Chemistry / Kimya

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End date: 2019Institution Author: search.filters.institutionAuthor.Polat, Hürriyet

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Now showing 1 - 10 of 23
  • Article
    Toz Kömürlerin Zenginleştirilmesinde Yağ Aglomerasyonu Yöntemi ve Yenilikler
    (İstanbul Üniversitesi, 2010) Kılınç Aksay, Ece; Polat, Hürriyet; Arslan, Vedat; Polat, Hürriyet; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Kömürün üretim teknolojisindeki gelişmeler, kömür üretimi sürecinde oluşan ince boyutlu (toz) kömürün miktarını arttırmaktadır. Bu tür toz kömürlerin zenginleştirilerek değerlendirilmesi, hem madencilik maliyetini azaltmakta, hem de önemli bir çevre problemini ortadan kaldırmaktadır. Ayrıca eneıjiye olan gereksinim, her geçen gün teknolojinin ilerlemesiyle doğru orantılı olarak artmaktadır. Dolayısıyla, çevre problemi yaratan sınırlı enerji kaynaklarının, çevre dostu yöntemlerle değerlendirilmesi gerekmektedir. Yağ aglomerasyonu yöntemi, bu yöntemlerden biridir. Özellikle çok ince boyutlu kömür tanelerinin kazanılmasında flotasyona alternatif bir yöntemdir. Bu yöntem, yüksek devirli karıştırıcılar kullanılarak, kömür tanelerinin yağ tarafından ıslatılması ve birbirlerine bağlanarak iri taneler haline getirilmesi prensibine dayanır. Yağın, kömür-su sistemine verilmeden önce, su içerisinde gerek mekanik karıştırma ile gerekse çeşitli yüzey aktif reaktiflerin kullanımı ile emülsiye edilmesi (dağıtılması) veya kömür yüzeyinin yine çeşitli yüzey aktif reaktiflerle hava/yağ sever özellik kazandırılması, yöntemin başarısını hem teknik hem de ekonomik yönden arttırmaktadır. Yağ aglomerasyonu yöntemindeki bu yenilikler, günümüzde linyit gibi düşük kaliteli kömürlerin bile, bu yöntem ile başarıyla zenginleştirilebilmesine olanak sağlamaktadır. Bu makalede, yağ aglomerasyonu yönteminin temel prensipleri, yöntemi etkileyen parametreler ve farklı tip kömürler için yöntemin uygulamasına yönelik araştırmalar detaylı olarak açıklanmış, yöntem ile ilgili yenilikler tartışılmıştır.
  • Article
    Solunabilir Tozun Su Spreyleri Kullanılarak Bastırılmasında Son Gelişmeler
    (2000) Polat, Hürriyet; Polat, Mehmet; Polat, Mehmet; Polat, Hürriyet; Gürgen, Sabit; 04.01. Department of Chemistry; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Türkiye'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; Polat, Mehmet; Polat, Hürriyet; İpekoğlu, Üner; 04.01. Department of Chemistry; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Effect 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
    Use of Ion Flotation To Remove Copper From Waste Waters
    (2006) Erdoğan, Demet; Polat, Hürriyet; Polat, Hürriyet; İpekoğlu, Üner; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Flotation studies were carried out to investigate the removal of copper from wastewaters. Various parameters such as pH, surfactant and frother concentrations and airflow rate were tested to determine the optimum flotation conditions. Sodium dodecyl sulfate and Hexadecyltrimethyl ammonium bromide were used as collectors. Recoveries as high as 90% could be to obtained under optimum conditions.
  • Article
    Citation - WoS: 2
    Reduction of Carbon Dioxide During the Synthesis of Metal Nano-Particles in Water
    (Elsevier Ltd., 2003) Polat, Hürriyet; Polat, Hürriyet; Cohen, H; Meyerstein, D; Rusonik, I.; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    An effort was made to synthesize "carbon-free" metal (Fe-0, Co-0, Ni-0) nano-particles via the reduction of their salts with BH4- in aqueous solutions. Surprisingly it was found that when the synthesis is carried out in the presence of CO2, e.g., in aerated solutions, the CO2 is catalytically reduced by BH(4)(-)on the surface of the metal particles. Carbon-free metals can be prepared by reduction under an inert atmosphere. Thus metal surfaces might have acted as catalysts for CO2 fixation, probably via the initial formation of carbon clusters, in the reductive atmosphere in the prebiotic era. (C) 2003 Elsevier B.V. All rights reserved.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Tannery Wastewater Sediments Produced by Clinoptiolite/Polyacrylamide-aided Flocculation as a Clay Additive in Brick Making
    (Springer Verlag, 2017) Köseoğlu, Kemal; Polat, Hürriyet; İsrail, L. İ.; Polat, Hürriyet; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Toxic tannery wastewater(s) (TWW) pose(s) a great risk to the environment. This study explores the potential of mitigating the harmful effects of TWW through sedimentation using clinoptiolite in the presence of various anionic, cationic and non-ionic flocculants with different molecular weights and charge densities followed by encapsulation in a brick structure for stability. Compressive strength (CS), size reduction after firing (SRAF), water absorption (WA) and colouring parameters of bricks were determined. X-Ray diffraction (XRD) and scanning electron microscopy (SEM)-energy dispersive X-ray (EDX) analyses were conducted on brick bodies. Kinetic leaching experiments were conducted for possible heavy metal release from the bricks. Bricks containing 10 wt% leather waste and 5 wt% clinoptiolite sintered at 800 °C instead of 920 °C possessed similar properties to the standard brick (SB).
  • Article
    Citation - WoS: 13
    Citation - Scopus: 15
    Ancillary Effects of Surfactants on Filtration of Low Molecular Weight Contaminants Through Cellulose Nitrate Membrane Filters
    (Elsevier Ltd., 2016) Olcay, Aybike Nil; Polat, Mehmet; Polat, Hürriyet; Polat, Mehmet; 04.01. Department of Chemistry; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Removal of contaminants with low molecular weight (<800 Dalton) requires the use of advanced separation techniques such as ultrafiltration (UF) or micellar enhanced ultrafiltration (MEUF). However, surface active agents invariably co-exist in waste waters along with these contaminants or they may be added intentionally as part of the separation process as in the case of MEUF. Though it is quite likely that both the filter medium and the contaminants would interact with the surfactant molecules or their micelles, there is not sufficient emphasis in the literature on the concomitant aspects of such interactions.The ancillary effects created by anionic (sodium dodecyl sulfate, SDS), cationic (hexadecyltrimethyl ammonium bromide, CTAB) and non-ionic (ethoxylated octylphenol, TX-100) surfactants on the mechanism and efficiency of the filtration process were investigated in this study. Methylene blue (MB) and cellulose nitrate membrane (CNM) filters were employed as model retentate and the separation medium. A combination of surface tension, contact angle and charge measurements demonstrated that the addition of surfactants had a remarkable effect on the filtration outcome. The effect depended on both the type and concentration of the surfactant and was manifested mainly through the creation of MB-surfactant entities which acted differently than the MB alone; but more importantly, through the interactions of the surfactant molecules/micelles and the MB-surfactant pairs with the separation membrane.
  • Article
    Citation - WoS: 140
    Citation - Scopus: 171
    Physicochemical Characterization of Chitosan Extracted From Metapenaeus Stebbingi Shells
    (Elsevier Ltd., 2011) Küçükgülmez, Aygül; Çelik, Mehmet; Polat, Hürriyet; Şen, Didem; Polat, Hürriyet; Kadak, Ali Eslem; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this study, chitosan was extracted from Metapenaeus stebbingi shells. In order to determine physicochemical characteristics of the extracted chitosan, the yield, moisture and ash contents, degree of deacetylation, molecular weight, water and fat binding capacities, apparent viscosity and colour properties were measured using a variety of techniques including Fourier transform infrared spectroscopy, scanning electron microscopy and X-ray diffraction. In addition, the physicochemical characteristics of the chitosan extracted from M. stebbingi shells were compared to commercial chitosan. The degree of deacetylation was calculated by the titration method and elemental analysis. The molecular weight was determined by viscosimetric methods. The results of the study indicate that shrimp shells are a rich source of chitosan as 17.48% of the shell's dry weight is consisted of this material. Extracted chitosan exhibited a lower molecular weight, higher degree of deacetylation, higher viscosity and higher water and fat binding capacities compared to the commercial chitosan.
  • Article
    Citation - WoS: 21
    Citation - Scopus: 23
    Adsorption of Methylene Blue From Aqueous Solution on High Lime Fly Ash: Kinetic, Equilibrium, and Thermodynamic Studies
    (Taylor and Francis Ltd., 2012) Keleşoğlu, Serkan; Polat, Hürriyet; Kes, Mürşide; Sütçü, Leman; Polat, Hürriyet; 04.01. Department of Chemistry; 04. Faculty of Science; 01. Izmir Institute of Technology
    Kinetic, equilibrium, and thermodynamic studies were performed for the batch adsorption of methylene blue (MB) on the high lime fly ash as a low cost adsorbent material. The studied operating variables were adsorbent amount, contact time, dye concentration, and temperature. The kinetic data were analyzed using the pseudo-first order and pseudo-second order kinetic models and the adsorption kinetic was followed well by the pseudo-second order kinetic model. The equilibrium data were fitted with the Freundlich, Langmuir, and Dubinin Radushkevich (D-R) isotherms and the equilibrium data were found to be well represented by the Freundlich and D-R isotherms. Based on these two isotherms MB is taken by chemical ion exchange and active sites on the high lime fly ash have different affinities to MB molecules. Various thermodynamic parameters such as enthalpy of adsorption (ΔH°), free energy change (ΔG°), and entropy change (ΔS°) were investigated. The positive value of ΔH° and negative value of ΔG° indicate that the adsorption is endothermic and spontaneous. The positive value of ΔS° shows the increased randomness at the solid-liquid interface during the adsorption. A single-stage batch adsorber was also designed based on the Freundlich isotherm for the removal of MB by the high lime fly ash. © 2012 Copyright Taylor and Francis Group, LLC.
  • Article
    Citation - WoS: 23
    Citation - Scopus: 24
    Analytical Solution of Poisson-Boltzmann Equation for Interacting Plates of Arbitrary Potentials and Same Sign
    (Elsevier Ltd., 2010) Polat, Mehmet; Polat, Hürriyet; Polat, Mehmet; Polat, Hürriyet; 04.01. Department of Chemistry; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Efficient calculation of electrostatic interactions in colloidal systems is becoming more important with the advent of such probing techniques as atomic force microscopy. Such practice requires solving the nonlinear Poisson-Boltzmann equation (PBE). Unfortunately, explicit analytical solutions are available only for the weakly charged surfaces. Analysis of arbitrarily charged surfaces is possible only through cumbersome numerical computations. A compact analytical solution of the one-dimensional PBE is presented for two plates interacting in symmetrical electrolytes. The plates can have arbitrary surface potentials at infinite separation as long they have the same sign. Such a condition covers a majority of the colloidal systems encountered. The solution leads to a simple relationship which permits determination of surface potentials, surface charge densities, and electrostatic pressures as a function of plate separation H for different charging scenarios. An analytical expression is also presented for the potential profile between the plates for a given separation. Comparison of these potential profiles with those obtained by numerical analysis shows the validity of the proposed solution. © 2009 Elsevier Inc. All rights reserved.