The hydrogel (HGs) was synthesized via free radical polymerization using Sodium alginate-g-poly(hydroxyethyl acrylamide-co–N isopropylacrylamide-co-2-Acrylamido-2-methylpropane sulfonic acid), with reactant concentrations optimized via the Taguchi method. Furthermore, a magnetic hydrogel (MHGs) was prepared by coprecipitating Fe2+ and Fe3+ ions. The study characterized the hydrogel (HGs) and the composite (MHGs) using FTIR, FESEM, TEM, VSM, XRD, TGA, AFM, and BET. The study also focused on removing Lead ions (Pb2+) from aqueous solutions. The maximum adsorption capacity was higher at 250.7 mg/g in 35 OC, and the kinetics of adsorption were found to comply with the pseudo-second order model. Moreover, the lead ions (Pb2+) uptake followed the Freundlich and Temkin isotherms. The investigation of the (Pb2+) removal at different temperatures (5,15,25, and 35 °C) showed that the adsorption process is basically of a physical type. The calculations were made for the Gibbs free energy, enthalpy, entropy, and the equilibrium constant. For this study, we chose the Response Surface Methodology RSM in conjunction with Analysis of Variance ANOVA to explore the Pb2+ adsorption as a function of temperature, Pb2+ concentration, and acidity. The results showed that with increasing pH and temperature, the adsorption efficiency increases, which follows the endothermic nature of the process. The efficiency of Pb2+ removal was checked after washing the adsorbent with hydrochloric acid, and the results were quite encouraging, even after four washes.
