Master Degree / Yüksek Lisans Tezleri

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

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Publisher: search.filters.publisher.Izmir Institute of TechnologySubject: search.filters.subject.Membranes (Technology)

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Now showing 1 - 5 of 5
  • 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.
  • Master Thesis
    Preparation of Ultrafiltration/ Microfiltration Ceramic Composite Membranes for Biotechnology Applications
    (Izmir Institute of Technology, 2002) Erdem, İlker; Çiftçioğlu, Muhsin
    Ceramic membranes possess desirable properties for industrial separation and concentration processes where extreme conditions of heat, pH, ionic strength are present. Ceramic composite membranes consisting of a support and a thin membrane layer with finer pores were prepared in this work. Ceramic supports were prepared from fine alumina and zirconia powders by dry-pressing and slipcasting.These supports were sintered in the 1100-1200°C temperature range.These supports were dip-coated with ceramic sols prepared from zirconium propoxide and aluminium isopropoxide for the preparation of thin layers with finer pores. Average particle sizes of these sols were measured as 3-7 nm for zirconia sol and 30-40 nm for alumina sol by laser scattering technique. The dipcoated membranes were calcined in the 500-600°C temperature range. The thermal characterization of membrane layers was determined with DTA/TGA. The microstructure of the ceramic composite membranes was investigated with SEM. The clean water permeability (CWP) of membranes was tested by using deionised water in a filtration set-up. Separation experiments were performed with bovine serum albumin (BSA, Stokes diameter: 7 nm) solution and whey to determine protein separation capacity of the composite membranes. The CWP of the dry pressed alumina supports heat treated at 1100°C was found to be higher than the permeability of the slip-cast zirconia supports heat treated at 1200°C. The protein retention of the slip-cast zirconia support was detected as 60% with UVVIS spectrophotmeter analysis (Abs. at 280nm). After the modification of the support with dip-coating protein retention of 96% was achieved. Then the composite membranes were used in whey protein concentration experiments. Whey, which is a complex biological liquid, containing proteins, carbohydrate, minerals, was fed to the membrane without any clarification process. The retention of whey proteins with dry-pressed alumina support modified with 1/4 diluted zirconia sol (calcination temperature: 500°C) was found to be 96% with a permeate flux of 40 Lm-2hour-1.
  • Master Thesis
    The Use and Characterization of Composite Alumina-Titania Membranes for Gas Separation
    (Izmir Institute of Technology, 2002) Topuz, Berna; Çiftçioğlu, Muhsin
    The preparation, characterization and pure gas permeation of sol-gel derived alumina and silica membranes were investigated in this work. The effects of various parameters on sol particle size and unsupported membranes pore structure were investigated by laser light scattering particle size and N2 adsorption-desorption analysis .-alumina membranes were prepared on ZrO2 supports by successive dipping into boehmite sols. Almost proportional decreases in sol particle size and membrane pore diameter were determined with increasing acid content during the boehmite sol preparation. Increasing the H+/Al3+ mole ratio from 0.1 to 0.25 caused the hydrodynamic particle size and BJH pore size to decrease from 65 to 30 nm and 3.6 to 2.9 nm, respectively. The pore size increased from 2.8 nm to 3 nm upon increasing the calcination temperature from 500 to 600oC. Unsupported membranes were heat treated in the 200 to 1200 oC range for the characterization of the phase structure. Boehmite was the dominant phase below 500 oC, gamma being the dominant phase up to 900 oC and pure .-Al2O3 phase was obtained upon heat treatment at 1200oC. Pinhole and crack free alumina membranes about 3 .m (double layer) in thickness were observed from SEM pictures with insignificant infiltration. The CO2 permeability through the double layer .-Al2O3 membrane calcined at 600 oC was about 2.25*10-7 mol/m2.s.Pa, and had a slight pressure dependence which may indicate Knudsen Diffusion and Laminar Flow as the effective transport mechanisms. Upon the calcination of a similar double layer alumina membrane at 500oC, the CO2 permeability decreased to 1.51*10-8 mol/m2.s.Pa and was independent of pressure. Silica membranes were prepared by a sol-gel technique. These sols were prepared by acid catalysed hydrolysis and condensation of tetraethylorthosilicate in the presence of a solvent. The effects of processing parameters like the acid type and amount utilized during sol preparation, sol aging, heat treatment conditions, dipping time on the membrane pore structure and the permeation of pure gases were investigated. The supported membranes were heat treated in the 50-400 oC range. The N2 and CO2 permeabilities of silica membranes varied in the 2.2 * 10-10 . 2.7 * 10-8 mol / m2.s.Pa and 1.2*10-9 . 6.95*10-8 mol / m2.s.Pa range for single layer membranes dipped for 10 seconds into the sol. The sols became viscous and gelled in 16 hours at 50 oC. The O2 permeability increased with aging time. The optimum dipping time during processing was determined to be 10 seconds. The permeabilities of these membranes increased significantly with the sol acid content. The thickness of the silica membranes were determined to be about 2.m and significant infiltration into the support was observed from the SEM pictures.