Principle of gold leaching in cyanide solution
Jin Liu is a chemically stable precious metal. Gold is dissolved in a thin cyanide solution in the presence of oxygen (or oxidant) to form a monovalent gold complex: Flatbed Tow Truck,Rollback Tow Truck,Iveco Wrecker Tow Truck,Recovery Wrecker Truck Hubei Jiangnan Special Automobile Co., Ltd , https://www.cn-firetrucks.com
4Au+8KCN+2H 2 O+O 2 →4KAu(CN) 2 +4KOH
It can also be argued that the following reactions occur when gold dissolves:
2Au+4KCN+O 2 +2H 2 O→2KAu(CN) 2 +2KOH+ H 2 O 2
2Au+4KCN+H 2 O 2 →2KAu(CN) 2 +2KOH
Hydrogen peroxide is an intermediate product formed by the reduction of oxygen in dissolved water.
Regarding the kinetics of gold dissolution in cyanide solution, the diffusion theory states that when gold is immersed in a cyanide solution, the surface of gold dissolves immediately and a saturated solution is formed on the surface of gold, and the saturated solution gradually diffuses into the interior of the solution. Due to the diffusion, the concentration of the saturated solution around the gold is lowered, and the gold is further dissolved to supplement the concentration of the solution around the gold, and the dissolution of gold is gradually formed.
During the dissolution process, the metal loses electrons from its surfaced anode region, while oxygen extracts electrons from the cathode region of the metal surface. The electrochemical dissolution that occurs is shown in the figure below. 
Au→Au + +e -
Au + +2CN - →Au(CN) 2
The cathodic reaction is:
O 2 +2H 2 O+2e - →H 2 O 2 +2OH -
The dissolution rate of gold is related to the concentration of cyanide in the solution and the concentration and diffusion of oxygen. It is related to the surface area of ​​the cathode and anode where the reaction takes place and the concentration of cyanide and oxygen on the surface of the unit gold, and the inside of the solution and the saturated liquid. The thickness of the diffusion is related. When the cyanide concentration is low, the dissolution rate of gold depends only on the oxygen concentration. From a process point of view, the ratio of the dissolved oxygen to cyanide concentration should be controlled. The oxygen content in the free cyanide and the solution in the slurry must be analyzed and controlled at the same time, so that the molar ratio is equal to 6, in order to ensure the ideal leaching effect and The dosage of the medicament is small.