High specific surface crown ether modified chitosan nanofiber membrane by low-temperature phase separation for efficient selective adsorption

Recently, the rapid development of new energy industry has promoted a sharp increase in the demand for lithium (Li). The adsorption method has notably contributed to the recovery of lithium. However, the poor adsorption capacity and selectivity as well as the complicated preparation process of current adsorbents hinder the development of lithium adsorption. Herein, we adopted a simple and green low-temperature phase separation method to fabricate a chitosan (CS) nanofiber membrane. The specific surface area of the prepared membrane is as high as 111.55 m(2) g(-1). Meanwhile, for the sake of high selectivity for Li+, we chose 2-(Hydroxymethyl)-12-crown 4 Ether (2H12C4) with a unique cavity structure to graft onto the surface of CS to prepare crown ether (CE) modified chitosan nanofiber membranes (CS-CE). The results show that CS-CE achieved the maximum adsorption capacity of 297 mg g(-1) from a high-concentration Li+ solution with 1000 mg L-1 at pH 7.0. In a mixed solution coexisting with other interfering metal ions, CS-CE still exhibited a strong affinity for Li+. In addition, after 5 cycle experiments, the maximum adsorption capacity of CS-CE for Li+ decreased by only 8.8%, which proves the excellent reusability of CS-CE. Overall results suggested that CS-CE can be a promising candidate for the recovery of Li+.