Taguchi optimization approach for production of activated carbon from phosphoric acid impregnated palm kernel shell by microwave heating

• Robust Taguchi optimization method is used.
• A separate array for noise factor (particle size) was used.
• Microwave heating instead of the conventional heating in muffle furnace.
• Reduction of the production cost of activated carbon.
• Palm kernel shells were used as raw material and H3PO4 as impregnating material.

Taguchi method was applied to investigate the optimal operating conditions in the preparation of activated carbon using palm kernel shell with quadruple control factors: irradiation time, microwave power, concentration of phosphoric acid as impregnation substance and impregnation ratio between acid and palm kernel shell. The best combination of the control factors as obtained by applying Taguchi method was microwave power of 800 W, irradiation time of 17 min, impregnation ratio of 2, and acid concentration of 85%. The noise factor (particle size of raw material) was considered in a separate outer array, which had no effect on the quality of the activated carbon as confirmed by t-test. Activated carbon prepared at optimum combination of control factors had high BET surface area of 1473.55 m² g−1 and high porosity. The adsorption equilibrium and kinetic data can satisfactorily be described by the Langmuir isotherm and a pseudo-second-order kinetic model, respectively. The maximum methylene blue adsorbing capacity suggested by the Langmuir model was 1000 mg g−1.