Photocatalytic degradation of cyanide using titanium dioxide modified with copper oxide

Copper (II) oxide was loaded onto the surface of Degussa P25 TiO2 particles by photodeposition. The doped material was subsequently utilized as the photocatalyst for cyanide oxidation. The copper content on the TiO2 surface was varied from 0.05 to 10.0 at.% of Cu. It was found that nanosized CuO deposits were present on the surface of TiO2. Modifying TiO2 With CuO changed the optical properties of TiO2 and the onset of absorption was red shifted. The photocatalytic activity of the CuO loaded TiO2 catalysts was measured to determine their ability to oxidize cyanide. It was found that the rate of photooxidation of cyanide assisted with the doped catalyst was improved slightly at 0.10 at.% Cu. Any further increase of the copper dopant concentration decreased the oxidation rate markedly. The presence of Cu2+ ions (0.002-0.5 mM) in the solution also decreased the photocatalytic degradation of CN-. The decrease in the activity was explained in terms of the competition reaction of Cu(I) cyanide complex ions for surface hydroxyl radicals. In all cases cyanide was being oxidized to cyanate, the end product of cyanide photooxidation. (C) 2002 Elsevier Science Ltd. All rights reserved.