Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Recovery of Lithium From Aqueous System Using Manganese Oxide Adsorbent With Developed Electrospun Mat Substrate(01. Izmir Institute of Technology, 2023) Akgün, Berk; Ebil, Özgenç; Demir, Mustafa MuammerLithium is used in many fields due to its high energy density and unique electrochemical properties. Recently, there has been a strong increase in demand for lithium, so the extraction of lithium from natural water resources has become a remarkable research topic. One of the most effective methods of separating lithium from natural water sources is adsorption using lithium ion-sieve adsorbents. However, the powdered nature of the adsorbents makes them challenging to process and less recyclable. Recent studies have focused on developing adsorbents using different polymeric materials as substrates or binders. In the thesis, as a new approach, flexible and free-standing polyurethane electrospun mat substrates were produced and combined with λ-MnO2 to extract lithium from aqueous systems, and their lithium removal performance was investigated. After the fabricated mats and λ-MnO2 powder were characterized, the deposition process was performed, and filtration studies were carried out in synthetic lithium solution. Optimum conditions for lithium removal were found as an adsorbent amount of 200 mg, and 200 ppm initial [Li+], and pH 12. In addition, lithium removal performances have been improved by stacking mats and multi-stage filtration processes. Lithium removal reached 76.6% when a 400 ppm lithium solution and an 8-step filtration were used. Lithium removal experiments were performed with salt-lake brine containing high concentrations of various ions and showed that these ions reduced the lithium removal. In the study, PU electrospun mats for λ-MnO2 powder were found to be a promising substrate for lithium removal from aqueous systems.Master Thesis Valorization of Biomass for Fuel and Chemicals Production(01. Izmir Institute of Technology, 2023) Öcal, Bulutcem; Yüksel Özşen, AslıRapidly increasing global energy demand resulting from the growing population and worldwide development increased consumption of limited fossil fuel usage that causes severe environmental deterioration by CO2 emission have sparked interest in finding green, renewable, and sustainable alternative sources for energy. Bio-oil, derived by several biomass via liquefaction, is a promising candidate to replace fossil fuels. Turkey is a country, 27% of which is covered with forests (mostly oak trees). Therefore, it has great potential for cheap lignocellulosic feedstock forest residues from industrial applications and harvesting. In the present study, the thermal liquefaction of oak wood particles (OWP) was performed using various solvents besides water, such as ethanol, 1-butanol, and 1,4-dioxane. The experiments were carried out in a batch reactor for 1 and 2 h residence time at different temperatures (210oC, 240oC, and 270oC). Bio-oil samples obtained at best reaction temperature, 270oC, optimum residence time, 1 h, were analyzed with TGA, CHNS elemental analyzer, FTIR, and GC-MS. Based on energy recovery calculations, the enhancement of pristine OWP's energy efficiency depends on bio-oil yield, and quality was confirmed for all solvent types. 1,4-dioxane showed the best performance in yielding the maximum bio-oil with 51.8%. The higher heating values of the bio-oils ranged from 22.1 to 35 MJ/kg. Phenolic groups were the predominant components of bio-oil produced from OWP, while intensity of alcohols, ketones, and acids varied based on using solvents.Master Thesis Investigation of Electrochemical Co2 Capture System(Izmir Institute of Technology, 2022) Güler, Cansu; Uzunlar, ErdalFossil fuels have been used as a primary energy source for many years to meet the increasing energy demand since the industrial revolution. Fossil fuels are an important source of carbon that triggers global warming and climate change. To reduce the accumulation of carbon dioxide in the atmosphere, carbon capture has become more important. Conventional carbon capture technology is a thermally regenerated amine-based capture based on monoethanolamine (MEA). In this process, carbon dioxide is captured in an absorption column with the amine solution, and CO2-amine solution is sent to the stripping column, where the solution is heated to release the captured CO2 and regenerate the amine solution. However, an important disadvantage of this process is that it requires high energy for the CO2 release step. Recently, electrochemical CO2 capture process is proposed in the literature to decrease the energy requirement. The aim of this study is to investigate the electrochemical CO2 capture process using homopiperazine (HPZ). Unlike the conventional CO2 capture process, the CO2 release step is performed using an electrochemical cell. In the anode compartment of this electrochemical cell, the formed CO2-amine complexes are converted into amine-metal complexes from which the CO2 is released. The amine-metal complexes are then sent to the cathode, where the complex decomposes and metal deposition occurs. Laboratory-scale studies of the electrochemical capture process using MEA and HPZ as solvent were carried out. In the obtained results, it was found that HPZ has higher CO2 capture capacity and CO2 release rate than MEA and a similar CO2 absorption rate as MEA. In addition, UV-Vis spectra analyses showed that the reaction rate at the anode was much higher than the reaction rate at the cathode for both amines.Master Thesis Development of Keratin Based Hydrogel Systems(Izmir Institute of Technology, 2022) Yalçın Göl, Damla; Top, AybenIn this study, keratin proteins from Merino sheep wool were obtained via oxidative extraction (Chapter 2), sulfitolysis extraction (Chapter 3) and sulfitolysis with reductive extraction methods (Chapter 4). Keratin proteins were characterized XRD and FTIR spectroscopy and thermal analysis. In the SDS-PAGE gel results of the keratins diffusive protein bands between ~23 kDa and >170 kDa and a discrete band at about 12 kDa were observed confirming highly polydisperse nature of the protein samples. Then, keratin-based hydrogel systems were obtained via different methodologies. In Chapter 2, oxidized keratins (keratoses) were crosslinked with THPC to form keratose hydrogels. Effect of the amount of the crosslinking agent on the viscoelastic, swelling, and morphological properties of hydrogels was investigated. In Chapter 3, the keratin hydrogels were obtained via reformation of disulfide bridge and self-assembly of the keratin chains. In Chapter 4, keratins reduced with DTT were crosslinked with 2000 Da PEG-(C2H4-mal)2 and 6000 Da PEG-(C2H4-mal)2 to prepare PEG-hydrogels. Storage moduli of the hydrogels were obtained in the range of 63 ± 22 and 2613 ± 254 Pa and were shown to be tuned by the amount and chain length of the crosslinker. The highest swelling ratios were obtained for the THPC crosslinked hydrogels whereas the highest pore size was observed in PEG-keratin hydrogels. Cytocompatibility of the keratin based hydrogel systems was confirmed using L929 mouse fibroblast cells by applying CCK-8 tests. Of these hydrogels, PEG-keratin hydrogels were found to support cell proliferation with a higher rate than empty TCPS wells up to 4 days. These results demonstrate that low-cost keratin-based hydrogels can be used in a variety of biomedical applications, such as drug delivery systems for cancer therapy, and scaffolds in wound healing and soft tissue engineering.Master Thesis Devlopment of Solid Acid Catalysts for Cellulose Acetate Production(Izmir Institute of Technology, 2022) Sönmeztürk, Begüm; Yılmaz, SelahattinCellulose acetate (CA) is one of the most commercially important cellulose derivatives with a wide range of applications in various industries. As a green approach, the development of heterogeneous solid acid catalysts for cellulose acetate production is important. The objective of the present thesis is to develop active and stable mesoporous solid acid catalysts for solventless cellulose acetate production with acetic anhydride from microcrystalline cellulose. As catalyst sulfating agents, ammonium sulfate and chlorosulfonic acid (CSA) were applied. Ammonium sulfate ((NH₄)₂SO₄) sulfated catalysts are La incorporated titania-silica (SO4/La-TiO2-SiO2), sulfated titania-silica (SO4/TiO2-SiO2), and sulfated Ti-SBA-15 (SO4/Ti-SBA-15), whereas the CSA/Ti-SBA-15 catalysts were sulfated by chlorosulfonic acid. The effect of Si/Ti mole ratios (6, 10, 20) on the stability of CSA/Ti-SBA-15 catalysts was investigated. Activity and stability of the catalysts were tested in the cellulose acetylation reaction by acetic anhydride at 80 oC with a 10:1 acetic anhydride to cellulose AGU mole ratio. The effect of reaction time (2, 4, 6, and 8 h) and amount of catalyst (0.10, 0.25, and 0.5 g) on the reaction were investigated. Synthesized cellulose acetate samples were analyzed by FT-IR, 1H-NMR, and TGA. CSA/Ti-SBA-15 (10) was found to be the most active and stable catalyst with 2.84 % leaching, 89.6 % conversion, 74.6 % yield, and DS of 2.69. The activity and stability of CSA/Ti-SBA-15 (10) catalyst were further investigated after its treatment with acetone. At the end of the 3rd cycle, A-CSA/Ti-SBA-15 (10) was found as an active and stable catalyst with 58.6% cellulose conversion, 50% CA yield, DS of 2.62, and 1.68% sulfur leaching.Master Thesis An Investigation of Data-Based Fault Detection Methods in Petroleum Refineries(Izmir Institute of Technology, 2022) Yasmal, Aslı; Uzunlar, ErdalThe petroleum refineries are complex systems vital for energy and production sectors. During production, these complex systems might experience various faults, including fluid leaks in unit operations. The detection of leaks is important for a reliable, safe, and efficient operation. Among the possible leak detection mechanisms, data-based leak detection methods are promising in terms of low investment cost, less human intervention, ability to detect small leaks in advance and direct integration capability to distributed control systems. The aim of this study is to investigate data-based leak detection methods in a heat exchanger in a petroleum refinery. To that end, possible leaking problems in petroleum refineries are assessed, multiple leak cases from a real heat exchanger in a petroleum refinery are determined, literature studies are searched for appropriate data-based leak detection methods, applicability of a set of data-based leak detection methods is studied with a literature benchmark data set, and the real cases of heat exchanger leaks are studied with the determined leak detection methods. Data sets for multiple leak cases of a heat exchanger are obtained from a TUPRAS refinery. The benchmark data set is obtained from Tennessee Eastman Process (TEP). Discrete Wavelet Transform (DWT), Auto Encoder (AE), and Exponentially Weighted Moving Average (EWMA) are selected as the data-based leak detection methods. The selected data-based methods are first studied with TEP data set, and good fault detection capability is observed. Then, the real leak cases are studied. All three data-based methods are found successful in detecting the actual leak cases. For some of the cases, leaks are detected with data-based methods in advance of the operation engineers noticing the leak.Master Thesis Functionalized Cellulose-Based Adsorbent for Lithium Recoveryfrom Aqueous Solutions(01. Izmir Institute of Technology, 2021) Nampeera, Jackline; Yüksel Özşen, AslıThis study focused on generation of low-cost yet highly effective lithium selective bio-sorbent from olive pruning waste mainly olive branches. Olive branches were treated with NaOH that eliminated non-cellulosic materials and activated hydroxyl groups that inhibit the formation of active sites. Olive branches were then functionalized through homogeneous phosphorylation at 150 ⁰C. POB, NOB, and FOB samples were subjected to SEM, XRD, FTIR, BET, XPS, and TGA to observe the changes in their structure and properties. Factors affecting lithium adsorption were investigated on the synthesized FOB in a batch system and analyzed by ICP-OES. Adsorption isotherms are well fitted to the Freundlich isotherm model than the Langmuir isotherm model which exhibited a maximum adsorption capacity of 6.7 mg/g at 30 ⁰C. Kinetic studies exhibited fast kinetics and equilibrium was attained in 6 minutes while thermodynamic studies showed an exothermic, spontaneous reaction and increased randomness at the interaction interface. Regeneration studies proved the sustainability of FOB with Li+ desorption efficiency of 99.6% in 1.0 M HCl. The synthesized FOB displayed a better degree of column utilization and elution efficiency; 56.8% and 95.8% than Lewatit TP 260; 16.0% and 50.4% respectively in the adsorption column studies performed at room temperature. However, it exhibited a poor breakthrough capacity of 2.1 mg Li/ml sorbent than Lewatit TP 260 with 1.33 mg Li/ml sorbent. Based on all experimental results, the novel functionalized olive branches (FOB) proved a potential lithium selective bio-sorbent and can be applied in the recovery of lithium from its aqueous sources.Master Thesis Development of Peg and Peg-Peptide Based Drug Delivery Systems(Izmir Institute of Technology, 2016) Balcı, Beste; Top, AybenIn this study, two types of drug delivery systems (DDS) were prepared; mPEG (methoxy polyethylene glycol)-HYD (hydrazide)-DOX and mPEG-peptide-(HYD)-DOX. In the design of the conjugates, mPEG was used to increase the blood circulation time. HYD provided an acid cleavable bond between the carrier molecule and DOX, whereas peptide containing histidines imparted pH responsiveness of the molecule. Doxorubicin (DOX) was selected as a model anti-cancer drug. DDS were synthesized using two steps; hydrazide functionalization of carboxylic acid of the carrier molecule followed by DOX conjugation. Hydrazide form of the carrier molecules denoted as HYD1 and HYD2 were obtained using adipic acid dihydrazide (AADH) and carbohydrazide (CH), respectively. To increase DOX conjugation, trifluoroacetic acid (TFA) and DOX amounts were changed and the reactions were carried out at the conditions giving the highest DOX conjugation (mPEG-HYD:DOX:TFA= 2.5mg:2mg:20μL per 1 mL of DMSO). The peptide (AT1=CGGGHHHHHHGGGE) was synthesized using solid phase peptide synthesis (SPPS) and PEGylated using mPEG-maleimide to obtain mPEG-AT1 conjugate. The purity of AT1 and mPEG-AT1 were confirmed using mass spectroscopy and high performance liquid chromatography (HPLC). DOX conjugation percentages were obtained as 62 7, 60 3 and 35 + 3 for mPEG-HYD1-DOX, mPEG-HYD2-DOX and mPEG-AT1-HYD1-DOX, respectively. Drug release studies indicated modest pH responsiveness of the carrier molecules obtained using AADH. On the other hand, mPEG-HYD2-DOX released 13% of drug at the end of the 72h independent of pH. For mPEG-AT1-DOX, drug release percentage values were obtained as 15% and 30% at pH 7.4 and 5.0 respectively. Cytotoxicity of the conjugates of DDS was determined using lung cancer (A-549) cell lines. DOX equivalent IC50 values were determined as 20, 40 and 5 for mPEG-HYD1-DOX, mPEG-HYD2-DOX and mPEG-AT1-DOX respectively.Master Thesis Development of protective nano-coatings for electro-optical systems(01. Izmir Institute of Technology, 2016) Karabıyık, Merve; Ebil, ÖzgençElectro-optical (EO) systems have wide range of applications and in recent years, especially the use of EO imaging systems in military and civil aviation applications have substantially increased. In these applications, EO systems are exposed to quite harsh and unstable operating conditions like sudden changes in temperature and humidity, dust, fog, physical shock, vibration and radiation. If their optical surfaces such as prisms, lenses and mirrors are damaged due to these conditions, their repair usually is not possible. To overcome these problems, it is necessary to develop special protective coating layers for optical surfaces. The main goal of this study is to produce protective, self-cleaning and super-hydrophobic polymeric thin films for optical surfaces of the electro-optical (EO) systems. Initiated chemical vapor deposition (iCVD) is a novel method for the fabrication of thin film coatings and it has many advantages such as low production cost, very low deposition temperature, 3D geometry coating performance and high deposition rate. Therefore, iCVD was employed to fabricate homopolymers of poly (glycidyl methacrylate) (PGMA) and poly (1H, 1H, 2H, 2H-Perfluorodecyl acrylate) (PPFDA) and P(GMA-PFDA) copolymer thin-films as protective coatings for EO systems. Optical modeling and simulations were performed to determine the effect of film thickness and refractive index on optical performance of substrates to be coated. Optical performance of fabricated coatings was also measured between 400 and 1000 nm range to confirm that protective coatings do not have any measureable impact on optical performance provided that the protective film thickness is kept between 50 nm to 1 μm. The surface morphology of the protective coatings was evaluated using a variety of analytical tools such as Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and Contact Angle measurements. Optical tests were performed by following MIL-F-48616 Military Standard (MIL-STD). The best protective coatings were obtained by using P(GMA-PFDA) copolymer which yields good mechanical properties due to epoxy pendant group and super hydrophobicity due to incorporation of fluoro monomer.Master Thesis Synthesis of Silica Nano Particles With Custom-Made Morphology for Controlled Drug Delivery(Izmir Institute of Technology, 2012) Siretli, Çağrı; Polat, MehmetThe purpose was to have nanosized particles with low energy perimeters which function as non-reacting transporters for targeted delivery along with high energy sites inside the pores to achieve controlled release of specialized chemicals. Surfactants were used in combination with both base and acid catalyzed methods to achive desired structural properties and the characterization studies such as SEM, TEM, FTIR, BET surface area, pore size, size and zeta potential measurements were conducted. The effect of surfactants on mesoporous silica production changed depending on the type of methods. In the case of base catalysed method in alcohol, formation of stabilized emulsions with different sizes and their effect on the size and shape of silica particles was proposed. The effect of surfactants was attributed to their effect on a) the emulsification process and b) silica-silica and silica-surfactant interactions involved. In the case of base catalysed silica production in water, however, surfactant micelles were used as templates to produce pores. The effect of surfactant type and concentration was attributed to their effect on the CMC, micelle shape and size. Rod-like (~400 nm) at high and spherical (~200 nm) particles at low concentrations were synthesized. Here the surface area of ~1000 m2/g and average pore size of ~3 nm were obtained. Carbonization of these materials were performed to obtain nanosized silica particles with low energy perimeters successfully. Acid catalysed silica production in water was similar. Rod-like (600-800 nm) and cubic (800-1000 nm) nanoparticles were produced. These particles exhibited lower surface area of ~700 m2/g and larger pore size of ~5 nm.