The characterization of activated carbons with oxygen and nitrogen surface groups

The physicochemical properties and the surface chemical structure of the carbon materials obtained by the modification of the commercial activated carbon D43/1 (Carbo-Tech, Essen, Germany) were studied. The previously de-ashed activated carbon was subjected to the following modification procedures: high-temperature treatment (1000 K) under vacuum; oxidation with conc, nitric acid; and ammonia-treatment of annealed and oxidised carbons at high temperatures. The porous structure and the surface area of the five different carbon samples obtained were estimated by means of mercury porosimetry and from low-temperature nitrogen adsorption data. The thermogravimetric analysis and the quantitative determination of surface functional groups by selective neutralisation of bases and pH-metric titration were carried out. FTIR spectra (transmission) and X-ray photoelectron spectra (Cls, Ols and Nls) were obtained for all the carbon samples and compared with one another. The changes in the porosity and the chemical properties of the carbon surface caused by the modification were analysed. Some possible surface functional species, their structure and surface state are discussed.