Surface Structures of Surface Modified Activated Carbons

Abstract

Three kinds of commercial activated carbons (S, D and P), made from different starting materials and activation methods, were surface-modified after the evacuation at 1000°C by the following procedures: deash-H₂ reduction, H₂O₂ oxidation and air oxidation.Pore structures and surface areas were determined by N₂ gas adsorption, whereas surface species were analyzed by thermogravimetry and mass spectrometry during the heat/evacuation treatment.
The deash-H₂ reduction procedure eliminated almost all of the surface oxygenated species which decomposed to CO, CO₂ and H2O during the heat/evacuation treatment.In contrast, oxidation procedures were effective to generate oxygenated species.The most effective was the air oxidation procedure.In the oxidized samples, it was to be noted that the fraction of the oxygenated sites on the surface was found for the sample S (ZnC1₂-activation) larger than for the samples D and P (gas-activation).
Judging from the composition of desorbed gases, oxygenated surface species such as hydroxylic and carboxylic groups (large CO₂ and H₂O) were deduced to form mainly by the H₂O₂ oxidation.On the other hand, carbonyl, quinoic and carboxylic anhydride groups (large CO and little H₂O) seemed to be produced dominantly by the air oxidation procedure.