How to Select Good Gold Extraction Activated Carbon?

As we all know, gold is a very expensive metal, and the gold extraction process is naturally a very important matter. With the development of gold production and the progress of science and technology, the gold extraction process has been improved and perfected. Today's gold mines mainly use carbon-in-pulp (CIP) circuits, carbon-in-leach (CIL) circuits, and carbon-column (CIC) processes to extract gold.

The essence of the CIP/CIL/CIC process is that gold is leached from the fine ore in the slurry and adsorbed onto larger carbon particles, which are recovered from the carbon particles after the carbon has been simply screened out of the slurry. This article is about how to choose activated carbon for gold refining, as well as the external factors that affect gold adsorption, and finally helps you to choose the right activated carbon supplier.

الكربون المنشط قذيفة جوز الهند plays a vital role in gold refining and is used to adsorb gold with several advantages.
- Fast adsorption rate.
- High gold-carrying capacity.
- High abrasion resistance.

At the heart of any CIP, CIL or CIC gold refining process is activated carbon, because it is what adsorbs gold, so the performance of the activated carbon will also have an impact on gold recovery. When selecting an activated carbon for gold recovery, the following 9 characteristics are very important. The performance is directly related to: the production rate of gold refining, and the amount of gold wasted and lost.

1. Quality of raw material
The thicker the coconut shell, the better. Selecting thicker coconut shells with low volatility, low moisture, and high fixed carbon content will produce stronger and thicker activated carbon with lower ash content and better gold adsorption capacity and efficiency.

2. Particle size
The smaller the particle size of activated carbon, the faster will adsorb gold. However, the smaller the particle size, the more difficult it is to sieve the carbon from the slurry, which can lead to the loss of activated carbon and gold. If the carbon particles are too large, the rate of gold adsorption will be reduced. The particle size of activated carbon used in CIL and CIP plants is therefore a balance between sieving efficiency and gold adsorption rate.
Commonly activated carbon sizes for gold recovery range from 6-12mesh (1.68 mm ~ 3.36 mm), 8-16mesh (1.19 mm ~ 2.38 mm), and 6-16mesh (1.19 mm ~ 3.36 mm).

3. Absorptive Capacity (known as K-value)
Often called loading capacity, the adsorptive capacity of activated carbon refers to how much the activated carbon can adsorb. Adsorptive capacity is linked to the physical and chemical properties of the activated carbon. The higher the K value, the higher the gold adsorption capacity.

4. Absorption rate (known as R-value)
The rate of adsorption is also largely affected by both the physical and chemical properties of the activated carbon. The higher the R-value, the faster the rate of gold adsorption.

5. Mechanical strength or abrasion resistance/hardness
The hardness of activated carbon used for gold refining is as important as its gold adsorption properties. This is because activated carbon is subjected to intense friction and tumbling during the CIC, CIP/CIL processes. If the strength of the activated carbon is too low, it will wear down to fine particles, resulting in not only the loss of activated carbon but also the loss of gold, which will ultimately reduce the effectiveness of gold adsorption significantly.

So one good activated carbon for gold recovery is a compromise between hardness and gold adsorption performance. Coconut shell based activated carbon has been found to be the most suitable carbon for this application at present.

6. Iodine value
The higher the iodine value of the activated carbon, the more developed its pores are and the higher the gold carrying capacity and adsorption rate of the activated carbon under certain working conditions.

7. CTC value
The higher the CTC value of activated carbon, the more developed its pores are, and the higher the gold carrying capacity and adsorption rate of activated carbon will be under a certain working environment.

8. Appearance
More uniform size and cleaner appearance of the activated carbon will also increase the rate of gold adsorption. In order to minimize the production of carbon dust during wear and tear and regeneration, the strictest particle control is applied. We source evenly sized activated carbon, which does not need to be pre-ground when it comes into the plant and can be used directly after washing with water.

9. Production technology
There are currently two main activation processes in activated carbon plants: the Sleiphus and the rotary furnace. In order to obtain a higher hardness index of activated carbon, the Sleiphus process controls the iodine adsorption value at around 900-950 mg/g. This increases the hardness index but loses the gold adsorption capacity and the adsorption speed of the activated carbon. However, the rotary furnace can produce activated carbon with a higher iodine value and with a controlled strength of 98% or more.

1. Pulp density:
In order to maximize gold adsorption, the carbon must be evenly distributed throughout the ore pulp. This can be achieved by ensuring effective mixing and controlling the ore pulp density. The density of wet activated carbon is between 1.3 and 1.5, so the ore pulp must be in this region in order for the carbon to be evenly suspended in the ore pulp. If the density of the ore pulp is too low. then the carbon will sink to the bottom of the contactor, if the density of the ore pulp is too high, the carbon will float. In both cases there will be insufficient mixing, resulting in a lower recovery of gold.

2. Cyanide concentration
Cyanide concentration is important for gold leaching and generally needs to be maintained in excess to ensure maximum gold leaching.

3. The pH of the ore pulp
A high pH stabilizes the Au(CN)2- ions in the solution, thus reducing the chance of gold adsorption of calcium cyanide ions to gold. the lower the pH, the greater the chance of gold adsorption. However, the formation of HCN is dangerous at low pH conditions, so the optimum operating pH for the CIP/CIL plant is between 8 and 11.

4. Temperature during operation
The adsorption of calcium cyanide gold ions by activated carbon results in an exothermic reaction, i.e. heat is generated as the gold is adsorbed. At lower temperatures, carbon is favorable for gold adsorption; in general, gold adsorption works better in the cold winter months than in the hot summer months. But to remove (elute) the gold from the carbon, the temperature must be very high to have good results.

5. Gold Tenor and Inquiry Time
The higher the gold grade, the higher the amount of gold adsorbed by the activated carbon. As there is a rate control on the adsorption of gold by carbon, the inquiry time will also affect the amount of gold adsorbed. For cost reasons, inquiry times are kept between 10 and 60 minutes per contact for the CIP and CIL plants, and normal leaching times (up to 4 hours per tank) for the CIL plant.

When producing gold carbon, we have strict requirements on raw materials, The thickness of the coconut shell should reach 5-7mm, and it has to be screened and washed three times before it can be put into use.

So the carbon we produce is clean and the particles are full and uniform, it has strong adsorption capacity, high hardness, and high wear resistance, so it shows outstanding performance on gold recovery.

Our coconut shell activated carbon has an iodine value of up to 1900mg/g, and we exceed 90% of activated carbon manufacturers in the Chinese market.

Huamei offers a full range of carbon products to serve the gold recovery industry and is used by gold plants all over the world. These include standard activated carbon grades (HMGOLD-5500, HMGOLD-6000, and HMGOLD-7000), and higher capacity activated carbon grades (HMGOLD-Plus).