Method for purifying nickel-cobalt solution by using nickel-cobalt hydroxide raw material

Abstract

The present application belongs to the field of hydrometallurgy or chemical technology, and particularly relates to a method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw material, which comprises steps of leaching, removing iron and aluminum, removing calcium and magnesium, removing silicon and removing copper and zinc. The direct yield of nickel-cobalt-scandium is greatly improved by using reduction leaching instead of direct leaching with sulfuric acid; NH4F is used as a reagent for removing calcium and magnesium, and the removal rate of calcium and magnesium is high, and the reaction time is short; the third filtrate after removing calcium and magnesium is subjected to flocculation and silicon removal, so that the silicon content is reduced, the problem of intermediate phase in the subsequent extraction process is solved, the method of removing silicon by using polyferric sulfate is easy to operate, the index is stable, and the price is low, and no new impurities are brought into the system; zinc is removed by using hydrogen sulfide, so that the depth of Zn removal can reach below 1 mg / L, and because the precipitation is in an acidic condition, the residue contains low nickel. The method adopted in the present application has simple process, is easy to operate, has high separation efficiency, and has excellent index.

Description

Technical Field

[0001] This invention belongs to the field of hydrometallurgy or chemical technology, and specifically relates to a method for preparing a purified nickel-cobalt solution from nickel-cobalt hydroxide raw materials. Background Technology

[0002] Nickel-cobalt hydroxide (MCH) is a nickel intermediate produced from laterite nickel ore using high-pressure acid leaching (HP AL) technology. It is commonly used to manufacture nickel sulfate, and as a key element in the cathode material of ternary lithium batteries, coupled with the increasing prevalence and development of high-nickel batteries, nickel sulfate has a large future market potential, simultaneously driving demand for MHP raw materials. However, MHC contains impurities other than nickel and cobalt, such as iron, aluminum, manganese, magnesium, and silicon. Current processing methods involve dissolving and extracting the nickel-cobalt hydroxide material to remove impurities before reuse. However, in the production process of MHC from laterite nickel ore, the pH of the impurity removal solution is adjusted to 5.0-5.2 or higher to remove iron and aluminum, resulting in a large amount of nickel precipitation and reducing nickel recovery rate; this process is not properly recycled. Furthermore, laterite nickel ore has a high soluble silicon content. When using the leaching-extraction process, the silicon dioxide is dissolved in the form of silicic acid. During the extraction of the leaching solution, the silicic acid in the solution forms a large amount of interphase contaminants. These interphase contaminants can cause difficulties in extraction and back-extraction phase separation, resulting in phase entrainment and disrupting the extraction production. In severe cases, this can lead to production stoppage. Silicon removal is the biggest challenge in the wet leaching process.

[0003] Various processing techniques have been proposed in the prior art. Patent CN104480306A discloses a method for treating hydrochloric acid leaching solution of zinc-containing nickel-cobalt hydroxide material. The process includes: extracting the hydrochloric acid leaching solution of zinc-containing nickel-cobalt hydroxide material with N235 extraction solution; after washing nickel and back-extracting cobalt, the organic phase loaded with zinc is added to an ammoniacal back-extraction solution for zinc back-extraction; separating the aqueous phase and organic phase loaded with zinc; the ammoniacal back-extraction zinc solution is recycled after treatment, and the accumulated zinc can be opened in the form of zinc slag. Ammonium ions and chloride ions brought in by the organic phase will form ammonium chloride crystals, which are opened by filtration. The process is fast in phase separation, does not have any impact on the organic phase, and there is no wastewater discharge. Patent CN112779419A discloses a method for removing iron, aluminum, and silicon from a nickel-cobalt-manganese-copper solution under normal pressure. The method involves taking crude nickel-cobalt-manganese-copper raw material, mixing it with water to form a slurry, adding acid and a reducing agent for leaching, with the leaching endpoint pH ≤ 2.5. After thickening and separation, the supernatant and precipitant are added concurrently to a nickel-cobalt-manganese-copper solution containing iron, aluminum, and silicon removed at 70-100℃ and kept at this temperature. The precipitant is crude nickel-cobalt-manganese-copper raw material with a solid content of 1-50%, and the pH for iron, aluminum, and silicon removal is 3.0-4.0. The slurry undergoes solid-liquid separation, the filtrate is used as the extraction stock solution, and the iron, aluminum, and silicon removed slag and leaching residue are mixed with water to prepare a slurry with a solid content ≤ 50%. Acid is added to adjust the pH to 2.0-3.5, and a reducing agent is added to reduce the Fe content. 2+ ≥0.1g / L, after solid-liquid separation, iron, aluminum, and silicon-removed slag and filtrate are obtained. The filtrate is sent to the leaching section for raw material leaching. This method does not require the use of auxiliary materials, hazardous chemicals, or the introduction of other elements in the removal of iron, aluminum, and silicon. However, it cannot remove impurities such as iron, aluminum, calcium, magnesium, silicon, copper, and zinc from the ore.

[0004] Therefore, the method for preparing purified nickel-cobalt solutions using nickel-cobalt hydroxide raw materials still needs further improvement. Summary of the Invention

[0005] To solve, or at least partially solve, the above-mentioned technical problems, the present invention proposes a method for preparing a purified nickel-cobalt solution from nickel-cobalt hydroxide raw materials, the method comprising the following steps:

[0006] Leaching: The nickel-cobalt hydroxide is leached, reduced, and separated to obtain the first filtrate and the first filter residue;

[0007] Iron and aluminum removal: Neutralizing agent is added to the first filtrate to adjust the pH to a fixed value and then oxidized. After oxidation, the reaction solution is separated into solid and liquid to obtain the second filtrate and iron and aluminum slag.

[0008] Calcium and magnesium removal: The second filtrate is mixed with NH4F and reacted to obtain the third filtrate and calcium and magnesium slag;

[0009] Desiliconization: The third filtrate and ferric polysulfate are mixed and stirred to obtain silicon slag and desiliconized filtrate;

[0010] Copper and zinc removal: Hydrogen sulfide is introduced into the desilication filtrate, and the precipitate is dissolved by stirring. After the reaction is completed, the solution is filtered by pressure to obtain a purified nickel-cobalt solution.

[0011] Furthermore, the process of leaching and reducing nickel-cobalt hydroxide to obtain the first filtrate and the first filter residue specifically includes the following steps:

[0012] The nickel-cobalt hydroxide raw material is made into a slurry;

[0013] Concentrated sulfuric acid is injected into the slurry, and after stirring for 0.2-0.5 hours, dilute sulfuric acid is added dropwise to adjust the pH to 1.2-2.5.

[0014] After stirring for 1-2 hours, add the reducing agent and react for 0.5-1 hours to obtain the first reaction solution;

[0015] The first reaction solution is subjected to solid-liquid separation to obtain a first filtrate and a first filter residue.

[0016] Furthermore, the stirring speed during the process of obtaining the first filtrate and the first filter residue is 300-800 r / min.

[0017] The liquid-to-solid ratio in the slurry is 3-7:1;

[0018] The concentration of the dilute sulfuric acid is 10-40 wt%.

[0019] The amount of concentrated sulfuric acid added is 600-900 kg / t. 干矿料 ;

[0020] The reducing agent is one of H2O2, SO2, and Na2SO3; the amount of reducing agent used per mol of Mn in the mineral is 0.2-1 mol / mol.

[0021] Furthermore, the neutralizing agent used in the process of obtaining the second filtrate and iron-aluminum slag is Na2CO3, which is added after being prepared into a slurry with a solid content of 30-50%.

[0022] The pH value is fixed at 4.5-5.4, and the oxidation time is 3-5 hours.

[0023] Furthermore, the reaction conditions for the second filtrate with NH4F are as follows: reaction at 60-80°C for 0.5-1 h;

[0024] Wherein, the dosage coefficient of NH4F It is 1-3 mol / mol.

[0025] Further, the mixing and stirring of the third filtrate and ferric polysulfate specifically involves:

[0026] The third filtrate was mixed with ferric polysulfate and stirred at 40-60°C for 0.5-2 hours.

[0027] The dosage coefficient of the polyferric sulfate, PFS / SiO2, is 80-120 wt% / wt%.

[0028] Furthermore, during the mixing and stirring of the third filtrate and polyferric sulfate: after the pH drops following the addition of polyferric sulfate, 90-98 wt% NaOH solution is added to adjust the pH to 4.5-5.0 within 8 minutes and maintain it unchanged.

[0029] Furthermore, the hydrogen sulfide is obtained by the following method:

[0030] Add sodium sulfide solution to the hydrogen sulfide generator;

[0031] The sulfuric acid solution is then pumped into the hydrogen sulfide generator to produce hydrogen sulfide.

[0032] The sodium sulfide concentration is 60-80 g / L, and the sulfuric acid solution concentration is 230-280 g / L.

[0033] Furthermore, the sodium sulfide solution and sulfuric acid solution are added as follows: in the first 0.5 hours, the H2SO4 / Na2S ratio is 1:2 mol / mol, and in the next 1.5 hours, the H2SO4 / Na2S ratio is 1:2 mol / mol, and the solution is added within 1.5 hours.

[0034] Furthermore, the method also includes: removing hydrogen sulfide gas from the purified nickel-cobalt solution using compressed air bubbling.

[0035] The beneficial effects of this invention are:

[0036] This invention uses reduction leaching instead of direct sulfuric acid leaching, which greatly improves the direct recovery rate of nickel, cobalt, and scandium.

[0037] This invention uses NH4F as a calcium and magnesium removal reagent, which has a high calcium and magnesium removal rate and a short reaction time;

[0038] This invention uses flocculation to remove silicon from the third filtrate after calcium and magnesium removal, which can reduce its silicon content and solve the problem of intermediate phase in the subsequent extraction process. At the same time, the polyferric sulfate method for silicon removal is easy to operate, has stable indicators, is inexpensive, and will not introduce new impurities into the system.

[0039] The present invention uses hydrogen sulfide precipitation to remove zinc, which can achieve a Zn removal depth of less than 1 mg / L, and due to precipitation under acidic conditions, the slag has a low nickel content.

[0040] The method and process used in this invention are simple, easy to operate, have high separation efficiency, and excellent performance indicators.

[0041] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0042] 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.

[0043] Figure 1 A flowchart of the method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw materials proposed in this invention is shown;

[0044] Figure 2 A detailed flowchart of the method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw materials proposed in this embodiment of the invention is shown. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0046] This invention proposes a method for preparing a purified nickel-cobalt solution from nickel-cobalt hydroxide raw materials. First, nickel-cobalt hydroxide is leached with sulfuric acid to extract nickel, cobalt, and other elements. Then, the leached slurry is neutralized with Na₂CO₃ to a specific pH, causing iron, aluminum, and other elements to precipitate as iron-aluminum slag. After filtration, a nickel-cobalt solution and the iron-aluminum slag are obtained, thus separating nickel-cobalt from iron and aluminum. Following calcium, magnesium, silicon, copper, and zinc removal processes, a purified nickel-cobalt-manganese solution is obtained. The concentrations are: Ca, Mg < 30 mg / L, Cu, Zn < 1 mg / L, and Si < 30 mg / L. This is a simple, easy-to-operate, high-performance, and low-cost process for preparing a ternary nickel-cobalt-manganese solution. Specific steps are as follows: Figure 1 As shown:

[0047] Specifically, the following steps are included:

[0048] Leaching: The nickel-cobalt hydroxide is leached, reduced, and separated to obtain the first filtrate and the first filter residue;

[0049] Specifically:

[0050] The nickel-cobalt hydroxide raw material is made into a slurry with a liquid-to-solid ratio of 3-7:1, that is, the ratio of the nickel-cobalt hydroxide raw material to the added liquid (water + acid) in the slurry is 3-7:1.

[0051] Concentrated sulfuric acid is injected into the slurry at a rate of 600-900 kg / t of dry ore, i.e., 600-900 kg of concentrated sulfuric acid is added to every 1 t of nickel-cobalt hydroxide. After stirring at a speed of 300-800 r / min for 0.2-0.5 h, 10-40 wt% dilute sulfuric acid is added dropwise to adjust the pH to 1.2-2.5.

[0052] After stirring for 1-2 hours, a reducing agent is added and reacted for 0.5-1 hours to obtain the first reaction solution. The reducing agent is one of H2O2, SO2, or Na2SO3. The amount of reducing agent is based on the Mn content in the ore, and the ratio of reducing agent amount to Mn content in the ore is 0.2-1 mol / mol. That is, for every 1 mol of Mn in the nickel-cobalt hydroxide raw material, 0.2-1 mol of reducing agent is added.

[0053] The first reaction solution is subjected to solid-liquid separation to obtain a first filtrate and a first filter residue.

[0054] Iron and aluminum removal: Add neutralizing agent Na2CO3 to the first filtrate to adjust the pH to a fixed value of 4.5-5.4, and oxidize for 3-5 hours. After oxidation, the reaction solution is separated into solid and liquid to obtain the second filtrate and iron and aluminum slag. Na2CO3 needs to be prepared into a slurry with a solid content (i.e., the solid content in the slurry) of 30-50% before being added.

[0055] Calcium and magnesium removal: The second filtrate is mixed with NH4F and reacted at 60-80℃ for 0.5-1h to obtain the third filtrate and calcium and magnesium slag; wherein the dosage coefficient of NH4F is... It is 1-3 mol / mol.

[0056] Silicon removal: The third filtrate and polyferric sulfate are stirred at 40-60℃ for 0.5-2h to obtain silicon slag and desiliconized filtrate; wherein, the amount of polyferric sulfate is based on the SiO2 content in the third filtrate, and the coefficient PFS / SiO2 is 80-120wt% / wt%; after the pH drops after the addition of polyferric sulfate, 90-98wt% NaOH solution is added to adjust the pH to 4.5-5.0 within 8min and maintain it unchanged.

[0057] Copper and zinc removal: Hydrogen sulfide is introduced into the desilication filtrate, the precipitate is dissolved by stirring, and after the reaction is completed, the solution is filtered by pressure to obtain a purified nickel-cobalt solution;

[0058] Specifically:

[0059] The desiliconized filtrate is pumped into a copper and zinc removal tank, heated to 40-60°C, and sulfuric acid is added to adjust the pH to 2-3.

[0060] Add sodium sulfide solution to the hydrogen sulfide generator in the copper and zinc removal process. The concentration of sodium sulfide solution is 60-80 g / L.

[0061] The sulfuric acid solution is then pumped into the hydrogen sulfide generator at a certain rate. The generated hydrogen sulfide is then passed into a copper-zinc removal tank, stirred to dissolve the precipitate, and the reaction time is 1.5-2.5 hours. After the copper-zinc removal is completed, the solution is filtered to obtain a purified nickel-cobalt solution.

[0062] The sodium sulfide solution and sulfuric acid solution are added as follows: in the first 0.5 hours, the solution is added at a ratio of H2SO4 / Na2S of 1:2 mol / mol, and in the next 1.5 hours, the solution is added within 1.5 hours at a ratio of H2SO4 / Na2S of 1:2 mol / mol.

[0063] During the copper and zinc removal process, it is necessary to check all interfaces for H2S gas leaks. The inspection methods include lead acetate test paper and hydrogen sulfide detectors, with an alarm limit of 10 ppm. The obtained purified nickel-cobalt solution is bubbled with compressed air to remove H2S, and the exhaust gas is discharged outdoors through an exhaust hood. Copper sulfate solution is used to treat residual hydrogen sulfide gas in the hydrogen sulfide generator and the copper-zinc removal tank.

[0064] The following describes specific embodiments and Figure 2 The above methods and reaction conditions for each step are described in detail. The main steps include leaching, removal of iron and aluminum, removal of calcium and magnesium, removal of silicon, and removal of copper and zinc.

[0065] Example 1

[0066] Leaching: First, the nickel-cobalt hydroxide raw material is prepared into a slurry. Concentrated sulfuric acid is injected into the slurry to dissolve it, with an acid-to-ore ratio of 800 kg / t. The mixture is stirred for 0.5 h at a reaction temperature of 80 °C. 30 wt% dilute sulfuric acid is added dropwise to adjust the pH to 1.5, and stirring continues for another 1.5 h. Then, the reducing agent H₂O₂ is added, and the reaction is continued for 0.5 h. Finally, solid-liquid separation is performed to obtain the first filtrate and the first filter residue.

[0067] Iron and aluminum removal: Neutralizing agent Na2CO3 was added to the first filtrate to adjust the pH to 5.2. The reaction temperature was 80℃, and the reaction was carried out for 4 hours. After solid-liquid separation, iron and aluminum slag and the second filtrate were obtained.

[0068] Calcium and magnesium removal: The second filtrate from the iron and aluminum removal process is mixed with NH4F and stirred for 0.5 hours at a reaction temperature of 70°C. The NH4F dosage coefficient is... The concentration was 2 mol / mol. Solid-liquid separation was then performed to obtain the third filtrate and calcium-magnesium slag.

[0069] Silicon removal: The third filtrate from the calcium and magnesium removal process is mixed with polyferric sulfate (PFS) and stirred for 1 hour at a reaction temperature of 50°C. The polyferric sulfate dosage coefficient (PFS / SiO2) is 100 wt% / wt%. Solid-liquid separation is then performed to obtain silicon slag and desiliconized filtrate.

[0070] Copper-zinc removal: The desiliconized filtrate obtained from the desiliconization process is pumped into the copper-zinc removal tank and heated to 50°C. Sulfuric acid is added to adjust the pH to 2.5. Sodium sulfide solution with a concentration of 70 g / L is added to the hydrogen sulfide generator in the copper-zinc removal process. Then, sulfuric acid solution is pumped into the hydrogen sulfide generation tank at a certain rate. The sulfuric acid solution is added at a rate of H₂SO₄ / Na₂S of 1:2 mol / mol over 0.5 h, followed by H₂SO₄ / Na₂S at the same rate over 1.5 h, with a sulfuric acid concentration of 250 g / L. The generated hydrogen sulfide is then passed into the copper-zinc removal tank, stirred to dissolve the precipitate, and reacted for 2 h. After copper-zinc removal is complete, the solution is filtered under pressure to obtain a purified nickel-cobalt solution.

[0071] The leaching rates of nickel, cobalt, and manganese during the leaching and iron and aluminum removal processes are shown in Table 1: Ni 91%-94%, Co 89%-90%, Mn 67%-68%.

[0072] Table 1. Leaching results of nickel, cobalt, and manganese during the leaching and iron / aluminum removal process.

[0073]

[0074] The purification depth results of the purification process (purification of nickel-cobalt-manganese solution after removing copper and zinc) are shown in Table 2. Ca and Mg < 30 mg / L, SiO2 < 30 mg / L, Cu and Zn < 1 mg / L.

[0075] Table 2. Results of purification depth of nickel-cobalt solution

[0076]

[0077] Example 2

[0078] Unlike Example 1, the acid-to-ore ratio in the reduction leaching step was 600 kg / t, while all other conditions remained unchanged. The leaching results for nickel, cobalt, and manganese during the iron and aluminum removal process are shown in Table 3.

[0079] Table 3. Leaching results of nickel, cobalt, and manganese during the leaching and iron / aluminum removal process.

[0080]

[0081] Example 3

[0082] Unlike Example 1, the pH was adjusted to 4.5 in the iron and aluminum removal step, while all other conditions remained unchanged. The leaching results for nickel, cobalt, and manganese during the iron and aluminum removal process are shown in Table 4.

[0083] Table 4. Leaching results of nickel, cobalt, and manganese during the leaching and iron / aluminum removal process.

[0084]

[0085] Example 4

[0086] The difference from Example 1 is the dosage coefficient of NH4F in the calcium and magnesium removal step. The concentration was 3 mol / mol, and the operation was carried out under the same conditions. The leaching results of the third filtrate in the calcium and magnesium removal process are shown in Table 5:

[0087] Table 5. Leaching results of the third filtrate during the calcium and magnesium removal process.

[0088]

[0089] Example 5

[0090] Unlike Example 1, the reaction time in the copper-zinc step was 1.5 hours, while all other conditions remained unchanged. The leaching results for nickel, cobalt, and manganese are shown in Table 6.

[0091] Table 6. Results of purification depth of nickel-cobalt solution

[0092]

[0093] Comparative Example 1

[0094] Unlike Example 1, the acid-to-ore ratio in the reduction leaching step was 400 kg / t, while all other conditions remained unchanged. The leaching results for nickel, cobalt, and manganese during the iron and aluminum removal process are shown in Table 7.

[0095] Table 7. Leaching results of nickel, cobalt, and manganese during the leaching and iron / aluminum removal process.

[0096]

[0097]

[0098] Comparative Example 2

[0099] The difference from Example 1 is the dosage coefficient of NH4F in the calcium and magnesium removal step. The concentration was 0.5 mol / mol, and the operation was carried out under the same conditions. The leaching results of the third filtrate in the calcium and magnesium removal process are shown in Table 8:

[0100] Table 8. Leaching results of the third filtrate during the calcium and magnesium removal process.

[0101]

[0102] Comparative Example 3

[0103] Unlike Example 1, the reaction time in the copper-zinc step was 0.5 h, while all other conditions remained unchanged. The leaching results for nickel, cobalt, and manganese are shown in Table 9.

[0104] Table 9. Results of purification depth of nickel-cobalt solution

[0105]

[0106] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a purified nickel-cobalt solution from a nickel-cobalt hydroxide raw material, characterized in that, The method includes the following steps: Leaching: The nickel-cobalt hydroxide is leached, reduced, and separated to obtain a first filtrate and a first filter residue; this includes: preparing the nickel-cobalt hydroxide raw material into a slurry; injecting concentrated sulfuric acid into the slurry, stirring for 0.2-0.5 hours, then adding dilute sulfuric acid dropwise to adjust the pH to 1.2-2.5; stirring for 1-2 hours, then adding a reducing agent and reacting for 0.5-1 hours to obtain a first reaction solution; and performing solid-liquid separation on the first reaction solution to obtain a first filtrate and a first filter residue; the amount of concentrated sulfuric acid added is 600-900 kg / t. 干矿料 The amount of reducing agent used per mol of Mn in the ore is 0.2-1 mol / mol. Iron and aluminum removal: Neutralizing agent is added to the first filtrate to adjust the pH to a fixed value before oxidation. After oxidation, the reaction solution is separated into solid and liquid components to obtain the second filtrate and iron and aluminum slag. The fixed pH value is 4.5-5.

4. Calcium and magnesium removal: The second filtrate is mixed with NH4F and reacted to obtain the third filtrate and calcium and magnesium slag; the reaction conditions for the second filtrate and NH4F are 60-80℃ for 0.5-1h. Desiliconization: The third filtrate and ferric polysulfate are mixed and stirred to obtain silicon slag and desiliconized filtrate; Removal of copper and zinc: Hydrogen sulfide is introduced into the desilication filtrate, the precipitate is dissolved by stirring, and after the reaction is completed, the purified nickel-cobalt solution is obtained by pressure filtration.

2. The method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw materials according to claim 1, characterized in that, The stirring speed during the process of obtaining the first filtrate and the first filter residue is 300-800 r / min. The liquid-to-solid ratio in the slurry is 3-7:1; The concentration of the dilute sulfuric acid is 10-40 wt%; The reducing agent is one of H2O2, SO2, or Na2SO3.

3. The method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw material according to claim 1, characterized in that, The neutralizing agent used in the process of obtaining the second filtrate and iron-aluminum slag is Na2CO3, which is added after being prepared into a slurry with a solid content of 30-50%. The oxidation time is 3-5 hours.

4. The method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw materials according to claim 1, characterized in that, The dosage coefficient of NH4F It is 1-3 mol / mol.

5. The method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw material according to claim 1, characterized in that, The specific steps for mixing and stirring the third filtrate and ferric polysulfate are as follows: The third filtrate was mixed with ferric polysulfate and stirred at 40-60°C for 0.5-2 hours. The dosage coefficient of the polyferric sulfate, PFS / SiO2, is 80-120 wt% / wt.

6. The method for preparing purified nickel-cobalt solution from cobalt hydroxide raw material according to claim 1 or 5, characterized in that, During the mixing and stirring of the third filtrate and polyferric sulfate: after the pH drops after the addition of polyferric sulfate, add 90-98wt% NaOH solution to adjust the pH to 4.5-5.0 within 8 minutes and maintain it unchanged.

7. The method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw material according to claim 1, characterized in that, The hydrogen sulfide is obtained by the following method: Add sodium sulfide solution to the hydrogen sulfide generator; The sulfuric acid solution is then pumped into the hydrogen sulfide generator to produce hydrogen sulfide. The sodium sulfide concentration is 60-80 g / L, and the sulfuric acid solution concentration is 230-280 g / L.

8. The method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw material according to claim 7, characterized in that, The sodium sulfide solution and sulfuric acid solution are added as follows: in the first 0.5 hours, the solution is added at a ratio of 1:2 mol / mol for H2SO4 / Na2S, and in the next 1.5 hours, the solution is added at a ratio of 1:2 mol / mol.

9. The method for preparing purified nickel-cobalt solution from nickel-cobalt hydroxide raw material according to claim 1, characterized in that, The method further includes: removing hydrogen sulfide gas from the purified nickel-cobalt solution using compressed air bubbling.

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