A method for extracting gold from gold mines using micro-free cyanide

Abstract

The invention discloses a method for extracting gold from a micro-free cyanide of a gold mine, and relates to the technical field of gold leaching from ores. The method includes steps such as low-free cyanide gold leaching, adsorption of precious liquid, and Cu recovery. The method constructs a leaching solution of micro-free cyanide by adding an appropriate amount of copper-cyanide complex in leaching agents such as glycine, N, N-bis(hydroxyethyl)cocamide or hydroxyethylidene diphosphonic acid, and controls the gold leaching effect with high leaching rate, low cyanide consumption, environmental friendliness, and cost controllability by specific process conditions and parameters. The present invention effectively solves the problems of serious cyanide pollution, slow gold leaching rate, and copper interference in the gold leaching process in traditional gold leaching processes, and has broad application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of ore gold leaching, and in particular relates to a method for extracting gold from a gold mine using micro-free cyanide. Background Art

[0002] As a precious metal with important economic value and strategic significance, gold plays an indispensable role in the global economic system. Its wide application in many fields such as financial investment, electronics industry, and jewelry has led to a continuous increase in the demand for gold, which has also prompted the continuous evolution and innovation of gold extraction technology.

[0003] The traditional cyanide gold leaching process has been used for a long time and occupies a dominant position in the field of gold production. This process is based on the good solubility of cyanide solution in gold and can effectively extract gold from ore. However, the highly toxic nature of cyanide poses an extremely serious threat to the environment. In the gold production process, if cyanide is not used and managed properly, its leakage or discharge may cause long-term and irreversible pollution to the soil, water and atmosphere, posing a major risk to ecological balance and human health. At the same time, with the increasing awareness of environmental protection and increasingly stringent environmental regulations, the environmental pressure faced by the traditional cyanide gold leaching process is increasing day by day, and there is an urgent need to explore more environmentally friendly alternative processes.

[0004] Among the many gold resources, the treatment of gold ore is a challenging problem. Copper exists in various forms in the ore and has a strong affinity with cyanide. When the cyanide leaching process is used to treat copper-containing gold ore, copper will quickly react with cyanide to form a stable copper-cyanide complex. This not only leads to a large consumption of cyanide and increases production costs, but also significantly reduces the leaching efficiency of gold due to competitive adsorption of copper-cyanide complexes. Therefore, how to effectively solve the interference of copper in the cyanide leaching process has become the key to improving the resource utilization rate and economic benefits of copper-containing gold mines.

[0005] In recent years, non-cyanide gold leaching technology has gradually become a research hotspot, among which the gold leaching technology using copper cyanide complex or glycine as leaching aid has attracted much attention due to its environmental friendliness. It shows the potential to leach copper and gold from ores or concentrates, and the leaching system is not interfered by external cations (such as Fe, Mn, Cr, Mg, Al and Si, etc.). However, the above leaching aids generally have the defect of low leaching rate. Even at higher temperatures (about 50-60°C), its gold leaching rate is still much lower than that of conventional cyanide gold leaching process. In addition, the problem of slow gold leaching rate is more prominent, which prolongs the production cycle and has low production efficiency. It cannot meet the needs of efficient and rapid production in the modern gold industry, and seriously restricts its large-scale application in industrial production. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a method for extracting gold from gold ore with micro-free cyanide, so as to solve the problems of cyanide pollution, low leaching rate, slow gold leaching rate and copper interference in the existing gold extraction process.

[0007] The technical solution of the present invention is as follows:

[0008] A method for extracting gold from a gold mine using micro-free cyanide is carried out according to the following steps:

[0009] The first step, low free cyanide leaching gold:

[0010] 1) For high-copper gold ores with Cu>1%, chelating agents and glycine are added to the pulp; for low-copper gold ores with Cu≤1%, chelating agents, glycine and copper-cyanide complex are added to the pulp for leaching pretreatment;

[0011] 2) Use sodium cyanide for further leaching to achieve low free cyanide leaching of gold;

[0012] The method for preparing the copper cyanide complex is as follows: CuCN and liquid sodium cyanide are prepared into the copper cyanide complex, and the CN:Cu ratio is within a suitable range;

[0013] The chelating agent is hydroxyethylidene diphosphonic acid or N,N-di(hydroxyethyl)cocamide;

[0014] The second step is to extract gold by adsorption of precious liquid:

[0015] Use activated carbon to adsorb the leached precious liquid and collect the gold in it;

[0016] The third step is to recover Cu: sodium sulfide is added to the lean solution after carbon adsorption to recover Cu at a certain pH.

[0017] Preferably, the suitable molar ratio range is: CN:Cu molar ratio is (1.5~3):1.

[0018] Further preferably, the suitable molar ratio range is: CN:Cu molar ratio is 2.5:1.

[0019] Preferably, in step 1) of the first step, the slurry concentration is 30-40%, the amount of chelating agent added per ton of slurry is 1-10 kg; the amount of glycine added per ton of slurry is 2-20 kg; and the amount of copper cyanide complex added per ton of slurry is 1-8 kg.

[0020] Preferably, in the first step, the leaching process conditions are: temperature of 15-50° C., sodium hydroxide solution is used to adjust the pH value of the slurry to 11.5, the stirring rate is 300-800 r / min, and the total leaching time is 48-84 h.

[0021] Preferably, in the third step, the certain pH refers to pH 2-5.

[0022] Preferably, the slurry is obtained by grinding the gold ore raw material and then adjusting the slurry concentration; the grinding process is to grind the gold ore raw material to a particle size of less than 74 μm accounting for more than 90 wt% of the whole proportion; it contains 2.5-5 g / t of gold. Compared with the prior art,

[0023] The beneficial technical effects of the technical solution of the present invention are:

[0024] 1) High leaching rate: The leaching rate of the ore treated by the method of the present invention is high, which is equivalent to the recovery rate of traditional sodium cyanide leaching, ensuring the efficient extraction of gold.

[0025] 2) Environmentally friendly: The free cyanide content during the leaching process is extremely low, and the leaching tailings do not need to be harmlessly treated to meet the Class II solid waste standards, greatly reducing pollution to the environment.

[0026] 3) Reduce cyanide consumption: For high-copper concentrates, pre-treatment with leaching agent for copper leaching significantly reduces the cyanide consumption in the subsequent gold leaching process, thereby reducing production costs.

[0027] 4) Controllable costs: The recyclable utilization of leaching agents in the low free cyanide leaching system and the reduced cost of leaching residue treatment have certain economic advantages in the long run.

[0028] 5) Fast gold leaching rate: The method of the present invention has the outstanding characteristics of short leaching time and fast rate. DETAILED DESCRIPTION

[0029] The present invention is further described below in conjunction with examples and experimental data.

[0030] Example 1

[0031] The grade of Au in the gold ore used to prepare the slurry is 4.1g / t, the Cu content is 0.06%, and the slurry concentration is 35%. The amount of hydroxyethylidene diphosphonic acid added as a chelating agent is 1.5kg per ton of slurry, the amount of glycine added is 2.5kg per ton of slurry, and the amount of copper cyanide complex added is 1.7g per ton of slurry. By adjusting the concentration of CuCN, different CN:Cu molar ratios (4:3, 5:3, 6:3, 7:3, 8:3) of copper cyanide complex were set. The pH value was adjusted to 11.5, the stirring speed was 400r / min, and the leaching temperature was 30℃, and the leaching pretreatment was carried out for 6 hours.

[0032] Under the condition of sodium cyanide concentration of 0.5g / L (i.e. 500g per cubic meter of slurry), the pH value was adjusted to 11.5, the stirring speed was 400r / min, and the leaching temperature was 30℃, and the leaching was continued for 48 hours.

[0033] The results show that the Au leaching rates are 62%, 71.5%, 87.5%, 91% and 92% corresponding to different CN:Cu molar ratios, respectively.

[0034] Example 2

[0035] When the CN:Cu molar ratio of Example 1 was 7:3, other conditions remained unchanged, and the amount of glycine added was adjusted to 1 kg per ton of pulp, 2 kg per ton of pulp, and 3 kg per ton of pulp, respectively. The results showed that the Au leaching rates under this system were 26%, 87%, and 91%, respectively.

[0036] Example 3

[0037] On the basis of Example 2, suitable activated carbon was selected to conduct adsorption test on the precious solution leached by copper cyanide complex + glycine micro-free cyanide system. The effect of CN:Cu molar ratio on Au adsorption rate was compared. When the CN:Cu molar ratio was not less than 2.5, the Au adsorption rate could reach 99.02%, while the Cu adsorption rate was 45%, which effectively reduced the competitive adsorption of copper.

[0038] Example 4

[0039] For the lean solution after carbon adsorption (Cu822mg / L), the Cu content in the lean solution was accurately calculated and an appropriate amount of sodium sulfide was added to carry out a Cu recovery test. After the reaction was completed, the pH value of the supernatant was measured to be 3.0 using a precision pH meter, and the Cu content in the precipitated product was 58.33% and the Fe content was 3.00%, achieving efficient copper recovery.

[0040] Example 5

[0041] The gold ore used for preparing the slurry has an Au grade of 3.9 g / t, a Cu content of 8.32%, and a slurry concentration of 35%. The amount of hydroxyethylidene diphosphonic acid added as a chelating agent is 1.5 kg per ton of slurry, and the amount of glycine added is 10 kg per ton of slurry. The pH value is adjusted to 11.5, the stirring speed is 400 r / min, and the temperature is 30°C, and the leaching pretreatment is performed for 6 hours.

[0042] Then, 0.5 g / L (i.e., 500 g per cubic meter of slurry) of sodium cyanide was added, and the leaching was carried out for 48 hours at a stirring speed of 400 r / min and a temperature of 30°C.

[0043] The results showed that the Cu content in the precious solution was 3.04 g / L and the Au content was 517.7 mg / L.

[0044] Example 6

[0045] The Au grade in the gold ore used to prepare the slurry is 3.9 g / t, the Cu content is 8.32%, and the slurry concentration is 35%.

[0046] 0.5 g / L (i.e., 500 g per cubic meter of pulp) of sodium cyanide was added, the stirring speed was 400 r / min, and the temperature was 30°C for 48 hours. The results showed that the Cu content in the precious solution after leaching was 8.90 g / L, and the Au content was 482.8 mg / L. Compared with Example 5, the leaching rate of Cu was significantly improved, while the leaching rate of gold was reduced. This shows that the pretreatment of Example 5 effectively inhibited the leaching of copper and increased the leaching rate of gold.

[0047] Example 7

[0048] Example 2 When the amount of glycine added is 2 kg per ton of slurry, other conditions remain unchanged, the chelating agent is adjusted to N, N-di(hydroxyethyl)cocamide, and the amount is adjusted to 2 kg / t. The Au leaching rate under this system is 79%.

[0049] Comparative Example 1

[0050] The same raw materials as in Example 1 were used, and the leaching was carried out by cyanidation method at a pulp concentration of 35%, a pH value of 11.5, a sodium cyanide concentration of 0.5 g / L (i.e., 500 g per cubic meter of pulp) for 48 hours, and the slurry was adjusted with clean water. The gold leaching rate of the cyanidation method was 92.51%, and the leaching rate of the low free cyanide leaching method was 92.27%, which were close to each other, and the low free cyanide leaching residue was T CN The toxic leaching index is 1.77 mg / L, which is lower than 7.2 mg / L of leaching residue from the cyanide process, which fully proves the effectiveness of the present invention.

[0051] Comparative Example 2: Based on Example 1, no copper cyanide complex or chelating agent was added, the CN:Cu molar ratio was 7:3, and the leaching time was 24, 48 and 72 hours, respectively. In this system, the Au leaching rates were 37%, 67% and 88%, respectively.

[0052] By comparison, the Au leaching rate (91%) of the method of the present invention (Example 1) after leaching for 48 hours far exceeds the Au leaching rate (67%) of Comparative Example 2 at the same leaching time, indicating that the method of the present invention has a short leaching time and a fast rate.

[0053] The gold ore slurry of the present invention is obtained by first grinding the gold ore raw material and then adjusting the slurry concentration; the grinding process is to grind the gold ore raw material until the part with a particle size less than 74μm accounts for more than 90wt% of the whole proportion.

[0054] The N,N-di(hydroxyethyl)cocamide of the present invention is also known as coconut acid diethanolamide, abbreviated as CDEA in English, and has a CAS number of 68603-42-9.

Claims

1. A method for extracting gold from a gold mine using micro-free cyanide, characterized in that Follow these steps: The first step, low free cyanide leaching gold: 1) For high copper gold ores with Cu>1%, add chelating agents and glycine to the slurry; for low copper gold ores with Cu≤1%, add chelating agents, glycine and copper cyanide complex to the slurry; The pH value was adjusted to 11.5, the stirring speed was 400 r / min, the leaching temperature was 30°C, and the leaching pretreatment was performed for 6 hours; The slurry concentration is 30-40%, and the amount of glycine added per ton of slurry is 2-20 kg; 2) Use sodium cyanide for further leaching to achieve low free cyanide leaching of gold; The copper cyanide complex preparation method is as follows: CuCN and liquid sodium cyanide are prepared into a copper cyanide complex, and the molar ratio of CN:Cu is (1.5-3):1; The chelating agent is hydroxyethylidene diphosphonic acid or N,N-di(hydroxyethyl)cocamide; The second step is to extract gold by adsorption of precious liquid: Use activated carbon to adsorb the leached precious liquid and collect the gold in it; The third step is to recover Cu: sodium sulfide is added to the lean solution after carbon adsorption to recover Cu at pH 2~5.

2. The method for extracting gold from a gold mine using micro-free cyanide as claimed in claim 1, characterized in that The CN:Cu molar ratio is 2.5:

1.

3. The method for extracting gold from a gold mine using micro-free cyanide as claimed in claim 1, characterized in that: In step 1) of the first step, the slurry concentration is 30-40%, the amount of chelating agent added per ton of slurry is 1-10 kg; the amount of copper cyanide complex added per ton of slurry is 1-8 kg.

4. The method for extracting gold from a gold mine using micro-free cyanide as claimed in claim 1, wherein: In the first step, the leaching process conditions are: using sodium hydroxide solution to adjust the pH value of the ore pulp, and the total leaching time is 48~84h.

5. The method for extracting gold from a gold mine using micro-free cyanide according to any one of claims 1 to 4, characterized in that: The slurry is obtained by first grinding the gold ore raw material and then adjusting the slurry concentration; the grinding process is to grind the gold ore raw material until the part with a particle size less than 74μm accounts for more than 90wt% of the whole proportion; it contains 2.5~5g / t of gold.