THE ADSORPTION OF CARBON DIOXIDE ON CARBON SOLIDS. PART 1 - GRAPHITE AND DIAMOND AT 0 C.
NAVAL RESEARCH LAB WASHINGTON D C
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The high-temperature physical adsorption of carbon dioxide 1 coverage was measured on a number of relatively well defined carbon solids. The results provide an experimental means to differentiate between two arrays of adsorption sites that originate in the strong anisotropy of the graphite structure. The adsorption isotherms at 0 C indicate two distinct regions of surface coverage that are separated by a wide plateau. The adsorption at very low pressures 0.01 torr is considered to correspond to high-energy adsorption on an array of edge carbon atoms in the prism faces the additional adsorption at higher pressures takes place at sites of lesser energy in the more abundant basal planes. Similar behavior was observed for graphitized carbon black FT 2700 C, nmineral graphite, an annealed pyrolytic graphite, and a deashed heat-treated 1500 C coconut charcoal. In contrast, the adsorption of carbon dioxide on purified natural-diamond fragments followed a simple Langmuir isotherm compatible with the known isotropic structure of diamond. The amounts adsorbed expressed per unit area bring out similarities among the carbon solids that are characteristic of graphite. The large adsorption on the coconut charcoal appears due only to the large area that is essentially basal plane in behavior. There is evidence that the pyrolytic graphite has a porosity that may be invaded more completely by carbon dioxide than by krypton. Author
- Industrial Chemistry and Chemical Processing
- Physical Chemistry
- Life Support Systems