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Öğe Affinity microspheres and their application to lysozynia adsorption: Cibacron Blue F3GA and Cu(II) with poly(HEMA-EGDMA)(John Wiley and Sons Ltd, 1999) Denizli, Fatma; Denizli, Adil; Arıca, M. YakupLysozyme adsorption onto Cibacron Blue F3GA attached and Cu(II) incorporated poly(2-hydroxyethyl methacrylate-ethylene glycol dimethacrylate) [poly(HEMA-EGDMA)] microspheres was investigated. The microspheres were prepared by suspension polymerization. Various amounts of Cibacron Blue F3GA were attached covalently onto the microspheres by changing the initial concentration of dye in the reaction medium. The microspheres with a swelling ratio of 65%, and carrying different amounts of dye (between 1.4 and 22.5?mol/g-1) were used in the lysozyme adsorption studies. Lysozyme adsorption on these microspheres from aqueous solutions containing different amounts of lysozyme at different pH values was investigated in batch reactors. The lysozyme adsorption capacity of the dye-metal chelated microspheres (238.2mgg-1) was greater than that of the dye-attached microspheres (175.1mgg-1). The maximum lyzozyme adsorption capacities (qm) and the dissociation constant (kd) values were found to be 204.9mgg-1 and 0.0715mgml-1 with dye-attached and 270.7mgg-1 and 0.0583mgml-1 with dye-metal chelated microspheres, respectively. More than 90% of the adsorbed lysozyme were desorbed in 60 min in the desorption medium containing 0.5M KSCN at pH 8.0 or 25mM EDTA at pH 4.9. © 1999 Society of Chemical Industry.Öğe Biosorption of mercury on magnetically modified yeast cells(Elsevier Science Bv, 2006) Yavuz, Handan; Denizli, Adil; Güngüneş, Hakan; Safarikova, Mirka; Safarik, IvoBrewer's yeast (bottom yeast, Saccharomyces cerevisiae subsp. uvarum) cells were magnetically modified using water based magnetic fluid stabilized perchloric acid. The magnetically modified yeast cells were characterized by scanning electron microscopy (SEM) and electron spin resonance (ESR). Hg2+ biosorption-desorption properties of magnetically modified yeast cells from synthetic solutions were utilized in batch system. The biosorption process was fast; 80% of biosorption occured within 60 min and equilibrium was achieved at around 90 min. The maximum Hg2+ biosorption capacity was obtained to be 114.6 mg/g at 35 degrees C. The suitability of the Langmuir, Freundlich and Redlich-Peterson adsorption models to the equilibrium data was investigated for mercury-biosorbent system. The results were well fitted to the Langmuir isotherm. The applicability of two kinetic models including pseudo-first order and pseudo-second order model was estimated on the basis of comparative analysis of the corresponding rate parameters, equilibrium capacity and correlation coefficients. Results suggest that chemisorption processes could be the rate-limiting step in the biosorption process. The yeast biomass can be easily regenerated by 0.1 M HNO3 with higher effectiveness. Biosorption of heavy metal ions from artificial wastewater was also studied. The biosorption capacities are 29.9 mg/g for Cu2+, 76.2 mg/g for Hg2+, 14.1 mg/g for Ni2+ and 11.8 mg/g for Zn2+. (c) 2006 Elsevier B.V. All rights reserved.Öğe Concanavalin a immobilized affinity adsorbents for reversible use in yeast invertase adsorption(Wiley-V C H Verlag Gmbh, 2004) Yavuz, Handan; Akgöl, Sinan; Arıca, Yakup; Denizli, AdilConcanavalin A (Con A) immobilized poly(2-hydroxyethyl methacrylate) (PHEMA) beads were investigated for specific adsorption of yeast invertase from aqueous solutions. PHEMA beads were prepared by a suspension polymerization technique with an average size of 150-200 mum, and activated by epichlorohydrin. Con A was then immobilized by covalent binding onto these beads. The maximum Con A immobilization was found to be 10 mg/g. The invertase-loading capability of the PHEMA/Con A beads was observed at pH 5.0. The values of the Michaelis constant K-m of invertase were significanly larger upon adsorption, indicating decreased smaller for the adsorbed invertase. Adsorption improved the pH stability of the enzyme activity was found to be quite stable in repeated experiments.Öğe Metal-chelating properties of poly(2-hydroxyethyl methacrylate-methacryloylamidohistidine) membranes(John Wiley & Sons Inc, 2005) Denizli, Adil; Bektaş, Sema; Arıca, Yakup; Genç, ÖmerMetal-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.
