This study for the first time designed to modeling and optimize of activation process for removal of cadmium (II) ions by adsorption on oil shale using the response surface methodology. The optimal activation parameters selection was carried out on the basis of three factors by central composite design (CCD). The factors that have been identified are: activation temperature, activation time and massic ratio (mH2SO4/mYC). The capacity of adsorption of the cadmium (II) ions (Qads(mgg-1 )) , was chosen as a response. The measured parameters were found in accordance with the predicted values with a coefficient of determination (R2 ) of 0.92. The model has been confirmed by experimental tests to validate the results obtained. Based on the equation of the model and the desirability function, the activation temperature and activation time significantly affect of the adsorption capacity of Cd (II) ions. According to optimal activation conditions obtained using prediction profiler, the powder of oil shale mixed with H2SO4 at 213.8°C during 30 min in a massic ratio of 1.76, the adsorption capacity of Cd (II) ions is 68.38 (mgg-1 ). Subsequently, the impact of various influential variables such as pH, contact time and dose of activated oil shale were examined. The kinetic, isotherm and thermodynamic studies were found to be in good agreement with pseudosecond order and Langmuir model, respectively. The activated oil shale prepared under optimal activation conditions has a maximal capacity of adsorption equal to 68.02 mgg-1 according to model of Langmuir with BET surface area of 181.35 (m2 g-1 ). The values of thermodynamic parameters (ΔH°, ΔS°, ΔG°) affirm that the removal of Cd (II) ions on the activated oil shale (YCS) is an endothermic process. The (YCS) has great potential for adsorption of Cd(II) ions with regeneration efficiency more than 70%
