Using response surface methodology to optimize the operating parameters on the sorption of cadmium and surface area of the adsorbent

Abstract In this study, the adsorption of cadmium ions from aqueous solution onto hydroxyapatite was investigated. A series of apatite powders were synthesized under varying conditions of reaction time, reaction temperature and calcination temperature. In addition, the surface area (SBET) of each synthetized powders were measured. To model and optimize both the cadmium adsorption efficiency and the surface area of the prepared apatite, response surface methodology (RSM) was employed. three variables were considered such as: reaction time (time: 1-96 h), reaction temperature (TSol: 20-70°C) and calcination temperature (TCal: 45-655°C). The pH reaction was fixed at 9. The regression models developed showed good agreement with the experimental data, as indicated by high R² values, confirming the adequacy of the fitted models. The optimal conditions for achieving the maximum surface area (SBET) of 98 m²/g were found be: calcination temperature (TCal) of 354.26°C, reaction temperature (TSol) of 41.036°C and maturation time of 48h. For cadmium adsorption, the maximum adsorption yield was obtained for TCal = 235°C, TSol = 17.5°C and time =48h. In the second step, anew parameter such as reaction pH was introduced to study its effect on cadmium removal. The results indicated that when the pH exceeded 9, cadmium removal efficiency decreased, while the maximum adsorption was observed at pH= 8.5.