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    Kinetics and Thermodynamics of Cr(VI), Cu(II), and Ni(II) Adsorption on Activated Carbon Prepared from Rice Hulls
    (Taylor & Francis Inc, 2013) Bayrak, Yuksel; Topallar, Harika; Karagoz, Buse; Kilic, Ismail
    First, activated carbon was prepared by various ammonium compounds such as NH4NO3, NH4Cl, NH4Br, NH4I, NH4HCO3, and (NH4)(2)HPO4. The pore properties such as surface areas, pore volumes and pore sizes of them were compared under same activation conditions (600 degrees C, 5g of rice hull, 20g of ammonium compound, within a half-hour activation time). The highest surface area by Brunauer-Emmett-Teller (BET) method was obtained as 456.7667m(2)g(-1) by ammonium nitrate compared to other ammonium compounds, and then the kinetics and thermodynamics of Cr(VI), Cu(II), and Ni(II) ions removal from aqueous solutions on this activated carbon were studied. The adsorption data was found to follow second order kinetic model to explan the kinetics of Cr(VI), Cu(II), and Ni(II) ions adsorption, and rate constants were evaluated with the help of this kinetic model. Activation energy and other activation thermodynamic parameters (S, H, and G) were determined by means of the rate constants at different temperatures. Equilibrium data were fitted to the Langmuir and Freundlich adsorption isotherms. Freundlich isotherm best fits the experimental results. Thermodynamic parameters such as K-C, G, H, and S were also calculated. The positive value of S and negative values of G showed the spontaneous of this adsorption system, while the positive value of H pointed out this is an endothermic process.
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    Preparation of Rice Hull-Based Activated Carbon with Ammonium Nitrate
    (Asian Journal Of Chemistry, 2013) Kilic, Ismail; Bayrak, Yuksel; Topallar, Harika; Karagoz, Buse
    The present study deals with the preparation of rice hull-based activated carbon with ammonium nitrate. The obtained carbon was activated at temperatures between 400 and 900 degrees C. The rice hull-activated carbon presented a BET surface area of 456.77 m(2) g(-1) and a pore volume of 0.2406 cm(3) g(-1) at 600 degrees C. The adsorption and desorption average pore widths by BET method were found as 2.727 and 2.725 nm, respectively, whereas the Barret-Joyner-Halenda (BJH) adsorption and desorption average pore widths were 4.015 and 4.446 nm, respectively. Thus, it was found that rice hull-based activated carbon consisted of mesopores predominantly. These experimental results indicated the potential use of rice hull as a precursor in the activated carbon preparation process with ammonium nitrate. Moreover, the adsorption-desorption isotherm and the adsorption potential of the activated carbon that prepared at the optimum conditions were evaluated.