OXIDATION OF ACTIVATED CARBON BY HYDROGEN-PEROXIDE - STUDY OF SURFACE FUNCTIONAL-GROUPS BY FT-IR

Outgassed activated carbon was oxidized using H2O2 aqueous solutions and the surface oxygen groups were identified by FT-i.r. spectroscopy. The influence of solution concentration and pH, outgassing and oxidation conditions of the carbon, and the addition of catalytic or stabilizer agents to the oxidizing solution was investigated. The stability of the surface groups was also studied for a series of samples. The surface groups initially present in the carbon were largely OH and C-O-C. Oxidation of material with H2O2 solution, at unchanged pH, increased the OH groups present in the oxidized products. With solutions of pH 2.5 and 11.5, the OH groups decreased and various oxygen groups such as C=O and C...O, or CO2-, were formed. At the lowest pH value, formation of C-O-C structures with an increased number of C-O bonds occurred. Ether structures were lost when outgassing under more drastic conditions and when contact with the oxidizing solution was established at very different temperatures. The addition of Fe2+ to the oxidizing solution favoured the oxidation of carbon. However, Fe3+, ethanol and ether were not effective agents. Significant changes in the surface chemistry of samples were observed after a long period of time.