Response surface modeling of copper (II) adsorption from aqueous solution onto neem (Azadirachta indica) bark powder: Central composite design approach

In this work the individual and combined effect of four process parameters, i.e. initial copper (II) concentration, adsorbent dose, initial solution pH, and contact time on the adsorption of copper (II) from aqueous solution were studied by neem bark powder (NBP) using response surface methodology (RSM) approach based on central composite design (CCD). Copper (II) removal is maximum at the pH: 5, adsorbent dose: 0.9 g/50 ml, contact time: 90 min and initial copper (II) ion concentration: 62.5 mg/L. Analysis of variance (ANOVA) showed the relative significance of process parameters in removal process. The R 2 , adjusted R 2 and predicted R 2 values showed a good agreement between the actual and the predicted values. Process variables were optimized by desirability function. Thermodynamic parameters such as Gibbs free energy (∆G o ), the enthalpy (∆H o ) and the entropy change of adsorption (∆S o ) have also been evaluated and it has been found that the adsorption process was spontaneous, feasible and endothermic in nature. Received 11 Mar 2016, Revised 28 Mar 2017, Accepted 01 Apr2017