Chlorine and oxygen on the carbon surface Original Research Article

A series of carbons have been prepared with slight variations in oxygen content by treating BPL carbon with hydrogen at a number of temperatures and by ageing samples in a humid environment. These carbons were subsequently chlorinated at 180°C and washed to remove physisorbed chlorine. For the original oxidised series the primary water adsorption sites were observed to decrease with decreasing oxygen content determined from temperature-programmed desorption. The immersional enthalpy in water increased with increasing oxygen concentration on the surface of the carbon as did the number of hydrophilic surface sites measured by preferentially adsorbing 1-butanol from heptane. The relationships established for the oxidised carbons did not fit the chlorinated series with preliminary indications that the interaction of water with the oxygen functional groups is reduced from about 17 kJ mol−1 atomic oxygen on the surface to 5 kJ mol−1 by the influence of neighbouring chlorine atoms. Chlorination of the surface also appears to alter the measurement of hydrophilic oxygen sites and the interaction of water with the porous carbon structure.