Bio-inspired fabrication of Ester-functionalized imprinted composite membrane for rapid and high-efficient recovery of lithium ion from seawater.

Lithium ion (Li) is one of the important sustainable resource and it's urgently demanded to develop high-selectivity and high-efficient method to extract of Li from seawater. Hence, we propose the ester-functionalized ion-imprinted membrane (IIMs) with high selectivity and stability for the rebinding and separation of Li in aqueous medium via ion imprinted technology and membrane separation technology. In this work, the hydrophilic polydimethylsiloxane membranes (PDMS) are synthesized by self-polymerization of dopamine (DA) in aqueous solution, resulting in the fabrication of dense poly-dopamine (PDA) layer on the surface of PDMS (PDMS-PDA). In view of weak bonding forces (such as hydrogen bond, ionic bond and Van der Waals' force) between traditional imprinted polymer and ligand, the ester groups are formed between modified PDMS-PDA and ligand by surface grafting. The obtained Li imprinted membranes (Li-IIMs) have a suitable cavity and high adsorption capacity toward Li which reveal a high rebinding capacity (50.872 mg g) toward Li based on ample rebinding sites and strong affinity force. The superior relative selectivity coefficients (α, α and α are 1.71, 4.56 and 3.80, respectively) can be also achieved. The selectivity factors of Li-IIMs for Na, K and Rb are estimated to be 2.52, 2.8 and 3.03 times larger than Li non-imprinted membranes (Li-NIMs), which imply the superior selectivity of Li-IIMs toward Li. The regeneration ability of Li-IIMs is observed by systematic batch experiments. In summary, it can be concluded that the rebinding capacities of Li-IIMs is slightly decrease after eluting process, owing to the Li-IIMs with outstanding stability performance. Presentation of the method pave a fine prospect for coming true the long-term use of imprinted membrane.