Master Degree / Yüksek Lisans Tezleri

Permanent URI for this collectionhttps://hdl.handle.net/11147/3008

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Author: search.filters.author.Alsoy Altınkaya, SacideSubject: search.filters.subject.Membranes (Technology)

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Now showing 1 - 3 of 3
  • Master Thesis
    Development of Nanofiltration Membranes Through Surface Modification of Polysulfone Based Ultrafiltration Membranes
    (Izmir Institute of Technology, 2017) Bar, Canbike; Alsoy Altınkaya, Sacide
    Stimuli responsive membranes have been used for suppressing fouling and regulating selectivity in different applications. These types of membranes are usually manufactured in thin film composite structure by either polymerizing stimuli-responsive monomer or coating stimuli-responsive polymer on a support. Responsiveness is due to their characteristic features which rely on reversible changes in mass transfer and interfacial properties as a result of changes in external environment such as pH, temperature and ionic strength. In this study, a pentablock copolymer (PBC) which consists of temperature responsive Pluronic F127 (PEO-b-PPO-b-PEO) in the middle block and pH responsive poly(N,N-(diethylamino)ethyl methacrylate) (PDEAEM) in the end blocks was used for designing a new type of thin film composite (TFC) nanofiltration membrane. The support of the composite membrane was prepared from a blend of polysulfone/sulfonated polyethersulfone using nonsolvent induced phase separation and the PBC was attached to the support via electrostatic interaction. The conformation of grafted PBC chains was determined by adsorption studies. The effects of PDEAEM block length, concentration of the copolymer and adsorption time on the adsorbed amount were investigated. Among three copolymer samples investigated (15, 20 and 25 kDa), the 25 kDa PBC displayed the highest responsiveness, thus, rejection properties were determined for the membranes prepared only from this sample. The influences of operation pH and temperature on the structure integrity of the membrane were investigated with pure water permeability measurements and the change in pore size was assessed by determining rejection of neutral solutes by the membranes. The membranes were further characterized with SEM, AFM, contact angle, XPS and zeta potential measurements. It was demonstrated that a new pH and temperature responsive, high flux TFC NF membrane was manufactured.
  • Master Thesis
    Measurement and Modeling of Thermodynamic and Kinetic Data of Membrane Forming Systems
    (Izmir Institute of Technology, 2007) Arslan, Mine Özge; Alsoy Altınkaya, Sacide
    Phase inversion process involving a ternary system (nonsolvent/solvent/ polymer) isfrequently used to prepare porous and asymmetric polymeric membranes. The thermodynamic and kinetic data for the ternary system are required to understand membrane formation mechanisms, change the preparation conditions and predict the final structure of the membranes. In this study, cloud point curves for polysulfone (PSf)/1-methyl-2-pyrrolidinone (NMP)/water, PSf/tetrahydrofurane (THF)/water, PSf/NMP/ethanol, PSf/THF/ethanol, polymethyl methacrylate (PMMA)/acetone/water, PMMA/ THF/water, PMMA/acetone/formamide and PMMA/THF/formamide systems were measured by titrating polymer solutions with nonsolvents until the onset of turbidity.Binodal curves were calculated by using the Flory Huggins theory with constant interactionparameters. Theoretical ternary phase diagrams were found to be in good agreement with experimental cloud point data. In addition to liquid liquid equilibrium data, sorptionisotherms and diffusion coefficients of water, ethanol and chloroform were measured byusing a magnetic suspension balance. Results of kinetic studies have shown that water sorption in PSf films exhibits Fickian diffusion while anomalous diffusion is observed for ethanol and chloroform sorption. The kinetic data for water sorption was analyzed using a simple Fickian diffusion model to determine the diffusion coefficients. On the other hand, anamalous sorption kinetics were interpreted by a mathematical model involving independent contributions from Fickian diffusion and polymer relaxations. The model successfully fits non-Fickian anomalies including sorption overshoot and allows to determine diffusion coefficients and relaxation times. Diffusivities of penetrants in PSf was found to decrease in the following order: Water > Chloroform > Ethanol. Equilibrium sorption isotherms of ethanol and chloroform are well described by classical Flory Huggins thermodynamic theory with constant interaction parameters. A modified version of this theory for concentration dependent interaction parameter is used to correlate the sorption isotherm of water. Vrentas Duda free volume theory is able to correlate diffusivity data of water collected at 30 C and 40 C while the theory fails to correlate the diffusivities of ethanol and chloroform both of which were determined from diffusion-relaxation model.
  • Master Thesis
    Preparation and Characterization of Hemodialysis Membranes
    (Izmir Institute of Technology, 2007) Yaşar Mahlıçlı, Filiz; Alsoy Altınkaya, Sacide
    Hemodialysis is a widely used clinical therapy for end-stage renal failure and dialysis membranes are vital components of a hemodialysis unit. The most desirable properties of a hemodialysis membrane are high mass transfer of toxic solutes to reduce the dialysis time, blood compatibility and limited protein adsorption capacity. Protein adsorption or deposition on the surface or in its pores results in a progressive decline in flux, change of selectivity of the membrane and the activation of different defense systems in blood. To prepare hemodialysis membranes with improved transport properties and protein adsorption resistant surfaces, an enzyme immobilization technique was used. Asymmetric cellulose acetate membranes were prepared through dry phase inversion method and they were modified by blending urease enzyme directly into the casting solution. The effect of enzyme immobilization on the protein adsorption, solute transport rates and mechanical properties was investigated through static adsorption and permeation experiments, mechanical tests and structural characterization by scanning electron microscope. It was found that the solute permeation rates decreased exponentially while the maximum tensile strength of the membranes increased significantly by increasing the cellulose acetate (CA) to acetone weight fraction ratio in the membrane forming solution due to a change in the structure from porous to dense one. Modification of the CA membrane with urease immobilization increased the permeation coefficients of creatinine and uric acid by a factor of 1.2 and 1.7, respectively. Similarly, the % removal of urea from the donor compartment in 1 hour increased from 45.8% to 53.2% by using urease immobilized CA membrane. The protein adsorption capacity of the urease immobilized CA membrane was found to be 2 times lower than that of the regular CA membrane. Protein fouling on the membranes caused a decrease in the transport rates of all solutes. Due to protein fouling, the decrease in the permeation coefficients of creatinine and uric acid are 59.0% and 76.5%, respectively, through regular CA membranes. On the other hand, urease immobilization limited the decrease in the permeation rates by 39.2% and 33.4% for creatinine and uric acid, respectively. In a similar way, the rate of removal of urea through CA membrane and urease immobilized CA membrane decreased by 31.2% and 11.7%, respectively. While urease immobilization decreased the protein adsorption capacity, it did not cause any loss in mechanical strength of the membrane. These results indicate that urease immobilization can be used to improve transport properties and reduce protein adsorption capacity of the CA membranes. Urease immobilized CA membranes prepared in this study can be used as an alternative membrane in hemodialysis units.