Characteristics and sources of cyanide-containing wastewater in gold production

Cyanide is the main solvent of gold . It is the main method of gold extraction by wet method. The production process is simple, the cost is low, and the recovery rate of gold is high. However, the main disadvantage is that it is very toxic. It contains a large amount of simple cyanide, complex cyanide and sulfide cyanate and other impurities. Due to the high toxicity, the damage to the environment is also serious, and the treatment is quite difficult. Due to the different material composition characteristics of the ore, the gold production method used is not the same, so different cyanide-containing wastewater is produced. Such as:

1. The zinc powder produced by waste water displacement method gold cyanide solution, a gold precipitate was replaced by zinc, zinc cyanide is dissolved in the solution. The solution after being replaced by zinc is mainly divided into cyanide, such as NaCN, complex cyanide formed by cyanide ions and metal ions such as Zn2+, Fe2+, Fe3+, Cu2+, Cu+, such as copper cyanide complex Cu2(CN)2. , ferricyanide complex [Fe(CN)3-2], zinc cyanide complex Zn(CN) 4-2, and thiocyanate SCN- and other impurities. Among them, cyanide in the free state is the most toxic. Due to the large amount of such poor liquid, only part of the production is recycled and recycled, and the rest is discharged. Therefore, the sewage produced by the zinc replacement method mainly comes from the discharge of the poor liquid.

2. The method of wastewater generated CIP typically low-grade gold plant for the production, recovery of gold and silver, i.e., after the reform new process based on the conventional cyanide leaching, the zinc replacement method, the water addition to its tailings In addition to cyanide, it also contains a lot of tailings and other mineral impurities. This water cannot be returned for leaching and can only be discharged directly as waste water, posing a very serious pollution threat. Further, the solution desorbed from the adsorbed carbon is subjected to electrodeposition or zinc replacement, and the poor liquid contains cyanide, a base, and a residual metal ion or a cyano complex thereof. Except for partial recycling, the lean liquid is discharged, and the recycled lean liquid also has some efflux with the enrichment of oxygen-consuming impurities. Therefore, the large amount of cyanide-containing sewage discharged from the carbon slurry method constitutes a serious pollution threat.

3. The wastewater ion exchange with the clay when present in ores containing gold mud, impurities present in the ore or concentrate flotation agent, or calcine ion when there hematite fine particles, the more complex nature of the ore The exchange resin production is better than the carbon slurry method. After a series of processes by ion exchange, the obtained gold-rich solution is treated by conventional electrowinning and zinc replacement, and the residual cyanide including sludge washing, cyanide removal of Fe, Cu and tree fat is produced. The cyanide-containing wastewater is formed from the waste water containing cyanide and the lean liquid produced by removing zinc from sulfuric acid and the resin-exchanged pulp.

Performance of the main mechanisms: