Two-Step Preparation of an Amidoxime-Functionalized Chelating Resin for Removal of Heavy Metal Ions from Aqueous Solution

A novel amidoxime-functionalized chelating resin (PAO-g-PS) was prepared through a two-step method. First, poly (acrylonitrile) was grafted onto chloromethylated polystyrene beads via surface-initiated atom transfer radical polymerization, and then the nitrile group was converted to the amidoxime group by reaction with hydroxylamine. Fourier transform infrared spectrometry and X-ray photoelectron spectroscopy were used to characterize the structure of the resin. The adsorption properties were evaluated with Fe(III), Cr(III), Cd(II), and Pb(II). The maximum adsorption capacities obtained by experiment with Fe(III), Cr(III), Cd(II), and Pb(II) were 3.48, 2.54, 1.33, and 0.89 mmol g–1, respectively. By studying the effects of pH on adsorption, it was found that the adsorption of metal ions was mainly achieved by chelation interaction. The adsorption process conformed to the quasi-second-order dynamic equation. The thermodynamic study of adsorption suggested that the adsorption of PAO-g-PS resins for heavy metal ions was an entropy-driven endothermic chemisorption process. The adsorption of PAO-g-PS for heavy metal ions is selective, hardly affected by common coexisting ions such as Na(I), K(I), Ca(II), and Mg(II). The adsorption–desorption cycle indicated that the resin had good reusability and stability. All of these results indicated that the PAO-g-PS resins were suitable for efficient removal of metal ions from aqueous solution.