High copper, high arsenic, high sulfur gold ore or gold concentrate cyanide leaching gold process

I. Introduction

When gold ore is leached by cyanidation, the interference of copper , arsenic and sulfur coexist is more serious than the interference of these elements alone ^[1] . At present, high-copper, high-arsenic, high-sulfur symbiotic gold ore or gold concentrate is difficult to be leached by the cyanidation process, and needs to be pretreated by roasting, bacterial oxidation, etc., and has a good leaching rate by cyanide immersion gold process. Therefore, it limits the full utilization of mineral resources of difficult cyanide gold ore. We propose to pretreat with an alkali mixture to improve the cyanidation reaction environment with the activator SMD during cyanidation, which can improve the immersion of copper (1% to 6%), arsenic (6.5%) and sulfur (30%). Gold concentrate gold leaching rate.

The method can obtain better cyanide leaching indexes and good economic benefits for some high-copper, high-arsenic, high-sulfur gold ore or gold concentrate.

Second, industrial trials

(1) A gold mine in Anhui

The gold grade of gold concentrate in a gold mine in Anhui is 18~24g/t, the arsenic grade is 6%~6.5%, the copper is 3%~5%, and the sulfur is about 30%. The leaching of the ore sample by conventional cyanidation method has a leaching rate of 40% to 53% of gold and a leaching time of 48 hours or more. After pretreatment with an alkali mixture for 12 hours before cyanidation, an activator SMD is added during the cyanidation process to leaching. The time is 28~30h, and the gold leaching rate can reach 90%~94%.

Table 2 Analysis of chemical elements in gold concentrate

*Unit is g/t

(2) A gold mine in Xinjiang

A gold ore in Xinjiang is oxidized ore and primary ore. The copper grade in the ore is 3.3%, the arsenic grade is 5.8%, the sulfur grade is 20%, the gold grade is 23.8g/t (oxidized ore) and 6.28g/t (primary ore). The ore is leached by conventional cyanidation method, the leaching rate of gold is 48% to 54%, and the leaching time is 48 hours or more; in the process of cyanidation, after the treatment with 2 kg/t of alkali mixture is carried out for 3 to 4 hours, the cyanide leaching system is maintained. The NaCN mass fraction was 0.09%, the leaching time was 28h, and the gold leaching rate was 97.8% and 93%, respectively.

Third, the test method

Firstly grind the gold ore or gold concentrate in the ball mill to the desired particle size -300 mesh, take 100g of finely ground ore in the stirred tank, adjust the solid-liquid mass ratio to 1:2, add the alkaline mixture 5kg / t, pretreatment 10～15h, add 7～8kg/t NaCN, activator SMD 8～10kg/t, control cyanide system pH 10～11, stir cyanide leaching for 28h.

Fourth, the test results and discussion

The gold concentrate of a cyanide plant in Tongling, Anhui Province, contains 6.5% of arsenic, and about 3% of copper and about 30% of sulfur. The concentrate can only be leached by about 47% to 53% of gold by conventional cyanidation method; after adding the activator, only about 80% of gold can be leached by gasification cyanidation; if pretreatment with alkali mixture before cyanide, The leaching rate of gold is 91% to 94%.

(1) Effect of pretreatment time of alkali mixture on gold leaching rate

The effect of pretreatment of the sample with cyanide on the gold leaching with an alkali mixture is shown in Figure 1. The sample was pretreated with 5kg/t alkaline agent. As the pretreatment time increased, the leaching rate of gold increased. When the pretreatment time was extended to a certain time, the gold leaching rate was over 90%. If the pretreatment was continued, gold The leaching rate has decreased. From the cost considerations, it is more appropriate to choose a pretreatment time of 12h.

Figure 1 Effect of the amount of alkali mixture on the gold leaching rate

(2) Effect of sodium cyanide dosage on gold leaching rate

The effect of the amount of sodium cyanide on the leaching rate of gold is shown in Figure 2. Under the condition of no activator added, the leaching rate of gold increased with the increase of sodium cyanide dosage. The dosage of sodium cyanide reached 15-20 kg/t, and the leaching rate of gold still showed an upward trend. In actual production, it is considered that the sodium cyanide mass fraction in the cyanidation system should be kept at 0.09%.

Figure 2 Effect of sodium cyanide dosage on gold leaching rate

(III) Effect of the amount of activator on the gold leaching rate

When Cu, As, S and other elements coexist in the gold ore sample, the leaching rate of gold can only be increased by more than 20% in the cyanidation process; when arsenic and sulfur are present simultaneously, the leaching rate of gold can be increased by 30%~ 40%; if pretreatment with an alkali mixture before cyanidation, adding the same activator SMD during cyanidation, the leaching rate of gold can reach 91% to 94%. The test results are shown in Figure 3.

(4) Effect of oxidant dosage on gold leaching rate

The addition of an appropriate amount of oxidant during the agitation leaching reduces the consumption of cyanide ions. However, the test results show that the oxidant reduces the leaching rate of gold, and the results are shown in FIG.

(5) The effect of pH on gold leaching rate

The complexation reaction of gold and cyanide is suitable in the range of pH 9-12. According to the test results, it is better to control the pH between 10 and 11, and the results are shown in Fig. 5.

Figure 3 Effect of activator dosage on gold leaching rate

Figure 4 Effect of oxidant dosage on gold leaching rate

Figure 5 Effect of pH on the leaching rate of gold

(6) Effect of mixing time of cyanidation on gold leaching rate

The length of the stirring time has a great influence on the leaching rate of gold. The test results show that the stirring time is 28h, and the results are shown in Figure 6.

(VII) Effect of ore sample size on gold leaching rate

In the gold ore samples where copper, arsenic and sulfur coexist, the size of the ore sample affects the gold leaching and leaching index. The test results show that the gold ore sample size should be -300 mesh, and the test results are shown in Table 3.

Table 3 Effect of gold ore particle size on gold leaching rate

V. Conclusion

We pre-soaked gold ore or gold concentrates of copper, arsenic and sulfur minerals such as Anhui and Xinjiang with an alkali mixture before cyanidation for 12 hours, and added the activator SMD during the cyanidation process, so that the gold leaching rate has a large margin. improve. But this method is not universal. So far, only two gold mines in Anhui and Xinjiang have been industrially applied (see Table 4). This method needs to be widely applied and needs further study.

After the pretreatment of the ore sample by the alkaline agent, the activator is added during the cyanide leaching process, the leaching speed is fast, and the leaching rate is also high, and the results of the pilot and industrial production indicate that there is no influence on the subsequent gold extraction process. If the pretreatment with the alkaline agent is not used, only the SMD activator is added, the leaching rate of gold is not high, and the leaching rate of gold can be greatly improved only after the pretreatment with the alkali mixture. After the gold-containing noble liquid was replaced by zinc wire or zinc powder, the mass concentration of the poor liquid gold was 0.1 mg/L; the mass concentration of the poor liquid gold was 0.01 mg/L.

Table 4 Industrial applications

The method of using alkali mixture treatment and the activator cyanidation gold method is too strong, and the amount of sodium cyanide is large, which is the insufficiency of the method.

references

1 Li Shaoqing, Liu Gang, Sun Bin et al. High arsenic and high sulfur gold ore or gold concentrate cyanide leaching gold process. Gold, 2002, 23 (5): 29.

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