Chelating magnetic nanocomposite for the rapid removal of Pb(ii) ions from aqueous solutions: characterization, kinetic, isotherm and thermodynamic studies

In this study, a Fe₃O₄@GMA-AAm magnetic nanocomposite was synthesized as a novel adsorbent with a suitable core-shell structure, high adsorption capacity (158.73 mg g⁻¹), easy separation and rapid adsorption rate. For this purpose, Fe₃O₄ NPs were first reacted with 3-aminopropyltriethoxysilane for the preparation of MNPs-NH₂. Then the MNPs-NH₂ was allowed to react with glycidylmethacrylate to form Fe₃O₄-GMA. Finally Fe₃O₄@GMA-AAm was synthesized by grafting polyacrylamide onto the Fe₃O₄-GMA using a radical polymerization process. The morphology and characteristics of the adsorbent were examined by various techniques such as FT-IR, TEM, SEM, XRD, AFM, TGA, EDX, EMA and VSM analysis. The synthesized adsorbent was used for the removal of Pb²⁺ ions from aqueous media and the effect of different parameters (pH, adsorbed dosage, temperature, etc.) was investigated. The isotherm analysis indicated that the adsorption experimental data fitted very well with the Langmuir isotherm model. Two kinetics equations were used to describe the adsorption rate. The result showed that the pseudo-second-order model had a better fit with the experimental data, so the chemical adsorption was the rate controlling step of the adsorption process. The thermodynamic parameters for adsorption of Pb²⁺ ions onto the Fe₃O₄@GMA-AAm adsorbent showed that the adsorption was endothermic in nature and spontaneous.