The creation of acid carbon surfaces by treatment with (NH4)2S2O8

Two activated carbons with different degree of activation, 20 and 46% burn-off, were obtained from olive stones by steam activation. These samples were oxidized with a concentrated solution of (NH4)(2)S2O8 for different periods of time, up to a maximum of 24 hours, studying the variation in surface area, pore texture and surface chemistry during the oxidation process. The surface area and porosity was studied by N-2 and CO2 adsorption, mercury porosimetry, and helium and mercury densities. The surface complexes were characterized by temperature programmed desorption and FTIR techniques, selective neutralization, and mass titration. Detailed studies are made of the kinetics of the formation of CO and CO2-evolving groups and of their nature and structure. (C) 1997 Elsevier Science Ltd.