Process flow of gold cyanide recovery

The process flow of gold cyanide recovery typically involves the following steps:

Acidification: The first step involves adding acid to the cyanide solution to lower the pH to a range of 2.5-3.0. This helps to convert the cyanide to hydrogen cyanide gas, which can be safely vented off.

Volatilization: After acidification, the solution is heated to about 90-100°C to drive off the hydrogen cyanide gas. This step is carried out under controlled conditions to avoid the release of toxic gases.

Adsorption: The gold-cyanide complex in the solution is then adsorbed onto activated carbon particles. The carbon is typically added to the solution in a series of tanks called carbon-in-pulp (CIP) or carbon-in-leach (CIL) tanks. The carbon is kept in suspension by agitating the mixture to ensure maximum contact between the gold-cyanide complex and the carbon.

Stripping: Once the gold-cyanide complex has been adsorbed onto the carbon, the loaded carbon is removed from the CIP/CIL tanks and transferred to a stripping vessel. In this vessel, the gold is stripped off the carbon by desorption using a hot caustic solution (usually sodium hydroxide). This produces a solution containing the gold and the cyanide.

Recovery: The gold-cyanide solution is then treated to recover the gold. This can be done using a variety of methods, such as electrowinning, precipitation with zinc dust or aluminum powder, or smelting. The method used depends on the specific circumstances of the operation and the desired purity of the gold.

Recycle: The stripped carbon is then recycled back to the CIP/CIL tanks to be used again in the adsorption process. The remaining cyanide solution is also recycled back to the leaching circuit for further use.

Overall, the gold cyanide recovery process is an efficient and effective way to recover gold from low-grade ores and tailings. It is widely used in the mining industry and has proven to be a reliable method for recovering gold. However, it is important to manage the cyanide solution carefully to prevent environmental damage and ensure worker safety.