Yazar "Gurten, AA" seçeneğine göre listele
Listeleniyor 1 - 5 / 5
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Adsorption of indole and 2-methylindole on ligand-exchange matrix(ACADEMIC PRESS INC ELSEVIER SCIENCE, 2004) Erciyes, N; Gurten, AA; Abdullah, MI; Ayar, AThe adsorption of indole and its 2-methyl derivative from aqueous solutions onto cobalt(II)-carboxylated diaminoethane sporopollenin (CDAE-sporopollenin) was studied using a fixed-bed column at 25 +/- 0.1 degreesC. Minicolumn adsorption studies showed that the breakthrough and the total adsorption capacities of CDAE-sporopollenin in the concentration range we have studied increased with increasing external ligand concentration. The characteristics of the adsorption process were investigated using Scatchard plot analysis, where the equilibrium binding data for indole on ligand exchanger gave rise to a linear plot. However, for 2-methylindole, divergence from the Scatchard plot was evident, consistent with the participation of secondary equilibrium effects in the adsorption process. The adsorption behaviors of ligands on CDAE-sporopollenin were expressed by both the Langmuir and Freundlich isotherms. The adsorption isotherm data for these ligands on the resin can be satisfactorily fitted to the Freundlich isotherm within the concentration range studied. However, in the case of 2-methylindole, the experimental data did not fit the Langmuir model, especially when a high ligand concentration range is used; this is probably due to the nonspecific interactions between the ligand exchange matrix and the methyl group present. Ligand adsorption constants and correlation coefficients for the ligands were calculated from the Langmuir and Freundlich isotherms. (C) 2004 Elsevier Inc. All rights reserved.Öğe Determination of the rate control step of purin and pyrimidine bases adsorption on cobalt(II) - CDAE-sporopollenin(ELSEVIER SCIENCE BV, 2003) Ayar, A; Gurten, AAIn this work, adsorption kinetics of nucleic acid bases and nucleosides as ligands on cobalt(II)-carboxylated diaminoethyl sporopollenin (CDAE-sporopollenin) have been performed using continuous column runs. Adsorption rate measurements were carried out by using a-UV-Vis spectrophotometer, and rate control step of the adsorption process was determined. The adsorption of nucleic acid bases and nucleosides from solutions of different initial concentrations onto resin was measured as a function of time at 25degreesC. The results show that type of ligand has a great effect on ligand adsorption behaviour. External ligand concentrations play a significant role on adsorption rate of nucleic acid bases. The homogeneous diffusion model (HDM) is applied to the experimental breakthrough data. In all of the concentration range of adenine and uracil (nucleic acid bases), the graphs of -ln[l - U(alpha)] versus t were a straight line, which suggests that fractional attainment of equilibrium adsorption under film diffusion control is observed. On the contrary, adenosine and uridin (nucleosides), the graphs were not a straight line and have underwent adsorption under particle diffusion control. (C) 2003 Elsevier B.V. All rights reserved.Öğe Effect of polyvinylpyrrolidone on the corrosion resistance of steel(ELSEVIER SCI LTD, 2005) Gurten, AA; Erbil, M; Kayakirilmaz, KThe effect of polyvinylpyrrolidone (PVP) on the corrosion resistance of steel reinforced concrete was assessed by measuring the corrosion potential, linear polarization resistance and AC impedance during 60 days immersion in NaCl and NaCl + PVP Solutions, Polarization resistance (R-p) values of PVP added reinforced concrete were much higher than those without PVP. The relationship between corrosion potential and linear polarization resistance was analysed. Results from corrosion potential measurements were well comparable with the linear polarization resistance data, AC impedance spectra revealed that the resistance of PVP mixed electrodes was also quite higher than the other electrodes. The mechanical properties of concrete were measured. It wits observed that the compressive strength of concrete had increased approximately 44% in the specimens containing PVP. (c) 2005 Elsevier Ltd. All rights reserved.Öğe Removal of aniline from aqueous solution by PVC-CDAE ligand-exchanger(ELSEVIER SCIENCE BV, 2005) Gurten, AA; Ucan, S; Ozler, MA; Ayar, AThe adsorption of aniline from aqueous solutions onto cobalt(II)-poly(vinyl chloride)-carboxylated diaminoethane (PVC-CDAE) resin has been studied using a mini-column apparatus at 25 +/- 0.1 degrees C. First of all, experimental data obtained from the breakthrough curves were tested by using the Scatchard plot analysis, to have a preliminary prediction about the types of interaction of the resin with aniline. Our aim was to determine the model which best describes the experimental data. The aspect of the Scatchard plot indicated that the aniline adsorption did not follow the Langmuir model and the presence of two types of binding sites for aniline on the resin. However. the dynamics of aniline uptake were represented by the Freundlich model reasonably well. The kinetics of aniline adsorption from aqueous solution on the cobalt(II)-PVC-CDA-E have also been tested using continuous column runs and rate-controlling step of the process was determined. In this study, homogeneous diffusion model was adapted to a column system to describe the change in the aniline concentration at the column exit begining from breakthrough point as a function of time. Kinetic studies revealed that the rate-controlling step of the aniline adsorption was predominately film diffusion controlled rather particle diffusion. (c) 2005 Elsevier B.V. All rights reserved.Öğe The primary study on the effects of primer alcohols on the hydrogen evolution reaction on silver electrode(PERGAMON-ELSEVIER SCIENCE LTD, 2003) Gurten, AA; Kayakirilmaz, K; Yazici, B; Erbil, MThe cathodic behaviour of silver in 0.01 M NaCl and 0.01 M NaCl + 1.0 alcohols which are methyl, ethyl and propyl alcohols is investigated at pH 3 and 5 by means of electrolysis. The experimental (E-exp) and theoretical (E-rev) discharge potential are determined in all solutions between Pt and Ag electrodes. The cathodic and anodic overpotentials on silver cathode were determined using a platinum anode. The hydrogen gas is produced on constant potentials (5.00 or 10.00 V) on silver cathode. It is observed that the presence of alcohols decreases the anodic overpotential and increases the hydrogen yield in NaCl solution. (C) 2003 International Association for Hydrogen Energy. Published by Elsevier Science Ltd. All rights reserved.
