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    Öğe
    Equilibrium and kinetic studies of copper (II) ion uptake by modified wheat shells
    (Desalination Publ, 2012) Aydin, Haluk; Yerlikaya, Cigdem; Uzan, Serhat
    Natural adsorbents such as shells of unmodified wheat (RW), and modified wheat (MW) were assessed for Cu(II) adsorption from aqueous solutions. The removal of Cu(II) by these adsorbents from aqueous solution was investigated by using several parameters such as modificiation, contact time, temperature and pH. The extent of Cu(II) removal increased with increasing contact time, temperature and pH and also with modification by Reactive Orange 122 of adsorbent. The experimental data were analysed by the Langmuir and Freundlich models of adsorption. It was found that the Freundlich equation fits better than the Langmuir equation. In addition, the adsorption data obtained at different temperatures of Cu(II) by adsorbents were applied to pseudo first-order, pseudo second-order and Weber-Morris equations, and the rate constants of first-order adsorption (k(1)), the rate constants of second-order adsorption (k(2)) and diffusion rate constants (k(3)) at these temperatures were calculated, respectively. The rates of adsorption were found to conform to pseudo second-order kinetics with good correlation (R-2 >= 0.989). The data obtained from adsorption isotherms at different temperatures were used to calculate some thermodynamic quantities such as free energy of adsorption (Delta G degrees), enthalpy (Delta H degrees), and entropy (Delta S degrees). It is found that Delta G degrees is negative, indicating that the nature of adsorption process for Cu(II) is spontaneous. The positive value of Delta H degrees indicates that the adsorption of Cu(II) onto adsorbents is an endothermic process. The positive value of Delta S degrees reflects the affinity of the adsorbent for Cu(II). As a result, the present work indicates that the wheat shells MW chemically by Reactive Orange 122, possess more efficiency in adsorbing Cu(II) ions than the unmodified one (RW).
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    Öğe
    Removal of copper (II) from aqueous solution by adsorption onto low-cost adsorbents
    (Academic Press Ltd- Elsevier Science Ltd, 2008) Aydin, Haluk; Buluta, Yasemin; Yerlikaya, Cigdem
    The use of low-cost adsorbents was investigated as a replacement for current costly methods of removing metals from aqueous solution. Removal of copper (11) from aqueous solution by different adsorbents such as shells of lentil (LS), wheat (WS), and rice (RS) was investigated. The equilibrium adsorption level was determined as a function of the solution pH, temperature, contact time, initial adsorbate concentration and adsorbent doses. Adsorption isotherms of Cu (II) on adsorbents were determined and correlated with common isotherm equations such as Langmuir and Freundlich models. The maximum adsorption capacities for Cu (11) on LS, WS and RS adsorbents at 293, 313 and 333 K temperature were found to be 8.977, 9.510, and 9.588; 7.391, 16.077, and 17.422; 1.854, 2.314, and 2.954 mg g(-1), respectively. The thermodynamic parameters such as free energy (Delta G(0)), enthalpy (Delta H-0) and entropy changes (Delta S-0) for the adsorption of Cu (II) were computed to predict the nature of adsorption process. The kinetics and the factors controlling the adsorption process were also studied. Locally available adsorbents were found to be low-cost and promising for the removal of Cu (II) from aqueous solution. (C) 2007 Elsevier Ltd. All rights reserved.
  • [ X ]
    Öğe
    Utilization of shells of hazelnut modified with Reactive Orange 122 as adsorbent for the removal of Cu(II)
    (Desalination Publ, 2010) Aydin, Haluk; Yerlikaya, Cigdem
    The influence of reactive dye modification on the efficiency of adsorption capacities of hazelnut shells was investigated. To that end, natural adsorbents such as shells of unmodified hazelnut (RH), and modified hazelnut (MH) were used. The removal of Cu(II) by these adsorbents from aqueous solution was investigated by using several parameters such as modification, contact time, temperature and pH. The adsorption process attained equilibrium within 60 min. The extent of Cu(II) removal increased with increasing the contact time, temperature and pH and also with modification by Reactive Orange 122 as the adsorbent. Optimum pH value for Cu(II) adsorption was determined between 4-5. The experimental data were analysed by the Langmuir and Freundlich models of adsorption. It was found that the Langmuir equation fited better than the Freundlich equation. The maximum adsorption capacities for Cu(II) onto RH and MH at 298, 308 and 318 K were found to be 3.95, 4.65, and 4.74, 7.00, 8.12 and 8.61 mg/g, respectively. In addition, the adsorption data obtained at different temperatures of Cu(II) by adsorbents were applied to the pseudo first-order, pseudo second-order and Weber-Morris equations, and the rate constants of the first-order adsorption (k(1)), the rate constants of the second-order adsorption (k(2)) and intraparticle diffusion rate constants (k(3)) at these temperatures were calculated, respectively. The rates of adsorption were found to conform the pseudo second-order kinetics with good correlation (R-2 >= 0.991). The data obtained from the adsorption isotherms at different temperatures were used to calculate some thermodynamic quantities such as free energy of adsorption (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees). It is expected that Delta G degrees is negative, indicating that the nature of the adsorption process for Cu(II) is spontaneous. The positive value of Delta H degrees indicates that the adsorption of Cu(II) onto adsorbents is an endothermic process. The positive value of Delta So reflects the affinity of the adsorbent for Cu(II). As a result, the hazelnut shells (both modified and unmodified), inexpensive and easily available material, can be an alternative for more costly adsorbents used for Cu((II) removal from wastewater.