COMPARATIVE CATALYTIC ACTIVITY OF SELECTED METAL-OXIDES AND SULFIDES FOR THE PHOTOOXIDATION OF CYANIDE

The photocatalytic oxidation of cyanide by TiO2 (anatase and rutile), ZnS, ZnO, CdS, V2O5, SiO2 and Fe2O3 was investigated and compared with the photo-oxidation in the absence of catalyst. Only TiO2 and ZnO are satisfactory catalysts. Cyanide is first oxidized to cyanate and then via nitrite to nitrate. In most systems cyanide is also volatilized a s HCN. The amount of HCN volatilized is a function of the pH of the so lution and the surface area of the catalyst and generally increases wi th decreasing pH and increasing surface area.