Modification of the structure of an active carbon by heat treatment

Abstract

A series of active carbons was prepared by combination of activation (by steam, at 1173 K) and by heat treatment (at 1523 K, 2 h under nitrogen) and the structures of the samples were investigated by gas adsorption (nitrogen adsorption isotherms) and by' X-ray scattering. An agreement is observed between the average chord length of segments in the solid phase measured by SAXS and the average micropore size determined by gas adsorption, suggesting that the diameters of micropores formed during the activation and the heat treatment have nearly the same size as the crystallites. The qualitative selection criteria of active carbons for industrial (technological) applications are given by their adsorption properties. Some direct relationships exist between the adsorption properties and the structure of the active carbons as shown by Jfinosi & Stoeckli (1979) and Dubinin (1980. 1982). These investigations show that the adsorption properties are also sensitive to the kind of surface. Therefore, we could study only the relationship between the pore structure and the structure of the matrix of those samples which have the same quality of surface. This is performed by studying a series of active carbons, which was prepared from the same carbonized basic material by changing the technological parameters.