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Öğe Adsorption of crystal violet from aqueous solution on activated carbon derived from Gölbaşi lignite(2012) Depci T.; Kul A.R.; Onal Y.; Disli E.; Alkan S.; Turkmenoglu Z.F.Activated carbon (AC) was obtained from lignite of the local resource, Gölbaşi{dotless};- Adi{dotless};yaman (Turkey) by chemical activation. The Gölbaşi{dotless}; lignite was chosen as the precursor for its availability and low cost. The BET surface area of the activated carbon was found 921 m2/g. The AC was used as an adsorbent for Crystal Violet (CV) in aqueous solution. The adsorption properties of CV onto the activated carbon are discussed in terms of the adsorption isotherms (Langmuir and Freundlich) and the kinetic models (pseudo-first-order, pseudo-second-order and intraparticle diffusion model). It was shown that the experimental results best fitted by the Langmuir model, and the second-order kinetic equation. The thermodynamic parameters show that the adsorption process is endothermic. The experimental results point out that the obtained activated carbon is a viable candidate for sorbent removing CV from aqueous solutions.Öğe Characteristic properties of adsorbed catalase onto activated carbon based adiyaman lignite(2011) Depci T.; Alkan S.; Kul A.R.; Önal Y.; Alacabey I.; Dişli E.Catalase is one of the most common and important enzymes in biological systems. However, its purification process has some difficulties and it can be easily decomposed in aqueous or nonaqueous solutions. Therefore, a catalase should be adsorbed on solid materials to reduce its inactivation and to increase its economic value. Activated carbon which was obtained from Turkish low-rank coal (Gölbaşi-Adiyaman) by chemical activation was used as a solid carrier to adsorb catalase for the first time in this research. The pore structure of the activated carbon was determined by A Tri Star 3000 (Micromeritics, USA) surface analyzer and scanning electron microscope. In order to determine adsorption properties of catalase, ionic strength effect, temperature-activity, pH-activity, storage stability and operational stability of the activated carbon were investigated. The kinetic and thermodynamic mechanisms of adsorbed enzyme were also studied. The experimental results pointed out that the obtained activated carbon is a viable candidate for an alternative solid carrier for catalase and it may be a promising material for various biotechnological applications. © by PSP.Öğe Equilibrium, kinetic and thermodynamic studies of nickel adsorption onto natural and modified kaolinites(2011) Kul A.R.; Depci T.; Alacabey I.; Alkan S.; Onal Y.Availability of clay and its modified forms makes them a viable candidate for an alternative adsorbent.this study, kaolinite and modified kaolinites were tested to determine their suitability for removal of Ni (II) ions from aqueous medium. Parameters, such as kaolinite type, concentration of Ni ions, time and temperature of interaction, were investigated to evaluate the adsorption capacity, kinetics, equilibrium and thermodynamic properties of Ni (II) adsorption. The adsorption isotherms followed Freundlich, Dubinin-Redushkevich (D-R) and Halsey isotherms but DR isotherm was chosen due to its applicability to all adsorption isotherms. The kinetics of adsorption mechanism of Ni (II) was tested using pseudo-first-order, pseudosecond-order and intraparticle diffusion models. The results showed that adsorption mechanism could be perfectly explained with pseudo-second order equation. The intraparticle diffusion of Ni (II) ions within the natural and modified kaolinite was more likely to be governed by the diffusion step. Adsorption mechanism for activated kaolinite was intra-particle diffusion model. Ni (II) adsorptions on activated kaolinites were exothermic and spontaneous in nature. The results of this study indicated that activated kaolinite can be employed for removal of Ni (II) from industrial wastewater. © by PSP.Öğe Exploring the Impact of Lanthanum on Sodium Manganese Oxide Cathodes: Insight into Electrochemical Performance(John Wiley and Sons Inc, 2024) Whba R.; Altundag S.; Aydin M.G.; Kalyoncuoglu B.; Ozgul M.; Depci T.; Altin S.This investigation focuses on nominally La-doped Na0.67MnO2, exploring its structural, electrochemical, and battery characteristics for Na-ion batteries. X-ray diffraction analysis reveals formation of composite materials containing three distinct phases: P2-Na0.67MnO2, NaMn8O16, and LaMnO3. The bond structures of the powders undergo scrutiny through Fourier-transform infrared and Raman analyses, revealing dependencies on the NaO, MnO, and LaO structures. X-ray photoelectron spectroscopy and energy-dispersive X-ray dot mapping analyses show that the La ions are unevenly dispersed within the samples, exhibiting a valence state of 3+. Half-cell tests unveil similarities in redox peaks between the cyclic voltammetry analysis of La-doped samples and P2-type Na0.67MnO2, with a reduction in peak intensities as La content increases. Electrochemical impedance spectroscopy model analysis indicates direct influences of La content on the half-cell's resistive elements values. The synergistic effect of composite material with multiple phases yields promising battery performances for both half and full cells. The highest initial capacity value of 208.7 mAh g?1, with a 57% capacity fade, among others, is observed, and it diminishes with increasing La content. Full cells are constructed using an electrochemically presodiated hard carbon anode, yielding a promising capacity value of 184.5 mAh g?1 for sodium-ion battery studies. © 2024 Wiley-VCH GmbH.Öğe The nature of graphene surfaces as determined from the wettability studies of basal and edge planes(Electrochemical Society Inc., 2015) Bhattacharyya D.; Depci T.; Assemi S.; Prisbrey K.; Miller J.D.Effective exploitation of the electronic properties of graphene in aqueous medium has been limited due to lack of information about its wettability characteristics. In this paper, fundamental wettability studies of the face and edge planes of graphene were accomplished through contact angle measurements of the as-received and oxidized surfaces. Further, Raman spectroscopic studies were performed to analyze the effect of oxidation on the graphene surfaces based on the D and G bands. Atomic force microscopy (AFM) was used for surface force measurements to determine the iso-electric point (IEP) of the face and edge surface. The interaction of hydrophobic fullerene and hydrophilic fullerol nanoparticles on the graphene face and edge surfaces was studied through AFM imaging. The zeta potential measurements of the above mentioned carbon nanoparticles were also carried out to confirm that the interaction was due to hydrophobic or hydrophilic forces and not due to electrostatic interactions. In addition molecular dynamics and ab-initio simulations were also carried out to verify the interactions of the carbon nanoparticles with the graphite surfaces. © The Electrochemical Society.
