Bimetallic (Pd/Cu) catalysts supported on alumina were used for the degradation of nitrates in water. The reduction temperature strongly affects the surface and oxidation states of the metals on the catalysts. These significant changes were characterized by FT-IR, XPS, TEM with EDX and H-2 chemisorption. Migration of superficial copper on top of palladium and towards the support during the reducing steps was observed, moreover palladium particles free of copper were found. With increasing reduction temperature the activity of the bimetallic catalysts passes through a maximum whereas the selectivity to nitrogen increases. (c) 2005 Elsevier B.V. All rights reserved.