How to extract gold from limonite ore ?

Extracting gold from limonite ore involves several steps, as limonite is a type of iron ore that contains gold particles. The process is complex and requires careful handling and the use of various chemicals and equipment. Here is a detailed explanation of the steps involved:

1. Crushing and Grinding

The first step in extracting gold from limonite ore is to crush and grind the ore into a fine powder. This increases the surface area of the ore, making it easier to extract the gold. The equipment used for this process includes jaw crushers, ball mills, and rod mills.

2. Concentration

Once the ore is ground into a fine powder, the next step is to concentrate the gold particles. This can be done using several methods:

• Gravity Separation: This method uses the difference in density between gold and the surrounding minerals to separate the gold particles. Equipment such as jigs, shaking tables, and spiral concentrators are commonly used.
• Flotation: In this method, chemicals are added to the ore slurry to make the gold particles hydrophobic (water-repellent). Air bubbles are then introduced, which attach to the gold particles and float them to the surface, where they can be collected.

3. Roasting

Limonite ore often contains sulfides, which can interfere with the extraction process. Roasting involves heating the ore to high temperatures in the presence of oxygen to convert the sulfides into oxides. This makes it easier to extract the gold.

4. Cyanidation

Cyanidation is a common method for extracting gold from ore. In this process, the concentrated ore is mixed with a cyanide solution, which dissolves the gold. The gold-cyanide complex is then separated from the slurry using activated carbon or zinc precipitation.

5. Recovery

The final step is to recover the gold from the cyanide solution. This can be done using several methods:

• Activated Carbon: The gold-cyanide complex is adsorbed onto activated carbon. The carbon is then stripped of the gold using a hot caustic solution, and the gold is recovered by electrolysis or precipitation.
• Zinc Precipitation: The gold-cyanide complex is precipitated out of the solution using zinc dust. The precipitate is then filtered, and the gold is recovered by smelting.

6. Refining

The recovered gold is often impure and needs to be refined. This can be done using several methods:

• Electrolytic Refining: The impure gold is cast into anodes and placed in an electrolytic cell. A current is passed through the cell, causing the gold to dissolve and be deposited onto a cathode as pure gold.
• Chemical Refining: The impure gold is dissolved in aqua regia (a mixture of hydrochloric and nitric acids), and the gold is precipitated out of the solution using a reducing agent such as sodium metabisulfite.

Safety and Environmental Considerations

Extracting gold from limonite ore involves the use of hazardous chemicals and high temperatures, so it is important to follow safety protocols and environmental regulations. Proper disposal of waste materials and the use of protective equipment are essential to minimize the impact on the environment and ensure the safety of workers.

In summary, extracting gold from limonite ore is a multi-step process that involves crushing and grinding the ore, concentrating the gold particles, roasting to remove sulfides, cyanidation to dissolve the gold, and recovering and refining the gold. Each step requires specialized equipment and careful handling to ensure the efficient and safe extraction of gold.