Leaching method for iron oxide wrapped gold in calcine

Abstract

The invention discloses a leaching method for iron oxide coated gold in calcine, which comprises the following steps: adding water into the calcine to obtain ore pulp, adding an iron leaching agent to adjust the system to be weakly acidic, leaching, carrying out solid-liquid separation to obtain iron-removed slag, adding water into the iron-removed slag to prepare the ore pulp, adding the iron leaching agent into the ore pulp, and carrying out solid-liquid separation on the ore pulp to obtain the iron oxide coated gold in the calcine, and adjusting the pH value of the ore pulp to be neutral or alkalescent, adding a gold leaching agent, and performing solid-liquid separation after leaching to obtain gold leaching residues and a gold-containing pregnant solution. According to the leaching method for the iron oxide wrapped gold in the calcine, the wrapped gold in the iron oxide phase can be fully opened, and the gold recovery rate is increased by 15%-20%.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgical technology, and particularly relates to a leaching method for gold encapsulated in iron oxide. Background Technology

[0002] In the field of hydrometallurgy, the roasting of raw materials such as pyrrhotite, pyrrhotite, and arsenopyrite produces a large amount of roasted ore containing iron oxides, primarily hematite (Fe2O3) and magnetite (Fe3O4). Due to the reconstruction of the mineral lattice during roasting, the iron oxides form a dense coating layer, encapsulating some gold particles. This makes it difficult for the subsequent gold leaching agent to effectively contact the gold, resulting in a generally low gold leaching rate.

[0003] To address the problem of iron oxide encapsulation, existing technologies have proposed various solutions, but all have significant drawbacks. For example, the sulfuric acid leaching / curing method uses sulfuric acid to dissolve hematite, generating sulfates. This method has low raw material costs and a fast reaction rate, but concentrated sulfuric acid is highly corrosive to equipment, and the large amount of sulfate waste liquid generated still requires subsequent treatment. The alkaline leaching / alkaline decomposition method uses alkaline media to break down iron oxide and silica mineral encapsulation. This method is relatively clean, but it requires equipment with high alkali resistance and has demanding leaching conditions. Existing technologies propose using oxalic acid / oxalate to leach iron from roasted sand. This method has a high iron leaching rate from hematite, but oxalic acid / oxalate has poor solubility in aqueous solution, and the complexation ability of oxalate ions with iron is limited. Leaching often requires high concentrations and temperatures, and the subsequent gold recovery process uses cyanide leaching, requiring acid-base conversion between processes, resulting in a large waste of alkali.

[0004] Therefore, developing an environmentally friendly immersion gold process or method that can efficiently remove iron oxide coatings is a technical problem that urgently needs to be solved in the field of hydrometallurgy. Summary of the Invention

[0005] To overcome the problem of low gold leaching rate caused by iron oxide encapsulation in existing technologies, this invention provides a leaching method for gold encapsulated in iron oxide in calcined sand. This process can efficiently open the iron oxide encapsulation and leach gold, has low equipment requirements, reduces acid-base conversion processes, and is simple.

[0006] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows:

[0007] This invention provides a leaching method for gold encapsulated in iron oxide in calcined sand, comprising the following steps: S1. Add water to roasted sand to obtain a slurry. After adding an iron leaching agent, adjust the system to be weakly acidic. After leaching, separate the solid and liquid to obtain iron-removed slag. The iron leaching agent is a mixture of sulfosalicylic acid and sulfosalicylate, and the molar ratio of sulfosalicylic acid to sulfosalicylate in the mixture is 0.5-1:1-2.5. S2. Add water to the iron-removing slag obtained in S1 to prepare a slurry. Adjust the pH of the slurry to neutral or weakly alkaline and then add the gold leaching agent. After leaching, separate the solid and liquid to obtain gold-leaching slag and gold-containing precious solution.

[0008] The iron-impregnating agent in this invention is capable of reacting with Fe. 3+ / Fe 2+ A complex, acidic solution of a mixture of organic acids and their salts, wherein the organic acid anions can react with Fe. 3+ / Fe 2+ A stable, water-soluble complex is formed, and Fe in the calcined sand can be removed by solid-liquid separation. 3+ / Fe 2+ Open the gold package. In this invention, sulfosalicylic acid and sulfosalicylate are used as iron leaching agents, which can form a buffer system to maintain weakly acidic conditions. When using a single acid, the solution pH will be too low, and when using a single salt, the solution pH will be too high, both of which are not conducive to the occurrence of coordination reactions.

[0009] In this invention, controlling the molar ratio of sulfosalicylic acid to sulfosalicylate to be 0.5–1:1–2.5 creates a buffer system that maintains a weakly acidic condition. Using a single acid results in an excessively low pH, while using a single salt results in an excessively high pH, ​​both of which are detrimental to the coordination reaction. A slightly higher proportion of sulfosalicylate is more efficient and economical. Specifically, sulfosalicylate can directly dissociate in solution into highly coordinating divalent / trivalent sulfosalicylate ions, which can efficiently and rapidly coordinate with iron. Furthermore, sulfosalicylate promotes the dissolution of sulfosalicylic acid, increasing the overall ligand concentration and reducing solution preparation time. Finally, sulfosalicylate is less expensive, making it more economical. However, an excessively high proportion of sulfosalicylate will increase the system pH, reduce the efficiency of the coordination reaction, enhance the hydrolysis of iron, and reduce the iron removal effect.

[0010] As an optional implementation, in the leaching method provided by the present invention, in S1, the sulfosalicylate is selected from one or more of sodium salts, potassium salts, and ammonium salts.

[0011] As an optional implementation, in the leaching method provided by the present invention, in S1, the pH value of the system is adjusted to 2 to 3.5 after adding the iron leaching agent.

[0012] In this invention, the highly active coordination morphology of sulfosalicylate can be maintained under pH conditions of 2–3.5. This is because, under strongly acidic conditions, sulfosalicylic acid undergoes minimal dissociation, with only the sulfonic acid group dissociating to generate monovalent salicylate HOC6H3(COOH)SO3. - It has few coordination sites and weak coordination ability; under weakly acidic conditions, both the sulfonic acid group and the carboxyl group can dissociate, and the divalent sulfosalicylate ion HOC6H3(COO) in the solution... - SO3- It dominates the coordination site, has more coordination sites, and can form a stable chelate ring with iron, resulting in the best coordination effect. Simultaneously, under pH conditions of 2–3.5, it can inhibit Fe... 2+ Fe 3+ Hydrolysis: When the solution pH is too high, Fe 2+ Fe 3+ The increased tendency for hydrolysis leads to the formation of Fe(OH)2 and Fe(OH)3 precipitates, which is detrimental to iron removal. Furthermore, these precipitates adhere to the surface of mineral particles, hindering subsequent gold leaching.

[0013] As an optional implementation, in the leaching method provided by the present invention, in S1, the molar amount of sulfosalicylic acid and sulfosalicylate ligands in the mixture is 2.5 to 3.5 times the molar amount of total iron in the calcined sand.

[0014] In this invention, sulfosalicylate and iron mainly form five- or six-membered chelates in mono- and di-coordinated forms. When both sulfosalicylate and iron exist in di-coordinated forms, a slightly excessive ligand content is beneficial for promoting the coordination reaction and advancing the reaction forward, while achieving almost complete iron leaching. However, in addition to wasting ligands and increasing costs, excessive ligand concentration also has a certain adverse effect on iron leaching. This is because the ionic strength of the leachate increases rapidly at this point, leading to a large amount of free Na+. + / K + Counterions can shield the surface charge of iron complex ions, weakening the electrostatic attraction between the complex and water molecules, resulting in the hydration layer of the complex being compressed and thinned, making the complex unstable.

[0015] As an optional implementation, in the leaching method provided by the present invention, in S1, the sulfosalicylate ligand is (HOC6H3(COOH)SO3 - HOC6H3(COO) - SO3 - or - OC6H3(COO - SO3 - One or more of them.

[0016] As an optional implementation method, in the leaching method provided by the present invention, in S1, the liquid-solid ratio of calcined sand to water is 5 to 10:1.

[0017] As an optional implementation, in the leaching method provided by the present invention, in S1, the leaching temperature is 25-50°C, the stirring rate during the leaching process is 200-400 rpm, and the leaching time is 1-3 hours.

[0018] In this invention, controlling the leaching temperature within the aforementioned range is beneficial for promoting the dissolution of sulfosalicylic acid and sodium sulfosalicylate, and can also increase the coordination reaction rate and reduce the leaching time. However, excessively high temperatures not only increase energy consumption and accelerate water evaporation, but more seriously, high temperatures will promote the dissociation of the formed iron-sulfosalicylate complex, which is detrimental to the stability of the complex and will promote the hydrolysis of iron ions; excessively high temperatures will increase the thermal degradation tendency of organic reactants, making them prone to losing coordination activity. All of these are detrimental to iron leaching.

[0019] As an optional implementation, in the leaching method provided by the present invention, in S2, the gold leaching agent is a mixture of ferricyanide and thiosulfate, wherein the ferricyanide is selected from one or both of sodium ferricyanide or potassium ferricyanide, and the thiosulfate is selected from one or both of sodium thiosulfate or potassium thiosulfate.

[0020] As an optional implementation, in the leaching method provided by the present invention, in S2, the liquid-to-solid ratio of water and iron-removing slag is 2-3:1, the pH of the slurry is 7-9, the concentration of thiosulfate in the gold leaching agent is 0.1-0.3 mol / L, the concentration of ferricyanide is 0.01-0.08 mol / L, the stirring rate is 200-300 rpm, and the leaching time is 2-4 h.

[0021] As an optional implementation, in the leaching method provided by the present invention, the leaching rate of gold in the gold-containing precious solution is greater than 94%.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: The leaching method for gold encapsulated in iron oxide in calcined sand provided by this invention is carried out under weakly acidic conditions, exhibiting high solubility in water and good affinity with Fe. 3+ / Fe 2+ It exhibits strong coordination ability, enabling efficient iron removal at lower concentrations under milder conditions. The iron leaching agent is a mixture of sulfosalicylic acid and sulfosalicylate in a molar ratio of 0.5–1:1–2.5, forming a buffer system that maintains weakly acidic conditions. This allows for efficient and rapid coordination with iron, enhancing the iron removal effect. The gold leaching agent used in this invention is a non-toxic and environmentally friendly mixture of ferricyanide and thiosulfate. This agent can leach gold under neutral or weakly alkaline conditions (pH 7–9), resulting in a smooth pH transition from iron leaching to gold leaching. This significantly reduces reagent consumption and operational complexity for acid-base adjustment, improving the environmental friendliness and economy of the process and lowering equipment requirements. Using the method proposed in this invention, the gold encapsulated in the iron oxide phase can be fully opened, increasing the gold recovery rate by 15%–20%. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0025] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0026] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0027] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0028] The leaching method for gold encapsulated in iron oxides in calcined sand is as follows: Figure 1 As shown, the process includes an iron oxide leaching process and an iron removal slag leaching process. Specifically, roasted sand and water are mixed at a liquid-solid ratio of (5-10):1 to prepare a slurry. An iron leaching agent is added, the pH of the system is adjusted to 2-3.5, the leaching temperature is controlled at 25-50℃, the stirring speed is 200-400 rpm, and the leaching time is 1-3 h. Solid-liquid separation yields iron removal slag and iron leaching solution. The obtained iron removal slag is mixed with water at a liquid-solid ratio of (2-3):1 to prepare a slurry. The pH of the slurry is adjusted to 7-9, and an iron leaching agent is added. The stirring speed is controlled at 200-300 rpm, and the leaching time is 2-4 h. Solid-liquid separation yields gold leaching slag and gold-containing precious solution. Preferably, the iron leaching agent is a mixture of sulfosalicylic acid and sulfosalicylate, with a molar ratio of (0.5-1):(1-2.5), and the molar amount of the acid radical ligand is 2.5-3 times the molar amount of total iron in the roasted sand. The gold immersion agent is a mixture of ferricyanide and thiosulfate, wherein the concentration of thiosulfate is 0.1–0.3 mol / L and the concentration of ferricyanide is 0.01–0.08 mol / L.

[0029] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0030] The present invention does not have special requirements for the pH adjustment, stirring, leaching, solid-liquid separation and other operations, and any operation can be carried out using methods well known in the art.

[0031] The immersion gold method provided by the present invention will be described in detail below with reference to the embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0032] The raw materials used in the following examples and comparative examples are all roasted calcined sand from a refractory gold concentrate containing sulfur and arsenic in Hunan Province. The chemical composition analysis (wt.%) and chemical phase analysis of the gold ore are shown in Table 1 and Table 2.

[0033] Table 1: Chemical composition analysis of calcined sand (wt.%)

[0034] Table 2: Chemical phases of Au in calcined sand

[0035] Example 1 A leaching method for gold encapsulated in iron oxides in calcined sand includes the following steps: (1) Iron oxide leaching process: Water and roasted sand are mixed into a slurry at a liquid-solid ratio of 5:1. Iron leaching agent is added. The iron leaching agent is a mixture of sulfosalicylic acid and sodium sulfosalicylate. The molar ratio of sulfosalicylic acid and sodium sulfosalicylate is 1:1.6. The total molar amount of sulfosalicylate is 2.5 times (2.3 mol / L) of the total molar amount of iron in roasted sand (0.9 mol / L). The pH value of the system is adjusted to 2. The leaching temperature is 45℃. The leaching is carried out at 400 rpm for 2 h. The solid and liquid are separated to obtain iron slag and iron leaching solution. The iron content in the iron leaching solution is measured and the iron leaching rate is calculated.

[0036] (2) Iron slag leaching process: Water and the iron slag obtained in step (1) are mixed at a liquid-solid ratio of 2.5:1 to prepare a slurry and the pH is adjusted to 7. The gold leaching agent is added, which is potassium ferricyanide and sodium thiosulfate. The concentration of potassium ferricyanide is 0.02 mol / L and the concentration of sodium thiosulfate is 0.1 mol / L. The stirring speed is controlled at 300 rpm and leaching is carried out for 4 h. The gold leaching slag and gold-containing precious solution are obtained by filtration. The gold content in the gold-containing precious solution is determined and the gold leaching rate is calculated.

[0037] The iron content in the iron leaching solution and the gold content in the gold leaching solution were measured every 1 hour, and the leaching rate was calculated over time. The results are shown in Table 3.

[0038] Table 3: Changes in iron and gold leaching rates over time in Example 1

[0039] The results of multiple parallel experiments obtained using the above steps are as follows: Compared to the oxalic acid-sodium oxalate mixture used in Comparative Example 2, the sulfosalicylic acid-sodium sulfosalicylate iron leaching agent in this example can achieve almost complete iron leaching (98.32%) under lower concentration and temperature conditions. At this time, the gold leaching rate is 94.42% after leaching for 4 hours. Compared to the direct gold leaching process in Comparative Example 1, the gold leaching rate after iron removal is increased by 19.67%.

[0040] Example 2 A leaching method for gold encapsulated in iron oxides in calcined sand includes the following steps: (1) Iron oxide leaching process: Water and roasted sand are mixed into a slurry at a liquid-solid ratio of 5:1. Iron leaching agent is added. The iron leaching agent is a mixture of sulfosalicylic acid and sodium sulfosalicylate. The molar ratio of sulfosalicylic acid and sodium sulfosalicylate is 1:2. The total molar amount of sulfosalicylate is 3 times (2.7 mol / L) of the total molar amount of iron in roasted sand (0.9 mol / L). The pH value of the system is adjusted to 2. The leaching temperature is 25℃. The leaching is carried out at 400 rpm for 2 hours. The solid and liquid are separated to obtain iron slag and iron leaching solution. The iron content in the iron leaching solution is measured and the iron leaching rate is calculated.

[0041] (2) Iron slag leaching process: Water and the iron slag obtained in step (1) are mixed at a liquid-solid ratio of 2.5:1 to prepare a slurry and the pH is adjusted to 7. The gold leaching agent is added, which is potassium ferricyanide and sodium thiosulfate. The concentration of potassium ferricyanide is 0.02 mol / L and the concentration of sodium thiosulfate is 0.1 mol / L. The stirring speed is controlled at 300 rpm and leaching is carried out for 4 h. The gold leaching slag and gold-containing precious solution are obtained by filtration. The gold content in the gold-containing precious solution is determined and the gold leaching rate is calculated.

[0042] The iron content in the iron leaching solution and the gold content in the gold leaching solution were measured every 1 hour, and the leaching rate was calculated over time. The results are shown in Table 4.

[0043] Table 4: Changes in iron and gold leaching rates over time in Example 2

[0044] The results of multiple parallel experiments using the above steps are as follows: Compared to the oxalic acid-sodium oxalate mixture used in Comparative Example 2, the sulfosalicylic acid-sodium sulfosalicylate iron leaching agent in this example can achieve almost complete iron leaching (99.53%) under conditions of lower concentration and room temperature. At this time, the gold leaching rate is 95.15% after leaching for 4 hours. Compared to the direct gold leaching process in Comparative Example 1, the gold leaching rate after iron removal is increased by 20.4%.

[0045] Example 3 A leaching method for gold encapsulated in iron oxides in calcined sand includes the following steps: (1) Iron oxide leaching process: Water and roasted sand are mixed at a liquid-solid ratio of 5:1 to form a slurry. Iron leaching agent is added. The iron leaching agent is a mixture of sulfosalicylic acid and sodium sulfosalicylate. The molar ratio of sulfosalicylic acid and sodium sulfosalicylate is 1:2.5. The total molar amount of sulfosalicylate is 3.5 times (3.15 mol / L) of the total molar amount of iron in roasted sand (0.9 mol / L). The pH value of the system is adjusted to 3.5. The leaching temperature is 25℃. The leaching is carried out at 400 rpm for 2 h. The solid and liquid are separated to obtain iron slag and iron leaching solution. The iron content in the iron leaching solution is measured and the iron leaching rate is calculated.

[0046] (2) Iron slag leaching process: Water and the iron slag obtained in step (1) are mixed at a liquid-solid ratio of 2.5:1 to prepare a slurry and the pH is adjusted to 7. The gold leaching agent is added, which is potassium ferricyanide and sodium thiosulfate. The concentration of potassium ferricyanide is 0.02 mol / L and the concentration of sodium thiosulfate is 0.1 mol / L. The stirring speed is controlled at 300 rpm and leaching is carried out for 4 h. The gold leaching slag and gold-containing precious solution are obtained by filtration. The gold content in the gold-containing precious solution is determined and the gold leaching rate is calculated.

[0047] The iron content in the iron leaching solution and the gold content in the gold leaching solution were measured every 1 hour, and the leaching rate was calculated over time. The results are shown in Table 5.

[0048] Table 5: Changes in iron and gold leaching rates over time in Example 3

[0049] The results of multiple parallel experiments using the above steps are as follows: Compared to the oxalic acid-sodium oxalate mixture used in Comparative Example 2, the sulfosalicylic acid and sodium sulfosalicylate leaching agent in this example can achieve almost complete iron leaching (99.66%) under conditions of lower concentration and room temperature. At this point, the gold leaching rate is 96.01% after leaching for 4 hours. Compared to the direct gold leaching process in Comparative Example 1, the gold leaching rate after iron removal is increased by 21.26%.

[0050] Example 4 The difference from Example 1 is that the iron oxide immersion process involves adjusting the pH of the system to 4, while the remaining steps are the same as in Example 1.

[0051] The iron content in the iron leaching solution and the gold content in the gold leaching solution were measured every 1 hour, and the leaching rate was calculated over time. The results are shown in Table 6.

[0052] Table 6: Changes in gold leaching rate over time in Example 4

[0053] The results of multiple parallel experiments obtained using the above steps are as follows: when the pH is 4 during the iron leaching process, the iron leaching rate is 94.65%. Compared with the direct gold leaching process in Comparative Example 1, the gold leaching rate after iron removal in this comparative example is increased by 16.37%. However, compared with Example 1, the iron leaching rate in this example is reduced by 3.67%, indicating that an excessively high leaching pH is not conducive to iron leaching.

[0054] Comparative Example 1 Water and calcined sand were mixed at a liquid-solid ratio of 2.5:1 to prepare a slurry, and the pH was adjusted to 7. A gold leaching agent, consisting of potassium ferricyanide and sodium thiosulfate, was added. The concentration of potassium ferricyanide was 0.02 mol / L, and the concentration of sodium thiosulfate was 0.1 mol / L. The stirring rate was controlled at 300 rpm, and leaching was carried out for 4 h. The gold leaching residue and gold-containing precious solution were obtained by filtration. The gold content in the gold-containing precious solution was determined, and the gold leaching rate was calculated.

[0055] The gold content in the gold leaching solution was measured every 1 hour, and the leaching rate was calculated over time. The results are shown in Table 7.

[0056] Table 7: Changes in gold leaching rate over time in Comparative Example 1

[0057] The results of multiple parallel experiments obtained using the above steps are as follows: when the original calcined sand is not subjected to the iron leaching process, the gold leaching rate after 4 hours using potassium ferricyanide and sodium thiosulfate leaching agent is 74.75%, indicating that the leaching system does not leach the gold encapsulated in iron oxide.

[0058] Comparative Example 2 (1) Iron oxide leaching process: An oxalic acid-sodium oxalate mixture is used as the leaching agent for the iron leaching process, wherein the molar ratio of oxalic acid concentration to sodium oxalate is 1:2, the total molar amount of oxalic acid concentration and sodium oxalate is 5 times (4.5 mol / L) of the total molar amount of iron in the calcined sand (0.9 mol / L), the leaching temperature is 90℃, and the rest is the same as in Example 1.

[0059] (2) Iron slag removal and gold leaching process: same as in Example 1.

[0060] The iron content in the iron leaching solution and the gold content in the gold leaching solution were measured every 1 hour, and the leaching rate was calculated over time. The results are shown in Table 8.

[0061] Table 8: Changes in gold leaching rate over time in Comparative Example 2

[0062] The results of multiple parallel experiments obtained using the above steps are as follows: using a mixture of oxalic acid and sodium oxalate as the leaching agent, under high concentration of leaching agent and harsh temperature conditions, the leaching rate of iron was 95.12% within 2 hours and the leaching rate of gold was 91.25% within 4 hours. Compared with the direct leaching process in Comparative Example 1, the leaching rate of gold after iron removal was increased by 16.5%.

[0063] Comparative Example 3 The difference from Example 1 is that the molar ratio of sulfosalicylic acid to sodium sulfosalicylate is 2:1, while the remaining steps are the same as in Example 1.

[0064] The iron content in the iron leaching solution and the gold content in the gold leaching solution were measured every 1 hour, and the leaching rate was calculated over time. The results are shown in Table 9.

[0065] Table 9: Changes in gold leaching rate over time in Comparative Example 3

[0066] The results of multiple parallel experiments using the above steps are as follows: when the molar ratio of sulfosalicylic acid to sodium sulfosalicylate is 2:1, the leaching rate of iron is 82.30%. Compared with the direct leaching process in Comparative Example 1, the leaching rate of gold after iron removal in this embodiment is increased by 15.98%. Compared with Example 1, the iron leaching rate in this embodiment is reduced by 16.02%, and more undissolved particles were observed during the experiment. This indicates that because the sulfosalicylate group is not completely dissolved, the content of sulfosalicylate group with coordination activity in the system is less than that in Example 1, resulting in a lower iron leaching rate.

[0067] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. However, it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A leaching method for gold encapsulated in iron oxide in calcined sand, characterized in that, Includes the following steps: S1. Add water to roasted sand to obtain a slurry. After adding an iron leaching agent, adjust the system to be weakly acidic. After leaching, separate the solid and liquid to obtain iron-removed slag. The iron leaching agent is a mixture of sulfosalicylic acid and sulfosalicylate, and the molar ratio of sulfosalicylic acid to sulfosalicylate in the mixture is 0.5-1:1-2.

5. S2. Add water to the iron-removing slag obtained in S1 to prepare a slurry. Adjust the pH of the slurry to neutral or weakly alkaline and then add the gold leaching agent. After leaching, separate the solid and liquid to obtain gold-leaching slag and gold-containing precious solution.

2. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 1, characterized in that, In S1, the sulfosalicylate is selected from one or more of sodium salts, potassium salts, and ammonium salts.

3. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 1, characterized in that, In S1, the pH of the system is adjusted to 2-3.5 after adding the iron leaching agent.

4. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 1, characterized in that, In S1, the molar amount of sulfosalicylic acid and sulfosalicylate ligands in the mixture is 2.5 to 3.5 times the molar amount of total iron in the calcined sand.

5. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 4, characterized in that, The sulfosalicylate ligand is (HOC6H3(COOH)SO3) - HOC6H3(COO) - SO3 - or - OC6H3(COO - SO3 - One or more of them.

6. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 1, characterized in that, In S1, the liquid-solid ratio of calcined sand to water is 5 to 10:

1.

7. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 1, characterized in that, In S1, the leaching temperature is 25–50℃, the stirring rate during the leaching process is 200–400 rpm, and the leaching time is 1–3 h.

8. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 1, characterized in that, In S2, the gold immersion agent is a mixture of ferricyanide and thiosulfate, wherein the ferricyanide is selected from one or both of sodium ferricyanide or potassium ferricyanide, and the thiosulfate is selected from one or both of sodium thiosulfate or potassium thiosulfate.

9. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 1, characterized in that, In S2, the liquid-to-solid ratio of water to iron-removing slag is 2–3:1, the pH of the slurry is 7–9, the concentration of thiosulfate in the gold leaching agent is 0.1–0.3 mol / L, the concentration of ferricyanide is 0.01–0.08 mol / L, the stirring rate is 200–300 rpm, and the leaching time is 2–4 h.

10. The leaching method for gold encapsulated in iron oxide in calcined sand according to claim 1, characterized in that, The gold leaching rate in the gold-containing precious liquor is greater than 94%.

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