Co-producing Active Carbons and Sodium Silicate from Pyrolyzed Rice Husk by CO_2 Activation Coupled with NaOH Solution Boiling

摘要

Active carbon and sodium silicate were produced simultaneously from pyrolyzed rice husk (PRH) by CO_2 activation coupled with NaOH solution boiling. Doehlert matrix and Derringer's desirability function were applied to optimizing the boiling conditions to achieve a large specific surface area, a high silica extraction and low alkali consumption. In terms of this purpose, the optimum condition was determined as boiling CO_2-activated char with 1mol/L NaOH solution at a liquid/solid ratio of 9.7 mL/g. Under this condition, the modulus of the sodium silicate and the specific surface area (SSA) of the active carbon were 2.62 and 897 m~2/g, respectively. The values both reached their respective commercial levels. The pretreatment of the PRH with CO_2 activation can markedly increase the SSA of active carbons.