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The key to improving the gold recovery rate of percolation cyanidation is to enhance the permeability of the heap and make the leachate fully contact and react with the free gold in the ore. In addition, increasing the oxygen content during the gold leaching process is also an important condition for increasing the leaching rate. In order to increase the recovery rate of gold when using percolation cyanidation method, the following measures can usually be taken.
The core problem of the percolation cyanidation is how to ensure that the gold extraction solution and the valuable components in the ore can be fully contacted and effectively reacted. This requirement is more difficult for ores containing more ore and clay.
During the granulation process, the powder ore in the clay and ore adheres to the coarse particles to form a fine-grained coating. The ore particles formed in this way have sufficient wet strength and are less likely to break when solidified and then wetted.
Granulation can produce porous and permeable raw materials, thereby overcoming the main problems caused by ore particle size segregation during the pile-up, such as migration of fine particles and channeling of the solution during leaching, thereby increasing the gold recovery rate.
The basic principle of increasing the gold recovery rate of percolation cyanidation with a wetting agent is receiving great attention.
In theory, the addition of a special surfactant, a wetting agent, to the leachate reduces the surface tension and allows the ore and leachate to be more completely contacted, thereby increasing permeability and gold recovery rate.
Increasing the permeability can shorten the time required for leaching, reduce the cost of cyanide and pumping, reduce the dry zone in the leaching tank, enhance the penetration to individual ore particles, and finally achieve the purpose of improving the metal recovery rate.
A wetting agent is a material that enhances leaching. It not only increases the speed of leaching and final gold recovery rate, but also ensures that it does not adversely affect subsequent gold adsorption and desorption.
After the ore has been ground, it must be well classified, and then cyanidated separately according to the particle size to increase the percolation speed and gold recovery rate.
1) Using dry charging to minimize the moisture in the ore, so that the air fills the gap between the ore particles to increase the dissolution rate and gold recovery rate of the gold.
2) Before the leaching, prefill the cyanide solution with air to increase the oxygen content in the solution, thereby increasing the dissolution rate and gold recovery rate of the gold.
3) Blow the compressed air into the ore layer to oxidize various reducing agents, and at the same time, oxidize the ferrous compound into a ferric compound, which can also accelerate the dissolution of gold and improve the gold recovery rate.
Prior to leaching, the ore may be washed with water, alkali or acid to reduce cyanide consumption and increase gold gold recovery.
For example, the free acid and soluble salts can be washed away with water; the acid can be neutralized with base; the copper oxides and carbonates can be eliminated with dilute sulfuric acid.
The above are several measures that can improve the gold recovery rate of the diafiltration cyanidation and accelerate the dissolution of gold to obtain higher beneficiation index.