Introduction of acidic groups at the surface of activated carbon by microwave-induced oxygen plasma at low pressure

Functional groups at the surface of a commercial granulated activated carbo n were modified at low temperature in an oxygen plasma. Changes in the chem istry of the surface were monitored by thermal desorption, titration of aci dic groups, and XPS. A comparison of untreated and plasma-treated carbons, both before and after acid-washing and crushing, showed that reactions in o xygen plasma yield a low surface acidity with minimal modification of the i nitial sample porosity. Carboxylic groups, which are largely responsible fo r the surface acidity, appear to be unstable in the presence of the most re active oxygen species of the plasma. (C) 2000 Elsevier Science Ltd. All rig hts reserved.