Synthesis and characterization of a novel amino modified starch and its adsorption properties for Cd(II) ions from aqueous solution

A new amino modified starch (AMS) has been synthesized via grafting polymerization and ring-opening reaction using cassava starch as raw material and used as an adsorbent for the removal of Cd(II) ions from aqueous solution. The adsorbent was characterized by infrared spectroscopy (FT-IR), X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM). Batch adsorption experiments were carried out as a function of pH, adsorption time, initial Cd(II) ions concentration and temperature. Moreover, the equilibrium, thermodynamics and kinetics of the adsorption process were further investigated. It is found that the effect of pH on adsorption is visible and the optimum value is 6-7. The present adsorption system can be described more favorably by the pseudo-second-order kinetic model. The adsorption equilibrium data are correlated well with the Langmuir isotherm model. Furthermore, the adsorption is a spontaneous and endothermic process with increased entropy, and the rise of temperature will benefit the adsorption. In addition, the adsorption-desorption studies show that the AMS adsorbent can be reused almost without any loss in the adsorption capacity over three cycles.