Selective Recovery of Lithium from Salt Lake Brine by Using Ion-Imprinted Polymers
Ziyi Cao, Dagang Qi, Xueting Liu, Zhiyong Zhou, Chencan Du, Zhongqi Ren
Abstract
In this study, a novel lithium ion-imprinted polymer [Li(I)-IIP] was synthesized through bulk polymerization using Li + as the template, acrylic acid as the monomer, calix[4]arene as the ligand, ethylene glycol dimethacrylate as the cross-linker, and 2,2′-azobis(isobutyronitrile) as the initiator. Li(I)-IIPs were characterized by an infrared spectrometer, solid-state 13 C nuclear magnetic resonance, X-ray photoelectron spectrometer, scanning electron microscope, thermogravimetric analysis, and zeta potential and used to selectively adsorb Li + from aqueous solutions. The Li(I)-IIPs achieved adsorption equilibrium within 25 min at pH 10, exhibiting a maximum adsorption capacity of 28.52 mg/g for Li +, while the nonionic imprinted polymers (Li(I)-NIPs) displayed a maximum adsorption capacity of 22.82 mg/g. The isothermal adsorption model and adsorption kinetic model were determined, and the adsorption process of Li(I)-IIPs was found to follow Freundlich isothermal adsorption model and pseudo-second-order kinetic model. In addition, the adsorption selectivity for the binary mixtures of Li + /Rb +, Li + /Na +, and Li + /K + and the cyclic stability of Li(I)-IIPs were investigated. The selectivity coefficients for Li + /Rb +, Li + /Na +, and Li + /K +, were 1.427, 2.476, and 1.582, respectively. After 10 adsorption–desorption cycles, the adsorption capacity of the polymers decreased by 12.14%. The excellent selective adsorption performance and recyclability of Li(I)-IIPs make them promising for the separation of Li + from salt lake brines.