Heavy Metals Removal from Aqueous Solution by Modified Natural Zeolites Using Central Composite Design

Removal of heavy metals including Pb, Co, Cr and Zn from an aqueous solution was investigated using modified clinoptilolite zeolites as adsorbents. The adsorbents were characterized by X-ray, FTIR, SEM and BET. The central composite design defined under response surface methodology was applied for design of experiments. According to the results, clinoptilolite/MgO showed higher capacity for absorption of lead (98.38 %) in comparison to clinoptilolite/NaOH. The removal percentage of Co, Cr and Zn was obtained 89.51 %, 81.07 % and 78.24 %, respectively, using clinoptilolite/MgO. Moreover, the equilibrium experimental data well fitted the Freundlich isotherm model, as compared with the Langmuir isotherm. The results show that the complete regeneration of adsorbents can be achieved at room temperature using NaCl (0.35 M).