What are the commonly used leaching agents for gold mine pretreatment?

The purpose of using leaching agents in gold mine pretreatment is to chemically react with gold and other components in the gold mine, destroy the gold packaging structure, dissociate the gold from the ore and dissolve it in the solution, so as to improve the efficiency and recovery rate of subsequent gold extraction. At present, the commonly used leaching agents in gold mine pretreatment can be divided into traditional cyanide agents and emerging non-cyanide agents. They have their own characteristics and are suitable for different types of gold mines.

1. Traditional cyanide agents

Sodium cyanide: It is a widely used gold leaching agent. In an aerobic environment, it can react chemically with gold to form a water-soluble gold-cyanide complex, which dissolves gold from the ore. Sodium cyanide has the advantages of high leaching rate and good selectivity, and can achieve good leaching effects for most gold mines. However, sodium cyanide is highly toxic. If it leaks during use, it will cause serious harm to the environment and human body, and the treatment cost of cyanide-containing wastewater is high.

Potassium cyanide: Similar to sodium cyanide, it also forms a complex with gold to achieve gold leaching. Its leaching ability is slightly stronger than that of sodium cyanide, but the cost is relatively high, and it is also highly toxic, so safety regulations must be strictly followed in its use and management.

2. Non-cyanide agents

Thiourea: In an acidic medium, thiourea can react quickly with gold to form a stable complex, thereby leaching gold. Compared with cyanide, thiourea has lower toxicity and faster leaching speed, and has better adaptability to certain difficult-to-treat gold mines (such as carbonaceous gold mines). However, thiourea is unstable under acidic conditions and easily decomposes, resulting in large agent consumption and high production costs.

Thiosulfate: Common sodium thiosulfate can react with gold under alkaline conditions to form a gold thiosulfate complex. The thiosulfate leaching method has the advantages of environmental protection and low corrosion to equipment, and is suitable for treating gold mines containing impurities such as copper and arsenic. However, the leaching process of this method is relatively complicated, with many influencing factors, and the leaching rate of gold may be lower than that of the cyanide method.

3. Halogen agents

Chlorides: such as chlorine gas, sodium hypochlorite, etc., can produce chlorine free radicals with strong oxidizing properties in aqueous solution, which can oxidize and dissolve gold. The chloride leaching method has the advantages of fast leaching speed and low reagent cost, but chlorine gas is irritating and toxic. Safety protection should be paid attention to when using it, and harmful gases may be produced during the leaching process.

Bromide: Bromine and its compounds can also be used as gold leaching agents. Under certain conditions, they can react with gold to form soluble gold-bromine complexes. The bromide leaching method has the characteristics of high leaching efficiency and mild reaction conditions, but bromine is highly volatile and easily causes environmental pollution.

Amino acid agents: Certain amino acids (such as glycine) can form complexes with gold under certain conditions to achieve gold leaching. Amino acid reagents have the advantages of being non-toxic and environmentally friendly. They are a new type of gold leaching reagent with development potential. However, their leaching effect and stability need to be further improved, and there are still certain technical difficulties in large-scale application.

The above are the types of leaching agents commonly used in gold ore pretreatment. In actual ore dressing plants, how to use the reagents, which one to choose, and how much to use, all need to be selected according to the characteristics of the gold ore and the processing volume. Therefore, ore dressing test analysis can be carried out first, and then the appropriate gold pretreatment technology and reagents can be determined.