Activated carbon for gold extraction: an efficient metal recycling technology

1. Introduction

As a precious metal, gold has attracted much attention since ancient times due to its unique physical properties and wide application value. However, the process of mining and refining gold is often accompanied by high costs and environmental pressures. In recent years, with the advancement of science and technology, activated carbon gold extraction technology has gradually emerged and become an efficient and environmentally friendly gold recovery method.

2. The principle of refining gold with activated carbon

The principle of activated carbon refining gold is mainly based on the strong adsorption capacity of activated carbon and the chemical properties of gold. Activated carbon is a porous carbon material with a large specific surface area and adsorption capacity. During the refining process, gold usually exists in solution in the form of ions or complexes. When these solutions pass through the activated carbon layer, gold ions or complexes are adsorbed by the activated carbon and fixed on the surface. Subsequently, through a series of chemical reactions and physical separation steps, the gold can be desorbed from the activated carbon and recovered.

3.Activated carbon classification

Activated carbon can be divided into various types based on characteristics such as preparation raw materials, appearance shape and pore structure.  

Classification by raw material source:

Coal-based charcoal: Refined from high-quality anthracite as raw material, it has the characteristics of high strength, fast adsorption speed, high adsorption capacity, large specific surface area, and developed pore structure.

Nutshell charcoal: Mainly made from fruit shells and sawdust as raw materials, it is processed through carbonization, activation and refining. For example, coconut shell activated carbon is made from high-quality coconut shells.

Wood charcoal: Made from high-quality wood as raw material, it is refined through high-temperature carbonization, activation and various processes. Wooden activated carbon has the characteristics of large specific surface area, high activity, developed micropores, and strong decolorization ability.

Classification by appearance shape：

Powdered activated carbon: fine particle size, usually in powder form, often used for some special needs.

Granular activated carbon: Larger particle size, regular shape, easy to operate and recycle.

Pillar charcoal: Made from high-quality sawdust, charcoal, etc. as raw materials, it is made through crushing, mixing, extrusion, molding, drying, carbonization, and activation. Spherical activated carbon and honeycomb activated carbon: have specific shapes and structures and are suitable for specific metallurgical processes.

Classification by pore structure:

Microporous activated carbon: It has a large number of microporous structures and can adsorb small molecular substances.

Mesoporous activated carbon: has a larger pore size and is suitable for adsorbing macromolecular substances.   In the metallurgical industry, different types of activated carbon have different adsorption properties and application ranges. Therefore, when selecting metallurgical activated carbon, comprehensive considerations need to be made based on specific process requirements, material properties and processing conditions. Under normal circumstances, most of the activated carbon used to extract gold is 6-12 mesh in size and the raw material is coconut shell activated carbon, which has better extraction effect.

4. Steps of refining gold with activated carbon

Pretreatment： The ore or waste containing gold is subjected to pretreatment operations such as crushing and grinding to better contact with the solution.

Dissolution： Pretreated ore or waste is mixed with specific chemical reagents to dissolve the gold in the solution. This step usually requires a certain temperature and pressure.

Adsorption： The solution containing dissolved gold is adsorbed through the activated carbon layer. In this process, the adsorption capacity of activated carbon will be fully exerted to fix gold ions or complexes on the surface.

Desorption：Desorb gold from activated carbon by changing solution conditions (such as pH value, temperature, etc.) or using specific chemical reagents.

Recovery： The desorbed gold is subjected to further physical separation and purification operations to finally obtain high-purity gold products.  

5. Advantages of activated carbon for gold extraction High efficiency： Activated carbon has a large specific surface area and adsorption capacity, and can efficiently adsorb gold ions or complexes in the solution.

Environmental protection：Compared with traditional refining methods, activated carbon produces less waste during gold refining and causes less environmental pollution.

Flexibility：Activated carbon gold extraction technology is suitable for various types of gold ores and waste materials, and has strong adaptability.

Energy saving：During the refining process, activated carbon can be reused through regeneration, reducing energy consumption and costs.  

6. Conclusion

As an efficient and environmentally friendly metal recycling method, activated carbon gold extraction technology has broad application prospects in the field of gold mining and recycling. With the continuous advancement of science and technology and the improvement of environmental awareness, it is believed that this technology will be more widely used and promoted in the future.