Electrochemical leaching of gold-arsenic concentrate

At present, seeking and formulating a reasonable gold - arsenic concentrate treatment technology is an urgent issue to be solved in the gold industry. The authors studied the electrochemical oxidation leaching method with gold-containing sulfide concentrates. The purpose was to fully dissociate and expose the fine-grained dispersion gold in the sulfide, and then recover it by cyanidation. Gold-arsenic concentrates were tested in caustic soda solution by electrochemical leaching under laboratory conditions.
Three concentrates were selected belong to the same mine, but the content of the concentrate pyrite and arsenopyrite vary.
Concentrate, pyrite content, arsenic pyrite content, %
I 36.3 18.3
II 15.6 10.7
III 5 8.3
Gold is mainly rich in two minerals, but the gold content in arsenopyrite is higher than pyrite.
All concentrates are refractory concentrates in terms of processing technology. This can be demonstrated by the phase analysis of the gold in the concentrate (see Table 1). According to the roasting process - chemical treatment of the calcine with acid or alkali - the process of cyanidation of the residue to treat the concentrate, the gold content of the cyanide tailings of concentrate I is 4-5 g / ton, while the concentrate The gold content in the cyanide tailings of II and concentrate III is not less than 9~9.4 g/ton.

The electrochemical leaching test was carried out in a special-structure electrolytic cell having a volume of 1 liter. A separate leaching unit is used for each concentrate. At the time of the test, 100 g of the material was weighed, the original concentration of caustic soda was 100 g/liter, and the solution temperature was 70 °C.
According to the research results, for the concentrate I with the highest sulfide content, the best leaching conditions for the gold content in the tailings after the subsequent cyanidation are: liquid: solid = 10:1, current volume The density is 8.3 amps/liter and the leaching time is 8 hours. The optimum leaching conditions for concentrate II and concentrate III are: liquid: solid; 5:1, current bulk density is 5 amps/liter. The leaching time of concentrate II is 8 hours, and the concentrate III is the solution after 6 hours of electrochemical leaching. As of arsenate ion is 6-7 g/L, and 5 of sulfate ion is 5~13 g/ The liter and silicate anions and aluminum have a few milligrams per liter. The remaining concentration of caustic soda is 55 to 75 g/l. After treating the solution with lime, the arsenic is discharged from the solution in the form of a low-dissolved calcium arsenate, and when it is concentrated to 150 g/L with caustic soda and cooled to 16 to 17 ° C, the sulfur is anhydrous sodium sulfate. The form is discharged. By purifying this, the arsenic content in the solution is lowered to 0.7 g/liter, and the sulfur is lowered to 6.5 g/liter, thereby creating conditions for the recycling of the solution. After the solution is treated with lime, 60% of the caustic soda used to leach the arsenopyrite is regenerated. However, the caustic soda used to leach pyrite is not actually regenerated. It remains in solution as sodium sulphate.

As seen from the data in Table 2, when the concentrate I is treated according to the process flow specified in the following figure, the recovery rate of gold is the same level as that of the treatment according to the torrefaction process, and for concentrate II and concentrate III, The gold lost with the cyanide tailings is lower than the calcination process. Dropped by 3/4. [next]

Expanding the cost of processing the concentrate in the electrochemical leaching process The technical and economic calculations show that the various costs depend on the material composition of the concentrate. The content of pyrite in the concentrate is greatly affected. For low-sulfide concentrates, the electrochemical leaching process is economically superior to the roasting process, while for concentrates containing about 15% pyrite, the cost of electrochemical leaching is roughly equivalent to the cost of roasting.
The cost of processing concentrate II is about 66.1 rubles per ton, while that of concentrate III is 53.3 rubles per ton. The cost of processing the gold-arsenic concentrate in accordance with the roasting-baking cyanidation process is 61.4 rubles/ton.
For the treatment of concentrates with high pyrite content (concentrate 1), electrochemical leaching is economically uneconomical. However, for some products containing dipyrite and pyrite, the electrochemical leaching process is economically feasible.
Conclusion For the refractory gold-arsenic concentrates with different arsenic pyrite and pyrite content, electrochemical leaching is effective. After electrochemical leaching of the concentrate, 72-87% of arsenic pyrite and 45~53% of pyrite can be decomposed, so that the tailings gold content after cyanidation of the residue can be compared with the tail treated by the roasting process. The mine has decreased or is roughly equivalent.

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