Method for extracting S, Fe and Au from cyanide tailings

Henan gold mine widespread occurrence with each type of process is less sulfide gold ore. Metal ore pyrite minerals, followed by limonite, a small amount of yellow copper ore, galena and the like; gangue minerals potassium feldspar, sodium feldspar, quartz, biotite. The gold in the ore is mainly symbiotic with sulfide. The particle size of gold mineral is mostly in the range of 0.037~0.01mm, and the packaged gold accounts for 85%~95%, and the crack gold accounts for 5%~15%.

For this type of ore, most gold smelting plants use flotation-gold concentrate cyanide and carbon slurry processes. The main mineral component of the flotation gold concentrate is pyrite. After regrind, cyanide and carbon adsorption recover gold. The tailings are concentrated by thickener and separated by solid and liquid. The tail liquid is purified and discharged, and the cyanide tailings pile is discharged. Save or sell.

According to statistics from various smelting plants, the content of pyrite in such cyanide tailings is generally 80%-95%, and the gold grade is mostly around 3g/t. Gold is mainly encapsulated in pyrite, gangue minerals. The content is 5% to 20%, and basically does not contain gold. Most gold producers do not recycle these cyanide tailings, but sell or pile up cyanide tailings at low prices. At present, the amount of cyanide tailings that have been piled up and produced is considerable.

I. Comprehensive recovery of cyanide tailings

(1) Sedimentation separation and enrichment of gold-bearing iron ore

The mineral component of cyanide tailings is mainly pyrite, followed by feldspar and quartz. Using the relative density difference between the golden iron ore and other minerals, the sedimentation separation and enrichment of the gold-bearing iron ore, improve the gold grade of the material, and reduce the amount of subsequent processing.

The test shows that after the cyanide tailings slurry is precipitated in a static state for a certain period of time, the slurry without sedimentation is discarded, and the precipitate is collected to achieve the effect of enriching the gold-bearing iron ore. The test results are shown in Table 1.

It can be seen from the results of Table 1 that most of the gold-bearing iron ore in the cyanide tailings can be enriched by the sedimentation separation method, the gold grade is improved, and some tailings are discarded. The yield of gold-bearing iron ore after enrichment is 59.21%~88.81%, and the recovery rate of gold is 76.72%-96.66%.

Table 1 Results of sedimentation separation test of cyanide tailings

Note: The tailings slurry used for the test is taken directly from the discharge port of the cyanide plant. The tailings slurry concentration is 37%. The test barrel type container has a diameter of 23cm, a height of 24cm and a volume of about 10L. The mass of the slurry containing solid slag is 5.050kg.

In actual production, the gold-bearing iron ore is enriched from the cyanide tailings, the output is moderate, the gold-containing grade is improved, and it is easy to collect and store, easy to sell and use. According to preliminary estimates, if the gold-bearing iron ore after the sale is enriched, if the gold content is increased by 20 to 30 yuan, the small and medium-sized gold mining enterprises will increase the economic income by one million to several million yuan per year, and the economic benefits can be increased. .

(2) Roasting and enriching gold-bearing iron ore

The golden iron ore is calcined in a closed roaster, the pyrite structure is destroyed, and it is decomposed into sulfur gas and FeS, and the gold is fully exposed. After the sulfur gas is discharged, it is cooled by collection to form sulfur. In this way, 50% of the sulfur in the pyrite is converted into sulfur, which becomes a commodity and produces certain economic benefits.

The main component of the calcination is ferrous sulfide FeS, in which all gold is present, and the gold-containing grade is improved.

Take 10kg of golden iron ore, the gold grade is 3.73g/t, put it in a sealed stainless steel container with pressure exhaust valve, heat it with charcoal fire, the temperature is controlled between 650 °C ~ 700 °C, keep 3.5 ~ 4h. During the roasting process, the pressure exhaust valve continuously discharges sulfur gas. The calcined mass is 7.5 kg and the gold grade is 4.95 g/t. The recovery rate of gold is 99.53%, the loss on material is 2.51kg, the recovery of sulfur is 2.18kg, and the recovery rate of sulfur is 87.2%.

(3) Calcine flooding

There are many unfavorable factors for directly extracting gold from calcination, such as large processing capacity, large equipment investment, high consumption of sodium cyanide, etc., resulting in high production cost.

The calcine is placed in a stirred tank, and a sufficient amount of air is charged in the aqueous medium to agitate the oxidized water to immerse the FeS into FeSO _{4 to} dissolve in the water. The solid slurry of the slurry is separated, and the solid FeSO ₄ formed by evaporation of the solution can be sold; the leaching cyanide immersion gold.

In the test, 5 kg of calcined water was added to the slurry to a concentration of 10%, and a sufficient amount of air was charged. When the oxidation was stopped, the aeration was stopped. Then, an appropriate amount of water was added to precipitate in a static state. After the precipitation was completed, an aqueous FeSO ₄ solution was precipitated and evaporated to obtain 4.890 kg of solid FeSO ₄ . The solid precipitate had a dry mass of 1.86 kg and a gold grade of 13.25 g/t. The recovery rate of gold is 99.58%, and the conversion rate of FeS is 90.15%.

(4) Water leaching cyanide leaching gold

The test conditions and results of water leaching cyanide immersion gold are shown in Table 2.

Table 2 Test results of cyanidation gold leaching

The above series of processes can fully recycle S, Fe and Au in the golden iron ore, and the economic benefits are considerable.

(5) Brief description of the process

The cyanide tailings are enriched and enriched in the gold-bearing iron ore by sedimentation, and part of the tailings are discarded; the closed-type roasting of the golden-bearing iron ore is carried out, the sulfur gas is discharged, and the sulfur is cooled to be sulphur; the baking sand is mixed with air and stirred for water immersion, and then The slurry is subjected to pressure filtration, and the filtrate is evaporated to dryness as solid FeS0 ₄ ; the water leaching residue is immersed in gold by cyanidation. The whole process flow is shown in Figure 1.

Second, the conclusion

The cyanide tailings recyclable in Henan Province is rich in resources, and it can fully utilize the mineral resources and obtain better economic benefits.

The experimental results show that the cyanide tailings can be treated by sedimentation separation-baking-water immersion-cyanide leaching gold process.

43.6% of the sulfur-containing sulphur in the golden iron ore obtained by sedimentation separation, 45.08% of S and 90.15% of Fe are converted into FeSO ₄ , the recovery rate of S is 88.68%, and the recovery rate of Fe is 90.15%. The recovery rate is 95.09%. The recovery of gold in the cyanide tailings is 72.95% to 91.91%.

The process equipment is small, easy to operate, low investment, low cost, small pollution, quick effect, and is an ideal comprehensive recycling process for cyanide tailings.

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