Chitosan-Lignin-IM Nanocomposites for Efficient Removal of Cd(II) and Pb(II): Synthesis, Characterization, and Adsorptive Behavior

Abstract

Heavy metals like cadmium (Cd²⁺) and lead (Pb²⁺) can contaminate water and cause serious health risks. They also harm the environment. This study focused on making and testing a new nanocomposite called Chitosan-Lignin-IM. It was made by crosslinking chitosan with glutaraldehyde. Lignin was added next, followed by conjugation with 4-carboxylic imidazole using EDC/NHS. The structure and chemistry of the material were confirmed using FESEM and FT-IR. FESEM showed a uniform nanostructure. FT-IR confirmed the bonding of the functional groups. Adsorption tests showed high efficiency at pH 6–7. Over 90% of both Cd²⁺ and Pb²⁺ were removed at this range. The maximum adsorption was 142 mg/g for cadmium and 165 mg/g for lead. The material followed time-dependent uptake. It reached equilibrium in 2 to 3 hours. Swelling tests showed steady water absorption. The maximum swelling degree reached 467% after 5 hours. Viscosity tests showed shear-thinning behavior. This means it can flow easily under stress. The results show that the nanocomposite is efficient, fast, and stable in water. Its performance is better than many traditional materials. The addition of imidazole helped improve both metal binding and dispersion. This makes the material suitable for safe and practical water treatment.