STRUCTURAL AND SURFACE-PROPERTIES OF ACTIVE CARBONS OXIDIZED WITH NITRIC-ACID AT HIGH-TEMPERATURE

The effect of oxidation of active carbons with nitric acid at the boil ing temperature on their structural and surface properties was analyze d by nitrogen and water vapor adsorption data. Adsorption isotherms on unmodified and oxidized active carbons were measured at 77 K for nitr ogen and 298 K for water vapor. This oxidation of active carbons led t o formation of a significant amount of oxygen acidic groups on their s urfaces. Simultaneously this oxidation led to a considerable degradati on of the porous structure, which is manifested by decreasing: the tot al surface area, the micropore volume, and the external surface area o f mesopores. However, adsorption of water vapor on oxidized active car bons under low and moderate pressures is considerably greater than on unmodified carbons.