Abstract. Cyanide extraction of gold through milling of high grade ores and heap leaching of low grade ores requires cycling of millions of liters of alkaline water containing high concentrations of potentially toxic sodium cyanide , free cyanide, and metal cyanide complexes. Some milling operations result in tailings ponds of 150 ha and larger.
At present, most cyanidation gold extraction plants use cyanide as a gold extraction reagent. As is well known, cyanide is a kind of highly toxic hazardous chemical, so any misoperation in transportation, storage, use, and other links will cause the events of serious environmental pollution, malignant poisoning, etc.
Sodium cyanide is the most commonly used leaching chemical in gold extraction process. According to theoretical calculation, leaching 1 gram of gold only requires 0.5 grams of sodium cyanide. However, in most gold cyanidation plants, the consumption of cyanide is high, which is 50 100 times higher than the theoretical calculation.
Because cyanide leaching is very efficient, it allows profitable mining of much lower ore grades. Mining lower grade ore requires the extraction and processing of much more ore to get the same amount of gold. Partially due to cyanide, modern mines are. produce huge quantities of waste.
By suspending the crushed ore in a cyanide solution, a separation of up to 96 percent pure gold was achieved. The process was first used on the Rand in 1890 and, despite operational imperfections, led to a boom of investment as larger gold mines were opened up.