Method for extracting valuable metal from ore and preparing lithium manganese iron phosphate

Abstract

The invention provides a method for extracting valuable metals from ores, and relates to the technical field of preparation of lithium ion battery positive electrode materials from mineral aggregates, and the method comprises the following steps: S1, taking pyrolusite, carrying out alkaline leaching, and then carrying out primary reduction to obtain reduced pyrolusite; and S2, pyrite and the reduced pyrolusite are taken to be mixed and ground, then acid leaching is carried out, after solid-liquid separation, a liquid phase is extracted, and a mixed solution containing iron and manganese is obtained. According to the method, the two low-value minerals including the pyrite and the pyrolusite are creatively mixed, valuable metal iron and manganese are efficiently extracted, the battery material can be prepared through subsequent short-distance treatment, and the additional value is high.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing lithium-ion battery positive electrode materials from mineral materials, and in particular to a method for extracting valuable metals from ores and preparing lithium iron manganese phosphate. Background Art

[0002] As my country's new energy vehicle technology improves and matures, the sales of lithium-ion battery-powered vehicles in my country continue to rise, and the demand for cathode materials and their precursors is also increasing.

[0003] Faced with today's huge energy demand and increasingly serious environmental problems, lithium-ion batteries have played an increasingly important role since their successful development and commercialization. As a key component of lithium-ion batteries, cathode materials have become the key to improving the performance of lithium-ion batteries. Olivine-type lithium manganese iron phosphate (LiFe x Mn 1-x PO4, abbreviated as LFMP) cathode material is a good commercial cathode material because of its high theoretical specific capacity (>170 mAh / g), low raw material cost, compatibility with commercial electrolytes and good safety.

[0004] Currently, the main methods for preparing lithium iron manganese phosphate include high-temperature solid-phase method, hydrothermal method, mechanical ball milling method, and co-precipitation method. The high-temperature solid-phase method is simple and easy to industrialize, but it is difficult to control the crystal form and particle size, resulting in large fluctuations in product performance. The hydrothermal method has a low synthesis temperature and controllable morphology, but is limited by equipment and difficult to industrialize. The mechanical ball milling method causes uneven mixing of manganese and iron metals, which affects material properties. The co-precipitation method has low equipment requirements, a simple process, high output, and is easy to industrialize, making it a relatively common method for preparing lithium iron manganese phosphate. Currently, there are few reports on the direct preparation of lithium iron manganese phosphate by extracting manganese and iron from low-grade metal ores. The leaching process for low-grade metal minerals such as pyrolusite typically involves long-term leaching under high-temperature, high-acid conditions, resulting in high overall process costs, low efficiency, and the generation of large amounts of acidic wastewater. If efficient and environmentally friendly methods can be developed to treat low-grade metal minerals, the production cost of lithium battery cathode materials can be further reduced. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention provides a method for extracting valuable metals from ores and preparing lithium manganese iron phosphate, thereby efficiently utilizing metals such as Fe and Mn in the ores.

[0006] According to a first aspect of the present invention, a method for extracting valuable metals from ore is provided, comprising the following steps: S1: alkali leaching of pyrolusite, followed by a reduction step to obtain reduced pyrolusite; S2: mixing pyrite with the reduced pyrolusite, grinding the mixture, and then acid leaching the mixture. After solid-liquid separation, the liquid phase is extracted to obtain an iron-manganese mixed solution.

[0007] The present invention adopts an alkali leaching method to pretreat the pyrolusite, thereby removing aluminum in the pyrolusite and opening channels, and simultaneously promoting the roughening of the pyrolusite surface and increasing the reaction area.

[0008] In some embodiments, step S1 further includes: crushing the pyrolusite to a particle size of no more than 0.25 mm.

[0009] In some embodiments, the Fe content of the pyrite is 15-20 wt%, the S content is 25-30 wt%, and the Mn content of the pyrolusite is 30-50 wt%.

[0010] In some embodiments, in step S1, the alkali leaching includes: mixing the pyrolusite with an alkali solution at a solid-liquid ratio of 1 g: (3-5) mL, the concentration of the alkali solution is 40-50 g / L, the reaction temperature is 60-80° C., and the reaction time is 90-150 min.

[0011] In some preferred embodiments, the alkali solution is sodium hydroxide solution.

[0012] In some embodiments, in step S1, the one-stage reduction comprises: mixing the alkali-leached pyrolusite with a carbon reducing agent and then heating the mixture to react.

[0013] In some preferred embodiments, the mass ratio of the pyrolusite to the carbon reducing agent is (3-6):1; and / or the reaction temperature is 600-900° C., and the reaction time is 3-5 h.

[0014] The present invention performs a preliminary reduction on pyrolusite, converting high-valent MnO2 into low-valent manganese oxides such as Mn2O3 and Mn3O4, which is beneficial for subsequent synergistic leaching with pyrite. The reaction formula is as follows: 5MnO2+2C== Mn2O3+Mn3O4+CO+CO2 In some preferred embodiments, the carbon reducing agent is at least one of coal powder, charcoal powder, anthracite or petroleum coke.

[0015] In some embodiments, step S2 further comprises: drying, crushing, and ball milling the pyrite before mixing and grinding the pyrite with the reduced pyrolusite.

[0016] In some preferred embodiments, the drying comprises drying the pyrite at 60-80°C for 4-8 hours; and / or the crushing comprises crushing the pyrite to a particle size no greater than 20 μm; and / or the ball milling comprises a ball-to-material ratio of (3-10):1, a rotation speed of 300-500 rpm, and a time of 60-90 minutes. Mechanical ball milling of the pyrite to a certain extent can activate the surface particles of the pyrite.

[0017] In some embodiments, in step S2, the mass ratio of the pyrite to the reduced pyrolusite is 1:(2-6).

[0018] In some embodiments, the grinding method is ball milling. Because pyrite is much harder than pyrolusite, ball milling the two can further refine the pyrolusite particle size. Preferably, the conditions for ball milling the pyrite and reduced pyrolusite are: a ball-to-material ratio of (5-10):1, a rotation speed of 20-30 rpm, and a time of 5-8 hours.

[0019] In some preferred embodiments, the particle size of the ground pyrolusite is no greater than 0.15 mm.

[0020] In some embodiments, in step S2, the acid leaching includes: mixing the reduced pyrolusite with pyrite and acid solution at a solid-liquid ratio of 1 g: (3-6) mL, the concentration of the acid solution is 90-110 g / L, the reaction temperature is 70-90° C., and the reaction time is 120-240 min.

[0021] In some preferred embodiments, the acid solution is sulfuric acid.

[0022] Pyrite is reducible in acidic solution and can be leached together with the reduced pyrolusite to further reduce high-valent manganese oxides and convert them into Mn 2+ Dissolve into the solution. Part of the reaction formula is as follows: H2SO4+FeS2== FeSO4+H2S+S Mn2O3+ 2Fe 2+ + 6H + == 2Mn 2+ + 2Fe 3+ +3H2O Mn3O4+ 2Fe 2+ + 8H + == 3Mn 2+ + 2Fe 3+ +4H2O In some embodiments, in step S2, the extraction includes extracting the liquid phase with a P204 extractant and stripping the resulting organic phase with sulfuric acid. Using the P204 extractant in a one-step extraction process for the target metal element can purify a mixed solution of manganese sulfate and iron sulfate of relatively high purity.

[0023] In some preferred embodiments, the O / A ratio of the extracted organic phase to the aqueous phase is (2-3):1; and / or the concentration of the sulfuric acid is 0.3-0.6 mol / L, and the volume ratio of the organic phase to sulfuric acid in the stripping is 1:(1-1.2).

[0024] In some preferred embodiments, the saponification rate of the P204 extractant is 40% to 60%, and the number of extraction stages is 5 to 7.

[0025] In some embodiments, step S2 further includes: removing impurities from the iron-manganese-containing mixed liquid to obtain a purified iron-manganese-containing mixed liquid.

[0026] In some preferred embodiments, the impurity removal comprises: adding sulfide and fluoride to the iron-manganese mixed solution, and obtaining the product after solid-liquid separation; the amount of the sulfide added is 1.1 to 1.3 times the molar amount of Cu in the iron-manganese mixed solution, and the amount of the fluoride added is 1.1 to 1.3 times the total molar amount of Mg and Ca in the iron-manganese mixed solution.

[0027] According to a second aspect of the present invention, a method for preparing lithium manganese iron phosphate is proposed, comprising the steps of the method described in the first aspect of the present invention, and further comprising: co-precipitating the iron-manganese mixed solution with a phosphorus source, mixing the obtained precipitate with a carbon source and a lithium source and calcining it to obtain a lithium manganese iron phosphate positive electrode material.

[0028] In some embodiments, the ratio of the molar amount of the phosphorus source to the total molar amount of Fe and Mn in the iron-manganese mixed solution is (1.05-1.15):1.

[0029] In some preferred embodiments, the phosphorus source is at least one of phosphoric acid, sodium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate or ammonium phosphate.

[0030] In some preferred embodiments, the phosphorus source is at least one of ammonium dihydrogen phosphate, diammonium hydrogen phosphate or ammonium phosphate, and the precipitate is ammonium manganese ferrous phosphate.

[0031] In some embodiments, the carbon source is at least one of glucose or sucrose.

[0032] In some embodiments, the lithium source is at least one of lithium carbonate, lithium bicarbonate, or lithium hydroxide.

[0033] In some embodiments, the molar ratio of the ammonium manganese ferric phosphate to the carbon source and the lithium source is 1:1:(1.05-1.2).

[0034] In some embodiments, the calcination temperature is 700-1200° C., and the calcination time is 10-14 hours.

[0035] In some preferred embodiments, the method further comprises: before the co-precipitation reaction of the iron-manganese mixed solution and the phosphorus source, adding iron powder to the iron-manganese mixed solution to perform a reduction reaction.

[0036] In some preferred embodiments, after adding iron powder to the iron-manganese mixed solution, the temperature is raised to 60-80° C. and kept at this temperature for 60-90 minutes to carry out the reduction reaction.

[0037] In some preferred embodiments, the amount of the iron powder added is 0.1 to 0.6 times the total molar amount of Fe in the iron-manganese mixed solution.

[0038] The iron-manganese mixed liquid contains trivalent iron ions. By adding reduced iron powder, some of the trivalent iron ions can be converted into divalent iron ions, reducing the amount of carbon source used in the subsequent preparation of lithium manganese iron phosphate. At the same time, the Fe / Mn ratio in the liquid phase can be adjusted, and lithium manganese iron phosphate positive electrode materials with specific Fe and Mn ratios can be subsequently produced.

[0039] According to one embodiment of the present invention, there are at least the following beneficial effects: 1. The present invention uses a carbon reducing agent to pre-reduce pyrolusite, which can convert higher-valent MnO2 into lower-valent manganese oxides such as Mn2O3 and Mn3O4, thereby reducing the subsequent consumption of pyrite.

[0040] 2. When the pyrolusite after primary reduction is mixed with pyrite and ground, since the hardness of pyrite is much greater than that of pyrolusite, the hardness difference can be used to accelerate the crushing of pyrolusite and further refine the particle size of pyrolusite. At the same time, pyrolusite and pyrite can be physically combined to improve the efficiency of subsequent reactions.

[0041] 3. After the first stage of reduction, pyrolusite is leached in conjunction with pyrite. The divalent iron introduced by the pyrite serves as an iron source for the preparation of the precursor precipitate and also as a reducing agent for the pyrolusite, which can further reduce the pyrolusite. The two-stage reduction of pyrolusite can improve the leaching effect.

[0042] 4. Pyrite has a low grade, and pyrolusite is generally converted into products such as manganese sulfate in industry. The present invention creatively proposes to mix pyrite and pyrolusite, two low-value minerals, to efficiently extract valuable metals iron and manganese. Subsequently, battery materials can be prepared through short-range processing, which has high added value. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which: Figure 1 This is a process flow chart of Example 1 of the present invention. DETAILED DESCRIPTION

[0044] The following will clearly and completely describe the concept and technical effects of the present invention in conjunction with the embodiments so as to fully understand the purpose, characteristics and effects of the present invention.

[0045] Unless otherwise specified, the raw materials, reagents, or devices used in the following examples can be obtained from conventional commercial sources or can be obtained by existing known methods. Among them, pyrolusite, pyrite, and coal powder are all from third-party smelting enterprises or coal mines. The main chemical composition of pyrolusite is as follows: Mn 30.0wt%, Si 5.4wt%, Fe 8.27wt%, Al 2.9wt%, Ca0.4wt%, Mg 0.44wt%; the main chemical composition of pyrite is as follows: Fe 19.8wt%, S 27.4wt%, Mg 0.42wt%, Ca0.5wt%, Si 1.46wt%, Al 0.38wt%.

[0046] Example 1 This embodiment provides a method for preparing lithium manganese iron phosphate by combining pyrolusite with pyrite. Figure 1 As shown, the following steps are included: 1. Use an oven to dry the pyrite at 60°C for 4 hours, then crush it to a certain particle size, which is controlled to be no more than 10µm. Crush the pyrolusite to a particle size of no more than 0.25mm.

[0047] 2. Mechanically ball mill the pyrite with a ball-to-material ratio of 3:1, a rotation speed of 300 r / min, and a ball milling time of 60 min.

[0048] 3. Use NaOH solution to alkali leaching of pyrolusite to remove Al in pyrolusite. The concentration of NaOH solution is 40g / L, the solid-liquid ratio of alkali leaching is 1g:3mL, the reaction temperature is 60℃, and the stirring leaching is 90min.

[0049] 4. Use coal powder to preliminarily reduce the high-valent MnO2 in pyrolusite. Pyrolusite and coal powder are mixed in a mass ratio of 3:1 and reduced and roasted at 600℃ for 3h.

[0050] 5. The pyrolusite after preliminary reduction is mixed with pyrite in a mass ratio of 2:1 and ball milled with a ball-to-material ratio of 5:1, a rotation speed of 20 r / min, and a ball milling time of 5 h. The particle size of the pyrolusite is controlled to be no greater than 0.15 mm.

[0051] 6. The pyrite and the preliminarily reduced pyrolusite are subjected to the synergistic leaching by sulfuric acid, the concentration of the sulfuric acid is 90 g / L, the solid-liquid ratio of the synergistic leaching is 1 g:4 mL, the leaching temperature is 70 ℃, and the leaching time is 120 min.

[0052] 7. The target metals Fe and Mn are subjected to the one-step extraction by P204 extractant, the saponification rate of the extractant is 50%, the O / A ratio of the organic phase to the aqueous phase is 7:3, and the extraction stages are 6. The extracted organic phase is subjected to the stripping by the sulfuric acid with the concentration of 0.4 mol / L, the volume ratio of the organic phase to the sulfuric acid in the stripping is 1:1. The obtained manganese iron sulfate solution is filtered and purified after the addition of sodium sulfide and sodium fluoride, the sodium sulfide is added according to 1.1 times of the molar amount of Cu in the mixed solution, and the sodium fluoride is added according to 1.1 times of the total molar amount of Mg and Ca in the mixed solution.

[0053] 8. The mixed solution is added with the reduced iron powder, the addition amount is 0.1 times of the total molar amount of Fe in the mixed solution, and the temperature is increased to 70 ℃, and the temperature is kept for 60 min.

[0054] 9. The mixed solution is added with the ammonium dihydrogen phosphate to generate the ammonium manganese iron phosphate crystal, the molar ratio of the ammonium dihydrogen phosphate to the total molar amount of Fe and Mn in the mixed solution is 1.1:1.

[0055] 10. The ammonium manganese iron phosphate is added with the glucose and lithium hydroxide according to the molar ratio (Fe+Mn):carbon source:Li=1:1:1.05 to perform the synthesis calcination reaction, the calcination temperature is 800 ℃, and the calcination time is 12 h, and the lithium manganese iron phosphate positive electrode material LiFe 0.4 Mn 0.6 PO4 is prepared.

[0056] Example 2 The example provides a method for preparing lithium manganese iron phosphate by pyrolusite combined with pyrite, comprising the following steps: 1. The pyrite is dried by using an oven, dried at 70 ℃ for 6 h, and then crushed to a certain particle size, the particle size is controlled to be not greater than 15 µm, and the pyrolusite is crushed, and the particle size is controlled to be not greater than 0.25 mm.

[0057] 2. The pyrite is subjected to mechanical ball milling, the ball-to-material ratio is 6:1, the rotating speed is 400 r / min, and the ball milling time is 75 min.

[0058] 3. The pyrolusite is subjected to alkali leaching by using a NaOH solution to remove Al in the pyrolusite, the concentration of the NaOH solution is 45 g / L, the solid-liquid ratio of the alkali leaching is 1 g:3 mL, the reaction temperature is 70 ℃, and the stirring leaching time is 180 min.

[0059] 4. Use coal powder to preliminarily reduce the high-valent MnO2 in pyrolusite. Pyrolusite and coal powder are mixed in a mass ratio of 3:1 and reduced and roasted at 600℃ for 3h.

[0060] 5. The pyrolusite after preliminary reduction was mixed with pyrite in a mass ratio of 10:3 and ball milled with a ball-to-material ratio of 5:1, a rotation speed of 20 r / min, and a ball milling time of 5 h. The particle size of the pyrolusite was controlled to be no greater than 0.15 mm.

[0061] 6. Use sulfuric acid to synergistically leach the pyrite and the preliminarily reduced pyrolusite. The sulfuric acid concentration is 100 g / L, the solid-liquid ratio of the synergistic leaching is 1 g:4 mL, the reaction temperature is 80 ° C, and the leaching time is 180 min.

[0062] 7. The target metals Fe and Mn were extracted using a one-step extraction method using P204 extractant. The saponification rate of the extractant was 50%, the organic phase to aqueous phase ratio was 7:3, and the number of extraction stages was 6. The extracted organic phase was back-extracted with 0.4 mol / L sulfuric acid, with a volume ratio of 1:1 between the organic phase and sulfuric acid. Sodium sulfide and sodium fluoride were added to the resulting mixed solution of manganese sulfate and iron, and then filtered and purified. Sodium sulfide was added at a molar amount of 1.1 times the molar amount of Cu in the mixed solution, and sodium fluoride was added at a molar amount of 1.1 times the total molar amount of Mg and Ca in the mixed solution.

[0063] 8. Add reduced iron powder to the mixed solution in an amount equal to 0.2 times the total molar amount of Fe in the mixed solution, raise the temperature to 80°C, and keep warm for 60 minutes.

[0064] 9. Add ammonium dihydrogen phosphate to the mixed solution to form ammonium manganese iron phosphate crystals. The ratio of the molar amount of ammonium dihydrogen phosphate to the total molar amount of iron and manganese in the mixed solution is 1.1:1.

[0065] 10. Add glucose and lithium hydroxide to ammonium manganese iron phosphate in a molar ratio of (Fe+Mn): carbon source: Li=1:1:1.05 for a synthetic calcination reaction at a temperature of 800°C for 12 hours to prepare lithium manganese iron phosphate positive electrode material LiFe 0.36 Mn 0.64 PO4.

[0066] Example 3 This embodiment provides a method for preparing lithium manganese iron phosphate by combining pyrolusite with pyrite, comprising the following steps: 1. Use an oven to dry the pyrite at 80°C for 8 hours, then crush it to a certain particle size, which is controlled to be no more than 20µm. Crush the pyrolusite to a particle size of no more than 0.25mm.

[0067] 2. Mechanical ball milling of pyrite was performed with a ball-to-material ratio of 10:1, a rotation speed of 500 r / min, and a ball milling time of 90 min.

[0068] 3. Use NaOH solution to alkali leaching of pyrolusite to remove Al in pyrolusite. The concentration of NaOH solution is 50g / L, the solid-liquid ratio of alkali leaching is 1g:3mL, the reaction temperature is 80℃, and the stirring leaching is 150min.

[0069] 4. Use coal powder to preliminarily reduce the high-valent MnO2 in pyrolusite. Pyrolusite and coal powder are mixed in a mass ratio of 3:1 and reduced and roasted at 600℃ for 3h.

[0070] 5. The pyrolusite after preliminary reduction was mixed with pyrite in a mass ratio of 6:1 and ball milled with a ball-to-material ratio of 5:1, a rotation speed of 20 r / min, and a ball milling time of 5 h. The particle size of the pyrolusite was controlled to be no greater than 0.15 mm.

[0071] 6. Use sulfuric acid to synergistically leach the pyrite and the preliminarily reduced pyrolusite. The sulfuric acid concentration is 110 g / L, the solid-liquid ratio of the synergistic leaching is 1 g:4 mL, the reaction temperature is 80 ° C, and the leaching time is 240 min.

[0072] 7. The target metals Fe and Mn were extracted using a one-step extraction method using P204 extractant. The saponification rate of the extractant was 50%, the organic phase to aqueous phase ratio was 7:3, and the number of extraction stages was 6. The extracted organic phase was back-extracted with 0.4 mol / L sulfuric acid, with a volume ratio of 1:1 between the organic phase and sulfuric acid. Sodium sulfide and sodium fluoride were added to the resulting mixed solution of manganese sulfate and iron, and then filtered and purified. Sodium sulfide was added at a molar amount of 1.1 times the molar amount of Cu in the mixed solution, and sodium fluoride was added at a molar amount of 1.1 times the total molar amount of Mg and Ca in the mixed solution.

[0073] 8. Add reduced iron powder to the mixed solution in an amount equal to 0.2 times the total molar amount of Fe in the mixed solution, raise the temperature to 80°C, and keep warm for 60 minutes.

[0074] 9. Add ammonium dihydrogen phosphate to the mixed solution to form ammonium manganese iron phosphate crystals. The ratio of the molar amount of ammonium dihydrogen phosphate to the total molar amount of iron and manganese in the mixed solution is 1.1:1.

[0075] 10. Add glucose and lithium hydroxide to ammonium manganese iron phosphate in a molar ratio of (Fe+Mn): carbon source: Li=1:1:1.05 for a synthetic calcination reaction at a temperature of 800°C for 12 hours to prepare lithium manganese iron phosphate positive electrode material LiFe 0.32 Mn 0.68 PO4.

[0076] Comparative Example 1 This comparative example provides a method for preparing lithium manganese iron phosphate by combining pyrolusite with pyrite. The only difference from Example 2 is that the pyrolusite and pyrite after preliminary reduction are not ball milled.

[0077] Comparative Example 2 This comparative example provides a method for preparing lithium manganese iron phosphate by combining pyrolusite with pyrite. The only difference from Example 2 is that the pyrite is ball-milled separately, and the particle size of the pyrolusite after preliminary reduction is controlled to be no more than 0.15 mm by crushing.

[0078] Comparative Example 3 This comparative example provides a method for preparing lithium manganese iron phosphate by combining pyrolusite with pyrite, which differs from Example 3 only in that the pyrolusite is not initially reduced.

[0079] Comparative Example 4 This comparative example provides a method for preparing lithium manganese iron phosphate by combining pyrolusite with pyrite, which differs from Example 3 only in that the pyrolusite is not alkaline leached with NaOH solution.

[0080] Test example The Mn content in the ferromanganese sulfate mixed solution from step 7 of Examples 1-3 and Comparative Examples 1-4 was measured, and the Mn leaching rate was calculated as shown in the following table. The Mn leaching rate was calculated as follows: Leaching rate = (v1*c1 / m0*c0)*100%, where m0 is the mass of pyrolusite (g); c0 is the mass percentage of Mn in pyrolusite (g); v1 is the volume of the ferromanganese sulfate mixed solution (L); and c1 is the Mn concentration in the ferromanganese sulfate mixed solution (g / L).

[0081]

[0082] It can be seen that the present invention pre-treats pyrolusite and pyrite, and achieves efficient Mn leaching under relatively mild conditions by adopting a synergistic leaching method of pyrolusite combined with pyrite. As can be seen from Example 2 and Comparative Examples 1 and 2, mixed ball milling of pyrolusite and pyrite can greatly improve the leaching efficiency of Mn. Refining the particle size of pyrolusite by crushing alone still does not result in a high leaching rate. This is because mixed ball milling also has the effect of physically combining pyrolusite and pyrite, which can improve the efficiency of synergistic leaching. As can be seen from Example 3 and Comparative Example 3, preliminary reduction of pyrolusite is beneficial to improving the leaching efficiency of Mn. As can be seen from Example 3 and Comparative Example 4, pre-alkaline leaching of pyrolusite is beneficial to improving the leaching efficiency of Mn.

[0083] While the embodiments of the present invention have been described in detail above, the present invention is not limited to the embodiments described above. Various modifications may be made within the scope of knowledge possessed by a person skilled in the art without departing from the spirit of the present invention. Furthermore, the embodiments of the present invention and the features thereof may be combined with one another unless there is a conflict.

Claims

1. A method for extracting valuable metals from ores, characterized in that: The following steps are involved: S1: alkali leaching of pyrolusite, followed by a reduction step to obtain reduced pyrolusite; S2: mixing pyrite with the reduced pyrolusite, grinding the mixture, and then acid leaching the mixture. After solid-liquid separation, the liquid phase is extracted to obtain an iron-manganese mixed solution.

2. The method according to claim 1, characterized in that In step S1, the alkali leaching includes: mixing the pyrolusite with an alkali solution at a solid-liquid ratio of 1 g: (3-5) mL, the concentration of the alkali solution is 40-50 g / L, the reaction temperature is 60-80° C., and the reaction time is 90-150 min.

3. The method according to claim 1, characterized in that In step S1, the first stage reduction comprises: mixing the alkali-leached pyrolusite with a carbon reducing agent and then heating the mixture to react.

4. The method according to claim 1, wherein Step S2 further includes: drying, crushing, and ball milling the pyrite before mixing and grinding the pyrite with the reduced pyrolusite.

5. The method according to claim 4, characterized in that The drying includes: drying the pyrite at 60-80° C. for 4-8 hours; and / or, the crushing includes: crushing the pyrite to a particle size not greater than 20 μm; and / or, the ball milling conditions are: a ball-to-material ratio of (3-10):1, a rotation speed of 300-500 r / min, and a time of 60-90 min.

6. The method according to claim 1, characterized in that In step S2, the mass ratio of the pyrite to the reduced pyrolusite is 1:(2-6).

7. The method according to claim 1, characterized in that In step S2, the acid leaching includes: mixing the reduced pyrolusite with pyrite and acid solution at a solid-liquid ratio of 1 g: (3-6) mL for reaction, the concentration of the acid solution is 90-110 g / L, the reaction temperature is 70-90° C., and the reaction time is 120-240 min.

8. The method according to claim 1, characterized in that In step S2, the extraction includes: extracting the liquid phase with a P204 extractant, and back-extracting the obtained organic phase with sulfuric acid.

9. A method for preparing lithium manganese iron phosphate, comprising the steps of the method according to any one of claims 1 to 8, characterized in that: Also includes: The iron-manganese mixed solution is subjected to a co-precipitation reaction with a phosphorus source, and the obtained precipitate is mixed with a carbon source and a lithium source and calcined to obtain a lithium iron manganese phosphate positive electrode material.

10. The preparation method according to claim 9, characterized in that Also includes: Before the iron-manganese mixed solution is subjected to a co-precipitation reaction with a phosphorus source, iron powder is added to the iron-manganese mixed solution to carry out a reduction reaction.

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