THE FLOW OF FLUIDS THROUGH ACTIVATED CARBON RODS: II. THE PORE STRUCTURE OF ACTIVATED CARBON

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Abstract
The flow rates of adsorbable gases through zinc chloride activated carbon rods are considerably greater than might be expected from classical considerations. From data independent of flow measurements, the pore-size frequency distributions of the activated carbon are deduced and a model macropore system presented. It is shown that flow rates of nonadsorbable gases are consistent with a mean macropore diameter of about 3 × 10−5 cm., as well as being consistent with what can be inferred concerning such structures. The macropore system is regarded as an interstitial structure and is described as a random assembly of "bottle necks" joining relatively large void spaces. The assembly is described by means of two constant parameters and one stochastic variable. The mean micro-pore diameter of zinc chloride activated carbons is generally regarded as being of the order of 2 × 10−7 cm. or less. It is shown that no ordinary type of effusive or diffusive flow through pores of the order of 2 × 10−7 cm. can be appreciable compared with the flow through the macropore system, unless surface forces increase flow rates by large factors. In the case of strongly adsorbed gases the anomalous flow rates are ascribed to a flow through the micropore system and hence it is inferred that surface forces introduce large factors tending to increase flow rates in these very small pores.

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