On the characterization of acidic and basic surface sites on carbons by various techniques

Active carbons of different origins have been oxidized with H O and (NH ) S O and their oxygen surface complexes 2 2 4 2 2 8 have been characterized by TPD, classical titration following Boehm’s method and by neutralization calorimetry. The net enthalpies of neutralization, determined by immersion calorimetry into NaOH and HCl 2 N lead to 241.161.8 and 21 21 252.362.0 kJ eq for the acidic and basic sites on the surface. Experiments with NaHCO lead to 239.761.7 kJ eq for 3 the carboxylic groups alone. These results suggest that the surface groups of active carbons can also be characterized by immersion calorimetry. Results are also given for the variation of the pH of the point of zero charge with the total oxygen content of the surface.  1999 Published by Elsevier Science Ltd. All rights reserved.