Activated Carbon For Gold and Silver Industries

Initially wood charcoal with a surface area around 200 m2 /gram was used to extract gold and silver from the solution. As the development of the activated carbon having a surface area of  1,000 m2 / gram is used for that, of course, also with the increasing efficiency of the extraction. It encourages the production of activated carbon throughout the world. Coconut shell is the favorite material for active charcoal production today, and palm kernel shell is likely to be the next priority.

Activated carbon has a large surface area because of the large number of pores from its surface. The pores are intentionally made to improve the efficiency of adsorption. The more pores are formed the more activated carbon surface area. Based on the size of these pores are divided into macropore, mesopore and micropore. Macropore is the largest pore size located on the outer side or surface of activated carbon and as the entrance material will be adsorbed then through mesopore medium to last to the micropore. Micropore is the last terminal of material that is adsorbed. Micropore pore size ranges from 10 angstrom, mesopore 100-1000 angstrom and macropore larger 1000 angstrom (1 angstrom = 1e-10 meter). The raw material or activated carbon material, the choice of activation process used and the operating conditions that will determine the surface area of activated carbon consisting of macropore, mesopore and micropore. Hardness and density of materials are also often important considerations given the use of activated carbon itself, for example a number of extractions are carried out by stirring and there are also column operations.

The specific use of activated carbon for the application of certain materials or industries usually also requires certain specifications. Activated carbon used in fluid fluids will be optimal when specially designed under these conditions, as well as those used in gas fluids. The size of the target material and its extraction methods will determine the technical specifications of the activated carbon. Likewise in gold and silver, which extraction with stirring and column operations. So the raw material of coconut shell is generally still the main choice because it has a high level of hardness and density so that abrasion resistance. And so too the palm kernel shells can also be used given the high level of its hardness. So the activated carbon used must meet the criteria of quite hard, active enough and appropriate particle size. In the gold extraction activated carbon gold produced by the activation of physics (steam activation) is used. Rotary kiln is an activation equipment with raw materials such as coconut shell, while fluidized bed appliance and multi hearth kiln are commonly used for activated carbon from coal.

Activated carbon basically can be made from various materials that contain carbon (carbonaceous material) such as coal, coconut shell, palm kernel shell, wood, bamboo, heavy oil and even bone. Each material, type of activation and operating conditions of the process determines the quality or characteristics of activated carbon. Activated carbon from coconut shell has many micropore, while activated carbon from wood is dominated mesopore and macropore (micropore only has small portion) because wooden structure also more open. For activated carbon from coal micropore distribution, mesopore and macropore are almost evenly distributed. Based on the above characteristics, activated carbon coconut shell is widely used to adsorb small molecules of gas and liquid. Its uses such as gas masks, solvent recovery and gold recovery. While activated carbon from wood for the application of large molecules such as adsorbing organic dyes in the industry. While activated carbon from coal for the adsorption of organic molecules with varying sizes and their use is generally for drinking (potable) water treatment and wastewater treatment.

After gold or silver is adsorbed into the pores of activated carbon, the next step is to pick or remove (delution) from activated carbon. There are 2 technologies commonly used for this stage namely AARL elution process and Zadra elution process. The difference between electrowinning is an integral part of the Zadra circuit but a separate part of the AARL circuit. Zadra dominates in North America while AARL dominates in Southern Hemisphere, where the technology was originally developed. Which is the best? Operators factor and device performance more decisive. The 10 largest gold producers today include China, Australia, the United States, Russia, South Africa, Peru, Canada, Ghana, Indonesia and Uzbekistan.