Activated carbons were prepared from such low-rank coals as weathered coal (Inner-Mongolia, China; C: 53.5%, Ash: 19.0%) and brown coal (Yallourn, Australia; C: 63.6%, Ash: 1.4%) with a large quantities of sodium hydroxide under a lower temperature (773-973K) to the conventional steam activation (1073-1273K). By these operations, activated carbons with moderate values of specific surface area (Sg=1320m^2/g) were obtained with high yields (Y=22-45%) to the raw materials. The heat-treated decarboxylation of weathered coal enhanced greatly the effectiveness of activation by alkali, affording the Sg value of more than 1000m^2/g. The elimination of ash, especially silica in the weathered coal, was performed easily with alkali by the washing of the final product while the activation was processed. The ash content of the activated carbon from weathered coal was 4.0% at least, while almost nil for the product from brown coal.
