Phd Degree / Doktora

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End date: 2009Subject: search.filters.subject.Zeolites--Absorption and adsorption

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  • Doctoral Thesis
    The Effect of Microwaves on Ion Exchange in Zeolites
    (Izmir Institute of Technology, 2009) Akdeniz, Yelda; Ülkü, Semra
    Recent innovations of microwave field lead many scientists to focus on this phenomenon and it has been begun to be applied in different fields of zeolite applications. The purpose of this study is to determine the effect of microwave irradiation on ion exchange degree and on the structure of natural zeolite. The clinoptilolite rich mineral from Western Anatolia was used throughout the experiments. The ion exchange experiments were performed using AgNO3, Co.(NO3)26H2O and Cu (NO3)25/2H2O within 0.01M - 1M and 40 oC - 80 oC concentration and temperature range in conventional waterbath and microwave. Different solid and solution conditions on ion exchange degree were determined, as well. Metal exchanged minerals were characterized by using instrumental techniques. Antibacterial activity of the Agexchanged clinoptilolite against E. coli was determined by Kirby.Bauer method. The Ag +, Co2+ and Cu2+ amounts within the mineral increased with decreasing S/L while increased with increasing temperature and time. For some utilized parameters microwave treatment was effective however on the whole it did not significantly improved the degree of ion exchange compared to waterbath treatment. The inspection of XRD patterns and FTIR spectra of metal exchanged minerals confirmed that no transition of clinoptilolite phase and no shifts in peak positions occurred with exchange methods applied. The sorption processes are controlled mainly by external-phase mass transfer. Ag+, Co2+ and Cu2+ sorptions on NaCLI exhibited a good fit to Freundlich model and Langmuir models. All metal exchanged minerals showed considerable superiority against E.Coli.
  • Doctoral Thesis
    Integrated Approach To Whey Utilization Through Natural Zeolite Adsorption/ Desorption and Fermentation
    (Izmir Institute of Technology, 2009) Polat, Zelal; Ülkü, Semra
    In this thesis, the usage of clinoptilolite rich natural zeolites in the recovery of whey proteins by adsorption/desorption, and in the bioconversion of whey, lactose source, to lactic acid were investigated. The possibility for the utilization of natural zeolite deposits of Turkey; and whey, by-product of cheese manufacturing, in the production of high value added chemicals is important from both economical and environmental concerns. Natural zeolites with a particle size range of 75-150 .m were prepared and characterized. Aqueous protein solution, whey powder solution and whey were treated with the natural zeolites and dealuminated zeolites. Batch adsorption studies were performed and uptake data were collected. Equilibrium adsorption isotherms were analysed by Langmuir and Freundlich isotherms. Langmuir isotherm fits the experimental data better. Furthermore, experiments were conducted to see the effects of temperature, initial adsorbate concentration, solid/liquid ratio, agitation speed, pH, particle size and dealumination in adsorption process. The adsorption mechanism was analysed with adsorption kinetics models; and considering the effects of particle size, agitation speed and temperature external film diffusion, surface diffusion and surface reaction were found as effective. The effects of the natural zeolite on the pH, elemental composition and the adsorption tendency of the lactose-lactic acid in the fermentation media were also investigated; and the results were compared with the sythetic ones. Natural zeolites were found as an alternative inexpensive mineral source for the fermentation.
  • Doctoral Thesis
    Nitrogen Monoxide Storage and Release Properties of Local Natural Zeolite for Biological Applications
    (Izmir Institute of Technology, 2009) Narin, Güler; Ülkü, Semra; Ülkü, Semra
    In this thesis, nitrogen monoxide (nitric oxide, NO) adsorption, storage and release properties of the local clinoptilolite-rich natural zeolite and its modified forms were investigated. The zeolite particles (75-150 .m, 150-250 .m) were prepared through treatment of the natural zeolite with NaCl and consecutively with aqueous metal (Co2+, Ag+, Cu2+, Fe3+) salt solutions under different conditions. The prepared zeolites were characterized in terms of particle size and morphology, density, mineral and elemental composition, dehydration behavior, porosity, surface area, and infrared spectroscopic characteristics. The total adsorption capacities of the zeolites for NO were calculated from the breakthrough curves obtained at 30 oC on a dynamic adsorption system and found to be in the range of 5.5-8.5 mmol/g. NO was adsorbed in the zeolites reversibly and irreversibly. The total adsorption capacity was mainly contributed from the irreversible adsorption. The irreversible adsorption capacity was related to the type and amount of metal cation in the zeolite. The temperature-programmed desorption (TPD) profiles provided information about the desorption kinetics of the NO species formed on the zeolite surface upon the adsorption. The bands detected in the DRIFTS spectra upon admission of NO were assigned to reversibly and irreversibly adsorbed NO species. The unmodified and iron-sorbed zeolites gained antibacterial activity against E. coli after NO loading. The unmodified zeolite also exhibited antibacterial activity against B. subtilis after NO loading. The NO-loaded unmodified zeolite also exhibited complete bactericidal activity upon contact with both bacteria cells. The unmodified and copper-sorbed zeolites exhibited similar NO release kinetics.