Method for productizing iron-manganese elements in ferromanganese alloys

Abstract

This invention relates to the field of metal production or smelting technology, and discloses a method for the commercialization of iron and manganese elements in ferromanganese alloys. The method employs a two-stage leaching process for selective leaching of ferromanganese alloys, comprising: Step S1, adding water to the ferromanganese alloy and / or neutralized leaching residue, introducing a first oxidant, adding a sulfur-containing reagent, adding sulfuric acid, performing a first-stage catalytic oxygen leaching, and separating the solid and liquid to obtain a first leaching solution and iron slag; Step S2, adding ferromanganese alloy to the first leaching solution, adding water, performing a second-stage neutralized leaching, introducing a second oxidant, separating the solid and liquid to obtain a second leaching solution and neutralized leaching residue, and returning the neutralized leaching residue to step S1. This invention achieves the separation of manganese and iron, with a short process flow, low cost, and high efficiency, facilitating industrial production; moreover, iron is directly converted into iron oxide precursor, obtaining high-quality iron products at low cost, and manganese can be made into manganese sulfate solution for the production of battery-grade manganese sulfate, providing a new approach for the preparation of lithium-ion battery cathode precursor materials.

Description

Technical Field

[0001] This invention relates to the fields of metal production or smelting and the preparation of precursors for lithium-ion battery cathode materials. Specifically, it relates to a method for the commercialization of iron and manganese elements in ferromanganese alloys. Background Technology

[0002] Manganese, an indispensable metallic material in modern industry, has a long history of production and a constantly evolving market structure, with wide applications in steel, batteries, chemicals, and many other fields. Currently, with the development of the lithium battery industry, the demand for manganese is rising sharply. Battery-grade manganese sulfate, as a high-purity (typically ≥99.7%) and low-impurity manganese source, provides the essential manganese element for lithium battery cathode materials. Lithium manganese iron phosphate (LMFP) is produced by introducing manganese into lithium iron phosphate (LFP). Through mixing an iron-manganese precursor with a lithium source, and then reacting in a solid or liquid phase, lithium atoms are embedded into the crystal structure, ultimately forming the lithium manganese iron phosphate cathode material.

[0003] Manganese production mainly includes hydrometallurgical and pyrometallurgical processes.

[0004] The pyrometallurgical process for manganese mainly employs the blast furnace method and the electric furnace method. At high temperatures, manganese oxides are reduced to metallic manganese or high-carbon ferromanganese using carbonaceous reducing agents (such as coke). This process is mature and has a large output, making it the main method for producing pyrometallurgical manganese products. However, the ferromanganese obtained through pyrometallurgy is mainly used in the steelmaking and casting industries and cannot enter the current lithium battery industry.

[0005] Hydrometallurgy of manganese is a green extraction technology that selectively leaches manganese from low-grade manganese ores using acidic or alkaline solvents. The main process includes leaching, solid-liquid separation, purification (such as iron, calcium, and magnesium removal), precipitation, or electrowinning to produce metallic manganese or high-purity manganese compounds. It boasts advantages such as low energy consumption, low pollution, and strong adaptability. However, its industrial application still faces several challenges: the leaching process uses the anolyte from the electrowinning process, i.e., waste acid (to replace the acid), leading to the continuous accumulation of magnesium ions in the ore and ammonium ions in the buffer. Excessive magnesium increases solution viscosity, power consumption, and even reduces current efficiency, while excessive ammonium results in manganese slag containing large amounts of ammonium salts (or forming ammonium sulfate-manganese composite crystals), easily causing ammonia nitrogen pollution and significantly impacting environmental protection. Furthermore, the residual valuable metals in the leaching residue are difficult to recover efficiently.

[0006] Chinese patent application CN116835555A discloses a method for preparing ferromanganese phosphate by wet leaching of high-iron manganese ore and the ferromanganese phosphate obtained therefrom. The method includes: adding high-iron manganese ore powder and an oxidant to a sulfuric acid solution with a concentration of 8-12 wt% for leaching, obtaining a first filtrate and a first filter residue; adding the first filter residue to a sulfuric acid solution with a concentration of 30-35 wt% for leaching, obtaining a second filtrate; mixing the first filtrate and the second filtrate to obtain a leachate, then adding iron powder for reduction, obtaining a reduced solution; adding sulfide salt to the reduced solution to adjust the pH to 2-4, adding fluoride salt, and separating the solid and liquid to obtain a purified solution; adding an oxidant and a phosphate solution to the purified solution for reaction, obtaining a wet ferromanganese phosphate; calcining the wet ferromanganese phosphate at 200-800℃ for 2-5 hours to obtain ferromanganese phosphate.

[0007] Chinese patent application CN114604843A discloses a method for preparing battery-grade ferromanganese phosphate by simultaneous leaching of high-iron manganese ore. The method includes: mixing high-iron manganese ore with a measured amount of coal powder according to the manganese and iron content, grinding; roasting, then cooling with nitrogen gas, and metering the mixture into a reaction vessel; adding dilute sulfuric acid according to the manganese and iron content, and heating for leaching; adding manganese sulfate or ferrous sulfate to the solution according to the manganese and iron content respectively; adding a measured amount of ammonium sulfide and a measured amount of manganese fluoride, and reacting; filtering to obtain a purified mixture of manganese sulfate and ferrous sulfate; and further processing the mixture to produce battery-grade ferromanganese phosphate.

[0008] Both of the above documents use high-iron manganese ore as raw material, that is, they use the raw ore leaching method to prepare iron and manganese products. This method cannot be industrialized due to its long process and poor economic efficiency. Summary of the Invention

[0009] According to one embodiment of the present invention, the purpose is to provide a method for the commercialization of iron and manganese elements in ferromanganese alloys, so as to solve the problems of long process flow, poor economic efficiency and inability to achieve industrial production in the existing technology.

[0010] The above objective can be achieved through the following technical solutions: According to one aspect of the present invention, a method for the commercialization of iron and manganese elements in ferromanganese alloys is provided, which employs a two-stage leaching process for selective leaching of the ferromanganese alloy, comprising: Step S1: Add water to the ferromanganese alloy and / or neutralized leaching residue, introduce the first oxidant, add a sulfur-containing reagent, add sulfuric acid, control the pH to 0.5-6.0, carry out a first stage of catalytic oxygen leaching, and separate the solid and liquid to obtain the first leaching solution and iron slag. In step S2, manganese-iron alloy is added to the first leachate, water is added, a second oxidant is introduced, the pH is controlled at 2.0-7.0, and a two-stage neutralization leaching is carried out. Solid-liquid separation is performed to obtain a second leachate and a neutralized leaching residue. The neutralized leaching residue is returned to step S1.

[0011] Preferably, in step S1, the conditions for carrying out a catalytic oxygen leaching are: a reaction temperature of 30-110℃, a reaction time of 1-24h, and a liquid-to-solid ratio of (2-20):1.

[0012] Preferably, in step S1, the molar ratio of the amount of the first oxidant to the amount theoretically required for iron oxidation is (0.9-10.0):1.

[0013] More preferably, in step S1, the amount of the sulfur-containing reagent, calculated as pure sulfur dioxide, is 0.1-30% of the amount of the first oxidant.

[0014] Preferably, in step S1, the sulfur-containing reagent is selected from one or more of persulfate, persulfate, sulfuric acid, sulfite, thiosulfate, metabisulfite, sulfur dioxide, and sulfur trioxide.

[0015] Preferably, in step S1, during the addition of the sulfur-containing reagent, the pH range of the system is maintained at 1.0-5.0; when the pH is below the lower limit of the pH, the addition is stopped, and the addition is resumed after the pH rises to the specified range, or the pH of the system is adjusted to the specified range before the addition is resumed.

[0016] Preferably, in step S2, the conditions for the two-stage neutralization leaching are: reaction temperature of 30-110℃, reaction time of 1-24h; liquid-to-solid ratio of (2-20):1.

[0017] Preferably, in step S2, the molar ratio of the amount of the second oxidant to the amount theoretically required for iron oxidation is (0.9-10.0):1.

[0018] Preferably, the method further includes: step S31, adding a third oxidant to the second leachate, adjusting the pH to 3.0-7.5, removing iron, and obtaining a purified manganese sulfate solution, wherein the manganese sulfate solution is used to produce battery-grade manganese sulfate using an evaporation crystallization process.

[0019] Preferably, during the iron removal process, the reaction temperature is 0-100℃ and the reaction time is 0.5-24 h.

[0020] Preferably, the molar ratio of the amount of the third oxidant to the amount theoretically required for iron oxidation is (0.9-5.0):1.

[0021] Preferably, in step S31, when adjusting the pH, the neutralizing agent used is one or more of the following: metal, alkali metal / alkaline earth metal carbonate, alkali metal / alkaline earth metal bicarbonate, alkali metal / alkaline earth metal hydroxide, and manganese-containing intermediate product.

[0022] Furthermore, the metals include manganese, aluminum, and magnesium. The manganese-containing intermediate products include manganese hydroxide and manganese oxide.

[0023] Preferably, the first oxidant, the second oxidant, and the third oxidant are each independently selected from one or more of oxygen, compressed air, oxygen-enriched air, hydrogen peroxide, and ozone.

[0024] Preferably, the method further includes: step S32, adding ferric sulfate or manganese sulfate to the second leachate to adjust the iron-manganese ratio in the solution, and using a chemical precipitation method to co-precipitate iron and manganese to obtain an iron-manganese precursor, wherein the iron-manganese precursor is used to produce manganese-iron lithium battery cathode materials.

[0025] Preferably, the chemical precipitation method is one of the following: ammonia-soda method, ammonia method, ammonium bicarbonate method, sodium hydroxide method, and sodium carbonate method.

[0026] Preferably, the method further includes: hot-processing the iron slag to prepare an iron product. Further, the iron product is one of the iron oxide series or hematite.

[0027] Preferably, the reaction temperature of the heat treatment is 300-1500℃, and the reaction time is 0.5-24 h.

[0028] Preferably, before the step of hot processing the iron slag, the method further includes: filtering and washing the iron slag, slurrying it with water, and adding a modifier for modification treatment.

[0029] Preferably, the reaction temperature for the modification treatment is 0-100℃, and the reaction time is 0.5-24 h.

[0030] Preferably, the modifier is a surfactant selected from one or more of organic alcohols, Tween compounds, phosphates, and sodium dodecylbenzene sulfonate.

[0031] Preferably, the amount of the modifier is 1-1000 g / t iron slag.

[0032] Preferably, the manganese content in the ferromanganese alloy is 2-99%. More preferably, the manganese content in the ferromanganese alloy is 10-99%.

[0033] Preferably, the ferromanganese alloy is in the form of blocks, granules, or powder. More preferably, the ferromanganese alloy is in powder form with an average particle size of less than 100 μm.

[0034] Preferably, the catalytic oxygen leaching stage employs countercurrent leaching.

[0035] Preferably, the two-stage neutralization leaching is performed using countercurrent leaching.

[0036] Beneficial effects: According to one embodiment of the present invention, selective leaching is performed using a two-stage leaching method. In the first stage of leaching, the acidity is controlled to selectively leach manganese (in solution). At the same time, based on catalytic oxidation, the iron in the system is oxidized and precipitated into slag (solid phase), thus achieving the initial separation of manganese and iron. Since the first stage of leaching is under high acid conditions, some iron will leach into the solution along with manganese. The second stage of leaching is then used to neutralize the iron by adding a manganese-iron alloy, causing the iron to hydrolyze into the slag.

[0037] During the second-stage leaching, a higher pH is controlled, and a ferromanganese alloy is added. The manganese in the ferromanganese alloy acts as a neutralizing agent, causing the iron to hydrolyze and precipitate while releasing acid, and the manganese to form manganese sulfate. The second-stage leaching solution has a high manganese content and a very low iron content, that is, a relatively pure manganese sulfate solution is obtained after the second-stage leaching. This relatively pure manganese sulfate solution can be used for the next process. Because the pH of the second stage is high, the manganese leaching rate is not high, and the neutralized leaching residue contains a lot of manganese. This neutralized leaching residue is returned to the first-stage leaching to recover manganese.

[0038] This invention employs a two-stage leaching process: a first-stage catalytic oxidation leaching followed by a second-stage neutralization leaching with the addition of a manganese-iron alloy. Throughout the process, the catalytic oxidation by adding oxidants and sulfur-containing reagents works synergistically with the oxidation of the manganese-iron alloy itself, resulting in high efficiency. This achieves efficient separation of manganese and iron, with a short process flow, low cost, and high efficiency, making it suitable for industrial production.

[0039] Compared with the prior art, the embodiments of the present invention have the following advantages: 1) High efficiency. A two-stage leaching method is adopted, with the first stage being catalytic oxygen leaching and the second stage being neutralization leaching with manganese-iron alloy. Throughout the process, the catalytic oxidation of the oxidant and sulfur-containing reagent and the autocatalytic oxidation of the manganese-iron alloy work synergistically, resulting in higher efficiency.

[0040] 2) Simple process flow. Iron slag and relatively pure manganese sulfate solution can be obtained through two-stage leaching. The relatively pure manganese sulfate solution can be further purified by deep iron removal to obtain a high-concentration manganese sulfate solution, which can then be evaporated and crystallized to produce battery-grade manganese sulfate. Alternatively, it can be mixed with manganese / iron co-precipitate to form an iron-manganese precursor for the production of manganese-iron lithium battery cathode materials. The iron slag (i.e., iron oxide precursor) can be modified or not, and high-quality iron oxide series, hematite, and other iron products can be produced at low cost through thermal processing. The entire process flow is simple, low-cost, easy to operate and controllable, and does not require complex post-processing steps such as extraction, crystallization, or re-leaching.

[0041] 3) Reduced neutralizing agent consumption. Conventional processes, especially those requiring extraction after leaching to obtain the corresponding product, consume a large amount of neutralizing agent after leaching to control the reaction pH and iron leaching; otherwise, the extraction efficiency of the metal solution in the extraction stage is affected. However, this invention adds a ferromanganese alloy during the second-stage leaching. The manganese in this alloy acts as a neutralizing agent, neutralizing the residual acid in the first-stage leaching solution, thereby reducing neutralizing agent consumption.

[0042] 4) Low requirements for equipment materials. Compared with existing hydrochloric acid or mixed acid leaching, this invention uses sulfuric acid and sulfur-containing reagents for oxidative leaching, overcoming the problems of high requirements for equipment materials in chlorine-containing leaching systems.

[0043] 5) The process is simple, low-cost, and environmentally friendly, which is conducive to industrialization. Attached Figure Description

[0044] Figure 1 The process flow diagram for the integrated production of iron and manganese elements in the ferromanganese alloy of the present invention is shown.

[0045] Figure 2 The process flow diagram of the comprehensive productization of iron and manganese elements in the ferromanganese alloy in Embodiment 1 of the present invention is shown.

[0046] Figure 3 The process flow diagram for the integrated productization of iron and manganese elements in the ferromanganese alloy in Embodiment 2 of the present invention is shown. Detailed Implementation

[0047] The technical solution of the present invention will be clearly and completely described below with reference to embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0048] As mentioned earlier, current methods for preparing battery-grade ferromanganese phosphate typically involve wet leaching from high-iron manganese ore. However, this process is lengthy and economically unfeasible, hindering industrialization. The inventors propose using ferromanganese alloy dissolution to prepare battery-grade ferromanganese products. Since ferromanganese alloys contain almost no light metals such as aluminum, calcium, and magnesium, the subsequent impurity removal process can be significantly shortened. Currently, no reports have been found regarding the use of ferromanganese alloys to prepare lithium-ion battery cathode precursor materials.

[0049] Based on this technical concept, the inventors conducted research and further discovered that if manganese and iron are directly dissolved and separated using ferromanganese alloy, the acid consumption is high. After all the iron is dissolved, a large amount of neutralizing agent is needed to neutralize the remaining acid, which introduces a large amount of impurities. Through further research and improvement, the inventors proposed a process for selective leaching of ferromanganese alloy using a two-stage oxidation leaching method.

[0050] Selective oxidative leaching of ferromanganese alloy and / or the neutralized leaching residue from the second stage is performed under conditions of oxidant, sulfur-containing reagent, and sulfuric acid. Most of the iron enters the solid phase, while manganese is efficiently leached into the leachate as manganese sulfate. A small portion of iron ash is simultaneously leached into the first stage leachate. Ferromanganese alloy is added to the first stage leachate for second-stage neutralization leaching. The manganese in the ferromanganese alloy causes the iron in the solution to hydrolyze and precipitate into the residue. For the ferromanganese alloy, the new manganese element neutralizes to form manganese sulfate. For the solution, the manganese metal in the added ferromanganese alloy acts as a neutralizing agent, neutralizing the residual acid from the first stage leaching and the acid released during iron hydrolysis in the second stage leaching. The manganese-containing neutralized leaching residue obtained from the second stage leaching is returned to the first stage catalytic oxygen leaching for manganese recovery.

[0051] like Figure 1 As shown, in some embodiments of the present invention, the method for productizing iron and manganese elements in ferromanganese alloys includes: Step S1: Add water to the manganese-iron alloy and / or the neutralized leaching residue obtained from the second stage leaching, introduce the first oxidant, add sulfur-containing reagent, add sulfuric acid, control the pH, carry out the first stage leaching, filter, and obtain the first leachate and iron slag.

[0052] This first leaching step involves catalytic oxygen leaching under conditions of oxidant, sulfur-containing reagent, and sulfuric acid. After the iron in the material is oxidized, it enters the solid phase in the form of precipitate (iron oxide). The pH is controlled to be relatively high acidity, which greatly improves the leaching rate of manganese. The manganese is efficiently leached into the solution in the form of manganese sulfate, and the solution contains a small amount of leached iron.

[0053] Step S2: Add ferromanganese alloy to the first leachate, add water, introduce a second oxidant, control the pH, and perform a two-stage leaching process, including neutralization leaching, followed by filtration to obtain a second leachate and a neutralized leaching residue. In this step, the addition of ferromanganese alloy and the introduction of an oxidant during the two-stage leaching process constitute neutralization leaching.

[0054] A second-stage leaching process is performed on the primary leaching solution by adding a ferromanganese alloy. Iron hydrolyzes and precipitates into the slag, releasing acid. New manganese from the ferromanganese alloy is leached into the second-stage leaching solution as manganese sulfate. The manganese in this ferromanganese alloy acts as a neutralizing agent to neutralize the residual acid in the primary leaching solution and the acid released during iron hydrolysis. Because the pH of the second-stage leaching is higher, the manganese leaching rate is not high. Therefore, the manganese-containing neutralized leaching residue obtained from the second-stage leaching is returned to the primary leaching solution to recover manganese. This process effectively utilizes the material's own oxidation / neutralization process while separating and recovering manganese and iron from the alloy.

[0055] In step S1 of this invention, the material being processed can be a single ferromanganese alloy, a neutralized leaching residue obtained from a two-stage neutralization leaching process, or a mixture of ferromanganese alloy and neutralized leaching residue. For example, the primary leaching material may be neutralized leaching residue, with ferromanganese alloy added in the secondary stage; or, the primary leaching material may be ferromanganese alloy, with ferromanganese alloy added in the secondary stage; or, the primary leaching material may be ferromanganese alloy and part of the neutralized leaching residue, with ferromanganese alloy added in the secondary stage, etc. It should be noted that when the material being processed in step S1 contains ferromanganese alloy, the alloy added in step S2 is not limited to ferromanganese alloy and can also be other manganese-containing materials. Since this invention aims to process ferromanganese alloy, it is preferable that the ferromanganese alloy added in step S2 has the same composition as the ferromanganese alloy in step S1.

[0056] Furthermore, the manganese content in ferromanganese alloys can be 2-99%, such as 2%, 10%, 20%, 30%, 40%, 50%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 95%, 99%, etc.

[0057] Preferably, the manganese content in the ferromanganese alloy is not less than 10%, especially for step S2, where the advantage is more pronounced. The higher manganese content allows the alloy to fully utilize the neutralizing effect of manganese in the second-stage leaching process, neutralizing residual acid / iron ions in the first-stage leaching solution and covering and neutralizing iron ions generated during the second-stage dissolution. The material processed in this invention is a ferromanganese alloy, which is fundamentally different from ferronickel alloy, and their processing methods are unrelated. On one hand, the ferromanganese alloy of this invention has a higher manganese content (while nickel is a minority in ferronickel alloy), so its addition during the second-stage leaching process can neutralize iron ions in the first-stage leaching solution and cover and neutralize iron ions generated during the second-stage dissolution. On the other hand, and more importantly, in the ferromanganese alloy of this invention, manganese is a variable-valence metal. During the second-stage oxidation process, manganese forms a high-valence oxide, manganese dioxide, which accelerates the oxidation and precipitation of ferromanganese itself. Simultaneously, manganese dioxide is converted to manganese sulfate. Unreacted manganese dioxide returns to the first stage to continue oxidizing the metal phase and is reduced to manganese sulfate. The entire process involves synergistic effects of sulfur dioxide + oxygen catalytic oxidation and autocatalytic oxidation, resulting in high efficiency.

[0058] Furthermore, the ferromanganese alloy can be in bulk, granular, or powder form. Preferably, the ferromanganese alloy is in powder form, which allows for more efficient leaching of manganese. More preferably, the average particle size of the ferromanganese alloy is less than 100 μm, and the powdered ferromanganese alloy can be obtained by methods such as water atomization, gas atomization, and grinding.

[0059] This invention achieves initial separation of manganese and iron through a single-stage catalytic oxygen leaching process. A second-stage neutralization leaching process allows the iron in the first-stage leaching solution to hydrolyze and precipitate into the slag, resulting in a relatively pure second-stage leaching solution. This second leaching solution can be used to produce manganese-iron lithium-ion battery cathode materials after simple treatment. As for the iron slag, high-quality iron oxide series products or hematite products can be obtained through low-cost preparation methods. Therefore, using manganese-iron alloys to prepare battery-grade iron-manganese products allows for iron separation through a two-stage leaching process. The manganese-iron alloy contains almost no light metals such as aluminum, calcium, and magnesium, significantly shortening the subsequent impurity removal process and facilitating industrialization. This provides a new approach for the preparation of lithium-ion battery cathode precursor materials.

[0060] In some preferred embodiments, in step S1, a first-stage leaching is performed, with the pH controlled at 0.5-6.0, preferably 1.5-4.0. In step S2, a second-stage leaching is performed, with the pH controlled at 2.0-7.0, preferably 4.0-6.0. By controlling the first-stage leaching to a higher acidity, the leaching rate of manganese can be significantly improved. Simultaneously, the catalytic oxidation under the conditions of the first oxidant and sulfur-containing reagent causes iron to slag. However, due to the high acidity, a significant amount of iron also enters the solution, requiring iron removal. For the first-stage leaching solution, a ferromanganese alloy is added for neutralization, with manganese as the neutralizing agent; this is the second-stage leaching. In the second-stage process, a higher pH value is controlled, causing the iron to hydrate and release acid. The manganese added to the ferromanganese alloy neutralizes the acid, forming manganese sulfate. Iron is inhibited from leaching in the slag. The second-stage solution has a high manganese content and a very low iron content, proceeding to the next step. Because the second-stage pH is high, the manganese leaching rate is not high, so the neutralized leaching residue from the second-stage leaching is returned to the first-stage leaching to recover manganese.

[0061] To further improve the selective leaching efficiency of manganese during the first-stage leaching process, other conditions for the first-stage catalytic oxygen leaching are controlled. Specifically, the liquid-to-solid ratio of the system is controlled to be (2-20):1, preferably (5-15):1. Furthermore, the reaction temperature for the first-stage catalytic oxygen leaching is controlled to be 30-110℃, preferably 50-100℃; the reaction time is controlled to be 1-24h, preferably 5-20h.

[0062] To fully utilize the catalytic oxidation effect during the leaching process and ensure iron oxidation is incorporated into the slag, the amount of the first oxidant and / or sulfur-containing reagent added is controlled. Preferably, the molar ratio of the first oxidant to the theoretically required amount of iron oxidation (stoichiometric ratio of iron oxidation) is (0.9-10.0):1, for example, 0.9:1; 2.0:1; 4.0:1; 6.0:1; 8.0:1; 10.0:1, etc. The amount of the sulfur-containing reagent, converted to pure sulfur dioxide, is preferably 0.1-30% of the amount of the first oxidant, for example, 0.1%, 1%, 5%, 10%, 15%, 20%, 25%, 30%, etc.

[0063] Furthermore, the first oxidant is one or more of oxygen, compressed air, oxygen-enriched air, hydrogen peroxide, and ozone. The sulfur-containing reagent may be selected from one or more of persulfate, persulfate, sulfuric acid, sulfite, thiosulfate, metabisulfite, sulfur dioxide, and sulfur trioxide.

[0064] Furthermore, the addition of the sulfur-containing reagent needs to be controlled in conjunction with pH. That is, the system pH must be maintained above 0.5 during the addition of the sulfur-containing reagent, and more specifically, between 0.5 and 6.0. Preferably, the system pH is maintained between 1.0 and 5.0 during the addition of the sulfur-containing reagent for more efficient selective leaching.

[0065] The specific chain control method is as follows: when the pH is below the lower limit, the addition can be stopped first, and the pH can be allowed to gradually rise. Once the pH reaches the specified range, the addition can resume. Alternatively, when the pH is below the lower limit, the addition can be stopped first, and a neutralizing agent can be added to adjust / stabilize the pH of the system to the specified range before further addition. The neutralizing agent can be one or more of the following: alkali metal / alkaline earth metal carbonates, alkali metal / alkaline earth metal hydroxides, alkali metal / alkaline earth metal bicarbonates, metals (such as manganese, aluminum, magnesium, iron, etc.), and manganese-containing intermediates (such as manganese hydroxide, manganese oxide, etc.).

[0066] To further improve the efficiency of the two-stage neutralization leaching, other conditions for the two-stage neutralization leaching are controlled. Specifically, the liquid-to-solid ratio of the system is controlled to be (2-20):1, preferably (5-15):1. Furthermore, the reaction temperature for the two-stage neutralization leaching is controlled to be 30-110℃, and the reaction time is controlled to be 1-24h.

[0067] To ensure that iron in the solution is oxidized and incorporated into the slag during the second-stage neutralization leaching process, the second-stage leachate is further purified, and the amount of the second oxidant introduced during the second-stage neutralization leaching process is controlled. Furthermore, the molar ratio of the amount of the second oxidant to the theoretically required amount for iron oxidation is (0.9-10.0):1, that is, the flow rate of the second oxidant, based on the stoichiometric ratio of Fe oxidation, is 0.9-10.0 times the molar content of divalent iron. The second oxidant is sourced from one or more of oxygen, compressed air, oxygen-enriched air, hydrogen peroxide, and ozone.

[0068] Furthermore, preferably, both leaching stages employ countercurrent leaching, which can further improve selective leaching efficiency.

[0069] This invention provides a high-concentration manganese sulfate solution obtained through a two-stage oxidative leaching process, enabling the production of manganese-containing precursors for lithium-ion battery cathode materials using a simple and low-cost method. Meanwhile, the iron precursor can be prepared at low cost to obtain high-quality iron oxide series products or hematite products, realizing the commercialization of iron and manganese elements and providing precursors for lithium-ion battery cathode materials.

[0070] In some optional embodiments, after the second-stage neutralization and leaching in step S2, the method further includes: step S31, adding a third oxidant to the second leaching solution and adjusting the pH to 3.0-7.5 to remove iron and impurities, thereby obtaining a further purified manganese sulfate solution. The impurity concentration in the manganese sulfate solution is controlled at an extremely low level, for example, the iron content is controlled at an extremely low level (≤5ppm), and battery-grade manganese sulfate can be produced using an evaporation crystallization process.

[0071] To further improve the iron removal effect, the amount of the third oxidant is controlled. Preferably, the molar ratio of the amount of the third oxidant to the amount theoretically required for the oxidation of ferrous iron is (0.9-5.0):1. Furthermore, the reaction temperature for iron removal is controlled at 0-100℃, and the reaction time is controlled at 0.5-24 h.

[0072] The third oxidant can be one or more of oxygen, compressed air, oxygen-enriched air, hydrogen peroxide, and ozone. Furthermore, the neutralizing agent used to adjust the pH in this step can be one or more of alkali metal / alkaline earth metal carbonates, alkali metal / alkaline earth metal hydroxides, alkali metal / alkaline earth metal bicarbonates, metals (such as manganese, aluminum, magnesium, etc.), and manganese-containing intermediates (such as manganese hydroxide, manganese oxide, etc.). Preferably, a manganese-containing reagent is used as the neutralizing agent.

[0073] In some optional embodiments, after the second stage of neutralization and leaching in step S2, the method further includes: step S32, adjusting the iron-manganese ratio in the second leaching solution by adding ferric sulfate or manganese sulfate, using a chemical precipitation method to co-precipitate iron and manganese to obtain an iron-manganese precursor, and using the iron-manganese precursor to produce manganese-iron lithium battery cathode materials.

[0074] In this embodiment, iron is not removed from the second-stage leachate. Instead, an iron-manganese solution with any ratio is prepared directly from the second-stage leachate. For example, the iron-manganese ratio can be (5-8):(5:2), specifically 5:5, 6:4, 7:3, 8:2, etc. A chemical precipitation method is used to co-precipitate iron and manganese to obtain an iron-manganese precursor, which is then supplied as a raw material to the battery material. Further, the chemical precipitation method is one of the following: ammonia-alkali method, ammonia method, ammonium bicarbonate method, sodium hydroxide method, sodium carbonate method, etc.

[0075] In some alternative embodiments, after obtaining iron slag (i.e. iron precursor) through a catalytic oxygen leaching process, the iron slag is subjected to thermal processing to produce higher quality iron products such as iron oxide series or hematite.

[0076] To further improve the efficiency of hot working and enhance the performance of iron products, the reaction temperature for hot working is 300-1500℃, and the reaction time is 0.5-24 h.

[0077] In some alternative embodiments, after obtaining iron slag (i.e. iron precursor) through a catalytic oxygen leaching process, the iron slag is first modified and then subjected to thermal processing.

[0078] Specifically, this includes: washing the iron precursor, slurrying it with water, adding a modifier for modification treatment; and hot processing the modified iron precursor to obtain iron oxide series or hematite iron products.

[0079] Preferably, the reaction temperature for the modification treatment is 0-100℃, and the reaction time is 0.5-24 h. The amount of the modifier is 1-1000 g / t of iron slag. The modifier is a surfactant, selected from one or more of organic alcohols, Tween compounds, phosphates, sodium dodecylbenzene sulfonate, etc. Furthermore, the washing liquid from the iron precursor can be incorporated into the first leachate.

[0080] The technical solution and effects of the present invention will be described below with reference to specific embodiments, comparative examples, and accompanying drawings: Example 1 The ferromanganese alloy used in this embodiment has the following composition: 65% Mn, 25% Fe, and an average particle size of 15 μm. Figure 2 As shown, a two-stage leaching process is employed, specifically including the following treatment steps: Countercurrent leaching: Take 90g of the neutralized leaching residue obtained from the second-stage neutralization leaching, add 800g of water, and under conditions of 80℃, introduce oxygen at a flow rate of 1000 mL / min, introduce sulfur dioxide at a flow rate of 20 mL / min, control the pH=2.0, add 10g of sulfuric acid, react for 10 h, filter, wash the solid iron slag to obtain iron precursor, and the liquid phase, i.e. the first leaching solution, contains 64.5 g / L Mn and 10 g / L Fe.

[0081] Mn leaching rate was 99.2%, and iron leaching rate was 10%.

[0082] Neutralization leaching: 100 g of manganese-iron alloy powder and 800 g of water were added to the first leaching solution. Under the condition of 80℃, the final pH was controlled at 4.5, and the flow rate of O2 was 1000 mL / min. The reaction was carried out for 10 h, filtered, and the second leaching solution was obtained. The residue phase was washed to obtain the neutralized leaching solution. The residue was discharged and returned to the first countercurrent leaching stage.

[0083] Deep iron removal: The second leaching solution after the two-stage leaching needs to be deeply removed to remove impurities such as iron. Three times the molar amount of ferrous iron in hydrogen peroxide is added, the reaction temperature is 80℃, manganese hydroxide is used as a neutralizing agent to control the final pH to 7.5, and the reaction time is 5h. This yields a relatively pure manganese sulfate solution (Fe<0.003g / L), which is used for evaporation and crystallization to produce battery-grade manganese sulfate.

[0084] Preparation of national standard grade iron oxide red product: The iron precursor is washed, slurried with water, and then 20g / t polyethylene glycol is added. The temperature is 80℃ and the treatment time is 4h. After filtration and drying, it is calcined at 900℃ for 4h to obtain national standard grade (highest grade) iron oxide red product, which can be used in the fields of coatings and magnetic materials.

[0085] Example 2

[0086] The ferromanganese alloy used in this embodiment has the following composition: 65% Mn and 25% Fe; the average particle size is 15 μm. Figure 3 As shown, a two-stage leaching process is employed, specifically including the following treatment steps: Countercurrent leaching: Take 90g of the neutralized leaching residue obtained from neutralization leaching, add 800g of water, and under conditions of 90℃, introduce oxygen at a flow rate of 1000 mL / min, introduce sulfur dioxide at a flow rate of 20 mL / min, control the pH=3.0, add 10g of sulfuric acid, react for 12h, filter, and obtain the first leaching solution and the solid phase of iron precursor.

[0087] Mn leaching rate was 99.3%, and iron leaching rate was 9%.

[0088] Neutralization leaching: 100 g of manganese-iron alloy powder and 800 g of water were added to the first leaching solution. The final pH was controlled at 4.0 at 85℃. O2 was introduced at a flow rate of 1000 mL / min and the reaction was carried out for 12 h. The solution was filtered to obtain the second leaching solution. The residue phase was washed to obtain the neutralized leaching residue and returned to the first countercurrent leaching stage.

[0089] Iron-manganese co-precipitation: Ferric sulfate is added to the second leachate after two leaching stages to adjust the molar ratio of manganese and iron in the solution to 1:1. Co-precipitation is carried out using the ammonia-sodium hydroxide precipitation method to obtain manganese-iron hydroxide precursor, which is used as a positive electrode precursor material to produce manganese-iron lithium battery positive electrode materials.

[0090] Preparation of national standard grade iron oxide red product: The iron precursor is washed, slurried with water, and then 20g / t polyethylene glycol is added. The temperature is 80℃ and the treatment time is 4h. After filtration and drying, it is calcined at 900℃ for 4h to obtain national standard grade (highest grade) iron oxide red product, which can be used in the fields of coatings and magnetic materials.

[0091] Example 3

[0092] The ferromanganese alloy used in this embodiment is the same as that in Example 1. The two leaching steps in this embodiment are as follows: Countercurrent leaching: 100 g of ferromanganese alloy powder was added to 800 g of water. Oxygen was introduced at 100℃ with a flow rate of 1000 mL / min. Sulfur trioxide (calculated as sulfur dioxide) was introduced at a flow rate of 20 mL / min, and the pH was controlled at 5.5. 10 g of sulfuric acid was added, and the reaction was allowed to proceed for 15 h. The mixture was then filtered to obtain the first leachate and a solid iron precursor. The Mn leaching rate was 99.0%, and the iron leaching rate was 9.0%.

[0093] Neutralization leaching: Add 100 g of manganese-iron alloy powder and 800 g of water to the first leaching solution. Under the condition of 100℃, control the final pH=5.5, introduce O2 at a flow rate of 1000 mL / min, react for 10 h, filter, and obtain the second leaching solution and neutralized leaching residue. Return the neutralized leaching residue to the first countercurrent leaching stage.

[0094] Example 4

[0095] The ferromanganese alloy used in this embodiment is the same as that in Example 1. The two leaching steps in this embodiment are as follows: Countercurrent leaching: 100 g of ferromanganese alloy powder was added to 800 g of water. O2 was introduced at 80℃ with a flow rate of 1000 mL / min. Sodium sulfite was introduced at a flow rate of 20 mL / min (calculated as sulfur dioxide), and the pH was controlled at 0.5. 10 g of sulfuric acid was added, and the reaction was allowed to proceed for 10 h. The mixture was then filtered to obtain the first leachate and a solid iron precursor. The Mn leaching rate was 99.4%, and the iron leaching rate was 15%.

[0096] Neutralization leaching: Add 100 g of manganese-iron alloy powder and 800 g of water to the first leaching solution. Under the condition of 80℃, control the final pH=3.5, introduce oxygen at a flow rate of 1000 mL / min, react for 10 h, filter, and obtain the second leaching solution and neutralized leaching residue. Return the neutralized leaching residue to the first countercurrent leaching stage.

[0097] Comparative Example 1

[0098] The ferromanganese alloy used in this comparative example is the same as that in Example 1, and the two-stage leaching steps are as follows: Countercurrent leaching: Take 90g of the neutralized leaching residue obtained from the second-stage neutralization leaching, add 800g of water, and under 90℃ conditions, introduce oxygen at a flow rate of 1000 mL / min, introduce sulfur dioxide at a flow rate of 20 mL / min, control the pH=6.5, add 10g of sulfuric acid, react for 10 h, separate, and obtain the first leaching solution and solid iron precursor.

[0099] Mn leaching rate was 88%, and iron leaching rate was 12%.

[0100] Neutralization leaching: 100 g of manganese-iron alloy powder and 800 g of water were added to the first leaching solution. The pH was controlled at 4.5 at the endpoint under 80℃ conditions. O2 flow rate was 1000 mL / min. The reaction was carried out for 10 h. After filtration, the second leaching solution was obtained. The residue phase was washed to obtain the neutralized leaching residue and returned to the first countercurrent leaching stage.

[0101] By using ferromanganese alloy as raw material, the subsequent impurity removal process is significantly shortened. A two-stage oxidative leaching method is employed for selective leaching, efficiently leaching manganese into the liquid phase as manganese sulfate. Solid-liquid separation yields a high-concentration manganese sulfate leachate, while most of the iron is oxidized and precipitates (iron oxide red) into the solid phase, directly transforming iron into an iron oxide red precursor. This achieves efficient separation of manganese and iron elements in the ferromanganese alloy. Through hot processing or modification followed by hot processing of this iron oxide red precursor, high-quality iron oxide red and other iron-based products can be obtained at a lower cost. The high-concentration manganese sulfate-containing leachate after the two-stage leaching can be further purified to obtain a manganese sulfate solution suitable for producing battery-grade manganese sulfate. Alternatively, the ratio of manganese to iron in the leachate can be adjusted, and chemical precipitation can be used to co-precipitate iron and manganese, forming an iron-manganese battery precursor. Therefore, iron in the ferromanganese alloy is ultimately transformed into an iron oxide red precursor, while manganese is transformed into a precursor material for preparing manganese-containing lithium batteries, realizing the commercialization of iron and manganese elements in the ferromanganese alloy.

[0102] The description of this invention is given for illustrative and descriptive purposes only and is not intended to be exhaustive or to limit the invention to the forms disclosed. Many modifications and variations will be apparent to those skilled in the art. The embodiments were chosen and described in order to better illustrate the principles and practical application of the invention and to enable those skilled in the art to understand the invention and to design various embodiments with various modifications suitable for a particular purpose.

Claims

1. A method for the commercialization of iron and manganese elements in ferromanganese alloys, characterized in that, Selective leaching of ferromanganese alloys is performed using a two-stage leaching method, including: Step S1: Add water to the ferromanganese alloy and / or neutralized leaching residue, introduce the first oxidant, add a sulfur-containing reagent, add sulfuric acid, control the pH to 0.5-6.0, carry out a first stage of catalytic oxygen leaching, and separate the solid and liquid to obtain the first leaching solution and iron slag. In step S2, manganese-iron alloy is added to the first leachate, water is added, a second oxidant is introduced, the pH is controlled to be 2.0-7.0, and a two-stage neutralization leaching is carried out. Solid-liquid separation is performed to obtain a second leachate and a neutralized leaching residue. The neutralized leaching residue is returned to step S1.

2. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, In step S1, the conditions for carrying out a catalytic oxygen leaching process are: reaction temperature of 30-110℃, reaction time of 1-24h, and liquid-to-solid ratio of (2-20):

1.

3. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, In step S1, the molar ratio of the amount of the first oxidant to the amount theoretically required for iron oxidation is (0.9-10.0):1; the amount of the sulfur-containing reagent, calculated as pure sulfur dioxide, is 0.1-30% of the amount of the first oxidant.

4. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, In step S1, the sulfur-containing reagent is selected from one or more of persulfate, persulfate, sulfuric acid, sulfite, thiosulfate, metabisulfite, sulfur dioxide, and sulfur trioxide; And / or, in step S1, during the addition of the sulfur-containing reagent, the pH range of the system is maintained at 1.0-5.0; when the pH is below the lower limit of the pH, the addition is stopped, and the addition is resumed after the pH rises to the specified range, or the pH of the system is adjusted to the specified range before the addition is resumed.

5. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, In step S2, the conditions for the two-stage neutralization leaching are: reaction temperature of 30-110℃, reaction time of 1-24h; liquid-to-solid ratio of (2-20):

1. And / or, in step S2, the molar ratio of the amount of the second oxidant to the amount theoretically required for iron oxidation is (0.9-10.0):

1.

6. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, It also includes: step S31, adding a third oxidant to the second leachate, adjusting the pH to 3.0-7.5, removing iron, and obtaining a purified manganese sulfate solution, wherein the manganese sulfate solution is produced as battery-grade manganese sulfate using an evaporation crystallization process; During the iron removal process, the reaction temperature is 0-100℃ and the reaction time is 0.5-24 h. The molar ratio of the amount of the third oxidant to the amount theoretically required for iron oxidation is (0.9-5.0):

1.

7. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 6, characterized in that, The first oxidant, the second oxidant, and the third oxidant are each independently selected from one or more of oxygen, compressed air, oxygen-enriched air, hydrogen peroxide, and ozone; And / or, in step S31, the neutralizing agent used to adjust the pH is one or more of the following: metal, alkali metal / alkaline earth metal carbonate, alkali metal / alkaline earth metal bicarbonate, alkali metal / alkaline earth metal hydroxide, and manganese-containing intermediate product; wherein the metal includes manganese, aluminum, and magnesium; and the manganese-containing intermediate product includes manganese hydroxide and manganese oxide.

8. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, It also includes: step S32, adding ferric sulfate or manganese sulfate to the second leachate to adjust the iron-manganese ratio in the solution, and using a chemical precipitation method to co-precipitate iron and manganese to obtain an iron-manganese precursor; The iron-manganese precursor is used to produce manganese-iron lithium battery cathode materials. The chemical precipitation method is one of the following: ammonia-soda method, ammonia method, ammonium bicarbonate method, sodium hydroxide method, and sodium carbonate method.

9. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, The method further includes: hot processing the iron slag to prepare iron products; The reaction temperature for the heat treatment is 300-1500℃, and the reaction time is 0.5-24 h. The iron product in question is one of the iron oxide series or hematite.

10. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 9, characterized in that, Before the hot processing step of the iron slag, the method further includes: filtering and washing the iron slag, slurrying it with water, and adding a modifier for modification treatment.

11. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 10, characterized in that, The reaction temperature for the modification treatment is 0-100℃, and the reaction time is 0.5-24 h. The modifier is a surfactant, selected from one or more of organic alcohols, Tween compounds, phosphates, and sodium dodecylbenzene sulfonate; The amount of the modifier used is 1-1000 g / t iron slag.

12. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, The manganese content in the ferromanganese alloy is 2-99%, preferably 10%-99%; And / or, the first stage of catalytic oxygen leaching employs countercurrent leaching, and the second stage of neutralization leaching employs countercurrent leaching.

13. The method for commercializing iron and manganese elements in ferromanganese alloys according to claim 1, characterized in that, The ferromanganese alloy is in the form of blocks, granules, or powder; preferably in powder form with an average particle size of less than 100 μm.

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