Treatment of Activated Carbon with H2O2. 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.