An investigation was made of the effects of surface properties on the uptake of phenol by carbonaceous adsorbents and on subsequent regeneration by acetone leaching. As-received carbons derived from different source materials were evaluated at pH values 2 and 9, and the surface properties of selected adsorbents were varied by surface oxidation with concentrated HNO3 and/or heat treatment under nitrogen. Carbons derived from different source materials exhibited similar total uptake and reversible (acetone extractable) uptake at pH 2 but exhibited a wide range of reversibility at pH 9, conditions that promote oxidative coupling reactions. Surface acidity was investigated as a factor contributing to the reversibility of as-received carbons, and surface oxidation was evaluated as a means of improving regenerability. Oxidation of coal-and wood-based adsorbents with concentrated HNO3 increased surface acidity as measured by Boehm titration techniques and reduced the uptake of phenol but increased the reversible uptake. Reversibility was found to correlate with total acidity, reaching an upper plateau at a surface acidity of about 1 mu equiv/m(2). Uptake of water vapor by surface-treated carbons correlated with surface acidity, suggesting that selectivity for water may contribute to the suppression of oxidative coupling reactions.