Correlation of water adsorption isotherms with oxygen groups on carbon black surfaces

The adsorption of polar molecules, such as water and alcohols, on carbon surfaces is strongly dependant on specific, hydrogen bonding, interactions which occur with polar sites, usually oxygen functional groups, on carbon surfaces. In this paper we correlate the surface oxygen levels of non-porous carbon blacks, controlled using ozone oxidation and quantified by x-ray photoelectron spectroscopy, with the precise shape of vapour adsorption isotherms and with enthalpies of immersion (-hi /mJm) for water. Resulting Type III adsorption isotherms are displaced to higher adsorption values as the carbon total surface oxygen level [O]T (atomic %), measured by XPS, increases. The data are analysed using the Dubinin-Serpinsky equation and the resulting parameter, a0, which describes the surface concentration of primary polar adsorption sites, shown to correlate with [O]T which also influences both the degree of fit to the equation and the limiting experimental water adsorption value as.