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

This study has used acid treated rambutan peel biosorbent 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 is at (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 with pseudo-second order model with R2 of 99.28 %. Characterization of raw and acid treated rambutan peel biosorbent before and after adsorption were analyzed with FTIR, SEM and EDS.