Evaluation of cyanide removal processes on water effluents from gold ore processing and industrial scale up

Gold extraction goes through different steps, from research to physical-chemical processing, which uses chemical reagents for extraction, such as cyanide. In literature, there are presented many ways to remove cyanide from this effluent on a bench scale, although on an industry scale it is not very often analysed. In this study, seeking innovation on an industrial scale for cyanide removal from real effluent generated by gold processing was analysed through oxidation with H2O2 and Fenton process. It was proven that these processes can remove cyanide at the levels required for recirculation of the effluent in the process, which is 1.0 mg/L of free cyanide, reaching 99% of removal. Applying the treatment on an industrial scale, it was possible to obtain the removal of 89% of free cyanide and 90% of total cyanide. A statistical study was carried out using a DOE tool to evaluate the dosages of H2O2 and FeCl2 at different pH values to reduce the operational costs of this decontamination process. The results indicated that it is possible to remove cyanide to reuse the effluent, with results higher than 96% of removal, using 88% less H2O2 and 70% less FeCl2, monitoring pH at 3, resulting in less waste operation for the treatment of the effluent.