Nickel ions removal from aqueous solutions using natural zeolite: Optimization and modeling using response surface methodology based on central composite design

Natural clinoptilolite was tested as a low-cost adsorbent for Ni(II) removal from aqueous solutions. In order to reduce the total number of experiments to achieve the best conditions of the batch sorption procedure, response surface methodology based on central composite design was carried for the natural zeolite. Four independent variables, viz. initial nickel ion concentration (10-200 mg/L), adsorbent dose (0.1-0.7 g/L), contact time (5-120 min) and initial pH of solution (2-8) were transformed to coded values and quadratic model was built to predict the responses. Very high regression coefficients between the variables and the response indicate excellent evaluation of experimental data by second-order polynomial regression model. Three dimensional plots demonstrates relationships between the nickel ion uptake with the paired factors (when other factor was kept at its optimal level), describing the behavior of sorption system in a batch process. The model showed that nickel uptake in aqueous solution was affected by all the four factors studied. On the basis of experimental results and model parameters, it can be inferred that the adsorbent which has quite high adsorption capacity can be utilized for the removal of nickel from aqueous solution.

Keywords:

Nickel ion removal Natural zeolite , Batch method , Central composite design , Response surface methodology