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    Öğe
    Metal-chelating properties of poly(2-hydroxyethyl methacrylate-methacryloylamidohistidine) membranes
    (John Wiley & Sons Inc, 2005) Denizli, Adil; Bektaş, Sema; Arıca, Yakup; Genç, Ömer
    Metal-chelating membranes have advantages as adsorbents in comparison with conventional beads because they are not compressible and they eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of poly (2-hydroxyethyl methacrylate-methacryloylamidohistidine) [poly(HEMA-MAH)] membranes for the removal of three toxic heavy-metal ions-Cd(II), Pb(II), and Hg(II)-from aquatic systems. The poly(HEMA-MAH) membranes were characterized with scanning electron microscopy and H-1-NMR spectroscopy. The adsorption capacity of the poly(HEMA-MAH) membranes for the selected heavy-metal ions from aqueous media containing different amounts of these ions (30-500 mg/L) and at different pH values (3.0-7.0) was investigated. The adsorption capacity of the membranes increased with time during the first 60 min and then leveled off toward the equilibrium adsorption. The maximum amounts of the heavy-metal ions adsorbed were 8.2, 31.5, and 23.2 mg/g for Cd(II), Pb(II), and Hg(II), respectively. The competitive adsorption of the metal ions was also studied. When the metal ions competed, the adsorbed amounts were 2.9 mg of Cd(II)/g, 14.8 mg of Pb(II)/g, and 9.4 mg of Hg(II)/g. The poly(HEMA-MAH) membranes Could be regenerated via washing with a solution of nitric acid (0.01M). The desorption ratio was as high as 97%. These membranes were suitable for repeated use for more than three adsorption/desorption cycles with negligible loss in the adsorption capacity. The stability constants for the metal-ion/2-methacryloylamidohistidine complexes were calculated to be 3.47 x 10(6), 7.75 x 10(7), and 2.01 x 10(7) L/mol for Cd(II), Pb(II), and Hg(II) ions, respectively, with the Ruzic method. (c) 2005 Wiley Periodicals, Inc.
  • [ X ]
    Öğe
    Removal of Cd(II), Hg(II), and MID ions from aqueous solution using p(HEMA/Chitosan) membranes
    (Wiley, 2007) Bayramoğlu, Gülay; Arica, M. Yakup; Bektaş, Sema
    An interpenetration network (IPN) was synthesized from 2-hydroxyethyl methacrylate (HEMA) and chitosan, p(HEMA/chitosan) via UV-initiated photo-polymerization. The selectivity to different heavy metal ions viz Cd(II), Pb(II), and Hg(II) to the IPN membrane has been investigated from aqueous solution using bare pHEMA membrane as a control system. Removal efficiency of metal ions from aqueous solution using the IPN membranes increased with increasing chitosan content and initial metal ions concentrations, and the equilibrium time was reached within 60 min. Adsorption of all the tested heavy metal ions on the IPN membranes was found to be pH dependent and maximum adsorption was obtained at pH 5.0. The maximum adsorption capacities of the IPN membrane for Cd(II), Pb(II), and Hg(II) were 0.063, 0.179, and 0.197 mmol/g membrane, respectively. The adsorption of the Cd(II), Hg(II), and Pb(II) metal ions on the bare pHEMA membrane was not significant. When the heavy metal ions were in competition, the amounts of adsorbed metal ions were found to be 0.035 mmol/g for Cd(II), 0.074 mmol/g for Hg(II), and 0.153 mmol/g for Pb(II), the IPN membrane is significantly selective for Pb(II) ions. The stability constants of IPN membrane-metal ions complexes were calculated by the method of Ruzic. The results obtained from the kinetics and isotherm studies showed that the experimental data for the removal of heavy metal ions were well described with the second-order kinetic equations and the Langmuir isotherm model. (c) 2007 Wiley Periodicals, Inc.