Response surface methodology adhering central composite design for the optimization of Zn (II) adsorption using rice husk nanoadsorbent

Abstract

Present study highlights the effectuality of rice husk nanoadsorbent RHN for the removal of Zn (II) from aqueous solution. A peculiar statistical technique central composite design of response surface methodology by using Design-Expert® software version 11 was executed to investigate Zn (II) removal by varying three adsorption parameters such as pH, dose and metal ion concentration. Quadratic model equation and analysis of variance were outlined in the study. Zn (II) removal was found to be 80% at optimum conditions pH 6, dose 0.8 g/L and metal ion concentration 15 mg/L and desirability was near 0.9. To comprehend the nature of adsorption process, linear forms of isotherms were gratified. Langmuir isotherm model was found to be compatible with adsorption data indicating monolayer adsorption on homogeneous active sites of nanoadsorbent with 0.9978 R2. Pseudo-second order kinetic model fitted well to the adsorption data with R2 0.992. Spontaneous and endothermic nature of the process was depicted by thermodynamic study. Adsorption mechanism is reasonably explained by hydrolysis, precipitation, electrostatic interactions and HASB inreaction. The regeneration of RHN was analysed upto three successive cycles.