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 Fabrication of Colorimetric Ph Indicator Films by Electrospinning(Izmir Institute of Technology, 2022) Erez, Elif; Bayramoğlu, Beste; Eroğlu, Ahmet EminThe trend in the food packaging industry evolves towards innovative packaging materials as biosensors, which record the status of the product and can warn the consumer. The logic behind the colorimetric pH biosensor is that they provide the essential information about food visually by detecting change in pH. Anthocyanins are natural color pigments susceptible to pH change. Purple basil is rich in anthocyanins. In this study, ultrasound-assisted extraction was used for the extraction of dry purple basil. The processing conditions were optimized by response surface methodology (RSM) in terms of the total monomeric anthocyanin content and the increase in green intensity with pH. Electrospinning is a nanofiber fabrication operation used to encapsulate sensitive bioactive compounds for the production of intelligent sensing system. Polycaprolactone (PCL) films incorporating different purple basil extract (PBE) concentrations were fabricated by electrospinning procedure for the usage of colorimetric pH-indicator films as intelligent packaging. The most beadles and uniform nanofibrous mats were obtained when the spinning conditions were V=20 kV and Q=0.4 mL h-1for 10% (w v-1) PCLsolutions containing 0.4% and 0.6% (w v-1) PBE. The average fiber diameters in these films were 178.59±52.92 nm and 235.39±92.46 nm, respectively. The films gave promising results with regards to their use as colorimetric pH-indicator films. The time required to observe a visible color change (ΔE) in these films was only 4-5 s. The ΔE values between all successive pH’s were higher than 2, which is detectable by an inexperienced observer. Keywords: Anthocyanin, Purple Basil, Ultrasound-Assisted Extraction, Response Surface Methodology (RSM), Electrospinning, Colorimetric pH-indicator Films.