Phd Degree / Doktora
Permanent URI for this collectionhttps://hdl.handle.net/11147/2869
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Doctoral Thesis Removal of Dyes and Antibiotics by Adsorption and Photocatalytic Degradation Using Zn-Based Composites(01. Izmir Institute of Technology, 2023) Saygı, Gizem; Çakıcıoğlu Özkan, Seher FehimeIn this study, the ZIF-8 was synthesized and immobilized on the clinoptilolite surface (ZIF8@CLN) and doped with Ag nanoparticles, forming the Ag-ZIF8 and Ag-ZIF8@CLN composite materials. The characterization results indicated that the ZIF-8 was well-deposited on the clinoptilolite surface and doped successfully with Ag nanoparticles. The adsorption and photocatalytic activity of these adsorbents/catalysts were evaluated by the removal of the organic pollutants such as dyes and antibiotics. The target dyes were cationic Methylene blue (MB), anionic Methyl orange (MO) and Congo red (CR), and zwitterionic Rhodamine B (RhB). The target antibiotic was tetracycline (TC). The influence of various parameters on removal was investigated using different initial pH, photocatalyst amount, pollutant concentrations and ionic strength. The results showed that ZIF-8 and ZIF-8@CLN are excellent adsorbents. However, the photocatalytic activity of Ag-ZIF8 and especially Ag-ZIF8@CLN composites were much better than ZIF-8 and ZIF-8@CLN for degradation of all dyes. The Ag-ZIF8 and Ag-ZIF8@CLN composite catalysts exhibited more than 90% removal capacity under UV irradiation for 120 min with the dye concentration of 25 mg L-1 at the optimum pHs of each dye. The enhanced adsorption and photocatalytic performance of the composite photocatalysts was attributed to the synergistic effect between the ZIF-8, CLN and Ag. The adsorption data were evaluated by considering adsorption isotherms, kinetics and thermodynamics using target dyes and antibiotics. Proposed photodegradation mechanism of the dyes over Ag-ZIF8@CLN was explained detailed. This work introduced the ZIF-8-based composite photocatalysts with high efficiency, and may provide to prefer these catalysts in photocatalytic field.Doctoral Thesis Heat and Mass Transfer Characteristics of Adsorbents in Heat Pump and Refrigerator(01. Izmir Institute of Technology, 2023) Gündoğan, Şefika Çağla; Çakıcıoğlu Özkan, Seher FehimeDue to increasing drought, pandemic and climate crisis in recent years, researchers have increased their studies on environmentally friendly energy use. Although there are technological developments in the production of energy from renewable energy sources, the storage of this produced energy is still a problem that awaits a solution. At this point, adsorption heat pumps with high primary energy efficiency come to the fore as a developing technology and attract the attention of researchers. However, low heat transfer properties in the adsorbent bed reduce the performance of adsorption heat pumps and limit their applications. The aim of this thesis was to improve the performance of the adsorption heat pump by increasing the effective thermal conductivity within the adsorbent bed. Two methods have been employed to enhance the effective thermal conductivity. In the first method, which was unconsolidated adsorbent bed design, it was aimed to increase the thermal conductivity of the bed with metal additives with a continuous structure. In the second method, which is known as consolidated bed design, the effective thermal conductivity of zeolite 13X was tried to be enhance with a high conductive material, reduced graphene oxide. In the experimental studies, it was observed that the thermal conductivity increased from 0.12 W/m.K to 0.28 W/m.K in unconsolidated bed design by means of fin-shaped metal additive. In consolidated adsorbent bed design, the effective thermal conductivity of the Graphene/Zeolite 13X (1 wt% Graphene) was determined as 0.1613 W/m.K. In theoretical studies, the effect of thermal conductivity in the temperature, pressure and adsorbate concentration was investigated. The indirect and direct effects of effective thermal conductivity on specific cooling/heating power (SCP/SHP) and coefficient of performance (COP) values were examined. Although the effect of thermal conductivity on COP was ignored in most of the studies in the literature, it was observed that COP increased from 0.01 to 0.10 when thermal conductivity increased from 0.12 W/m.K to 1 W/m.K.Doctoral Thesis Preparation of Tyrosinase Immobilized Chitosan and Gelatin Films for Detection of Parathion-Methyl(Izmir Institute of Technology, 2012) Polatoğlu, İlker; Çakıcıoğlu Özkan, Seher FehimeIn this work, tyrosinase immobilized chitosan and gelatin films as optical enzyme sensors which were characterized and optimized by UV spectrophotometer, were developed for detection of the pesticide parathion-methyl. The results show that the best sensor was the chitosan supported ones (TCA) prepared by adsorption method due to higher responsiveness and higher catalytic activity. The prepared sensors used for 10 times without significant loss in activity indicate good operational stability. Immobilization of the enzyme to chitosan support increases the pH, temperature and storage stability with respect to free enzyme due to providing structural rigidity and appropriate flexibility by immobilization. The other indication is that, isopropyl alcohol is the most appropriate organic solvent to solve the pesticide due to showing higher solubility for parathion-methyl and lowest inhibition (decrease in activity) for the enzyme. TCA has wide linear detection range and it can detect the parathion methyl concentration below the Maximum Residue Limit (MRL). The decrease in enzyme activity was obtained up to 10 mg/l (ppm) parathion-methyl concentration. The other result is that, kinetics of the immobilized enzyme was reaction controlled for higher substrate concentrations as understood from effectiveness factor, η. Atomic force microscopy (AFM) and FTIR analysis show that tyrosinase enzyme was successfully coated on the surface of chitosan and gelatin films. After using the optical enzyme sensor the binding of product o-quinone to chitosan and gelatin films were observed which was characterized by AFM results and the UV visible absorption peaks.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 FehimeLi+, 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.