A method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder

Abstract

This invention discloses a method for producing MnSO4-FeSO4 mixed crystals with a controllable manganese-iron atomic ratio using reduced mineral powder. This method allows new energy material companies to control raw materials and ensure product quality stability. The technology for producing MnSO4-FeSO4 mixed crystals with a controllable manganese-iron atomic ratio is of great significance for the production of lithium manganese iron phosphate products.

Description

[Technical Field]

[0001] This invention relates to the field of lithium manganese iron phosphate technology, specifically to a method for producing MnSO4-FeSO4 mixed crystals with a controllable manganese-iron atomic ratio using reduced mineral powder. [Background Technology]

[0002] Lithium manganese iron phosphate (LFP) is a product of the blending of lithium iron phosphate (LFP) and lithium manganese phosphate (LMP). It shares the same structure as LFP, both being ordered and regular olivine-type structures. LFP possesses the same advantages as LFP: low cost, high safety performance, high thermal stability, no spontaneous combustion after needle penetration or overcharging, long lifespan, and no risk of explosion. It combines the advantages of both LFP and LMP, overcoming the low energy density of LFP, and is therefore hailed as an "upgraded version of LFP."

[0003] There are already relevant studies, such as Chinese patent application 201510001254.X, which describes a method for preparing lithium iron manganese phosphate (LMP) cathode material for lithium-ion batteries. This method uses manganese and iron source compounds as raw materials, prepares manganese-rich and manganese-poor solutions respectively, and synthesizes gradient-structured LMP precursors by co-precipitation method by controlling the sample addition rate. Then, lithium doping and high-temperature calcination are performed to prepare gradient-structured LMP, where the manganese content gradually decreases and the iron content gradually increases along the particle radius. The resulting LMP cathode material with gradient structure has the characteristics of high energy density, good cycle performance, and excellent rate performance, making it suitable for lithium-ion power battery applications.

[0004] MnSO4 and FeSO4 are the basic materials for lithium iron phosphate (LFP), the cathode material for manganese-based power lithium batteries. Iron and manganese ions have similar radii, easily forming solid solutions during the synthesis of LFP, thus achieving atomic-level mixing. On the one hand, increasing the proportion of manganese ions in LFP can improve the battery's voltage and energy density, but it also introduces numerous defects and porosity. These defects and porosity can potentially prolong lithium ion insertion and extraction, reducing ion migration rates and thus degrading battery cycle performance. On the other hand, increasing the iron content can improve the conductivity and rate performance of lithium batteries; however, excessive iron doping limits the voltage improvement effect of LFP. In other words, different manganese-iron atomic ratios in LFP lead to differences in electrochemical performance. [Summary of the Invention]

[0005] Currently, there are no reports on the production of MnSO4-FeSO4 mixed crystals with a controllable manganese-iron atomic ratio using reduced ore powder, and related technologies need further development. This invention provides a method for producing MnSO4-FeSO4 mixed crystals with a controllable manganese-iron atomic ratio using reduced ore powder. Using reduced ore powder to produce MnSO4-FeSO4 mixed crystals with a controllable manganese-iron atomic ratio is beneficial for new energy material companies to control raw materials and ensure product quality stability. The technology for producing MnSO4-FeSO4 mixed crystals with a controllable manganese-iron atomic ratio is of great significance for the production of lithium manganese iron phosphate products.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] The technical solution of this invention uses reduced ore powder as the main raw material. The reduced ore powder is mixed with water to form a slurry, then leached with concentrated sulfuric acid. Reduced iron powder is then added to remove Fe from the leaching solution. 3+ Reduced to Fe 2+ A mixed slurry of MnSO4-FeSO4 was obtained. Then, calcium carbonate was added to remove impurities, and concentrated sulfuric acid was used to absorb water and crystallize to remove impurities. Then, low-calcium reduced iron powder with Ca≤1000ppm was added to adjust the pH to 3.0-4.0, and FeSO4·7H2O was added. Finally, high-temperature crystallization was carried out to obtain mixed crystals of MnSO4-FeSO4 with controllable manganese-iron atomic ratio.

[0008] A method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder includes the following steps:

[0009] 1) Pulping: Add 300-mesh reduced mineral powder and water to a mixing tank at a solid-liquid mass ratio of 1:4 to obtain a slurry;

[0010] 2) While stirring the slurry obtained in the above step, add concentrated sulfuric acid with a mass content of 98% dropwise, and carry out the leaching reaction at 50℃-60℃. The amount of concentrated sulfuric acid added is 1.4:1 acid-ore ratio, and the leaching time is 2 hours. After the reaction is completed, the leaching slurry is obtained.

[0011] 3) Add reduced iron powder to the leachate obtained in the previous step to reduce Fe 3+ Reduced to Fe 2+ The mass ratio of reduced iron powder to reduced ore powder was 14:200, the reaction temperature was 50℃-60℃, the reaction time was 1h, and the reaction was completed to obtain a MnSO4-FeSO4 mixed slurry.

[0012] 4) Heat the MnSO4-FeSO4 mixed slurry obtained in the above step to 85℃-95℃ and react for 1 hour;

[0013] 5) Adjust the pH of the MnSO4-FeSO4 mixed slurry to 4.5 using calcium carbonate. During this process, the K, Na, and Fe content in the MnSO4-FeSO4 mixed slurry will decrease. 3+ Al 3+ SO 2- 4 and OH - The reaction produces precipitates such as potassium ferric sulfate, sodium ferric sulfate, ferric hydroxide, and aluminum hydroxide. The leaching residue and the purified MnSO4-FeSO4 mixed solution A are obtained by pressure filtration. The leaching residue is washed at a solid-liquid ratio of 1:1.5 to obtain a lower concentration MnSO4-FeSO4 mixed solution B. The lower concentration MnSO4-FeSO4 mixed solution B is used as water for pulping with 300-mesh reduced mineral powder.

[0014] 6) Water absorption and crystallization: Add concentrated sulfuric acid to the purified MnSO4-FeSO4 mixed solution A obtained in the previous step. The amount of concentrated sulfuric acid added is 40%-60% of the volume of the purified MnSO4-FeSO4 mixed solution A. After the reaction is completed, filter under pressure to obtain mixed crystals A of MnSO4-FeSO4 with high acid content and mixed solution C of MnSO4-FeSO4 with high acid content. Use the mixed solution C of MnSO4-FeSO4 with high acid content as sulfuric acid solution to leach the reduced mineral powder. Add a small amount of water to the mixed crystals A of MnSO4-FeSO4 with high acid content, and then add low calcium reduced iron powder with Ca≤1000ppm to adjust the pH to 3.0-4.0 to obtain a further purified MnSO4-FeSO4 mixed solution D.

[0015] 7) Analyze and test the further purified MnSO4-FeSO4 mixed solution D obtained in the previous step. Based on the analysis results of Mn and Fe content, add FeSO4·7H2O. The required mass of FeSO4·7H2O is:

[0016] (V is the volume of the MnSO4-FeSO4 mixed solution D after further purification, and the correction coefficient k = 1.03), so that the ratio of manganese to iron atoms in the MnSO4-FeSO4 mixed solution D after further purification is a controllable ratio, and the control range of the ratio of manganese to iron atoms is (2-9) / [(8-1)×k];

[0017] 8) High-temperature crystallization to adjust the manganese-iron atomic ratio: The material obtained in the previous step is reacted in a crystallization kettle with a stirring speed of 350 r / min, a holding temperature of 165℃ in the crystallization kettle, and a total crystallization time of 2 h. One-time crystallization yields MnSO4-FeSO4 crystals with low impurity content and a controllable manganese-iron atomic ratio.

[0018] In this invention:

[0019] The main components of the reduced mineral powder mentioned in step 1) are analyzed as follows:

[0020] project Mn Fe K Na Al Ca Mg Reduced mineral powder / % 38-45 12-18 ≤1 ≤0.5 ≤5 ≤0.5 ≤0.2 Reduced iron powder / % ≤0.05 ≥85 ≤0.05 ≤0.05 ≤0.1 ≤0.3 ≤0.1。

[0021] Step 6) describes water absorption and crystallization, which utilizes the hygroscopic properties of concentrated sulfuric acid. Concentrated sulfuric acid is added to the purified MnSO4-FeSO4 mixed solution A, with the amount added being 40%-60% of the volume of solution A. The concentrated sulfuric acid reacts with the solute water to form H2SO4·H2O, H2SO4·2H2O, and H2SO4·4H2O. Due to the reduction in solvent water, a large amount of the main solute, MnSO4-FeSO4, precipitates out, resulting in MnSO4-FeSO4 crystals A with high acid content. Under the condition of adding 40%-60% concentrated sulfuric acid, CaSO4 is converted into water-soluble Ca(HSO4)2, thus significantly reducing the content of the low-content impurity calcium in the high-acid MnSO4-FeSO4 crystals A. Other low-content impurities, Na, K, and Mg, exist in the solution as Na2SO4, K2SO4, and MgSO4, respectively, but these sulfates have high solubility (Na2SO42-Mg ... The solubility of Na2SO4 at 0℃ is 19.5 g / 100 ml water, the solubility of K2SO4 at 20℃ is 11.2 g / 100 ml water, and the solubility of MgSO4 at 20℃ is 33.7 g / 100 ml water. After water absorption and crystallization, Na2SO4, K2SO4, and MgSO4 remain unsaturated in the solution, thus significantly reducing the content of low-content impurities Na, K, and Mg in the crystals of MnSO4-FeSO4 with high acid content. Pressure filtration yields MnSO4-FeSO4 mixed crystals A with high acid content and MnSO4-FeSO4 mixed solution C with high acid content. MnSO4-FeSO4 mixed solution C with high acid content is used as a sulfuric acid solution to leach the reduced mineral powder. A small amount of water is added to MnSO4-FeSO4 mixed crystals A with high acid content, and then low-calcium reduced iron powder with Ca≤1000ppm is added to adjust the pH to 3.0-4.0, resulting in MnSO4-FeSO4 mixed solution D after further impurity removal.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced ore powder, as described in this invention, involves leaching the reduced ore powder with concentrated sulfuric acid, followed by adding reduced iron powder to remove Fe from the leaching slurry. 3+ Reduced to Fe 2+A mixed solution A of MnSO4-FeSO4 was obtained. Finally, FeSO4·7H2O was added to the further purified MnSO4-FeSO4 mixed solution D to prepare a MnSO4-FeSO4 mixed crystal with a manganese-iron atom ratio of (2-9): (8-1). No relevant reports have been found on the technical scheme for preparing MnSO4-FeSO4 mixed crystal with a controllable manganese-iron atom ratio.

[0024] 2. The method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder described in this invention uses reduced mineral powder as the main raw material to prepare MnSO4-FeSO4 mixed crystals with Mn / Fe atomic ratio of (2-9) / (8-1) that meet the standard of "J / CIAPS-20220010 Lithium Manganese Iron Phosphate Cathode Material for Lithium-ion Batteries". This method represents new process development and comprehensive utilization of resources.

[0025] 3. The method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder as described in this invention allows for the preparation of qualified MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio through a single crystallization. In contrast, existing methods for producing battery-grade MnSO4 crystal products typically require three high-temperature crystallization processes for impurity removal. The technical solution of this invention achieves energy conservation and emission reduction.

[0026] 4. Using the method described in this invention for producing MnSO4-FeSO4 mixed crystals B with controllable manganese-iron atomic ratio from reduced ore powder, the total yield of Mn element in the leaching solution and slag washing solution of the reduced ore powder is ≥94%, and the total yield of Fe element in the leaching solution and slag washing solution is ≥57%. [Attached Image Description]

[0027] Figure 1 This is a process flow diagram of the method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder according to the present invention.

Detailed Implementation Methods

[0028] The specific embodiments of the present invention will be further described below with reference to examples.

[0029] Example 1:

[0030] A method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder includes the following steps:

[0031] The main components of the reduced ore powder and reduced iron powder involved in this embodiment are shown in Table 1:

[0032] Table 1:

[0033]

[0034] (1) Pulping: 300-mesh reduced mineral powder and water are added to a mixing tank at a solid-liquid mass ratio of 1:4 to obtain slurry;

[0035] (2) While stirring the slurry, 98% concentrated sulfuric acid was added dropwise to carry out the leaching reaction at 50°C. The amount of concentrated sulfuric acid added was 1.4:1 of acid to ore ratio. The reaction temperature was 50°C and the leaching was carried out for 2 hours. After the reaction was completed, the leaching slurry was obtained.

[0036] (3) Add an appropriate amount of reduced iron powder to the leachate to reduce Fe. 3+ For Fe 2+ The reaction process parameters are: temperature 50℃, reaction time 1h, and the mass ratio of reduced iron powder to reduced ore powder is 14:200, resulting in a MnSO4-FeSO4 mixed slurry.

[0037] (4) The MnSO4-FeSO4 mixed slurry was heated to 85℃ and reacted for 1 hour;

[0038] (5) Adjust the pH of the MnSO4-FeSO4 mixed slurry to 4.5 using calcium carbonate. During this period, the K, Na, and Fe content in the MnSO4-FeSO4 mixed slurry will be reduced. 3+ Al 3+ SO 2- 4 and OH - The reaction produces precipitates such as potassium ferric sulfate, sodium ferric sulfate, ferric hydroxide, and aluminum hydroxide. The leaching residue and the purified MnSO4-FeSO4 mixed solution A are obtained by pressure filtration. The leaching residue is washed at a solid-liquid ratio of 1:1.5 to obtain a lower concentration MnSO4-FeSO4 mixed solution B. The lower concentration MnSO4-FeSO4 mixed solution B is used as water for pulping with 300-mesh reduced mineral powder.

[0039] (6) Water absorption and crystallization: Taking advantage of the water absorption property of concentrated sulfuric acid, concentrated sulfuric acid was added to the purified MnSO4-FeSO4 mixed solution A. The amount of concentrated sulfuric acid added was 40% of the volume of the purified MnSO4-FeSO4 mixed solution A. After pressure filtration, MnSO4-FeSO4 mixed crystals A and MnSO4-FeSO4 mixed solution C with high acid content were obtained. MnSO4-FeSO4 mixed solution C with high acid content was used as sulfuric acid solution to leach the reduced mineral powder. A small amount of water was added to MnSO4-FeSO4 mixed crystals A with high acid content, and then low calcium reduced iron powder with Ca≤1000ppm was added to adjust the pH to 3.5 to obtain MnSO4-FeSO4 mixed solution D with further purification.

[0040] (7) Analyze and test the MnSO4-FeSO4 mixed solution D after further impurity removal. Based on the analysis results, add FeSO4·7H2O. The required mass of FeSO4·7H2O is:

[0041] (V is the volume of the MnSO4-FeSO4 mixed solution D after further purification, and the correction factor k = 1.03), so that the ratio of manganese to iron atoms in the MnSO4-FeSO4 mixed solution D after further purification is 6:(4×k);

[0042] (8) Experiment on adjusting the manganese-iron atomic ratio by high temperature crystallization: The stirring speed of the crystallization vessel was 350 r / min, the holding temperature of the crystallization vessel was 165℃, and the total crystallization time was 2h. A mixed crystal of MnSO4-FeSO4 with low impurity content and a manganese-iron atomic ratio of 6:4 was obtained by one crystallization. The test results of the obtained MnSO4-FeSO4 mixed crystal are shown in Table 2 below. The indexes were formulated with reference to the standard "HG / T 4823-2015 Manganese Sulfate for Batteries".

[0043] Table 2:

[0044] project content index <![CDATA[Mn 2+ (%)]]> 19.74 No requirements <![CDATA[Fe 3+ (%)]]> 0.20 No requirements <![CDATA[Fe 2+ (%)]]> 12.86 No requirements Potassium (mg / kg) 78.93 ≤100ppm Sodium (mg / kg) 90.05 ≤100ppm Calcium (mg / kg) 191.96 ≤200ppm Magnesium (mg / kg) 148.40 ≤200ppm

[0045] In this embodiment, the manganese-iron atomic ratio in the MnSO4-FeSO4 mixed crystal is 6:4, the total yield of manganese in the leaching solution and rinsing solution is 94.34%, and the total yield of iron in the leaching solution and rinsing solution is 60.57%.

[0046] Example 2:

[0047] A method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder includes the following steps:

[0048] The chemical composition data of the reduced ore powder and reduced iron powder in this embodiment are the same as those in Example 1;

[0049] (1) Pulping: 300-mesh reduced mineral powder and water are added to a mixing tank at a solid-liquid mass ratio of 1:4 to obtain slurry;

[0050] (2) While stirring the slurry, 98% concentrated sulfuric acid was added dropwise. The leaching reaction was carried out at 55°C. The amount of concentrated sulfuric acid added was 1.4:1 of acid to ore ratio. The reaction temperature was 55°C and the leaching was carried out for 2 hours. After the reaction was completed, the leaching slurry was obtained.

[0051] (3) Add an appropriate amount of reduced iron powder to the leachate to reduce Fe. 3+ For Fe 2+The reaction process parameters are: temperature 50℃, reaction time 1h, and the mass ratio of reduced iron powder to reduced ore powder is 14:200, resulting in a MnSO4-FeSO4 mixed slurry.

[0052] (4) The MnSO4-FeSO4 mixed slurry was heated to 90℃ and reacted for 1 hour;

[0053] (5) Adjust the pH of the MnSO4-FeSO4 mixed slurry to 4.5 using calcium carbonate. During this period, the K, Na, and Fe content in the MnSO4-FeSO4 mixed slurry will be reduced. 3+ Al 3+ SO 2- 4 and OH - The reaction produces precipitates such as potassium ferric sulfate, sodium ferric sulfate, ferric hydroxide, and aluminum hydroxide. The leaching residue and the purified MnSO4-FeSO4 mixed solution A are obtained by pressure filtration. The leaching residue is washed at a solid-liquid ratio of 1:1.5 to obtain a lower concentration MnSO4-FeSO4 mixed solution B. The lower concentration MnSO4-FeSO4 mixed solution B is used as water for pulping with 300-mesh reduced mineral powder.

[0054] (6) Water absorption and crystallization: Taking advantage of the water absorption property of concentrated sulfuric acid, concentrated sulfuric acid was added to the purified MnSO4-FeSO4 mixed solution A. The amount of concentrated sulfuric acid added was 50% of the volume of the purified MnSO4-FeSO4 mixed solution A. After pressure filtration, MnSO4-FeSO4 mixed crystals A and MnSO4-FeSO4 mixed solution C with high acid content were obtained. MnSO4-FeSO4 mixed solution C with high acid content was used as sulfuric acid solution to leach the reduced mineral powder. A small amount of water was added to MnSO4-FeSO4 mixed crystals A with high acid content, and then low calcium reduced iron powder with Ca≤1000ppm was added to adjust the pH to 3.5 to obtain MnSO4-FeSO4 mixed solution D with further purification.

[0055] (7) Analyze and test the MnSO4-FeSO4 mixed solution D after further impurity removal. Based on the analysis results, add FeSO4·7H2O. The required mass of FeSO4·7H2O is:

[0056] (V is the volume of the MnSO4-FeSO4 mixed solution D after further purification, and the correction factor k = 1.03), so that the ratio of manganese to iron atoms in the MnSO4-FeSO4 mixed solution D after further purification is 5:(4×k);

[0057] (8) Experiment on adjusting the manganese-iron atomic ratio by high temperature crystallization: The stirring speed of the crystallization vessel was 350 r / min, the holding temperature of the crystallization vessel was 165℃, and the total crystallization time was 2h. A mixed crystal of MnSO4-FeSO4 with low impurity content and a manganese-iron atomic ratio of 5:4 was obtained by one crystallization. The test results of the obtained MnSO4-FeSO4 mixed crystal are shown in Table 3 below. The indexes were formulated with reference to the standard "HG / T 4823-2015 Manganese Sulfate for Batteries".

[0058] Table 3

[0059] project content index <![CDATA[Mn 2+ (%)]]> 18.51 No requirements <![CDATA[Fe 3+ (%)]]> 0.19 No requirements <![CDATA[Fe 2+ (%)]]> 14.39 No requirements Potassium (mg / kg) 79.76 ≤100ppm Sodium (mg / kg) 70.68 ≤100ppm Calcium (mg / kg) 172.32 ≤200ppm Magnesium (mg / kg) 126.74 ≤200ppm

[0060] In this embodiment, the manganese-iron atomic ratio in the MnSO4-FeSO4 mixed crystal is 5:4, the total yield of manganese in the leaching solution and rinsing solution is 97.12%, and the total yield of iron in the leaching solution and rinsing solution is 64.73%.

[0061] Example 3:

[0062] A method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder includes the following steps:

[0063] The chemical composition data of the reduced ore powder and reduced iron powder in this embodiment are the same as those in Example 1;

[0064] (1) Pulping: 300-mesh reduced mineral powder and water are added to a mixing tank at a solid-liquid mass ratio of 1:4 to obtain slurry;

[0065] (2) While stirring the slurry, 98% concentrated sulfuric acid was added dropwise to carry out the leaching reaction at 60°C. The amount of concentrated sulfuric acid added was 1.4:1 of acid to ore ratio. The reaction temperature was 60°C and the leaching was carried out for 2 hours. After the reaction was completed, the leaching slurry was obtained.

[0066] (3) Add an appropriate amount of reduced iron powder to the leachate to reduce Fe. 3+ For Fe 2+ The reaction process parameters are: temperature 60℃, reaction time 1h, and the mass ratio of reduced iron powder to reduced ore powder is 14:200, resulting in a MnSO4-FeSO4 mixed slurry.

[0067] (4) The MnSO4-FeSO4 mixed slurry was heated to 95℃ and reacted for 1 hour;

[0068] (5) Adjust the pH of the MnSO4-FeSO4 mixed slurry to 4.5 using calcium carbonate. During this period, the K, Na, and Fe content in the MnSO4-FeSO4 mixed slurry will be reduced. 3+ Al 3+ SO 2- 4 and OH -The reaction produces precipitates such as potassium ferric sulfate, sodium ferric sulfate, ferric hydroxide, and aluminum hydroxide; the leaching residue and the purified MnSO4-FeSO4 mixed solution A are obtained by pressure filtration. The leaching residue is washed at a solid-liquid ratio of 1:1.5 to obtain a lower concentration MnSO4-FeSO4 mixed solution B. The lower concentration MnSO4-FeSO4 mixed solution B is used as water for pulping with 300-mesh reduced mineral powder.

[0069] (6) Water absorption and crystallization: Taking advantage of the water absorption property of concentrated sulfuric acid, concentrated sulfuric acid was added to the purified MnSO4-FeSO4 mixed solution A. The amount of concentrated sulfuric acid added was 60% of the volume of the purified MnSO4-FeSO4 mixed solution A. After pressure filtration, MnSO4-FeSO4 mixed crystals A and MnSO4-FeSO4 mixed solution C with high acid content were obtained. MnSO4-FeSO4 mixed solution C with high acid content was used as sulfuric acid solution to leach the reduced mineral powder. A small amount of water was added to MnSO4-FeSO4 mixed crystals A with high acid content, and then low calcium reduced iron powder with Ca≤1000ppm was added to adjust the pH to 3.5 to obtain MnSO4-FeSO4 mixed solution D with further purification.

[0070] (7) Analyze and test the MnSO4-FeSO4 mixed solution D after further impurity removal. Based on the analysis results, add FeSO4·7H2O. The required mass of FeSO4·7H2O is:

[0071] (V is the volume of the MnSO4-FeSO4 mixed solution D after further purification, and the correction factor k = 1.03), so that the ratio of manganese to iron atoms in the MnSO4-FeSO4 mixed solution D after further purification is 7:(4×k);

[0072] (8) Experiment on adjusting the manganese-iron atomic ratio by high temperature crystallization: The stirring speed of the crystallization vessel was 350 r / min, the holding temperature of the crystallization vessel was 165℃, and the total crystallization time was 2h. A mixed crystal of MnSO4-FeSO4 with low impurity content and a manganese-iron atomic ratio of 7:4 was obtained by one crystallization. The test results of the obtained MnSO4-FeSO4 mixed crystal are shown in Table 4 below. The indexes were formulated with reference to the standard "HG / T 4823-2015 Manganese Sulfate for Batteries".

[0073] Table 4

[0074]

[0075]

[0076] In this embodiment, the manganese-iron atomic ratio in the MnSO4-FeSO4 mixed crystal is 7:4, the total yield of manganese in the leaching solution and rinsing solution is 95.67%, and the total yield of iron in the leaching solution and rinsing solution is 57.10%.

[0077] Comparative Example 1:

[0078] The chemical composition data of the reduced ore powder and reduced iron powder in this comparative example are the same as those in Example 1. The difference in the operation steps compared to Example 1 is:

[0079] In step (5), calcium carbonate is not added; instead, reduced mineral powder with low MnO2 content (ω) is used to adjust the pH. MnO2 Within the range of 0%-0.3%, its component analysis is as follows: ω Mn 47.63%, ω Fe 15.40%, ω MnO2 : 0.1%; approximately 30g of low MnO2 content reducing ore powder is needed for 200g of reducing ore powder. MnO2 Reduced mineral powder with low MnO2 content (ω) within the range of 0%-0.3% MnO2 Within the range of 0%-0.3%, water is added at a solid-liquid ratio of 1:4 to form a slurry, which is then slowly added to the MnSO4-FeSO4 mixed slurry. The pH of the slurry is adjusted to 2.5. Then, reduced iron powder is added to collect acid. The amount added is 4g of reduced iron powder for every 200g of reduced ore powder. Finally, calcium carbonate is added to adjust the pH to 3.5-4.0 to remove impurities. The solution is then filtered to obtain the purified MnSO4-FeSO4 mixed solution B.

[0080] The remaining operations are the same as in Example 1.

[0081] The test results of the obtained MnSO4-FeSO4 crystals are shown in Table 5 below. The indicators were formulated with reference to the standard "HG / T 4823-2015 Manganese Sulfate for Batteries".

[0082] Table 5:

[0083]

[0084]

[0085] The results of the comparative experiment show that:

[0086] In Comparative Example 1, the manganese-iron atomic ratio in the MnSO4-FeSO4 mixed crystal was 6:4, with a total manganese yield of 91.76% and an iron yield of 49.84% in the leaching and rinsing solutions. In Example 1, the manganese-iron atomic ratio in the MnSO4-FeSO4 crystal was 6:4, with a total manganese yield of 94.34% and an iron yield of 60.57% in the leaching and rinsing solutions.

[0087] Instructions to use reduced mineral powder with low MnO2 content (ω) MnO2 When calcium carbonate is used to adjust pH in the range of 0%-0.3%, the manganese and iron in the reduced mineral powder with low MnO2 content do not react sufficiently, resulting in a decrease in the total yield of manganese and iron in the leaching and washing solutions.

[0088] Comparative Example 2:

[0089] Replace the reduced mineral powder in step 1) of Example 1 with pyrolusite (ω Mn 41.74%, ω MnO2 36.35%, ω Fe : 6.04%) and pyrite (ω Fe 32.45%, ω S (34.42%). Pyrolusite and water were pulped at a solid-liquid ratio of 1:4 to obtain a slurry. Concentrated sulfuric acid with a mass content of 98% was added dropwise to the slurry at an acid-to-ore ratio of 0.8:1. Then, pyrite was slowly added, with the amount of pyrite added being 0.3 times that of pyrolusite. The reaction temperature was 90℃, and the reaction time was 3 hours. Finally, reduced iron powder was added to reduce Fe. 3+ For Fe 2+ The ratio of reduced iron powder to pyrolusite was 5:200, the reaction temperature was 90℃, the reaction time was 1h, and finally calcium carbonate was added to adjust the pH to 4.5 to remove impurities. The solution was then filtered to obtain a mixed solution B of MnSO4-FeSO4 after impurity removal.

[0090] The other steps are the same as in Example 1.

[0091] The test results of the obtained MnSO4-FeSO4 crystals are shown in Table 6 below. The indicators were formulated with reference to the standard "HG / T 4823-2015 Manganese Sulfate for Batteries".

[0092] Table 6:

[0093] project content index <![CDATA[Mn 2+ (%)]]> 18.70 No requirements <![CDATA[Fe 3+ (%)]]> 0.05 No requirements <![CDATA[Fe 2+ (%)]]> 12.70 No requirements Potassium (mg / kg) 42.48 ≤100ppm Sodium (mg / kg) 71.52 ≤100ppm Calcium (mg / kg) 152.84 ≤200ppm Magnesium (mg / kg) 78.54 ≤200ppm

[0094] The results of the comparative experiment show that:

[0095] In Comparative Example 2, the manganese-iron atomic ratio in the MnSO4-FeSO4 mixed crystal was 6:4, the total yield of manganese in the leaching and washing solutions was 95.26%, and the total yield of iron in the leaching and washing solutions was 38.07% (iron from pyrolusite). In Example 1, the manganese-iron atomic ratio in the MnSO4-FeSO4 crystal was 6:4, the total yield of manganese in the leaching and washing solutions was 94.34%, and the total yield of iron in the leaching and washing solutions was 60.57%.

[0096] Since pyrite and manganese ore undergo a redox reaction in sulfuric acid solution to leach manganese and iron, it indicates that using manganese ore and pyrite as raw materials results in poor iron leaching, leading to a decrease in the total iron yield in the leachate and washing solution.

[0097] Summarize:

[0098] The method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced ore powder as described in this invention has a manganese-iron atomic ratio of (5-7):4 in the MnSO4-FeSO4 mixed crystals. The total yield of Mn element in the leaching solution and slag washing solution of the reduced ore powder is 94.34-97.12%, and the total yield of Fe element in the leaching solution and slag washing solution is 57.10-64.73%.

[0099] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, any improvements and changes made without departing from the inventive concept of the present invention are within the protection scope of the present invention.

Claims

1. A method for producing MnSO4-FeSO4 mixed crystals with controllable manganese-iron atomic ratio using reduced mineral powder, characterized in that: Includes the following steps: 1) Pulping: 300-mesh reduced ore powder and water are added to a stirred tank at a solid-liquid mass ratio of 1:4 and pulverized to obtain a slurry; the main components of the reduced ore powder are shown below: 2) While stirring the slurry obtained in the previous step, add concentrated sulfuric acid with a mass content of 98% dropwise, and carry out the leaching reaction at 50℃-60℃. The amount of concentrated sulfuric acid added is 1.4:1 acid-ore ratio, and the leaching time is 2 hours. After the reaction is completed, the leaching slurry is obtained. 3) Add reduced iron powder to the leachate obtained in the previous step to reduce Fe 3+ Reduced to Fe 2+ The mass ratio of reduced iron powder to reduced ore powder was 14:200, the reaction temperature was 50℃-60℃, the reaction time was 1h, and the reaction was completed to obtain a MnSO4-FeSO4 mixed slurry. 4) Heat the MnSO4-FeSO4 mixed slurry obtained in the above step to 85℃-95℃ and react for 1 hour; 5) Adjust the pH of the MnSO4-FeSO4 mixed slurry to 4.5 using calcium carbonate. During this process, the K content in the MnSO4-FeSO4 mixed slurry... + Na + Fe 3+ Al 3+ SO4 2- and OH - The reaction produces potassium ferric sulfate, sodium ferric sulfate, ferric hydroxide and aluminum hydroxide precipitates. The leaching residue and the purified MnSO4-FeSO4 mixed solution A are obtained by pressure filtration. The leaching residue is washed at a solid-liquid ratio of 1:1.5 to obtain a lower concentration MnSO4-FeSO4 mixed solution B. The lower concentration MnSO4-FeSO4 mixed solution B is used as water for pulping with 300-mesh reduced mineral powder. 6) Water absorption and crystallization: Add concentrated sulfuric acid to the purified MnSO4-FeSO4 mixed solution A obtained in the previous step. The amount of concentrated sulfuric acid added is 40%-60% of the volume of the purified MnSO4-FeSO4 mixed solution A. After the reaction is completed, filter press to obtain MnSO4-FeSO4 crystals A with high acid content and MnSO4-FeSO4 mixed solution C with high acid content. Use the MnSO4-FeSO4 mixed solution C with high acid content as sulfuric acid solution to leach the reduced mineral powder. Add a small amount of water to the MnSO4-FeSO4 mixed crystals A with high acid content, and then add low calcium reduced iron powder with Ca≤1000ppm to adjust the pH to 3.0-4.0 to obtain MnSO4-FeSO4 mixed solution D with further purification. 7) Analyze and test the further purified MnSO4-FeSO4 mixed solution D obtained in the previous step. Based on the analysis results of Mn and Fe content, add FeSO4·7H2O. The required mass of FeSO4·7H2O is: V is the volume of the MnSO4-FeSO4 mixed solution D after further purification, and the correction coefficient k = 1.03, so that the ratio of manganese to iron atoms in the MnSO4-FeSO4 mixed solution D after further purification is a controllable ratio, and the control range of the ratio of manganese to iron atoms is (2-9) / [(1-8)×k]; 8) High-temperature crystallization to adjust the manganese-iron atomic ratio: The material obtained in the previous step is reacted in a crystallization kettle with a stirring speed of 350 r / min, a holding temperature of 165℃ in the crystallization kettle, and a total crystallization time of 2 h. One-time crystallization yields MnSO4-FeSO4 crystals with low impurity content and a controllable manganese-iron atomic ratio.

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