Preparation of poly(hydroxyethyl methacrylate-co-methacrylamidohistidine) beads and its design as a affinity adsorbent for Cu(II) removal from aqueous solutions

Different metal-complexing ligands carrying synthetic adsorbents have been reported in the literature for heavy metal removal. We have developed a novel and new approach to obtain high metal adsorption capacity utilizing 2-methacrylamidohistidine (MAH) as a metal-complexing ligand. MAH was synthesized by using methacrylochloride and histidine. Spherical beads with an average size of 150–200 μm were obtained by the radical suspension polymerization of MAH and 2-hydroxyethylmethacrylate (HEMA) conducted in an aqueous dispersion medium. Owing to the reasonably rough character of the bead surface, p(HEMA-co-MAH) beads had a specific surface area of 17.6 m2 g−1. Synthesized MAH monomer was characterized by NMR. p(HEMA-co-MAH) beads were characterized by swelling studies, FTIR and elemental analysis. These p(HEMA-co-MAH) affinity beads with a swelling ratio of 65%, and containing 1.6 mmol MAH g−1 were used in the adsorption/desorption of copper(II) ions from metal solutions. Adsorption equilibria was achieved in ∼2 h. The maximum adsorption of Cu(II) ions onto pHEMA was ∼0.36 mg Cu(II) g−1. The MAH incorporation significantly increased the Cu(II) adsorption capacity by chelate formation of Cu(II) ions with MAH molecules (122.7 mg Cu(II) g−1), which was observed at pH 7.0. pH significantly affected the adsorption capacity of MAH incorporated beads. The observed adsorption order under non-competitive conditions was Cu(II)>Cr(III)>Hg(II)>Pb(II)>Cd(II) in molar basis. The chelating beads can be easily regenerated by 0.1 M HNO3 with higher effectiveness. These features make p(HEMA-co-MAH) beads very good candidate for Cu(II) removal at high adsorption capacity.