Optimization of microwave irradiated - coconut shell activated carbon using response surface methodology for adsorption of benzene and toluene

Abstract

Effluents from various industries release volatile organic compounds (VOCs) into the environment which causes serious environmental hazards. Coconut shell-based porous carbons were synthesized using chemical activation with potassium hydroxide (KOH) for adsorption of benzene and toluene. Central composite design of the response surface methodology was used in the optimization of the preparation conditions of the porous carbons. The effects of microwave power, irradiation time, and KOH impregnation ratio (IR) on benzene and toluene removal were investigated. The optimum condition was obtained at microwave power of 500 W; irradiation time 4 min; and 1.5 KOH IR, which resulted in 84 and 85% removal of benzene and toluene, respectively, at 95% yield of activated carbon (AC) from the char. Equilibrium data were fitted to Langmuir, Freundlich, and Temkin isotherms with all the models having R2 > 0.94. The equilibrium data were best fitted by Langmuir isotherm, with maximum adsorption capacity of 212 and 238 mg/g for benzene and toluene, respectively. High surface area of 1,354 m2/g and highly microporous carbon prepared lead to the high adsorption capacities. Pseudo-second-order kinetic model best fitted the kinetic data. The ACs produced can be used to remediate water polluted by VOCs.