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Öğe Adsorption of chromium(VI) metal ions from aqueous solution using hexagonal ZnO particles: Equilibrium, kinetic and thermodynamic modelling studies(Wiley, 2014) Erduran, Nuran; Gokgoz, Murat; Ada, KezbanZinc oxide powders having hexagonal plate particles were prepared by homogeneous precipitation from boiling aqueous solutions that contained excess urea and 0.075 (Z075) and 0.300 (Z300) M Zn2+. The equilibrium, kinetic and thermodynamics of the adsorption of chromium (VI) from aqueous solution onto Z075 and Z300 were investigated. Thermodynamic parameters and K-# equilibrium constant of activation were calculated. Langmuir, Temkin and Dubinin-Radushkevich (D-R) isotherm models were used to describe the adsorption of Cr(VI) onto ZnO powders. The monomolecular adsorption capacity of Z075 and Z300 was determined as 980 and 1050mgg(-1) for Cr(VI), respectively.Öğe Adsorption of Remazol Brilliant Blue R using ZnO fine powder: Equilibrium, kinetic and thermodynamic modeling studies(Elsevier, 2009) Ada, Kezban; Ergene, Aysun; Tan, Sema; Yalçın, EmineZinc oxide powders with six-sided flake-like particles were prepared by homogeneous precipitation from boiling aqueous solutions that contained excess urea and 0.075 (Z075) and 0.300 (Z300) M Zn2+. The average sizes of the particles are 37 and 46 mu m, while the average sizes of the crystals are similar to 45 for Z075 and Z300 at 1000 degrees C. Equilibrium, kinetic and thermodynamic studies were carried out for the adsorption of RBBR dye from aqueous solution using both types of ZnO in the form of fine powders. The effects of pH, initial dye concentration, contact time and temperature of solution on the adsorption were studied. Langmuir, Temkin and Dubinin-Radushkevich (D-R) isotherm models were used to describe the adsorption of RBBR onto ZnO powders. The Langmuir and D-R isotherm models fit the equilibrium data better than the Temkin isotherm model. The monomolecular adsorption capacity of Z075 and Z300 was determined to be 190 and 345 mg g(-1) for RBBR, respectively. The Lagergren first-order, Ritchie second-order kinetic and intra-particle diffusion models were used for the adsorption of the dye onto ZnO powders. The Ritchie second-order model was suitable for describing the adsorption kinetics for the removal of RBBR front aqueous solution onto Z075 and Z300. Thermodynamic parameters, such as the Gibbs free energy (Delta G(#)), enthalpy (Delta H-#), entropy (Delta S-#) and equilibrium constant of activation (K-#) were calculated. These parameters showed that the adsorption process of RBBR onto Z075 and Z300 was an endothermic process of a chemical nature under the studied conditions. (C) 2008 Elsevier B.V. All rights reserved.Öğe Cytotoxicity and apoptotic effects of nickel oxide nanoparticles in cultured HeLa cells(Via Medica, 2010) Ada, Kezban; Turk, Mustafa; Oguztuzun, Serpil; Kilic, Murat; Demirel, Mehmet; Tandogan, Nisa; Latif, OzturkThe aim of this study was to observe the cytotoxicity and apoptotic effects of nickel oxide nanoparticles on human cervix epithelioid carcinoma cell line (HeLa). Nickel oxide precursors were synthesized by an nickel sulphate-excess urea reaction in boiling aqueous solution. The synthesized NiO nanoparticles (<200 nm) were investigated by X-ray diffraction analysis and transmission electron microscopy techniques. For cytotoxicity experiments, HeLa cells were incubated in 50-500 mu g/mL NiO for 2, 6, 12 and 16 hours. The viable cells were counted with a haemacytometer using light microscopy. The cytotoxicity was observed low in 50-200 mu g/mL concentration for 16 h, but high in 400-500 mu g/mL concentration for 2-6 h. HeLa cells' cytoplasm membrane was lysed and detached from the well surface in 400 mu g/mL concentration NiO nanoparticles. Double staining and M30 immunostaining were performed to quantify the number of apoptotic cells in culture on the basis of apoptotic cell nuclei scores. The apoptotic effect was observed 20% for 16 h incubation.Öğe The effect of preparation procedure for precursor on the morphology, surface area and porosity of alumina powders(Asian Journal Of Chemistry, 2008) Ada, KezbanIn order to investigate the effect of preparation procedure for precursors on some physico-chemical properties of powders, three alumina precursors were prepared by different ways. The first precursor (P1) was precipitated by adding ammonia to the boiling aluminium sulphate solution buffered by NH3/NH4Cl (pH = 9.25). The second precursor (P2) was precipitated by the reaction between aluminium sulphate and excess urea in boiling aqueous solution (pH = 3.42). The third precursor (P3) was precipitated by the similar reaction in boiling aqueous solution buffered by C2H4(COOH)(2)/C2H4(COONH4)(2) (pH = 4.16). Three different alumina powders (P1, P2 and P3) were obtained by the calcination of the precursors at 1000 degrees C for 2 h. The powders were examined by scanning electron microscopy and nitrogen adsorption-desorption techniques. The BET specific surface areas (A) and specific micro-mesopore volumes (V) for the powders (P1, P2 and P3) were obtained as 116 m(2) g(-1) and 0.34 cm(3) g(-1), 66 m(2) g(-1) and 0.15 cm(3) g(-1) and 148 m(2) g(-1) and 0.59 cm(3) g(-1), respectively. The surface areas of the powders determined by other methods, are compared with the BET values.Öğe In vitro genotoxic effects of ZnO nanomaterials in human peripheral lymphocytes(Springer, 2014) Gumus, Duygu; Berber, Ahmet Ali; Ada, Kezban; Aksoy, HuseyinIn this study, possible genotoxic effects of zinc oxide (ZnO) nanoparticles were investigated in cultured human peripheral lymphocytes by using chromosome aberrations and micronucleus assays (MN). For this purpose, the cells were treated with ZnO (1, 2, 5, 10, 15 and 20 mu g/mL) for 24 and 48 h. In this research, four types of chromosome aberrations were observed as chromatid and chromosome breaks, fragment and dicentric chromosomes. ZnO induced significant increase of the ratio of chromosomal aberrations as well as percentage of abnormal cells at concentrations of 1, 5, 10 and 20 mu g/mL in 24 h treatments. In 48 h treatments, while ZnO nanomaterials induced significant increase of the percentage of abnormal cells only at a concentration of 10 mu g/mL, and of chromosome aberration per cell in comparison to the control at concentrations of 5 and 10 mu g/mL. On the other hand, this material significantly increased the micronuclei frequency (MN) at concentrations of 10 and 15 mu g/mL in comparison to the control. Cytokinesis-block proliferation index was not affected by ZnO treatments. It also decreased the mitotic index in all concentrations at 24 h but not at 48 h. The present results indicate that ZnO nanoparticles are clastogenic, mutagenic and cytotoxic to human lymphocytes in vitro at specific concentrations and time periods.Öğe Kinetic and equilibrium studies on the biosorption of Cl reactive orange 16 dye by immobilized Scenedesmus quadricauda(Asian Journal Of Chemistry, 2008) Tan, Sema; Ergene, Aysun; Ada, Kezban; Katircioglu, HikmetThe biosorption of commonly used reactive dye, reactive orange 16 (RO 16). from aqueous solutions by live (ILSq) and heat inactivated Scenedesmus quadricauda (IHISq) immobilized Scenedesmus quadricauda was studied in a batch system with respect to pH, temperature and biosorption time. The ILSq and IHISq exhibited the highest dye uptake capacity at 30 degrees C, the initial pH value of 2.0 and the initial dye concentration of 300 mg L(-1). At 300 mg L(-1) initial dye concentration in the batch system the adsorption capacity was determined as 88.4 mg g(-1) of dye biosorption for IHISq in 0.5 h. The adsorption capacity of ILSq was observed as 71.2 mg g(-1) in 0.5 h and 76.4 mg g(-1) and 82.8 mg g(-1) of dye biosorption within I and 3 h, respectively. The equilibrium concentration and the adsorption capacity at equilibrium were determined using four different sorption models i.e., Langmuir, Temkin, Flory-Huggins and Freundlich isotherm.Öğe A model for initial-stage sintering thermodynamics of an alumina powder(Elsevier Science Sa, 2008) Sarikaya, Yüksel; Ada, Kezban; Önal, MüşerrefA model was proposed to calculate several thermodynamic parameters for the initial-stage sintering of an alumina powder obtained after calcinations at 900 degrees C for 2 h of a precursor. The precursor was synthesized by an alumina sulphate-excess urea reaction in boiling aqueous solution. The cylindrical compacts of the powder with a diameter of 14 mm were prepared under 32 MPa by uniaxial pressing using oleic acid (12% by mass) as binder. The compacts were fired at various temperatures between 900 and 1400 degrees C for 2 h. The diameter (D) of the compacts before and after firing was measured by a micrometer. The D Value after firing was taken as a sintering equilibrium parameter. An arbitrary sintering equilibrium constant (K,) was calculated for each firing temperature by assuming K(a) = (D(i) -D)/(D-D(f)), where D(i) is the largest value before sintering and D(f) is the smallest value after firing at 1400 degrees C. Also, an arbitrary change in Gibbs energy (Delta G(a)degrees) was calculated for each temperature using the K(a) value. The graphs of In K(a) vs. 1/T and Delta G(a)degrees vs. T were plotted, and the real change in enthalpy (Delta H degrees) and the real change in entropy (AS') were calculated from the slopes of the obtained straight lines, respectively. Inversely, real Delta G degrees and K values were calculated using the real Delta H degrees and Delta S degrees values in the Delta G degrees = -RT In K = Delta H degrees-T Delta S degrees relation. The best fitting Delta H degrees and Delta S degrees values satisfying this relation were found to be 157,301 J mol(-1) and 107.6 J K(-1) mol(- 1), respectively. (c) 2008 Elsevier B.V. All rights reserved.Öğe Preparation and characterization of a ZnO powder with the hexagonal plate particles(Elsevier, 2008) Ada, Kezban; Goekgoez, Murat; Oenal, Mueserref; Sankaya, YuekselZinc oxide precursors were obtained by the reaction of excess urea with 0.05-0.30 M ZnSO4 in boiling aqueous solution. The precursors precipitated were dried at 100 degrees C for 2 h to yield powdery products and these products were calcined at 1000 degrees C for 2 h to yield zinc oxide powders. Differential thermal analysis (DTA) and thermal gravimetric analysis (TGA) curves of the air-dried precursor precipitates show that the suitable temperatures for dehydration of crystal water, of ligand water and of dehydroxylation are 76, 290, and 866 degrees C, respectively. From the scanning electron microscopy (SEM) photographs and particle size distribution (PSD) curves, the average sizes of the hexagonal plate particles in precursor and ZnO powders are found to be 55 and 35 mu m, respectively. X-ray diffraction (XRD) data were evaluated by Scherrer equation for the estimation of the average crystal size of the precursor (11 nm) and ZnO (45 nm). The specific surface area and specific micro-mesopore volume of the ZnO powders are so small as to fall into the experimental error limits. It was concluded that all the measured quantities are not affected considerably by the Zn2+ concentration. (c) 2007 Elsevier B.V. All rights reserved.Öğe Removal of Remazol Brilliant Blue R dye from aqueous solutions by adsorption onto immobilized Scenedesmus quadricauda: Equilibrium and kinetic modeling studies(Elsevier Science Bv, 2009) Ergene, Aysun; Ada, Kezban; Tan, Sema; Katircioglu, HikmetThe green algae Scenedesnnus quadricauda was immobilized in alginate gel beads. The immobilized active (IASq) and heat inactivated S. quadricauda (IHISq) were used for the removal of Remazol Brilliant Blue R (Cl 61200, Reactive Blue 19, RBBR) from aqueous solutions in the concentration range 25-200 mg L(-1). At 150 mg L(-1) initial dye concentration the IASq and IHISq exhibited the highest dye uptake capacity at 30 degrees C, at the initial pH value of 2.0. At the same initial dye concentration in the batch system the adsorption capacity was determined for IASq as 44.2: 44.9 and 45.7 mg g(-1) in 30. 60 and 300 min, respectively. After 300 min the adsorption capacity hardly changed during the adsorption time. The IHISq of adsorption capacity was observed as 47.6; 47.8 and 48.3 mg g(-1) in 30, 60 and 300 min. respectively. After 300 min the adsorption capacity was not changed for 24 h. The Langmuir, Freundlich, Temkin, Dubinin-Radushkevich and Flory-Huggins isotherm models were used to fit the equilibrium biosorption data. The Langmuir, Freundlich and Dubinin-Radushkevich equations have better coefficients than Temkin and Flory-Huggins equation describing the RBBR dye adsorption onto IASq and IHISq. The monomolecular biosorption capacity of the biomass was found to be 68 and 95.2 mg g(-1) for IASq and IHISq, respectively. From the Dubinin-Radushkevich model. the mean free energy was calculated as 6.42-7.15 kJ mol(-1) for IASq and IHISq, indicating that the biosorption of dye was taken place in physical adsorption reactions. The experimental data were also tested in terms of kinetic characteristics and it was determined that the biosorption process of dye was well explained with pseudo-second-order kinetics. (C) 2009 Elsevier B.V. All rights reserved.
