Optimization using central composite design (CCD) of response surface methodology (RSM) for biosorption of hexavalent chromium from aqueous media

In this study, unmodified biosorbent was obtained from Arachis hypogea husk and applied to remove hexavalent chromium [Cr(VI)] from aqueous media through batch technique. The independent variables (contact time, pH of the solution and initial Cr(VI) concentration) influencing the adsorption process were optimized by central composite design (CCD) found in response surface methodology of the Design-Expert software 12.0.0 at a fixed temperature of 30 ± 0.5 °C. Furthermore, equilibrium sorption isotherms and kinetics studies were also investigated. The ANOVA component of the CCD indicated that all the process independent variables investigated had significant impacts on the sorption capacity of Cr(VI) by Arachis hypogea husk. The obtained experimental data showed that at the optimized 120 min contact time, 8.0 pH of the aqueous solution and 50 mg/L initial Cr(VI) concentration resulted in an optimum adsorption capacity of 2.355 mg/g. Equilibrium sorption isotherm and kinetic studies showed that Redlich–Peterson adsorption isotherm and pseudo-second-order kinetic models fitted well to the equilibrium data. The unmodified adsorbent from Arachis hypogea husk was found to be efficient for Cr(VI) decontamination from the aqueous media.