Phd Degree / Doktora
Permanent URI for this collectionhttps://hdl.handle.net/11147/2869
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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, SemraThe 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 Cr (vi) Removal With Natural, Surfactant Modified and Bacteria Loaded Zeolites(Izmir Institute of Technology, 2011) Cansever Erdoğan, Beyhan; Ülkü, Ayşe SemraThe 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.