Phd Degree / Doktora

Permanent URI for this collectionhttps://hdl.handle.net/11147/2869

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2009 - 200932010 - 20112

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Language: search.filters.language.enSubject: search.filters.subject.Zeolites--Absorption and adsorption

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Now showing 1 - 5 of 5
  • 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.
  • Doctoral Thesis
    Sorption of N2, Co2 and Ch4 on the Ultrasound Enhanced Cation Exchanged X Zeolites
    (Izmir Institute of Technology, 2011) Erten Kaya, Yasemin; Çakıcıoğlu Özkan, Seher Fehime
    Li+, Ca2+ and Ce3+ ions exchange on NaX zeolite under ultrasonic irradiation and the N2, CO2 and CH4 sorption on the zeolites obtained by using Zero Length Coulumn (ZLC) technique were studied. The kinetic and equilibrium of ion exchange were applied in the concentration range of 3-9 fold equivalent excess at 50 oC and 70 oC. The results obtained from the ultrasonic method was compared with the traditional method. Maximum exchange percent was obtained under ultrasonic irradiation as 76, 72 and 66 for Li+, Ca2+ and Ce3+ ions exchange, respectively. The kinetics of the ion exchange of Li+, Ca2+, Ce3+ ions into NaX zeolite has been investigated with models; pseudo first order, pseudo second order reaction models, intraparticle and external diffusion models. At initial, ion exchange is very fast kinetically and completed within about 15 min. After that both mechanism: intraparticle and external resistance are dominant which are proved with Biot number. The experimental conditions in zero length column are adjusted to control the adsorption under diffusion. The adsorbents selected for adsorption in ZLC have the convenient average pore diameters for CO2, N2 and CH4 adsorption. The kinetic gas selectivities, S(CO2/CH4), S(CO2/N2), S(N2/CH4) at 30 oC, 60 oC and 90 oC are lower than 5 for all the adsorbents. The lowest selectivity is obtained for NaX zeolite. The CO2 selectivity over CH4 and N2 are higher than N2 selectivity over CH4 for all the adsorbents S(CO2/CH4), S(CO2/N2) S(N2/CH4). This can be explained with the high electrostatic interaction and the low kinetic diameter of CO2 than the other gases.
  • Doctoral Thesis
    Cr (vi) Removal With Natural, Surfactant Modified and Bacteria Loaded Zeolites
    (Izmir Institute of Technology, 2011) Cansever Erdoğan, Beyhan; Ülkü, Ayşe Semra
    The objective of the study is to determine the bacteria removal performances of the local clinoptilolite rich mineral and its surfactant modified forms and to investigate potential applications of clinoptilolite rich mineral, surfactant modified clinoptilolite rich mineral and bacteria loaded forms in Cr (VI) sorption. Characterizations of clinoptilolite rich mineral and its modified forms were studied. Batch sorption experiments were performed and the effects of the parameters such as pH, initial concentration, agitation speed, particle size and temperature were investigated. Sorption kinetic data were analysed by external mass transfer, intraparticle diffusion, pseudo first and second order models. Intraparticle diffusion model results indicated that sorption of Cr (VI) on the sorbents was a multi-step process, involving external and intraparticle diffusion. Effective diffusion coefficient results implied that Cr (VI) sorption process was not solely intraparticle diffusion controlled and external film diffusion was also effective. Biot number (100-3000) results indicated that Cr (VI) sorption process was mainly controlled by intraparticle diffusion. The sorption reaction model results revealed that sorption of Cr (VI) onto sorbents was well represented by the pseudo-second order kinetic model. Sorption isotherm model results indicated that the Langmuir isotherm fitted well with the experimental data. Thermodynamic analysis, Gibbs energy change (<-20 kJ/mol), entropy change of sorption (<-0.2 kJ/mol K), enthalpy change (<-100kJ/mol) and activation energy (<40 kJ/mol) showed that sorption process was exothermic, spontaneous and physical sorption.