Commercial activated carbon was treated with a non-thermal oxygen plasma under atmospheric pressure using three types of reactors: a dielectric barrier discharge (DBD) parallel-plate reactor; an atmospheric pressure glow discharge plasma jet reactor and a DBD coaxial type reactor. The samples treated with the plasma were characterized by the pH value at the point of zero charge. An estimation of the adsorption properties of samples for copper ions in aqueous solution was also carried out in order to explain the effect of pH value on the adsorption results. (c) 2005 Elsevier B.V. All rights reserved.