Application of response surface methodology for the optimization of copper (II) adsorption in aqueous solution using rambutan peel powder biosorbent

Abstract

In this study acid-treated rambutan peel was used as a low-cost agricultural waste-derived biosorbent to remove copper (II) from aqueous solution. Central composite design (CCD) of response surface methodology (RSM) was applied to study the optimization of adsorption capacity and removal efficiency through analyzing the parameters (initial copper (II) concentration, pH and biosorbent dosage) by using Design-Expert software. The optimum conditions of adsorption capacity of copper (II) were: biosorbent dosage = 0.05 g, initial copper (II) concentration = 60 mg/L, pH = 5 whereas for removal efficiency they were: biosorbent dosage = 0.1 g, initial copper (II) concentration = 35 mg/L, pH = 5. The highest adsorption capacity and removal efficiency obtained were 25.33 mg/g and 95.24 %, respectively. Pseudo-first and -second order models and intra-particle diffusion model were applied to study adsorption kinetics. The kinetic data fitted well the pseudo-second order model with R2 of 99.28 %. Characterization of raw and acid-treated rambutan peel biosorbent before and after adsorption was performed with FTIR, SEM and EDS.