Novel methacryloylamidophenylalanine functionalized porous chelating beads for adsorption of heavy metal ions

Abstract

The purpose of this study was to investigate in detail the adsorption performance of poly(2-hydroxyethylmethacrylate-methacryloylamidophenylalanine) [p(HEMA-MAPA)] beads. The metal-complexing comonomer MAPA was synthesized by reacting methacryloyl chloride with phenylalanine. Spherical beads with an average size of 150-200 mum were obtained by radical suspension polymerization of HEMA and MAPA, conducted in an aqueous dispersion medium. The beads had a specific surface area of 19.1 m(2)/g, and were characterized by means of swelling studies, FTIR, and elemental analysis. Beads with a swelling ratio of 68% and containing 3.2 mmol MAPA/g were used for the removal of heavy metal ions. Adsorption experiments were conducted with the MAPA-functionalized beads involving the heavy metal ions cadmium, arsenic, chromium, mercury, and lead. Metal adsorption was found to be dependent on the characteristics of the solution (i.e., medium pH and metal concentration) and the type of metals to be adsorbed. We have obtained adsorption capacities equal to 669.4 mg/g for Hg(II), 584.4 mg/g for Pb(II), 268.4 mg/g for Cd(II), 204.1 mg/g for As(III), and 115.2 mg/g for Cr(III). The adsorption capacities on molar basis were in the order of Hg(II) > Pb(II) > Cd(II) > As(III) > Cr(Ill). Adsorption of heavy metal ions from synthetic wastewater was also studied. The adsorption capacities were 24.5 mg/g for Cd(II), 16.9 mg/g for Cr(III), 144.4 mg/g for Hg(II), 90.9 mg/g for Pb(II), and 8.0 mg/g for As(III) at 0.5 mmol/l initial metal concentration. Naturally, depending on the desired goals, the beads containing metal could be regenerated for appropriate disposal. Our results suggest that p(HEMA-MAPA) beads are good metal adsorbers and have a great potential for environmental protection