The elimination of cyanide from water by oxidation under UV illumination and using ZnO powder as catalyst has been studied. The study has been carried out by determining the yield of CN- elimination at different irradiation times, initial CN- concentrations, pH, mass of ZnO in suspension, temperatures, and light intensities. The CN- oxidation gives OCN- as an intermediate product, which is further oxidized to CO32-. The greater yields of the CN- photooxidation are obtained at pH = 11. In addition, at this pH the ZnO is highly stable. The ZnO is a good catalyst even under solar irradiation. It has been observed that, after 2 h of solar exposure, 87% of the initial 10-4 M of CN- has been transformed to CO32-. © 1988.