Method for leaching precious metal through catalytic oxidation of thiosulfate

Abstract

The invention discloses a method for leaching precious metal through catalytic oxidation of thiosulfate, which comprises the following steps: mixing a copper-containing catalytic system-thiosulfate solution with a precious metal-containing material, and carrying out leaching reaction to obtain a precious metal leachate; wherein a copper-containing catalytic system in the copper-containing catalytic system-thiosulfate solution is a copper-iminodiacetic acid complex. The precious metal is extracted by adopting a copper-iminodiacetic acid catalytic system, the leaching rate of the precious metal and the consumption of thiosulfate can be considered, the leaching effect is remarkably superior to that of an existing copper ammonia system, and industrial application is easy to achieve.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, and in particular to a method for leaching precious metals by catalytic oxidation of thiosulfate. Background Art

[0002] Cyanide has been widely used in precious metal leaching, mainly due to its simple process and mature technology. However, the use of cyanide can cause a series of major toxicological problems related to human health and the environment. Therefore, the research hotspots of scholars at home and abroad are focused on cyanide-free leaching agents, such as halogens, thioureas, thiocyanates and thiosulfates. Among these cyanide-free leaching agents, thiosulfate is considered to be the most promising cyanide-free leaching agent due to its advantages such as non-toxicity, low corrosion to equipment and excellent leaching performance for complex or carbon-containing metal ores.

[0003] Typically, in the absence of a catalyst, thiosulfate leaches precious metals very slowly. 2+ ) is continuously generated, and the dissolution rate of precious metals is significantly accelerated. However, thiosulfate is metastable, Cu(NH3)4 2+ The presence of will significantly accelerate its oxidative decomposition. Therefore, the consumption of thiosulfate in the system is very high, which limits the industrial application of thiosulfate extraction of precious metals. In addition, the decomposition products of thiosulfate include S3O6 3- 、S4O6 2- 、SO3 2- and S n 2- , these decomposition products will form a passivation layer on the surface of precious metals, thus hindering the continuous leaching of precious metals.

[0004] In recent years, researchers have conducted extensive research on reducing the high consumption of thiosulfate, mainly focusing on three aspects: (1) The use of additives; using some additives in the existing thiosulfate system, such as sodium chloride (NaCl), sodium carboxymethyl starch (CMS), carboxymethyl cellulose (CMC), humic acid (HA), sodium sulfite (Na2SO3), etc. Xu Bin et al. found that the addition of HA may destroy the interaction between copper ions and thiosulfate, thereby inhibiting the decomposition of thiosulfate. The results showed that the consumption of thiosulfate dropped significantly from 42.4% to 13.2%. (2) The development of non-copper catalytic systems; using other transition metal ions (including iron, cobalt and nickel) as catalysts instead of copper ions. For example, Dong Zhonglin et al. used Ni(NH3)6 with weaker oxidation ability. 2+ Replace the traditional Cu(NH3)4 2+, it was observed that the consumption of thiosulfate decreased from 53.6 kg / t to 26.5 kg / t. However, the gold leaching efficiency also decreased from 88.3% to 81.2%. (3) Exploration of potential substitutes for ammonia; complexing agents including citric acid (CA) and ethylenediamine di-o-phenylacetic acid (EDDHA) were used as substitutes for ammonia to reduce the consumption of thiosulfate while preventing the negative impact of ammonia release on the environment. Zhang Guowei et al. used EDDHA as a ligand for copper ions and found that it effectively reduced the formation of sulfide on the gold surface, thereby reducing the consumption of thiosulfate to 10.54 kg / t. Although these efforts have achieved a certain degree of success in inhibiting the consumption of thiosulfate, it remains challenging to achieve high leaching rates of precious metals.

[0005] Therefore, there is an urgent need to develop a new catalytic oxidation system that can effectively reduce the consumption of thiosulfate while achieving efficient leaching of precious metals by the thiosulfate method. Summary of the invention

[0006] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for leaching precious metals by catalytic oxidation of thiosulfate, so as to solve the problem that the current thiosulfate leaching technology for precious metals is difficult to balance the consumption of thiosulfate reagents and the leaching efficiency.

[0007] To achieve the above object, the present invention is implemented through the following technical solutions: The invention provides a method for leaching precious metals by catalytic oxidation of thiosulfate, comprising the following steps: mixing a copper-containing catalyst system-thiosulfate solution with a precious metal-containing material, and performing a leaching reaction to obtain a precious metal leaching solution; wherein the copper-containing catalyst system in the copper-containing catalyst system-thiosulfate solution is a copper-iminodiacetic acid complex.

[0008] Preferably, the copper-iminodiacetic acid complex is formed by the coordination of copper ions with iminodiacetic acid or iminodiacetic acid salt.

[0009] Preferably, the initial concentration of copper ions in the reaction system is 0.003-0.05 mol / L; the initial concentration of iminodiacetic acid or iminodiacetic acid salt in the reaction system is 0.01-0.2 mol / L.

[0010] Preferably, the thiosulfate in the copper-containing catalyst system-thiosulfate solution includes one or more of sodium thiosulfate, potassium thiosulfate, calcium thiosulfate, and ammonium thiosulfate; the concentration of the thiosulfate is 0.05~0.5 mol / L.

[0011] Preferably, the precious metal-containing material is precious metal ore slurry, and the slurry liquid-to-solid ratio is (2-10):1.

[0012] Preferably, the precious metal grade in the precious metal ore is 2.0~255 g / t.

[0013] Preferably, the pH of the leaching reaction is 6-11.

[0014] Preferably, the leaching reaction time is 1 to 60 h.

[0015] Preferably, the leaching reaction is carried out under stirring conditions, and the stirring speed is 100~700 r / min.

[0016] Preferably, the precious metal is one or more of gold and silver.

[0017] The beneficial effects of the present invention are: (1) The present invention uses a copper-iminodiacetic acid catalytic system to extract precious metals, which can take into account both the precious metal leaching rate and the thiosulfate consumption, and the leaching effect is significantly better than the existing copper ammonia system; (2) The decomposition products of thiosulfate in the leachate of the present invention are small, and the composition of the leachate is relatively simple, which is conducive to the recovery and recycling of the leachate; (3) The present invention does not add volatile ammonia water, is environmentally friendly, promotes the development of green extraction of precious metals, and is easy to realize industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a diagram of the gold immersion effect of S1-2 in Example 1 and Comparative Examples 1 to 3. DETAILED DESCRIPTION

[0019] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] The current thiosulfate method for extracting precious metals generally uses the copper-ammonia-thiosulfate system, but the biggest problem in the leaching process of this system is that Cu(NH3)4 2+ For S2O3 2-The catalytic oxidation significantly increases the consumption of thiosulfate, and the decomposition products of thiosulfate will form a passivation layer on the surface of the precious metal, thereby hindering the continuous leaching of the precious metal, resulting in poor leaching effect. Based on this, the present invention provides a method for leaching precious metals by catalytic oxidation of thiosulfate, comprising the following steps: mixing a copper-containing catalyst system-thiosulfate solution with a precious metal-containing material, and performing a leaching reaction to obtain a precious metal leaching solution; wherein the copper-containing catalyst system in the copper-containing catalyst system-thiosulfate solution is a copper-iminodiacetic acid complex.

[0021] In some preferred embodiments, the copper-iminodiacetic acid complex is formed by the coordination of copper ions and iminodiacetic acid or iminodiacetic acid salt. The initial concentration of copper ions in the reaction system is 0.003-0.05 mol / L; the initial concentration of iminodiacetic acid or iminodiacetic acid salt in the reaction system is 0.01-0.2 mol / L. The initial concentration of iminodiacetic acid or iminodiacetic acid salt in the reaction system is further preferably 0.05-0.1 mol / L.

[0022] In some preferred embodiments, the thiosulfate in the copper-containing catalyst system-thiosulfate solution includes one or more of sodium thiosulfate, potassium thiosulfate, calcium thiosulfate, and ammonium thiosulfate; the concentration of the thiosulfate is 0.05~0.5 mol / L, and more preferably 0.3 mol / L.

[0023] In some preferred embodiments, the precious metal-containing material is precious metal ore slurry, and the slurry liquid-to-solid ratio is (2-10):1, and more preferably (4-8):1.

[0024] In some preferred embodiments, the precious metal grade in the precious metal ore is 2.0-255 g / t, and more preferably 30-50 g / t.

[0025] In some preferred embodiments, the pH of the leaching reaction is 6-11, more preferably 8-10.

[0026] In some preferred embodiments, the leaching reaction time is 1 to 60 h, more preferably 24 to 48 h.

[0027] In some preferred embodiments, the leaching reaction is carried out under stirring conditions, and the stirring speed is 100-700 r / min, and more preferably 300-500 r / min.

[0028] The method for leaching precious metals by catalytic oxidation of thiosulfate provided by the present invention adopts copper-iminodiacetic acid-thiosulfate to leach precious metals. In the process, iminodiacetic acid forms a copper-iminodiacetic acid complex with copper ions with higher stability to stabilize copper in the solution, so as to weaken the oxidative decomposition effect of the copper ammonia complex on thiosulfate, thereby improving the stability of the precious metal leaching system and reducing the consumption of thiosulfate. At the same time, the copper-iminodiacetic acid complex can be adsorbed on the surface of the precious metal, can catalyze the dissolution of the precious metal, accelerate the leaching process of the precious metal in thiosulfate, and improve the leaching efficiency of the precious metal.

[0029] The present invention is described in detail below with reference to specific embodiments.

[0030] Example 1 To a reaction tank containing 4 L of water, 0.01, 0.05, 0.1, and 0.2 mol / L of iminodiacetic acid, 0.003 mol / L of copper sulfate, and 0.3 mol / L of ammonium thiosulfate were added. After stirring evenly, 1 kg of ore powder containing 43.96 g / t of gold was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 48 h. They were recorded as S1-1, S1-2, S1-3, and S1-4, respectively. The leaching effects are shown in Table 1.

[0031] Table 1 Leaching effect of each group in Example 1

[0032] Example 2 To a reaction tank containing 4 L of water, 0.05 mol / L of iminodiacetic acid, 0.003, 0.01, 0.03, 0.05 mol / L of copper sulfate and 0.3 mol / L of ammonium thiosulfate were added. After stirring evenly, 1 kg of ore powder containing 43.96 g / t of gold was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 48 h. They were recorded as S2-1, S2-2, S2-3, and S2-4, respectively. The leaching effects are shown in Table 2.

[0033] Table 2 Leaching effect of each group in Example 2

[0034] Example 3 To a reaction tank containing 4 L of water, 0.05 mol / L of iminodiacetic acid, 0.003 mol / L of copper sulfate and 0.05, 0.1, 0.3, and 0.5 mol / L of ammonium thiosulfate were added. After stirring evenly, 1 kg of ore powder containing 43.96 g / t of gold was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 48 h. They were recorded as S3-1, S3-2, S3-3, and S3-4, respectively. The leaching effects are shown in Table 3.

[0035] Table 3 Leaching effect of each group in Example 3

[0036] Example 4 To a reaction tank containing 4 L of water, 0.05 mol / L of iminodiacetic acid, 0.003 mol / L of copper sulfate and 0.2 mol / L of ammonium thiosulfate were added. After stirring evenly, 1 kg of ore powder containing 43.96 g / t of gold was added to the solution. The slurry pH was adjusted to 6, 8, 10, and 11. The reaction was carried out at a stirring speed of 500 r / min for 48 h. They were recorded as S4-1, S4-2, S4-3, and S4-4, respectively. The leaching effects are shown in Table 4.

[0037] Table 4 Leaching effect of each group in Example 4

[0038] Example 5 To a reaction tank containing 4 L of water, 0.05 mol / L of iminodiacetic acid, 0.003 mol / L of copper sulfate and 0.2 mol / L of ammonium thiosulfate were added. After stirring evenly, 2, 1, 0.5 and 0.4 kg of ore powder containing 43.96 g / t of gold were added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 24 h. They were recorded as S5-1, S5-2, S5-3 and S5-4, respectively. The leaching effects are shown in Table 5.

[0039] Table 5 Leaching effect of each group in Example 5

[0040] Example 6 To a reaction tank containing 4 L of water, 0.05 mol / L of iminodiacetic acid, 0.003 mol / L of copper sulfate and 0.2 mol / L of ammonium thiosulfate were added. After stirring evenly, 1 kg of ore powder containing 43.96 g / t of gold was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 1, 3, 6, 12, 24, 48 and 60 h, respectively recorded as S6-1, S6-2, S6-3, S6-4, S6-5, S6-6 and S6-7. The leaching effects are shown in Table 6.

[0041] Table 6 Leaching effect of each group in Example 6

[0042] Example 7 To a reaction tank containing 4 L of water, 0.05 mol / L of iminodiacetic acid, 0.003 mol / L of copper sulfate and 0.2 mol / L of ammonium thiosulfate were added. After stirring evenly, 1 kg of ore powder containing 43.96 g / t of gold was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 100, 300, 500 and 700 r / min for 48 h. They were recorded as S7-1, S7-2, S7-3 and S7-4, respectively. The leaching effects are shown in Table 7.

[0043] Table 7 Leaching effect of each group in Example 7

[0044] Example 8 To a reaction tank containing 4 L of water, 0.05 mol / L of iminodiacetic acid, 0.003 mol / L of copper sulfate and 0.2 mol / L of ammonium thiosulfate were added. After stirring evenly, 1 kg of ore powder containing 2.52, 43.96, 115.89 and 255 g / t of gold was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 48 h. They were recorded as S8-1, S8-2, S8-3 and S8-4, respectively. The leaching effects are shown in Table 8.

[0045] Table 8 Leaching effect of each group in Example 8

[0046] Example 9 0.05 mol / L of iminodiacetic acid, 0.003 mol / L of copper sulfate and 0.2 mol / L of ammonium thiosulfate were added to a reaction tank containing 4 L of water. After stirring evenly, 1 kg of ore powder containing 104 g / t of silver was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 48 h. The silver leaching rate was 98.62% and the consumption of thiosulfate was 10.67 kg / t.

[0047] Comparative Example 1 To a reaction tank containing 4 L of water, add 0.05 mol / L of ammonia water, 0.003 mol / L of copper sulfate and 0.3 mol / L of ammonium thiosulfate. After stirring evenly, add 1 kg of ore powder containing 43.96 g / t of gold to the solution, adjust the slurry pH to 8, and react at a stirring speed of 500 r / min for 48 h. The gold leaching rate is 11.29%, and the consumption of thiosulfate is 27.68 kg / t.

[0048] Comparative Example 2 1 mol / L ammonia water, 0.003 mol / L copper sulfate and 0.3 mol / L ammonium thiosulfate were added to a reaction tank containing 4 L of water. After stirring evenly, 1 kg of ore powder containing 43.96 g / t of gold was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 48 h. The gold leaching rate was 21.36% and the consumption of thiosulfate was 15.59 kg / t.

[0049] Comparative Example 3 1 mol / L ammonia water, 0.03 mol / L copper sulfate and 0.3 mol / L ammonium thiosulfate were added to a reaction tank containing 4 L of water. After stirring evenly, 1 kg of ore powder containing 43.96 g / t of gold was added to the solution. The pH of the slurry was adjusted to 8. The reaction was carried out at a stirring speed of 500 r / min for 48 h. The gold leaching rate was 55.31% and the consumption of thiosulfate was 57.22 kg / t.

[0050] Figure 1 The gold leaching effect diagram of S1-2 in Example 1 and Comparative Examples 1, 2, and 3 shows that the leaching rate of precious metals by the copper-iminodiacetic acid catalytic system provided by the present invention is significantly better than that of the copper ammonia system, and the green and efficient leaching of precious metals is achieved while reducing the consumption of reagents, thereby solving the problem that the current thiosulfate gold leaching technology is difficult to balance the consumption of reagents and the leaching efficiency.

[0051] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For matters that are not described in detail in some embodiments, reference may be made to the description in other embodiments.

[0052] The above-mentioned embodiments only express the implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for leaching precious metals by catalytic oxidation of thiosulfate, characterized in that: The steps include: The copper-containing catalyst system-thiosulfate solution is mixed with a precious metal-containing material, and a leaching reaction is carried out to obtain a precious metal leaching solution; wherein the copper-containing catalyst system in the copper-containing catalyst system-thiosulfate solution is a copper-iminodiacetic acid complex.

2. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 1, characterized in that: The copper-iminodiacetic acid complex is formed by the coordination of copper ions and iminodiacetic acid or iminodiacetic acid salt.

3. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 2, characterized in that: The initial concentration of the copper ion in the reaction system is 0.003-0.05 mol / L; the initial concentration of the iminodiacetic acid or the iminodiacetic acid salt in the reaction system is 0.01-0.2 mol / L.

4. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 1, characterized in that: The thiosulfate in the copper-containing catalyst system-thiosulfate solution includes one or more of sodium thiosulfate, potassium thiosulfate, calcium thiosulfate, and ammonium thiosulfate; the concentration of the thiosulfate is 0.05-0.5 mol / L.

5. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 1, characterized in that: The precious metal-containing material is precious metal ore slurry, and the slurry liquid-to-solid ratio is (2-10):

1.

6. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 5, characterized in that: The grade of precious metals in the precious metal ore is 2.0~255 g / t.

7. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 1, characterized in that: The pH of the leaching reaction is 6-11.

8. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 1, characterized in that: The leaching reaction time is 1 to 60 h.

9. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 1, characterized in that: The leaching reaction is carried out under stirring conditions, and the stirring speed is 100~700 r / min.

10. The method for leaching precious metals by thiosulfate catalytic oxidation according to claim 1, characterized in that: The precious metal is one or more of gold and silver.

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