Batch adsorption of cadmium ions from aqueous solution by means of olive cake

The use of natural adsorbent such as olive cake to replace expensive imported synthetic adsorbent is particularly appropriate for developing countries such as Jordan. In this study, batch adsorption experiments were carried out for the removal of cadmium ions from its aqueous solution using olive cake as adsorbent. Parameters effects such as temperature, pH and adsorbent dose on the adsorption process were studied. The adsorbent used in this study exhibited as good sorption at approximately pH 6 at temperatures 28, 35 and 45 degrees C. The removal efficiency was found to be 66% at pH 6 and temperature 28 degrees C. The equilibrium data were analyzed using Langmuir and Freundlich isotherm models to calculate isotherm constants. The experimental results were in a good agreement with these models. Results show that when an increasing in temperature from 28 to 45 degrees C, the maximum adsorption capacity (q(max)) is decreased from 65.4 to 44.4 mg/g and Freundlich constant (K-f) decreased from 19.9 to 15.7. The thermodynamic parameters for the adsorption process data were evaluated using Langmuir isotherm. The free energy change (Delta G degrees) and the enthalpy change (Delta H degrees) showed that the process was feasible and exothermic, respectively. The dynamic data fitted to the first order, Lagergren-first order and pseudo second-order kinetic models. The experimental results indicated that the pseudo second-order reaction model provided the best description for these data with a correlation coefficient of 0.99. The adsorption rate constant was calculated as 8.4 x 10(-3) g mg(-1) min(-1) at 28 degrees C. (c) 2007 Elsevier B.V. All rights reserved.