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

ABSTRACT

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-1) toward Li+ based on ample rebinding sites and strong affinity force. The superior relative selectivity coefficients (αNa/Li, αK/Li and αRb/Li 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.