Chlorine and oxygen on the carbon surface

A series of carbons have been prepared with slight variations in oxygen con tent by treating BPL carbon with hydrogen at a number of temperatures and b y ageing samples in a humid environment. These carbons were subsequently ch lorinated at 180 degrees C and washed to remove physisorbed chlorine. For t he original oxidised series the primary water adsorption sites were observe d to decrease with decreasing oxygen content determined from temperature-pr ogrammed desorption. The immersional enthalpy in water increased with incre asing oxygen concentration on the surface of the carbon as did the number o f hydrophilic surface sites measured by preferentially adsorbing 1-butanol from heptane. The relationships established for the oxidised carbons did no t fit the chlorinated series with preliminary indications that the interact ion 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 ne ighbouring chlorine atoms. Chlorination of the surface also appears to alte r the measurement of hydrophilic oxygen sites and the interaction of water with the porous carbon structure. (C) 2000 Elsevier Science Ltd. All rights reserved.