. The oxidation of the PDA by sodium periodate caused significant intermolecular cross-linking within the SP-PDA layer to reduce the possibility of the ion-imprinted layer detaching from the membrane, thereby increasing the reusability of the SP-IIM. After five repeated adsorption–desorption cycles, the adsorption capacity of the SP-IIM only decreased by 4.6%, which indicated that the SP-IIM was highly reusable. This work improved the adsorption capacity and reusability of ion-imprinted membranes by changing the microstructure of the interface adhesion layer, which was of great significance to the further development of ion-imprinted membranes.