Ülkü, Semra
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Ülkü, Ayşe Semra
Uelkue, S.
Uelkue, Semra
Ulku, S
Ulku, S.
Ülku, S.
Ülkü, S.
Ulku, Semra
Ulkü, Semra
Uelkue, S.
Uelkue, Semra
Ulku, S
Ulku, S.
Ülku, S.
Ülkü, S.
Ulku, Semra
Ulkü, Semra
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03.02. Department of Chemical Engineering
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Former Staff
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Sustainable Development Goals
1NO POVERTY
0
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2ZERO HUNGER
8
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3GOOD HEALTH AND WELL-BEING
6
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4QUALITY EDUCATION
5
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5GENDER EQUALITY
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6CLEAN WATER AND SANITATION
18
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7AFFORDABLE AND CLEAN ENERGY
21
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8DECENT WORK AND ECONOMIC GROWTH
7
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9INDUSTRY, INNOVATION AND INFRASTRUCTURE
21
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10REDUCED INEQUALITIES
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11SUSTAINABLE CITIES AND COMMUNITIES
2
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12RESPONSIBLE CONSUMPTION AND PRODUCTION
19
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13CLIMATE ACTION
21
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14LIFE BELOW WATER
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15LIFE ON LAND
3
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16PEACE, JUSTICE AND STRONG INSTITUTIONS
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17PARTNERSHIPS FOR THE GOALS
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79
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3355
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28
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Scholarly Output
100
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68
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97619/65147
Supervised MSc Theses
14
Supervised PhD Theses
8
WoS Citation Count
2953
Scopus Citation Count
3286
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13
WoS Citations per Publication
29.53
Scopus Citations per Publication
32.86
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95
Supervised Theses
22
| Journal | Count |
|---|---|
| Journal of Thermal Analysis and Calorimetry | 9 |
| Journal of Applied Polymer Science | 6 |
| Microporous and Mesoporous Materials | 4 |
| Applied Clay Science | 4 |
| Industrial and Engineering Chemistry Research | 4 |
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Article Citation - WoS: 3Citation - Scopus: 2Adsorption of No in Clinoptilolite-Rich Zeolitic Mineral by Concentration Pulse Chromatography Method(Elsevier Ltd., 2016) Narin, Güler; Ülkü, SemraThe equilibrium and kinetic parameters for NO adsorption in a clinoptilolite-rich natural zeolitic material from Turkey were determined using the concentration pulse chromatography method. Under the experimental conditions (carrier gas velocities and adsorption temperatures) the micropore diffusion resistance was found to be the mass transfer controlling step. Matching the first moment of the response peaks to the mathematical model the Henry's Law constants and heat of adsorption at zero loading were determined. The axial dispersion, external film, macropore and micropore diffusion coefficients, and activation energy for diffusion of NO in the micropores were calculated from the analysis of the second moments of the response peaks. For successive NO pulses without regeneration between the pulses, the retention times of the response peaks decreased and peak areas increased with the injection number indicating irreversible adsorption. The reversibly adsorbed NO could be desorbed by purging with an inert gas at the adsorption pressure and temperature. Temperature programmed desorption profile obtained by heating the NO saturated adsorbent to 400 °C under inert flow revealed presence of multiple irreversibly adsorbed species in NZ with different thermal stabilities. Desorption of these species was not achieved during the heating up to 400 °C which makes the natural zeolitic materıal suitable for NO storage rather than for cyclic adsorptive separation processes.Article Citation - WoS: 30Citation - Scopus: 31Water and Water Vapor Sorption Studies in Polypropylene-Zeolite Composites(Wiley, 2003) Pehlivan, Hilal; Özmıhçı, Filiz; Tıhmınlıoğlu, Funda; Balköse, Devrim; Ülkü, SemraWater and water vapor sorption to porous polypropylene-zeolite composites prepared by hot pressing have been studied as a function of zeolite loading. This work presents the first report on the effect of the zeolite as a filler on the water-sorption properties of PP composites. Water swelling experiments were conducted at 25°C using pure PP and PP-zeolite films samples having different zeolite loadings (6-40 wt %). Because PP is a hydrophobic polymer, it does not sorp any water, but the composites having 10, 20, 30, and 40% zeolites have sorbed 0.63, 1.00, 1.72 and 3.74% water, respectively. The zeolite itself at the same conditions sorbed 24.5% water. As the filler loading in the composites increased, equilibrium uptake values increased also. On the other hand, water vapor sorption and kinetics has been studied using a Cahn 2000 gravimetric sorption system. Within in the range of 0.35-0.95% water vapor was adsorbed by the composites containing 10-40 wt % zeolites. Experimental effective water vapor diffusivities of the composite films was about one order of magnitude higher (10-fold) than the experimental water diffusion coefficient in composites. The transport of water in composites was slower than that in the liquid water due to the longer diffusion pathway and adsorption on the surface of the composites. Although the liquid water may fill all the voids in the composite, water vapor is adsorbed on the surface of the zeolite only.Master Thesis A novel drug carrier system using clinoptilolite for ginkgo biloba leaf extract(Izmir Institute of Technology, 2004) Göktaş, Selda; Ülkü, Semra; Ülkü, SemraThe use of natural and synthetic zeolites for pharmacological applications in possible encapsulation and/or adsorption of different ions and molecules in their open frame-work, and the subsequent release has emerged as a promising field during last years. In this study, the possible use of clinoptilolite-rich mineral as a novel drug carrierfor the active constituents present in Ginkgo biloba leaf extract solutions was investigated.In the first place, the extraction conditions for the compounds of interest (terpene lactones and flavonoid aglycones) within the leaf material were optimized. The extraction processes were performed with 80% ethanol aqueous solution due to its being non-toxic in nature and widely-used solvent for the preservation of the antioxidant activity possessed by the extract. For the quantification of the extracted species, HighPerformance Liquid Chromatography (HPLC) analysis was conducted. The quantification of terpene lactones was achieved with Evaporative Light Scattering Detection (ELSD), whereas flavonoid glycosides were quantified by Ultraviolet (UV) detection after being converted to their aglycone forms via acidic hydrolysis.In the adsorption studies, clinoptilolite having a particle size in the range 25- 106um was experimented. The flavonoid aglycone constituents were found to be selectively adsorbed on the clinoptilolite surface, whereas terpene lactones were determined to be adsorbed on the clinoptilolite surface in negligible amount. Therefore, the study concentrated on the adsorption of flavonoid constituents on the surface of the zeolitic material.Finally, the antioxidant activity determinations of the extract solutions were performed by the Trolox Equivalent Antioxidant Capacity (TEAC) assay. The antioxidant activity measurements performed for the Ginkgo leaf extract and commercial tablet extract solutions both showed decreasing antioxidant activities via adsorption. The decrease in antioxidant activity was related to the adsorption of phenolic constituents on the clinoptilolite surface.Doctoral Thesis Cr (vi) Removal With Natural, Surfactant Modified and Bacteria Loaded Zeolites(Izmir Institute of Technology, 2011) Cansever Erdoğan, Beyhan; Ülkü, Ayşe SemraThe objective of the study is to determine the bacteria removal performances of the local clinoptilolite rich mineral and its surfactant modified forms and to investigate potential applications of clinoptilolite rich mineral, surfactant modified clinoptilolite rich mineral and bacteria loaded forms in Cr (VI) sorption. Characterizations of clinoptilolite rich mineral and its modified forms were studied. Batch sorption experiments were performed and the effects of the parameters such as pH, initial concentration, agitation speed, particle size and temperature were investigated. Sorption kinetic data were analysed by external mass transfer, intraparticle diffusion, pseudo first and second order models. Intraparticle diffusion model results indicated that sorption of Cr (VI) on the sorbents was a multi-step process, involving external and intraparticle diffusion. Effective diffusion coefficient results implied that Cr (VI) sorption process was not solely intraparticle diffusion controlled and external film diffusion was also effective. Biot number (100-3000) results indicated that Cr (VI) sorption process was mainly controlled by intraparticle diffusion. The sorption reaction model results revealed that sorption of Cr (VI) onto sorbents was well represented by the pseudo-second order kinetic model. Sorption isotherm model results indicated that the Langmuir isotherm fitted well with the experimental data. Thermodynamic analysis, Gibbs energy change (<-20 kJ/mol), entropy change of sorption (<-0.2 kJ/mol K), enthalpy change (<-100kJ/mol) and activation energy (<40 kJ/mol) showed that sorption process was exothermic, spontaneous and physical sorption.Article Citation - WoS: 55Citation - Scopus: 60Effect of Regeneration Temperature on Adsorption Equilibria and Mass Diffusivity of Zeolite 13x-Water Pair(Elsevier Ltd., 2016) Sayılgan, Şefika Çağla; Mobedi, Moghtada; Ülkü, SemraThe adsorption equilibrium and mass diffusivity of zeolite 13X-water pair for different adsorption and regeneration temperatures were determined by a homemade volumetric system. The isotherms of the zeolite 13X-water pair were obtained by collecting pressure versus time data and applying ideal gas law. The effective diffusivity of the pair was calculated by using long term analytical solution of mass diffusivity based on Fick's law. The experimental study showed that the adsorption capacity of zeolite 13X-water pair was 23% (kg/kg), 21% (kg/kg) and 19% (kg/kg) when the adsorption temperature was 35, 45 and 60 °C respectively for the desorption temperature of 90 °C. Furthermore, the adsorption capacity increased from 22% (kg/kg) to 24% (kg/kg) when the desorption temperature was increased from 90 °C to 150 °C. It was observed that the present adsorption equilibrium results were compatible with the reported results in the literature. The mass diffusivity of the pair was found in the range of 4 × 10-9-6 × 10-8 m2/s for the long time period when the initial adsorptive pressure was 2000 Pa. The effective mass diffusivity depends on concentration and it was decreased with increasing adsorbate concentration.Doctoral Thesis Recovery of Phytochemicals (having Antimicrobial and Antioxidant Characteristics) From Local Plants(Izmir Institute of Technology, 2010) Altıok, Evren; Ülkü, SemraThe objective of the present work was to assess the selective isolation of polyphenols from olive leaf and grape skin, which are supplied from the main local plants. The effects of extraction conditions on the types and amounts of polyphenolic compounds and selective separation of them by adsorption were investigated. The batch adsorption and dynamic column studies were performed by silk fibroin and clinoptilolite. Kinetic models were used to determine the mechanism of adsorption. Dynamic column models were applied to optimize the operating parameters. The biological activities of isolated fractions from the crude extracts were determined by analyzing their antioxidant, antimicrobial and cytotoxic activities. Recovered trans-resveratrol significantly inhibited all pathogenic microorganisms. However, higher concentration of grape skin crude extract is required to achieve same inhibition. Although grape skin extract did not have any effect on prostate and breast cancer cells, trans-resveratrol has very significant inhibition effect.Article Citation - WoS: 19Citation - Scopus: 21Microwave Effect on Ion-Exchange and Structure of Clinoptilolite(Springer Verlag, 2007) Akdeniz, Yelda; Ülkü, SemraThe effect of microwave irradiation on the ion exchange degree and structure of clinoptilolite mineral has been examined in comparison with the conventional heat treatment in waterbath. Clinoptilolite-rich mineral from the Western Anatolia, Bigadiç region was used for the experimental study. The mineral was mainly clinoptilolite (80-85%) and additionally, quartz (5-10%), and analcime+mordenite (<5%) were found as co-existing minerals. The mineral was stable towards dehydration and maintains its original structure up to 800°C. The BET and Langmuir surface areas of the sample were found to be 22 and 17m2/g for N2 adsorption and 28 and 22m2/g for Ar adsorption, respectively. For the exchange experiments, clinoptilolite rich mineral was treated with 1N NaCl salt solution both in a microwave unit and waterbath for 10min, 1h and 2h at 80°C. The waterbath treatment with the same conditions was continued for two additional weeks. The chemical composition of the parent and Na-exchanged forms of the clinoptilolite rich minerals were analyzed by using Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-AES). Microwave treatment was found to be more rapid and effective for ion exchange compared to conventional waterbath treatment. Additionally, the XRD results reveal that microwave irradiation has zero effect on the structure of the clinoptilolite rich mineral.Master Thesis Removal of Heavy Metals From Wastewaters by Use of Natural Zeolites(Izmir Institute of Technology, 2001) Türkmen, Müşerref; Ülkü, SemraIn the present study, clinoptilolite rich local natural zeolite was proposed as an ion-exchanger for the removal of heavy metals (Pb2+, Cu2+, Zn2+) from wastewaters.Natural zeolite samples were exposed to a simple pretreatment process which included washing and drying to remove impurities and dust.Thermal and adsorption related properties of washed and original zeolite samples were determined by TGA and N2 adsorption analyses. In TGA analyses, average water content for washed and original samples were found as 9.44 and 10.13 % respectively. In N2 adsorption studies, both washed and original samples showed the characteristic Type IIb isotherm. BET surface areas of the samples were calculated as 39.73 and 47.72 m2/g for washed and original samples respectively.Pretreatment process was found to improve the adsorption capacity of clinoptilolite due to the removal of impurities and dust.In ion-exchange studies, efficiency of natural zeolite in removal of heavy metals from the solutions was investigated based on some physical and chemical variables. For this purpose, particle size and the amount of zeolite in the solution, contact time of the metal containing solution with zeolite were selected as physical variables and pH, metal concentration of the solution, and the presence of other ions were selected as chemical variables. The chemical analyses of all exchange solutions were performed by using ICP-AES. Removal % of the metal ions from the solutions were obtained. Based on the experimental results, zeolite exhibited a significant affinity to Pb2+, followed by Cu2+ and Zn2+ even in the presence of competing cations.To test the applicability of natural zeolite for the treatment of Acid Mine Drainage (AMD), zeolite samples were allowed to contact with simulated AMD solutions.Consequently, natural zeolite was found to be an efficient ion exchanger for removing lead, copper and zinc ions from aqueous solutions.Article Citation - WoS: 112Citation - Scopus: 130The Effect of Hcl Treatment on Water Vapor Adsorption Characteristics of Clinoptilolite Rich Natural Zeolite(Elsevier Ltd., 2005) Çakıcıoğlu Özkan, Fehime; Ülkü, SemraIn this study, water vapor adsorption properties of the clinoptilolite rich zeolite tuff, from Bigadic (Turkey), and its modified forms were examined. The modified forms were obtained by treating the tuff with HCl solutions (0.032, 0.16, 0.32, 1.6 or 5 M) at 25,40,75 and 100°C for 3 h. Infrared spectroscppy and water vapor adsorption were used for the characterization of the zeolites. Langmuir, BET and Dubinin-Raduschevich methods were applied in the analysis of water vapor adsorption data. Applications of Dubinin Raduschevich equation to the water adsorption data displayed that the super-micropore volume was not very sensitive to acid treatment. It was found out that the Langmuir surface area and ultra-micropore volume depend on the degree of the removal of aluminum from the structure.Article Citation - WoS: 2Citation - Scopus: 2A Study of Chemical and Physical Changes During Biaxially Oriented Polypropylene Film Production(Walter de Gruyter GmbH, 2003) Ülkü, Semra; Balköse, Devrim; Arkış, Esen; Sipahioğlu, MuzafferPolypropylene films obtained during the biaxial orientation process were characterized by energy dispersive X-ray analysis (EDX), scanning electron microscopy. X-ray diffraction, differential scanning calorimetry, infrared spectroscopy. Inorganic particles with Al, Si, Na, Mg, Ti, K,O elements were present in biaxially oriented films. Polypropylene had molecules with both isotactic configuration and it was crystallized only in isotactic α phase. The films drawn in one and two directions had unit cells with b axis parallel to surface of the films. The antioxidants present in the films were consumed during processing, preventing polypropylene oxidation in air at high processing temperatures. One surface of the films contained less polypropylene and had functional groups rich in oxygen such as C=O and COO.