Optimization of the preparation of Millettia thonningii seed pods activated carbon for use in the remediation of dye-contaminated aqueous solutions

Abstract

An increasing research interest in the use of waste-derived activated carbon in the remediation of contaminated water as a renewable alternative to commercial activated carbon has been noted. This research evaluates the optimization of the preparation of activated carbon from Millettia thonningii seed pods for application in the removal of synthetic dyes from aqueous solutions. The Box–Behnken experimental design, a subset of response surface methodology is employed in this research as it provides an economical strategy to optimize the process using a minimal number of experiments. The effect of preparation factors such as activation temperature, activation time and impregnation ratio on the preparation process was evaluated and these conditions optimized by maximizing the activated carbon yield and the adsorption efficiencies of two synthetic dyes, Basic Violet 3 and Basic Blue 9. The optimal conditions established were activation temperature of 400 °C, activation time of 30 min and impregnation ratio of 2.0. The activated carbon yield, Basic Violet 3 and Basic Blue 9 adsorption efficiencies approached 39.12%, 83.25% and 91.05% respectively under these optimal experimental conditions. The optimized activated carbon was characterized via physicochemical and proximate analysis, Fourier transform infrared spectroscopy and scanning electron microscopy. Millettia thonningii seed pods activated carbon produced at the optimum activation conditions possessed desirable properties such as low ash content, low moisture content and suitable bulk density. The activated carbon also holds great potential for application in the removal of hazardous synthetic dyes from wastewater.