Optimizing Adsorption of Co(II) and Ni(II) by 13× Molecular Sieves Using Response Surface Methodology

Abstract

Batch experiments were carried out to investigate the adsorption characteristics of Co(II) and Ni(II) by 13× molecular sieves which are hydrothermally synthetic byproducts accompanied with preparation of potassium carbonate from insoluble potash ores. The response surface methodology technique was utilized to optimize the process conditions. The combined effects of the major parameters including pH, initial concentration of metal ions, and temperature on the adsorption were investigated using central composite design. The analysis of variance of the quadratic model suggested that the predicted values were in good agreement with experimental data. The optimum conditions were found to be: initial concentration of metal ions, 20 mg/L; temperature 40 °C for both the metals; and pH, 6.29 and 8.0 for Co(II) and Ni(II), respectively. Scanning electron microscope and X-ray diffraction analyses testified to the obvious change of the surface morphology and the presence of metal on the sorbent after adsorption. The results from the sequential adsorption–desorption cycles showed that 13× molecular sieves adsorbent held good desorption and reusability.