Coconut shell gold-grade activated carbon is made from high-quality coconut shells through a special process. It features a large specific surface area and strong adsorption capacity, making it widely used in gold refining. In the heap leaching process of gold mines, coconut shell gold-grade activated carbon can efficiently adsorb gold ions in the solution, improving the gold recovery rate. With the soaring price of gold, market demand is also constantly growing. However, how to choose the right activated carbon for gold recovery?

The principle of gold recovery is the adsorption of gold cyanide complex ions ([Au(CN)₂]⁻) in cyanide solutions by activated carbon. Therefore, the selection of activated carbon should focus on "improving gold adsorption efficiency" and "reducing desorption costs." Key indicators are as follows:

1. Iodine adsorption value ≥1000 mg/g, preferably 1100-1300 mg/g. A higher iodine value indicates a larger specific surface area, more developed micropores (2-5 nm), more adsorption sites for gold cyanide complex ions, and a higher adsorption capacity.

2. Methylene blue adsorption value ≥180 mg/g. This reflects the number of mesopores, which can serve as transport channels for gold cyanide complex ions, increasing the adsorption rate.

3. Specific surface area ≥1000 m²/g, micropore ratio ≥70%. Micropores are the core area for gold adsorption; a higher ratio indicates stronger selective adsorption of gold and reduced adsorption of impurities (copper, iron, etc.).

4. Strength (wear resistance) ≥95% (granular carbon) In gold recovery processes, activated carbon needs to withstand friction and impact in stirred tanks (CIP/CIL) or heap leaching. Low strength leads to easy pulverization, causing gold loss and equipment blockage.

5. Particle size: 4-16 mesh (1.18-3.35mm), preferably 6-12 mesh. A moderate particle size is desirable: too fine a particle size leads to easy loss and high resistance; too coarse a particle size results in a small specific surface area and slow adsorption rate.

6. Pore structure: Primarily micropores (2-5nm), supplemented by mesopores (5-50nm). Micropores are responsible for gold adsorption, while mesopores are responsible for transport. A reasonable ratio of these two types balances adsorption capacity and adsorption rate.

7. Ash content: ≤5%. Excessive ash content introduces impurities, increasing the difficulty of waste liquid treatment after desorption and reducing gold purity.

8. pH value: Neutral to weakly alkaline (7-9). Avoid acidic activated carbon damaging the stability of the cyanide solution and affecting the formation of gold cyanide complex ions.