THE CHARACTERIZATION OF ACTIVATED CARBONS WITH OXYGEN AND NITROGEN SURFACE GROUPS

The physicochemical properties and the surface chemical structure of t he carbon materials obtained by the modification of the commercial act ivated carbon D43/1 (Carbo-Tech, Essen, Germany) were studied. The pre viously de-ashed activated carbon was subjected to the following modif ication procedures: high-temperature treatment (1000 K) under vacuum; oxidation with conc. nitric acid; and ammonia-treatment of annealed an d oxidised carbons at high temperatures. The porous structure and the surface area of the five different carbon samples obtained were estima ted by means of mercury porosimetry and from low-temperature nitrogen adsorption data. The thermogravimetric analysis and the quantitative d etermination of surface functional groups by selective neutralisation of bases and pH-metric titration were carried out. FTIR spectra (trans mission) and X-ray photoelectron spectra (C1s, O1s and N1s) were obtai ned for all the carbon samples and compared with one another. The chan ges in the porosity and the chemical properties of the carbon surface caused by the modification were analysed. Some possible surface functi onal species, their structure and surface state are discussed. (C) 199 7 Elsevier Science Ltd.