A novel polyvinyltetrazole-grafted resin with high capacity for adsorption of Pb(ii), Cu(ii) and Cr(iii) ions from aqueous solutions

A novel polyvinyltetrazole-grafted resin with high capacity for the adsorption of heavy metal ions was prepared via surface-initiated atom transfer radical polymerization (SI-ATRP) of acrylonitrile on chloromethylated crosslinked styrene–divinylbenzene resin and a subsequent cyano-tetrazole conversion reaction under microwave assistance. Fourier-transform infrared spectrometry and X-ray photoelectron spectroscopy were used to characterize the surface composition of the polyvinyltetrazole-grafted resin. It was found that the grafting amount of acrylonitrile increased linearly with the polymerization time, and approximately 70% of the cyano groups on the resin surface were converted to tetrazolyl groups, as estimated by elemental analysis. The maximum adsorption capacity of the resin was up to 1.52 mmol g−1 for Pb(II), 2.65 mmol g−1 for Cu(II) and 3.36 mmol g−1 for Cr(III) at pH 5.0. The effects of pH and salt concentration on the adsorption suggested that the adsorption of metal ions was governed mainly by the chelation interaction. The adsorption isotherms of the three metal ions were best described by the Langmuir model, and their adsorption kinetics followed the pseudosecond-order kinetic equation. The adsorption of the three concerned metal ions was hardly affected by common coexisting ions such as Na(I), K(I), Ca(II) and Mg(II), whereas it was slightly decreased when Fe(III) and Zn(II) coexisted in the solution, which illustrates the selective adsorption of Pb(II), Cu(II) and Cr(III) from wastewater. The resin has a good desorption rate and is reusable. In addition, the resin exhibited excellent chemical stability under strong acidic and alkaline conditions. These findings suggest that the resin could be potentially applied to the efficient removal of heavy metal ions from wastewater.