A method for recovering precious metals from thiosulfate leachate based on fixed pore material

Abstract

This invention discloses a method for recovering precious metals from thiosulfate leachate based on a porous material. The method includes the following steps: grinding precious metal-containing ore in a thiosulfate solution; leaching the ground slurry to obtain a precious metal leachate; using the precious metal leachate as an electrolyte, placing the electrolyte in an electrolytic cell, and performing electrolysis using an electrode system within the electrolytic cell, causing the precious metal to deposit on an electrode plate; collecting the deposited elemental precious metal on the electrode plate; the electrode plate includes a substrate and a porous material disposed on the surface of the substrate. This invention uses a porous material as an electrode, utilizing the characteristics of the porous material combined with an electrochemical reduction method to achieve the recovery of specific precious metal complex ions from thiosulfate leachate through specific pores. This achieves integrated targeted adsorption and reduction, enabling efficient recovery of target ions even in the presence of impurity ions, with a recovery efficiency tens of times higher than traditional electrodeposition methods.

Description

Technical Field

[0001] This invention relates to the field of precious metal recovery technology, and specifically to a method for recovering precious metals from thiosulfate leachate based on a fixed-pore material. Background Technology

[0002] Thiosulfate extraction of gold is currently the most promising cyanide-free gold extraction technology for industrial application. It boasts advantages such as rapid leaching, being environmentally friendly and non-toxic, and having strong adaptability to various ores. However, its industrial application is limited by the technical bottleneck of recovering gold complex ions from the leachate. Traditional adsorption methods, such as activated carbon, have poor adsorption capacity for gold complex ions; displacement methods easily cause secondary pollution; solution extraction methods cause serious environmental pollution; and electrodeposition methods are difficult to recover low-concentration gold complex ions. Recently, research has shown that using activated carbon as an electrode material under the assistance of an electric field can achieve the enrichment and recovery of gold complex ions, shortening the traditional three steps of adsorption, desorption, and electrodeposition. However, in actual leachates, multiple competing ions exist, which can easily affect the adsorption and reduction efficiency of gold complex ions, resulting in a decrease in recovery efficiency.

[0003] Therefore, in order to promote the further industrial application of thiosulfate, it is urgent to propose new strategies to reduce the interference of competing ions, thereby achieving efficient recovery of precious metals from low-concentration thiosulfate leachates. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for recovering precious metals from thiosulfate leachates based on pore-fixed materials, thereby solving the current problem of the difficulty in achieving efficient recovery of low-concentration precious metals from thiosulfate leachates.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for recovering precious metals from thiosulfate leachate based on a fixed-pore material, comprising the following steps:

[0007] S1. The precious metal-containing ore is ground in a thiosulfate solution, and the ground slurry is leached to obtain a precious metal leachate.

[0008] S2. Using precious metal leaching solution as electrolyte, the electrolyte is placed in an electrolytic cell, and an electrode system located in the electrolytic cell is used to perform electrolysis, so that the precious metal is deposited on the electrode plate.

[0009] S3. Collect the noble metal elements deposited on the electrode plates;

[0010] The electrode plate includes a substrate and a fixed hole material disposed on the surface of the substrate.

[0011] Preferably, the precious metal is gold or silver.

[0012] Preferably, the pore-fixing material is a pore-fixing carbon material.

[0013] Preferably, the method for preparing the porous carbon material is a physical or chemical activation method.

[0014] Preferably, the preparation method of the pore-fixed activated carbon material includes: crushing and sieving walnut shells and then calcining them at a high temperature to obtain carbonized products; mixing and grinding the carbonized products with potassium hydroxide, calcining them at a high temperature a second time, and then washing and drying them to obtain pore-fixed activated carbon material.

[0015] Preferably, the concentration of precious metal ions in the precious metal leachate is at the ppm or ppb level.

[0016] Preferably, step S2 adjusts the precious metal leachate to be alkaline.

[0017] Preferably, the precious metal is gold; the temperature of the first high-temperature calcination is 400°C, and the temperature of the second high-temperature calcination is 700°C.

[0018] Preferably, the voltage of the electrolysis is 0.4 to 1.6V.

[0019] Preferably, the electrolysis time is 22 to 24 hours.

[0020] The beneficial effects of this invention are:

[0021] This invention uses a porous material as an electrode and leverages its properties in conjunction with an electrochemical reduction method to recover specific noble metal complex ions from thiosulfate leachates through specific pores, achieving integrated targeted adsorption and reduction. This invention is better suited for the recovery of low-concentration noble metals from thiosulfate leachates, enabling efficient recovery of target ions even in the presence of impurity ions, with a recovery efficiency tens of times higher than traditional electrodeposition methods. Attached Figure Description

[0022] Figure 1 These are pore size distribution diagrams of the fixed-pore activated carbon material in Example 1 and the non-fixed-pore activated carbon material in Comparative Example 2;

[0023] Figure 2 These are diagrams illustrating the gold recovery effects in Examples 2-5;

[0024] Figure 3 These are graphs showing the gold recovery effect in the actual leachate of Example 6 and Comparative Example 7;

[0025] Figure 4 This is a diagram showing the gold recovery effect in proportions 3 to 6. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0027] The inventors recognized that existing recovery methods are insufficient for extracting low concentrations of precious metals from thiosulfate leaching solutions. Therefore, developing efficient and pollution-free enrichment technologies for low-concentration precious metal resources is crucial. Consequently, this invention designs a fixed-pore material and combines it with an electrochemical reduction method to simultaneously enrich and reduce precious metal ions in complex leaching systems, achieving the recovery of specific precious metal complex ions and simplifying the traditional precious metal ion recovery process.

[0028] Specifically, this invention proposes a method for recovering precious metals from thiosulfate leachate based on a fixed-pore material, comprising the following steps:

[0029] S1. The precious metal-containing ore is ground in a thiosulfate solution, and the ground slurry is leached to obtain a precious metal leachate.

[0030] S2. Using precious metal leaching solution as electrolyte, the electrolyte is placed in an electrolytic cell, and an electrode system located in the electrolytic cell is used to perform electrolysis, so that the precious metal is deposited on the electrode plate.

[0031] S3. Collect the noble metal elements deposited on the electrode plates;

[0032] The electrode system of this invention includes an electrode plate, a wire connected to the electrode plate, and the other end of the wire connected to an external power source. The electrode plate includes a substrate and a fixed-hole material disposed on the surface of the substrate. The substrate is a metal-based or carbon-based electrode plate, such as a titanium plate, platinum plate, stainless steel plate, or nickel foam plate.

[0033] Furthermore, in some embodiments, the pore-fixing material is a pore-fixing carbon material, such as pore-fixing activated carbon material, pore-fixing graphite material, pore-fixing graphene material, etc.

[0034] Furthermore, in some embodiments, the pore-fixing material is a pore-fixing activated carbon material.

[0035] Furthermore, in some embodiments, the method for preparing the pore-fixed activated carbon material is a physical or chemical activation method, such as acid or alkali vapor activation.

[0036] Furthermore, in some embodiments, the method for preparing the fixed-pore activated carbon material includes:

[0037] The walnut shells are crushed, sieved, and then calcined at high temperature to obtain carbonized products.

[0038] The carbonization product is mixed and ground with potassium hydroxide, then subjected to a second high-temperature calcination, washed and dried to obtain a porous activated carbon material.

[0039] Furthermore, in some embodiments, when the precious metal is gold, the preparation method of the pore-fixed activated carbon material includes: crushing and sieving walnut shells, then calcining them at 400°C to obtain carbonized products; mixing and grinding the carbonized products with potassium hydroxide, then calcining them at 700°C to obtain pore-fixed activated carbon material after washing and drying.

[0040] Furthermore, in some embodiments, the concentration of noble metal ions in the noble metal leachate is trace or micro-level, i.e., in the ppm (mg / L) or ppb (μg / L) range. The concentration of noble metal ions in the noble metal leachate includes, but is not limited to, 0.01–100 mg / L, more preferably 1–10 mg / L; for example, it can be 0.01 mg / L, 1 mg / L, 5 mg / L, 10 mg / L, etc.

[0041] Furthermore, in some embodiments, step S2 adjusts the precious metal leachate to be alkaline. In some preferred embodiments, step S2 adjusts the pH of the precious metal leachate to 8-12.

[0042] Furthermore, in some embodiments, the electrolysis voltage is ≥0.4V, preferably 0.4-1.6V; for example, it can be 0.4V, 0.5V, 0.8V, 1.0V, 1.2V, 1.4V, 1.6V, etc. The electrolysis time is 22-24 hours.

[0043] The present invention will now be described in detail with reference to specific embodiments.

[0044] Example 1

[0045] A method for recovering precious metals from thiosulfate leachate based on a fixed-pore material includes the following steps:

[0046] A gold thiosulfate analog solution was prepared using gold standard solution and ammonium thiosulfate, with a gold concentration of 5 mg / L.

[0047] Walnut shells were crushed and sieved to obtain a powder product, which was calcined at 400℃ for 1 hour in a tube furnace under a nitrogen atmosphere. After cooling, it was washed with ethanol and water, and then freeze-dried to obtain a carbonized product. The carbonized product was then ground and mixed with potassium hydroxide in a 1:3 ratio, calcined at 700℃ for 2 hours under a nitrogen atmosphere, washed with hydrochloric acid and water, and then freeze-dried to obtain a porous activated carbon material. The pore size distribution of this porous activated carbon material is as follows: Figure 1 As shown, the pore volume of a pore with a diameter of 2.42 nm is approximately 0.11 mL / g.

[0048] A slurry was prepared by mixing and grinding pore-fixing activated carbon material with conductive carbon black and polyvinylidene fluoride in a ratio of 8:1:1. The slurry was then coated onto the surface of a titanium plate and dried to obtain an electrode plate.

[0049] The pH of the gold thiosulfate simulation solution was adjusted to 10.00 and then poured into an electrolytic cell. Two electrode plates coated with porous activated carbon were inserted into the solution, with the coated sides facing each other. The two electrode plates were connected to the positive and negative terminals of a DC power supply via wires. After adjusting the power supply voltage to 1.2V, a peristaltic pump was turned on to circulate the aqueous solution. After 22 hours of electrolysis, a sample was taken from the solution and filtered to remove the sparingly soluble solids. The concentration of gold in the filtrate was determined by atomic absorption spectrometry, and the gold recovery rate was calculated to be 96.8%.

[0050] Example 2

[0051] A method for recovering precious metals from thiosulfate leachate based on a fixed-pore material includes the following steps:

[0052] Cu was prepared using gold standard solution, copper standard solution, and ammonium thiosulfate. 2+ The gold thiosulfate is a gold simulation solution containing coexisting impurity metal ions, wherein the gold concentration is 5 mg / L.

[0053] Walnut shells were crushed and sieved to obtain powdered products. The powdered products were calcined at 400°C for 1 hour in a tube furnace under a nitrogen atmosphere. After cooling, the powdered products were washed with ethanol and water and then freeze-dried to obtain carbonized products. The carbonized products were then ground and mixed with potassium hydroxide in a 1:3 ratio and calcined at 700°C for 2 hours under a nitrogen atmosphere. The mixture was then washed with hydrochloric acid and water and freeze-dried to obtain pore-fixed activated carbon materials.

[0054] A slurry was prepared by mixing and grinding pore-fixing activated carbon material with conductive carbon black and polyvinylidene fluoride in a ratio of 8:1:1. The slurry was then coated onto the surface of a titanium plate and dried to obtain an electrode plate.

[0055] The pH of the gold thiosulfate simulation solution was adjusted to 10.00 and then poured into an electrolytic cell. Two electrode plates coated with porous activated carbon were inserted into the solution, with the coated sides facing each other. The two electrode plates were connected to the positive and negative terminals of a DC power supply via wires. After adjusting the power supply voltage to 1.2V, a peristaltic pump was turned on to circulate the aqueous solution. After 22 hours of electrolysis, a sample was taken from the solution and filtered to remove the sparingly soluble solids. The concentration of gold in the filtrate was determined by atomic absorption spectrometry, and the gold recovery rate was calculated to be 98.6%.

[0056] Example 3

[0057] A method for recovering precious metals from thiosulfate leachate based on a fixed-pore material includes the following steps:

[0058] Ni was prepared using gold standard solution, nickel standard solution and ammonium thiosulfate. 2+ The gold thiosulfate is a gold simulation solution containing coexisting impurity metal ions, wherein the gold concentration is 5 mg / L.

[0059] Walnut shells were crushed and sieved to obtain powdered products. The powdered products were calcined at 400°C for 1 hour in a tube furnace under a nitrogen atmosphere. After cooling, the powdered products were washed with ethanol and water and then freeze-dried to obtain carbonized products. The carbonized products were then ground and mixed with potassium hydroxide in a 1:3 ratio and calcined at 700°C for 2 hours under a nitrogen atmosphere. The mixture was then washed with hydrochloric acid and water and freeze-dried to obtain pore-fixed activated carbon materials.

[0060] A slurry was prepared by mixing and grinding pore-fixing activated carbon material with conductive carbon black and polyvinylidene fluoride in a ratio of 8:1:1. The slurry was then coated onto the surface of a titanium plate and dried to obtain an electrode plate.

[0061] The pH of the gold thiosulfate simulation solution was adjusted to 10.00 and then poured into an electrolytic cell. Two electrode plates coated with porous activated carbon were inserted into the solution, with the coated sides facing each other. The two electrode plates were connected to the positive and negative terminals of a DC power supply via wires. After adjusting the power supply voltage to 1.2V, a peristaltic pump was turned on to circulate the aqueous solution. After 22 hours of electrolysis, a sample was taken from the solution and filtered to remove the sparingly soluble solids. The concentration of gold in the filtrate was determined by atomic absorption spectrometry, and the gold recovery rate was calculated to be 91.2%.

[0062] Example 4

[0063] A method for recovering precious metals from thiosulfate leachate based on a fixed-pore material includes the following steps:

[0064] Al was prepared using gold standard solution, aluminum standard solution, and ammonium thiosulfate. 3+ The gold thiosulfate is a gold simulation solution containing coexisting impurity metal ions, wherein the gold concentration is 5 mg / L.

[0065] Walnut shells were crushed and sieved to obtain powdered products. The powdered products were calcined at 400°C for 1 hour in a tube furnace under a nitrogen atmosphere. After cooling, the powdered products were washed with ethanol and water and then freeze-dried to obtain carbonized products. The carbonized products were then ground and mixed with potassium hydroxide in a 1:3 ratio and calcined at 700°C for 2 hours under a nitrogen atmosphere. The mixture was then washed with hydrochloric acid and water and freeze-dried to obtain pore-fixed activated carbon materials.

[0066] A slurry was prepared by mixing and grinding pore-fixing activated carbon material with conductive carbon black and polyvinylidene fluoride in a ratio of 8:1:1. The slurry was then coated onto the surface of a titanium plate and dried to obtain an electrode plate.

[0067] The pH of the gold thiosulfate simulation solution was adjusted to 10.00 and then poured into an electrolytic cell. Two electrode plates coated with porous activated carbon were inserted into the solution, with the coated sides facing each other. The two electrode plates were connected to the positive and negative terminals of a DC power supply via wires. After adjusting the power supply voltage to 1.2V, a peristaltic pump was turned on to circulate the aqueous solution. After 22 hours of electrolysis, a sample was taken from the solution and filtered to remove the sparingly soluble solids. The concentration of gold in the filtrate was determined by atomic absorption spectrometry, and the gold recovery rate was calculated to be 98.9%.

[0068] Example 5

[0069] A method for recovering precious metals from thiosulfate leachate based on a fixed-pore material includes the following steps:

[0070] Pb was prepared using gold standard solution, lead standard solution and ammonium thiosulfate. 2+ The gold thiosulfate is a gold simulation solution containing coexisting impurity metal ions, wherein the gold concentration is 5 mg / L.

[0071] Walnut shells were crushed and sieved to obtain powdered products. The powdered products were calcined at 400°C for 1 hour in a tube furnace under a nitrogen atmosphere. After cooling, the powdered products were washed with ethanol and water and then freeze-dried to obtain carbonized products. The carbonized products were then ground and mixed with potassium hydroxide in a 1:3 ratio and calcined at 700°C for 2 hours under a nitrogen atmosphere. The mixture was then washed with hydrochloric acid and water and freeze-dried to obtain pore-fixed activated carbon materials.

[0072] A slurry was prepared by mixing and grinding pore-fixing activated carbon material with conductive carbon black and polyvinylidene fluoride in a ratio of 8:1:1. The slurry was then coated onto the surface of a titanium plate and dried to obtain an electrode plate.

[0073] The pH of the gold thiosulfate simulation solution was adjusted to 10.00 and then poured into an electrolytic cell. Two electrode plates coated with porous activated carbon were inserted into the solution, with the coated sides facing each other. The two electrode plates were connected to the positive and negative terminals of a DC power supply via wires. After adjusting the power supply voltage to 1.2V, a peristaltic pump was turned on to circulate the aqueous solution. After 22 hours of electrolysis, a sample was taken from the solution and filtered to remove the sparingly soluble solids. The concentration of gold in the filtrate was determined by atomic absorption spectrometry, and the gold recovery rate was calculated to be 98.2%.

[0074] Example 6

[0075] A method for recovering precious metals from thiosulfate leachate based on a fixed-pore material includes the following steps:

[0076] Gold ore from a mineral processing plant was selected and ground in a solution containing ammonium thiosulfate, ammonium sulfite, and ammonia. The ground slurry was then sent to a leaching unit, where an appropriate amount of water was added to control the slurry concentration. The temperature was maintained at 50°C, and the leaching process was carried out with stirring for 10 hours. Testing revealed that the gold concentration in the leachate was 9.8 mg / L.

[0077] Walnut shells were crushed and sieved to obtain powdered products. The powdered products were calcined at 400°C for 1 hour in a tube furnace under a nitrogen atmosphere. After cooling, the powdered products were washed with ethanol and water and then freeze-dried to obtain carbonized products. The carbonized products were then ground and mixed with potassium hydroxide in a 1:3 ratio and calcined at 700°C for 2 hours under a nitrogen atmosphere. The mixture was then washed with hydrochloric acid and water and freeze-dried to obtain pore-fixed activated carbon materials.

[0078] A slurry was prepared by mixing and grinding pore-fixing activated carbon material with conductive carbon black and polyvinylidene fluoride in a ratio of 8:1:1. The slurry was then coated onto the surface of a titanium plate and dried to obtain an electrode plate.

[0079] The pH of the gold thiosulfate simulation solution was adjusted to 10.00 and then poured into an electrolytic cell. Two electrode plates coated with porous activated carbon were inserted into the solution, with the coated sides facing each other. The two electrode plates were connected to the positive and negative terminals of a DC power supply via wires. After adjusting the power supply voltage to 1.2V, a peristaltic pump was turned on to circulate the aqueous solution. After 22 hours of electrolysis, a sample was taken from the solution and filtered to remove the sparingly soluble solids. The concentration of gold in the filtrate was determined by atomic absorption spectrometry, and the gold recovery rate was calculated to be 99.1%.

[0080] Comparative Example 1

[0081] The precious metal was recovered from the gold thiosulfate simulation solution using a method essentially the same as in Example 1, except that the electrode plate was a titanium plate without a fixed-pore material, and the gold recovery rate was 4.3%.

[0082] Comparative Example 2

[0083] The precious metal was recovered using a method essentially the same as in Example 1, except that the material coated on the electrode plate was a non-porous material. This non-porous material was prepared by crushing and sieving walnut shells to obtain a powder product, calcining it at 400°C for 1 hour in a tube furnace under a nitrogen atmosphere, washing it with ethanol and water after cooling, and then freeze-drying it to obtain a carbonized product. The calculated gold recovery rate was 65%.

[0084] Comparative Example 3

[0085] The method used is basically the same as in Example 2, from Cu 2+ To recover gold from a gold thiosulfate simulation solution containing coexisting impurity metal ions, the difference lies in that the material coated on the electrode plate is a non-porous material. The preparation method of the non-porous material is the same as that of Comparative Example 2, and the results are as follows: Figure 4 As shown, the gold recovery rate was 65.4%.

[0086] Comparative Example 4

[0087] Using essentially the same method as in Example 3, from Ni 2+ To recover gold from a gold thiosulfate simulation solution containing coexisting impurity metal ions, the difference lies in that the material coated on the electrode plate is a non-porous material. The preparation method of the non-porous material is the same as that of Comparative Example 2, and the results are as follows: Figure 4 As shown, the gold recovery rate was 64.9%.

[0088] Comparative Example 5

[0089] Using essentially the same method as in Example 4, from Al 3+ To recover gold from a gold thiosulfate simulation solution containing coexisting impurity metal ions, the difference lies in that the material coated on the electrode plate is a non-porous material. The preparation method of the non-porous material is the same as that of Comparative Example 2, and the results are as follows: Figure 4 As shown, the gold recovery rate was 68.4%.

[0090] Comparative Example 6

[0091] The method used is essentially the same as in Example 5, from Pb 2+ To recover gold from a gold thiosulfate simulation solution containing coexisting impurity metal ions, the difference lies in that the material coated on the electrode plate is a non-porous material. The preparation method of the non-porous material is the same as that of Comparative Example 2, and the results are as follows: Figure 4 As shown, the gold recovery rate was 81.5%.

[0092] Comparative Example 7

[0093] The precious metal was recovered from the gold thiosulfate leaching solution using a method essentially the same as in Example 6, except that the electrode plate was a titanium plate without a pore-fixing material, and the gold recovery rate was 8.5%.

[0094] from Figures 2-4 It can be seen that non-porous materials are not effective in recovering gold thiosulfate when impurity metal ions coexist, while porous materials are significantly more effective in recovering gold thiosulfate than the control group when impurity metal ions coexist, thus achieving "selective recovery". Applying porous materials to recover gold in actual leachate has high practical value.

[0095] It should be noted that all the above embodiments belong to the same inventive concept, and the descriptions of each embodiment have different focuses. Where the description in a particular embodiment is not detailed, please refer to the description in other embodiments.

[0096] The embodiments described above are merely illustrative of implementation methods of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for recovering precious metals from thiosulfate leachate based on a fixed-pore material, characterized in that, The steps include: S1. The ore containing precious metals is ground in a thiosulfate solution, and the ground slurry is leached to obtain a precious metal leachate. The coexisting impurity metal ions in the precious metal leachate include Cu. 2+ Ni 2+ Al 3+ and Pb 2+ At least one of them; S2. Using the precious metal leachate as the electrolyte, the electrolyte is placed in an electrolytic cell, and an electrolysis operation is performed using an electrode system provided in the electrolytic cell, so that the precious metal is deposited on the electrode plate. S3. Collect the noble metal element deposited on the electrode plate; The electrode plate includes a substrate and a fixed-pore material disposed on the surface of the substrate, wherein the precious metal is gold and the fixed-pore material is a fixed-pore activated carbon material. The preparation method of the pore-fixed activated carbon material includes the following steps: crushing and sieving walnut shells, then calcining them at 400°C to obtain carbonized products; mixing and grinding the carbonized products with potassium hydroxide, then calcining them at 700°C to obtain pore-fixed activated carbon material after washing and drying. The preparation method of the electrode plate includes the following steps: mixing and grinding the pore-fixed activated carbon material with conductive carbon black and polyvinylidene fluoride in a ratio of 8:1:1 to obtain a slurry, then coating it on the surface of a titanium plate and drying it to obtain the electrode plate.

2. The method according to claim 1, characterized in that, The concentration of precious metal ions in the precious metal leachate is at the ppm or ppb level.

3. The method according to claim 1, characterized in that, In step S2, the precious metal leachate is adjusted to be alkaline.

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