Refractory gold-bearing arsenic minerals how can they be leaching?

Case:
Arsenic-bearing gold ores are generally refractory ores, and the development and utilization of its resources is a worldwide problem. Arsenopyrite (arsenopyrite), orpiment and realgar are the main arsenic minerals in arsenic-bearing gold ores. Arsenopyrite is one of the most common gold-carrying minerals, often encapsulated with finely dispersed gold particles, in which case even ultrafine grinding of the ore cannot completely dissociate the gold particles. Therefore, the pretreatment process of arsenic-bearing gold ore is one of the leading directions of scientific and technological research on gold extraction technology. Fine-grained states are encapsulated within or between individual crystals of arsenopyrite or pyrite. When gold and arsenopyrite coexist, a black or dark brown surface film will be formed to cover the surface of gold.

When gold is extracted, the above phenomenon results in a very low gold recovery rate.
Solution:
1. Roasting oxidation pretreatment
The roasting oxidation method is a traditional process in non-ferrous metal beneficiation and metallurgy, and it is also the most common and reliable method for processing gold-bearing sulfide ores, especially carbon-bearing sulfide ores.
The purpose of roasting is to decompose the sulfide to expose the gold particles, to volatilize the sulfides of arsenic and antimony in an oxidized state, and to burn or inactivate the carbonaceous substances; The next step of cyanide leaching gold provides good power conditions.
A roasting process is a multiphase chemical reaction, and the main influencing factors are temperature, physicochemical properties of reactants and products (particle size, porosity, chemical composition, etc.), airflow characteristics, and oxygen concentration in the gas.

2. Wet chemical pretreatment
1) Atmospheric pressure alkaline leaching pretreatment
Atmospheric pressure alkaline leaching pretreatment is to oxidize and treat the relevant components of the ore by adding chemical reagents under normal pressure, and the medium is alkaline.
2) Normal pressure acid treatment
Atmospheric acid treatment is usually the oxidation treatment of refractory ore with only peroxymonosulphuric acid.
3) Wet Chlorination
The water chlorination method is used for the direct gold extraction of carbonaceous gold ores. Unlike gold extraction, the reagents used in pretreatment are not chlorine gas, but hypochlorite, high-valent ferric chloride and copper salts, and chlorination. sodium etc.
4) HNO3 decomposition method
The use of HNO3 to oxidize arsenic pyrite can fully decompose the sulfide in the raw material, thereby enriching Au exponentially, which is beneficial to the recovery of Au.
5) Hot pressing chemical pretreatment
The use of hot-pressed oxygen leaching for the pretreatment of refractory ore can improve the cyanidation rate of gold and reduce the consumption of cyanide.
The hot-pressed oxidation method is mainly used for the pretreatment of sulfide ores and arsenopyrite. According to the different medium environments, it is divided into hot-pressed oxygen acid leaching and alkali leaching.

3. Bacterial oxidation pretreatment
The research on bacterial pre-oxidation is quite active. As early as the 1960s, the former Soviet Union discovered a new lytic autotrophic Thiobacillus ferric oxidans in the work of bacterial leaching of arsenic gold ore, using this arsenic-resistant bacteria to decompose arsenic yellow Iron ore and pyrite can dissociate Au encapsulated in it. The mechanism of action is exactly the same as the process of pressurized oxidation, and bacteria play the role of catalytic oxidation. Under the action of bacteria, the decomposition and oxidation process of many minerals can be accelerated by dozens or even hundreds of times.

After leaching for 60-120 hours, the oxidation rate of arsenopyrite can reach 80%-90%; when the leaching residue is treated with cyanidation, the small-scale test results show that the gold leaching rate increases by 30%-50% during cyanidation after biological oxidation .

4. Other preprocessing techniques
1) Vacuum dearsenic method.
2) Volatile smelting method.
3) Segregation roasting method. As gold development progresses, pretreatment technology of high arsenic gold ore has become more and more important. Research on pretreatment technology needs to be further developed and deepened to address the diverse characteristics of arsenic-containing refractory gold resources.

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