Effects of Alkali/Char Ratio and Activation Temperature on Ultramicropores of Rice Husk Active Carbon

Porous carbons were prepared by KOH activation of rice husk char at alkali/char ratios of 0.6 : 1 to 3 : 1 and activation temperatures from 640 degrees C to 780 degrees C. The obtained porous carbons were characterized using N-2 adsorption and desorption technique, CO2 adsorption, TG-FTIR analyses. The results indicate that the ultramicropore size of the prepared porous carbons is mostly in the range of 0.42-0.70 nm. As the alkali/char ratio increases, the volume of ultramicropores first rises and then diminishes, whereas the volume of ultramicropores tends to decrease monotonously with the increase of activation temperature. A microporous carbon with ultramicropore volume of 0.149 mL/g, ultramicropore fraction of 36.3%, pore volume of 0.411 mL/g, and specific surface area of 774 m(2)/g, can be produced by activation at 640 degrees C at the alkali/char ratio of 1 : 1. The ultramicropore volume of the porous carbons and their CO2 uptake at 10(4) Pa display a strong linear relationship.