Application of coconut shell activated carbon in gold refining

Coconut shell activated carbon is a porous material made from coconut shells through a series of physical and chemical processes. It is widely used in water treatment, air purification, and precious metal refining.

 

Coconut shell activated carbon is a porous material made from coconut shells through a series of physical and chemical processes. It is widely used in water treatment, air purification, and precious metal refining.

Preparation process of coconut shell activated carbon  

The first step in preparing coconut shell activated carbon is to select high-quality coconut shells. Coconut shells should be fresh and free of mold as much as possible to ensure the quality of the final product.

Clean the coconut shells and remove the dirt and impurities on the surface. After cleaning, dry the coconut shells naturally in the sun or put them in a drying oven to ensure that there is as little moisture as possible in the coconut shells.

The dried coconut shells need to be carbonized. Carbonization refers to heating the coconut shells to a high temperature (usually 500-700℃) in an oxygen-deficient or oxygen-free environment to decompose them into carbonaceous substances. This process is usually carried out in a carbonization furnace, and the time generally ranges from several hours to one day. The carbonized coconut shells are black and have a preliminary porous structure.  

The carbonized coconut shells need to be further activated to increase their specific surface area and porosity. There are two main methods of activation: physical activation and chemical activation:

Physical activation is to react the carbonized coconut shell with water vapor or carbon dioxide at high temperature (800-1000℃). This process can further open the pores of the coconut shell and increase the specific surface area.

Chemical activation is to mix the carbonized coconut shell with an activator (such as zinc chloride, phosphoric acid, potassium hydroxide, etc.) and heat it at a lower temperature (400-600℃). The activator can promote the formation of pores in the coconut shell and enhance its adsorption capacity.

The coconut shell after chemical activation needs to be washed to remove the residual activator and then dried.   The activated coconut shell activated carbon needs to be crushed and sieved to obtain a product with uniform particle size. Coconut shell activated carbon with different particle size ranges can be prepared according to application requirements.  

Finally, the prepared coconut shell activated carbon is packaged and stored in a dry and ventilated environment to avoid moisture and pollution.

Application of coconut shell activated carbon in gold refining

Gold refining is a complex process that requires the use of a variety of chemical agents and physical methods. Coconut shell activated carbon has important applications in gold extraction due to its excellent adsorption properties, especially in the carbon-in-pulp (CIP) and carbon-in-leach (CIL) processes.  

1. CIP process

The CIP process refers to the process of adsorbing the gold in the leachate through coconut shell activated carbon after the gold ore is crushed and leached. The specific steps are as follows:  

Leaching

The crushed and ground gold ore is mixed with a sodium cyanide solution to dissolve the gold from the ore to form gold cyanide.  

Adsorption

The solution containing gold cyanide is mixed with coconut shell activated carbon, and the gold cyanide will be adsorbed by the activated carbon. Since coconut shell activated carbon has a huge specific surface area and a developed pore structure, it can effectively adsorb gold in the solution.  

Washing

The activated carbon adsorbed with gold is separated from the leachate, and the impurities on the activated carbon are washed clean with clean water or an acidic solution to reduce the impact of impurities on the subsequent gold extraction process.  

Desorption and electrolysis

The activated carbon adsorbed with gold is mixed with a desorbent (such as sodium cyanide solution or caustic soda solution) and the gold is desorbed from the activated carbon by heating or pressurizing. The desorbed gold solution is reduced by electrolysis or other methods to finally obtain pure metallic gold.

Activated carbon regeneration

The desorbed coconut shell activated carbon can be regenerated by heating, chemical treatment and other methods to restore its adsorption performance and then recycled.  

2. CIL process

The CIL process is similar to the CIP process, except that the adsorption and leaching processes are carried out simultaneously. In the CIL process, gold ore is leached in a cyanide solution, and coconut shell activated carbon is directly added to the leaching tank to adsorb the dissolved gold. Since adsorption and leaching are carried out simultaneously, the CIL process is more efficient when processing low-grade ores.  

Leaching and adsorption

The gold ore is mixed with a sodium cyanide solution and coconut shell activated carbon, and the dissolved gold cyanide is immediately adsorbed by the coconut shell activated carbon.  

Washing and desorption

Similar to the CIP process, the activated carbon adsorbed with gold is washed and desorbed to obtain a gold-containing solution.

Electrolysis and activated carbon regeneration

The desorbed gold-containing solution is reduced to pure gold by electrolysis and other methods, and the coconut shell activated carbon is regenerated for recycling.   III. Advantages of coconut shell activated carbon in gold refining Coconut shell activated carbon has the following advantages in gold refining:  

1. High adsorption capacity: Coconut shell activated carbon has a developed pore structure and a high specific surface area, which can effectively adsorb gold cyanide in the solution and improve the recovery rate of gold.  

2. Excellent mechanical strength: Coconut shell activated carbon has high mechanical strength and can withstand the mechanical stress generated during adsorption, washing, desorption and other processes, reducing the wear and loss of activated carbon.  

3. Good regeneration performance: Coconut shell activated carbon can be regenerated by physical or chemical methods to restore its adsorption performance, has a long service life, and reduces the cost of gold refining.  

4. Green and environmentally friendly: Coconut shell activated carbon raw materials are widely available and renewable, the production process is relatively environmentally friendly, has little environmental pollution, and is conducive to sustainable development.   As a highly efficient adsorption material, coconut shell activated carbon plays an important role in gold refining. Its preparation process includes raw material preparation, cleaning and drying, carbonization, activation, crushing and screening. The prepared coconut shell activated carbon has high adsorption capacity, excellent mechanical strength and good regeneration performance. In CIP and CIL processes, coconut shell activated carbon can effectively improve the recovery rate of gold and reduce the refining cost, and has broad application prospects.