How to separate gold from ore
Shibang China
Shanghai Shibang Machinery Co., Ltd. is a high-technology minerals processing company, Professional manufacturer of mini
Separating gold from ore involves several processes, which can vary depending on the type of ore and the nature of the gold. Here are the main methods used:
1. Crushing and Grinding
The ore is crushed and ground to liberate the gold particles.
2. Gravity Separation
Gravity separation techniques take advantage of the difference in density between gold and the surrounding materials.
- Panning: Using a pan, gold miners separate gold from other materials by swirling water.
- Sluicing: A sluice box uses flowing water to separate gold from gravel.
- Centrifugation: A centrifuge separates fine particles of gold from other materials.
3. Flotation
Flotation involves mixing the powdered ore with water and chemicals to create a frothy mixture where the gold can be separated from other minerals. The gold attaches to bubbles and rises to the surface, where it can be collected.
4. Cyanidation
Cyanidation is a chemical process for extracting gold from low-grade ore by converting the gold to a water-soluble coordination complex.
- Heap Leaching: Ore is piled in large heaps, and a cyanide solution is sprayed over the heap, dissolving the gold.
- Vat Leaching: Ore is placed in large tanks, and a cyanide solution is added to dissolve the gold.
5. Amalgamation
This method involves mixing the crushed ore with mercury, which forms an amalgam with gold. The amalgam is then heated to evaporate the mercury, leaving behind pure gold.
6. Electrowinning
In this process, the gold is removed from the cyanide solution using electrical currents. This technique is often used in conjunction with cyanidation.
Detailed Steps for Each Method
Gravity Separation (Example: Panning)
1. Crush and Grind: Reduce the size of the ore to liberate gold particles.
2. Pan the Ore: Place the crushed ore in a pan and add water. Swirl the mixture so that the lighter material is washed over the side, leaving the denser gold particles behind.
Cyanidation (Example: Heap Leaching)
1. Crush the Ore: The ore is crushed to a fine powder.
2. Heap Formation: The powdered ore is heaped on a large surface.
3. Cyanide Solution Application: A cyanide solution is sprayed over the heap. The solution percolates through the heap and dissolves the gold.
4. Collection: The gold-laden solution is collected from the base of the heap.
5. Recovery: The gold is then extracted from the solution, often by zinc precipitation or activated carbon adsorption.
Flotation
1. Crushing and Grinding: Crush and grind the ore to a fine powder.
2. Add Reagents: Mix the powdered ore with water and reagents to create a slurry.
3. Air Injection: Inject air into the slurry, creating frothy bubbles.
4. Gold Collection: The gold attaches to the bubbles and floats to the surface, where it is skimmed off.
Safety and Environmental Concerns
- Mercury: Amalgamation with mercury is hazardous to health and the environment.
- Cyanide: Cyanidation poses significant environmental risks if not managed properly. It requires stringent controls to prevent cyanide spills and contamination.
Summary
The choice of method depends on the nature of the ore, the amount of gold present, and environmental and safety considerations. Gravity separation is simple and safe but may not be effective for fine gold. Flotation and cyanidation are more efficient for processing large volumes of ore but require more sophisticated equipment and safety measures.
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