Design and characterize ion-imprinted smart polymers from carboxymethyl chitosan for selective removal of cadmium (II) ions

Ion-imprinted polymers (IIPs) selectively extract target metal ions using ion-matched functional cavities, which can capture the target metal ion among other interfering metal ions with similar physical and chemical properties. This work developed polymers containing memory sites for cadmium ions for extraction from aqueous solutions using ion-imprinted polymer (IIP) technology. The ability of chitosan to bind to target cadmium (II) ions was enhanced by modifying it to carboxymethyl chitosan and using the latter as the polymer matrix, acetic acid solution as the porogen solvent, and glutaraldehyde as the cross-linking agent. The analytical efficiency of IIP adsorption of cadmium ions in aqueous solutions was studied, and the selectivity of the IIP for cadmium ions in a mixture of heavy metal ions was studied. Crosslinking was performed in the presence of cadmium ions for IIPs and in the absence of cadmium ions for non-imprinted polymers (NIPs). IIPs offer advantages such as ease of preparation, consistent hole size, polymer structure stability, environmental stability, and strong presentability. Infrared spectroscopy was utilized to evaluate carboxymethyl chitosan, IIP, and NIP, and X-ray diffraction was employed to investigate the crystalline properties. The polymers were examined using scanning electron microscopy (SEM) to characterize the surface properties of the IIP. The effect of time and pH on sample loading was investigated. IIP has excellent loading capacity for cadmium ions and high selectivity for Cd²⁺ when other competing ions such as Pb²⁺, Ni²⁺, and Cu²⁺ are present. Chitosan and NIP were non-selective.