Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - Scopus: 6Lithium Extraction From Geothermal Brine Using Γ-Mno2: a Case Study for Tuzla Geothermal Power Plant(Elsevier Ltd, 2024) Toprak, S.; Yılmaz, Selahattin; Öncel, Ç.; Baba, Alper; Yılmaz, S.; Demir, Mustafa Muammer; Baba, A.; Koç, G.A.; Demir, M.M.Geothermal brines contain high concentrations of ions and form a source of various valuable elements. The isolation of the elements from their water systems is a great challenge when the gradual depletion of ores in mining is considered. Attempts have been made for a long time to isolate valuable elements from aqueous mixtures prepared in the laboratory. However, those studies might not reflect the complexity of natural systems and might yield results that deviate significantly from the performance in real field systems. In this study, sorption is used to extract lithium ions from a representative field, Tuzla Geothermal Power Plant (TGPP) Turkey, using a mini-pilot reactor introduced to the reinjection well of the plant. Electrolytic manganese dioxide (γ-MnO2), a relatively inexpensive material widely used as the cathode material in lithium-ion batteries, was employed as a sorbent material for lithium. The sorption/desorption performance of the novel γ-MnO2 was investigated under various conditions. Sorption is performed at 360K and 2 bars. The maximum sorption performance was obtained at 1 h in Tuzla GPP. The desorption experiments were performed in acidic solutions. The concentration of Li+ in the desorption solution was found to be 25 mg/L on average when 10 g of γ-MnO2 was dispersed into 30 mL of the acidic aqueous solution. The first desorption solution was used consecutively for collecting more Li+ ions through the desorption of fresh brine-treated powder samples (cumulative desorption). By repeating this process four times consecutively, 230 mg/L of Li+ was obtained in the desorption solution. Moreover, the reusability of the γ-MnO2 sorbent was examined. The sorbent powder showed almost 40% performance efficiency compared to virgin powder under the conditions employed in this study. The use of electrolytic γ-MnO2 sorbent for lithium adsorption was found to be a promising process for practical use in the separation of lithium from geothermal brines. © 2024Article Citation - WoS: 7Citation - Scopus: 7Epoxidation of Soybean Oil Over Titanium or Niobium Incorporated Sba-15 and Sulfated Lanthanum Titania Silicate Catalysts(Elsevier, 2022) Kalkandelen, Mustafa; Yılmaz, SelahattinMesoporous heterogeneous catalysts were synthesized to develop environmentally benign catalysts for soybean oil's (Glycine max) epoxidation. The investigated materials were sulfated lanthanum doped titania silica xerogel (SO4/La-TiO2-SiO2), and Ti and Nb incorporated SBA-15 with two different silica/metal molar ratios of 10 and 20. Soybean oil epoxidation reactions were performed in tert-butanol by utilizing H2O2 as oxidant at 75 °C for 6 h. Product analysis was carried out by H NMR, FTIR, and analytical methods. Nb-SBA-15 catalysts yielded better conversion than Ti-SBA-15 catalysts owing to their high acidity. However, epoxide selectivity was found low for both catalyst groups due to water in the medium that promoted side reactions. Tert-butanol and ethyl acetate were studied as solvents, but employing ethyl acetate in the reactions triggered catalysts aggregation and deposition on the reactor surface. Stability tests indicated the robustness of Ti and Nb against leaching, whereas sulfur leaching was noted with SO4/La-TiO2-SiO2 catalyst. The most active Nb-SBA-15 (10) catalyst was also applied in the epoxidation of soybean-derived fatty acid methyl esters (FAME). The results showed that small-sized FAME molecules did not enhance the reaction rate. Reusability tests indicated that Nb-SBA-15 (10) was active in epoxidation for at least three cycles.Article Citation - WoS: 13Citation - Scopus: 14Detection of Crispr-Cas9 Mutations Using a Carbon Nanotube-Modified Electrochemical Genosensor(MDPI, 2021) Kıvrak, Ezgi; Pauzaite, Tekle; Copeland, Nikki A.; Hardy, John G.; Kara, Pınar; Fırlak, Melike; İnce Yardımcı, Atike; Yılmaz, Selahattin; Palaz, FahreddinThe CRISPR-Cas9 system has facilitated the genetic modification of various model organisms and cell lines. The outcomes of any CRISPR-Cas9 assay should be investigated to ensure/improve the precision of genome engineering. In this study, carbon nanotube-modified disposable pencil graphite electrodes (CNT/PGEs) were used to develop a label-free electrochemical nanogenosensor for the detection of point mutations generated in the genome by using the CRISPR-Cas9 system. Carbodiimide chemistry was used to immobilize the 5 '-aminohexyl-linked inosine-substituted probe on the surface of the sensor. After hybridization between the target sequence and probe at the sensor surface, guanine oxidation signals were monitored using differential pulse voltammetry (DPV). Optimization of the sensitivity of the nanogenoassay resulted in a lower detection limit of 213.7 nM. The nanogenosensor was highly specific for the detection of the precisely edited DNA sequence. This method allows for a rapid and easy investigation of the products of CRISPR-based gene editing and can be further developed to an array system for multiplex detection of different-gene editing outcomes.Article Citation - WoS: 34Citation - Scopus: 39Aptamer-Based Electrochemical Biosensing Strategy Toward Human Non-Small Cell Lung Cancer Using Polyacrylonitrile/Polypyrrole Nanofibers(Springer, 2020) Kıvrak, Ezgi; İnce Yardımcı, Atike; İlhan, Recep; Ballar Kırmızıbayrak, Petek; Yılmaz, Selahattin; Kara, PınarIn the present study, a sensitive electrochemical aptamer-based biosensing strategy for human non-small cell lung cancer (NSCLC) detection was proposed using nanofiber-modified disposable pencil graphite electrodes (PGEs). The composite nanofiber was comprised of polyacrylonitrile (PAN) and polypyrrole (PPy) polymers, and fabrication of the nanofibers was accomplished using electrospinning process onto PGEs. Development of the nanofibers was confirmed using scanning electron microscopy (SEM). The high-affinity 5 '-aminohexyl-linked aptamer was immobilized onto a PAN/PPy composite nanofiber-modified sensor surface via covalent bonding strategy. After incubation with NSCLC living cells (A549 cell line) at 37.5 degrees C, the recognition between aptamer and target cells was monitored by electrochemical impedance spectroscopy (EIS). The selectivity of the aptasensor was evaluated using nonspecific human cervical cancer cells (HeLa) and a nonspecific aptamer sequence. The proposed electrochemical aptasensor showed high sensitivity toward A549 cells with a detection limit of 1.2 x 10(3)cells/mL. The results indicate that our label-free electrochemical aptasensor has great potential in the design of aptasensors for the diagnostics of other types of cancer cells with broad detection capability in clinical analysis.Article Citation - WoS: 8Citation - Scopus: 8Synthesis of Butyl Glucoside Over Sulphated Zr-Sba and Tungstophosphoric Acid Incorporated Sba-15 Catalysts(Elsevier Ltd., 2021) Mutlu, Nahide Nuran; Yılmaz, SelahattinGlycosidation of glucose with n-butanol was studied over sulphated Zr incorporated SBA-15 and tungstophosphoric acid (TPA) incorporated SBA-15 catalysts. The catalysts were prepared with different Zr, TPA and SO4 amounts via hydrothermal synthesis. SBA-15 structure was preserved and Zr and TPA were successfully incorporated. Sulphation improved the acidity of Zr-SBA-15 and the ratio of Brønsted to Lewis acid sites (B/L) increased. Thus, much higher butyl glucoside yields (about 70 %) were obtained over SO4/Zr-SBA-15 catalysts. However, 15 % activity loss was observed after 2 re-use due to sulphate leaching. TPA-SBA-15 catalysts had the highest B/L and provided very high catalytic activity with butyl glucoside yields above 95 %. The initial rate of butyl glucoside formation over TPA-SBA-15 catalysts were close to that of H2SO4. These catalysts were found stable and reusable. Reaction temperature and catalysts amount was studied as the reaction parameters over the most active and selective catalyst. © 2020 Elsevier B.V.Article Citation - WoS: 86Citation - Scopus: 98Characterization and Catalytic Activity of Cufezsm-5 Catalysts for Oxidative Degradation of Rhodamine 6g in Aqueous Solutions(Elsevier Ltd., 2010) Dükkancı, Meral; Gündüz, Gönül; Yılmaz, Selahattin; Yaman, Y. C.; Prikhod’ko, R. V.; Stolyarova, I. V.This study presents an evaluation of the catalytic performances of Fe and Cu containing ZSM-5 zeolites for oxidation of Rhodamine 6G. Fe and Cu were loaded by ion exchange or through hydrothermal synthesis. The catalytic process was carried out in an aqueous solution using H2O2 as an oxidant. The catalyst prepared by hydrothermal synthesis showed the highest activity (100% decolorization, 59.1% aromatic degradation and 51.8% TOC removal at initial pH of 3.5). This catalyst was stable against leaching even at low pH. The change in activity of the catalysts prepared was attributed to incorporation of the Fe and Cu species with ZSM-5. Fe and Cu were in structural locations - in the framework - in the catalyst prepared by hydrothermal synthesis while there were extraframework cations or species in catalysts prepared by ion exchange. Incoporation of Cu into FeZSM-5 increased its catalytic activity. © 2010 Elsevier B.V. All rights reserved.Article Citation - WoS: 165Citation - Scopus: 174Heterogeneous Fenton-Like Degradation of Rhodamine 6g in Water Using Cufezsm-5 Zeolite Catalyst Prepared by Hydrothermal Synthesis(Elsevier Ltd., 2010) Dükkancı, Meral; Gündüz, G.; Yılmaz, Selahattin; Prihod’ko, R. V.In this study, heterogeneous Fenton-like degradation of reactive azo dye Rhodamine 6G in water was investigated over a CuFeZSM-5 zeolite catalyst prepared by hydrothermal synthesis. At initial pH of 3.4, a color removal of 100% was achieved after a reaction time of 45min. TOC elimination was measured to be 51.8% after 2h of oxidation. Initial decolorization rate was described by an equation of -rA0=4.56×102 e-24.83/RTCR6G,0CH2O2,00.35 where R is in kJ/mol. The leaching of iron and copper cations from zeolite structure into the solution during oxidation was dependent on pH strongly. The regulation of pH from 6.5 (dye solution pH) to 3.4, increased leaching for iron from 0.7 to 0.8mg/dm3 and for copper from 1.4 to 2.1mg/dm3. The copper was totally leached from the catalyst during the process at pH 3.4. © 2010 Elsevier B.V.Article Citation - WoS: 54Citation - Scopus: 62Sic-Particulate Aluminum Composite Foams Produced by Powder Compacts: Foaming and Compression Behavior(Springer Verlag, 2003) Elbir, Semih; Yılmaz, Selahattin; Toksoy, Ahmet Kaan; Güden, Mustafa; Hall, Ian W.The foaming behavior of SiC-particulate (8.6% by volume) aluminum composite powder compacts contained Titanium Hydride blowing agent was investigated by heating above the melting temperature (750°C) in a pre-heated furnace. Aluminum powder compacts were also prepared and foamed using similar compaction and foaming parameters in order to determine the effect of SiC-particulate addition on foaming and compression behavior. The linear expansions of the compacts at various furnace holding times were ex situ determined. Optical and scanning electron microscopy techniques were used to characterize prepared and deformed foams microstructures. The SiC-particulate addition was found to increase the linear expansion and reduce the extent of the liquid metal drainage and cell coarsening of the aluminum compacts. The composite foam samples also showed higher compressive stresses, but a more brittle behavior as compared with aluminum foams.