As gold resources gradually deplete and mining becomes more challenging, the extraction of gold from ores has become increasingly challenging. Carbon-in-leach (CIL) method, as an effective gold extraction process, has been widely used in the field of gold metallurgy. This article will elaborate on the process flow of CIL gold extraction, discussing its principles, steps, and influencing factors during the gold extraction process.
Carbon-in-leach (CIL) is a method that utilizes activated carbon to adsorb gold. The basic principle involves immersing gold-bearing ores in a cyanide solution, where gold is oxidized into [Au(CN)2]- ions, forming soluble gold cyanide dissolved in the solution. Then, utilizing the strong adsorption capacity of activated carbon, the cyanide gold ions in the solution are adsorbed, achieving gold extraction.
1. Crushing and Grinding:
Firstly, the raw ore undergoes crushing and grinding to control particle size within a suitable range. Crushing aims to break the raw ore into smaller particles, increasing the exposed surface area of gold; grinding further refines ore particles, preparing them for subsequent leaching.
2. Leaching:
The crushed and ground ore is sent to the leaching tank for leaching treatment in an alkaline cyanide solution. Alkaline conditions facilitate the dissolution of cyanide and oxidation of gold, allowing gold to dissolve in the solution as [Au(CN)2]- ions.
3. Adsorption:
The leached solution containing cyanide gold ions is then subjected to adsorption by adding activated carbon. Activated carbon, with its large surface area and strong adsorption, rapidly adsorbs cyanide gold ions in the solution, forming gold-activated carbon complexes.
4. Washing:
The adsorbed activated carbon is separated from other impurities in the solution. Through the washing process, impurities on the surface of activated carbon are washed away, ensuring the purity and extraction rate of gold.
5. Desorption:
The activated carbon carrying gold ion complexes from washing enters the desorption tank, where, under appropriate conditions, gold is desorbed from the activated carbon, forming a gold-containing solution.
6. Refinement:
Finally, the gold-containing solution after desorption undergoes refinement treatment. Typically, electrolysis or zinc powder displacement is employed to precipitate gold from the solution, obtaining pure gold metal.
1.Cyanide Concentration:
Cyanide concentration is a crucial factor affecting the gold extraction efficiency of CIL. Appropriate cyanide concentration promotes gold dissolution and adsorption, but excessively high concentrations may lead to excessive adsorption by activated carbon and wastage.
2.Oxygen Content:
Oxygen plays a role in oxidizing gold in the CIL process, so an adequate oxygen content in the solution facilitates gold dissolution. Oxygen deficiency or insufficient oxygen content reduces the dissolution rate of gold, affecting the extraction efficiency.
3.Agitation Speed:
Proper agitation speed maintains the uniformity of the solution in the leaching tank, facilitating gold dissolution and activated carbon adsorption. Too slow agitation leads to reduced reaction rates, while excessively fast agitation may cause foam overflow and increased energy consumption.
4. Temperature:
Temperature affects both the dissolution rate of gold and the adsorption efficiency of activated carbon. Generally, higher temperatures accelerate gold dissolution and activated carbon adsorption rates, but excessively high temperatures may lead to solution evaporation and uncontrolled reactions.
Carbon-in-leach (CIL) is an efficient gold extraction process, involving crushing, leaching, adsorption, washing, desorption, and refinement. In practical applications, optimizing process parameters based on ore properties, process conditions, and economic considerations is essential to improve gold extraction rate and purity, achieving economic benefits and environmentally friendly gold extraction processes.
