A method for leaching gold from gold-containing material without cyanide

Abstract

The present invention provides a method for cyanide-free leaching of gold from gold-containing materials, comprising the following steps: preparing a gold leaching reagent by mixing formamide and / or ammonium formate with thiourea in a mass ratio of 4:1 to 10:1; placing the gold-containing material in an aqueous solution containing the gold leaching reagent, adding an oxidizing agent, leaching under acidic conditions, and filtering to obtain a gold-containing solution and leaching residue. This method promotes cyanide-free gold leaching. Compared with existing gold leaching methods, this method can not only leach gold at high ferric iron concentrations, but also within a wider solution pH range. This method overcomes the problem that existing reagents, such as thiourea and polysulfides, cannot be used at high ferric iron concentrations or can only be used under single alkaline or acidic conditions.

Description

Technical Field

[0001] The present invention relates to the field of clean gold extraction, in particular to a method for leaching gold from gold-containing materials without cyanide. Background Art

[0002] At present, the gold industry generally uses the cyanide method to extract gold from minerals. The cyanide method for gold dissolution has the advantages of simple process, complete equipment, high gold recovery rate and low cost, but its disadvantages are also prominent: long leaching time, poor selectivity, high toxicity, and the generation of a large amount of cyanide-containing wastewater and waste residue. The wastewater and waste residue treatment costs are high and the process is complicated.

[0003] Currently reported cyanide-free gold extraction reagents include thiosulfate, thiourea, lime sulfur, thiocyanate, halogen, etc. However, problems such as high reagent consumption and harsh process conditions limit their industrial application. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the shortcomings and defects mentioned in the above background art and provide a method for cyanide-free leaching of gold from gold-containing materials, thereby promoting the cyanide-free gold leaching process. Compared with existing gold leaching methods, this method can not only leach gold at high ferric ion concentrations, but also leach gold over a wider solution pH range. This solves the problem that existing reagents such as thiourea and polysulfides cannot be used at high ferric ion concentrations or can only be used under single alkaline or acidic conditions.

[0005] In order to solve the above technical problems, the technical solution proposed by the present invention is:

[0006] A method for leaching gold from a gold-containing material without cyanide comprises the following steps:

[0007] (1) Prepare a gold leaching reagent by mixing formamide or / and ammonium formate with thiourea in a mass ratio of 4 to 10:1;

[0008] (2) placing the gold-containing material in an aqueous solution containing the gold leaching reagent, adding an oxidant, leaching under acidic conditions, and filtering to obtain a gold-containing solution and leaching residue.

[0009] Preferably, during the leaching process, the pH value of the solution is controlled at 1.2 to 9.5.

[0010] Preferably, during the leaching process, the pH value of the solution is controlled at 7 to 9.5.

[0011] Preferably, the oxidant is one of air, oxygen, trivalent iron ions or any combination thereof.

[0012] Preferably, when the oxidant is trivalent iron ions, the amount thereof added is controlled so that the concentration of trivalent iron ions in the solution is not less than 2 g / L; when the oxidant is air or oxygen, the gas flow rate introduced into the solution is controlled to be not less than 40 mL / min.

[0013] Preferably, during the leaching process, the amount of the gold leaching reagent added is 0.1% to 6% of the mass of the gold-containing material, and the leaching temperature is 25 to 70°C.

[0014] Preferably, during the leaching process, the leaching time is 5 to 10 hours.

[0015] Preferably, the solid-liquid ratio g:mL of the aqueous solution of the gold leaching reagent in step (2) is 1:3-4.

[0016] Preferably, during the leaching process, the leaching stirring speed is 200 to 350 r / min.

[0017] Preferably, the gold-containing material comprises the following components: Fe: 20-30wt%, S: 0.2-1.8wt%, As: 1.2-2.2wt%, Cu: 0.16-0.5wt%, Sb: 0.01-0.05wt%, Al: 3.4-5.6wt%; Au: 5-75g / t.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The method for cyanide-free gold leaching of the present invention comprises the following steps: the formamide or ammonium formate or a mixture of formamide and ammonium formate has a synergistic gold extraction effect with thiourea; the formamide or ammonium formate not only has a certain gold leaching ability itself, but also can enhance the stability of thiourea; and the thiourea can increase the gold leaching rate of formamide or ammonium formate, thereby achieving cyanide-free and efficient gold leaching.

[0020] 2. Compared with the existing gold leaching methods, the cyanide-free gold leaching method of the present invention can not only leach gold at a high trivalent iron ion concentration, but also leach gold within a wider solution pH range, thereby solving the problem that existing reagents, such as thiourea and polysulfide, cannot be used at a high trivalent iron ion concentration and can only be used under a single alkaline or acidic condition. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1This is the phase analysis of the gold-containing material used in the present invention. DETAILED DESCRIPTION

[0023] To facilitate understanding of the present invention, the present invention will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0024] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of the present invention.

[0025] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0026] The chemical composition of the sulfur-containing refractory gold ore used in the following examples is shown in Table 1, and the phase analysis is shown in Table 1. Figure 1 The gold content of the slag from the traditional cyanide leaching and thiourea leaching processes is still as high as 15g / t or more.

[0027] Table 1 Composition of gold-containing materials (wt%, ω)

[0028]

[0029] Example 1:

[0030] The specific operation of cyanide-free leaching of gold from gold-containing materials of the present invention is as follows: Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0031] 40g of gold-containing material was leached, and 2g (5% of the mass of the gold-containing material) of a cyanide-free gold leaching reagent formed by formamide and thiourea in a mass ratio of 6:1 was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:3, the stirring speed was 300r / min, the pH was adjusted to 1.8, the leaching temperature was 50°C, the trivalent iron ion concentration was 7g / L, and the leaching time was 6h. After leaching, the gold-containing solution and leaching residue were filtered to obtain the gold-containing solution and leaching residue. The leaching residue was dried at 95°C and sent for testing. The gold leaching rate in the gold-containing material was 86.22%, and the thiourea loss rate was 12.8%.

[0032] Example 2:

[0033] The specific operation of cyanide-free leaching of gold from gold-containing materials of the present invention is as follows: Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0034] 40g of gold-containing material was leached, and 0.5g (1.25% of the mass of the gold-containing material) of a cyanide-free gold leaching reagent formed by formamide and thiourea in a mass ratio of 10:1 was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:4, the stirring speed was 300r / min, the pH was adjusted to 9, the leaching temperature was room temperature, the trivalent iron ion concentration was 7g / L, and the leaching time was 6h. After leaching, the gold-containing solution and leaching residue were filtered to obtain the gold-containing solution and leaching residue. The leaching residue was dried at 95°C and sent for testing. Analysis showed that the gold leaching rate in the gold-containing material was 87.5%, and the thiourea loss rate was 43.7%.

[0035] Example 3:

[0036] The specific operation of cyanide-free leaching of gold from gold-containing materials of the present invention is as follows: Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0037] 40g of gold-containing material was leached, and 1.5g (3.75% of the mass of the gold-containing material) of a cyanide-free gold leaching reagent formed by ammonium formate and thiourea in a mass ratio of 6:1 was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:4, the stirring speed was 350r / min, the pH was adjusted to 9, the leaching temperature was room temperature, the trivalent iron ion concentration was 25g / L, and the leaching time was 5h. After the leaching was completed, the gold-containing solution and leaching residue were filtered to obtain the gold-containing solution and leaching residue. The leaching residue was dried at 95°C and sent for testing. Analysis showed that the gold leaching rate in the gold-containing material was 83.8%, and the thiourea loss rate was 30.8%.

[0038] Example 4:

[0039] The specific operation of cyanide-free leaching of gold from gold-containing materials of the present invention is as follows: Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0040] 40g of gold-containing material was leached, and 1g of a cyanide-free gold leaching reagent (2.5% of the mass of the gold-containing material, with a mass ratio of ammonium formate and ammonium formate of 4:1) was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:4, the stirring speed was 280r / min, the pH was adjusted to 9, the leaching temperature was 40°C, and the leaching time was 9h. Air was bubbled into the solution during the leaching process (50mL / min). After leaching, the gold-containing solution and leaching residue were filtered to obtain the gold-containing solution and leaching residue. The leaching residue was dried at 95°C and sent for testing. Analysis showed that the gold leaching rate in the gold-containing material was 90.4%, and the thiourea loss rate was 37.4%.

[0041] Example 5:

[0042] The specific operation of cyanide-free leaching of gold from gold-containing materials of the present invention is as follows: Figure 1, and the leaching rate of gold in gold-containing materials is tested as follows:

[0043] 40g of gold-containing material was leached, and 2g of a cyanide-free gold leaching reagent (5% of the mass of the gold-containing material, with a mass ratio of ammonium formate and ammonium formate of 4:1) was added to the mixture (ammonium formate + ammonium formate): thiourea at a mass ratio of 10:1. During the leaching process, the solid-liquid ratio (g:mL) was 1:4, the stirring speed was 280r / min, the pH was adjusted to 9, the leaching temperature was room temperature, and the leaching time was 6h. Air was bubbled into the solution during the leaching process (100mL / min). After leaching, the gold-containing solution and leaching residue were filtered to obtain the gold-containing solution and leaching residue, which was then dried at 95°C and sent for testing. Analysis showed that the gold leaching rate in the gold-containing material was 87.7%, and the thiourea loss rate was 30.7%.

[0044] Comparative Example 1:

[0045] The specific operation of cyanide-free leaching of gold from gold-containing materials is shown in the physical analysis of the gold-containing materials used. Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0046] 40g of gold-containing material was leached, and 2g of thiourea was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:3, the stirring speed was 300r / min, the pH was adjusted to 1.8, the leaching temperature was 50°C, the trivalent iron ion concentration was 7g / L, and the leaching time was 6h. After leaching, the gold-containing solution and leaching residue were filtered to obtain the gold-containing solution and leaching residue. The leaching residue was dried at 95°C and sent for testing. The gold leaching rate of the gold-containing material was 38.0%, and the thiourea loss rate was 95.3%.

[0047] Comparative Example 2:

[0048] The specific operation of cyanide-free leaching of gold from gold-containing materials is shown in the physical analysis of the gold-containing materials used. Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0049] 40g of gold-containing material was leached, and 2g of thiourea was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:4, the stirring speed was 300r / min, the pH was adjusted to 9, the leaching temperature was room temperature, the trivalent iron ion concentration was 7g / L, and the leaching time was 6h. After leaching, the gold-containing solution and leaching residue were filtered to obtain the gold-containing solution and leaching residue. The leaching residue was dried at 95°C and sent for testing. The gold leaching rate of the gold-containing material was 10.4%, and the thiourea loss rate was 99.7%.

[0050] Comparative Example 3:

[0051] The specific operation of cyanide-free leaching of gold from gold-containing materials is shown in the physical analysis of the gold-containing materials used. Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0052] 40g of gold-containing material was leached, and 2g of formamide was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:3, the stirring speed was 300r / min, the pH was adjusted to 1.8, the leaching temperature was 50°C, the trivalent iron ion concentration was 7g / L, and the leaching time was 6h. After leaching, the gold-containing solution and leaching residue were filtered to obtain the gold-containing solution and leaching residue. The leaching residue was dried at 95°C and tested. The gold leaching rate of the gold-containing material was 67.9%.

[0053] Comparative Example 4:

[0054] The specific operation of cyanide-free leaching of gold from gold-containing materials is shown in the physical analysis of the gold-containing materials used. Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0055] 40g of gold-containing material was leached, and 2g of formamide was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:4, the stirring speed was 300r / min, the pH was adjusted to 9, the leaching temperature was room temperature, the trivalent iron ion concentration was 7g / L, and the leaching time was 6h. After leaching, the gold-containing solution and leaching residue were filtered, and the leaching residue was dried at 95°C and tested. The gold leaching rate of the gold-containing material was 72.9%.

[0056] Comparative Example 5:

[0057] The specific operation of cyanide-free leaching of gold from gold-containing materials is shown in the physical analysis of the gold-containing materials used. Figure 1 , and the leaching rate of gold in gold-containing materials is tested as follows:

[0058] 40g of gold-bearing material was leached, and 2g of ammonium formate was added. During the leaching process, the solid-liquid ratio (g:mL) was 1:3, the stirring speed was 300r / min, the pH was adjusted to 1.8, the leaching temperature was 50°C, the ferric ion concentration was 7g / L, and the leaching time was 6h. After leaching, the gold-bearing solution and leaching residue were filtered, and the leaching residue was dried at 95°C and tested. The gold leaching rate of the gold-bearing material was 57.1%.

Claims

1. A method for leaching gold from gold-containing materials without cyanide, characterized in that: The steps include: (1) Prepare a gold leaching reagent by mixing formamide or / and ammonium formate with thiourea in a mass ratio of 4 to 10:1; (2) placing the gold-containing material in an aqueous solution containing the gold leaching reagent, adding an oxidant for leaching, controlling the pH value of the solution at 1.2 to 9.5 during the leaching process, and obtaining a gold-containing solution and leaching residue after filtration.

2. The method for leaching gold from gold-containing materials without cyanide according to claim 1, characterized in that: During the leaching process, the pH value of the solution is controlled at 7 to 9.

5.

3. The method for leaching gold from gold-containing materials without cyanide according to claim 1, characterized in that: The oxidant is one of air, oxygen, trivalent iron ions or any combination thereof.

4. The method for leaching gold from a gold-containing material without cyanide according to claim 3, characterized in that: When the oxidant is trivalent iron ions, the amount of the oxidant added is controlled so that the concentration of trivalent iron ions in the solution is not less than 2 g / L; when the oxidant is air or oxygen, the gas flow rate into the solution is controlled to be not less than 40 mL / min.

5. The method for leaching gold from gold-containing materials without cyanide according to claim 1, characterized in that: During the leaching process, the amount of the gold leaching reagent added is 0.1% to 6% of the mass of the gold-containing material, and the leaching temperature is 25 to 70°C.

6. The method for leaching gold from gold-containing materials without cyanide according to claim 1, characterized in that: During the leaching process, the leaching time is 5 to 10 hours.

7. The method for leaching gold from gold-containing materials without cyanide according to claim 1, characterized in that: The solid-liquid ratio g:mL of the aqueous solution of the gold leaching reagent in step (2) is 1:3-4.

8. The method for leaching gold from gold-containing materials without cyanide according to claim 1, characterized in that: During the leaching process, the leaching stirring speed is 200-350 r / min.

9. The method for leaching gold from a gold-containing material without cyanide according to any one of claims 1 to 8, characterized in that: The gold-containing material comprises the following components: Fe: 20-30wt%, S: 0.2-1.8wt%, As: 1.2-2.2wt%, Cu: 0.16-0.5wt%, Sb: 0.01-0.05wt%, Al: 3.4-5.6wt%; Au:5-75g / t.

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