Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Research Project Uçucu kül ve doğal zeolitin beraber kullanılarak borun atık sulardan uzaklaştırılması(2008) Polat, Hürriyet; Polat, Mehmet; Şekeroğlu, KorayBu proje kapsamında, Yeniköy, Kemerköy, Soma ve Yatağan termik santrallerinden alınan uçucu küllerin, sıcaklık, katı / sıvı oranı ve başlangıç konsantrasyonu gibi parametler kullanılarak bor adsorpsiyon kapasiteleri incelenmiştir. Bor adsorpsiyon deneyleri laboratuvarda hazırlanan simültane sular (10, 25, 50, 100 ve 300 ppm Bor) ve Kızıldere (Denizli) jeotermal tesislerinden (25-30 ppm Bor) alınan borlu sularla yapılmıştır. Yapılan “batch” deneylere dayanarak, uçucu küllerin boru adsopladığı ve özellikle yüzey alanı en geniş olan Yeniköy külü yeterli zaman ve yüzey alanı sağlandığında %99 ‘a varan adsorpsiyon miktarına ulaştığı gözlenmiştir. Tüm küllerin deney sonuçları tek katmanlı adsorpsiyonu belirten “Langmuir” izotermine ve Kaydırılmış İkinci Mertebe parametresine daha uygun olduğu tespit edilmiştir. Yapılan sıcaklık çalışmalarında, Yeniköy ve Kemerköy külleriyle 25o C, 45o C ve 65o C koşullarında yapılan deneylerin verileri kullanılarak, o ΔH ,o ΔG , o ΔS değerleri hesaplanmıştır. Sıcaklıkla azalan adsorpsiyon kapasitesi ve negatif o ΔH değerleri, ekzotermik adsorpsiyon olduğunu belirtmektedir. Aynı zamanda -40,0 kJ / mol’ün altında çıkan (-52,89 ve -48,55 kJ / mol) entalpi ( o ΔH ) değerleri kimyasal adsorpsiyon olduğunu belirtmektedir. Soma ve Yatağan külleri için de Langmuir izotermlerinin uygun olması kimyasal bir adsorpsiyon olduğunu önermektedir.Article Solunabilir Tozun Su Spreyleri Kullanılarak Bastırılmasında Son Gelişmeler(2000) Polat, Hürriyet; Polat, Mehmet; Gürgen, SabitTürkiye'de görülen meslek hastalıklarının çoğunu tozun solunmasından kaynaklanan pnömokonyoz oluşturmaktadır. Bu yazının amacı, yeraltı ocaklarında işçi sağlığı açısından sakıncalı olan havada asılı tozların, su spreyleri kullanılarak bastırılması konusunda gelinen aşamayı sunmaktır. Bu amaçla, havada asılı toz ve su damlalarıyla yapılan detaylı çalışmalar ışığında, sprey suyuna katılan yüzey aktif maddelerin istenen verim artışını sağlayamama nedenleri ele alınmakta ve su spreylerinin Türkiye'deki maden ocaklarında kullanım olanakları tartışılmaktadır.Conference Object Effect of Some Physical, and Chemical Variables on Flocculation and Sediment Behaviour(A.A. Balkema Publishers, 2000) Polat, Hürriyet; Polat, Mehmet; İpekoğlu, ÜnerEffect of some chemical and physical variables on the settling rate, final sediment height, sediment viscosity and supernatant turbidity of a clay sample was studied using various polyacrylamide type flocculants. Increasing flocculant concentration significantly increased both the settling rate and sediment viscosity. More importantly, changes in the final sediment, height, hence the packing density, was minimal for all the conditions tested once the sediment was allowed to consolidate. Also, the mode of addition of the polymer, at once or continuous, did not seem to affect any of the parameters measured. Conditioning time seemed to alter the settling rate at low polymer concentrations, but had no effect at high polymer concentrations. However, increasing the conditioning time caused a decrease in the sediment viscosity. Different types of the polyacrylimides generated different settling rates at a given concentration, but the final sediment height was nearly independent of polymer type.Conference Object Citation - Scopus: 1Yapay Sindirim Sıvısında Doğal Zeolitlerde Meydana Gelen Morfolojik Değişmeler(Institute of Electrical and Electronics Engineers Inc., 2009) Demirbüker Kavak, Dilek; Özçelik, Serdar; Ülkü, SemraDoğal zeolitler biyoaktif maddelerdir. Doğal zeolitlerin hayvanlarda biyokütle arttırıcı besi katkı maddesi, insanlarda ülser tedavisinde mide asitliğini tamponlayıcı, asitliği düşürücü ilaç gibi değişik kullanım alanları mevcuttur. Değişik sağlık alanlarında kullanımlarından dolayı, zeolitlerin yapısal stabilitesinin sindirim sırasında belirlenmesi; olası olumlu veya olumsuz etkileşimleri anlamak açısından önem taşımaktadır. Gerçekleştirilen araştırmada, yapay sindirim sırasında zeolitte meydana gelebilecek olası morfolojik değişimlerin incelenmesi hedeflenmiştir. Bu amaçla zeolitin ABTS ile radikal sönümleme kapasitesi araştırılmış, yapay sindirim denemeleri gerçekleştirilerek de uygulama süreci sonrası yapıda olası değişimler ve adsorpsiyonlar taramalı elektron mikroskobu, FTIR, XRD analizleri ile incelenmiştir. 3g/100ml zeolitin ABTS radikalini %45 inhibe ettiği bulunmuştur. Taramalı elektron mikroskobu deneyleri sonucunda yapay sindirilmiş örneklerin yüzey morfolojisinde değişim gözlenmemiştir. Element analizleri yapısal kaybın olmadığını, Al ve Si elementlerinin ağırlıkça yüzdelerinin, kontrol örnekleriyle (Al:8.1; Si: 39) sindirilmiş örneklerde (Al:8.2; Si: 38.3) yaklaşık aynı olduğunu göstermiştir. Infrared spektrum (IR) ve X-ray ışını kırınımı analizleri sonuçları ise bu bulguları doğrulamıştır. Ayrıca taramalı elektron mikroskobu ve IR spektrum sonuçları yapay sindirim ortamındaki maddelerin, zeolit yüzeyinde adsorplanmadıklarıını göstermektedir. Sonuç olarak doğal zeolitler, yapay sindirim sırasında yapısal stabilitelerini kaybetmemektedirler.Article Citation - WoS: 10Citation - Scopus: 10Determination of the Particle Interactions, Rheology and the Surface Roughness Relationship for Dental Restorative Ceramics(Elsevier Ltd., 2009) Kes, Mürşide; Polat, Hürriyet; Keleşoğlu, Serkan; Polat, Mehmet; Aksoy, GökhanThe effect of inter-particle interactions on the slurry properties and the final surface roughness of the dental ceramic restoratives was investigated. A commercial dental ceramic powder, IPS Empress 2 veneer, was used as the raw material. The magnitudes of the particle-particle interactions were computed by the DLVO theory for the ceramic slurries of different electrolyte solutions (0.1 M, 0.25 M, 0.5 M, 0.75 M, 1 M NaCl and CaCl2). As expected, the energies of particle-particle interactions were influenced significantly by the presence of electrolytes. These computations demonstrated that addition of electrolytes leads to a progressive depression of the repulsive double layer forces. The absence of these forces should inevitably lead to agglomeration caused by the ever-present van der Waals forces. The rheological measurements carried out using the slurries with same solution properties supported the findings of the DLVO computations. It was found that dental ceramic slurries showed a Newtonian behavior in the absence of electrolytes, which is indicative of little or no agglomeration in the slurry. On the other hand, the same slurries displayed a non-Newtonian, shear thinning behavior in the presence of electrolytes which can be attributed to agglomeration or gelation. Roughness of the ceramic surfaces produced from these slurries was studied by SEM analysis and profilometer measurements. Contact angle studies were also carried out on the same surfaces. It was observed that the surface became rougher initially with electrolyte addition to a maximum, most probably due to formation of isolated agglomerates due to a reduction of the repulsive double layer forces. After reaching a maximum, surface roughness decreased to a much lower value with further increase in electrolyte concentration. This was most probably caused by the formation of a relatively homogeneous, gel-like structure within the extensively agglomerated slurry due to a complete collapse of the double layer.Article Citation - WoS: 98Citation - Scopus: 108Capacity and Mechanism of Phenol Adsorption on Lignite(Elsevier Ltd., 2006) Polat, Hürriyet; Molva, Murat; Polat, MehmetA raw lignitic coal from Soma, Turkey was investigated to determine its potential as an adsorbent for phenol removal from wastewaters. Kinetic batch tests demonstrated that phenol could be completely removed from solution given sufficient solids loading and reaction time. The adsorption capacity of 10 mg/g obtained with the lignite is low compared to those achievable with activated carbons (around 300 mg/g). However, when normalized for the surface area, the adsorption capacity was much larger for the lignite (1.3 mg/m2) than that generally observed with activated carbons (0.05-0.3 mg/m2). Hydrogen-bonding of the phenolic -OH with the oxygen sites on the lignite surface is the most likely mechanism for adsorption. Though water molecules also have affinity for the same oxygen sites, lateral benzene ring interactions make phenol adsorption energetically more favorable. Since phenol molecules adsorbed in this fashion would project their benzene rings into solution, formation of a second layer through the action of the dispersive π-π interactions between the benzene rings is very likely. Residual water quality with respect to major elements and heavy metals was within acceptable limits defined by the ASTM standards. Dissolution of organic matter from the lignite was also observed to be negligible.Article Citation - WoS: 36Citation - Scopus: 40The Kinetics of Citral Hydrogenation Over Pd Supported on Clinoptilolite Rich Natural Zeolite(Elsevier Ltd., 2005) Yılmaz, Selahattin; Uçar, Şule; Artok, Levent; Güleç, HilalThe liquid phase hydrogenation of citral has been investigated over Pd (2.42%) supported on clinoptilolite rich natural zeolite catalyst for different reaction conditions. The zeolite support did not affect the active metal properties. This was attributed to the large size of Pd particles on the support. High selectivity (90%) to citronellal was obtained at complete conversion of citral. The catalytic activity increased with reaction temperature (80, 100, 120°C) following an Arrhenius behaviour, while selectivity remained constant for a given conversion. Selectivity to citronellal increased from 78 to 90% with increase in the amount of catalyst in the reaction solution (Citral/Pd mole ratio 293, 176 and 105). The spent catalyst regained its fresh activity and selectivity upon regeneration.Article Citation - WoS: 123Citation - Scopus: 131A New Methodology for Removal of Boron From Water by Coal and Fly Ash(Elsevier Ltd., 2004) Polat, Hürriyet; Vengosh, Avner; Pankratov, Irena; Polat, MehmetHigh levels of boron concentrations in water present a serious problem for domestic and agriculture utilizations. The recent EU drinking water directive defines an upper limit of 1 mgB/I. In addition, most crops are sensitive to boron levels >0.75 mg/1 in irrigation water. The boron problem is magnified by the partial (∼60%) removal of boron in reverse osmosis (RO) desalination due to the poor ionization of boric acid and the accumulation of boron in domestic sewage effluents. Moreover, high levels of boron are found in regional groundwater in some Mediterranean countries, which requires special treatment in order to meet the EU drinking water regulations. Previous attempts to remove boron employed boron-specific ion-exchange resin and several cycles of RO desalination under high pH conditions. Here, we present an alternative methodology for boron removal by using coal and fly ash as adsorbents. We conducted various column and batch experiments that explored the efficiency of boron removal from seawater and desalinated seawater using several types of coal and fly ash materials under controlled conditions (pH, liquid/solid ratio, time of reaction, pre-treatment, regeneration). We examined the effect of these factors on the boron removal capacity and the overall chemical composition of the residual seawater. The results show that the selected coal and fly ash materials are very effective in removing boron such that the rejection ratio of boron can reach 95% of the initial boron content under certain optimal conditions (e.g., pH = 9, L/S = 1/10, reaction time > 6 h). Our experiments demonstrated that use of glycerin enables regeneration of boron uptake into coal, but the boron uptake capacity of fly ash reduces after several cycles of treatment-reaction. The boron removal is associated with Mg depletion and Ca enrichment in the residual seawater and conversely with relative Mg enrichment and Ca depletion in the residual fly ash. We propose that the reaction of Ca-rich fly ash with Mg-rich seawater causes co-precipitation of magnesium hydroxide in which boron is co-precipitated. The new methodology might provide an alternative technique for boron removal in areas where coal and fly ash are abundant.Article Citation - WoS: 5Citation - Scopus: 7Alumina/Water Suspensions in the Presence of Peo-Ppo Triblock Copolymers(Elsevier Ltd., 2004) Şakar Deliormanlı, Aylin; Polat, Hürriyet; Çiftçioğlu, MuhsinThe aim of this study was to investigate the stability and dispersion behaviour of aqueous alumina suspensions in the presence of polyethylene oxide-polypropylene oxide-polyethylene oxide (PEO-PPO-PEO) type triblock copolymers. For this purpose alumina suspensions at various solids loadings were prepared using four different methods. These are: Method I: powder and water were stirred only; Method II: powder and water were stirred and ultrasonic treatment was applied; Method III: powder and water were stirred in the presence of block copolymers; Method IV: powder and water were stirred and ultrasonic treatment was applied in the presence of block copolymers. These suspensions were characterized by means of rheological measurements. Sedimentation and turbidity measurements were also conducted to support these results and to investigate the stability of these systems for longer times. Surface tension measurements were performed to investigate the adsorption behaviour of block copolymers onto alumina surface. It was found that the use of PEO-PPO-PEO type triblock copolymers improved the dispersion behaviour of aqueous alumina suspensions in the presence of ultrasonic treatment at low solids loadings. However their effect was not significant at high solids loadings and without ultrasonic treatment.Conference Object Citation - WoS: 2Citation - Scopus: 2Effects of Mechanical Treatment on the Formation of Α-Al 2o3 From Gibbsite(Trans Tech Publications, 2004) Şakar Deliormanlı, Aylin; Çiftçioğlu, Muhsin; Polat, HürriyetIn this study preparation of fine alpha alumina powders derived from Bayer gibbsite was studied. Preparation of the alumina powders was performed by decomposition of the gibbsite into transition alumina phase followed by controlled transformation to the alpha phase. Gibbsite was thermally treated at 350°C and 900°C to obtain a transition form of alumina. The purpose of the heat treatment at 350°C was to increase the surface area of the gibbsite particles and obtain a loosely packed structure that may reduce the size of the rather coarse precursor gibbsite during the grinding step. Mechanical treatment (by using ultrasonic forces and impact forces) was utilized to increase the transformation rate to the alpha alumina in the transition phase matrix and influence the nucleation and growth rate of the solid -solid phase transformation. These powders were calcined at 1100, 1200 and 1450°C for 1 to 8 hours. Results indicated that transformation to the alpha phase was accomplished in the powders preheated at 900°C, ultrasonically treated or ground, and then calcined at 1200°C for 2 to 8 hours or at 1450°C for 2 hours. Ultrasonic treatment accelerated the transformation rate to the alpha phase at 1100°C in 2 hours. Powders that were calcined at 1100 to 1200°C for 1 hour had a significant kappa content together with the alpha phase. Additionally the powder prepared without mechanical treatment and calcined at 1100°C was mainly in the kappa phase.