Ion-imprinted chitosan prepared without cross-linking agent for efficient selective adsorption of Al(iii) from rare earth solution

Abstract

In the aqueous phase, ion-imprinted materials exhibit excellent selective adsorption properties for specific ions, but their complicated preparation process and large amount of crosslinker consumption limit their application. In this study, ion-imprinted chitosan (IIP-CS) was prepared by a simple one-step hydrothermal method without a cross-linking agent for the efficient adsorption of trace amounts of Al(III) from a rare earth solution. The structures and morphology of IIP-CS were analyzed by FT-IR, SEM, and XRD. The Al(III) adsorption characteristics of IIP-CS were investigated under various preparation processes and adsorption conditions. It was found that the optimum mass ratio of IIP-CS is 3 : 1 and pH is 3 and the adsorption capacity reaches up to 40.36 mg g⁻¹. In addition, three different isothermal models—Temkin, Freundlich, and Langmuir—were used to analyze the equilibrium adsorption of IIP-CS in aqueous solution. The results obtained are consistent with the Langmuir model. The adsorption process of Al(III) on IIP-CS follows a pseudo-secondary kinetic model, suggesting that electron sharing or exchange between IIP-CS and Al(III) is a key factor affecting its adsorption rate. IIP-CS shows high selectivity coefficients for Al(III) in mixtures of La(III), Y(III), and Gd(III), which are 792.50, 163.26, and 55.16, respectively. The mechanism of action is the formation of a complex via amidation between Al(III) and IIP-CS. IIP-CS is an adsorbent with excellent regeneration and selective adsorption performance in aqueous solution.