Preparation and characterization of activated carbons from spirit lees by physical activation

Spirit lees was carbonized and then activated by steam and CO2 to prepare activated carbons. The effect of carbonization temperature, type and amount of activator, activation temperature and time on the pore structure, and the adsorption of methylene blue and iodine were investigated. The gas products during activation were analyzed online to reveal the activation mechanism. Results showed that steam activation was rather more active than CO2. Regardless of the activation agent, a low carbonization temperature of 450 °C and a medium activation temperature of 800 °C favored the iodine adsorption. For the methylene blue adsorption, the same low carbonization temperature of 450 °C, however, medium/high activation temperatures (850–900 °C) are favorable. The best activated carbon was prepared with a steam activator using a carbonization temperature of 450 °C and an activation temperature of 800 °C, which had a surface area and pore volume of 371.6 m2/g and 0.34 cm3/g, and iodine and methylene blue adsorption capacities of 580 mg/g and 90 mg/g respectively. O- and H-containing functional groups in the carbonized spirit lees reacted with the activation regent (steam or CO2) to form the initial pores, then the accessible active sites reacted with the activation regent to generate secondary pores.