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    A comperative study for adsorption of methylene blue from aqueous solutions by two kinds of amberlite resin materials
    (Desalination Publ, 2012) Kerkez, Ozge; Bayazit, Sahika Sena; Uslu, Hasan
    An organic dye, methylene blue (MB), was separated from a model aqueous solution by using adsorption method with low cost resin adsorbents. The adsorption of MB was studied with Amberlite XAD-16 and Amberlite XAD-7 HP. The aim of the study is to achieve a high removal value of the dye and comparing these two adsorbents for MB adsorption. Adsorption of MB was investigated in terms of equilibrium and kinetics conditions. Adsorption isotherms were determined and correlated with equations such as Freundlich, Langmuir and Temkin isotherm models. Langmuir isotherm has good agreement with R-2 value over 0.99. Pseudo second order model was fitted for this adsorption system. Here we showed that 99% removal of MB can be achieved with Amberlite XAD-16. SEM studies revealed the morphological observations of the unloaded adsorbent and the changes in the adsorbed polymeric resin. FTIR spectrums of adsorbents before and after the adsorption supported the SEM results.
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    Efficient removal of methylene blue by photocatalytic degradation with TiO2 nanorod array thin films
    (Springer, 2013) Kerkez, Ozge; Boz, Ismail
    TiO2 nanorod array thin films were synthesized on fluorine doped tin oxide (FTO) glass substrate by the hydrothermal method. The prepared TiO2 nanorod arrays were characterized by X-ray diffraction, scanning electron microscopy and UV-Vis diffuse reflectance spectroscopy. The effect of different synthesis conditions was investigated on the growth and photocatalytic activity of the samples. X-ray diffraction results show that the main phase of TiO2 is rutile and nanorod growth significantly depends on the synthesis conditions. TiO2 nanorod array thin films were used for the photocatalytic degradation of methylene blue in aqueous solution under UV irradiation (254 and 365 nm). The hydrothermal synthesis conditions of TiO2/FTO sample were determined for maximum photodegradation efficiency. Total degradation of 94 % was achieved under 254 nm and 69 % degradation was achieved under 365 nm with TiO2/FTO sample prepared with initial HCl:H2O = 1:1 ratio, 1.0 ml TiCl4 at 180 A degrees C for 2 h hydrothermal growth. The apparent reaction rate constant was calculated to be 0.0108 min(-1) under 254 nm and 0.0044 min(-1) under 365 nm.
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    Hexavalent chromium adsorption on superparamagnetic multi-wall carbon nanotubes and activated carbon composites
    (Inst Chemical Engineers, 2014) Bayazit, Sahika Sena; Kerkez, Ozge
    Hexavalent chromium (Cr(VI)) adsorption from aqueous solutions on magnetically modified multi-wall carbon nanotubes (M-MWCNT) and activated carbon (M-AC) was investigated. M-MWCNT and M-AC were prepared by co-precipitation method with Fe2+:Fe3+ salts as precursors. The magnetic adsorbents were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The effects of amount of adsorbents, contact time, initial pH, temperature and the initial concentration of Cr(VI) solution were determined. The adsorption equilibrium, kinetics, thermodynamics and desorption of Cr(VI) were investigated. Equilibrium data fitted well with the Langmuir isotherm forboth of the adsorbents. The theoretical adsorption capacities are 14.28 mg/g of M-MWCNT and 2.84 mg/g of M-AC. Cr(VI) adsorption kinetics was modeled with pseudo-second order model, intraparticle diffusion model and Bangham model. Thermodynamic parameters were calculated and AG, Ali and AS indicate that the adsorption of Cr(VI) onto M-MWCNT and M-AC was exothermic and spontaneous in nature. Results revealed that M-MWCNT is an easily separated effective adsorbent for Cr(VI) adsorption from aqueous solution. (C) 2014 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.
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    Magnetite decorated multi-walled carbon nanotubes for removal of toxic dyes from aqueous solutions
    (Springer, 2014) Kerkez, Ozge; Bayazit, Sahika Sena
    The removal of malachite green (MG) and rhodamine B (RB) from aqueous solutions was studied by batch adsorption technique using Fe3O4/MWCNT. Fe3O4/MWCNT adsorbent was synthesized by co-precipitation method and characterized by XRD, SEM, and TGA. 94 % MG removal and 98 % RB removal were achieved in 80 min using 10 mg adsorbent, at pH 6 and 298 K. The effects of adsorbent amount, pH, initial dye concentration, contact time, and temperature were investigated. Equilibrium data were well fitted by Langmuir adsorption model and pseudo-second-order kinetic model. MG adsorption on Fe3O4/MWCNT is exothermic and RB adsorption is endothermic in nature.
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    Photo(electro)catalytic Activity of Cu2+-Modified TiO2 Nanorod Array Thin Films under Visible Light Irradiation
    (Pergamon-Elsevier Science Ltd, 2014) Kerkez, Ozge; Boz, Ismail
    In the present study, a two-step method was applied to synthesise Cu2+-modified TiO2 nanorod array thin films for photocatalytic processes. TiO2 nanorod array thin films were synthesised by a hydrothermal method and then modified with an ultrasonic-assisted sequential cation adsorption method. The samples were characterised by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra (DRS), scanning electron microscopy (SEM), photoluminescence (PL) spectroscopy and inductively coupled plasma mass spectroscopy (ICP-MS) analysis. The photoelectrochemical properties of the samples were evaluated by linear sweep voltammetry and Mott-Schottky analysis; photocatalytic activities were tested by methylene blue degradation under visible light. The photocurrent density of the TiO2/FTO sample modified with 50 mM Cu2+ solution was 26 times higher than that of the unmodified TiO2/FTO sample. Additionally, methylene blue degradation efficiency under visible light was increased 40% with respect to the efficiency of the unmodified sample. The mechanism of the photocatalytic activity enhancement of Cu2+-modified TiO2 nanorod films was discussed. (C) 2013 Elsevier Ltd. All rights reserved.
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    Photodegradation of Methylene Blue with Ag2O/TiO2 under Visible Light: Operational Parameters
    (Taylor & Francis Inc, 2015) Kerkez, Ozge; Boz, Ismail
    Ag2O modified TiO2 nanoparticles were synthesized by precipitation and wet impregnation method. They were characterized by X-ray diffraction technique, UV-vis diffuse reflectance spectrophotometry and Fourier transform infrared spectroscopy. Inductively coupled plasma mass spectrometry was performed to quantify Ag amount in the photocatalysts. The photocatalysts occurred in the concentration range of 0.05%-2% in the Ag/Ti molar ratio. The photocatalytic activity was investigated for the degradation of methylene blue as a model organic dye. Optimum reaction conditions were determined to provide maximum dye degradation efficiencies under visible light. Under visible light illumination, C2-Ag2O/TiO2 (Ag/Ti=0.1/100) showed the highest activity. Reaction rate constants were calculated and compared for various reaction conditions.
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    Removal of ciprofloxacin from aqueous solution using humic acid- and levulinic acid- coated Fe3O4 nanoparticles
    (Inst Chemical Engineers, 2017) Danalioglu, Selen Tugba; Bayazit, Sahika Sena; Kerkez, Ozge; Alhogbi, Basma G.; Salam, Mohamed Abdel
    Humic acid (HA)- and levulinic acid (LA)-coated magnetic Fe3O4 nanoparticles were prepared and subsequently characterized using scanning electron microscopy, X-ray diffraction spectroscopy, Fourier transformer infrared spectroscopy, thermogravimetric analysis, particle size distribution analysis, and zeta-potential analysis. These magnetic nanoparticles were used for ciprofloxacin adsorption from aqueous solutions. Non-linear Langmuir and Freundlich adsorption isotherm models were used to explain the adsorption equilibria. The Langmuir adsorption capacities (q(m)) were 101.93 mg/g for HA-coated Fe3O4 and 53.76 mg/g for LA-coated Fe3O4. The appropriate contact times were 40 min for HA-coated Fe3O4 and 60 min for LA-coated Fe3O4. The adsorption rates and mechanisms were determined using pseudo-first-order and pseudo-second-order kinetic models. After the adsorption studies, the loaded nanoparticles were used for desorption studies, and their desorption kinetics were investigated. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.