Browsing by Author "Caliskan, Necla"

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Adsorption of Zinc(Ii) on Diatomite and Manganese-Oxide Diatomite: a Kinetic and Equilibrium Study
(Elsevier, 2011) Caliskan, Necla; Kul, Ali Riza; Alkan, Salih; Sogut, Eda Gokirmak; Alacabey, Ihsan
The removal of Zn(II) ions from aqueous solution was studied using natural and MnO2 modified diatomite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. From the D-R model, the mean adsorption energy was calculated as >8 kJ mol(-1), indicating that the adsorption of Zn(II) onto diatomite and Mn-diatomite was physically carried out. In addition, the pseudo-first-order, pseudo-second-order and intraparticle diffusion models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (Delta H-0), Gibbs' free energy (Delta G(0)) and entropy (Delta S-0) were calculated for natural and MnO2 modified diatomite. These values showed that the adsorption of Zn(II) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously. (C) 2011 Elsevier B.V. All rights reserved.
Equilibrium and Kinetic Studies of the Adsorption of Zn(Ii) Ions Onto Natural and Activated Kaolinites
(Sage Publications inc, 2009) Kul, Ali Riza; Caliskan, Necla
The removal of Zn(II) ions from aqueous solution was studied using natural, thermally-activated and acid-activated kaolinite samples at different temperatures. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. The Langmuir constants for natural kaolinite were found to be negative whereas, for the other samples, the isotherm models gave a good fit. In addition, the pseudo-first-order and pseudo-second-order models were used to determine the kinetic data. The experimental data were well fitted by the pseudo-second-order kinetic model. Thermodynamic parameters such as the enthalpy (Delta H-0), Gibbs' free energy (Delta G(0)) and entropy (Delta S-0) were calculated for natural, thermally-activated and acid-activated kaolinite. These values showed that the adsorption of Zn(II) ions onto activated kaolinite was controlled by a physical mechanism and occurred spontaneously The process of adsorption was favoured at high temperatures, with the adsorption capacity of the acid-activated kaolinite being greater relative to that of natural and thermally-activated kaolinite at various temperatures.
The Inhibition Effect of Some Pyrimidine Derivatives on Austenitic Stainless Steel in Acidic Media
(Elsevier Science Sa, 2011) Caliskan, Necla; Akbas, Esvet
5-Benzoyl-4-(substitutedphenyl)-6-phenyl-3,4-dihydropyrimidine-2(1H)-(thio)ones (DHPMs) (I and II) were synthesized using the Biginelli three component cyclocondensation reaction of an appropriate arylaldehyde, and (thio) urea. The effect of these corrosion inhibitors on the corrosion of austenitic stainless steel in 0.5M H2SO4 has been studied by electrochemical methods using Tafel plot, linear polarization and electrochemical impedance spectroscopy at 298K. The inhibition efficiencies obtained from all the methods employed are in good agreement. The adsorption of the DHPMs onto the stainless steel surface was found to follow Langmuir and Dubinin-Radushkevich adsorption isotherm models. Negative values of Delta G(ads) in the acidic media ensured the Spontaneity Of the adsorption process. Results show DHPM I to be the best inhibitor with a mean efficiency of 91% at 2 x 10(-3) M additive concentration. (c) 2010 Elsevier B.V. All rights reserved.
Isotherm and Kinetic Studies of Pb(Ii) Adsorption on Raw and Modified Diatomite by Using Non-Linear Regression Method
(Parlar Scientific Publications (p S P), 2017) Sogut, Eda Gokirmak; Caliskan, Necla
This study presents the evaluation of the original diatomite (D-O) and manganese oxide modified (D-mn) diatomite used as adsorbents for Pb (II) removal from aqueous solution. The experimental data were fitted to the non-linear two parameter equation of Langmuir, Freundlich, Dubinin-Radushkevich, and non-linear three parameter equation of Redlich-Peterson, Sips and Toth Isotherms. The correlation coefficient (R-2), standard error (S.E) and Chi-square (x(2)) values were used to select the best theoretical isotherm. Adsorption mechanism of Pb(H) ion onto the D-O was explained by heterogeneous adsorption model while homogenous adsorption model was used to explain the adsorption on D-mn. Also, both adsorbents were observed to comply better with the three-parameter isotherms. Pseudo first-order, pseudo second-order, Elovich and intraparticle diffusion equations were used to describe the adsorption rate of Pb(II). The experimental data were well fitted by the pseudo second-order kinetic model. Thermodynamic parameters such as free energy (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees) showed spontaneous and endothermic in nature of adsorption for both of adsorbents.
The Natural Diatomite From Caldiran-Van (Turkey): Electroanalytical Application To Antimigraine Compound Naratriptan at Modified Carbon Paste Electrode
(Bentham Science Publ Ltd, 2010) Caliskan, Necla; Sogut, Eda; Saka, Cafer; Yardim, Yavuz; Senturk, Zuhre
This paper is the first report describing the characterization of local diatomite of Caldiran-Van region (Eastern Anatolia, Turkey). Special attention was paid to the ability of its electroanalytical performance at modified electrodes and to the potential application of diatomite-modified electrode. For this purpose, the determination of Naratriptan which is a novel oral triptan (5-hydroxytryptamine receptor agonist) in migraine treatment, by means of a carbon paste electrode modified with 10% (w/w) of diatomite was studied using cyclic and square-wave voltammetry. The experimental conditions that affect the electrode reaction process were studied in terms of pH of the supporting electrolyte, scan rate, accumulation variables, modifier composition and square-wave parameters. Using square-wave stripping mode, the drug yielded a well-defined voltammetric response in Britton-Robinson buffer, pH 4.0 at 0.84 V (vs Ag/AgCl) (a pre-concentration step being carried out with an open circuit at 120 s). The process could be used to determine Naratriptan concentrations in the range 5x10(-7)-9x10(-7) M, with a detection limit of 1.25x10(-7) M (46.5 mu g L(-1)). The applicability of the method to spiked human urine samples was illustrated.
Removal of Cu(Ii) and Cd(Ii) Ions From Aqueous Solutions Using Local Raw Material as Adsorbent: a Study in Binary Systems
(desalination Publ, 2017) Caliskan, Necla; Sogut, Eda Gokirmak; Savran, Ali; Kul, Ali Riza; Kubilay, Senol
The purpose of this study is to examine the interaction of Cu(II) and Cd(II) ions in solution with the local raw clayey material of Tilkitepe located in the eastern shore of Lake Van in East Anatolia (Turkey). This material was used as an adsorbent without any chemical or physical treatment and was characterized by X-ray fluorescence, X-ray diffraction, scanning electron microscope, Fourier transform infrared and differential thermal analysis-thermogravimetric analyses. Langmuir, Freundlich, Dubinin-Kaganer-Radushkevich, Temkin and Harkins-Jura non-linear adsorption isotherm models were applied to the experimentally obtained adsorption data and the isotherm constants were calculated. The highest R-2 values for adsorption of both ions in the binary system were obtained by applying the experimental data to the Freundlich isotherm model. In binary system, the experimental adsorption capacities for Cu(II) and Cd(II) ions obtained by kinetic data were 52.631 and 44..843 mg g(-1) at 600 mg L-1 initial metal ion concentrations, respectively In the competitive adsorption, the affinity of Cu(II) toward the adsorbent was much higher than that of the Cd(II). Adsorption kinetics was evaluated using the pseudo-first-order, pseudo-second-order, intraparticle diffusion, Avrami and mass transfer kinetic models. The experimental data proved a closer fit to the pseudo-second-order model. Thermodynamic parameters such as enthalpy (Delta H degrees), Gibbs free energy (Delta G degrees) and entropy (Delta S degrees) were calculated using adsorption isotherms obtained at different temperatures. The results show that the adsorption is spontaneous and controlled by a physical mechanism.
Removal of Lead, Copper and Cadmium Ions From Aqueous Solution Using Raw and Thermally Modified Diatomite
(desalination Publ, 2017) Sogut, Eda Gokirmak; Caliskan, Necla
In this study, raw diatomite was purified by thermal treatment in order to improve the adsorption capacity of diatomite. The prepared calcined diatomite samples were characterized by the X-ray diffraction (XRD), scanning electron microscope (SEM) and Fourier transformation infrared (FT-IR) analysis techniques. The raw and thermally modified diatomite at 500 degrees C was tested for the adsorption of Pb(II), Cu(II) and Cd(II) from aqueous solutions. Adsorption experiments were performed under batch process, using metal ions initial concentration, contact time and temperature as variables. The linear Langmuir, Freundlich and Dubinin-Radushkevich (D-R) adsorption equations were applied to describe the equilibrium isotherms. Equilibrium studies showed that thermally modified diatomite has a higher removal capacity for Pb(II), Cu(II) and Cd(II) from water than untreated diatomite. The kinetic data were evaluated using the pseudo-first-order, pseudo-second-order and intraparticle diffusion kinetic equations. The experimental data proved a closer fit to the pseudo-second-order model. Thermodynamic parameters such as the enthalpy (Delta H-0), Gibbs' free energy (Delta G(0)) and entropy (Delta S-0) were calculated for raw and thermally modified diatomite. These values showed that the adsorption of Pb(II), Cu(II) and Cd(II) ions onto diatomite samples was controlled by a physical mechanism and occurred spontaneously.