In recent years, attention has been paid to the treatment of gold ore containing a large amount of arsenic , sulfur and carbon. However, there are many difficulties in recovering gold from such ores.
Soviet Union similar study of two types of ore; (1) a silicon-containing aluminate matrix sulfide - carbonate ore (2) sulfide ore containing silicate and aluminosilicate matrix. The first 18% of carbonate ore, sulfides (pyrite and arsenopyrite) 6%. The oxidized ore sample contained 2.4% arsenate and sulfate. The amount of sulfides (such as pyrite, arsenopyrite, and stibnite ) in the second type of ore accounted for 5.4%; in the ore samples after oxidation, iron oxide and iron hydroxide reached 6%.
In the oxidized ore, the content of sulfide-type sulfur is small, accounting for 0.1% or less. The gold in the ore forms inclusions of submicron particles in pyrite, arsenopyrite and stibnite. In the ore after oxidation, the gold particles increase slightly, reaching a few tenths and a few micrometers.
The chemical composition of the first type of sulfide ore: total sulfur content is 2.6 to 2.9%, sulfuric acid type sulfur is 0.1%; organic carbon is 0.05%; arsenic is 0.87%. For this type of oxidized zone ore, it is characterized by a large amount of arsenic (about 0.7%). Sulfide-type sulfur was not found in this ore.
The second type of sulfide ore sample is characterized by a low arsenic content (about 0.18%) and a rhodium content of 0.2%. The total sulfur content in the ore is 2.7%, and the sulfate type sulfur is 0.1%. The organic carbon content is much higher than in the first type of ore, about 1.1%. In this type of oxidized ore, like the first type of ore, there is no sulfide-type sulfur, and the contents of arsenic and antimony are 0.06% and 0.08%, respectively.
In order to recover gold from oxidized ores, it has been proposed to treat ore using a non-filtration adsorption process and to test it under semi-industrial conditions. The process includes: crushing, grinding (the ore fineness of the ore reaches 95 to 98%-0.1 mm), classification, and the slurry is dense (making the liquid-solid ratio II: 1.1: 1.2). The cyanidation is then carried out and the gold is recovered from the thick product.
The adsorption capacity of the anion exchanger fluctuates between 13 and 18 mg/g. When processing oxidized ore, the process recovery of gold is 3 to 86%. The phase analysis of the adsorbed tailings shows that when the ore is treated according to this process, about 80-90% of the gold that is not recovered is finely immersed in quartz and sulfide, and is oxidized. Covered. Therefore, this part of the gold cannot be recovered during the cyanidation process.
The behavior of the first and second types of oxidized ores differs during the cyanidation process. The first type of ore is characterized by the absence of monomeric gold in the adsorbed tailings, while in the tailings of the second type of ore, monomeric gold accounts for 7.3% of the total amount of gold lost in the tailings. Therefore, in order to recover the monomer gold more completely from the second type of ore, it is necessary to extend the time of cyanidation or to preselect the monomer gold at the beginning of the process.
Semi-industrial tests have shown that it is possible to treat these ores with a direct adsorption cyanidation process. It is very difficult to recover gold from the first type of ore that is extremely difficult to handle. This is because the gold in the sulfide is in a fine-grained state in the case where the gold content in the ore is very low. Special methods should be used for such ores, such as flotation first; then recovering gold from flotation concentrates using a more complex process.
In the flotation process, according to the type of mineral is floated different stone, gold obtained 31 to 34 g / t, sulfide sulfur from 20 to 26%, arsenic S ~ 5%, 0 to 0.8% antimony, the carbonaceous material 1 to 4% of flotation concentrate.
When recovering gold from refractory gold-bearing concentrates, the most common method is to first calcine; then cyanide the calcination. After calcination, a calcine and a calcine having a low arsenic content can be obtained. This is advantageous for the recovery of gold. The flotation concentrate should be calcined in two stages in the boiling layer. The calcination temperature in the first stage of calcination is 450 to 500 Â° C, and the calcination temperature in the second stage is 600 to 650 Â° C (for concentrates containing no antimony and carbon). Under this condition, gold has the highest recovery rate in the subsequent adsorption cyanidation process. For carbon-containing concentrates, the following roasting regime is recommended: the first stage has a calcination temperature of 550 Â° C and the second stage of roasting at a temperature above 650 Â° C.
If it is considered that gold is finely immersed in the sulfide in the first type of ore of the deposit, the loss of gold with the tailings during the treatment of the calcine is due to insufficient oxidation, so that the dense iron oxide cannot be made. Gold symbiotic with arsenic oxide is dissociated. In order to reduce the content of sulfide in the calcining, the method of increasing the calcination temperature is adopted, and the recovery string of gold cannot be increased. The effect of the residual content of sulfide-type sulfur on the recovery of gold from the calcine is shown in the attached table.
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