Mechanically activated starch magnetic microspheres for Cd(II) adsorption from aqueous solution

Abstract

Magnetic starch microspheres (AAM-MSM) were synthesized via an inverse emulsion graft copolymerization by using mechanically activated cassava starch (MS) as a crude material, acrylic acid (AA) and acrylamide (AM) as graft copolymer monomers, and methyl methacrylate (MMA) as the dispersing agent and used as an adsorbent for the removal of Cd(II) ions from aqueous solution. Fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and vibrating sample magnetometry (VSM) were used to characterize the AAM-MSM adsorbent. The results indicated that AA, AM, and MMA were grafted to the MS, and the Fe 3 O 4 nanoparticles were encapsulated in the AAM-MSM adsorbent microspheres. The adsorbent exhibited a smooth surface, uniform size, and good sphericity because of the addition of the MMA and provided more adsorption sites for the Cd(II) ions. The maximum adsorption capacity of Cd(II) on the AAM-MSM was 39.98 mg·g −1 . The adsorbents were superparamagnetic, and the saturation magnetization was 16.7 A·m 2 ·kg −1 . Additionally, the adsorption isotherms and kinetics of the adsorption process were further investigated. The process of Cd(II) ions adsorbed onto the AAM-MSM could be described more favorably by the pseudo-second-order kinetic and Langmuir isothermal adsorption models, which suggested that the chemical reaction process dominated the adsorption process for the Cd(II) and chemisorption was the rate-controlling step during the Cd(II) removal process.