Synthesis and characterization of magnetic amidoximated chitosan-g poly(polyacrylonitrile)/laponite RD nanocomposites with enhanced adsorption capacity for Cu$^{2+}$

Abstract

Magnetic amidoximated nanocomposites based on a combination of chitosan and magnetic laponite RD were prepared and examined for the removal of Cu$^{2+}$ from aqueous solutions. Magnetic laponite RD was prepared by an in situ method. In order to prepare magnetic amidoximated nanocomposites, acrylonitrile was grafted to chitosan in the presence of magnetic laponite RD. Then the nitrile pendants on magnetic chitosan-g-polyacrylonitrile/laponite RD (mChtioPANLap) were converted to amidoxime groups. We developed a polyamidoximated magnetic nanocomposite based on a mixture of chitosan/laponite RD, possessing a high adsorption capacity for Cu$^{2+}$. By introducing magnetic laponite RD the adsorption capacity of nanocomposites for Cu$^{2+}$ was significantly improved. The effects of contact time, initial concentration of Cu$^{2+}$, initial pH of Cu$^{2+}$ solutions, and temperature on adsorption process were investigated. Studying adsorption kinetics showed that the experimental data are described better by the pseudo-second-order kinetic model. The adsorption of Cu$^{2+}$ on nanocomposites followed the Langmuir isotherm model well. Additionally, the fitting of isotherm data by the Dubinin-Radushkevich model showed that the adsorption process occurred by physisorption mechanism. The thermodynamic data indicated that the adsorption process was spontaneous and endothermic.