Method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore

Abstract

The invention provides a method for preparing high-purity magnesium sulfate heptahydrate by utilizing magnesium-containing gold ore, and belongs to the technical field of comprehensive utilization of resources, the method provided by the invention comprises the following steps: crushing the magnesium-containing gold ore, putting the crushed magnesium-containing gold ore into a dump leaching column, circularly spraying the crushed magnesium-containing gold ore with a hot dilute acetic acid solution and a hot lime water solution in sequence, and discharging the solution; circularly spraying the ore again by using a dilute sulphuric acid solution, and collecting a pickling solution obtained by reacting dilute sulphuric acid with the ore; naturally air-drying the pickling solution to obtain crude salt; the method comprises the following steps: adding water into crude salt, dissolving at a high temperature, adding caustic calcined magnesite to adjust the pH value, heating the solution to boil, keeping the boiling state for 5-6 minutes, quickly cooling the boiling solution to 60-65 DEG C within 2 minutes, quickly filtering, retaining filtrate, naturally cooling and crystallizing the filtrate, filtering, screening out crystals, and drying to obtain magnesium sulfate heptahydrate. The magnesium sulfate product prepared by the invention is relatively high in purity, and the content of MgSO4. 7H2O is 99.7%, the content of iron is 0.0015%, the content of chlorine is 0.015%, and the content of arsenic is 0.0002%.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive resource utilization, and in particular to a method for preparing high-purity magnesium sulfate heptahydrate by utilizing magnesium-containing gold ore. Background Art

[0002] Gold ores generally contain carbonate minerals, such as magnesium carbonate. Such carbonate minerals will affect the leaching rate of gold in the metallurgical process, and it is often necessary to pre-treat the ore with acid to wash away a large amount of carbonate minerals before metallurgical operations. However, a large amount of acid is consumed during the acid treatment process, resulting in increased metallurgical costs, and the pickling liquid produced by the treatment contains a large amount of metal salts, which can pollute the soil and water environment if discharged directly. For example, a large amount of magnesium ions input into natural water bodies may cause eutrophication of the water body and destroy the balance of the aquatic ecosystem; and excessive magnesium ion content in the soil may cause soil salinization and aggravate soil degradation.

[0003] In the prior art, there is a treatment method for recovering magnesium in the pickling solution in the form of magnesium sulfate heptahydrate, which can not only avoid a large amount of magnesium salts from being discharged into the ecosystem with sewage, reduce pollution to the environment, but also make full use of the magnesium element in mineral resources, and make up for the acid consumption cost in the acid treatment through the commercial value of magnesium sulfate heptahydrate. Magnesium sulfate heptahydrate is widely used in agriculture, leather industry, printing and dyeing papermaking, plastics and other industries, and can be used as fertilizer, cotton weighting agent or filler of kapok products, etc., with high commercial value. However, the magnesium sulfate heptahydrate obtained by preparing magnesium-containing gold ore is often of low purity (≤99.5%), which limits its scope of application to a certain extent.

[0004] In view of this, it is necessary to design a method for preparing high-purity magnesium sulfate heptahydrate using magnesium-containing gold ore to solve the above problems. Summary of the invention

[0005] In view of the technical problems existing in the background technology, the present application provides a method for preparing high-purity magnesium sulfate heptahydrate using magnesium-containing gold ore, aiming to solve the technical problems that the magnesium sulfate heptahydrate prepared from magnesium-containing gold ore in the prior art has low purity and limited application scope. The magnesium sulfate product prepared by the present application has a MgSO4·7H2O content of 99.7%, an iron content of 0.0015%, a chlorine content of 0.015%, and an arsenic content of 0.0002%, which meets the requirements of the chemical industry standard HG / T 2680-2017 "Industrial Magnesium Sulfate" for Class I (magnesium sulfate heptahydrate) superior products, and can be used in agriculture with high requirements for heavy metal content and fine chemical industry with high requirements for purity.

[0006] The present application provides a method for preparing high-purity magnesium sulfate heptahydrate using magnesium-containing gold ore, comprising the following steps:

[0007] S1. Crush the magnesium-containing gold ore and put it into a heap leaching column. Spray the ore with a hot dilute acetic acid solution in a circulating manner. Stop spraying the dilute acetic acid solution when the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.0. Then spray the ore with a hot lime water in a circulating manner. Stop spraying the lime water when the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.5. Finally, drain the solution in the heap leaching column;

[0008] S2. Spray the ore obtained in step S1 with a dilute sulfuric acid solution in a circulating manner. Stop spraying the dilute sulfuric acid solution when the pH value of the solution flowing out from the bottom of the heap leaching column stabilizes at 3.0, and collect the pickling solution obtained by the reaction of the dilute sulfuric acid and the ore during the spraying process;

[0009] S3. Naturally air-dry the pickling solution to obtain crude salt;

[0010] S4. Take the crude salt obtained in step S3, dissolve it by heating with water, add light-burned magnesium to adjust the pH to 7.0, then heat to boiling and maintain the boiling state for 5 - 6 min. Then quickly cool the temperature of the boiling solution to 60 - 65 °C within 2 min, quickly filter, retain the filtrate. After the filtrate naturally cools and crystallizes, filter, screen out the crystals and dry them to obtain magnesium sulfate heptahydrate.

[0011] Further, in step S1, the temperature of the dilute acetic acid solution is 35 - 36 °C.

[0012] Further, in step S1, the temperature of the lime water is 45 - 46 °C.

[0013] Further, in step S1, the concentration of the dilute acetic acid solution is 10 - 20 g / L.

[0014] Further, in step S1, the mass concentration of the lime water is 0.5%.

[0015] Further, in step S1, the mass ratio of the magnesium-containing gold ore crushed to a particle size of less than 2 mm is greater than or equal to 90%.

[0016] Further, in step S2, the concentration of the dilute sulfuric acid solution is 20 - 50 g / L.

[0017] Further, the drying temperature of the crystals screened out in step S4 is 40 - 45 °C.

[0018] Further, in step S4, the solid-liquid ratio of taking the crude salt and dissolving it by heating with water is 5:3.

[0019] Further, in the process of natural cooling and crystallization of the filtrate in step S4, it also includes stirring the filtrate at a rate of 50 - 60 r / min.

[0020] The beneficial effects of this application are as follows:

[0021] The present application provides a method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore. By circulating and spraying the ore with a hot dilute acetic acid solution before pickling, acetate ions are complexed with heavy metal ions (such as Fe 2+ , Mn 2+ ) in the ore. By circulating and spraying the ore with a hot lime aqueous solution, the heavy metal ions are further pre-precipitated. In this way, these metal ions can be prevented from co-precipitating with magnesium ions in subsequent steps, thereby improving the purity of the magnesium sulfate product. After pretreatment of the ore with a hot dilute acetic acid solution and a hot lime aqueous solution, the content of MgSO4·7H2O in the crude salt obtained by pickling is greater than 90%.

[0022] In the present application, during the process of purifying the crude salt, the solution after reacting with light-burned magnesium is rapidly cooled from boiling to 65°C within 2 minutes, triggering explosive nucleation, avoiding the entry of impurity ions into the crystal lattice, and significantly improving the purity of the finally prepared magnesium sulfate product.

[0023] The present application uses magnesium-containing gold ore to prepare magnesium sulfate, realizes the recovery of magnesium in the pickling solution, obtains high-purity magnesium sulfate heptahydrate with higher commercial value through the improved process, and makes up for part of the acid consumption cost in the heap leaching process of gold ore. The content of MgSO4·7H2O in the magnesium sulfate product prepared in the present application is 99.7%, the content of iron is 0.0015%, the content of chlorine is 0.015%, and the content of arsenic is 0.0002%, meeting the requirements for Class I (magnesium sulfate heptahydrate) premium products in the chemical industry standard HG / T 2680-2017 "Industrial Magnesium Sulfate", and can be used in agriculture with high requirements for heavy metal content and fine chemical industry with high requirements for purity.

[0024] The above description is only an overview of the technical solution of the present application. In order to be able to understand the technical means of the present application more clearly, it can be implemented according to the content of the specification. And in order to make the above and other purposes, features and advantages of the present application more obvious and understandable, the specific embodiments of the present application are given below. Detailed Description of the Embodiment

[0025] The embodiments of the technical solution of the present application will be described in detail below. The following embodiments are only used to illustrate the technical solution of the present application more clearly, so they are only examples and cannot be used to limit the protection scope of the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "comprising" and "having" and any variations thereof in the specification and claims of this application are intended to cover non-exclusive inclusion.

[0027] In the description of the embodiments of this application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity, specific order or primary-secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "a plurality" is more than two, unless otherwise specifically defined.

[0028] Referring to "embodiments" herein means that specific features, structures or characteristics described in connection with the embodiments can be included in at least one embodiment of this application. The phrase appears in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. Those skilled in the art will explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0029] In the description of the embodiments of this application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can mean: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0030] During the process of removing carbonate minerals from gold ore by acid treatment, a large amount of acid will be consumed, resulting in an increase in metallurgical costs. Moreover, the acid washing solution produced by the treatment contains a large amount of metal salts, and direct discharge will cause environmental pollution. In the prior art, there has been a treatment method for recovering magnesium in the acid washing solution in the form of magnesium sulfate heptahydrate. This not only can avoid a large amount of magnesium salts being discharged into the ecosystem with sewage, reducing environmental pollution, but also can make full use of the magnesium element in the mineral resources, and make up for the acid consumption cost in the acid treatment through the commercial value of magnesium sulfate heptahydrate. However, the magnesium sulfate heptahydrate obtained from magnesium-containing gold ore often has a relatively low purity (≤99.5%), which somewhat limits its application range.

[0031] To solve the technical problem in the prior art that the purity of magnesium sulfate heptahydrate prepared from magnesium-containing gold ore is relatively low and its application range is limited, this application provides a method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore. Before acid washing, the ore is pretreated with a hot dilute acetic acid solution and a hot lime water solution. First, through the acetate ions and heavy metal ions (such as Fe 2+ 、Mn2+ Complex with (such as Fe 2+ , Mn 2+ , As 3+ , etc.), and then further pre - precipitate heavy metal ions (such as Fe, Mn, As, etc.) with hot lime water to avoid the simultaneous precipitation of these metal ions with magnesium ions in subsequent steps, thereby improving the purity of magnesium sulfate products. After pretreatment, the content of MgSO4·7H2O in the crude salt obtained by pickling is greater than 90%; in this application, during the process of purifying the crude salt, the solution after reacting with light - burned magnesia is rapidly cooled from boiling to 65°C within 2 min, triggering explosive nucleation, avoiding the entry of impurity ions into the crystal lattice, and significantly improving the purity of the finally prepared magnesium sulfate product. The content of MgSO4·7H2O in the magnesium sulfate product prepared in this application is 99.7%, the iron content is 0.0015%, the chlorine content is 0.015%, and the arsenic content is 0.0002%, meeting the requirements for Class I (magnesium sulfate heptahydrate) premium products in the chemical industry standard HG / T 2680 - 2017 "Industrial Magnesium Sulfate".

[0032] The embodiment of this application provides a method for preparing high - purity magnesium sulfate heptahydrate from magnesium - containing gold ore, including the following steps:

[0033] S1, Crush the magnesium - containing gold ore and put it into a heap leaching column, spray the ore with a hot dilute acetic acid solution in a circulating manner. When the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.0, stop spraying. Then, spray the ore with a hot lime water in a circulating manner. When the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.5, stop spraying. Finally, discharge the solution in the heap leaching column, and the precipitates or suspended substances generated during the pretreatment reaction are also discharged together with the solution.

[0034] In the embodiment of this application, the mass ratio of the magnesium - containing gold ore crushed to a particle size of less than 2 mm is greater than or equal to 90%.

[0035] In the embodiment of this application, the temperature of the dilute acetic acid solution is 35 - 36°C, and the concentration is 10 - 20 g / L.

[0036] In the embodiment of this application, the temperature of the lime water is 45 - 46°C, and the mass concentration is 0.5%.

[0037] In this application, spraying the ore with a hot dilute acetic acid solution is to complex acetate ions with heavy metal ions (such as Fe 2+ , Mn 2+ ) in the ore, and spraying the ore with hot lime water is to further pre - precipitate heavy metal ions. Pretreating the ore with a hot dilute acetic acid solution and a hot lime water solution can significantly improve the purity of the crude salt, that is, significantly increase the content of MgSO4·7H2O in the crude salt. In actual operation, the dilute acetic acid solution and lime water should be continuously supplemented according to specific conditions to reach the pH value specified in step S1.

[0038] S2. Circulate and spray the ore obtained in step S1 with dilute sulfuric acid solution, and stop spraying when the pH value of the solution flowing out from the bottom of the heap leaching column is stable at 3.0, and collect the pickling solution obtained by the reaction of dilute sulfuric acid and the ore during the spraying process.

[0039] In the embodiment of the present application, the concentration of the dilute sulfuric acid solution is 20 - 50 g / L. In actual operation, the dilute sulfuric acid solution should be continuously replenished according to specific conditions to reach the pH value specified in step S2.

[0040] S3. Naturally air-dry the pickling solution to obtain crude salt.

[0041] In the embodiment of the present application, the content of MgSO4·7H2O in the crude salt is greater than 90%, preferably greater than 92%.

[0042] S4. Take the crude salt obtained in step S3, add water and heat it to dissolve at a solid-liquid ratio of 5:3 (the preferred heating temperature is 70°C), add light-burned magnesia to adjust the pH to 7.0, then heat to boiling and maintain the boiling state for 5 - 6 min, and then quickly cool the temperature of the boiling solution to 60 - 65°C within 2 min, preferably 65°C. Filter quickly at 60 - 65°C, retain the filtrate, wait for the filtrate to cool naturally and crystallize, then filter, screen out the crystals and dry them to obtain magnesium sulfate heptahydrate.

[0043] Among them, the temperature of the boiling solution must be quickly cooled to 60 - 65°C within 2 min to improve the purity of the finally prepared magnesium sulfate product and make it meet the requirements for the first-class (magnesium sulfate heptahydrate) high-quality product in the Chemical Industry Standard HG / T 2680 - 2017 "Industrial Magnesium Sulfate". This is because rapid cooling within two minutes can suddenly increase the supersaturation of the solution, thereby triggering explosive nucleation, avoiding the entry of impurity ions into the crystal lattice, and improving the product purity.

[0044] In the embodiment of the present application, during the process of the filtrate cooling naturally and crystallizing, it also includes stirring the filtrate at a rate of 50 - 60 r / min.

[0045] The following lists some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain the present application and cannot be construed as a limitation of the present application. For those without specific technical or conditions indicated in the embodiments, they shall be carried out according to the techniques or conditions described in the literature in this field or according to the product specifications. For those reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0046] Example 1

[0047] Example 1 provides a method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore, including the following steps:

[0048] S1. Crush the magnesium-containing gold ore so that the mass ratio of the ore with a particle size below 2 mm is 90%. Then put the ore into a heap leaching column, and spray the ore with a dilute acetic acid solution at a temperature of 35°C and a concentration of 15 g / L in a circulating manner. Appropriately replenish the dilute acetic acid solution during the spraying process. Stop spraying when the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.0. Then, spray the ore with a lime water solution at a temperature of 45°C and a mass concentration of 0.5% in a circulating manner. Appropriately replenish the lime water solution during the spraying process. Stop spraying when the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.5. Finally, drain the solution in the heap leaching column.

[0049] S2. Spray the ore obtained in step S1 with a dilute sulfuric acid solution at a concentration of 30 g / L in a circulating manner. Appropriately replenish the dilute sulfuric acid solution during the spraying process. Stop spraying when the pH value of the solution flowing out from the bottom of the heap leaching column stabilizes at 3.0, and collect the acid washing solution obtained from the reaction of the dilute sulfuric acid and the ore during the spraying process into a collecting tank.

[0050] S3. Naturally air-dry the acid washing solution in the collecting tank to obtain crude salt with a MgSO4·7H2O content of 92.64%.

[0051] S4. Weigh 500 g of the crude salt obtained in step S3, add water according to a solid-liquid ratio of 5:3 and heat it to 70°C, stir to dissolve, add light-burned magnesia to adjust the pH of the solution to 7.0, then heat the solution to boiling and keep it boiling for 5 min. Then quickly cool the temperature of the boiling solution to 65°C within 2 min, and quickly filter at this temperature to obtain a filtrate. Stir the obtained filtrate at a rate of 50 - 60 r / min, let it naturally cool to room temperature, filter out the crystals, and dry them at 45°C to obtain a purified magnesium sulfate product with a yield of 71.6%.

[0052] Comparative Example 1

[0053] The difference between Comparative Example 1 and Example 1 is that in step S1, a dilute acetic acid solution and lime water at room temperature are used, and in step S4, the temperature of the boiling solution is naturally cooled to 65°C, including the following steps:

[0054] S1. Crush the magnesium-containing gold ore so that the mass ratio of the ore with a particle size below 2 mm is 90%. Then put the ore into a heap leaching column, and spray the ore with a dilute acetic acid solution at a concentration of 15 g / L in a circulating manner. Appropriately replenish the dilute acetic acid solution during the spraying process. Stop spraying when the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.0. Then, spray the ore with a lime water solution with a mass concentration of 0.5% in a circulating manner. Appropriately replenish the lime water solution during the spraying process. Stop spraying when the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.5. Finally, drain the solution in the heap leaching column.

[0055] S2. Spray the ore obtained in step S1 with a dilute sulfuric acid solution having a concentration of 30 g / L in a circulating manner. During the spraying process, appropriately supplement the dilute sulfuric acid solution. Stop spraying when the pH value of the solution flowing out from the bottom of the heap leaching column stabilizes at 3.0, and collect the pickling solution obtained from the reaction of the dilute sulfuric acid with the ore during the spraying process into a liquid collection tank.

[0056] S3. Naturally air-dry the pickling solution in the liquid collection tank to obtain crude salt with a MgSO₄·7H₂O content of 87.55%.

[0057] S4. Weigh 500 g of the crude salt obtained in step S3, add water according to a solid-liquid ratio of 5:3 and heat to 70 °C, stir to dissolve, add calcined magnesia to adjust the pH of the solution to 7.0, heat the solution to boiling and keep it boiling for 5 min, then wait for the solution temperature to naturally cool to 65 °C, filter to obtain a filtrate. Stir the obtained filtrate at a rate of 50 - 60 r / min to let it naturally cool to room temperature, filter to screen out the crystals, and dry at 45 °C to obtain a purified magnesium sulfate product with a yield of 60.52%.

[0058] Comparative Example 2

[0059] The difference between Comparative Example 2 and Example 1 is that the ore is not pretreated, and the temperature of the boiling solution is naturally cooled to 65 °C, including the following steps:

[0060] S1. Crush the magnesium-containing gold ore so that the mass ratio of the ore with a particle size below 2 mm is 90%, then put the ore into a heap leaching column, spray the ore with a dilute sulfuric acid solution having a concentration of 30 g / L in a circulating manner. During the spraying process, appropriately supplement the dilute sulfuric acid solution. Stop spraying when the pH value of the solution flowing out from the bottom of the heap leaching column stabilizes at 3.0, and collect the pickling solution obtained from the reaction of the dilute sulfuric acid with the ore during the spraying process into a liquid collection tank.

[0061] S2. Naturally air-dry the pickling solution in the liquid collection tank to obtain crude salt with a MgSO₄·7H₂O content of 82.85%.

[0062] S3. Weigh 500 g of the crude salt obtained in step S3, add water according to a solid-liquid ratio of 5:3 and heat to 70 °C, stir to dissolve, add calcined magnesia to adjust the pH of the solution to 7.0, heat the solution to boiling and keep it boiling for 5 min, then wait for the solution temperature to naturally cool to 65 °C, filter to obtain a filtrate. Stir the obtained filtrate at a rate of 50 - 60 r / min to let it naturally cool to room temperature, filter to screen out the crystals, and dry at 45 °C to obtain a purified magnesium sulfate product with a yield of 62.44%.

[0063] In the magnesium sulfate products prepared in Example 1 and Comparative Examples 1 - 2, arsenic is the main heavy metal impurity. The purity of the magnesium sulfate products is shown in the following table.

[0064]

[0065] Referring to the above table, the magnesium sulfate product prepared in Example 1 meets the provisions of the chemical industry standard HG / T2680-2017 "Industrial Magnesium Sulfate" for Class I (magnesium sulfate heptahydrate) superior products, while the magnesium sulfate product of Comparative Example 1-2 does not meet the requirements. Compared with Example 1, the magnesium sulfate product obtained in Comparative Example 1-2 has a reduced content of magnesium sulfate heptahydrate, while the content of impurities such as iron, chlorine, and arsenic is significantly increased. This is because a large amount of impurities enter the pickling solution in Comparative Example 1-2, which relatively reduces the content of magnesium sulfate heptahydrate in the crude salt, and subsequent recrystallization cannot completely remove impurities, resulting in a significant increase in the residual amount in the final product.

[0066] The magnesium sulfate product prepared in Example 1 has a high purity and an arsenic content far below the standard limit. It can be used as a high-purity fertilizer for agricultural fertilization to supplement magnesium and sulfur in the soil; it can also be used as a fine chemical raw material for synthesizing other high-purity magnesium compounds (such as magnesium stearate, magnesium oxide) or sulfates (such as potassium sulfate).

[0067] In summary, the present application provides a method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore, by pretreating the ore with hot dilute acetic acid solution and hot lime water solution before pickling, the purity of crude salt is significantly improved; by rapidly reducing the temperature of the solution after adding light-burned magnesium to 65°C within 2 minutes during the purification of crude salt, the purity of the magnesium sulfate product finally prepared is significantly improved. The magnesium sulfate product prepared by the present application has a MgSO4·7H2O content of 99.7%, an iron content of 0.0015%, a chlorine content of 0.015%, and an arsenic content of 0.0002%, which meets the requirements of the chemical industry standard HG / T2680-2017 "Industrial Magnesium Sulfate" for Class I (magnesium sulfate heptahydrate) superior products, and can be used in agriculture with high requirements for heavy metal content and fine chemical industry with high requirements for purity.

[0068] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A method for preparing high-purity magnesium sulfate heptahydrate using magnesium-containing gold ore, characterized in that: The steps include: S1, crushing the magnesium-gold ore and putting it into a heap leaching column, circulate spraying the ore with a hot dilute acetic acid solution, stop spraying the dilute acetic acid solution when the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.0, then circulate spraying the ore with hot lime water, stop spraying the lime water when the pH value of the solution flowing out from the bottom of the heap leaching column reaches 6.5, and finally discharge the solution in the heap leaching column; S2, cyclically spraying the ore obtained in step S1 with a dilute sulfuric acid solution, stopping the spraying of the dilute sulfuric acid solution when the pH value of the solution flowing out from the bottom of the heap leaching column is stabilized at 3.0, and collecting the pickling liquid obtained by the reaction of the dilute sulfuric acid and the ore during the spraying process; S3, air-drying the pickling solution to obtain crude salt; S4, taking the crude salt obtained in step S3, adding water and heating to dissolve, adding light-calcined magnesium to adjust the pH to 7.0, and then heating to boiling, and keeping the boiling state for 5-6 minutes, then quickly cooling the temperature of the boiling solution to 60-65° C. within 2 minutes, quickly filtering, retaining the filtrate, and after the filtrate is naturally cooled and crystallized, filtering, sieving out the crystals and drying to obtain magnesium sulfate heptahydrate.

2. The method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore according to claim 1, characterized in that: In step S1, the temperature of the dilute acetic acid solution is 35-36°C.

3. The method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore according to claim 1, characterized in that: In step S1, the temperature of the lime water is 45-46°C.

4. The method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore according to claim 2, characterized in that: In step S1, the concentration of the dilute acetic acid solution is 10-20 g / L.

5. The method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore according to claim 3, characterized in that: In step S1, the mass concentration of the lime water is 0.5%.

6. The method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore according to claim 1, characterized in that: In step S1, the magnesium-gold ore is crushed to a particle size of less than 2 mm, and the mass proportion of the ore is greater than or equal to 90%.

7. The method for preparing high-purity magnesium sulfate heptahydrate using magnesium-containing gold ore according to claim 1, characterized in that: In step S2, the concentration of the dilute sulfuric acid solution is 20-50 g / L.

8. The method for preparing high-purity magnesium sulfate heptahydrate from magnesium-containing gold ore according to claim 1, characterized in that: The drying temperature of the crystals screened out in step S4 is 40-45°C.

9. The method for preparing high-purity magnesium sulfate heptahydrate using magnesium-containing gold ore according to claim 1, characterized in that: In step S4, crude salt is added to water and heated to dissolve to a solid-liquid ratio of 5:

3.

10. The method for preparing high-purity magnesium sulfate heptahydrate using magnesium-containing gold ore according to claim 1, characterized in that: In step S4, the process of naturally cooling and crystallizing the filtrate also includes stirring the filtrate at a rate of 50-60 r / min.

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