Operation and end point judgment method for reducing gold in high-selenium chlorination leachate based on ferrite

Abstract

The invention relates to the technical field of hydrometallurgy, and discloses an operation and end point judgment method for reducing gold in a high-selenium chlorination leachate based on ferrite, which comprises the following steps: S1, performing chlorine removal on the high-selenium chlorination leachate; s2, after chlorine removal is finished and the temperature of the high-selenium chlorination leachate is cooled, a ferrite solution is added to the surface of the leachate after chlorine removal, and the reaction potential is monitored; s3, after the reaction endpoint potential drops to a first potential platform, the high-selenium chlorination leachate is rapidly cooled, and coarse gold powder and reduced liquid are obtained through filtering; according to the method, the speed of adding the reducing agent ferrous salt solution into the high-selenium chlorination leaching solution is controlled, the reaction endpoint is judged through potential, gold is reduced firstly, it is avoided that due to excessive ferrous salt, part of selenium, platinum and palladium are reduced, the content of gold in the reduced solution is smaller than 5 mg / L, the reduction rate of gold is larger than 99%, and the reduction rate of selenium, tellurium, platinum and palladium is smaller than 0.05%; and efficient selective separation of gold is realized.

Description

Technical Field

[0001] The invention relates to the technical field of hydrometallurgy, in particular to an operation and endpoint judgment method based on ferrous salt reduction of gold in high-selenium chloride leaching solution. Background Art

[0002] Copper anode mud is a smelting byproduct produced during the copper electrolytic refining process. It is also an important raw material for copper smelting enterprises to comprehensively recover rare and precious metals. The efficient and short-process recovery of gold and silver is the most important economic benefit of anode mud. At present, the main anode mud treatment processes at home and abroad include traditional pyrometallurgical process, combined metallurgical process, Kaldo furnace process, semi-wet process and full wet process.

[0003] The semi-wet process is a relatively mature process for industrial application of high-selenium anode mud. The pre-circuit of selenium is achieved by sulphuric acid roasting and steaming selenium in a rotary kiln, and then gold, platinum, palladium and tellurium are enriched in the chlorinated leaching solution by chlorination leaching. For the chlorinated leaching solution, patent CN201610171265.7 adopts sulfur dioxide to control the potential and step-by-step reduction of the gold separation solution, which can achieve effective separation of gold, platinum, palladium and tellurium. This method has been applied industrially. Patent CN110578059B uses a full wet process with sulfuric acid leaching for copper removal, hydrochloric acid leaching for antimony and bismuth removal, and chlorination leaching for gold separation as the main process to treat high-selenium anode mud. Because selenium is not separated in advance, selenium, tellurium, gold, platinum and palladium are all enriched in the chlorinated leaching solution. In order to avoid the dispersion of gold, a short process and efficient separation of gold have become a top priority. If sulfur dioxide is used as a reducing agent, due to its strong reducing property, while chloroauric acid is reduced to elemental gold, selenious acid is also reduced to elemental selenium in large quantities. While selenium is dispersed, preferential separation of gold cannot be achieved, causing the full wet process to enter a bottleneck stage due to difficulty in preferentially separating gold.

[0004] For the high-selenium chloride leaching solution obtained in patent CN110578059B, patent CN201310477786.1 provides a method for reducing gold with ferrous iron, using soluble ferrous salt as a reducing agent. From the perspective of standard electrode potential, Divalent iron ions can selectively reduce gold while selenium is not reduced. However, in the actual reaction process, improper process control and reaction endpoint control, such as adding ferrous salt solution too quickly, resulting in excessive local concentration, excessive addition of ferrous salt solution, etc., will not only affect the reduction rate of gold, but also cause selenium, platinum and palladium to be reduced to a certain extent in the coarse gold powder. Therefore, ferrous salt is used as a reducing agent. Its operation method and endpoint judgment are of great significance to ensure the reduction rate of gold and improve the quality of coarse gold powder.

[0005] Therefore, we need to propose an operation and endpoint judgment method based on ferrous salt reduction of gold in high-selenium chloride leaching solution. Summary of the invention

[0006] The invention aims to provide an operation and endpoint judgment method for reducing gold in a high-selenium chloride leaching solution by using ferrous salt, wherein the rate at which a reducing agent ferrous salt solution is added to the high-selenium chloride leaching solution is controlled, and the reaction endpoint is judged by potential, and gold is firstly reduced, thereby avoiding partial reduction of selenium, platinum and palladium due to excessive ferrous salt. After the reduction, the gold content in the solution is less than 5 mg / L, the reduction rate of gold is greater than 99%, and the reduction rates of selenium, tellurium, platinum and palladium are less than 0.05%, thereby realizing efficient and selective separation of gold, so as to solve the problems raised in the above-mentioned background technology.

[0007] To achieve the above object, the present invention provides the following technical solution: an operation and endpoint judgment method based on ferrous salt reduction of gold in high-selenium chloride leaching solution, comprising the following steps:

[0008] S1, driving out chlorine from the high-selenium chlorination leaching solution;

[0009] S2, after the chlorine removal is completed and the temperature of the high-selenium chlorination leaching solution is cooled, a ferrous salt solution is added to the surface of the chlorine-removed leaching solution, and the reaction potential is monitored;

[0010] S3. When the reaction endpoint potential drops to the first potential platform, the high-selenium chloride leaching solution is rapidly cooled and filtered to obtain coarse gold powder and reduced solution.

[0011] Preferably, in step S1, the selenium concentration in the high-selenium chloride leaching solution is 20-40 g / L, the tellurium concentration is 8-15 g / L, the gold concentration is 1-2 g / L, the platinum concentration is 0.01-0.015 g / L, and the palladium concentration is 0.04-0.05 g / L.

[0012] Preferably, in step S1, the temperature of the chlorine removal process is controlled at 90-110°C, the potential of the high-selenium chlorination leaching solution before chlorine removal is 900-1100mV, and the temperature of the high-selenium chlorination leaching solution is cooled to 40-60°C after chlorine removal, and the potential of the high-selenium chlorination leaching solution after cooling is 600-800mV.

[0013] Preferably, in step S2, in order to ensure that the subsequently added ferrous salt solution can react stably and avoid decomposition or unnecessary chemical reactions caused by high temperature, the high-selenium chloride leachate needs to be cooled. The ferrous salt solution is added from the surface of the high-selenium chloride leachate through a guide tube to avoid high concentration of local ferrous salt solution in the high-selenium chloride leachate or violent reaction.

[0014] Preferably, in step S2, the concentration of ferrous ions in the ferrous salt solution is 10-30 g / L. To control the speed of the reaction, the addition rate of the ferrous salt solution is 2-5 mL / min to ensure that the reaction proceeds smoothly and evenly.

[0015] Preferably, in step S2, after the temperature of the high-selenium chloride leaching solution is cooled to 40-60°C, the process potential monitoring uses an ORP composite electrode to continuously measure the potential of the high-selenium chloride leaching solution and draw a potential change curve.

[0016] Preferably, in step S3, the first potential platform is the potential platform where the potential first reaches stability after the reaction starts with the addition of the ferrous salt solution and the potential drops from 700-800 mV to 520-560 mV. At the first potential platform, Au is reduced and other elements are not reduced.

[0017] Preferably, in step S3, after the reaction endpoint potential drops to the first potential platform, the high-selenium chlorination leaching solution is rapidly cooled to a temperature below 35° C., solid-liquid separation is performed, and coarse gold powder and reduced liquid are obtained by filtration.

[0018] Preferably, in step S3, after the first potential platform appears, as the ferrous salt solution continues to be added, the potential further drops to 420-460 mV and a second potential platform appears, and as the ferrous salt solution continues to be added, the potential platform remains unchanged for a long time, and at the second potential platform, Au and other elements are reduced.

[0019] Preferably, in step S3, a filtering device is used to separate the coarse gold powder and the reduced liquid, the coarse gold powder is retained on the filtering device, and the coarse gold powder is dried and purified to remove the solution and impurities contained in the coarse gold powder.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention controls the rate at which a ferrous salt solution as a reducing agent is added to a high-selenium chloride leaching solution, determines the reaction end point by electric potential, reduces gold first, and avoids partial reduction of selenium, platinum and palladium due to excessive ferrous salt. After the reduction, the gold content in the solution is less than 5 mg / L, the gold reduction rate is greater than 99%, and the selenium, tellurium, platinum and palladium reduction rates are less than 0.05%, thereby realizing efficient selective separation of gold. The reaction process has a high controllability, a small amount of the ferrous salt solution as a reducing agent is used, and the selective reduction of gold is efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a flowchart of the present invention;

[0023] Figure 2 It is a potential trend diagram of the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in 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.

[0025] Example 1

[0026] See also Figure 1-2 The present invention provides a technical solution: an operation and endpoint judgment method based on ferrous salt reduction of gold in high-selenium chloride leaching solution, comprising the following steps:

[0027] S1, driving out chlorine from the high-selenium chlorination leaching solution, removing chlorine from the high-selenium chlorination leaching solution, the presence of chlorine may affect the separation and extraction of other elements in the leaching solution, so it is necessary to remove it through the chlorination driving step;

[0028] In step S1, the time for driving out chlorine is controlled at 1-3h, the concentration of selenium in the high-selenium chlorination leaching solution is 20-40g / L, the concentration of tellurium is 8-15g / L, the concentration of gold is 1-2g / L, the concentration of platinum is 0.01-0.015g / L, and the concentration of palladium is 0.04-0.05g / L.

[0029] In step S1, the temperature of the chlorine removal process is controlled at 90-110°C, the potential of the high-selenium chlorination leaching solution before chlorine removal is 900-1100mV, and the temperature of the high-selenium chlorination leaching solution is cooled to 40-60°C after chlorine removal (distilled water is added in time during the cooling process to maintain the volume of the high-selenium chlorination leaching solution), and the potential of the high-selenium chlorination leaching solution after cooling is 600-800mV.

[0030] S2, after the chlorine removal is completed and the temperature of the high-selenium chlorination leaching solution is cooled, a ferrous salt solution is added to the surface of the chlorine-removed leaching solution, and the reaction potential is monitored;

[0031] After removing the chlorine, the temperature of the solution may be high and needs to be cooled to a temperature suitable for subsequent processing. The purpose of cooling is to ensure that the subsequently added ferrous salt solution will not decompose due to high temperature or undergo unnecessary chemical reactions. The ferrous salt solution is added to reduce the metal ions in the solution. The ferrous salt solution is added at a certain rate to ensure that the reaction can proceed smoothly, avoid violent reactions or excessive local concentrations, and help obtain better reaction effects and product quality.

[0032] Potential is a physical quantity that describes the extent of a chemical reaction. By monitoring changes in potential, we can understand the extent of the reaction and whether it has reached the expected endpoint.

[0033] In step S2, in order to ensure that the subsequently added ferrous salt solution can react stably and avoid decomposition or unnecessary chemical reactions caused by high temperature, the high-selenium chloride leachate needs to be cooled. The ferrous salt solution is added from the surface of the high-selenium chloride leachate through a guide tube to avoid high concentration of local ferrous salt solution in the high-selenium chloride leachate or violent reaction.

[0034] In step S2, the concentration of ferrous ions in the ferrous salt solution is 10-30 g / L. To control the speed of the reaction, the addition rate of the ferrous salt solution is 2-5 mL / min to ensure that the reaction proceeds smoothly and evenly.

[0035] In step S2, after the temperature of the high-selenium chloride leaching solution is cooled to 40-60°C, the process potential monitoring uses an ORP composite electrode to continuously measure the potential of the high-selenium chloride leaching solution and draw a potential change curve.

[0036] S3. When the reaction endpoint potential drops to the first potential platform, the high-selenium chloride leaching solution is rapidly cooled and filtered to obtain coarse gold powder and reduced solution.

[0037] When the potential drops to the first potential platform, it means that the reaction has reached the predetermined end point. At this time, the addition of ferrous salt solution should be stopped immediately to avoid overreaction.

[0038] If the solution temperature is moderate or a purer solid product is required, you can choose to cool it down before filtering. Cooling down helps to crystallize or precipitate certain components in the solution, making them easier to separate.

[0039] The coarse gold powder is the solid product obtained by filtration, which may contain the target metal or other impurities, and the reduced liquid is the liquid after filtration, which may contain ions and compounds that have not been reduced or removed.

[0040] In step S3, the first potential platform is the potential platform where the potential reaches stability for the first time after the reaction starts with the addition of the ferrous salt solution and the potential drops from 700-800 mV to 520-560 mV. Under the first potential platform, Au is reduced and other elements are not reduced.

[0041] In step S3, after the reaction endpoint potential drops to the first potential platform, the high-selenium chloride leaching solution is rapidly cooled to a temperature below 35° C., solid-liquid separation is performed, and coarse gold powder and reduced liquid are obtained by filtration.

[0042] In step S3, after the first potential platform appears, with the continued addition of ferrous salt solution, the potential further drops to 420-460 mV and a second potential platform appears. With the continued addition of ferrous salt solution, the potential platform remains unchanged for a long time. At the second potential platform, Au and other elements are reduced.

[0043] In step S3, a filtering device is used to separate the coarse gold powder and the reduced liquid. The coarse gold powder is retained on the filtering device, and the coarse gold powder is dried and purified to remove the solution and impurities contained in the coarse gold powder.

[0044] The main components of high-selenium chlorination leaching solution are shown in the following table:

[0045] Table 1 Main components of high selenium chlorination leaching solution g / L

[0046] element Au Se Te Pt Pd Fe Chlorinated leachate 1.06 39.49 12.48 0.017 0.037 0.06

[0047] Measure 3L of chlorinated leaching solution and pour it into a beaker. Do not heat the solution to remove chlorine. Stir at 300r / min. Insert the potentiometer into the solution and fix it. When the potential stabilizes, the potential is 1030mV. Then add Fe at 3mL / min through a peristaltic pump. 2+ The ion concentration of ferrous sulfate heptahydrate solution is 20 g / L. When the potential drops to 650 mV and remains stable, it is immediately filtered while hot to obtain the reduced residue and reduced liquid. The experimental results are shown in Table 2.

[0048] Table 2 Experimental results of Example 1

[0049] element Au Se Te Pt Pd Fe Chlorinated leaching solution g / L 1.06 39.49 12.48 0.017 0.037 0.06 Reduction liquid g / L 0.047 39.47 12.48 0.017 0.037 6.47 Reduction rate % 95.57 0.05 0 0 0 ——

[0050] Note: In the experimental results, <0.005g / L is the lower limit of ICP test, and the reduction rate is calculated based on 0.005g / L.

[0051] Example 2

[0052] The same as Example 1 is not repeated here, the difference is

[0053] Measure 3L of chlorinated leaching solution and pour it into a beaker. Place the beaker in a constant temperature water bath and adjust the temperature to 100℃. After removing the chlorine for 2 hours, cool the solution to 60℃ at room temperature or water cooling conditions. (During the process, add distilled water in time to a volume slightly lower than the initial volume of the solution, and add the volume to the initial volume after the reaction is completed)

[0054] Stirring at 300 r / min, insert the potentiometer into the solution and fix it. When the potential stabilizes, the potential is 683 mV. Then, Fe is added at 10 mL / min by a peristaltic pump. 2+ The ion concentration is 20g / L ferrous sulfate heptahydrate solution. When the potential changes from rapid decline to stability, the potential is 564mV. After rapid cooling to 35°C, the reduced slag and reduced liquid are obtained by filtration. The experimental results are shown in Table 3.

[0055] Table 3 Experimental results of Example 2

[0056] element Au Se Te Pt Pd Fe Chlorinated leaching solution g / L 1.06 39.49 12.48 0.017 0.037 0.06 Reduction liquid g / L <0.005 33.41 10.52 0.01 0.03 2.94 Reduction rate % 99.53 15.39 15.69 33.45 23.55 ——

[0057] Example 3

[0058] The same as the above embodiment will not be repeated, the difference is

[0059] Measure 3L of chlorinated leaching solution and pour it into a beaker. Place the beaker in a constant temperature water bath and adjust the temperature to 100℃. After removing the chlorine for 2 hours, cool the solution to 60℃ at room temperature or water cooling conditions. (During the process, add distilled water in time to a volume slightly lower than the initial volume of the solution, and add the volume to the initial volume after the reaction is completed)

[0060] Stirring at 300 r / min, insert the potentiometer into the solution and fix it. When the potential stabilizes, the potential is 668 mV. Then, Fe is added at 3 mL / min by a peristaltic pump. 2+ The ion concentration is 20 g / L ferrous sulfate heptahydrate solution. When the potential changes from rapid decline to stability, the potential is 533 mV. After rapid cooling to 35°C, the reduced slag and reduced liquid are obtained by filtration. The experimental results are shown in Table 4.

[0061] Table 4 Experimental results of Example 3

[0062] element Au Se Te Pt Pd Fe Chlorinated leaching solution g / L 1.06 39.49 12.48 0.017 0.037 0.06 Reduction liquid g / L <0.005 39.45 12.47 0.017 0.037 2.14 Reduction rate % 99.53 0.1 0.08 0 0 ——

[0063] Example 4

[0064] The same as the above embodiment will not be repeated, the difference is

[0065] Measure 3L of chlorinated leaching solution and pour it into a beaker. Place the beaker in a constant temperature water bath and adjust the temperature to 100℃. After removing the chlorine for 2 hours, cool the solution to 60℃ at room temperature or water cooling conditions. (During the process, add distilled water in time to a volume slightly lower than the initial volume of the solution, and add the volume to the initial volume after the reaction is completed)

[0066] Stirring at 300 r / min, the amount of ferrous sulfate added was 10 times the theoretical value of reducing chloroauric acid, and Fe was added at 3 mL / min by a peristaltic pump. 2+ The ion concentration was 20 g / L ferrous sulfate heptahydrate solution. The potential was not controlled during the process. The monitored endpoint potential was 436 mV. After the ferrous sulfate was added, it was rapidly cooled to 35°C and then filtered to obtain the reduced slag and reduced liquid. The experimental results are shown in Table 5.

[0067] Table 5 Experimental results of Example 4

[0068] element Au Se Te Pt Pd Fe Chlorinated leaching solution g / L 1.06 39.49 12.48 0.017 0.037 0.06 Reduction liquid g / L <0.005 30.90 12.47 0.017 0.025 5.19 Reduction rate % 99.53 21.74 0 0 32.26 ——

[0069] Example 5

[0070] The same as the above embodiment will not be repeated, the difference is

[0071] Measure 3L of chlorinated leaching solution and pour it into a beaker. Place the beaker in a constant temperature water bath and adjust the temperature to 100℃. After removing the chlorine for 2 hours, cool the solution to 60℃ at room temperature or water cooling conditions. (During the process, add distilled water in time to a volume slightly lower than the initial volume of the solution, and add the volume to the initial volume after the reaction is completed)

[0072] Stirring at 300 r / min, insert the potentiometer into the solution and fix it. When the potential stabilizes, the potential is 677 mV. Then, Fe is added at 3 mL / min by a peristaltic pump. 2+ The ion concentration is 20g / L ferrous sulfate heptahydrate solution. When the potential changes from rapid decline to stability, the potential is 556mV, and the addition of ferrous sulfate is stopped. The reaction is continued for 30min, and the reduced slag and reduced liquid are obtained by filtration. The experimental results are shown in Table 6.

[0073] Table 5 Experimental results of Example 5

[0074] element Au Se Te Pt Pd Fe Chlorinated leaching solution g / L 1.06 39.49 12.48 0.017 0.037 0.06 Reduction liquid g / L 0.13 39.47 12.48 0.017 0.037 2.07 Reduction rate % 87.74 0.05 0 0 0 ——

[0075] The above experiments show that the reaction endpoint is determined by potential, which avoids the partial reduction of selenium, platinum and palladium due to excessive ferrous salt. The gold content in the solution after reduction is less than 5 mg / L, the gold reduction rate is greater than 99%, and the selenium, tellurium, platinum and palladium reduction rates are less than 0.05%, achieving efficient and selective separation of gold.

[0076] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An operation and endpoint determination method based on ferrous salt reduction of gold in high-selenium chloride leaching solution, characterized in that: The following steps are involved: S1, driving out chlorine from the high-selenium chlorination leaching solution; S2, after the chlorine removal is completed and the temperature of the high-selenium chlorination leaching solution is cooled, a ferrous salt solution is added to the surface of the chlorine-removed leaching solution, and the reaction potential is monitored; S3. When the reaction endpoint potential drops to the first potential platform, the high-selenium chloride leaching solution is rapidly cooled and filtered to obtain coarse gold powder and reduced solution.

2. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 1, characterized in that: In step S1, the selenium concentration in the high-selenium chloride leaching solution is 20-40 g / L, the tellurium concentration is 8-15 g / L, the gold concentration is 1-2 g / L, the platinum concentration is 0.01-0.015 g / L, and the palladium concentration is 0.04-0.05 g / L.

3. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 1, characterized in that: In step S1, the temperature of the chlorine removal process is controlled at 90-110°C, the potential of the high-selenium chlorination leaching solution before chlorine removal is 900-1100mV, and the temperature of the high-selenium chlorination leaching solution is cooled to 40-60°C after chlorine removal, and the potential of the high-selenium chlorination leaching solution after cooling is 600-800mV.

4. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 1, characterized in that: In step S2, in order to ensure that the subsequently added ferrous salt solution can react stably and avoid decomposition or unnecessary chemical reactions caused by high temperature, the high-selenium chloride leachate needs to be cooled. The ferrous salt solution is added from the surface of the high-selenium chloride leachate through a guide tube to avoid high concentration of local ferrous salt solution in the high-selenium chloride leachate or violent reaction.

5. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 4, characterized in that: In step S2, the concentration of ferrous ions in the ferrous salt solution is 10-30 g / L. To control the speed of the reaction, the addition rate of the ferrous salt solution is 2-5 mL / min to ensure that the reaction proceeds smoothly and evenly.

6. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 1, characterized in that: In step S2, after the temperature of the high-selenium chloride leaching solution is cooled to 40-60°C, the process potential monitoring uses an ORP composite electrode to continuously measure the potential of the high-selenium chloride leaching solution and draw a potential change curve.

7. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 1, characterized in that: In step S3, the first potential platform is the potential platform where the potential reaches stability for the first time after the reaction starts with the addition of the ferrous salt solution and the potential drops from 700-800 mV to 520-560 mV. Under the first potential platform, Au is reduced and other elements are not reduced.

8. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 1, characterized in that: In step S3, after the reaction endpoint potential drops to the first potential platform, the high-selenium chloride leaching solution is rapidly cooled to a temperature below 35° C., solid-liquid separation is performed, and coarse gold powder and reduced liquid are obtained by filtration.

9. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 1, characterized in that: In step S3, after the first potential platform appears, with the continued addition of ferrous salt solution, the potential further drops to 420-460 mV and a second potential platform appears. With the continued addition of ferrous salt solution, the potential platform remains unchanged for a long time. At the second potential platform, Au and other elements are reduced.

10. The method for operation and endpoint determination based on ferrous salt reduction of gold in high-selenium chloride leaching solution according to claim 1, characterized in that: In step S3, a filtering device is used to separate the coarse gold powder and the reduced liquid. The coarse gold powder is retained on the filtering device, and the coarse gold powder is dried and purified to remove the solution and impurities contained in the coarse gold powder.

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