Relationship between Sulfide Type Sulfur Content and Gold Recovery Rate in Calcine
Calcination temperature °C | Content in calcination (%) | Gold recovery rate (%) | Desulfurization rate (%) | Arsenic removal rate (%) | |||
Paragraph | Second paragraph | arsenic | Total sulfur | Sulfide sulfur | |||
400 | 600 | 0.53 | 9.8 | 7.6 | 74.0 | 64.0 | 90.8 |
450 | 600 | 0.63 | 6.3 | 3.8 | 80.0 | 82.3 | 88.3 |
500 | 600 | 0.78 | 2.5 | 0.7 | 80.0 | 93.4 | 87.1 |
550 | 600 | 0.89 | 2.2 | 0.2 | 76.0 | 95.8 | 82.7 |
600 | 600 | 0.95 | 1.8 | Not tested | 67.2 | 95.4 | 85.2 |
Arsenic oxide pyrite, certain antimony-containing minerals and their decomposition products, in the cyanide process can cause great difficulties. According to the literature, when there is a soluble compound with antimony and arsenic, a thin and dense covering film is formed on the surface of the gold particles. They can block the contact of cyanide and oxygen with the gold surface. Thus, the dissolution rate of gold is significantly reduced.
In order to dissolve the oxidized products of arsenopyrite and stibnite, the calcine may be subjected to alkali treatment. However, this operation is very troublesome and needs to be carried out at a high alkali concentration and a temperature of 90 °C. After this alkali treatment, a calcine having a very low arsenic and antimony content can be obtained. This is extremely advantageous for the next step in recovering gold from the calcined product. In the cyanidation process, when the adsorbent is present, there is a great influence on the recovery of gold from the calcined product.
The problem of recovering gold from calcine by adsorption leaching has not been studied. However, this method will help to increase the recovery of gold, and it can also eliminate the heavy work of filtering and depositing gold from the clarified solution.
Using cyanidation and adsorption methods, from 40 to 45 (55 to 60) g / ton, sulfide type sulfur 0.7 to 1.5 (2.0 to 2.5)%, sulfate type sulfur 2 (1)%, arsenic 3 ( 1) The process of recovering gold in the calcine has been achieved.
The calcination of the calcined concentrate with high carbon content is relatively low (less than 1%) and the content of antimony is 0.8 to 0.6%. The carbon content in these calcinations is around 4%. Gold can be recovered from the calcine after leaching the arsenic for 1 hour with an alkali solution at 80 to 90 °C. In the adsorption cyanidation stage, the AM-2B anion exchange resin can increase the gold recovery by 1-2%, while for the carbon-containing calcined product, the gold recovery can be increased by 5%. The proposed adsorption leaching method involves pre-cyanation of the ground calcine followed by adsorption cyanidation.
Since cyanidation is carried out at a very high sodium cyanide concentration (0.4 to 0.5 g/L), and a large amount of AM-21-type anion exchange resin (4 to 5% of the volume of the slurry) is removed. The pre-cyanide operation performed below suppresses the adsorption of gold by the carbonaceous material.
In the adsorption and leaching process of the calcine, the gold process recovery string is 85 to 87%, and in the presence of the carbonaceous material, the gold recovery string is 79 to 81%.
A common disadvantage of the process including the roasting of arsenic-containing gold concentrates is that the flue gas purification system is very complex and the recovery of gold from the calcine is low. Therefore, in the process of recovering gold from refractory arsenic-containing concentrates, some pure hydrometallurgical treatment schemes such as bacterial oxidative leaching and autoclaved oxidative leaching have also been studied. These methods can prevent harmful gases from being emitted into the atmosphere.
The bacterial oxidation leaching process takes a long time. In order to obtain a high gold recovery rate, the bacterial oxidation process must be carried out for 150 to 300 hours depending on the degree of difficulty in handling the concentrate.
The method of performing oxidative leaching on the concentrate first, and then adsorbing cyanidation on the hot leaching slag is relatively promising.
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