Removal of arsenic(III) ions from aqueous solutions by modified hazelnut shell
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In this study modified hazelnut shells (HS) were used to remove As(III) ions from aqueous solutions. For this purpose, FeCl3 and FeCl3 + NaOH were used as modifying agents. Several important parameters influencing the adsorption of As(III) ions such as contact time, pH, temperature and initial metal concentration were investigated following batch experiments. From the results, it is indicated that temperature 20 degrees C and solution pH = 9.0 are the optimum conditions for adsorption. Maximum adsorption experimental capacities of HS that was treated with FeCl3 and FeCl3 + NaOH were 4.37 and 11.84 mg g(-1) for arsenic, respectively. The adsorption data at optimum conditions were analyzed by Freundlich, Langmuir, Dubinin-Radushkevich and Temkin isotherm models, and it was found that Freundlich isotherm model gives better fit. Thermodynamic parameters such as enthalpy change (Delta H degrees), entropy change (Delta S degrees) and free energy change (Delta G degrees) were also calculated. These results were indicated that the adsorption of arsenic on HS is exothermic and proceeds spontaneously Additionally, it can be said that these adsorptions are physical because the Gibbs free energy change (Delta G degrees) for both adsorbents were found lower than 20 kJ mol(-1).