Activated Carbon Preparation from Cassava Residue Using a Two-Step KOH Activation: Preparation, Micropore Structure and Adsorption Capacity

Activated carbon (AC) was prepared from cassava residue using a two-step activation, including carbonization and subsequent KOH activation. The conditions of activation were optimized through single factor and orthogonal experiments. Heating at 700 °C for 90 min resulted in a charcoal yield of 20%, the optimal condition for carbonization. Factors affecting surface area (S BET) were KOH/char ratio > activation temperature > activation time. The porous structure of the AC was characterized using the physical adsorption of N2 at 77 °K. AC with a S BET of 460–2655 m2/g and pore volume of 0.41–1.198 cm3/g were prepared. Prepared AC had a high proportion of micropores (range: 83.0–92.0%) compared to mesopores. The average diameters of the micropores and mesopores were in the range of 0.991–1.093 nm and 19.37–37.97 nm, respectively. The highest adsorption capacities for formaldehyde and iodine were 295 mg/g and 1387 mg/g, respectively. SEM images demonstrated the topographic structure of the AC.