Chemical Engineering / Kimya Mühendisliği

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  • Article
    Impact of Titania Phase Structure and Surface Reactivity on the Photocatalytic Degradation of Various Dyes and Textile Wastewater
    (National Institute of Science Communication and Policy Research, 2023) Yurtsever, Hüsnü Arda; İloğlu, Onur; Çiftçioğlu, Muhsin
    Titania (TiO2) powders have been prepared by precipitation method in different precipitation media which contain sulfate, nitrate or organic species. Photocatalytic degradation of different dyes and a real textile wastewater have been conducted with these powders along with commercial powder Degussa P25 for comparison. Ethyl alcohol (organic medium), sulfuric acid (sulfate medium) and nitric acid (nitrate medium) have been used to dissolve titanium precursor for the precipitation of TiO2 in ammonia solution. UV-Vis DRS and XPS results indicate that S doping in sulfate medium precipitated powder and N doping in nitrate medium precipitated powder has been occurred and the presence of S or N containing impurities on the grain boundaries have been improved light absorption of TiO2 significantly. However, these powders have exhibited low surface reactivities. The highest surface reactivity has been obtained with the powder precipitated in organic medium which also has the highest crystallite sizes (76 nm rutile and 34 nm anatase crystallites) with relatively low rutile weight percentage (10.0%). The surface-normalized rate constants of this powder are 0.02038 min-1.m-2 in real textile wastewater degradation and 0.0161 min-1.m-2 in methyl orange degradation, which are 0.01563 and 0.0091 min-1.m-2, respectively, for Degussa P25. Results have shown that this powder show 30-70% higher surface reactivities compared to Degussa P25. The main structural difference of organic medium precipitated powder and Degussa P25 has been found to be the anatase-rutile weight ratio and crystallite size of rutile phase whereas band gap energy of Degussa P25 is lower and other properties are not significantly different.
  • Article
    Citation - WoS: 3
    Citation - Scopus: 4
    Photocatalytic and Optical Properties of Zinc Oxide Structures Prepared at Different Urea Concentrations
    (Serban Solacolu Foundation, 2020) Uysal, Berk; Şen, Selin; Top, Ayben
    In this study, ZnO samples were synthesized using zinc acetate and urea with a method containing sonication, sol-gel transition and calcination steps. Urea to zinc acetate mole ratio values were changed as 0, 0.5, 1, and 2 and corresponding calcined samples were denoted as UZ-0, UZ-0.5, UZ-1, and UZ-2, respectively. Scanning electron microscopy (SEM) images indicated globular and rod-like structures. Aspect ratios of the nanorods increased as urea to zinc acetate ratio increased from 0 to 1 whereas nanoparticles with sizes of 70 +/- 20 nm were observed for UZ-2 sample. Brunauer, Emmett and Teller (BET) surface area values of the samples varied between 9 and 25 m(2)/g and increased as initial urea amount increased. Band gap energies of the samples ranged between 3.24 and 3.29 eV. Four major peaks at about 400, 420, 480 and 530 nm with different intensities were observed in the photoluminescence (PL) spectra of the samples. All the samples removed rhodamine B by both adsorption and photodegradation. The highest visible light induced photodegradation rate was exhibited by UZ-2 sample having the highest surface area and it is attributed to superior charge separation properties of this sample under visible light.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 16
    Synthesis, Characterization and Adsorption Studies of Phosphorylated Cellulose for the Recovery of Lithium From Aqueous Solutions
    (Editura Acad Romane, 2021) Recepoğlu, Yaşar Kemal; Yüksel, Aslı
    In this study, pristine cellulose was functionalized by the phosphorylation reaction to make it suitable for lithium separation. After characterization studies of the synthesized adsorbent with SEM, EDX, FTIR, TGA and XPS, the effects of various parameters on the lithium uptake capacity of the adsorbent were examined. The analysis of equilibrium data by several adsorption models showed that maximum adsorption capacity of the adsorbent was found to be 9.60 mg/g at 25 degrees C by the Langmuir model. As initial concentration and contact time increased, adsorption capacity also increased, however, mild temperature (25-35 degrees C) and pH (5-6) were better for the adsorption of lithium. 80% of lithium adsorption within three minutes proved the fast kinetic nature of the adsorbent. A 99.5% desorption efficiency of lithium was achieved with 0.5 M H2SO4, among HCl and NaCl with different molarities. Phosphorylated cellulose was shown to be a favorable adsorbent for the recovery of lithium from aqueous solutions.
  • Article
    Citation - WoS: 4
    Citation - Scopus: 5
    Investigating the Effects of Ultrasonic Energy on the Flotation Behavior of Pyrite and Galena Minerals
    (Oficyna Wydawnicza Politechniki Wroclawsjiej, 2020) Horasan, Ümit; Tanrıverdi, Mehmet; Çicek, Tayfun; Polat, Mehmet
    Although pyrite is one of the more abundant minerals of the earth crust, it has low economic value. When it reports to the concentrate during flotation along with the valuable minerals, it decreases the grade of the valuable minerals and leads to an increase in smelting costs. Numerous modifications have been suggested in the literature to increase the selective recovery of pyrite containing base metal-sulfide ores. The use of ultrasonic applications is one such method. In this study, the effect of the ultrasonic application on the flotation behavior of galena and pyrite mineral was investigated through systematic Hallimond Tube experiments. In the initial phase of the experiments, the optimum flotation conditions (particle size, pH, amount of air, and amount of reagent) were determined for the two minerals. Subsequent experiments were carried out under these optimums to distinguish the effect of the ultrasonic application. The influence of how the ultrasonic application was applied (i.e. before and during the conditioning stage or before the re-flotation of the concentrate) was also studied. It was observed that the ultrasonic application had a strong activating influence if it was administered before or during the conditioning stage. The effect was similar to whether the minerals were floated individually or from their mixtures. However, when it was applied to a flotation concentrate before re-flotation, it selectively displayed a depressant action for the pyrite to the extent that no depressants were needed. The results conclusively showed that the ultrasonic application could drastically improve the selectivity of the complex ores.
  • Article
    Citation - WoS: 10
    Citation - Scopus: 9
    Bi̇yomalzemelerden İ̇zole Edi̇len Staphylococcus Epidermidis Suşlarinin Yüzey Özelli̇kleri̇ni̇n Beli̇rlenmesi̇
    (Ankara Mikrobiyoloji Derneği, 2010) Sudağıdan, Mert; Erdem, İlker; Çavuşoğlu, Cengiz; Çiftçioğlu, Muhsin
    The surface properties of bacteria play an important role on adhesion to the biomaterial surface. In this study, the surface properties of Staphylococcus epidermidis strains isolated from clinically used polymeric biomaterial surfaces were investigated on the basis of zeta potential, hydrophobicity and surface topography. A total of 10 S.epidermidis strains isolated from intravenous catheters (n= 5), endotracheal tubes (n= 3) and central venous catheters (n= 2) which were used in the patients of pulmonary Intensive Care Unit, Ege University Medical Faculty Hospital, were included to the study. Seven of those isolates were biofilm producers, inhabiting biofilm genes, 2 were non-biofilm producers, however, inhabiting biofilm genes, and 1 was non-biofilm producer, inhabiting no biofilm genes. Zeta potential analysis have been performed in 3 different buffers (phosphate-buffered saline, 1 mM potassium chloride and 1 mM potassium phosphate buffer) and at different pH values (pH 4.1-8.2), in order to simulate in vivo environment of the biomaterials. Hydrophobicities of the strains were examined by bacterial adhesion to hydrocarbon (BATH) test and the surface topography of biofilms and slime layers were visualized by atomic force microscopy (AFM) and scanning electron microscopy (SEM) methods. It was found that all strains have negative zeta potential values (surface charge) in all buffers and pH values. In hydrophobicity analysis, the highest value (86%) was determined for non-biofilm forming S.epidermidis strain YT-169b (endotracheal tube isolate) and the lowest hydrophobicity (2.5%) was determined for biofilm forming S.epidermidis strain YT-212 (central venous catheter isolate). Biofilm and slime layers of the strains were imaginated by AFM and SEM analysis in ?m scale. SEM analysis showed that bacteria highly adhered to rough surfaces on biomaterial surfaces and the produced slime layers covered the surface of bacteria. In conclusion, elucidating the surface properties of opportunistic pathogens in different physiologic buffers will give important clues for the production of non-adhesive materials and antibacterial surfaces for those bacteria. It was also estimated that designing the surface of the biomaterial to have negative surface charge in the body and to be as smooth as possible will hamper biofilm formation.
  • Conference Object
    Structural and Thermal Characterization of Ti+o Ion Implanted Ultrahigh Molecular Weight Polyethylene (uhmwpe)
    (American Institute of Physics, 2009) Öztarhan, Ahmet; Urkaç Sokullu, Şadiye Emel; Tıhmınlıoğlu, Funda; Kaya, N.; Ila, Daryush; Budak, S.; Nikolaev, A.
    In this work, Metal-Gas Hybrid Ion Implantation technique was used as a tool for the surface modification of Ultra High Molecular Weight Polyethylene (UHMWPE). Samples were Ti + O ion implanted by using Metal-Vapour Vacuum Arc (MEVVA) ion implanter to a fluence of 5x10(16) ion/cm(2) for each species and extraction voltage of 30 kV. Untreated and surface treated samples were investigated by Rutherford Back Scattering (RBS) Spectrometry, Attenuated Total Reflectance - Fourier Transform Infrared (ATR-FTIR) Spectroscopy, Thermo Gravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). Results indicate that Ti + O ion implantation can be applied on UHMWPE surfaces successfully. ATR-FTIR spectra indicate that the C-H concentration on the surface decreased after Ti + O implantation. Thermal characterization with TGA and DSC shows that polymeric decomposition temperature is shifted after ion implantation.
  • Book Part
    Polyelectrolytes Thermodynamics and Rheology Preface
    (Springer, 2014) Visakh, P. M.; Bayraktar, Oğuz; Alfredo Pico, Guillermo
    [No abstract available]
  • Article
    Citation - WoS: 3
    Validation on of Local Thermal Equilibrium and Uniform Pressure Assumptions for an Isobaric Adsorption Process in an Adsorbent Bed
    (Türk Isı Bilimi ve Tekniği Derneği, 2016) Gediz İliş, Gamze; Mobedi, Moghtada; Ülkü, Semra
    Bu çalışmanın amacı, adsorbent yatakta ısı ve kütle transferini analiz etmek için kullanılan yerel ısıl denge ve sabit basınç yaklaşımı varsayımların geçerliliğini araştırmaktır. İçerisinde silika jel partikülleri içeren bir yatak ile su kabı olan bir deney düzeneği tasarlanmış ve adsorpsiyon sürecinde yatağın içinde farklı yerlerde yerel sıcaklık ve basınç ölçülmüştür. Ayrıca, sabit basınç yaklaşımı ve yerel ısıl denge varsayımlara dayalı ısı ve kütle transferi denklemleri çözülmüştür. Sayısal sonuçlar, ilgili deneysel sonuçlarla karşılaştırılmış ve aralarında oldukça iyi bir uyum tespit edilmiştir. Gerçekleştirilen karşılaştırmaya dayanarak, incelenen yatak için iki önemli sonuç şu şekildedir: a) katı madde ve su buharı arasında yerel ısıl denge bulunmaktadır, b) bir yatak içinde parçacıklar arası kütle transferi direnci ihmal edilebilir düzeyde olup konsantrasyonunun ve sıcaklığın belirlenmesi için sabit basınç yaklaşımı geçerlidir. Ayrıca, bu çalışmada sunulan deneysel sonuçlar diğer araştırmacıların sayısal çalışmalarının geçerliliğini doğtulamak için değerli veriler sağlayacaktır.
  • Article
    Citation - WoS: 18
    Citation - Scopus: 17
    Cnt Incorporated Polyacrilonitrile/Polypyrrole Nanofibers as Keratinocytes Scaffold
    (Trans Tech Publications, 2019) İnce Yardımcı, Atike; Aypek, Hande; Öztürk, Özgür; Yılmaz, Selahattin; Özçivici, Engin; Meşe, Gülistan; Selamet, Yusuf
    Polypyrrole (PPy) is an attractive scaffold material for tissue engineering with its non-toxic and electrically conductive properties. There has not been enough information about PPy usage in skin tissue engineering. The aim of this study is to investigate biocompatibility of polyacrilonitrile (PAN)/PPy nanofibrous scaffold for human keratinocytes. PAN/PPy bicomponent nanofibers were prepared by electrospinning, in various PPy concentrations and with carbon nanotube (CNT) incorporation. The average diameter of electrospun nanofibers decreased with increasing PPy concentration. Further, agglomerated CNTs caused beads and disordered parts on the surface of nanofibers. Biocompatibility of these PAN/PPy and PAN/PPy/CNT scaffolds were analyzed in vitro. Both scaffolds provided adhesion and proliferation of keratinocytes. Nanofiber diameter did not significantly influence the morphology of cells. However, with increasing number of cells, cells stayed among nanofibers and this affected their shape and size. In this study, we demonstrated that PAN/PPy and PAN/PPy/CNT scaffolds enabled the growth of keratinocytes, showing their biocompatibility.
  • Book Part
    Citation - WoS: 28
    Citation - Scopus: 26
    Laos (large Amplitude Oscillatory Shear) Applications for Semisolid Foods
    (Springer, 2019) Yazar, Gamze; Çağlar Duvarcı, Özlem; Yıldırım Ertürk, Merve; Kokini, Josef L.
    The rheological behavior of semisolid foods under large amplitude oscillatory shear (LAOS) can offer more detailed understanding of structural changes occurring during processing and consumption compared to traditional rheometry. This chapter focuses on a detailed description of LAOS measurements, including theory, testing method, data interpretation, and corrections. It also discusses LAOS application to food systems with different core structures ranging from dilute dispersions to gels, foams, emulsions, and soft elastic networks, along with a special emphasis on yogurt. Type of stress responses for different rheological behavior, Lissajous-Bowditch curves, and the resulting LAOS parameters e3/e1, ?3/?1, S, and T) are used to understand the structural changes in all of these foods with special emphasis on high-fat, low-fat, and non-fat yogurt. © 2019, Springer Nature Switzerland AG.