Ali Mohammad Sanati

The Fe3O4@SiO2 adsorbent was synthesized using amorphous silica extracted from rice husk, functionalized by APTMS group and characterized by vibrating sample magnetometer (VSM), Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Also, response surface methodology was applied to optimize the removal of cadmium ions by synthesized adsorbent in an aqueous solutions. Experiments were conducted based on a rotatable central composite design (CCD) and analyzed using response surface methodology (RSM). The adsorption process was investigated as a function of three independent factors viz. initial solution pH (3-7), sorbent dosage (0.1-2 g.L-1) and initial Cd (II) concentration (10-100 mg.L-1). The optimum conditions for the cadmium adsorption were found to be 5.17, 0.1 g.L-1 and 100 mg.L-1, respectively, for initial solution pH, sorbent dosage and initial Cd (II) concentration. Under these conditions, the removal efficiency and adsorption capacity of the Fe3O4@SiO2-NH2 for removal of cadmium ions were obtained to 58.71% and 305.64 mg.g-1, respectively. Additionally, the obtained value for desirability was equal to 0.722. The theoretical isotherm models were applied to describe the adsorption process that the Langmuir model provides the best correlation of the equilibrium data. The kinetics study reviled that data from the experiments fitted well to the pseudo-second order equation than the pseudo-first order. The thermodynamic parameters reviled that the adsorption process strongly depended on temperature and indicating the exothermic behavior and spontaneous nature of the adsorption.