Gold-arsenic ore and its concentrate processing method (2)

When the gold arsenic concentrate or the calcined calcined cyanide is treated, it has different characteristics. When the concentrate is cyanated, it should be treated with alkali in advance, cyanized in stages, and leached with a cyanide solution of low-concentration calcium oxide. If a simple sulfide (or estrogen yellow realgar) ore or a concentrate containing arsenic, it must be treated with the test method of antimony ores and concentrates containing at cyanide. The calcination after calcination usually requires washing with water, followed by cyanidation and maintaining the concentration of NaCN in the cyanide solution at 0.08% or more. The consumption of cyanide and lime can be greatly reduced by rinsing. For calcined sand containing difficult to recover gold, it can be treated with two or three stages of cyanidation, and if necessary, intermediate treatment with alkali. The base dissolves the oxides of arsenic (especially iron arsenate) and exposes the gold encapsulated in these compounds. When processing the calcine, an alkali solution having a NaOH concentration of 6 to 8% is required. The slurry is heated to 80~90% °C for 2~3 hours. The material is then dewatered, and finally cyanidation is carried out and the gold in the liquid phase is examined and analyzed. By adding a hydroxide or calcium oxide to the solution, the alkali solution containing Na ₃ AsO ₄ can be regenerated. Arsenic precipitates as calcium arsenate and the solution is concentrated with NaOH .

First incompletely oxidizing roasting, and then volatilizes from gold chloride - practicable method - the recovery of gold arsenic concentrate. The conditions of the chlorination volatilization test are as follows: the sulfur content in the calcine is 3.5 to 4% , the NaCl consumption is 7.5 to 10% of the weight of the calcine , and the temperature of the chlorination is 1000 °C . Under these conditions, about 96 to 98% of the gold is transferred to the volatiles and recovered.

Decomposition Gold - Concentrate autoclave Arsenic - alkali leaching method is worth further study. At temperature 100 °C , the partial pressure of oxygen in the gas phase is 10 atm, using 150~ 180 grams / liter NaOH solution for 2 hours of tempering of the concentrate , can ensure that + points completely decompose the sulfide, so that 98 ~ 99% of arsenic and sulfur into the liquid phase. The gold in the leaching slag after rinsing can be recovered by cyanidation (without adding lime). The autoclave can be achieved in an aqueous medium by passing oxygen in the air through an autoclave at 50 atm. Under these conditions, arsenic is oxidized to form iron arsenate and sulfuric acid.

Bacterial leaching is a promising method for oxidizing gold -series concentrates. Using this - method can substantially completely expose the gold. The arsenic compounds (mainly arsenate and calcium arsenite) obtained after bacterial leaching are poorly soluble in water and have little toxicity. This is unmatched by the arsenic compound formed during the roasting process and the pyrometallurgical smelting process.

In order to oxidize arsenic pyrite, it is recommended to use artificially cultured Thiobacillus ferrooxidans in a concentration of 106-107 cells / ml in the original solution . Bacterial leaching tests are carried out under static conditions and the best values ​​for the following main parameters must be determined:

The pH of the original bacterial solution ;

The concentration of ferric iron,

Liquid to solid ratio in raw pulp

The time of bacterial leaching.

The raw values ​​of these parameters are: pH ; 1.8~2 ; the concentration of Fe ³⁺ is 3~ 4 grams / liter, liquid to solid ratio = 30 ~ 50 , time is 300 ~ 400 hours. The bacteria are then adapted to the specific conditions, the solution is subjected to intermediate arsenic removal (adding lime milk to a pH of 3 to 3.5 ), and the bacterial leaching test is organized according to a downstream process in an effort to shorten the time of bacterial leaching and to be thicker. pulp achieve this - method. For some gold - arsenic concentrate, the optimal conditions for arsenopyrite oxidation is started: liquid ratio = 5: 1, the leaching time was 120 to 150 hours. While the arsenic pyrite is oxidized, part of the pyrite (about 30-40% ) is also oxidized.

The leaching residue after the leaching of the bacteria is washed with water, and then the leaching residue is cyanated. In addition to the cyanidation method, it is also possible to carry out tests using a thiourea method, a water chlorination method, or the like.

For gold, there is exposed from the pyrite and arsenopyrite in - some relatively new method (e.g., chemical mechanical and electrochemical methods) should be emphasized.

Partially oxidizing the arsenic contained in the ore are - part is in the form of scorodite oxide and other minerals condition exists. The gold in this ore is covered by a scorodite film, making it difficult to perform flotation and cyanidation. The scorodite can be floated with a fatty acid collector .

In order to recover gold and arsenic from partially oxidized ore, it can be tested using a process that includes the following operations:

The flotation gold and sulfide are collected by a sulfhydryl group, and the concentrate is calcined and calcined to cyanide;

Flotation tailings are treated with NaOH solution to leach arsenic and remove the film on the surface of the gold particles;

The residue is treated by cyanidation;
Arsenic is precipitated from an alkaline solution with lime or a high concentration of NaOH solution. Lime can precipitate and also regenerate NaOH. The regenerated NaOH can be recycled.

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