Method for producing manganese sulfate aqueous solution using sulfur dioxide reduction leaching method

Abstract

One embodiment of the present invention is a method for producing an aqueous manganese sulfate solution using a sulfur dioxide reduction leaching method, comprising: a raw material preparation step of preparing a manganese-containing by-product containing manganese and impurities; a pulverization step and a washing step of pulverizing and washing the manganese-containing by-product; a reduction leaching step of leaching the manganese-containing by-product pulverized by the pulverization step and the washing step; a neutralization step of neutralizing the post-leaching solution generated by the reduction leaching step; a first purification step of purifying the post-neutralization solution generated by the neutralization step; and a second purification step of additionally purifying the solution after the first purification generated by the first purification step, wherein the reduction leaching step is carried out using an inorganic acid and sulfur dioxide gas, and discloses a method for producing an aqueous manganese sulfate solution using a sulfur dioxide reduction leaching method.

Description

Technical Field

[0001] The present invention relates to a method for producing an aqueous manganese sulfate solution from a manganese-containing by-product generated during the wet smelting process of zinc. In particular, it relates to a method for producing an aqueous manganese sulfate solution of high purity used as a raw material for a precursor among the positive electrode active materials of lithium-ion secondary batteries.

Background Art

[0002] Manganese sulfate is mainly produced through processes such as leaching, precipitation, and crystallization from low-purity manganese ore or manganese-containing substances. On the other hand, for the production of manganese sulfate used as a raw material for a precursor among the positive electrode active materials of lithium-ion secondary batteries, a wet reaction is required. Among these, leaching using an acid from solid manganese-containing substances must be carried out.

[0003] In this process, the use of a reducing agent for the composition of the reducing atmosphere is required. However, there is a problem that the process operating cost increases due to excessive use of the reducing agent for complete leaching of manganese.

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to produce manganese sulfate, particularly an aqueous manganese sulfate solution of high purity, from a by-product containing manganese. In particular, in order to replace the reducing agent used in the reduction leaching process, a reducing gas containing sulfur dioxide gas is used as a leaching aid to propose a process with high recovery rate and economic efficiency.

[0005] Furthermore, a high-purity aqueous manganese sulfate solution is produced through neutralization and purification of the post-leaching solution ensured in the reduction leaching process of manganese.

Means for Solving the Problems

[0006] One embodiment of the present invention discloses a method for producing an aqueous manganese sulfate solution using a sulfur dioxide reduction leaching method, comprising: a raw material preparation step of preparing a manganese-containing by-product containing manganese and impurities; a grinding step and a washing step of grinding and washing the manganese-containing by-product; a reduction leaching step of leaching the manganese-containing by-product ground by the grinding step and the washing step; a neutralization step of neutralizing the leached solution produced by the reduction leaching step; a first purification step of purifying the neutralized solution produced by the neutralization step; and a second purification step of further purifying the first purified solution produced by the first purification step, wherein the reduction leaching step is carried out using an inorganic acid and sulfur dioxide.

[0007] In one embodiment, the average particle size of the pulverized manganese-containing by-product may be 1 μm to 25 μm.

[0008] In one embodiment, the grinding step and the washing step may be carried out in the same reactor.

[0009] In one embodiment, during the grinding and washing steps, the manganese-containing by-product is washed with dilute acid and water, the dilute acid being at least one of sulfuric acid, hydrochloric acid, and nitric acid, and the concentration of the dilute acid may be 10 g / L to 100 g / L.

[0010] In one embodiment, the amount of water introduced for the washing step may be 1.5 to 3 times the weight of the manganese-containing by-product.

[0011] In one embodiment, the neutralization step may be carried out using a manganese-containing by-product as the neutralizing agent.

[0012] In one embodiment, sulfur dioxide gas may be additionally injected during the neutralization step.

[0013] In one embodiment, the first purification step may include a step of removing the impurities using a precipitation method, and the second purification step may include a step of removing the impurities using a solvent extraction method.

[0014] In one embodiment, the first purification step may be carried out by adding at least one of sodium sulfide, sodium hydrosulfide, ammonium hydrogen sulfide, and hydrogen sulfide as a precipitating agent and allowing the impurities to precipitate.

[0015] In one embodiment, the second purification step may include a loading step of extracting manganese contained in the liquid after the first purification into an organic phase; a scrubbing step of washing the organic phase from which manganese has been extracted with water; and a stripping step of adding sulfuric acid to the organic phase after the scrubbing step to recover manganese in the form of an aqueous manganese sulfate solution. [Effects of the Invention]

[0016] According to the present invention, manganese sulfate, in particular, a high-purity aqueous solution of manganese sulfate, can be produced from manganese-containing by-products.

[0017] In the reduction leaching process included in the present invention, unlike leaching using conventional reducing agents, the use of a reducing gas allows for a relatively high recovery rate and high cost-effectiveness.

[0018] The manganese sulfate according to the present invention can be suitably used as a precursor raw material among the positive electrode active materials of lithium secondary batteries. [Brief explanation of the drawing]

[0019] [Figure 1] Figure 1 is a flowchart showing a method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to one embodiment of the present invention.

[0020] [Figure 2] Figure 2 is a flowchart showing the second purification step according to one embodiment of the present invention. [Modes for carrying out the invention]

[0021] Examples of the present invention are illustrated for the purpose of explaining the technical idea of the present invention. The scope of rights according to the present invention is not limited to the examples presented below or the specific descriptions of these examples.

[0022] Among the cathode active materials of lithium-ion secondary batteries, a wet reaction is required for the production of manganese sulfate used as a raw material for the precursor. Among them, leaching using an acid from a solid manganese-containing material must be carried out.

[0023] In this process, different from the examples of the present invention, reducing agents such as hydrogen peroxide (H2O2) for the composition of the reducing atmosphere can be used. In this case, there is a problem that the operating cost of the process increases due to excessive use of the reducing agent for complete leaching of manganese.

[0024] The method for producing an aqueous manganese sulfate solution according to an example of the present invention can use a reducing gas containing sulfur dioxide (SO2 gas) as a leaching aid, and has a high recovery rate and economic efficiency.

[0025] Hereinafter, the present invention will be described with reference to the drawings.

[0026] FIG. 1 is a flowchart showing a method for producing an aqueous manganese sulfate solution using a sulfur dioxide gas reduction leaching method according to an example of the present invention. FIG. 2 is a flowchart showing a second purification step according to an example of the present invention.

[0027] Referring to Figures 1 and 2, a method for producing an aqueous manganese sulfate solution using a sulfur dioxide reduction leaching method according to one embodiment of the present invention may include a raw material preparation step (S100) for preparing a manganese-containing by-product containing manganese and impurities, a grinding step and a washing step (S200) for grinding and washing the manganese-containing by-product, a reduction leaching step (S300) for leaching the manganese-containing by-product ground by the grinding step and the washing step, a neutralization step (S400) for neutralizing the leached solution produced by the reduction leaching step, a first purification step (S500) for purifying the neutralized solution produced by the neutralization step, and a second purification step (S600) for further purifying the first purified solution produced by the first purification step.

[0028] Raw material preparation process (S100) In the raw material preparation step (S100), a manganese-containing by-product containing manganese and impurities may be prepared. In one embodiment, the manganese-containing by-product may be generated in the wet smelting process of zinc. In this case, the manganese-containing by-product may be prepared together with the zinc process liquid in the raw material preparation step (S100).

[0029] As a manganese-containing raw material for producing an aqueous manganese sulfate solution, the manganese-containing by-product may include at least one of oxides, hydroxides, sulfides, or sulfur oxides. The manganese in the manganese-containing by-product may be present in the form of manganese dioxide (MnO2).

[0030] In one example, the manganese-containing byproduct may contain at least one of the following impurities other than manganese (Mn): calcium (Ca), potassium (K), lead (Pb), zinc (Zn), magnesium (Mg), sodium (Na), and silicon (Si). In one example, the composition of the manganese-containing byproduct is as shown in Table 1 below. The unit is wt%.

[0031] [Table 1]

[0032] In one embodiment, the manganese-containing byproduct may contain oxygen (O). For example, the portion not shown in Table 1 may be mostly oxygen (O).

[0033] Crushing and washing process (S200) In the grinding and washing process (S200), the manganese-containing by-product may be ground and washed. The grinding and washing process (S200) is a pretreatment process for the manganese-containing by-product. In the grinding and washing process (S200), a grinding process may be performed to reduce the particle size of the manganese-containing by-product. In addition, a washing process may be performed to remove at least some of the impurities contained in the manganese-containing by-product. In the raw material preparation process (S100), the manganese-containing by-product may be prepared together with the zinc process solution. In the washing process, the zinc process solution may be washed with water.

[0034] The average particle size of the crushed manganese-containing by-product may be approximately 1 μm to 25 μm. Before the crushing process, the average particle size of the manganese-containing by-product may be approximately 500 μm to 900 μm. The average particle size of the manganese-containing by-product may be reduced to approximately 1 μm to 25 μm by the crushing process. Therefore, by reducing the average particle size of the manganese-containing by-product through the crushing process before the reductive leaching process (S300), the leaching efficiency in the reductive leaching process (S300) can be increased. If the average particle size of the manganese-containing by-product is large, the reactivity is low, which may make leaching substantially difficult in the subsequent reductive leaching process (S300). That is, if the average particle size of the manganese-containing by-product is greater than 25 μm, the leaching efficiency may decrease. For example, the crushing process can be carried out using a milling machine such as a ball mill or a rod mill.

[0035] In the grinding and washing steps (S200), at least some of the impurities in the manganese-containing by-product can be removed. In one embodiment, in the grinding and washing steps (S200), the manganese-containing by-product can be washed with dilute acid and water to remove at least some of the impurities. In one embodiment, the dilute acid may be at least one of sulfuric acid (H2SO4), hydrochloric acid (HCl), and nitric acid (HNO3). In one embodiment, the concentration of the dilute acid may be 10 g / L to 100 g / L.

[0036] The amount of water used in the washing process may be 1.5 to 3 times the weight of the manganese-containing by-product. If the amount of water used in the washing process is less than 1.5 times the weight of the manganese-containing by-product, the impurity removal rate may be less than 50%. If the amount of water used in the washing process is more than 3 times, the impurity removal rate may increase, but the amount of water used in the process will increase, which may reduce economic efficiency.

[0037] In one embodiment, the grinding step and the washing step may be performed simultaneously. The grinding step and the washing step may be performed in the same reactor. For example, the grinding step and the washing step may be performed simultaneously using a wet grinding machine. After that, some of the impurities (calcium, potassium, magnesium, sodium, etc.) contained in the manganese-containing byproduct can be removed by solid-liquid separation. When the grinding step and the washing step are performed simultaneously, the process of producing the manganese sulfate aqueous solution may be simplified. This is because, during the process of producing the manganese sulfate aqueous solution, the subsequent steps after the grinding step and the washing step involve a reaction with water. Also, when the grinding step and the washing step are performed in the same reactor, the number of reactors can be reduced. In other embodiments, the grinding step and the washing step may be performed separately.

[0038] Reduction leaching process (S300) In the reductive leaching step (S300), the manganese-containing by-product pulverized in the grinding step and washing step (S200) is leached out. The reductive leaching step (S300) may be performed after the grinding step and washing step (S200). In the reductive leaching step (S300), the manganese-containing by-product pulverized using an inorganic acid and a reducing gas may be leached out. The reducing gas may be sulfur dioxide (SO2 gas). In one embodiment, the reductive leaching step (S300) may be performed using an inorganic acid and sulfur dioxide. For example, the inorganic acid may be at least one of sulfuric acid (H2SO4), hydrochloric acid (HCl), and nitric acid (HNO3). The inorganic acid may be an inorganic acid diluted with water.

[0039] In one embodiment, the concentration of sulfur dioxide may be 10% or more, in which case the manganese solubility may be 99.6% or more. Of the supplied sulfur dioxide, the sulfur dioxide that is not involved in the reaction is reused in the reductive leaching process (S300) through recycling. If the concentration of sulfur dioxide is less than 10%, the amount of circulation of gases other than sulfur dioxide increases, which may cause a decrease in the solubility. Therefore, it is preferable that the concentration of sulfur dioxide is 10% or more. However, the present invention is not limited thereto, and in other embodiments of the present invention, sulfur dioxide with a concentration of less than 10% may be used. The gases other than sulfur dioxide may be inert gases, oxygen, or air.

[0040] Sulfur dioxide can be injected via an injection pipe. For example, the process liquid may be located inside a reaction tank, and sulfur dioxide can be injected into the reaction tank through an injection pipe located at the bottom of the tank. Thus, the sulfur dioxide can react with manganese inside the process liquid.

[0041] Sulfuric acid and sulfur dioxide can be used in the reductive leaching process. In this case, sulfur dioxide reacts with water through [Reaction Equation 1] and [Reaction Equation 2] below to produce sulfurous acid, and manganese can be leached from the manganese-containing byproduct in the form of manganese sulfate (MnSO4) in a reducing atmosphere to produce the leached solution.

[0042] [Reaction Equation 1] SO2(g) → SO2(aq)

[0043] [Reaction Equation 2] MnO2 + SO2(aq) → MnSO4

[0044] Manganese in manganese-containing by-products mainly exists in the form of manganese dioxide (MnO2), but since the manganese in manganese dioxide is tetravalent, leaching of manganese can be difficult. In contrast, leaching of divalent manganese can be easily performed. Therefore, in order to leach manganese, it is necessary to reduce the manganese in the manganese dioxide in the manganese-containing by-product to divalent manganese. In this regard, in the embodiments of the present invention, tetravalent manganese can be reduced with divalent manganese using sulfur dioxide as a reducing agent, thereby enabling the production of a leached solution in the form of manganese sulfate from the manganese-containing by-product (see [Reaction Equations 1] and [Reaction Equations 2] above).

[0045] The reductive leaching process (S300) can be carried out at approximately 20°C to 60°C. The reductive leaching process (S300) starts at room temperature, and during the leaching reaction, the internal temperature can rise to 60°C due to an exothermic reaction. This may mean that an additional heat source is not required. Therefore, the reductive leaching process (S300) may be an economical process. The sulfuric acid concentration of the leaching solution may be 25 g / L to 100 g / L. The pH of the leaching solution may be 1 or less. In one example, in the reductive leaching process (S300), not only manganese but also other impurities may be leached together. For example, impurities such as calcium (Ca), potassium (K), lead (Pb), and zinc (Zn) may be leached together with manganese and contained in the leached solution.

[0046] The manganese concentration of the leaching solution obtained in the reductive leaching process (S300) may be approximately 60 g / L to 100 g / L. For example, the manganese concentration of the leaching solution may be 61 g / L to 64 g / L. Therefore, approximately 1.5 to 3 times the amount of water compared to the weight of the crushed manganese-containing by-product may be used to dilute the inorganic acid.

[0047] The sulfur dioxide generated by sulfur dioxide gas replaces the role of the leachate, thus reducing the amount of inorganic acid used in typical acid leaching processes. More specifically, sulfur dioxide can be produced from sulfur dioxide gas by [Reaction Equation 3] below, and sulfuric acid can be produced from sulfur dioxide by [Reaction Equation 4]. Therefore, it is not necessary to maintain a one-to-one equivalence ratio between inorganic acid and manganese. In other words, the amount of inorganic acid used can be reduced.

[0048] [Reaction Equation 3] SO2 + H2O → H2SO3

[0049] [Reaction Equation 4] 2H2SO3 + O2 → 2H2SO4

[0050] Neutralization process (S400) In the neutralization step (S400), the leached solution produced by the reductive leaching step (S300) can be neutralized. The neutralization step (S400) may be performed after the reductive leaching step (S300). When securing the leached solution, if the leached solution is produced in a high pH atmosphere, a small amount of leached solution may be produced. In the embodiment of the present invention, the reductive leaching step (S300) can be performed in a low pH acidic atmosphere to secure a sufficient amount of leached solution, and then the neutralization step (S400) can be performed.

[0051] In the neutralization step (S400), a neutralizing agent is added to raise the pH of the leaching solution produced in the reductive leaching step (S300). The addition of the neutralizing agent may be for the subsequent purification steps. The neutralizing agent used may be at least one of the following: manganese-containing by-product, sodium hydroxide (NaOH), sodium carbonate (Na2CO3), calcium hydroxide (Ca(OH)2), magnesium hydroxide (Mg(OH)2), calcium oxide (CaO), and magnesium oxide (MgO). Preferably, in the neutralization step (S400), the manganese-containing by-product may be used in the form of crushed manganese-containing by-product as the neutralizing agent. It is not a problem if the amount of impurities increases due to the addition of manganese-containing by-product, because the first purification step (S500) and the second purification step (S600) are performed after the neutralization step (S400).

[0052] If the neutralization step (S400) is carried out using a manganese-containing by-product, the amount of neutralizing agent added separately can be reduced, potentially lowering costs. Furthermore, the inflow of additional impurities can be prevented, and the manganese concentration in the neutralized solution can be increased. When a manganese-containing by-product is used as the neutralizing agent, a reducing gas (e.g., sulfur dioxide) may be added to the neutralization step (S400) to dissolve any valuable metals contained in the additionally added manganese-containing by-product. In this case, the leaching reactor and the neutralization reactor can be configured in a continuous manner.

[0053] After the neutralization step (S400) is performed, the pH of the neutralized solution may be approximately 3 to 5. Preferably, the pH of the neutralized solution may be approximately 4 to 5.

[0054] 1st purification step (S500) In the first purification step (S500), the neutralized solution produced by the neutralization step (S400) can be purified. The neutralized solution may also be the neutralized leachate. The first purification step (S500) is a step to remove impurities from the neutralized solution after the neutralization step (S400).

[0055] The first purification step (S500) may be a step in which impurities are removed using a precipitation method. In the first purification step (S500), at least one of sodium sulfide (Na2S), sodium hydrosulfide (NaSH), ammonium hydrogen sulfide (NH4HS), and hydrogen sulfide (H2S) may be used as a precipitating agent to remove heavy metal impurities. In addition, in the first purification step (S500), a precipitating agent may be used to remove light metal impurities. Fluoride At least one of sodium (NaF), oxalic acid (C2H2O4), or sodium oxalate (Na2C2O4) can be used. Through this, impurities such as zinc, lead, cadmium, cobalt, nickel, calcium, and magnesium can be removed. In one example, when sodium hydrosulfide (NaSH) is used as the precipitant, the reaction equation is as shown below [Reaction Equation 5]. In one example, the precipitant is Fluoride When sodium (NaF) is used, the reaction equation is as shown below [Reaction Equation 6].

[0056] [Reaction Equation 5] 2M H SO4 + 2NaSH → Na2SO4 + H2SO4 + 2M H S↓(M H (These are heavy metals such as Zn, Pb, Cd, Co, Ni, Cu, etc.)

[0057] [Reaction Equation 6] M L SO4 + 2NaF → Na2SO4 + M L F2↓(M L (These are light metals such as Ca and Mg.)

[0058] The first purification step (S500) can be carried out at approximately 20°C to 60°C.

[0059] Precipitating agents for removing heavy metal impurities can be added in an equivalent ratio of approximately 0.8 to 1.4 relative to the heavy metals present in the neutralized solution. If the precipitating agent for removing heavy metal impurities is added in an equivalent ratio of less than 0.8 relative to the heavy metals, the heavy metal removal rate will be 85% or less, and a complete reaction may not occur. If the precipitating agent for removing heavy metal impurities is added in an equivalent ratio greater than 1.4 relative to the heavy metals, an excess of impurities due to the precipitating agent will flow in, negatively impacting the process and potentially reducing economic efficiency.

[0060] Precipitating agents for removing light metal impurities can be added in an equivalent ratio of approximately 1.0 to 2.5 relative to the light metals present in the neutralized solution. If the precipitating agent for removing light metal impurities is added in an equivalent ratio of less than 1.0 relative to the light metals, the light metal removal rate may be less than 90%, indicating that a complete reaction may not occur. If the precipitating agent for removing light metal impurities is added in an equivalent ratio greater than 2.5 relative to the light metals, excess impurities originating from the precipitating agent may flow in, negatively impacting the process and potentially reducing economic efficiency.

[0061] After the first purification step (S500), the content of zinc, lead cadmium, nickel, and copper cobalt in the liquid after the first purification may decrease to 5 mg / L or less. After the first purification step (S500), the content of calcium and magnesium in the liquid after the first purification may decrease to 50 mg / L or less.

[0062] 2nd purification process (S600) In the second purification step (S600), the liquid produced in the first purification step (S500) may be further purified. The second purification step (S600) may be performed after the first purification step (S500). The second purification step (S600) may be a step to remove impurities using solvent extraction. Organic extractants may be used in the second purification step (S600) to remove impurities such as sodium (Na) and potassium (K). In one embodiment, the second purification step (S600) may include a loading step (S610), a scrubbing step (S620), and a stripping step (S630). The organic extractant can be at least one of the following: di-2-ethylhexyl phosphonic acid, mono-2-ethylhexyl(2-ethylhexyl)phosphonate, and bis(2,4,4-trimethylpentyl)phosphinic acid.

[0063] The loading step (S610) may be a step in which manganese contained in the liquid after the first purification is extracted into the organic phase. The loading step (S610) may also be a step in which manganese contained in the liquid after the first purification is extracted into the organic phase after the first purification step (S500) using an organic extractant. The reaction temperature of the loading step (S610) may be about 30°C to 50°C. When the reaction temperature of the loading step (S610) is about 30°C to 50°C, the reaction of the organic extractant may be most active. If the reaction temperature of the loading step (S610) is below 30°C, the viscosity of the organic extractant may increase and its reactivity may decrease. If the reaction temperature of the loading step (S610) is above 50°C, the efficiency of the process may decrease due to the large amount of volatile components. The amount of organic phase added to the aqueous phase in the loading step (S610) may be about 3 to 6 by volume ratio. If the volume ratio of the organic phase to the aqueous phase in the loading process (S610) is less than 3, the binding between the target metal and the organic extractant may not be complete, resulting in an extraction rate of 90% or less. If the volume ratio of the organic phase to the aqueous phase in the loading process (S610) is greater than 6, the process cost may increase due to excessive use of the organic extractant. The pH range of the loading process (S610) may be approximately 4 to 5. To adjust the pH range of the loading process (S610) to 4 to 5, at least one of sodium hydroxide (NaOH), sodium carbonate (Na2CO3), or sodium sulfate (Na2SO4) may be used.

[0064] Once the extraction of manganese into the organic phase is complete through mixing of the aqueous and organic phases, phase separation is possible due to the difference in specific gravity between the organic and aqueous phases. The organic phase containing manganese can then be subjected to a scrubbing process (S620).

[0065] The scrubbing step (S620) may be a step of washing the organic phase from which manganese has been extracted with water. The scrubbing step (S620) may also be a step of removing impurities from the loaded organic phase using water. S The reaction temperature for step 620 may be approximately 30°C to 50°C. Scrubbing process ( S620) When the reaction temperature is approximately 30°C to 50°C, the reaction of the organic extractant may be most active. Scrubbing process ( S If the reaction temperature in step 620) is below 30°C, the viscosity of the organic extractant may increase and its reactivity may decrease. Scrubbing step ( S If the reaction temperature in step 620) exceeds 50°C, the amount of volatile components will be large, which may reduce process efficiency. Scrubbing process ( S The amount of organic phase added to the aqueous phase (620) may be approximately 5 to 10 by volume. Scrubbing process ( S 620) is a process that cleans not only the target metal but also other impurities, and is a scrubbing process ( S 620) If the amount of organic phase added to the aqueous phase is less than 5 by volume, the impurity removal rate may be 85% or less. Scrubbing process ( S If the amount of organic phase added to the aqueous phase (620) is greater than 10 by volume, impurities can be completely removed, but process costs may increase as the amount of unnecessary water used increases. The organic phase containing manganese can be washed with water to remove impurities such as sodium and potassium contained in the organic phase. The organic phase containing manganese, which has been purified by removing impurities, can then be subjected to a stripping process (S630).

[0066] In the stripping step (S630), sulfuric acid may be added to the organic phase after the scrubbing step (S620) to produce a second purified liquid. The second purified liquid may be an aqueous manganese sulfate solution. That is, in the stripping step (S630), after the scrubbing step (S620), sulfuric acid may be added to the organic phase to recover manganese in the form of an aqueous manganese sulfate solution. The stripping step (S630) may be a step of back-extracting the manganese contained in the organic phase into the aqueous phase. The reaction temperature of the stripping step (S630) may be about 30°C to 50°C. When the reaction temperature of the stripping step (S630) is about 30°C to 50°C, the reaction of the organic extractant may be most active. When the reaction temperature of the stripping step (S630) is below 30°C, the viscosity of the organic extractant may increase and its reactivity may decrease. If the reaction temperature in the stripping step (S630) exceeds 50°C, the amount of volatile components may increase, potentially reducing process efficiency. The amount of organic phase added to the aqueous phase in the stripping step (S630) may be approximately 5 to 10 by volume. If the amount of organic phase added to the aqueous phase in the stripping step (S630) is less than 5 by volume, complete manganese extraction is possible, but the amount of water used may increase. Consequently, the manganese content of the manganese sulfate aqueous solution may decrease. If the amount of organic phase added to the aqueous phase in the stripping step (S630) is greater than 10 by volume, the efficiency of manganese back-extraction may decrease. The pH range of the stripping step (S630) may be approximately 0.5 to 1.5. Sulfuric acid (H2SO4) is used to adjust the pH range of the stripping step (S630) to approximately 0.5 to 1.5.

[0067] Through this process, manganese sulfate (MnSO4), from which impurities have been removed, can be recovered in the form of an aqueous solution. The manganese sulfate aqueous solution according to one embodiment of the present invention may have a manganese content of approximately 115 g / L to 135 g / L. The composition of the manganese sulfate aqueous solution is shown in Table 2 below.

[0068] [Table 2]

[0069] As a result, according to the embodiments of the present invention, manganese sulfate, particularly a high-purity aqueous solution of manganese sulfate, can be produced from manganese-containing by-products.

[0070] In the reductive leaching process included in the embodiments of the present invention, unlike leaching using a conventional reducing agent, the use of a reducing gas allows for a relatively high recovery rate and high economic efficiency.

[0071] The manganese sulfate according to the embodiments of the present invention can be appropriately used as a precursor raw material among the positive electrode active materials of lithium secondary batteries.

[0072] Example 1 (Raw material preparation process) Manganese-containing by-products containing the elements listed in Table 3 below were prepared.

[0073] [Table 3]

[0074] (Crushing process and washing process) To improve leaching efficiency, the manganese-containing by-product was crushed and washed simultaneously. This partially removed water-soluble impurities such as magnesium, sodium, and potassium. The removal rates were 55% for magnesium, 55% for sodium, and 62% for potassium. The average particle size of the manganese-containing by-product before crushing was approximately 800 μm. After crushing for 30 minutes, the average particle size of the crushed manganese-containing by-product was approximately 5 μm.

[0075] (Reduction leaching process) Next, 0.4 kg of pulverized manganese-containing byproduct was dissolved at room temperature for 1 hour in sulfuric acid with a concentration of 30 g / L, a solid-liquid ratio of 215 g / L, and 10% sulfur dioxide at a rate of 10 NL / hr to obtain a leachate with a manganese concentration of 61 g / L to 64 g / L. The solid-liquid ratio is the ratio of the byproduct to the sulfuric acid.

[0076] (neutralization process) Next, 0.1 kg of pulverized manganese-containing by-product and 10% sulfur dioxide at a rate of 2 NL / hr were added to the leached solution and neutralized at 50°C for 1 hour to obtain a neutralized solution with a manganese concentration of 80 g / L. In the case of manganese and zinc, a dissolution rate of 99.6% or higher was observed.

[0077] (1st purification step) Next, a precipitation step was performed to remove impurities present in the neutralized solution. First, 1.2 equivalents of sodium hydrosulfide (NaSH) were added to the neutralized solution to remove heavy metal impurities, and the mixture was reacted at 60°C for 2 hours. This allowed for the removal of over 99% of lead and zinc through sulfide precipitation.

[0078] Next, to remove light metal impurities, 2.0 equivalents Fluoride By adding sodium (NaF) and reacting at 70°C for 2 hours, calcium and magnesium were successfully removed to a concentration of 30 mg / L via a fluorine-based precipitate.

[0079] (2nd purification step) Next, a solvent extraction step was performed to recover manganese from the liquid obtained after the first purification step by precipitation. A 30% di-2-ethylhexyl phosphonic acid extractant was used. The pH was 4.5, the volume ratio of the organic phase to the aqueous phase was 5, and the reaction was carried out at 35°C. The volume ratio of the organic phase to the aqueous phase can be expressed as O / A (Organic / Aqueous). This loaded manganese from the aqueous phase into the organic phase, and the manganese content remaining in the aqueous phase was recovered to less than 0.1 g / L.

[0080] Next, the reaction was carried out at 35°C using an organic phase containing manganese and water to achieve an O / A ratio of 10. This scrubbed away potassium, magnesium, sodium, and other impurities. The main impurities removed at this time were potassium at 30 mg / L, magnesium at 1 mg / L, and sodium at 350 mg / L.

[0081] Next, to recover the manganese contained in the washed organic phase in the aqueous phase, sulfuric acid and the organic phase were reacted at 35°C with an 0 / A ratio of 10. This resulted in the recovery of manganese in the form of an aqueous manganese sulfate solution. The solubility of manganese was at a level of 99.6%.

[0082] Example 2 The average particle size of the manganese-containing by-product, after grinding and washing for 10 minutes, was 130 μm. Other conditions, such as the reaction conditions for the leaching process, were the same as in Example 1. The reaction conditions for the leaching process included, for example, the solid-liquid ratio, sulfuric acid concentration, sulfur dioxide concentration, reaction time, and reaction temperature. In this case, the dissolution rate of manganese in the reductive leaching process was 82%.

[0083] Example 3 In the reduction leaching process of Example 1, the concentration of sulfur dioxide was changed to 99.9%. All other conditions were the same as in Example 1. The leaching results were the same as before, with a manganese dissolution rate of 99.6% or higher, and it was possible to obtain a manganese leached solution with a manganese concentration of 61 g / L to 64 g / L. In other words, a leached solution can be obtained regardless of the sulfur dioxide concentration. In both cases, the manganese dissolution rate was at the 99% level, whether the sulfur dioxide concentration was 10% (low concentration) or 99.9% (high concentration), indicating that a high dissolution effect can be obtained regardless of the sulfur dioxide concentration.

[0084] Comparative Example The following describes comparative examples for comparison with the examples. In Comparative Examples 1 to 4, all conditions other than the process conditions described below are the same as in Example 1.

[0085] Comparative Example 1 In the leaching process, 300 g / L of sulfuric acid was added without adding a reducing agent, and then the mixture was roasted at 600°C for 5 hours to produce manganese sulfate. This manganese sulfate was dissolved in water to obtain a leachate. The solubility of manganese was 75%.

[0086] Comparative Example 2 In the leaching process, sodium oxalate was added as a reducing agent at a ratio of 1 to 3 times the molar mass of manganese. While the manganese dissolution rate was over 95%, impurities such as sodium were generated. These impurities can increase the cost of auxiliary materials in subsequent processes.

[0087] Comparative Example 3 In the first purification process, 0.75 equivalents of sodium hydrosulfide were added to remove heavy metal impurities. The removal rates for the main impurities were 98.7% for lead and 65.2% for zinc.

[0088] Comparative Example 4 In the first purification process, Fluoride Sodium was added in an equivalent ratio of 0.5 to remove light metal impurities. 52% of calcium, the main impurity, was removed.

[0089] While the technical concept of the present invention has been explained above by some embodiments and examples shown in the attached drawings, it will be understood that various substitutions, modifications, and alterations can be made without departing from the technical concept and scope of the present invention as understandable to a person with ordinary skill in the art to which the present invention pertains. Furthermore, such substitutions, modifications, and alterations should be considered to fall within the scope of the attached claims.

Claims

1. This is a method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method. A raw material preparation process for preparing manganese-containing by-products, including manganese and impurities, which are generated in the wet smelting process of zinc; A grinding step and a washing step for grinding and washing the manganese-containing by-product; A reduction leaching step for leaching the manganese-containing by-product pulverized by the aforementioned grinding and washing steps; A neutralization step to neutralize the leachate produced by the reduction leaching step; A first purification step for purifying the neutralized solution produced by the neutralization step; and The process includes a second purification step of further purifying the liquid produced by the first purification step; A method for producing an aqueous manganese sulfate solution using a sulfur dioxide reduction leaching method, wherein the reduction leaching step is carried out using an inorganic acid and sulfur dioxide.

2. A method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 1, wherein the average particle size of the pulverized manganese-containing by-product is 1 μm to 25 μm.

3. A method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 1 or 2, wherein the grinding step and the washing step are carried out in the same reactor.

4. In the aforementioned grinding and washing steps, the manganese-containing by-product is washed with dilute acid and water. The dilute acid is at least one of sulfuric acid, hydrochloric acid, and nitric acid. A method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 1 or 2, wherein the concentration of the dilute acid is 10 g / L to 100 g / L.

5. The method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 4, wherein the amount of water introduced for the washing step is 1.5 to 3 times the weight of the manganese-containing by-product.

6. A method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 1 or 2, wherein the neutralization step is carried out using a manganese-containing by-product as a neutralizing agent.

7. A method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 6, wherein sulfur dioxide gas is additionally injected in the neutralization step.

8. The first purification step includes a step of removing the impurities using a precipitation method, A method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 1 or 2, wherein the second purification step includes a step of removing the impurities using a solvent extraction method.

9. The method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 8, wherein the first purification step is carried out by adding at least one of sodium sulfide, sodium hydrosulfide, ammonium hydrogen sulfide, and hydrogen sulfide as a precipitating agent and allowing the impurities to precipitate.

10. The second purification step described above is: A loading step in which manganese contained in the liquid after the first purification is extracted into the organic phase; A scrubbing step of washing the organic phase from which manganese has been extracted with water; and A method for producing an aqueous manganese sulfate solution using the sulfur dioxide reduction leaching method according to claim 8, comprising a stripping step of adding sulfuric acid to the organic phase after the scrubbing step to recover manganese in the form of an aqueous manganese sulfate solution.

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