A method for recovering nickel from nickel-containing waste slag

Abstract

This application relates to the field of hydrometallurgical technology and provides a method for recovering nickel from nickel-containing waste slag, comprising the following steps: collecting nickel-containing waste slag; preparing a slurry by mixing the nickel-containing waste slag and water; adding a first sulfuric acid solution to the slurry, controlling the pH value between 2.7 and 3.3 to carry out a first leaching reaction, and then filtering to obtain a nickel sulfate solution. The method for recovering nickel from nickel-containing waste slag provided by this application, by controlling the pH value of the reaction system between 2.7 and 3.3, not only ensures that a large amount of nickel is leached out, while only a small amount of iron, copper, and aluminum are leached out, but also allows the leached Fe... 3+ Reprecipitation occurs within this pH range to form goethite, while ensuring the leaching of Fe. 3+ The rate is slower than Fe 3+ The increased rate of hydrolysis and precipitation can reduce nickel entrainment and improve nickel recovery. Furthermore, goethite can adsorb leached Cu. 2+ To reduce Cu in nickel sulfate solution 2+ Impurity concentration improves the quality of nickel recovery products.

Description

Technical Field

[0001] This application belongs to the field of hydrometallurgical technology, and in particular relates to a method for recovering nickel from nickel-containing waste slag. Background Technology

[0002] The process of removing impurities during the production of nickel sulfate by hydrometallurgy generates a large amount of nickel-containing waste residue, which exists in the form of hydroxides and has a low impurity content. Therefore, recovering nickel from the nickel-containing waste residue can not only increase the production of nickel sulfate, but also treat the waste residue, reduce the accumulation of solid waste, reduce environmental pressure, and realize the recycling of nickel resources.

[0003] Traditional methods for treating nickel-containing waste involve complete leaching with a high-acidity sulfuric acid solution, followed by the addition of neutralizing agents, oxidizing agents, reducing agents, and other auxiliary materials to adjust the pH and form a precipitate. Deep impurity removal is then achieved through extraction, followed by back-extraction with an organic loading to obtain a metal salt solution. Therefore, existing nickel recovery methods are complex, involve numerous steps, and require a large amount of auxiliary materials for impurity removal, such as soda ash, sodium chlorate, and various extractants. Although the final product has high purity, the high consumption of auxiliary materials and the diverse equipment requirements result in high processing costs and demanding operational skills from employees. Summary of the Invention

[0004] The purpose of this application is to provide a method for recovering nickel from nickel-containing waste slag, aiming to solve the problems of complex processes, numerous steps, and high consumption of auxiliary materials in existing methods for recovering nickel from nickel-containing waste slag.

[0005] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows:

[0006] In a first aspect, this application provides a method for recovering nickel from nickel-containing waste slag, comprising the following steps:

[0007] Collect nickel-containing waste residue;

[0008] Nickel-containing waste residue and water are mixed to form a slurry;

[0009] The first sulfuric acid solution was added to the slurry, and the pH value was controlled between 2.7 and 3.3 to carry out the first leaching reaction. Then, the solution was filtered to obtain nickel sulfate solution.

[0010] Compared with the prior art, this application has the following beneficial effects:

[0011] The method for recovering nickel from nickel-containing waste slag provided in the first aspect of this application involves preparing a slurry from the nickel-containing waste slag and water, then adding a first sulfuric acid solution to the slurry, controlling the pH value between 2.7 and 3.3 to carry out a first leaching reaction, and finally filtering to obtain a nickel sulfate solution. Controlling the pH value of the reaction system between 2.7 and 3.3 allows the leached Fe... 3+Within this pH range, goethite is generated for redeposition, ensuring that nickel is leached in large quantities, iron in small quantities, and copper and aluminum in trace amounts. Simultaneously, it ensures that Fe is produced during leaching. 3+ The rate is slower than Fe 3+ The rate of hydrolysis precipitation can prevent Fe from remaining in the solution. 3+ Excessive concentration generates ferric hydroxide colloid, which reduces nickel entrainment and improves nickel recovery. Furthermore, the generated goethite enhances the leaching of Cu. 2+ It has a certain adsorption effect and can reduce the Cu content in the obtained nickel sulfate solution. 2+ The reduced impurity concentration improves the quality of the recovered nickel products. Furthermore, this recovery method offers advantages such as a short process flow, simple operation, low equipment requirements, and low cost. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a process flow diagram of a method for recovering nickel from nickel-containing waste slag provided in an embodiment of this application. Detailed Implementation

[0014] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0015] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0016] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0017] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0018] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0019] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0020] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0021] The first aspect of this application provides a method for recovering nickel from nickel-containing waste slag, such as... Figure 1 As shown, it includes the following steps:

[0022] S10: Collect nickel-containing waste residue;

[0023] S20: Prepare a slurry by mixing nickel-containing waste residue and water;

[0024] S30: Add the first sulfuric acid solution to the slurry, control the pH value between 2.7 and 3.3 to carry out the first leaching reaction, and then filter to obtain nickel sulfate solution.

[0025] The method for recovering nickel from nickel-containing waste slag provided in this application involves preparing a slurry from the nickel-containing waste slag and water, then adding a first sulfuric acid solution to the slurry, controlling the pH value between 2.7 and 3.3 to carry out a first leaching reaction, and finally filtering to obtain a nickel sulfate solution. Controlling the pH value of the reaction system between 2.7 and 3.3 allows the leached Fe...3+ Within this pH range, goethite is generated for redeposition, ensuring that nickel is leached in large quantities, iron in small quantities, and copper and aluminum in trace amounts. Simultaneously, it ensures that Fe is produced during leaching. 3+ The rate is slower than Fe 3+ The rate of hydrolysis precipitation can prevent Fe from remaining in the solution. 3+ Excessive concentration generates ferric hydroxide colloid, which reduces nickel entrainment and improves nickel recovery. Furthermore, the generated goethite enhances the leaching of Cu. 2+ It has a certain adsorption effect and can reduce the Cu content in the obtained nickel sulfate solution. 2+ The reduced impurity concentration improves the quality of the recovered nickel products. Furthermore, this recovery method offers advantages such as a short process flow, simple operation, low equipment requirements, and low cost.

[0026] In step S10 above, the collected nickel-containing waste residue can be generated during the impurity removal process of hydrometallurgical nickel sulfate production, existing in the form of hydroxides. Specifically, based on 100% of the total weight of the nickel-containing waste residue, it contains: Ni 35.52-37.34%, Cu 0.002-0.004%, Fe 2.43-2.87%, and Al 0.65-0.95%. The collected nickel-containing waste residue generally contains metals such as Ni, Cu, Fe, and Al within the above-mentioned ranges. Through the recovery method of this application embodiment, Ni and Fe metals in the nickel-containing waste residue can be effectively recovered.

[0027] In step S20 above, the method for preparing the slurry from nickel-containing waste residue and water can be as follows: the mass-to-volume ratio of nickel-containing waste residue to water is 1g:(1.0~1.2)mL, for example, 1g:1mL, 1g:1.1mL, 1g:1.2mL, etc. The nickel-containing waste residue and water are added to the reactor and stirred to form a slurry. Specifically, when the mass of nickel-containing waste residue is 1000g, the volume of water can be 1000~1200mL. The mass-to-volume ratio of nickel-containing waste residue to water can be selected according to the concentration of the nickel sulfate solution to be leached.

[0028] In step S30 above, the acidity of the first sulfuric acid solution is 0.63–0.75 N, for example, 0.63 N, 0.65 N, 0.67 N, 0.69 N, 0.71 N, 0.73 N, 0.75 N, etc. The first sulfuric acid solution is added to the slurry, specifically by slowly adding it using a peristaltic pump. This controls the pH of the slurry between 2.7 and 3.3, for example, pH values ​​of 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, and 3.3, which allows the leached Fe... 3+Within this pH range, goethite is formed, allowing for reprecipitation, which reduces Ni entrainment and improves nickel recovery. Furthermore, it allows for control over Fe production during leaching. 3+ The rate is slower than Fe 3+ The rate of hydrolysis precipitation can prevent Fe from remaining in the solution. 3+ Excessive concentration leads to the formation of ferric hydroxide colloid. Therefore, the first leaching reaction of nickel-containing waste slag is carried out under conditions of pH 2.7–3.3 to ensure that a large amount of Ni is leached out, while only a small amount of iron, copper, and aluminum are leached out. Thus, after the first leaching reaction, the nickel recovery rate can reach 85.15–93.36%. The resulting nickel sulfate solution contains Ni at a concentration of 92.66–96.48 g / L, Cu at 0.002–0.008 g / L, Fe at 0.004–0.01 g / L, and Al at 0.005–0.011 g / L. Therefore, the nickel sulfate solution obtained in this application meets the impurity requirements for the product and can be recycled as a nickel sulfate solution product. The reaction formula for the first leaching reaction is as follows:

[0029] Ni(OH)₂ + H₂SO₄ = NiSO₄ + 2H₂O

[0030] 2Fe(OH)3+3H2SO4=Fe2(SO4)3+6H2O,

[0031] Cu(OH)₂ + H₂SO₄ = 2H₂O + CuSO₄

[0032] 2Al(OH)3 + 3H2SO4 ==Al2(SO4) 4)3 +6H2O,

[0033] Fe 3+ +2H₂O=FeOOH+3H + .

[0034] In the embodiments, the conditions for the first leaching reaction include: a stirring speed of 280–320 r / min, such as 280 r / min, 290 r / min, 300 r / min, 310 r / min, 320 r / min, etc., and a temperature of 85–90°C, such as 85°C, 86°C, 87°C, 88°C, 89°C, 90°C, etc. Within this temperature range, Fe is favored. 3+ The formation of goethite (FeOOH) causes Fe to redefine, thereby reducing Ni entrainment, improving nickel recovery, and preventing Fe from remaining in the solution. 3+Excessive concentration leads to the formation of ferric hydroxide colloid, which occurs over a period of 6–8 hours, such as 6h, 6.5h, 7h, 7.5h, or 8h. Within this time range, it is ensured that a large amount of nickel in the nickel-containing waste is leached out to form a nickel sulfate solution, and the Fe in the nickel sulfate solution… 3+ Low concentration, high recovery efficiency.

[0035] In this embodiment, an aging process is included after the first leaching reaction and before the filtration process. Specifically, the aging process can begin after the addition of the first sulfuric acid solution is stopped, and the aging time is 3 to 5 hours. Aging allows Fe to… 3+ H produced by hydrolysis + Re-reacting with some poorly crystalline goethite can reform goethite with a better crystalline form, and goethite can adsorb Cu. 2+ It can reduce the Cu content in nickel sulfate solution. 2+ The impurity concentration is low, making it easy to filter, resulting in high recovery efficiency and a high-quality nickel sulfate solution obtained from filtration.

[0036] After step S30 above, filtration is performed to obtain a nickel sulfate solution and filter residue. The preparation method of this embodiment further includes: mixing the obtained low-nickel filter residue with the second sulfuric acid solution and adjusting the pH to 0.18–0.25, performing a second leaching reaction, and then filtering to obtain a low-nickel solution and hematite slag; wherein the low-nickel solution is used to prepare a slurry with nickel-containing waste residue and water, and the iron content of the hematite slag is 60.57–62.04%. Specifically, the mass-to-volume ratio of the low-nickel filter residue to the second sulfuric acid solution is 1g:(4–5)mL, for example, 1g:4mL, 1g:4.2mL, 1g:4.4mL, 1g:4.6mL, 1g:4.8mL, or 1g:5mL. When the mass of the low-nickel filter residue is 1000g, the volume of the second sulfuric acid solution can be 4000–5000mL.

[0037] In this embodiment, the low-nickel filter residue obtained from step S30 is collected, and the low-nickel filter residue, water, and 98% concentrated sulfuric acid are added to a high-pressure reactor to form a feed solution. The pH of the feed solution is adjusted to 0.18-0.25 to carry out a second leaching reaction. Alternatively, the low-nickel filter residue and the second sulfuric acid solution are added to a high-pressure reactor at a mass-to-volume ratio of 1:(4-5) to form a feed solution. The pH of the feed solution is adjusted to 0.18-0.25 to carry out a second leaching reaction. Then, the solution is filtered to obtain a low-nickel solution and hematite slag. The conditions for the second leaching reaction include: a rotation speed of 270–300 r / min, such as 270 r / min, 275 r / min, 280 r / min, 285 r / min, 290 r / min, 295 r / min, 300 r / min, etc.; an internal pressure of 1.55–1.65 MPa, such as 1.55 MPa, 1.57 MPa, 1.59 MPa, 1.61 MPa, 1.63 MPa, 1.65 MPa, etc.; a temperature of 180–185℃, such as 180℃, 181℃, 182℃, 183℃, 184℃, 185℃; and a time of 5–6 h, such as 5 h, 5.5 h, 6 h, etc. Within the pressure, temperature, and time range of the reactor, nickel in the low-nickel filter residue can be further leached to form a low-concentration nickel sulfate solution. This low-concentration nickel sulfate solution can be returned to step S10 to prepare a slurry with nickel-containing waste residue and water. This not only reduces the amount of water and sulfuric acid used, saving costs, but also further improves the nickel recovery rate from the nickel-containing waste residue. In addition, it is beneficial to convert goethite (FeOOH) into hematite (Fe2O3), which can produce hematite slag by-products with low impurities and high iron content. This reduces the accumulation of solid waste residue, alleviates environmental pressure, realizes resource recycling, and improves economic benefits.

[0038] The following description is based on specific embodiments.

[0039] Example 1

[0040] This embodiment provides a method for recovering nickel from nickel-containing waste slag, including the following steps:

[0041] S11: Provides 1000g of nickel-containing waste slag; wherein the composition and content of the nickel-containing waste slag include: Ni 36%, Cu 0.0036%, Fe 2.67%, Al 0.8%;

[0042] S12: Add nickel-containing waste slag and pure water to the reactor and stir to form a slurry according to the mass-volume ratio of nickel-containing waste slag and water of 1:1.1;

[0043] S13: First, the slurry is stirred using an electric mixer at a speed of 300 r / min, while being heated to 87°C using an electric furnace. Then, a 0.69 mol / L sulfuric acid solution is slowly added to the slurry using a peristaltic pump, while maintaining the pH of the reaction system at 3. The first leaching reaction is carried out for 7 hours. After stopping the addition of sulfuric acid solution, the slurry is aged for 4 hours and then filtered to obtain nickel sulfate solution and low-nickel filter residue. The nickel sulfate solution is used as a nickel product for nickel recovery.

[0044] S14: Add low-nickel filter residue and sulfuric acid solution to a high-pressure reactor at a mass-to-volume ratio of 1g:4.5mL, adjust the pH of the solution to 0.21, set the stirring speed to 280r / min, heat to 182℃, introduce compressed air to make the pressure inside the reactor 1.6MPa, and carry out the second leaching reaction for 5.5h. After filtration, obtain low-nickel solution and hematite slag. The low-nickel solution is used to return to step S20 to prepare slurry with nickel-containing waste residue and water.

[0045] Upon testing, the nickel sulfate solution obtained in step S13 had a nickel concentration of 93.79 g / L, a Cu concentration of 0.002 g / L, a Fe concentration of 0.004 g / L, and an Al concentration of 0.007 g / L, which met the impurity requirements for the product and could be used as a nickel sulfate solution product; the nickel recovery rate was 91.67%; the hematite slag obtained in step S14 had a nickel content of 0.41% and an iron content of 60.57%, and the hematite slag was identified as hematite by XRD and could be sold as a by-product.

[0046] Example 2

[0047] This embodiment provides a method for recovering nickel from nickel-containing waste slag, including the following steps:

[0048] S21: Provides 1000g of nickel-containing waste residue; wherein the composition and content of the nickel-containing waste residue include: Ni 35.52%, Cu 0.002%, Fe 2.43%, Al 0.65%;

[0049] S22: Add nickel-containing waste slag and pure water into the reactor and stir to form a slurry, according to a mass-volume ratio of 1:1 for nickel-containing waste slag and water.

[0050] S23: First, the slurry is stirred using an electric mixer at a speed of 280 r / min, while being heated to 85℃ using an electric furnace. Then, a 0.63 mol / L sulfuric acid solution is slowly added to the slurry using a peristaltic pump, while maintaining the pH of the reaction system at 2.7. The first leaching reaction is carried out for 6 hours. After stopping the addition of sulfuric acid solution, the slurry is aged for 3 hours and then filtered to obtain nickel sulfate solution and low-nickel filter residue. The nickel sulfate solution is used as a nickel product for nickel recovery.

[0051] S24: Add low-nickel filter residue and sulfuric acid solution to a high-pressure reactor at a mass-to-volume ratio of 1g:4mL, adjust the pH of the solution to 0.18, set the stirring speed to 270r / min, heat to 180℃, introduce compressed air to make the pressure inside the reactor 1.55MPa, and carry out the second leaching reaction for 5h. After filtration, obtain low-nickel solution and hematite slag. The low-nickel solution is used to return to step S20 to prepare slurry with nickel-containing waste residue and water.

[0052] Upon testing, the nickel sulfate solution obtained in step S23 had a nickel concentration of 95.38 g / L, a Cu concentration of 0.002 g / L, a Fe concentration of 0.004 g / L, and an Al concentration of 0.005 g / L, meeting the impurity requirements for the product and thus suitable as a nickel sulfate solution product; the nickel recovery rate was 93.36%; the hematite slag obtained in step S24 had a nickel content of 0.37% and an iron content of 61.89%, and the hematite slag was identified as hematite by XRD and can be sold as a by-product.

[0053] Example 3

[0054] This embodiment provides a method for recovering nickel from nickel-containing waste slag, including the following steps:

[0055] S31: Provides 1000g of nickel-containing waste residue; wherein the composition and content of the nickel-containing waste residue include: Ni 37.34%, Cu 0.004%, Fe 2.87%, Al 0.95%;

[0056] S32: Add nickel-containing waste slag and pure water to the reactor and stir to form a slurry according to the mass-volume ratio of nickel-containing waste slag and water of 1:1.2;

[0057] S33: First, the slurry is stirred using an electric mixer at a speed of 320 r / min, while being heated to 90℃ using an electric furnace. Then, a 0.75 mol / L sulfuric acid solution is slowly added to the slurry using a peristaltic pump, while maintaining the pH of the reaction system at 3.3. The first leaching reaction is carried out for 8 hours. After stopping the addition of sulfuric acid solution, the slurry is aged for 5 hours and then filtered to obtain nickel sulfate solution and low-nickel filter residue. The nickel sulfate solution is used as a nickel product for nickel recovery.

[0058] S34: Add low-nickel filter residue and sulfuric acid solution to a high-pressure reactor at a mass-to-volume ratio of 1g:5mL, adjust the pH of the solution to 0.25, set the stirring speed to 300r / min, heat to 185℃, introduce compressed air to make the pressure inside the reactor 1.65MPa, and carry out the second leaching reaction for 6h. After filtration, obtain low-nickel solution and hematite slag. The low-nickel solution is used to return to step S20 to prepare slurry with nickel-containing waste residue and water.

[0059] Upon testing, the nickel sulfate solution obtained in step S33 had a nickel concentration of 96.48 g / L, a Cu concentration of 0.002 g / L, a Fe concentration of 0.004 g / L, and an Al concentration of 0.006 g / L, which met the impurity requirements for the product and could be used as a nickel sulfate solution product; the nickel recovery rate was 87.76%; the hematite slag obtained in step S34 had a nickel content of 0.34% and an iron content of 62.1%, and the hematite slag was identified as hematite by XRD and could be sold as a by-product.

[0060] As shown in Examples 1-3 above, the nickel recovery rate in Example 2 reached as high as 93.36%. In this example, the first leaching reaction was carried out by controlling the pH value of the reaction system to 2.7, indicating that under this pH condition, the leaching amount of nickel in the nickel-containing waste slag was the largest, and the nickel recovery rate was the highest. In the nickel sulfate solution obtained in step S3 of Examples 1-3, the Fe concentration was 0.004 g / L, indicating that controlling the pH value of the reaction system between 2.7 and 3.3 can maximize the leaching of Fe. 3+ The ore is redeposited to form goethite, while leaching produces Fe. 3+ The rate is slower than Fe 3+ The rate of hydrolysis precipitation can prevent Fe from remaining in the solution. 3+ Excessive concentration will generate ferric hydroxide colloid. Therefore, the first leaching reaction of nickel-containing waste slag under the condition of pH value of 2.7 to 3.3 not only results in a high nickel recovery rate, but also in fewer impurities in the recovered nickel sulfate solution, resulting in a good product quality.

[0061] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for recovering nickel from nickel-containing waste slag, characterized in that, Includes the following steps: Collect nickel-containing waste slag; wherein, the nickel-containing waste slag is generated during the impurity removal process of hydrometallurgical production of nickel sulfate, exists in the form of hydroxide, and, based on 100% of the total weight of the nickel-containing waste slag, contains: Ni 35.52~37.34%, Cu 0.002~0.004%, Fe 2.43~2.87%, and Al 0.65~0.95%; The nickel-containing waste residue and water are mixed to form a slurry; A first sulfuric acid solution is added to the slurry, and the pH value is controlled between 2.7 and 3.3 to carry out the first leaching reaction. Then, the solution is filtered to obtain a nickel sulfate solution. The method for recovering nickel further includes: adding the filter residue and the second sulfuric acid solution to a high-pressure reactor, mixing them, adjusting the pH to 0.18-0.25, carrying out a second leaching reaction, and then filtering to obtain a low-nickel solution and hematite slag; the low-nickel solution is used to prepare the slurry with the nickel-containing waste residue and water; wherein the conditions for the second leaching reaction include: a stirring speed of 270-300 r / min, a reactor pressure of 1.55-1.65 MPa, a temperature of 180-185℃, a time of 5-6 h, and a mass-to-volume ratio of the filter residue to the second sulfuric acid solution of 1 g: (4-5) mL.

2. The method for recovering nickel from nickel-containing waste slag as described in claim 1, characterized in that, The mass-to-volume ratio of the nickel-containing waste residue to the water is 1 g: (1.0~1.2) mL.

3. The method for recovering nickel from nickel-containing waste slag as described in claim 1, characterized in that, The acidity of the first sulfuric acid solution is 0.63~0.75N.

4. The method for recovering nickel from nickel-containing waste slag as described in any one of claims 1 to 3, characterized in that, The conditions for the first leaching reaction include: a stirring speed of 280~320 r / min, a temperature of 85~90℃, and a time of 6~8 h.

5. The method for recovering nickel from nickel-containing waste slag as described in any one of claims 1 to 3, characterized in that, An aging process is included after the first leaching reaction step and before the filtration process step.

6. The method for recovering nickel from nickel-containing waste slag as described in claim 1, characterized in that, The iron content of the hematite slag is 60.57-62.04%.

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