Characterization of Modified Mechanically Activated Cassava Starch Magnetic Porous Microspheres and Its Adsorption for Cd(II) Ions

The magnetic polymer microsphere is a promising adsorbent due to its high adsorption efficiency and good regeneration ability from wastewater. Cassava starch magnetic porous microspheres (AAM-MSMPMs) were synthesized by graft copolymerization in inverse emulsion. Mechanically activated cassava starch (MS) was used to graft skeletons, vinyl monomers [acrylic acid (AA) and acrylamide (AM)] as copolymerized unsaturated monomers, methyl methacrylate (MMA) as the dispersing agent, and polyethylene glycol/methanol (PEG2000/MeOH) as the porogen. It was found that the AAM-MSMPM adsorbent is superparamagnetic, the saturation magnetization is 14.9 emuGreek ano teleiag(-1), and it can be rapidly and directionally separated from Cd(II) ions in aqueous solution. The FTIR indicated that the carboxyl and hydroxyl groups were grafted into MS. The AAM-MSMPM had good speroidization and a uniform size. After the porogen was added, the particle size of the AAM-MSMPM decreased from 19.00 to 7.00 nm, and the specific surface area increased from 7.00 to 35.00 m(2)Greek ano teleiag(-1). The pore volume increased from 0.03 to 0.13 cm(3)Greek ano teleiag(-1). The AAM-MSMPM exhibited a large specific surface area and provided more adsorption active sites for Cd(II) ions. The maximum adsorption capacity of the AAM-MSMPM for Cd(II) ions was 210.68 mg center dot g(-1), i.e., 81.02% higher than that without porogen. Additionally, the Cd(II) ion adsorption process on the AAM-MSMPM can be described by Langmuir isothermal and pseudo-second-order kinetic models. A chemical reaction dominated the Cd(II) ion adsorption process on the AAM-MSMPM, and chemisorption was the rate-controlling step during the Cd(II) ion adsorption process. The AAM-MSMPM still had excellent stability after five consecutive reuses.

Automated summary

The synthesis of cassava starch magnetic porous microspheres (AAM-MSMPMs) was accomplished through graft copolymerization in inverse emulsion. The resulting AAM-MSMPM adsorbent exhibited superparamagnetic behavior and demonstrated a high capacity for the adsorption of Cd(II) ions in aqueous solution. The addition of a porogen resulted in a decrease in particle size, an increase in specific surface area, and an enhancement in adsorption capacity. The adsorption process on the AAM-MSMPM followed Langmuir isothermal and pseudo-second-order kinetic models, with chemisorption as the rate-controlling step. The AAM-MSMPM also displayed excellent stability after multiple reuses.