Surface and sorption properties of active -carbons

Summary

• 1. Pairs of samples of active carbon were prepared, each pair being such that the two carbons were very close in porous structure but were distinguislied by the presence in one of acidic surface oxides-, these oxides were absent in the other. which was freed from them by thermal treatment in a vacuum at about 1000′. It was proved that the samples of carbon chosen for comparison were almost identical in porous structure, although differing in the nature of their surfaces.

• 2. A study was made of the sorptive properties of carbons with respect to a nonpolar substance, benzene. It was shown experimentally that acidic surface oxides have no appreciable effect on the sorptive power of carbon for benzene vapor over a wide range of equilibrium pressures.

• 3. The sorption and desorption isotherms of water vapor were investigated for carbons containing acidic surface oxides and for the corresponding carbons freed from these oxides. It was found that the surface oxides had a very considerable effect on the sorptive power of carbons for water vapor, the effect being manifested in the sorption and desorption isotherms of the oxidized carbons by a displacement of the curve in the region of low relative pressure.

• 4. The basic causes for the differences in the adsorption properties of active carbons differing in the chemical nature of their surfaces were examined.