Optimization of Copper and Zinc ions removal from aqueous solution by modified Nano-bentonite using Response surface methodology

In recent decades, the presence of heavy metal ions in wastewater has become an important public concern worldwide. Adsorption is a commonly used technique for removing various types of materials including metal ions from contaminated water sources. However, common methods for adsorption are not completely efficient at low ion concentrations; therefore, adsorbents should be improved in order to reach an acceptable level of adsorption efficiency. In this study, the removal of two heavy metals ions, zinc and copper, from synthetic aqueous solution using Nano-bentonite was investigated. Modified bentonite was obtained by calcination of bentonite at 600 ⁰C for 2h. Response surface methodology (RSM) and central composite design (CCD) were used to optimize the operating factors of the adsorption process. Operation time, adsorbent dosage, ion concentration and pH were the variables and percentage of ion removal was considered as the response. HCl and NaOH were used as chemical agents to adjust pH at optimum level of operating condition for Cu^2+ and Zn^2+ removal which were as follows: Cu^2+ initial concentration: 110.1 mg/L, pH:7.3, time: 96.8 min, adsorbent dosage: 2.1 g/l, and Zn^2+ initial concentration: 105 mg/L, pH: 6.9, time: 73.1 min and adsorbent dosage: 2 g/l. Results and 3D plots exhibited significant proof for accepting the competence of the modified Nano-bentonite as an efficient adsorbent for metals ion removal.