Phd Degree / Doktora

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

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Subject: search.filters.subject.Zeolites

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Now showing 1 - 5 of 5
  • Doctoral Thesis
    Adsorptive Characteristics of Aflatoxin B1 in the Presence of Purified Clinoptilolite Rich Mineral and Lactobacillus Plantarum S2
    (Izmir Institute of Technology, 2012) Bulut Albayrak, Çisem; Ülkü, Semra
    The human diet contains a wide variety of natural carcinogens. Aflatoxin B1 (afB1) is the most toxic and most prevalent compound. Both probiotic lactic acid bacteria and clinoptilolite rich zeolite mineral have potential to eliminate this toxin. This study was planned in order to investigate adsorptive characteristics of afB1 by local purified clinoptilolite rich mineral (PNZ) and probiotic strains which were isolated from different natural sources (fermented cabbage, boza ) in the present work. PNZ and isolated strains were characterized by using several physical, chemical and biological techniques. Adsorption characteristics of both probiotic lactobacilli and PNZ were investigated in simulated gastrointestinal solutions. The chosen probiotic strain was identified as L. plantarum .The studies indicated that, both L. plantarum S2 and PNZ can eliminate afB1 in the phosphate buffer solution. They are more effective when they were used together (45% for L. plantarum S2, 32% for PNZ, 86%for L. plantarum S2 and PNZ together). AfB1 adsorption equilibrium data were best represented by Sips isotherm model for PNZ, whereas by Langmuir isotherm model for L. plantarum S2. Thermodynamic studies implied that afB1 adsorption by mineral and L. plantarum S2 was physical adsorption. Experiments with different temperatures showed that afB1 adsorption by PNZ was exothermic but afB1 adsorption by lactobacilli was endothermic. Adsorption kinetics were analysed by diffusional models and reaction models for afB1 adsorption by PNZ mineral. Both film diffusion and /or intra particle diffusion were effective on adsorption kinetics depending on the experimental conditions (Temperature, pH, agitation speed, etc).
  • 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.
  • Doctoral Thesis
    Inhibition of Microbial Ss-Glucuronidase by Natural Zeolites and Their Effects on Cancer Prevention in Human Intestinal Systems
    (Izmir Institute of Technology, 2010) Demirbüker Kavak, Dilek; Ülkü, Semra
    Bacterial β-glucuronidase (GUS) enzyme has an important role in the production of reactive metabolites related to some diseases and cancer development. In this thesis, health promoting role of clinoptilolite rich zeolite mineral was proposed to act as a potential inhibitor and as adsorbant of GUS and also to have cytotoxic effect towards cancer cells. Therefore inhibition and adsorption mechanism of GUS by clinoptilolite rich mineral and its cytotoxicity towards cancer cells were investigated. Additionally, another potential inhibitor; casein and their interactions with GUS and clinoptilolite rich mineral were revealed. Results showed that GUS activity was inhibited by either casein or clinoptilolite rich mineral and both of them acted as mixed type inhibitors. Additionally, it was found that clinoptilolite rich mineral was a potential adsorbent for GUS. Results showed that removal percentages of proteins were 9.4-54.4 % and 36.5-77.3 % for GUS and casein, respectively and depended on their initial concentrations. Equilibrium studies showed that both adsorptions were exothermic and physical and kinetic models implied that external fluid film or skin resistance, and intraparticle diffusion might be effective for GUS and casein adsorption, respectively. In cytotoxicity tests, clinoptilolite rich mineral (25mg/ml) inhibited approximately 50 % of the Caco-2 cell proliferation. This high inhibition was not observed for MCF-7 cells where inhibition was found to be 20-30 %. Flow cytometric results for both cell lines indicated that total apoptosis percentage in overall population was low compared to control sample. This result was also confirmed by cell cycle analyses.