Abstract In recent years, water quality issues related with hazardous wastewater and toxic substances have attracted worldwide attention. Cyanide is a major toxin in wastewater resulting from a diversity of industries, including gold mining. Cyanide has adverse health effects on people as well as other living organisms. The toxic effects of cyanide are so important to cause nerve damage and thyroid glands malfunctioning. In this paper, the degradation of cyanide in waters resulting from gold mining activity was carried out in a batch system with two catalysts TiO 2 Degussa P-25 and TiO 2 doped with copper heteropolyimolybdate, that was synthesized in laboratory and characterized by FTIR and XRD. Assays showed a degradation of 98.55% with a concentration of 0.3 g/L of TiO 2 and 97.17% with TiO 2 doped with 1% of Cu heteropolyimolybdate (1 g/L) in 50 min of reaction. A real mining sample showed a cyanide degradation of 55.76% with TiO 2 in 240 min of reaction. All the assays were made applying photodegradation using a 125-Watt mercury lamp as source. These results are encouraging to use this technology for the removal of cyanide coming from highly contaminated aqueous effluents.