Browsing by Author "Gur, Aycan"

Now showing 1 - 14 of 14

Determination of Mass Attenuation Coefficients of Concretes Containing Ulexite and Ulexite Concentrator Waste
(Pergamon-elsevier Science Ltd, 2013) Oto, Berna; Gur, Aycan
Purposes of this study are to examine photon attenuation properties of concretes including ulexite and ulexite concentrator waste and to present an alternative shielding material in order to decrease the intensity of gamma radiation. In order to investigate the radiation transmission of these concretes, mass attenuation coefficients at 59.54 and 80.99 key photons energies were measured by executing a transmission geometry with NaI(Tl) scintillation detector and calculated by WinXCom computer program. (C) 2013 Elsevier Ltd. All rights reserved.
Determination of the Optimum Conditions for Boric Acid Extraction From Ulexite in Perchloric Acid Solutions
(Asian Journal of Chemistry, 2008) Gur, Aycan; Yildiz, Adnan; Celik, Hilal; Selcuk, Ahmet
In this study, Taguchi method was used to determine optimum conditions for the dissolution of ulexite in perchloric acid slutions. For optimization process; solid-to-liquid ratio, reaction time, particle size and acid concentration were chosen as parameters. In the experiment, stirring speed and reaction temperature were kept as constant. The ranges of experimental parameters-were between 0.1-0.2 g/cm(3) for solid-to-liquid ratio, 1.5-2.5 M for acid concentration, 165.0-512.5 mu m for particle size and 12-36 min for reaction time. In the end of the experimental sections the optimum conditions were determined as 0.1 g/mL for solid to liquid ratio; 215 mu m for particle size; 24 min for reaction time; 500 rpm for stirring speed; 30 degrees C for reaction temperature and 2 mol/dm(3) for acid concentration. Under these conditions, it was found that the boric acid extraction from ulexite was reached a value of 99 %.
Dissolution Kinetics and Mechanism of Pandermite in Acetic Acid Solutions
(Academic Journals, 2010) Gur, Aycan; Caglayan, Firat; Yildiz, Adnan; Selcuk, Ahmet
In this study, the dissolution kinetics and mechanism of pandermite mineral was investigated using a batch reactor employing the parameters of particle size, acid concentration, solid/liquid ratio, stirring speed and reaction temperature. From experimental data, it was determined that the conversion rate of pandermite to boric acid was increased with decreasing particle size, solid/liquid ratio and increasing reaction temperature. Conversion rate increased up to 3 M, acid concentration then decreased with increasing acid concentration. It was observed that there was no important effect of stirring speed on the dissolution rate. Furthermore, it was observed that the dissolution mechanism was dependent on acid concentration due to restriction of dissolution in acetic acid solutions. The dissolution rate of pandermite mineral in acetic acid solution was examined according to homogeneous and heterogeneous chemical reaction model. It was determined from graphical and statistical methods that the reaction kinetics fitted to model in the form of first order pseudo homogeneous model [- ln (1 - X)] = kt and activation energy for the dissolution process was found to be 28.496 kj/mol. A mathematical model, which indicated the dissolution process was established.
Dissolution Kinetics of Calcined Ulexite in Ammonium Chloride Solutions at High Solid-To Ratios
(Peking Univ Press, 2006) Gur, Aycan
The dissolution kinetics of calcined ulexite in ammonium chloride solutions at high solid-to-liquid ratios were investigated. In the experiments, calcination temperature, solution concentration, reaction temperature, and prehydration were chosen as parameters. It was observed that the dissolution rate increased with increasing calcination temperature, solution concentration, and reaction temperature, whereas it was not affected by pre-hydration. Employing graphical and statistic methods, the dissolution rate, based on homogeneous reaction model, can be given as: (1X(B2O3))(-1)-1= k(c(NH4Cl))(1.982)t. The activation energy for the dissolution of the ulexite sample calcined at 160 degrees C was found to be 84.04 kJ . mol(-1).
Exploring Thermodynamics and Kinetic Parameters of Immobilized Catalase Enzyme Via Adsorption on Krill Clay
(desalination Publ, 2017) Nas, Mehmet Salih; Gur, Aycan; Gur, Tugba; Yonten, Vahap
The thermodynamic parameters and immobilization kinetics of catalase enzyme via adsorption onto krill clay were performed in aqueous solution in batch system. The adsorbent was characterized by X-ray fluorescence, scanning electron microscope and Brunauer-Emmett-Teller N-2 adsorption measurements. The effect of some parameters to the adsorption process such as contact time, stirring speed, initial enzyme concentration, initial ionic strength, temperature and pH were analyzed. Maximum adsorption capacity (q(m)) showed a great dependence on pH and initial enzyme concentration. It was found at pH 5.5, and initial enzyme concentration, 0.0075 g L-1 values. Pseudo-first-order, pseudo-second-order and intraparticle diffusion were used to fit the kinetics data on kinetic models. Furthermore, thermodynamic activation parameters such as enthalpy, entropy, Gibbs free energy and activation energy (Delta H degrees, Delta S degrees, Delta G degrees and E-a) which reveal that catalase enzyme adsorption occur spontaneously and in endothermic nature were determined. The obtained results confirmed that the applicability of krill clay is an efficient immobilizing supporter for catalase enzyme and krill clay material can be used as a very effective adsorbent in immobilization of this enzyme from aqueous solutions.
Investigation of Adsorption Kinetics and Removal of Copper (Ii) and Zinc From Aqueous Solution by Bardakci Clay
(Amer Chemical Soc, 2009) Gur, Aycan; Y'ld'z, Ardnan; Alkan, Erkan; Gur, Tugba
Investigation of Kinetics and Mechanism of Priceite Leaching in Sulphuric Acid Solutions
(oficyna Wydawnicza Politechniki Wroclawskiej, 2015) Gur, Aycan
The leaching kinetics and mechanism of priceite having the formula of 4CaO center dot 5B(2)O(3)center dot 7H(2)O was investigated in sulphuric acid solutions. For the dissolution process, the effects of reaction temperature, sulphuric acid solution concentration, solid/liquid ratio, particle size, and stirring speed were investigated as effective parameters for the experiments. The experimental data indicated that the dissolution rate increased with the increasing reaction temperature, the decreasing particle size, and the solid/liquid ratio. The conversion rate increased up to 1.0 mol/dm(3) with the increasing acid concentration, and then decreased with the increasing acid concentration over concentrations of 1 mol/dm3. It was also determined that the stirring speed had no significant effect on the dissolution rate. The dissolution process of priceite in sulphuric acid solution was tested with regard to heterogeneous and homogeneous reaction models, and it was found that the dissolution rate was controlled by first order pseudo-homogeneous reaction model. The activation energy of the dissolution process was determined as 26.07 kJ.mol(-1). The results were evaluated graphically and statistically. The experimental data were found to fit well with the mathematical model.
A Kinetic Study on Leaching of Colemanite in Ammonium Nitrate Solutions
(Chinese Chemical Soc, 2008) Gur, Aycan
The dissolution of colemanite in aqueous ammonium nitrate solutions was investigated in a batch reactor in terms of stirring speed, particle size, reaction temperature, solid-to-liquid ratio and solution concentration. The results showed that the dissolution rate increased with increasing temperature and concentration of ammonium nitrate solution as well as decreasing particle size and solid-to-liquid ratio, while no important effect of stirring speed was observed on dissolution rate. Colemanite could be dissolved up to 100 percent in aqueous ammonium nitrate solutions. The dissolution kinetics of colemanite was examined according to heterogeneous and homogeneous reaction models. The experimental data revealed high activation energy, indicating that the dissolution rate based on heterogeneous reaction models can be expressed as 1-(1-X)(1/3)=3.28x10(4).D-0.653 7.C-1.295 8.(S/L)(-0.490 9).e(-41.40)(RT).t. The activation energy of the process was found to be 41.40 kJ.mol(-1).
Leaching Kinetics of Colemanite in Perchloric Acid Solutions
(Soc Chemical Eng Japan, 2008) Gur, Aycan; Alkan, M. Emin
Boron minerals are crucial For our world. Colemanite, which is one or the most widely available boron minerals, has the chemical formula of Ca-2 center dot 5B(6)O(7)center dot 5H(2)O and a monoclinic crystal structure. The parameters selected for this study are particle size, reaction temperature, acid concentration, solid to liquid ratio and stirring speed. The dissolution rate of colemanite was found to increase with decreasing particle size and solid to liquid ratio, with increasing reaction temperature and acid concentration, while if was not affected by stirring speed. A model equation was constructed for the process. Employing graphical and statiscal methods, the dissolution rate, based on heterogeneous reaction model and evaluation Of the experimental data and the mathematical model revealed that the dissolution process was found to be controlled by chemical reaction and the activation energy of this process was estimated to be 46.475 kJ mol(-1). The mathematical model to represent the kinetics of this process can be expressed as: 1 -(1-X)(1/3) = 7.73 x 10(5) x (Rp)(-0.2735) x (CA)(0.1891) X (S/L)(-0.2318) X e(-5589.965f) x t.
Leaching Kinetics of Tincal in Ammonium Chloride Solutions
(Chinese Chemical Soc, 2009) Gur, Aycan; Kandilcik, Meltem
The effects of reaction temperature, solution concentration, solid to liquid ratio, particle size and stirring speed were investigated on leaching kinetics of tincal, sodium tetraborate decahydrate(Na2B4O7 center dot 10H(2)O), in ammonium chloride solutions. The results showed that the dissolution rate increased with increasing solution concentration and reaction temperature, and increased with decreasing particle size and solid to liquid ratio. It was also determined that stirring speed had no significant effect on dissolution rate. The dissolution process was examined according to homogeneous and heterogeneous reaction kinetic Model. The dissolution rate was found to be based on the first order pseudo homogeneous reaction model. The activation energy of the dissolution of tincal in ammonium chloride solutions was determined to be 82.73 kJ . mol(-1).
A Novel Ph-Responsive P(aam-co-metac)/Mmt Composite Hydrogel: Synthesis, Characterization and Its Absorption Performance on Heavy Metal Ions
(Taylor & Francis inc, 2015) Ilgin, Pinar; Durak, Halil; Gur, Aycan
In this study, the preparation and characterization of the novel pH-sensitive poly (acrylamide-co-2-methacryloyloxy) ethyltrimethyl ammonium chloride)/montmorillonite (p(AAm-co-METAC)/MMT) composite superabsorbent hydrogels and their selective metal absorbtion properties were investigated. The adsorption of metal ions is highly dependent on the initial feed concentration, contact time, pH of the metal solution and adsorbent doses. The results were analyzed both by the Langmuir and Freundlich isotherms and the adsorption is found to follow pseudo-second-order kinetics. The adsorption capacity followed the order Zn2+>Ni2+>Cu2+>Pb2+ and the maximum adsorption capacities of them were similar to 320, 285, 240 and 120 (mg g(-1)), respectively.
Photon Attenuation Properties of Concretes Containing Magnetite and Limonite Ores
(oficyna Wydawnicza Politechniki Wroclawskiej, 2017) Gur, Aycan; Artig, Birol; Cakir, Tahir
In this study, gamma shielding properties of concretes containing magnetite and limonite ores at different ratios (5%, 10%, 15%, 20%, and 30%) were investigated by using a Co-60 (1.25 MeV) radioactive source which was built in Thratron 1000E (TM) device used for radiotherapy purposes. Then, the photon transmission values (I/I-0) were measured by 0.6 cm(3), farmer type, PTW (TM) ion chamber. The dose readings (I-0 and I), made by PTW (TM) Unidose Electrometer, were used to calculate the linear attenuation coefficient (mu, cm(-1)), the mean free path (lambda, cm), and the mass attenuation coefficient (mu(rho), cm(2)/g) by the Lambert equations, and the results were compared with the calculations obtained using the WinXCom computer program. The findings from this study revealed that the concretes containing magnetite and limonite ores were more effective than the ordinary concrete in the attenuation of gamma rays. It was determined that the values of the mean free path decreased with the increasing concentrations of magnetite and limonite ores while the linear attenuation coefficients for 10 concrete blocks increased with the increasing magnetite and limonite ore concentrations. A comparison of the theoretical values obtained from the WinXCom computer program and the experimental results revealed a good level of conformity.
Photon Attenuation Properties of Some Concretes Containing Barite and Colemanite in Different Rates
(Pergamon-elsevier Science Ltd, 2013) Oto, Berna; Gur, Aycan; Kacal, Mustafa Recep; Dogan, Bekir; Arasoglu, Ali
Radiation shielding properties of concretes containing barite and colemanite in different rates were evaluated by using Ba-133 (80.99 and 303 key) and Am-241 (59.54 key) radioactive sources. Gamma rays were counted by a NaI(TI) detector with a resolution of 122 keV at 662 key. The study reveals that the concretes under research are effective than ordinary concrete for the attenuation of gamma rays. It was determined that the values of mean free path decreased with the increasing concentration of barite and colemanite and the linear attenuation coefficients increased with the increasing concentration of barite and colemanite in the concrete. Theoretical values were obtained by using Penelope and WinXCom computer programs and these were compared with the experimental results. (C) 2012 Elsevier Ltd. All rights reserved.
Synthesis and Characterization of a New Fast Swelling Poly(epma-Co as Superabsorbent Polymer for Anionic Dye Absorbent
(Springer, 2015) Ilgin, Pinar; Gur, Aycan
A novel superabsorbent polymer poly(2,3-epoxypropyl methacrylate-co-2-(methacryloyloxy)ethyl trimethyl ammonium chloride), p(EPMA-co-METAC), was prepared simply by free radical aqueous copolymerization reaction of 2,3-epoxypropyl methacrylate (EPMA) and 2-(methacryloyloxy)ethyl trimethyl ammonium chloride (METAC) using N,N'-methylenebisacrylamide (MBA) as a cross-linking agent and ammonium persulfate (APS) as a free radical initiator. The chemical structures of hydrogel were confirmed by FTIR and elemental analysis. The swelling behavior of the hydrogel samples was investigated under different experimental conditions such as time, pH, ionic strength and different media. In the second part of this study, the superabsorbent hydrogels were tested for the removal of an anionic dye, i.e., Coomassie Brilliant Blue G-250 (CBB), a molecule having a marked amphiphilic character, from aqueous environment. Finally, isotherm adsorption data of dye on hydrogels were modeled according to Langmuir and Freundlich isotherm models. The results revealed that the experimental data was correlated by both of them. Also, the kinetic parameters for the adsorption process of the dye were investigated based on the different kinetic models such as pseudo-first-order and second-order models and the adsorption kinetics followed well the pseudo-second-order model. Novel superabsorbent polymer samples also show good anionic dye absorbency and excellent swelling ability. As a result, p(EPMA-co-METAC) hydrogel appeared to be suitable for the removal of CBB from aqueous solutions.