High temperature chlorination

In high temperature pressure vessel, under conditions of the presence of ferric chloride, gold chloride generates chlorine gas using iron chloride complexes of gold (AuFeCl ₆₎ gas method called high temperature chlorination of gold.
In order to fully expose the gold particles, the gold-containing sulfide ore is ground and calcined, and the pyrite structure is destroyed at a temperature of 500 ° C. The calcine is cooled to 350 ° C with water and sent to a multi-stage fluidized chlorinator. Chlorine gas with a pressure of 101 kPa is introduced into the chlorinator, and gold and chlorine dissociated from the pyrite form gold chloride (AuCl ₆ ) gas. In the presence of ferric chloride gas, the temperature is controlled to 310-340 ° C, and the gold chloride is further chlorinated to form a gas phase ferric chloride gold complex (AuFeCl ₆ ). The chemical reaction formula is:

2Au (solid) + Fe ₂ Cl ₆ (gas) + 3Cl ₂ (gas) → 2AuFeCl ₆ (gas)

Thereby the gold is separated from the ore.
There are many methods for recovering gold from ferric chloride gold complexes. For example, when ferric chloride gold complex gas is further heated to a temperature of 475 ° C, AuFeCl6 will produce good dissociation:

2AuFeCl ₆ (gas) → 2Au (solid) + 3Cl ₂ (gas) + Fe ₂ Cl ₆ (gas)

Another method is to recover the iron chloride gold complex gas through a salt bed, and the salt bed will absorb the iron and gold chloride in the gas stream.

AuFeCl ₆ (gas) + 2NaCl (solid) → NaAuCl ₄ (liquid) + NaFeCl ₄ (liquid)

Gold can be recovered from the salt by hydrometallurgical methods.
The high-temperature chlorination method dissolves gold quickly, does not pollute the environment, and can be carried out under water shortage conditions.

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