Comparison and analysis of one- and two-step activation for preparation of activated carbon from furfural residues

Activated carbon (AC) was prepared from furfural residue (FR) in a horizontal tube reactor under a carbon dioxide atmosphere comparing one- and two-step activation methods. Considerable differences were observed between ACs produced from these two methods in microscopic morphology, structural properties, organic structure, and crystallinity. It showed that the AC obtained by one-step activation (800 oC, 20 min, K2CO3: FR = 0.5:1) exhibited microporous and alkaline surface characteristics, and achieved the highest iodine value of 1305.7 mg/g and BET surface area 2083.6 m2/g. While, for the two-step method, the iodine value was 1004.9 mg/g and the BET surface area was only 726.3 m2/g. Furthermore, one-step activation obtained a higher yield of high-quality AC in a shorter activation time than the two-step method. The adsorption data fitted well with the Redlich-Peterson isotherm model and reached the highest value of 1761.1 mg/g, while the adsorption kinetics agreed well with the pseudo-second-order model.