Preparation of Fe ₃O ₄@SiO ₂@ P(AANa- co-AM) Composites and Their Adsorption for Pb(II)

Abstract

A series of magnetic composites of sodium polyacrylate and polyacrylamide copolymer [Fe ₃O ₄@SiO ₂@P(AANa- co-AM)] were prepared. The investigation showed that the adsorption efficiency of Pb(II) was the best when the acrylamide/acrylic acid (AM/AA) mass ratio of composites was 5:5. Therefore, the composite of this ratio was selected as the adsorbent to systematically adsorb Pb(II) in aqueous solution. Static adsorption of Pb(II) to the magnetic composites in aqueous solutions was investigated by varying the solution pH and the concentration of Pb(II). The adsorption kinetics and isotherms model of Pb(II) on the Fe ₃O ₄@SiO ₂@P(AANa- co-AM) composites followed a pseudo-second-order model and the Langmuir isotherm model, respectively. When the temperatures were 298.15, 308.15, and 318.15 K, the maximum adsorption capacities of Fe ₃O ₄@SiO ₂@P(AANa- co-AM) composites were 237.53, 248.14, and 255.10 mg/g, respectively. The thermodynamic study of adsorption showed that the adsorption of Pb(II) on Fe ₃O ₄@SiO ₂@P(AANa- co-AM) composites was a spontaneous endothermic process. The X-ray photoelectron spectroscopy (XPS) analysis showed that the adsorption of Pb(II) was due to the chelation between −COO ^– and Pb(II). After four adsorption–desorption cycles, the adsorbent can still maintain a high adsorption capacity.