SOLAR PHOTOCATALYTIC DETOXIFICATION OF CYANIDE EFFLUENTS FROM METAL FINISHING INDUSTRY

Abstract

Wastewaters from metal ? nishing industry contain, among other pollutants, high amounts of cyanide and heavy metals, which results in a high toxicity of the effluent. Therefore, it is necessary to detoxify the effluent before discharging to a sewage treatment plant which commonly consists in a biological treatment.In this study, we analyzed different photocatalytic methods for cyanide removal: photo-Fenton, Fenton-like with metals such as manganese, zinc, silver, cobalt, chromium and copper and photocatalysis with addition of other oxidants such as persulfate.Initially, we performed a study on synthetic water prepared with contaminants found in real wastewater. In order to better simulate real conditions, the possible interferences from ions usually present in water, such as carbonates, sulfates, fluorides or nitrates has been studied. The best treatment (Fenton-Like) was applied to real wastewaters from a metallurgical industry of the east of Spain, containg high amounts of copper.The global analysis of the treatments determined that the best results were obtained by applying solar photo-Fenton process and photo-Fenton-like processes with copper. The total degradation of cyanide and copper precipitation was achieved, improving the characteristics of the treated effluent.