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    A comparative study for removal of different dyes over M/TiO2 (M = Cu, Ni, Co, Fe, Mn and Cr) photocatalysts under visible light irradiation
    (Elsevier Science Sa, 2015) Kerkez-Kuyumcu, Ozge; Kibar, Efgan; Dayioglu, Kubra; Gedik, Fadime; Akin, Ayse NIlgun; Ozkara-Aydinoglu, Seyma
    The purpose of this work is to design and develop a series of stable and effective TiO2 photocatalysts prepared by a modified precipitation method. In order to improve the photo response of the TiO2 to the visible region, the effect of addition of six successive transition metal elements of fourth period, namely chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), and copper (Cu) was studied. Two different types of dyes, methyl orange (MO, azo dye) and methylene blue (MB, thiazine dye group), were used to investigate the influence of structure of dyes on the photocatalytic degradation rates. The results showed that loading titania with 0.3 wt.% of different transition metal elements was found to have significant influences on the crystallographic structure, physical properties and optical absorption properties of titania based catalysts, as well as catalytic activity during dye degradation reactions. The optical reflection edge was obviously shifted to the visible light range with the transition metal additives. The band gap energies of the doped TiO2 samples were considerably narrower than that of plain TiO2. The different activity levels of the catalysts for both dyes clearly show that the photocatalytic activity of samples strongly depended on the metal dopant used. Among all the catalysts, Cu/TiO2 sample exhibited the highest photocatalytic activity under visible light for both of the dyes owing to the low band gap energy and delayed electron-hole recombination. (C) 2015 Elsevier B.V. All rights reserved.
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    A comparative study on the kinetics of carbon dioxide reforming of methane over Pt-Ni/Al2O3 catalyst: Effect of Pt/Ni Ratio
    (Elsevier Science Sa, 2013) Ozkara-Aydinoglu, Seyma; Aksoylu, A. Erhan
    Kinetics and surface reaction mechanism of CO2 reforming of methane (CDRM) was studied over 0.2%Pt-15%Ni/Al2O3 and 0.3%Pt-10%Ni/Al2O3 catalysts in order to determine the effect of Ni/Pt loading ratio on kinetic behavior. The simple power-law type rate expressions obtained for 0.3%Pt-10%Ni/Al2O3 and 0.2%Pt-15%Ni/Al2O3 have reaction orders of 1 and 1.09 for CH4 and 0.87 and 1.40 for CO2, respectively, confirming methane consumption rate for 0.2%Pt-15%Ni/Al2O3 sample is more sensitive to the increase in partial pressure of CO. The comparative analysis of meaningful surface reaction models for the catalysts and the optimized model parameters obtained revealed that the surface reaction mechanisms are completely different CO inhibition effect is stronger and CO2 utilization is suppressed on the catalyst with high Ni:Pt loading ratio. On the other hand, with a decrease in Ni:Pt loading ratio, CH4 adsorption becomes weaker, ability of utilizing CO2 as the oxygen source gets stronger and CO inhibition effect is practically eliminated. (C) 2012 Elsevier B.V. All rights reserved.
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    Enhanced & effective phosphate recovery from water by indium fumarate & zirconium fumarate metal-organic frameworks: Synthesis, characterization, adsorption, kinetic and isotherm studies
    (Elsevier, 2022) Ozcelik, Gulsum; Cavusoglu, Ferda Civan; Ozkara-Aydinoglu, Seyma; Bayazit, Sahika Sena
    Eutrophication has been an important environmental issue for the last decade. Agricultural and industrial actions cause high concentrations of phosphate discharging to surface and ground waters, and high levels of phosphate concentration causes eutrophication. The decreasing of the phosphate concentration is an essential matter and adsorption is one of the most effective solutions for this purpose. In this study, indium fumarate (In-fum) and zirconium fumarate (Zr-fum) were prepared. Surface characterizations of these adsorbents were applied by XRD, FTIR, SEM, TGA, DSC, and BET surface analysis. The surface areas of In-fum and Zr-fum were determined as 181.19 m(2)/g and 527.96 m(2)/g, respectively. Water absorption abilities of adsorbents were tested by Karl-Fischer method. The water contents inside the pores of water-treated Zr-fum and In-fum are 0.0560% (w/w) and 0.0694% (w/w), respectively. Phosphate adsorption performances of In-fum and Zr-fum particles were studied by parametric research, investigating the effects of adsorbent quantity, contact time, solution pH, initial solution concentration, adsorption temperature, and co-existing ions. The phosphate adsorption uptake (q(e)) of Zr-fum is 33.52 mg/g and qe value of In-fum is 31.29 mg/g when adsorbent quantity is 1 mg. The kinetic studies reveal that both adsorbents follow pseudo second-order kinetic model according to the R-2 values. These values are 0.93 for In-fum and 0.98 for Zr-fum. The rate constants are 0.15 g/mg min (In-fum) and 0.14 x 10(-2) g/mg min (Zr-fum). Theoretical maximum phosphate adsorption uptake (q(m)) of In-fum is 93.40 mg/g at 318 K. The q(m) value of Zr-fum is 67.44 mg/g at 308 K. Phosphate adsorption over In-fum is strongly dependent on temperature change whereas the effect of temperature on adsorption performance of Zr-fum is insignificant. The pH of the phosphate solution should be below 7 to obtain an appropriate surface and phosphate ion charge combination. The presence of co-existing chloride ions does not dramatically affect phosphate adsorption capacity.
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    Fe3O4 supported UiO-66 (Zr) metal-organic framework for removal of drug contaminants from water: fuzzy logic modeling approach
    (Springer Heidelberg, 2023) Cavusoglu, Civan Ferda; Ozcelik, Guelsuem; Ozbek, Cengiz; Ozkara-Aydinoglu, Seyma; Bayazit, Sahika Sena
    The increase in production and consumption of pharmaceuticals and personal care products causes environmental problems. In this study, naproxen and clofibric acid adsorption were studied using Fe3O4-supported UiO-66 (Zr) metal-organic framework (Mag-UiO-66). The adsorption processes were carried out in batch mode at pH value 3.0. The optimum adsorbent quantities, equilibrium periods, pseudo-first-order (PFO), pseudo-second-order (PSO), and intra-particles diffusion kinetic models were calculated. Non-linear Langmuir, Freundlich, Dubinin-Radushkevich (D-R), and Sips isotherm equations were applied to experimental data. Thermodynamic analyses of naproxen and clofibric acid adsorption were also carried out in this study. The Langmuir isotherm q(m) values were found as 14.15 mg/g for naproxen at 308 K and 41.87 mg/g for clofibric acid at 298 K. Both of the adsorption processes were exothermic. MISO (multi-input single-output) fuzzy logic models for removal of both naproxen and clofibric acid adsorptions were designed based on the experimental data to estimate the removal uptake values. It is noteworthy that the results obtained through designed fuzzy logic models matched well with the experimental data and the findings of this study emphasize the validity of designed fuzzy logic models.
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    La, Mn and Zn promoted microporous iron catalysts with high productivity and stability for Fischer-Tropsch synthesis
    (Springer, 2016) Gul, Omer F.; Atac, Ozlem; Boz, Ismail; Ozkara-Aydinoglu, Seyma
    Fischer-Tropsch synthesis is studied over precipitated Fe catalysts promoted with Mn, Zn and La metals. The results showed that there was a large increase in surface area and pore volume, and a sharp decrease in average pore size upon the addition of promoters. Catalyst productivity and rate of syngas converted as well as hydrocarbon yield increased with addition of promoters to Fe structure during precipitation step. Addition of metal promoters led catalyst samples of microporous structures with relatively high surface areas. This effect probably yielded catalysts with enhanced long-term activity and stability. Samples containing 10 % Zn and 5 % Mn exhibited the highest catalytic activity and stability. Increasing the loading of Zn from 5 to 10 wt% led to a noteworthy increase on yield and productivity as well as rate of syngas converted. The highest productivity was obtained for the sample containing 10 % Zn, highest yield was attained over the sample containing 5 % Mn. The results indicate that the selectivity to C-12-C-18 range was more pronounced for the catalyst promoted with Mn metal whereas alpha-olefins and higher molecular weight products were increased with the addition of 5 % Zn over Fe based catalysts. The decrease in temperature from 523 to 493 K resulted in an increase in heavy hydrocarbons and a significant decrease in gaseous and light hydrocarbons for Fe4Si5Mn catalyst.
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    ?-olefin selectivity of Fe-Cu-K catalysts in Fischer-Tropsch synthesis: Effects of catalyst composition and process conditions
    (Elsevier Science Sa, 2012) Ozkara-Aydinoglu, Seyma; Atac, Ozlem; Gul, Omer F.; Kinayyigit, Solen; Sal, Sinan; Baranak, Murat; Boz, Ismail
    Fischer-Tropsch (FT) synthesis has been studied over a series of precipitated Fe catalysts promoted to investigate the effect of K and Cu promoters on the carbon number distribution of FT product. The main intention is to maximize the alpha-olefin selectivity by controlling the secondary reactions of alpha-olefin as a function of potassium and copper loadings. The results showed that impregnation of different loadings of Cu and K promoters to precipitated iron-based catalyst was found to have significant influences on the crystallographic structure, morphological and physical properties of iron-based catalysts, as well as catalytic activity, stability and selectivity performances during FT synthesis. 100Fe7Cu3K sample exhibited the highest catalytic activity and stability in TOS tests. The catalyst is capable of working under a variety of temperatures and space velocities at a same activity level with no significant activity loss. Proper control of Cu and K contents is essential to obtain maximum C-5+ yield since the changes in the relative loadings of both Cu and K promoters affect hydrocarbon product distribution. 100Fe7Cu3K sample has high secondary alpha-olefin hydrogenation activity as olefin/paraffin ratio decreases with increasing carbon number while C-19+ selectivity is relatively low compared to other samples. The effects of space velocity and temperature on alpha-olefin selectivity are strongly dependent on the amounts of Cu and K promoters and chain length. The maximum alpha-olefin/n-paraffin ratio has been obtained over 100Fe3Cu1K sample at 543 K with a space velocity of 3 NL/h/g-cat. (C) 2011 Elsevier B.V. All rights reserved.
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    Photocatalytic degradation of organic dyes under visible light on sol-gel derived M/ZnO (M=Cr, Mn, Sn, Fe, Ni, Cu, Co, Ba) catalysts
    (Springer, 2022) Demir, Beyza; Tuter, Melek; Ozkara-Aydinoglu, Seyma
    A series of ZnO photocatalysts were developed by sol-gel method for photocatalytic degradation of dyes in textile wastewater under visible light irradiation. Eight different metal elements (barium, cobalt, copper, chromium, iron, manganese, nickel, and tin) were incorporated into ZnO structure to improve the photocatalytic activity of the samples in the visible region. The synthesized particles were characterized by X-ray diffraction, inductively coupled plasma, N-2 adsorption techniques and UV-vis diffuse reflectance spectroscopy. Two different types of dyes, rhodamine B and methylene blue, were used to study the effect of dye structure on degradation rates. The results showed that addition of different metal elements on ZnO structure had remarkable effects on textural and optical properties, crystal structures, and photodegradation rates. The surface area of ZnO increased with the metal ion additives. The band gap energy of the ZnO was reduced by addition of Sn dopant. The diverse photocatalytic trends of metal-doped ZnO samples for both dyes undoubtedly showed the significant and drastic effect of metal dopant on the photocatalytic activity. For photodegradation of both rhodamine B and methylene blue under visible light, Sn doped ZnO showed the highest photocatalytic owing to the decreased band gap of ZnO and suppressed recombination of electron-hole pairs. The pH of the reaction medium had also significant effect on degradation rate.
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    A thermodynamic equilibrium analysis of hydrogen and synthesis gas production from steam reforming of acetic acid and acetone blends as bio-oil model compounds
    (Pergamon-Elsevier Science Ltd, 2022) Kizilpelit, Busra Gonca; Karaosmanoglu, Filiz; Ozkara-Aydinoglu, Seyma
    Thermodynamic analysis of steam reforming of blends of two model oxygenates, acetic acid and acetone, representing carboxylic acids and ketones in bio-oil is performed to investigate the effects of their potential interactions on hydrogen yield, synthesis gas composition and progress of reaction network. The results show that both acetic acid and acetone reach complete conversion at all operating conditions. Higher S/C molar ratio results in higher H2 and CO2 yields for both acetic acid and acetone. With the increase in pressure, H2 and CO yields are diminished whereas CH4 and CO2 yields are enhanced. H2 and CO2 yields increase with the decrease in acetone concentration in the feed blend. CO and CH4 production are affected adversely for acetic acid rich blends. The maximum H2 yield values are 75.54%, 78.34%, 80.09%, 81.78% and 84.17% at 700 degrees C for acetic acid/acetone blends of 0.0/1.0, 0.3/0.7, 0.5/0.5, 0.7/0.3 and 1.0/0.0, respectively.(c) 2022 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.