Basic steps of carbon-in-pulp method (CIP)
Raw material preparation:
Grind the gold-containing ore to an appropriate particle size to increase the gold leaching rate. It is usually necessary to grind until 80% passes through a 200 mesh sieve.
Cyanide leaching:
Mix the ground ore with cyanide solution (usually sodium cyanide solution) and react under suitable conditions (such as temperature, pH value and time). Gold forms a soluble gold-cyanide complex with cyanide:
[
\text{Au} + 2 \text{NaCN} + \text{H}_2\text{O} \rightarrow \text{Na}_2\text{[Au(CN)}_2] + \text{NaOH}
]
Carbon slurry mixing:
Activated carbon is added to the cyanide leachate to form a carbon slurry with the gold-cyanide compound. The activated carbon adsorbs gold ions during this process.
Separation and washing:
The carbon slurry is separated from the leachate by sedimentation or filtration, and multiple washings are usually performed to ensure maximum gold recovery.
Elution:
The gold-adsorbed activated carbon is eluted, usually using a high-concentration sodium cyanide solution or hot water solution to release the adsorbed gold.
The eluted gold solution is transferred to the subsequent refining process.
Gold refining:
The gold is extracted and precipitated from the eluate by electrolysis, smelting or other chemical methods, and finally a pure gold nugget is obtained.
Advantages
High recovery rate: The carbon-in-slurry method has a high gold recovery rate, usually reaching more than 95%.
Strong adaptability: It can process many different types of gold-bearing ores, including low-grade ores.
High degree of automation: It is suitable for application in large-scale gold processing plants, and can be automated to improve production efficiency.
Precautions
Use of cyanide: Cyanide is required in the carbon-in-slurry method, which poses a risk to the environment and the safety of workers. Therefore, safe operating procedures must be strictly followed and wastewater treatment must be done well.
Selection of activated carbon: High-quality activated carbon has a high specific surface area and good pore structure, which can improve the adsorption effect of gold. It is crucial to choose the right activated carbon.
Control of operating conditions: The operating conditions such as pH, temperature and cyanide concentration of the leaching solution should be strictly controlled to ensure the efficiency of leaching and adsorption.
Summary
Activated carbon-in-slurry method is an important method in gold recovery. It effectively improves the recovery efficiency of gold by utilizing the excellent adsorption properties of activated carbon. With the development of technology, the carbon-in-slurry method has been continuously improved and optimized, becoming an indispensable part of modern gold mining processing.
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