The effects of chemical pretreatments of the support on CO oxidation over the activated carbon-supported Wacker-type catalyst were studied. Dry oxidation by air at 400 degrees C and wet oxidation in H(2)O(2) and H(3)PO(4) aqueous solution were used to modify the physical and chemical properties of activated carbon The textural and surface characteristics of activated carbons were characterized by nitrogen adsorption, temperature-programmed desorption (TPD) and Boehm titration. The dispersion of active phase and chemical environment of CO oxidation catalysts were investigated by X-ray Photoelectron Spectroscopy (XPS) and temperature-programmed reduction (TPR) CO oxidation results showed that the catalyst prepared using activated carbon with high mesopores and oxygen-functional groups as support pet forms higher CO oxidation activity at ambient temperature, especially in high relative humidity XPS and TPR results show that the activated carbon support with enriched oxygen-functional groups would benefit the distribution of active components (Pd(2+), Cu(2+)) on the catalyst surface and the formation of easily reducible Cu(2+) species (C) 2010 Elsevier B.V. All rights reserved