Magnetic polyphenol nanocomposite of Fe<sub>3</sub>O<sub>4</sub>/SiO<sub>2</sub>/PP for Cd(II) adsorption from aqueous solution
Chuang Liu, Xiaoxue Jiang, Xiaoyu Wang, Qian Wang, Lanxin Li, Fugang Zhang, Wenyan Liang
Abstract
In order to solve the water solubility and difficult re-use of plant polyphenol (PP) in Cd(II) adsorption, PP was immobilized on the surface of magnetic material in this study. A core-shell nanocomposite Fe3O4/SiO2/PP (∼18 nm) was synthesized with 3–8 nm SiO2 and 2–5 nm PP. TGA analysis revealed the PP coating amount was 2.39%. VSM detection suggested that saturation magnetization of Fe3O4/SiO2/PP was 45.94 emu/g. The adsorption equilibrium was reached in 2 h and the adsorption kinetics followed a pseudo-second-order model. The adsorption data fitted well to a Langmuir isotherm, achieving a 98.6% of Cd(II) removal at 0.6 g, pH 7.0, 298 K and 160 rpm. The adsorption capacity of Cd(II) on Fe3O4/SiO2/PP highly depended on the pH. The adsorption capacity increased as the initial solution pH was increased in the range of 3.0–8.0. The adsorbed Cd(II) on Fe3O4/SiO2/PP could be effectively desorbed by 0.1 mol/L of HNO3 and the Fe3O4/SiO2/PP still maintained a stable adsorption capacity after five cycles. The adsorption mechanism of Cd(II) on Fe3O4/SiO2/PP is mainly dependent on complexation and electrostatic adsorption from the FTIR and XPS analyses. This study provided a new way for PP to remove Cd(II) from aqueous solution.