Eco-friendly hydrogel based on carboxymethylcellulose poly (acrylic acid-co-hydroxyethyl acrylamide) (CMC-AAC-co-HEAM) for sustainable removal of Pb (II) ions from contaminated water

A hydrogel based on carboxymethylcellulose poly(acrylic acid-co-hydroxyethyl acrylamide) (CMC-AAC-co-HEAM) was synthesized via free radical polymerization and employed as an efficient adsorbent for the removal of Pb(II) ions from aqueous solutions. The influence of critical parameters, including adsorbent dosage, contact time, pH, ionic strength, and temperature, was systematically evaluated. Adsorption equilibrium was attained within 120 minutes, with a maximum uptake capacity of 39.8 mg/g. Kinetic studies demonstrated that the adsorption process was best described by the pseudo-second-order model, while isotherm analysis indicated favorable fitting to the Freundlich model, confirming multilayer adsorption on a heterogeneous surface. Thermodynamic investigations revealed that the adsorption was feasible, spontaneous, and endothermic, with negative ΔG values and a positive ΔH. Furthermore, the functional groups of the hydrogel, primarily carboxyl and hydroxyl moieties, played a central role in Pb(II) binding through electrostatic attraction and complexation. These results highlight the potential of CMC-AAC-co-HEAM hydrogel as a cost-effective and environmentally sustainable material for heavy metal remediation.