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    Adsorption of heavy metal ions from aqueous solutions by bio-char, a by-product of pyrolysis
    (ELSEVIER SCIENCE BV, 2013) Kilic, Murat; Kirbiyik, Cisem; Cepeliogullar, Ozge; Putun, Ayse E.
    Bio-char, a by-product of almond shell pyrolysis, was used as an alternative adsorbent precursor for the removal of heavy metal ions from aqueous solutions. The adsorption potential of almond shell bio-char for Ni(II) and Co(II) removal was investigated. Adsorption experiments were carried out by varying pH, adsorbent dosage, initial metal ion concentrations, contact time and temperature to determine the optimum conditions. To describe the equilibrium isotherms the experimental data were analyzed by the Langmuir, Freundlich, Dubinin-Radushkevich (D-R) and Temkin isotherm models. Pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models were used to find out the kinetic parameters and mechanism of adsorption process. The thermodynamic parameters such as Delta G degrees, Delta H degrees and Delta S degrees were calculated for predicting the nature of adsorption. The results showed that bio-char derived from pyrolysis of biomass can be used as a low-cost and effective adsorbent for removal of heavy metal ions from aqueous solutions. (C) 2013 Elsevier B.V. All rights reserved.
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    Comparative studies on adsorptive removal of heavy metal ions by biosorbent, bio-char and activated carbon obtained from low cost agro-residue
    (IWA PUBLISHING, 2016) Kirbiyik, Cisem; Putun, Ayse Eren; Putun, Ersan
    In this study, Fe(III) and Cr(III) metal ion adsorption processes were carried out with three adsorbents in batch experiments and their adsorption performance was compared. These adsorbents were sesame stalk without pretreatment, bio-char derived from thermal decomposition of biomass, and activated carbon which was obtained from chemical activation of biomass. Scanning electron microscopy and Fourier transform-infrared techniques were used for characterization of adsorbents. The optimum conditions for the adsorption process were obtained by observing the influences of solution pH, adsorbent dosage, initial solution concentration, contact time and temperature. The optimum adsorption efficiencies were determined at pH 2.8 and pH 4.0 for Fe(III) and Cr(III) metal ion solutions, respectively. The experimental data were modelled by different isotherm models and the equilibriums were well described by the Langmuir adsorption isotherm model. The pseudo-first-order, pseudo-second-order kinetic, intra-particle diffusion and Elovich models were applied to analyze the kinetic data and to evaluate rate constants. The pseudo-second-order kinetic model gave a better fit than the others. The thermodynamic parameters, such as Gibbs free energy change Delta G degrees, standard enthalpy change Delta H degrees and standard entropy change Delta S degrees were evaluated. The thermodynamic study showed the adsorption was a spontaneous endothermic process.
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    Enhancing the c-TiO2 based perovskite solar cell performance via modification by a serial of boronic acid derivative self-assembled monolayers
    (ELSEVIER, 2017) Kirbiyik, Cisem; Kara, Koray; Kara, Duygu Akin; Yigit, Mesude Zeliha; Istanbullu, Bilal; Can, Mustafa; Sariciftci, Niyazi Serdar
    Morphological control of MAPbI(3) crystal growth is one of the most important factor to fabricate high efficient perovskite solar cells. Herein, different boronic acid derivative self-assemble monolayers were used for modification of c-TiO2 surface and controlling of interface properties between c-TiO2 and MAPbI(3) layers. Pre-mixed MAPbI(3) solution in GBL was deposited by spin-coating technique onto non-modified and modified c-TiO2 surfaces by selected SAMs. The 1-OMe modified c-TiO2 based solar cell shows an increase in J(sc), resulting an increase to 9.4% PCE to compare with 5.9% PCE of non-modified c-TiO2 based solar cell. With this work, we demonstrated the possibility of morphological control of perovskite layer by using simple modification method of sublayer to increase the photovoltaic characteristics of solar cells. (C) 2017 Elsevier B.V. All rights reserved.
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    Equilibrium, kinetic, and thermodynamic studies of the adsorption of Fe(III) metal ions and 2,4-dichlorophenoxyacetic acid onto biomass-based activated carbon by ZnCl2 activation
    (ELSEVIER, 2017) Kirbiyik, Cisem; Putun, Ayse Eren; Putun, Ersan
    This study investigated the preparation of activated carbon from low-cost biomass as precursor and the using of obtained activated carbon for the removal of Fe(III) and 2,4-D pollutants from model solution. The different parameters affecting the adsorption were examined. Equilibrium data were fitted into Langmuir, Freundlich, D-R and Temkin isotherm models for four different examined temperatures (from 20 to 50 degrees C). Adsorption of 2,4-D was well described by Freundlich isotherm as a physical adsorption, whereas Langmuir model well described the adsorption of Fe(III) at four different temperatures from 20 to 50 degrees C. Pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich models were used to analyse kinetic data. The adsorption kinetics for both pollutants were found to match pseudo-second-order kinetic model with high correlation (between 0.975-0.999 for Fe(III), between 0.995-0.999 for 2,4-D) than the other models. In addition, the thermodynamic parameters were evaluated and discussed for the thermodynamically modeling of the adsorption processes.