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    Evaluation of the thermodynamic parameters for the adsorption of some hydrocarbons on chemically treated-bentonites by inverse gas chromatography
    (Springerlink, 2005) Gürkan, Ramazan; Ceylan, Hasan; Şahan, Tekin; Savran, Ali; Kubilay, Şenol; Ceylan, Hasan
    Inverse gas chromatography has been used to evaluate the adsorption parameters ( Ha, Hst, Sa and Ga) of some probe molecules, each representing a class of organic (n-hexane, cyclohexane, benzene, n-octane, 1-octene and isooctane) on bentonite and chemically treated-bentonites. The adsorption parameters of the probes on the bentonite samples were determined in infinite dilution region. Adsorption of the organic species was investigated in the temperature range of 200–275?C, using a flame ionization detector, and nitrogen as a carrier gas. The net retention volumes (Vn) of the probes were determined by the help of the retention times (tR) observed on gas chromatograms for each probe. Injection was made at least three times for each probe, obtaining reproducible results of ±0.5%. It was found that benzene exhibits more negative H than for n-hexane and cyclohexane on all of the adsorbents. In addition, it was found that 1-octene exhibits more negative H than for n-octane and isooctane on the chemically treated-bentonites, whereas n-octane exhibits more negative H than for 1-octene and isooctane on the natural bentonite. Also, interactions of benzene with the natural- and chemically treated-bentonites were found to be stronger than those of n-hexane and cyclohexane with the same carbon number. Again, interactions of the 1-octene with the chemically treated-bentonites were found to be stronger those of n-octane and isooctane with the same carbon number. On the contrary, interactions of n-octane with the untreated-bentonite were found to be stronger than those of 1-octene and isooctane.
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    Optimization of removal conditions of copper ions from aqueous solutions by Trametes versicolor
    (Elsevier, 2010) Şahan, Tekin; Ceylan, Hasan; Şahiner, Nurettin; Aktaş, Nahit; Ceylan, Hasan
    A multi-step response surface methodology was successfully applied to optimize the biosorption conditions for the maximum removal of Cu(II) ions from aqueous solutions using Trametes versicolor fungi as a biosorbent. In the first step, the most effective medium factors, which are pH, temperature and initial Cu(II) concentration, on biosorption of Cu(II), were determined through Plackett–Burman Design. Then steepest accent followed by central composite design steps were utilized to evaluate the optimum biosorption conditions for the maximum Cu(II) ions removal. Based on the statistic analysis; the optimum conditions were obtained 5.51, 20.13 C and 60.98 mg/L as medium pH, medium temperature and initial Cu(II) concentration, respectively. Finally the analysis of variance (ANOVA) of central composite design showed the proposed quadratic model fitted experimental data very well.
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    Removal of some heavy metal cations from aqueous solution by adsorption onto natural kaolin
    (SageJournals, 2005) Ceylan, Hasan; Şahan, Tekin; Gürkan, Ramazan; Kubilay, Şenol; Ceylan, Hasan
    The adsorption removal of some heavy metal cations such as Cu(II), Zn(II) and Co(II) from aqueous solution onto kaolin has been studied using the batch method with initial metal ion concentrations within the range 15–70 mg/l. The percentage adsorption and equilibrium concentrations were determined by means of atomic absorption flame photometry as a function of adsorbate concentration, pH and temperature. Ion-exchange studies showed that over the complete concentration range studied the adsorption ratios for metal cations adsorbed onto kaolin correlated with the linear forms of the Langmuir, Freundlich and Dubinin–Kaganer–Radushkevich (DKR) adsorption isotherms. The cationexchange capacity of kaolin towards each metal ion studied was evaluated. It was found that the adsorption phenomena depended on the charge density and diameter of the hydrated ion. The equilibrium studies demonstrated that the selectivity of the ions followed the sequence Zn(II) > Cu(II) > Co(II) at pH 7.0. Calculation of thermodynamic parameters such as the standard enthalpy (?H0), Gibbs free energy (?G0) and entropy (?S0) showed that the adsorption of the heavy metal ions studied onto kaolin was an endothermic process which was favoured at higher temperatures. These results show that natural kaolin has a considerable potential for the removal of heavy metal cationic species from aqueous solution and wastewater.