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I. Introduction
Arsenic-containing gold concentrate a gold grade of 15 ~ 18g / t, the arsenic content of 6.12%, a cobalt content of 1.5%, a nickel content of 0.29%, a sulfur content of 10%, these elements are interference gold cyanide Leaching. When the gold concentrate is directly treated with cyanide carbon slurry, the leaching rate of gold is 58.36%; after the gold concentrate is treated with the aiding agent for 6-8 hours, the leaching rate of gold is 5.78%. 68.32%. At the beginning of the leaching stage, the leaching rate of gold increases with the oxidation of arsenic. After a period of time, the arsenic continues to oxidize in the cyanidation system, but the cyanide leaching rate of gold decreases due to the formation of a film on the surface of the gold mineral. Although the arsenic in the final concentrate is basically oxidized, the leaching of the immersible gold is not complete. When the concentrate is treated with the infusion agent for 6-8 hours, the anti-filming agent and activator [1 , 2] are added during the cyanidation process to obtain a better gold cyanide leaching rate. After using this treatment method, when the mass fraction of arsenic in the cyanide leach residue is 2.30%, the leaching rate of gold is 91.2%, and the leaching time is shortened by 8 to 10 hours. This method has great practical significance for the development and utilization of such gold resources.
Second, experimental research
(1) Main mineral components
An arsenic-bearing gold ore has two major categories of oxidized ore and primary ore. After flotation original ore, gold ore more types of mineral, arsenic pyrite, pyrite, cobaltite, nickel and luminance gangue minerals. Gold concentrates contain high arsenic and have a great influence on the cyanidation leaching of gold. Cobalt and nickel also form complexes with cyanide, which affects the cyanide leaching of gold.
(II) Analysis of main elements of mineral samples
Gold concentrate gold and silver in addition, there are arsenic, cobalt, nickel, sulfur and other elements, mainly elemental analysis below.
Analysis table of main elements in gold concentrate
(III) Cyanide carbon leaching process test
The arsenic-containing gold ore is finely ground to -200 mesh, the solid-liquid mass ratio is 1:2.5 with water, the pH of the system is adjusted to about 11 with sodium hydroxide, and 5 kg/t of sodium cyanide and an appropriate amount of activated carbon are added, and the mixture is continuously stirred for 48 hours. The cyanide leaching rate is up to 58.36%.
Third, cyanidation test method
1000g of gold concentrate is finely ground to -200 mesh 90% with 2.5kg/t of the infusion agent, placed in a stirred tank, and the solid-liquid mass ratio is adjusted to 1:2.5 with water, and the mixture is evenly stirred. Adjust the pH of the system to about 11 with sodium hydroxide, add 2.5kg / t anti-filming agent, 5 ~ 8kg / t activator SmD, after cyanidation carbon immersion process, continuous stirring cyanide carbon immersion for 30h, solid-liquid separation The lean liquid can be recycled.
Fourth, test results and discussion
(1) The effect of arsenic oxidation on gold leaching during cyanidation The mass fraction of arsenic in gold concentrate is 6.12%, the leaching rate of gold by direct cyanidation is 58.36%; the sample is calcined at 600 °C ~ 650 °C for 2 h. When the mass fraction of arsenic in the calcine is 4.8%, the cyanidation leaching rate of gold is 80.8%; the ore sample and the infusion agent are uniformly mixed at a ratio of 100:20, and calcined at 550 ° C to 600 ° C for 2 h, the quality of arsenic in the calcine. The fraction of 4.03%, the gold leaching rate reached 87.4%; and after the ore sample was treated with anti-filming agent and activator for 6-8h, the arsenic mass fraction of cyanide leach residue was 2.30%, the gold cyanide leaching rate was 91.2. %. In the cyanidation process, after arsenic is oxidized to a certain extent, gold leaching begins slowly or even stops. After the addition of the anti-filming agent, the passivation of gold during the cyanidation leaching process can be prevented.
In the cyanidation process, the arsenopyrite can be oxidized to Fe 2 (SO 4 ) 3 , As(OH) 3 , As 2 O 3 , etc., and As 2 O 3 reacts with cyanide to form HCN, which can consume cyanide. At the same time, the arsenic sulfide can be well dissolved in the alkali medium to form arsenite, thioarsenite, etc. The dissolution and oxidation of arsenic gradually increase. When the arsenic is reached to a certain extent, these products are easily on the surface of gold minerals. a thin film layer, and gold can seriously hinder CN - chemical reaction between the 2 and O. When the anti-filming agent is added during the cyanidation process, the arsenic mineral can be prevented from forming a film on the surface of the gold mineral after oxidation, thereby ensuring gold leaching.
(II) Influence of the size of the ore sample
If the size of the ore sample is coarse, the leaching rate is low. After the ore samples are respectively ground to -200 mesh 65%, 75% and 100% pass rate, direct cyanidation leaching, the finer the particle size of the ore sample, the higher the gold leaching rate. The test results show that the ore sample size - 200 mesh 100% is suitable.
(III) Selection of pH during cyanidation
The complexation reaction of gold with cyanide has a pH in the range of 9-12. Tests have shown that the pH in the cyanidation system is preferably around 11. The test results are shown in Figure 1.
Figure 1 Effect of pH on gold leaching rate
(4) The effect of sodium cyanide dosage
In the cyanidation system, the leaching rate of gold increases with the amount of sodium cyanide, and the leaching rate is higher when the amount of sodium cyanide is 5 kg/t. In the actual production process should be held cyanide CN - from mass fraction of 0.1% is appropriate. The test results are shown in Figure 2.
Figure 2 Effect of sodium cyanide dosage on gold leaching rate
(5) Influence of the amount of aiding agent
The infusion agent is a colorless transparent liquid, pH 7-8, soluble in water, and is not easily decomposed at normal temperature. After the ore sample is treated with the infusion agent for 5-8 hours, the gold concentrate is treated by the cyanidation carbon immersion process, and the leaching rate of gold is obviously improved. The test results are shown in Figure 3.
Figure 3 Effect of the amount of aiding agent on gold leaching rate
(6) Influence of activator dosage
In the cyanidation process of arsenic-containing gold concentrate, the cyanide leaching rate of gold can be increased by 10% to 20% after adding the activator SmD. The effect of the amount of activator on the gold leaching rate is shown in Figure 4.
Figure 4 Effect of activator dosage on gold leaching rate
(7) The influence of cyanide time
When cyanidation is leached, the length of the stirring time has a great influence on the cyanidation leaching of gold. The test results show that the stirring leaching time is preferably 24 to 30 hours. The time is further extended, and the cyanidation leaching rate of gold decreases due to the re-dissolution. The test results are shown in Figure 5.
Figure 5 Effect of stirring time on gold leaching rate
V. Conclusion
When an arsenic-containing gold concentrate is directly treated by cyanide carbon leaching, the gold leaching rate is low and the leaching speed is slow due to interference of impurities such as arsenic. Even after the calcination treatment, gold leaching still does not reach a good index. The test aid is mixed with the ore sample for 10 min and continuously stirred for 5-8 h. After cyanidation under the conditions of adding anti-filming agent and activator, the cyanidation leaching rate of gold is greatly improved, and the leaching speed is also accelerated. The test results show that after the cyanide leaching gold-containing solution is adsorbed by activated carbon, the mass concentration of gold in the poor liquid is 0.02 mg/L, and the mass concentration of gold after adsorption by ion exchange resin is 0.01 mg/L. After pretreatment with a dipping agent, the arsenic-containing gold concentrate can be treated with a film-preventing agent and an activator cyanidation method to obtain a good gold leaching recovery index, which has good economic benefits.
references
[1] Li Shaoqing, Wang Liping, Luo Jianmin. Cyanide leaching process of a arsenic-containing sulphur- copper gold concentrate
Experimental Research [J]. Gold, 2005, 26(3): 29-31.
[2] Li Shaoqing, Liu Gang, Sun Bin. High copper, high arsenic, high sulfur gold ore or gold concentrate cyanide leaching gold
Process [J]. Gold, 2002, 23(5): 29-31.
Author unit
Chang'an University (Lin Shu, Wu Yarui, Yang Yuhui)
Xi'an Coal Mining Machinery Factory (Yang Chao production)
Changan New Materials Company (Li Shaoqing)
Sinochem Modern Environmental Chemicals (Xi'an) Co., Ltd. (Niu Gang)
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