A lithium ion-imprinted adsorbent using magnetic carbon nanospheres as a support for the selective recovery of lithium ions

A magnetic carbon-based lithium ion-imprinted material (Li+-IIP-Fe3O4@C) with a high Li+ adsorption selectivity was designed and prepared by a surface ion imprinting method, using magnetic carbon nanospheres (Fe3O4@C) as the carrier and 2-hydroxymethyl-12-crown-4 as the adsorption unit. First, Fe3O4@C was silanized by γ-methacryloxypropyltrimethoxysilane to obtain Si-Fe3O4@C which was then functionalized with methacrylic acid (MAA), followed by polymerization to obtain PMAA-Fe3O4@C with a regular morphology and a high degree of MAA grafting. Finally, 2-hydroxymethyl-12-crown-4 was grafted onto the surface of PMAA-Fe3O4@C in the presence of LiClO4 under catalysis by p-toluenesulfonic acid. This was cross-linked by ethylene glycol dimethacrylate and eluted by a HNO3 solution to obtain Li+-IIP-Fe3O4@C. The kinetic adsorption and isothermal adsorption results for this material show that the adsorption of Li+ conforms to a pseudo-second-order kinetic model and has Langmuir isotherms. The maximum adsorption capacity of Li+-IIP-Fe3O4@C for Li+ is 22.26 mg g-1 at 25°C. The selection factors of Li+ against Na+, K+ and Mg2+ are 8.06, 5.72, and 2.75, respectively. The Li+ adsorption capacity of Li+-IIP-Fe3O4@C decreases by only 8.8% after six adsorption-desorption cycles, demonstrating an excellent regeneration capability and making it very useful for lithium recovery.