Synthesis of a cross-linked polymer using a diallylammonium monomer containing 12-crown-4 motifs for the selective extraction of lithium ions

A new diallyl amine salt monomer (I) bearing Li⁺ chelating 12-Crown-4 ether motifs [(H₂C = CHCH₂)₂NH⁺CH₂-(12-C-4) Cl⁻] was synthesized. Monomer (I) under free radical cyclopolymerization and alternate copolymerization with SO₂ afforded homo (II) and copolymer (III) in good yields. Terpolymerization of I, SO₂, and a cross-linker tetraallylhexane-1,6-diammonium chloride (IV) gave cross-linked resin V, which has been utilized as a scavenger for lithium ions from aqueous samples via the liquid‒solid technique. Optimizing a method involves adjusting multiple variables, such as pH, Li⁺ concentration, and resin dose, to achieve the best possible results. The adsorption capacity was determined using inductively coupled plasma-optical emission spectroscopy (ICP‒OES). The lithium removal study was conducted at concentrations ranging from 20 to 100 ppm. Resin V adsorbs lithium ions rapidly with excellent efficiency following second-order kinetics and fitting the Temkin and Langmuir adsorption isotherms. The resin demonstrated remarkable selectivity in adsorbing Li⁺ from its binary mixtures Li⁺/Na⁺ and Li⁺/K⁺.