Treatment of Activated Carbon with H 2 O 2 . Effect on the Porous Texture

Abstract

The effect of the oxidation of activated carbon (AC) with aqueous solutions of H₂O₂ on the porous texture of the material has been investigated. In such treatments of AC, H₂O₂ solutions of varying concentration and pH (i.e., unchanged pH and pH values of 2.5 and 11.5) were used. Oxidizing solutions containing Fe²⁺, Fe³⁺, ethanol or ether were also employed. Initial outgassing of AC and contact of the intermediate product with the oxidizing solution were effected under controlled conditions of temperature and time. The resulting samples were characterized texturally by gas adsorption (N₂, 77 K) and mercury porosimetry. The mass of sample significantly increased when H₂O₂ solutions at pH 2.5 were used. Such treatment of AC produced a loss of microporosity or none depending on the method of preparation of the samples. Thus, a loss of microporosity occurred, for example, when contact between the H₂O₂ solution and the AC was effected at 0°C, whereas no loss of microporosity occurred when the temperature was 70°C. For a few samples the unfavourable effect of oxidation of the AC on its porous texture not only concerned the micropores but also the mesopores and macropores.