Preparation of activated carbon
Ten grams of rice husk ash after acid pre-treatment was uniform mixed with K2CO3 powder in a porcelain reactor at a certain impregnation ratio. Then the reactor was put into a tube furnace, which was heated to a designed temperature under nitrogen flow for a certain period of time. In this procedure, the energy can be provided by bio-oil. The combustion heat of oil which comes from pyrolysis rice husk is 25.72 MJ/kg. The system was cooled to 100 °C within, and then transferred to a covered 500 mL three-necked flask. A certain amount of water was added to the covered three-necked flask. The suspension was kept boiling for 30 min under reflux condenser and vigorous stirring conditions. Finally, the dispersions were filtered. The activated carbon was washed thoroughly with distilled water and dried for 12 h at 120 °C, and the filtrate was transferred into a carbonating reactor to prepare silica.