Thermo-responsive ion imprinted polymer on the surface of magnetic carbon nanospheres for recognizing and capturing low-concentration lithium ion

Abstract

Ion imprinted polymer (IIP) on the surface of magnetic carbon nanospheres, using N-propylacrylamide and benzo-12-crown 4-ether (B12C4) as bi-functional monomers, is designed and synthesized for the selective recognition and recovery of Li+ from aqueous medium. The adsorption behaviors of Li+-IIP including adsorption kinetics, isotherms, selective recognition, and regeneration are investigated in detail by inductively coupled plasma-optical emission spectroscopy. The adsorption capacity of Li+-IIP towards Li+ reaches a maximum value of 23.46 mg g−1 at 25 ˚C within 60 min. The Langmuir and pseudo-second-order models manifest the apparent adsorption behavior dominated by single layer chemisorption. The Li+-IIP realized selective adsorption of Li+ against Na+, K+, Mg2+, Al3+, and Fe3+ in their coexistence solution. It is reused five times without a significant decrease with the assistance of externally applied magnetic field for solid/liquid separation. The recognition mechanism of Li+-IIP towards Li+ is the combined action of dehydration effect, electrostatic attraction, and size and imprinting effect, as identified by theoretical simulated calculation based on density functional theory and experimental data. The temperature-responsive adsorption of Li+-IIP towards Li+ facilitates the adsorption/desorption operations. Li+-IIP shows good separation from the treated solution by applying an external magnetic field. This work provides new insights into the recovery of lithium.