The analysis of surface and pores of activated carbons by the adsorption of various gases

The analysis of surface and pores of activated carbons oxidized to various degrees has been carried out on the basis of adsorption isotherms of nitrogen, water and several organic compounds. The reason for the large hysteresis of isotherms of water was ascribed to the structure formation of water in the micropores caused by the hydrophobic interaction at water-carbon inferface. INTRODUCTION The surface of activated carbons has been characterized from physical, chemical and industrial points of view by many researchers. Among them, the pore structure analysis has been carried out on adsorption isotherms of microporous carbons such as molecular sieve carbons and carbon fibers intensively for the purpose of physical characterization. The influence of oxidative and reductive treatment of this material at various temperatures upon the surface properties is also one of the most important subjects to study from chemical view point. The surface oxidation of this material by various means gives a drastic change to the surface area and pore size as well as to chemical properties such as hydrophilicity to the hydrophobic surface. The adsorption isotherms o f various nonpolar and polar gases on this material can supply interesting information of not only of physical characterization such as micrLporosity and fractal property, but also chemical nature such as acidity and hyrophilicity can be studied. The physical and chemical characterization is studied in this report on an activated carbon oxidized to various degrees with nitric acid. The detailed analysis of adsorption isotherms of various nonpolar and polar compounds gave some interesting results. MATERIALS Granular activated carbons “DIAHOPE” of Mitsubishi Chemical made by steam activation of coal were ground to powder less than 75 mesh. This material was boiled with nitric acid solution of 1, 6 and 12 mol/l concentration for 1 h. The original and acid treated materials were washed repeatedly with pure water until