A short-process and low-cost continuous and stable gold extraction process by thiocyanate method

Abstract

The present invention discloses a short-process and low-cost continuous and stable gold extraction process by thiosulfate method, belonging to the field of hydrometallurgy. In a closed reactor, by adjusting the concentrations of dissolved O2, thiosulfate and catalyst to a lower level, the pulp potential is decreased to an appropriate range to leach gold ore, and the leached residue and leached pregnant solution are obtained by filtration. Pure nitrogen is introduced into the leached pregnant solution to exhaust the oxygen in the solution, and copper powder is added for displacement. The copper-rich crude copper and the displacement lean solution are obtained by filtration. The copper-rich crude copper is treated by electrolytic refining, pure copper is obtained at the cathode, and gold mud is obtained at the anode. The gold mud is washed with dilute acid to obtain the acid washing solution containing copper and pure gold. After adjusting the pH of the acid washing solution containing copper, it is combined with the displacement lean solution supplemented with the leaching agent for the leaching of fresh ore in the next cycle. The method of the present invention takes into account the problems of long process flow, high cycle cost and great environmental protection pressure of the copper-ammonia-catalyzed thiosulfate method, and is suitable for use in the natural environment.

Description

Technical Field

[0001] The present invention belongs to the field of hydrometallurgy and relates to a process for continuously and stably extracting gold from gold ore. Background Art

[0002] Gold has an extremely low content in the earth's crust and is a national strategic metal with excellent physical and chemical properties, which is widely used in high-tech industries. The cyanidation method is the mainstream technology for extracting gold from gold ore. According to statistics, more than 80% of the world's gold production uses the cyanidation method. However, cyanide is highly toxic. At the same time, the gold leaching rate of this method is slow and the leaching time is long, which is not suitable for treating gold ores containing sulfides, copper and other cyanide-consuming substances, as well as carbonaceous or clay-containing substances that are prone to "robbing gold". Therefore, the gold industry urgently needs to develop non-toxic non-cyanide gold extraction technologies.

[0003] Among the studies on numerous non-cyanide gold extraction technologies, the thiosulfate method is widely regarded as the most promising non-toxic non-cyanide gold extraction method to replace the cyanidation method. Without the action of a catalyst, the gold leaching rate of pure thiosulfate is slow and the gold leaching rate is low. Introducing a copper-ammonia catalytic system can significantly improve the gold leaching ability of thiosulfate. The methods for recovering gold from the copper-ammonia catalytic thiosulfate gold leaching pregnant solution include metal displacement method, activated carbon adsorption method, solvent extraction method, resin adsorption method and electrodeposition method, etc. The metal displacement method has a simple and mature process, but the gold grade of the obtained crude gold product is low, and at the same time, no systematic solution circulation research has been carried out, and the stability of various gold recovery indexes is not clear. The activated carbon adsorption method has a weak adsorption capacity for the Au(S2O3)2 3– complex ion, and the gold recovery rate is low. The solvent extraction method has high requirements for the clarity of the solution and the gold concentration in the leaching pregnant solution. The extractant is expensive and the extractant is an organic reagent, which is prone to form secondary pollution. The electrodeposition method has high requirements for the clarity of the solution, low current efficiency, and difficult solution circulation. The resin adsorption method is widely regarded as the most suitable for recovering gold from the thiosulfate leaching pregnant solution. It has low requirements for the clarity of the solution, and the resin has the advantages of large adsorption capacity and reusable, etc., but Cu(S2O3)3 5– for Au(S2O3)2 3– competitive adsorption results in the need to adopt a complex two-stage desorption process for gold recovery.

[0004] As the prior art, the method of using copper-ammonia catalytic thiosulfate to leach gold and using the resin adsorption method to recover gold from the gold leaching pregnant solution has inherent "three major problems", namely: First, the strong oxidation of Cu(NH3)4 2+ / O2 to S2O3 2– , and the large amount of S2O3 2– usage, etc. lead to a large consumption of thiosulfate reagents. Second, ammonia water is volatile and has certain toxicity, and ammonia threatens the environment. Third, Cu(S2O3)3 5– for resin adsorption of Au(S2O3)23– Competition occurs, leading to a complex gold recovery process. For this reason, scientific researchers have carried out a lot of relevant research work, mainly including the following two aspects. On the one hand, during the copper-ammonium thiosulfate gold leaching process, means of regulating the gold leaching reaction conditions or using additives are adopted to reduce the consumption of thiosulfate. However, during the gold leaching process, the reaction conditions are constantly changing, making it difficult to precisely control them. At the same time, there are great limitations in the selection of additives, and no additive that can be generally applicable to multiple gold ores has emerged. On the other hand, new catalytic systems to replace the copper-ammonia catalytic system are studied, such as copper-citric acid / ethylenediamine, iron-oxalic acid / EDTA / sulfosalicylic acid, nickel / cobalt-ammonia, nickel / cobalt-glycine, etc. However, these catalytic systems either single-substitute copper but still have the problem of ammonia threatening the environment, or single-substitute ammonia but still have the problem of complex gold recovery process, or both copper and ammonia are substituted but the reagents are expensive or toxic. Therefore, the thiosulfate gold extraction technology has not been industrially promoted and applied for a long time.

[0005] The Chinese invention patent application with the publication number CN117947278A discloses "a thiosulfate process for gold extraction". First, it uses a copper-containing catalytic system-thiosulfate solution to leach the gold-containing material to obtain a thiosulfate leaching solution containing precious metals; then, a reducing agent containing S 2- is added to the thiosulfate leaching solution containing precious metals for reaction, and after filtration, a precipitate residue rich in gold and copper and a filtrate containing thiosulfate are obtained; finally, the precipitate residue rich in gold and copper is treated by acidic oxidation leaching to obtain a leaching solution containing copper ions and a gold-containing leaching residue. It claims to solve the problems of large consumption of thiosulfate and difficult gold recovery, and simplifies the gold leaching process. Although the process disclosed in this patent is simple, using a reducing agent containing S 2- to precipitate gold and copper from the thiosulfate leaching solution of precious metals, there are seriously the following two problems:

[0006] (1) The reducing agent containing S 2- is first expensive, and secondly, it is difficult to control the addition amount of the precipitate. If the addition amount is too small, the gold precipitation is not complete, and if the addition amount is too large, the leaching solution will contain too much sulfide ion, resulting in the precipitation of copper ions when adding the catalyst copper ions for the next leaching supplement, and too much catalyst copper ions need to be supplemented, increasing the gold leaching cost.

[0007] (2) Adding S 2- for replacement will incidentally precipitate the catalyst copper ions together to form CuS or CuS2. In his invention, it is mentioned to leach copper with dilute acid, but CuS or CuS2 is insoluble in dilute acid, and it is difficult to separate the precipitated gold and copper subsequently. At the same time, for the copper-containing leaching solution mentioned in its process, the copper content is extremely low. Even if it is returned to the leaching solution for leaching, a large amount of catalyst copper still needs to be supplemented during leaching, which greatly increases the leaching cost.

[0008] In summary, during leaching, the leaching cost remains very high, the actual operation of this process is difficult, and the difficulty in recovery remains a problem. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a short-process and low-cost continuous and stable gold extraction process by the thiosulfate method, to overcome the foregoing defects existing in the prior art, to further reduce the gold extraction cost, shorten the gold extraction process, and improve the stability of various gold extraction indexes.

[0010] The technical solution of the present invention is as follows:

[0011] A short-process and low-cost continuous and stable gold extraction process by the thiosulfate method, comprising the following steps:

[0012] (1) In a closed reactor, by adjusting the dissolved O2, thiosulfate concentration, and copper-ammonia catalyst concentration within a certain range at a relatively low level to lower the pulp potential to an appropriate range for leaching the gold ore, and filtering to obtain leached residue and leached pregnant solution;

[0013] (2) Passing pure nitrogen into the leached pregnant solution to remove oxygen in the solution, and then adding copper powder for displacement, and filtering to obtain copper concentrate rich in gold and displacement barren solution;

[0014] (3) Using electrolytic refining to treat the copper concentrate rich in gold, obtaining pure copper at the cathode and gold mud at the anode;

[0015] (4) Washing the gold mud with dilute acid to obtain acid washing solution containing copper and pure gold;

[0016] The adjustment of the dissolved O2 concentration at a relatively low level means controlling the average dissolved O2 concentration between 0.25 and 0.35 mg / L; the adjustment of the leaching agent thiosulfate at a relatively low level means adjusting the thiosulfate concentration between 0.05 and 0.08 mol / L; the adjustment of the copper-ammonia catalyst concentration at a relatively low level means adjusting the copper sulfate concentration to 0.5 to 1 mmol / L and the ammonia water concentration to 0.4 to 0.8 mol / L; the reduction of the pulp potential to an appropriate range means controlling the pulp potential at 195 to 205 mV.

[0017] Preferably, the thiosulfate refers to one or more of calcium thiosulfate, sodium thiosulfate, and ammonium thiosulfate.

[0018] Preferably, the conditions for leaching the gold ore in step (1) are that the pulp concentration is 25 to 50%, the proportion of the gold ore ground to a particle size of -200 mesh in the whole is more than 90 wt%, during leaching, the reaction temperature is controlled at 25 to 35 °C, the pH value of the reaction system is 9 to 12, the reaction time is 8 to 12 h, and the stirring speed is 200 to 400 r / min.

[0019] Preferably, the dosage of copper powder in step (2) is 300 times the theoretical dosage.

[0020] Preferably, the conditions for electrolytic refining in step (3) are as follows: the electrolyte is one of sulfuric acid or nitric acid, the electrolysis temperature is 25 - 35°C, and the current density is 100 - 230 A / m 2 , and the electrolysis time is 12 - 48 h.

[0021] Preferably, the pure copper refers to pure copper with a purity of 3N or higher; the pure gold refers to pure gold with a purity of 3N or higher; the gold mud obtained from the electrolytic refining anode refers to gold mud with a gold content of 97% or higher.

[0022] Preferably, the acid used for the dilute acid washing in step (4) is one or two of sulfuric acid, nitric acid, and hydrochloric acid; the pickling conditions are as follows: the acid concentration is 0.5 - 2 mol / L, the acid dosage is added according to the solid - liquid ratio of 1:(2 - 3), the pickling time is 1 - 2 h, the pickling temperature is 25 - 100°C, and the stirring speed is 200 - 400 r / min.

[0023] Preferably, in step (2), the flow rate of the pure nitrogen gas introduced is 1 - 3 ml / min; the fineness of the copper powder used is - 200 - +400 mesh.

[0024] Preferably, the replacement lean solution obtained in step (2) is supplemented with thiosulfate, and the copper - containing pickling solution obtained in step (4) is adjusted to a pH of 10, and then the replacement lean solution supplemented with thiosulfate and the pH - adjusted copper - containing pickling solution are combined for use in the leaching of fresh ore in the next cycle.

[0025] More preferably, the thiosulfate supplemented to the replacement lean solution includes one or more of calcium thiosulfate, sodium thiosulfate, and ammonium thiosulfate; the amount of thiosulfate supplemented is such that the concentration of thiosulfate in the leaching solution is supplemented to 0.05 - 0.08 mol / L. During the leaching process, the lower the dissolved oxygen concentration, the weaker the oxidation effect on the leaching agent thiosulfate, and the lower the consumption of thiosulfate. However, the dissolved O2 cannot be too low, otherwise it will affect the gold leaching rate and gold leaching efficiency. Therefore, in the present invention, the average concentration of dissolved O2 is controlled between 0.25 - 0.35 mg / L.

[0026] During the leaching process, when the thiosulfate concentration increases, the gold leaching rate is fast, but the oxidation decomposition products of the leaching agent increase and the consumption increases; when the concentration decreases, the gold leaching efficiency can be improved by appropriately prolonging the leaching time, and the oxidation decomposition products of the leaching agent decrease and the consumption decreases. Therefore, in the present invention, the thiosulfate concentration is adjusted to 0.05 - 0.08 mol / L.

[0027] If the pulp potential is too high, it will lead to an enhanced catalytic oxidation and decomposition effect on thiosulfate, resulting in an increased consumption of thiosulfate; if the pulp potential is too low, it will lead to a slow gold leaching rate and a low gold leaching rate. Therefore, in the present invention, the pulp potential is controlled at 195 - 205 mV.

[0028] Appropriately increasing the ammonia concentration is beneficial to the formation of Cu(NH3)4 2+ Stabilize copper ions and reduce Cu 2+ The oxidation of the leaching agent thiosulfate. In addition, reducing the reagent concentration is beneficial to reducing the reagent cost. Therefore, in the present invention, the concentration of copper sulfate is adjusted to 0.5 - 1 mmol / L, and the concentration of ammonia water is adjusted to 0.4 - 0.8 mol / L.

[0029] During the reaction process of the present invention, no oxygen is supplemented into the closed reaction kettle, and only the air and pulp dissolved oxygen in the reaction kettle at the initial stage can meet the oxygen required for the gold leaching process. By controlling the low dissolved oxygen concentration of the pulp, the consumption of the leaching agent thiosulfate is reduced.

[0030] The dosage of copper powder needs to be excessive, otherwise the replacement is not sufficient. The possible reasons are: on the one hand, there are other metal ions in the solution that can be replaced by copper powder besides gold; on the other hand, the metal replaced by copper powder in the solution covers the surface of the copper powder, forming a passivation film, which hinders the replacement of copper powder. Therefore, in the present invention, the dosage is 300 times the theoretical dosage (copper and gold are replaced in a ratio of 1:2). The dosage of copper powder is greatly increased to ensure that the gold is completely replaced.

[0031] If the dosage of acid is too small, the copper leaching rate in the gold mud is relatively low and the copper is not completely leached; if the dosage of acid is too large, the cost of acid is too high, and at the same time, a large amount of alkali needs to be added to adjust the pH value in order to be combined with the precious liquid of the second-stage leaching and returned for use, resulting in a large consumption of alkali. Therefore, in the present invention, the acid concentration is controlled at 0.5 - 2 mol / L.

[0032] Compared with the prior art, the advantages of the present invention are as follows:

[0033] First, in the thiosulfate process for gold extraction of the present invention, the gold extraction cost is significantly reduced. First, when using copper-ammonia to catalyze thiosulfate for gold leaching, traditionally, copper-ammonia is used to catalyze thiosulfate for gold leaching in an open reactor. During the gold leaching stirring process, ammonia is extremely volatile, and it is necessary to increase the concentration of the gold leaching reagent to ensure the gold leaching kinetics. First, the dosage of the leaching agent thiosulfate is large. Second, the oxidation effect of Cu(NH3)4 2+ on S2O3 2– is enhanced. In addition, in an open reactor, the dissolved oxygen content in the solution is high, and O2 has an impact on S2O3 2–Strong oxidation. This results in a large consumption of the leaching agent thiosulfate. By adjusting the concentrations of dissolved O2, the leaching agent (thiosulfate), and the catalyst (copper, ammonia) to a lower level, the present invention reduces the pulp potential to an appropriate range and leaches gold in a closed reactor, avoiding the threat of ammonia volatilization to the environment and significantly reducing the consumption of the leaching agent and Cu(NH3)4 2+ / O2's strong oxidation of S2O3 2– , significantly reducing the consumption of gold leaching reagents (especially thiosulfate). Second, when using copper powder to displace and recover gold, the amount of copper powder used is 300 times the theoretical amount. The amount of copper powder used is low and the consumption is small, significantly reducing the gold recovery cost. Third, the present invention combines the displaced lean solution supplemented with the leaching agent thiosulfate and the copper-containing pickling solution (pH adjusted to 10), and the combined solution can be directly used for leaching fresh ore in the next cycle without additional supplementation of copper sulfate, that is, the copper consumed by copper powder displacement in the previous cycle can just be used to supplement the copper required for gold leaching in the current cycle, significantly reducing the catalytic gold leaching cost of the gold ore. In summary, the process of the present invention can significantly reduce the gold extraction cost of the entire solution cycle.

[0034] II. The thiosulfate process for gold extraction of the present invention can significantly shorten the gold extraction process. According to the gold extraction process of the present invention, finely ground gold ore only needs to go through several short steps such as leaching, copper powder displacement, electrolytic refining, pickling for impurity removal, and ingot casting to obtain gold ingots. Compared with other thiosulfate gold leaching and recovery processes proposed in the industry, the gold extraction process flow is greatly shortened, reducing the process investment and production cost.

[0035] III. The thiosulfate process for gold extraction of the present invention has stable gold extraction indicators in solution circulation. When using thiosulfate to leach actual gold ore, metal elements such as Cu, Ag, and Hg in the gold ore will inevitably dissolve into the leaching solution. With the increase in the number of solution circulation times, the accumulation of these inevitable metal ions will affect the gold leaching to varying degrees and affect the stability of gold recovery indicators. The process of the present invention uses copper powder displacement. In addition to displacing the target metal, it can also remove most of the inevitable metal ions in the leaching solution, realizing the purification of the leaching solution, which is more conducive to the continuous and stable use of the leaching solution and further improving the stability of various gold extraction indicators.

[0036] IV. The present invention introduces nitrogen into the leaching solution to evacuate oxygen, which is beneficial to reducing the amount and dissolution amount of copper powder, preventing the redissolution of gold after displacement, and further improving the metal displacement efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is the process flow diagram of the thiosulfate process for gold extraction of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0038] For the convenience of understanding the present invention, the present invention will be described more comprehensively and in detail below in conjunction with the accompanying drawings of the specification and preferred embodiments, but the protection scope of the present invention is not limited to the following specific embodiments.

[0039] Unless otherwise defined, all the technical terms used hereinafter have the same meaning as commonly 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 protection scope of the present invention.

[0040] Unless otherwise specifically stated, various raw materials, reagents, instruments, and equipment used in the present invention can be obtained through the market or can be prepared by existing methods.

[0041] The following are the comparative examples and examples of gold extraction from quartz vein-type oxidized gold ore.

[0042] Raw material 1: The raw material is a certain quartz vein-type oxidized gold ore with a gold grade of 2.66 g / t. The main gangue component is SiO2 with a content of 88.6%. First, the ore is crushed and wet ball milled to -200 mesh accounting for 90% by weight, and the pulp is adjusted to a mass concentration of 33% to obtain raw material pulp 1. It should be noted that in the comparative examples and examples, "t" -矿 represents the ore mass.

[0043] Comparative Example 1

[0044] Copper sulfate, ammonia water, and sodium thiosulfate are successively added to raw material pulp 1 to be 0.02 mol / L, 1.5 mol / L, and 0.20 mol / L respectively. Then, the pH value of the pulp is adjusted to 10.0 with sodium hydroxide and sulfuric acid. Under the condition of 25 °C and in an open reactor, leaching is carried out at a stirring speed of 300 r / min for 8.0 h. During the leaching process, the pulp potential is maintained at 241 - 253 mV, and the dissolved oxygen concentration is 0.65 - 0.71 mg / L. The gold leaching rate is 86.53%. The consumption of copper sulfate, ammonia water, and sodium thiosulfate is 1.01 kg / t -矿 、32 kg / t -矿 、27.8 kg / t -矿 . Example 1

[0045] As Figure 1 shown, this example includes the following steps:

[0046] (1) Using raw material pulp 1 as the object, leaching is carried out with copper sulfate, ammonia water, and sodium thiosulfate at low reagent concentrations. The leaching conditions are as follows: copper sulfate 0.001 mol / L (copper ion concentration 63.5 mg / L), ammonia water 0.8 mol / L, sodium thiosulfate 0.07 mol / L, stirring speed 400 r / min, and the pH of the pulp is adjusted to 10. Leaching is carried out in a closed reactor at 25 °C for 8.0 h. During the leaching process, the pulp potential is maintained at 196 - 200 mV, and the average dissolved oxygen concentration is controlled at about 0.3 mg / L. The leaching rate of gold is 86.84%, and the consumption of copper sulfate and sodium thiosulfate are 0.22 kg / t -矿 and 12.42 kg / t -矿 respectively. Since leaching is carried out in a closed reactor, the consumption of ammonia water is negligible.

[0047] (2) Nitrogen is introduced into the leaching precious liquid obtained after filtration in step (1) to expel air, and then copper powder is added for a metal displacement reaction to obtain gold-rich crude copper and displacement lean liquid. The displacement is carried out according to a mass ratio of gold to copper of 2:1, and the amount of copper powder used is 300 times the theoretical amount (copper and gold are displaced according to 1:2). Under the above conditions, the displacement rate of gold is 99.48%, and the consumption of copper powder is 0.042 kg / t -矿 .

[0048] (3) The gold-rich crude copper obtained in step (2) is subjected to electrolytic refining. The electrolytic refining conditions are as follows: the electrolyte is sulfuric acid, the electrolysis temperature is 25 °C, the current density is 220 A / m 2 , the electrolysis time is 48 h, and gold mud with a gold content of 98.34% and pure copper (cathode copper) with a copper content of 99.96% are obtained.

[0049] (4) The gold mud obtained in step (3) is stirred and washed with 1 mol / L dilute sulfuric acid. The stirring speed for washing is 300 r / min, the time is 1 h, the temperature is 80 °C, and the solid-liquid ratio is 1:2. After washing, 99.91% pure gold and copper-containing pickling solution with a copper content of 20.3 mg / L are obtained. Example 2

[0050] This embodiment further includes the following steps: First, take a sample from the replaced lean solution obtained in step (2) of Embodiment 1 and titrate to obtain a sodium thiosulfate concentration of 0.052 mol / L. Second, adjust the pH of the copper-containing pickling solution obtained in step (4) of Embodiment 1 to 10. Finally, combine the replaced lean solution with the pH-adjusted copper-containing pickling solution for the leaching of fresh ore in the next cycle. Through titration and ICP analysis, the concentrations of copper ions and ammonia water in the leaching solution at the beginning of leaching are 63.68 mg / L and 0.78 mol / L of ammonia water, respectively. During the leaching process, the pulp potential is maintained at 197 - 202 mV, the average concentration of dissolved oxygen is controlled at about 0.27 mg / L, the leaching time is 12 h, the leaching temperature is 35 °C, and other leaching conditions are the same as those in step (1) of Embodiment 1. After leaching, the gold leaching rate is 85.92%, and the consumption of copper sulfate and sodium thiosulfate are 0.092 kg / t -矿 , 10.26 kg / t -矿 , and due to leaching in a closed reactor, the consumption of ammonia water is negligible.

[0051] The operations of steps (2) and (3) in this embodiment are the same as those of steps (2) and (3) in Embodiment 1. According to the above conditions, the gold replacement rate in step (2) is 98.88%, and the copper powder consumption is 0.034 kg / / t -矿 . In step (3), gold mud with a gold content of 97.99% and pure copper (cathode copper) with a copper content of 99.85% are obtained.

[0052] The difference between step (4) of this embodiment and step (4) of Embodiment 1 is that: stir and wash the gold mud obtained in step (3) with 2 mol / L dilute sulfuric acid for 1.5 h, the solid-liquid ratio is 1:3, and the stirring speed is 200 r / min. After washing according to this embodiment, 99.97% pure gold and a copper-containing pickling solution with a copper content of 24.66 mg / L are obtained. Embodiment 3

[0053] This embodiment further includes the following steps: Add calcium thiosulfate to the stripped lean solution obtained in step (2) of Embodiment 1 to 0.08 mol / L, adjust the pH of the copper-containing pickling solution obtained in step (4) of Embodiment 1 to 10, and then combine the stripped lean solution supplemented with calcium thiosulfate with the pH-adjusted copper-containing pickling solution for the leaching of fresh ore in the next cycle. Through titration and ICP analysis, the concentrations of copper ions and ammonia water in the leaching solution at the initial stage of leaching are 62.14 mg / L and 0.76 mol / L of ammonia water, respectively. During the leaching process, the pulp potential is maintained at 195 - 199 mV, the average concentration of dissolved oxygen is controlled at about 0.34 mg / L, the temperature is 35°C, the leaching time is 10 h, and other leaching conditions are the same as those in step (1) of Embodiment 1. After leaching, the gold leaching rate is 87.11%, and the consumption of copper sulfate and calcium thiosulfate are 0.079 kg / t -矿 and 10.1 kg / t -矿 , respectively. Since the leaching is carried out in a closed reactor, the consumption of ammonia water is negligible.

[0054] The operation of step (2) in this embodiment is the same as that of step (2) in Embodiment 1. According to the above conditions, the gold replacement rate in step (2) is 99.37%, and the copper powder consumption is 0.053 kg / t -矿 .

[0055] The difference between step (3) in this embodiment and step (3) in Embodiment 1 is that the current density is 100 A / m 2 , the electrolysis time is 24 h, and the electrolysis temperature is 35°C. According to the above conditions, gold mud with a gold content of 98.26% and pure copper with a copper content of 99.93% are obtained.

[0056] The difference between step (4) in this embodiment and step (4) in Embodiment 1 is that the gold mud is stirred and washed with 0.5 mol / L dilute sulfuric acid, the washing and stirring time is 2 h, the temperature is 70°C, the solid-liquid ratio is 1:3, and the stirring speed is 400 r / min. After washing according to this embodiment, 99.9% pure gold and a copper-containing pickling solution with a copper content of 18.91 mg / L are obtained.

[0057] The following are the comparative examples and embodiments of gold extraction from sulfide-type gold ore.

[0058] Raw material two: The raw material is a certain sulfide-type gold ore with a gold grade of 48 g / t. The main gangue components are pyrite, SiO2 and mica, and it also contains a small amount of chalcopyrite. The amount of gold encapsulated in the gold ore is small, belonging to an easily leachable gold ore. First, the ore is crushed and wet ball-milled to -200 mesh accounting for wt90%, and the pulp is adjusted to a mass concentration of 25% to obtain raw material pulp two.

[0059] Comparative Example 2

[0060] Copper sulfate, ammonia water, and ammonium thiosulfate were successively added to raw material pulp II to 0.03 mol / L, 1.5 mol / L, and 0.30 mol / L respectively. Then, the pH value of the pulp was adjusted to 10.0 with sodium hydroxide and sulfuric acid. In an open reactor at 30 °C, leaching was carried out at a stirring speed of 300 r / min for 8.0 h. During the leaching process, the pulp potential was maintained at 247 - 258 mV, and the dissolved oxygen concentration was 0.7 - 0.74 mg / L. The leaching rate of gold was 83.65%. The consumption of copper sulfate, ammonia water, and ammonium thiosulfate was 1.24 kg / t -矿 、36.41 kg / t -矿 、34.59 kg / t -矿 respectively. Example 4

[0061] (1) Taking raw material pulp II as the object, leaching was carried out using copper sulfate, ammonia water, and ammonium thiosulfate with low reagent concentrations. The leaching conditions were: copper sulfate 0.0005 mol / L (copper ion concentration 31.5 mg / L), ammonia water 0.45 mol / L, ammonium thiosulfate 0.075 mol / L, stirring speed 400 r / min, pH = 10. Leaching was carried out in a closed reactor at 30 °C for 12.0 h. During the leaching process, the pulp potential was maintained at 197 - 201 mV, and the average dissolved oxygen concentration was controlled at about 0.28 mg / L. The leaching rate of gold was 83.14%. The consumption of copper sulfate and ammonium thiosulfate was 0.35 kg / t -矿 、17.61 kg / t -矿 respectively. Since leaching was carried out in a closed reactor, the consumption of ammonia water was negligible.

[0062] (2) Nitrogen was introduced into the leaching precious liquid obtained after filtering the gold leaching in step (1) to exhaust air, and then copper powder was added for metal displacement reaction to obtain gold-rich crude copper and displacement lean liquid. The displacement was carried out according to the mass ratio of gold to copper of 2:1, and the amount of copper powder used was 300 times the theoretical amount (copper and gold are displaced according to 1:2). Under the above conditions, the displacement rate of gold was 98.66%, and the consumption of copper powder was 0.064 kg / t -矿 respectively.

[0063] (3) The gold-rich crude copper obtained in step (2) was electrolytically refined. The conditions for electrolytic refining were: the electrolyte was sulfuric acid, the electrolysis temperature was 30 °C, the current density was 220 A / m 2 ², the electrolysis time was 24 h, and gold mud with a gold content of 97.89% and pure copper (cathode copper) with a copper content of 99.91% were obtained.

[0064] (4) The gold mud obtained in step (3) is stirred and washed with 1 mol / L dilute sulfuric acid. The stirring speed for washing is 300 r / min, the time is 1 h, the temperature is 80 °C, and the solid-liquid ratio is 1:2. After washing, 99.95% pure gold and copper-containing pickling solution with a copper content of 21.81 mg / L are obtained. Example 5

[0065] This example further includes the following steps: The displacement lean solution obtained in step (2) of Example 4 is supplemented with sodium thiosulfate to 0.06 mol / L, and the pH of the copper-containing pickling solution obtained in step (4) of Example 4 is adjusted to 10. Then, the displacement lean solution supplemented with sodium thiosulfate and the pH-adjusted copper-containing pickling solution are combined for the leaching of fresh ore in the next cycle. Through titration and ICP analysis, the concentrations of copper ions and ammonia water in the leaching solution at the beginning of leaching are 29.97 mg / L and 0.43 mol / L of ammonia water, respectively. During the leaching process, the pulp potential is maintained at 199 - 203 mV, the average concentration of dissolved oxygen is controlled at about 0.31 mg / L, the temperature is 35 °C, the leaching time is 11 h, and other leaching conditions are the same as those in step (1) of Example 4. After leaching, the leaching rate of gold is 82.92%, and the consumption of copper sulfate and sodium thiosulfate are 0.094 kg / t -矿 and 17.28 kg / t -矿 respectively. Since the leaching is carried out in a closed reactor, the consumption of ammonia water is negligible.

[0066] The operation of step (2) in this example is the same as that of step (2) in Example 4. According to the above conditions, the displacement rate of gold in step (2) is 99.06%, and the consumption of copper powder is 0.06 kg / t -矿 respectively.

[0067] The difference between step (3) of this example and step (3) of Example 4 is that the current density is 150 A / m 2 and the electrolysis time is 48 h. Gold mud with a gold content of 98.3% and pure copper with a copper content of 99.92% are obtained.

[0068] The difference between step (4) of this example and step (4) of Example 4 is that the gold mud is stirred and washed with 0.5 mol / L dilute sulfuric acid, the temperature is 90 °C, the solid-liquid ratio is 1:3, and the washing time is 2 h. After washing, 99.93% pure gold and copper-containing pickling solution with a copper content of 25.1 mg / L are obtained. Example 6

[0069] This embodiment further includes the following steps: Add sodium thiosulfate to the replaced lean solution obtained in step (2) of Embodiment 5 to 0.08 mol / L, adjust the pH of the copper-containing pickling solution obtained in step (4) of Embodiment 5 to 10, and then combine the replaced lean solution supplemented with sodium thiosulfate and the pH-adjusted copper-containing pickling solution for the leaching of fresh ore in the next cycle. Through titration and ICP analysis, the concentrations of copper ions and ammonia water in the leaching solution at the initial stage of leaching are 29.1 mg / L and 0.41 mol / L of ammonia water, respectively. During the leaching process, the pulp potential is maintained at 198 - 202 mV, the average concentration of dissolved oxygen is controlled at about 0.27 mg / L, the temperature is 25°C, the leaching time is 9 h, and other leaching conditions are the same as those in step (1) of Embodiment 4. After leaching, the leaching rate of gold is 83.11%, and the consumption of copper sulfate and sodium thiosulfate are 0.11 kg / t -矿 and 18.15 kg / t -矿 , respectively. Since the leaching is carried out in a closed reactor, the consumption of ammonia water is negligible.

[0070] The operation of step (2) in this embodiment is the same as that of step (2) in Embodiment 4. According to the above conditions, the replacement rate of gold in step (2) is 98.46%, and the consumption of copper powder is 0.074 kg / t -矿 .

[0071] The difference between step (3) in this embodiment and step (3) in Embodiment 4 is that the electrolysis temperature is 25°C and the current density is 200 A / m 2 , obtaining gold mud with a gold content of 98.4% and pure copper with a copper content of 99.86%.

[0072] The difference between step (4) in this embodiment and step (4) in Embodiment 4 is that the gold mud is stirred and washed with 2 mol / L dilute sulfuric acid, the washing and stirring time is 1.5 h, the temperature is 90°C, the solid-liquid ratio is 1:3, and the stirring speed is 200 r / min. After washing, 99.93% pure gold and a copper-containing pickling solution with a copper content of 22.61 mg / L are obtained.

[0073] The pure gold obtained in the above embodiments is made into gold ingots through casting.

[0074] The closed reactor described in the present invention mainly refers to a completely closed glass reactor. During the reaction process, the pH and dissolved oxygen concentration of the leaching solution in the closed reactor can be detected.

[0075] The pure nitrogen is used for purging air with nitrogen, and the flow rate is 1 - 3 ml / min.

[0076] The copper powder used for metal replacement refers to copper powder with a fineness of -200 to +400 mesh.

[0077] The copper concentration in the replaced lean solution increases by 20 - 25 mg / L due to the dissolution of copper powder.

[0078] The gold-rich crude copper refers to the crude copper with a gold content of 13.04 - 13.95 kg / t and a copper content of 98.5 - 98.6% after copper powder replacement.

Claims

1. A short-process and low-cost continuous and stable gold extraction process by thiosulfate method, characterized in that It includes the following steps: (1) In a closed reactor, by adjusting the dissolved O2, the concentration of the leaching agent thiosulfate, and the concentration of the copper ammonia catalyst within a certain range at a relatively low level, the pulp potential is decreased to an appropriate range to leach the gold ore, and the leached residue and the leached pregnant solution are obtained by filtration; (2) Pure nitrogen is introduced into the leached pregnant solution to remove the oxygen in the solution, and then copper powder is added for replacement, and the copper concentrate rich in gold and the replacement lean solution are obtained by filtration; (3) The copper concentrate rich in gold is treated by electrolytic refining, pure copper is obtained at the cathode, and gold mud is obtained at the anode; (4) The gold mud is washed with dilute acid to obtain an acid washing solution containing copper and pure gold; The adjustment of the dissolved O2 concentration at a relatively low level means that the average concentration of dissolved O2 is controlled between 0.25 and 0.35 mg / L; the adjustment of the leaching agent thiosulfate at a relatively low level means that the concentration of thiosulfate is adjusted to 0.05 to 0.08 mol / L; the adjustment of the copper ammonia catalyst concentration at a relatively low level means that the concentration of copper sulfate is adjusted to 0.5 to 1 mmol / L and the concentration of ammonia water is adjusted to 0.4 to 0.8 mol / L; the decrease of the pulp potential to an appropriate range means that the pulp potential is controlled at 195 to 205 mV; In step (2), the amount of copper powder used is 300 times the theoretical amount; in step (2), the flow rate of the pure nitrogen introduced is 1 to 3 ml / min; the fineness of the copper powder used is -200 to +400 mesh; The acid used for the dilute acid washing in step (4) is one or two of sulfuric acid, nitric acid, and hydrochloric acid; the acid washing conditions are: the acid concentration is 0.5 to 2 mol / L, the amount of acid added is according to the solid-liquid ratio of 1:(2 to 3), the acid washing time is 1 to 2 h, the acid washing temperature is 25 to 100 °C, and the stirring speed is 200 to 400 r / min; The replacement lean solution obtained in step (2) is supplemented with thiosulfate, and the pH of the acid washing solution containing copper obtained in step (4) is adjusted to 10, and then the replacement lean solution supplemented with thiosulfate and the acid washing solution containing copper with adjusted pH are combined for the leaching of fresh ore in the next cycle.

2. The continuous and stable gold extraction process by the short-process and low-cost thiosulfate method according to claim 1, wherein: The thiosulfate refers to one or more of calcium thiosulfate, sodium thiosulfate, and ammonium thiosulfate.

3. The continuous and stable gold extraction process by the short-process low-cost thiosulfate method according to claim 1, characterized in that: The conditions for leaching the gold ore in step (1) are that the pulp concentration is 25 to 50%, the part of the gold ore ground to a particle size of -200 mesh accounts for more than 90 wt% of the whole, during leaching, the reaction temperature is controlled at 25 to 35 °C, the pH value of the reaction system is 9 to 12, the reaction time is 8 to 12 h, and the stirring speed is 200 to 400 r / min.

4. The continuous and stable gold extraction process by the short-process and low-cost thiosulfate method according to claim 1, characterized in that: The conditions for electrolytic refining in step (3) are as follows: the electrolyte is one of sulfuric acid or nitric acid, the electrolysis temperature is 25 - 35 °C, and the current density is 100 - 230 A / m 2 , and the electrolysis time is 12 - 48 h.

5. The continuous and stable gold extraction process by the short-process low-cost thiosulfate method according to claim 1, characterized in that: The pure copper refers to pure copper with a purity of more than 3N; the pure gold refers to pure gold with a purity of more than 3N; the gold mud obtained at the anode of electrolytic refining refers to gold mud with a gold content of more than 97%.

6. The short-process low-cost continuous and stable gold extraction process by the thiosulfate method according to any one of claims 1 to 5, characterized in that: The thiosulfate supplemented to the replacement lean solution includes one or more of calcium thiosulfate, sodium thiosulfate, and ammonium thiosulfate; the supplementary amount of thiosulfate is to supplement the concentration of thiosulfate in the leaching solution to 0.05 to 0.08 mol / L.

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