Method for preparing manganese sulfate aqueous solution by using sulfur dioxide gas reduction leaching method

Abstract

One embodiment of the present invention discloses a method for producing an aqueous manganese sulfate solution by means of a sulfur dioxide gas reduction leaching method, comprising: a raw material preparation step for preparing a manganese-containing by-product containing manganese and impurities; a crushing step and a washing step for crushing and washing the manganese-containing by-product; a reduction leaching step for leaching the crushed manganese-containing by-product obtained by the crushing step and the washing step; a neutralization step for neutralizing a post-leaching solution generated in the reduction leaching step; a first purification step for purifying a post-neutralization solution generated in the neutralization step; and a second purification step for further purifying the first post-purification liquid generated in the first purification step, in which the reduction leaching step is performed using an inorganic acid and a sulfur dioxide gas.

Description

Technical Field

[0001] The present invention relates to a method for producing an aqueous solution of manganese sulfate from a manganese-containing byproduct generated during a zinc hydrometallurgical process. In particular, the present invention relates to a method for producing a high-purity aqueous solution of manganese sulfate that can be used as a raw material for a precursor of a positive electrode active material for a lithium-ion secondary battery. Background Art

[0002] Manganese sulfate is mainly produced from low-purity manganese ore or manganese-containing materials through processes such as leaching, precipitation, and crystallization. On the other hand, a wet reaction is required to produce manganese sulfate, which is a raw material used as a precursor in the positive electrode active material of lithium-ion secondary batteries. Among them, acid leaching needs to be carried out from a manganese-containing material in a solid state.

[0003] In this process, a reducing agent is required to generate a reducing atmosphere. However, there is a problem that the process operation cost increases due to excessive use of the reducing agent to completely leach manganese. Summary of the invention

[0004] Technical issues

[0005] The object of the present invention is to provide a method for producing manganese sulfate, especially a high-purity manganese sulfate aqueous solution, from a manganese-containing by-product. In particular, a process with high recovery rate and economic feasibility is proposed, wherein a reducing gas containing sulfur dioxide gas is used as a leaching aid instead of a reducing agent used in a reduction leaching process.

[0006] Another object of the present invention is to provide a method for producing a high-purity manganese sulfate aqueous solution by neutralizing and purifying a leached liquid obtained in a manganese reduction leaching step.

[0007] Technical Solution

[0008] One embodiment of the present invention discloses a method for producing an aqueous solution of manganese sulfate by using a sulfur dioxide gas reduction leaching method, comprising: a raw material preparation step of preparing a manganese-containing by-product containing manganese and impurities; a crushing step and a washing step of crushing and washing the manganese-containing by-product; a reduction leaching step of leaching the crushed manganese-containing by-product obtained by the crushing step and the washing step; a neutralization step of neutralizing a leached liquid generated in the reduction leaching step; a first purification step of purifying the neutralized liquid generated in the neutralization step; and a second purification step of further purifying the first purified liquid generated in the first purification step, wherein the reduction leaching step is performed using an inorganic acid and sulfur dioxide gas.

[0009] In one embodiment, the average particle size of the crushed manganese-containing by-product may be 1 μm to 25 μm.

[0010] In one embodiment, the pulverizing step and the washing step may be performed in the same reactor.

[0011] In one embodiment, in the crushing process and the washing process, the manganese-containing by-product can be washed by diluted acid and water, the diluted acid can be at least one of sulfuric acid, hydrochloric acid and nitric acid, and the concentration of the diluted acid can be 10g / L to 100g / L.

[0012] In one embodiment, the amount of the water added in the washing process may be 1.5 to 3 times the amount of the manganese-containing by-products by weight.

[0013] In one embodiment, the neutralization process may be performed using a manganese-containing by-product as a neutralizing agent.

[0014] In one embodiment, sulfur dioxide gas may be additionally injected during the neutralization process.

[0015] In one embodiment, the first purification process may include a process of removing the impurities by a precipitation method, and the second purification process may include a process of removing the impurities by a solvent extraction method.

[0016] In one embodiment, the first purification process may be performed by adding at least one of sodium sulfide, sodium hydrogen sulfide, ammonium hydrogen sulfide, and hydrogen sulfide as a precipitant to precipitate the impurities.

[0017] In one embodiment, the second purification process may include: a loading process of extracting manganese contained in the first purified liquid into an organic phase; a washing process of washing the organic phase from which manganese has been extracted with water; and a removal process of adding sulfuric acid to the organic phase after the washing process to recover manganese in the form of a manganese sulfate aqueous solution.

[0018] Effects of the Invention

[0019] According to the present invention, in some embodiments, manganese sulfate, especially a high-purity manganese sulfate aqueous solution, can be produced from manganese-containing byproducts.

[0020] In the case of the reduction leaching process included in the present invention, unlike leaching using a conventional reducing agent, the use of a reducing gas can achieve a relatively high recovery rate and high economic benefits.

[0021] The manganese sulfate of the present invention can be suitably used as a raw material of a precursor of a positive electrode active material of a lithium secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The present invention is a flowchart showing a method for producing a manganese sulfate aqueous solution by using a sulfur dioxide gas reduction leaching method according to an embodiment of the present invention.

[0023] Figure 2 FIG. 1 is a flow chart showing the second purification step according to an embodiment of the present invention. DETAILED DESCRIPTION

[0024] The purpose of showing the embodiments of the present invention is to explain the technical spirit of the present invention. The scope of protection claimed in the present invention is not limited to the following embodiments or detailed descriptions of these embodiments.

[0025] The production of manganese sulfate, which is a raw material used as a precursor of a positive electrode active material for lithium-ion secondary batteries, requires a wet reaction, wherein acid leaching must be performed from a solid manganese-containing material.

[0026] In this process, unlike the embodiment of the present invention, a reducing agent such as hydrogen peroxide (H2O2) may be used to generate a reducing atmosphere. In this case, there is a problem of increased process operating costs due to excessive use of the reducing agent to completely leaching manganese.

[0027] The method for producing a manganese sulfate aqueous solution according to an embodiment of the present invention can obtain a high recovery rate and high economic benefit by using a reducing gas containing sulfur dioxide gas (SO2 gas) as a leaching aid.

[0028] Hereinafter, the present invention will be described with reference to the accompanying drawings.

[0029] Figure 1 The present invention is a flowchart showing a method for producing a manganese sulfate aqueous solution by using a sulfur dioxide gas reduction leaching method according to an embodiment of the present invention. Figure 2 FIG. 1 is a flow chart showing the second purification step according to an embodiment of the present invention.

[0030] Reference Figure 1 and 2 The method for producing an aqueous solution of manganese sulfate by using a sulfur dioxide gas reduction leaching method according to an embodiment of the present invention may include: a raw material preparation step S100 of preparing a manganese-containing by-product containing manganese and impurities, a pulverization step and a washing step S200 of pulverizing and washing the manganese-containing by-product, a reduction leaching step S300 of leaching the pulverized manganese-containing by-product pulverized in the pulverization step and the washing step, a neutralization step S400 of neutralizing a leached liquid generated in the reduction leaching step, a first purification step S500 of purifying the neutralized liquid generated in the neutralization step, and a second purification step S600 of further purifying the first purified liquid generated in the first purification step.

[0031] Raw material preparation process S100

[0032] In the raw material preparation step S100, a manganese-containing byproduct containing manganese and impurities may be prepared. In one embodiment, the manganese-containing byproduct may be produced in a zinc wet smelting process. In this case, the manganese-containing byproduct may be prepared together with a zinc process solution in the raw material preparation step S100.

[0033] The manganese-containing byproduct as a manganese-containing raw material for producing an aqueous solution of manganese sulfate may contain at least one of oxides, hydroxides, sulfides, and sulfur oxides. The manganese-containing byproduct may contain manganese in the form of manganese dioxide (MnO2).

[0034] In one embodiment, the manganese-containing by-product may contain at least one of calcium (Ca), potassium (K), lead (Pb), zinc (Zn), magnesium (Mg), sodium (Na) and silicon (Si) as impurities other than manganese (Mn). In one embodiment, the composition of the manganese-containing by-product is shown in Table 1 below. The unit is wt%.

[0035] Table 1

[0036] Mn Ca K Pb Zn Mg Na Si 30 to 45 0.1 to 3.5 0.1 to 3.5 0.1 to 4.0 0.1 to 4.0 0 to 0.05 0.05 to 0.3 0 to 0.05

[0037] In one embodiment, the manganese-containing by-product may contain oxygen (O). For example, most of the components not shown in Table 1 may be oxygen (O).

[0038] Crushing process and washing process S200

[0039] In the crushing process and washing process S200, the manganese-containing by-product may be crushed and washed. The crushing process and washing process S200 correspond to a pretreatment process of the manganese-containing by-product. In the crushing process and washing process S200, the crushing process may be performed to reduce the particle size of the manganese-containing by-product. In addition, the washing process may be performed to remove at least some 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.

[0040] The average particle size of the manganese-containing byproduct after pulverization may be about 1 μm to 25 μm. The average particle size of the manganese-containing byproduct before the pulverization process may be about 500 μm to 900 μm. The average particle size of the manganese-containing byproduct may be reduced to about 1 μm to 25 μm by the pulverization process. Therefore, the leaching efficiency in the reduction leaching process S300 may be improved by reducing the average particle size of the manganese-containing byproduct by the pulverization process before the reduction leaching process S300 is performed. If the average particle size of the manganese-containing byproduct is large, it is substantially difficult to leach in the subsequent reduction leaching process S300 due to low reactivity. That is, if the average particle size of the manganese-containing byproduct is greater than 25 μm, the leaching efficiency will be reduced. For example, the pulverization process may be performed using a mill such as a ball mill or a rod mill.

[0041] In the crushing process and washing process S200, at least some of the impurities in the manganese-containing by-product may be removed. In one embodiment, in the crushing process and washing process S200, the manganese-containing by-product is washed with diluted acid and water to remove at least some of the impurities. In one embodiment, the diluted acid may be at least one of sulfuric acid (H2SO4), hydrochloric acid (HCl) and nitric acid (HNO3). In one embodiment, the concentration of the diluted acid may be 10 g / L to 100 g / L.

[0042] The amount of water introduced for the washing process may be 1.5 to 3 times the amount of the manganese-containing by-products by weight. If the amount of water introduced for the washing process is less than 1.5 times the amount of the manganese-containing by-products, the impurity removal rate will be less than 50%. If the amount of water introduced for the washing process is more than 3 times the amount of the manganese-containing by-products, the impurity removal rate can be improved. However, the increase in the amount of water used in the process will reduce economic feasibility.

[0043] In one embodiment, the pulverizing process and the washing process can be performed simultaneously. The pulverizing process and the washing process can be performed in the same reactor. For example, the pulverizing process and the washing process can be performed simultaneously using a wet pulverizer. Afterwards, some impurities (calcium, potassium, magnesium, sodium, etc.) contained in the manganese-containing by-product can be removed by performing solid-liquid separation. When the pulverizing process and the washing process are performed simultaneously, the process of manufacturing an aqueous solution of manganese sulfate can be simplified. This is because in the process of manufacturing an aqueous solution of manganese sulfate, the subsequent process after the pulverizing process and the washing process involves a reaction in water. In addition, if the pulverizing process and the washing process are performed in the same reactor, the number of reactors can be reduced. In another embodiment, the pulverizing process and the washing process can be performed separately.

[0044] Reduction leaching process S300

[0045] In the reduction leaching process S300, the manganese-containing byproducts crushed in the crushing and washing S200 are leached. The reduction leaching process S300 may be performed after the crushing process and the washing process S200. In the reduction leaching process S300, the crushed manganese-containing byproducts may be leached using an inorganic acid and a reducing gas. The reducing gas may be sulfur dioxide gas (SO2gas). In one embodiment, the reduction leaching process 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.

[0046] In one embodiment, the concentration of sulfur dioxide gas may be 10% or higher, in which case the dissolution rate of manganese may be 99.6% or higher. The sulfur dioxide gas supplied and not participating in the reaction may be recycled and reused in the reduction leaching process S300. If the concentration of sulfur dioxide gas is lower than 10%, the circulation amount of gas other than sulfur dioxide gas increases, which may cause the dissolution rate to decrease. Therefore, it is desirable that the concentration of sulfur dioxide gas is 10% or higher. However, the present invention is not limited thereto. In another embodiment of the present invention, sulfur dioxide gas having a concentration lower than 10% may be used. The gas other than sulfur dioxide gas may be an inert gas, oxygen or air.

[0047] The sulfur dioxide gas may be injected through the injection pipe. For example, the process solution may be stored in a reaction tank, and the sulfur dioxide gas may be injected into the reaction tank through the injection pipe installed at the bottom of the reaction tank. Thus, the sulfur dioxide gas may react with the manganese in the process solution.

[0048] Sulfuric acid and sulfur dioxide gas may be used in the reduction leaching process. In this case, sulfur dioxide gas reacts with water to produce sulfurous acid (Sulfurous acid) through the following reaction formula 1 and reaction formula 2, and manganese is leached from the manganese-containing byproduct in the form of manganese sulfate (MnSO4) in a reducing atmosphere. This can produce a post-leaching solution.

[0049] Reaction 1

[0050] SO2(g)→SO2(aq)

[0051] Reaction 2

[0052] MnO2+SO2(aq)→MnSO4

[0053] The manganese in the manganese-containing byproduct mainly exists in the form of manganese dioxide (MnO2). Since the manganese in the manganese dioxide is tetravalent, the leaching of manganese will not be easy to carry out. On the other hand, the leaching of divalent manganese can be easily carried out. Therefore, in order to leach manganese, the manganese in the manganese dioxide in the manganese-containing byproduct must be reduced to divalent manganese. In this regard, in an embodiment of the present invention, tetravalent manganese can be reduced to divalent manganese by using sulfur dioxide gas as a reducing agent. Thus, a post-leaching solution in the form of manganese sulfate can be manufactured from the manganese-containing byproduct (refer to the above reaction formula 1 and reaction formula 2).

[0054] The reduction leaching process S300 may be performed at a temperature of about 20°C to 60°C. The reduction leaching process S300 is started from room temperature. During the leaching reaction, the internal temperature rises to 60°C due to the exothermic reaction. This may mean that no additional heat source is required. Therefore, the reduction leaching process S300 may be an economical process. The sulfuric acid concentration in the leachate may be 25g / L to 100g / L. The pH of the leachate may be 1 or lower. In one embodiment, in the reduction leaching process S300, not only manganese but also other impurities may be leached. For example, impurities such as calcium (Ca), potassium (K), lead (Pb), zinc (Zn), etc. may be leached together with manganese and may be included in the post-leaching solution.

[0055] The manganese concentration of the leached solution obtained in the reduction leaching step S300 may be about 60 g / L to 100 g / L. For example, the manganese concentration in the leached solution may be 61 g / L to 64 g / L. In view of this, water in an amount of about 1.5 to 3 times the amount of the crushed manganese-containing by-product by weight may be used to dilute the inorganic acid.

[0056] The sulfurous acid generated from the sulfur dioxide gas is used as a leaching solution, which can reduce the amount of inorganic acid used compared to a general acid leaching process. In more detail, sulfurous acid can be produced from sulfur dioxide gas according to the following reaction formula 3, and sulfuric acid can be produced from sulfurous acid according to reaction formula 4. Therefore, it is not necessary to maintain a one-to-one equivalent of inorganic acid and manganese. That is, the amount of inorganic acid used can be reduced.

[0057] [Reaction 3]

[0058] SO2+H2O→H2SO3

[0059] [Reaction 4]

[0060] 2H2SO3+O2→2H2SO4

[0061] Neutralization process S400

[0062] In the neutralization step S400, the post-leaching liquid generated in the reduction leaching step S300 may be neutralized. The neutralization step S400 may be performed after the reduction leaching step S300. When obtaining the post-leaching liquid, if the post-leaching liquid is produced in a high pH atmosphere, a small amount of the post-leaching liquid will be produced. In an embodiment of the present invention, the neutralization step S400 may be performed after the reduction leaching step S300 is performed in an acidic atmosphere with a low pH to obtain a sufficient amount of the post-leaching liquid.

[0063] In the neutralization process S400, a neutralizing agent is added to increase the pH of the post-leaching solution generated in the reduction leaching process S300. The addition of the neutralizing agent may be performed in preparation for the purification process to be performed later. The neutralizing agent may be at least one of a manganese 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, the neutralization process S400 may be performed by using a manganese-containing by-product in the form of a crushed manganese-containing by-product as a neutralizing agent. Due to the addition of the manganese-containing by-product, there is no problem even if the amount of impurities increases. This is because the first purification process S500 and the second purification process S600 are performed after the neutralization process S400.

[0064] If the neutralization process S400 is performed using a manganese-containing byproduct, the amount of the neutralizing agent added separately can be reduced, thereby reducing costs. In addition, the introduction of other impurities can be prevented, and the concentration of manganese in the neutralized liquid can be increased. When a manganese-containing byproduct is used as a neutralizing agent, a reducing gas (e.g., sulfur dioxide gas) can be additionally injected into the neutralization process S400 to dissolve the valuable metals contained in the additionally added manganese-containing byproduct. In this case, the leaching reactor and the neutralization reactor can be performed continuously.

[0065] After the neutralization step S400 is performed, the pH of the neutralized solution may be about 3 to 5, and preferably, may be about 4 to 5.

[0066] First purification step S500

[0067] In the first purification step S500, the neutralized liquid generated in the neutralization step S400 may be purified. The neutralized liquid may be a leached liquid after neutralization. The first purification step S500 is a step of removing impurities in the neutralized liquid after the neutralization step S400.

[0068] The first purification process S500 may be a process for removing impurities by precipitation. In the first purification process S500, at least one of sodium sulfide (Na2S), sodium hydrosulfide (NaSH), ammonium hydrogen sulfide (NH4HS) and hydrogen sulfide (H2S) may be used as a precipitant to remove heavy metal impurities. In addition, in the first purification process S500, at least one of sodium fluoride (NaF), oxalic acid (C2H2O4) and sodium oxalate (Na2C2O4) may be used as a precipitant to remove light metal impurities. This allows the removal of impurities such as zinc, lead, cadmium, cobalt, nickel, calcium, magnesium, etc. In one embodiment, when sodium hydrosulfide (NaSH) is used as a precipitant, a reaction as shown in the following reaction formula 5 occurs. In one embodiment, when sodium fluoride (NaF) is used as a precipitant, a reaction as shown in the following reaction formula 6 occurs.

[0069] [Reaction 5]

[0070] 2M H SO4+2NaSH→Na2SO4+H2SO4+2M H S↓(where M H Heavy metals, such as Zn, Pb, Cd, Co, Ni, Cu, etc.)

[0071] [Reaction formula 6]

[0072] M L SO4+2NaF→Na2SO4+M L F2↓(where M L Light metals, such as Ca, Mg, etc.)

[0073] The first purification process S500 may be performed at a temperature of about 20°C to 60°C.

[0074] A precipitant for removing heavy metal impurities may be added at an equivalent ratio of about 0.8 to 1.4 relative to the heavy metal contained in the neutralized liquid. If a precipitant for removing heavy metal impurities is added at an equivalent ratio of less than 0.8 relative to the heavy metal, the heavy metal removal rate may be 85% or less and a complete reaction may not occur. If a precipitant for removing heavy metal impurities is added at an equivalent ratio of more than 1.4 relative to the heavy metal, impurities caused by the precipitant may be excessively introduced, which may have a negative impact on the process and reduce economic feasibility.

[0075] A precipitant for removing light metal impurities may be added at an equivalent ratio of about 1.0 to 2.5 relative to the light metal contained in the neutralized liquid. If a precipitant for removing light metal impurities is added at an equivalent ratio of less than 1.0 relative to the light metal, the light metal removal rate may be 90% or less and a complete reaction may not occur. If a precipitant for removing light metal impurities is added at an equivalent ratio of more than 2.5 relative to the light metal, impurities caused by the precipitant may be excessively introduced, which may have a negative impact on the process and may reduce economic feasibility.

[0076] After the first purification step S500, the contents of zinc, lead, cadmium, nickel, copper and cobalt in the first purified liquid can be reduced to 5 mg / L or less. After the first purification step S500, the contents of calcium and magnesium in the first purified liquid can be reduced to 50 mg / L or less.

[0077] Second purification step S600

[0078] In the second purification process S600, the first purified liquid generated in the first purification process S500 may be further purified. The second purification process S600 may be performed after the first purification process S500. The second purification process S600 may be a process of removing impurities by solvent extraction. An organic extractant may be used in the second purification process S600 to remove impurities such as sodium (Na) and potassium (K). In one embodiment, the second purification process S600 may include a loading process S610, a scrubbing process S620, and a stripping process S630. As the organic extractant, at least one of di-2-ethylhexyl phosphoric acid, mono-2-ethylhexyl (2-ethylhexyl) phosphonate, and bis (2,4,4-trimethylpentyl) phosphinic acid may be used.

[0079] The loading process S610 may be a process of extracting manganese contained in the first purified liquid into an organic phase. The loading process S610 may be a process of extracting manganese contained in the first purified liquid generated in the first purification process S500 into an organic phase using an organic extractant. The reaction temperature in the loading process S610 may be about 30° C. to 50° C. If the reaction temperature in the loading process S610 is about 30° C. to 50° C., the reaction of the organic extractant may be most active. If the reaction temperature in the loading process S610 is 30° C. or lower, the viscosity of the organic extractant increases and the reactivity decreases. If the reaction temperature in the loading process S610 exceeds 50° C., the amount of volatilized components is large, which reduces the process efficiency. The volume ratio of the amount of the organic phase added in the loading process S610 to the aqueous phase may be about 3 to 6. If the volume ratio of the amount of the organic phase to the aqueous phase in the loading process S610 is less than 3, the combination of the target metal and the organic extractant is incomplete, and the extraction rate may be 90% or less. If the volume ratio of the amount of the organic phase to the aqueous phase in the loading process S610 exceeds 6, the process cost may increase due to excessive use of the organic extractant. The pH range in the loading process S610 may be about 4 to 5. In order to adjust the pH range in the loading process S610 to 4 to 5, at least one of sodium hydroxide (NaOH), sodium carbonate (Na2CO3), and sodium sulfate (Na2SO4) may be used.

[0080] When the manganese extraction into the organic phase is completed by mixing the aqueous phase and the organic phase, phase separation occurs due to the difference in specific gravity between the organic phase and the aqueous phase. The organic phase containing manganese may be subjected to a washing step S620.

[0081] The washing process S620 may be a process of washing the organic phase from which manganese has been extracted with water. The washing process S620 may be a process of removing impurities in the loaded organic phase using water. The reaction temperature in the washing process 620 may be about 30°C to 50°C. If the reaction temperature in the washing process 620 is about 30°C to 50°C, the reaction of the organic extractant may be most active. If the reaction temperature in the washing process 620 is 30°C or lower, the viscosity of the organic extractant will increase and the reactivity will decrease. If the reaction temperature in the washing process 620 exceeds 50°C, the amount of volatilized components may be large and the process efficiency may decrease. The volume ratio of the organic phase added in the washing process 620 to the aqueous phase may be about 5 to 10. The washing process 620 is a process of washing impurities other than the target metal. If the volume ratio of the organic phase added in the washing process 620 to the aqueous phase is less than 5, the impurity removal rate will be 85% or less. If the volume ratio of the organic phase added to the aqueous phase in the washing process 620 exceeds 10, the impurities can be completely removed. However, the process cost will increase due to the unnecessary water consumption. Washing the manganese-containing organic phase with water can remove impurities including sodium and potassium contained in the organic phase. The manganese-containing organic phase whose purity has been improved by removing impurities can be subjected to the removal process S630.

[0082] In the removal process S630, a second purified liquid may be generated by adding sulfuric acid to the organic phase after the cleaning process S620. The second purified liquid may be an aqueous solution of manganese sulfate. That is, manganese may be recovered in the form of an aqueous solution of manganese sulfate by adding sulfuric acid to the organic phase after the cleaning process S620 in the removal process S630. The removal process S630 may be a process of stripping manganese contained in the organic phase to the aqueous phase. The reaction temperature in the removal process S630 may be about 30° C. to 50° C. If the reaction temperature in the removal process S630 is about 30° C. to 50° C., the reaction of the organic extractant may be most active. If the reaction temperature in the removal process S630 is 30° C. or less, the viscosity of the organic extractant may increase and the reactivity may decrease. If the reaction temperature in the removal process S630 exceeds 50° C., the amount of the volatilized component may be large, which may reduce the process efficiency. The volume ratio of the organic phase added in the removal process S630 to the aqueous phase may be about 5 to 10. If the volume ratio of the organic phase added in the removal process S630 to the aqueous phase is less than 5, manganese may be completely extracted, but the amount of water used will increase. Therefore, the manganese content in the manganese sulfate aqueous solution will decrease. If the volume ratio of the organic phase added in the removal process S630 to the aqueous phase exceeds 10, the stripping efficiency of manganese will decrease. The pH range in the removal process S630 may be about 0.5 to 1.5. Sulfuric acid (H2SO4) may be used to adjust the pH range in the removal process S630 to about 0.5 to 1.5.

[0083] In this way, 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 an embodiment of the present invention may have a manganese content of about 115 g / L to 135 g / L. The composition of the manganese sulfate aqueous solution is shown in Table 2 below.

[0084] Table 2

[0085]

[0086] Therefore, according to the embodiments of the present invention, manganese sulfate, in particular a high-purity manganese sulfate aqueous solution, can be produced from manganese-containing by-products.

[0087] In the case of the reduction leaching process included in the embodiment of the present invention, unlike leaching using a conventional reducing agent, the use of a reducing gas can obtain a relatively high recovery rate and high economic benefits.

[0088] The manganese sulfate produced according to the embodiment of the present invention can be suitably used as a raw material for a precursor of a positive electrode active material for a lithium secondary battery.

[0089] Example 1

[0090] (Raw material preparation process)

[0091] A manganese-containing by-product containing the elements shown in Table 3 below was prepared.

[0092] Table 3 (Unit: wt%)

[0093] Mn Ca K Pb Zn Mg Na Si 40.4 1.2 2.1 2.2 2.2 0.02 0.06 0.01

[0094] (Crushing and washing process)

[0095] In order to improve the leaching efficiency, the manganese-containing by-products were crushed and washed. Thus, some water-soluble impurities such as magnesium, sodium and potassium were removed. The removal rate of magnesium was 55%, sodium was 55% and potassium was 62%. The average particle size of the manganese-containing by-products before crushing was about 800 μm. After crushing for 30 minutes, the average particle size of the crushed manganese-containing by-products was about 5 μm.

[0096] (Reduction leaching process)

[0097] Subsequently, 0.4 kg of the crushed manganese-containing by-product was dissolved at room temperature for 1 hour using 30 g / L sulfuric acid, a solid-liquid ratio of 215 g / L, and 10 NL / hr of 10% sulfur dioxide gas to obtain a leached solution having a manganese concentration of 61 g / L to 64 g / L. The solid-liquid ratio is the ratio of the by-product to the sulfuric acid.

[0098] (Neutralization process)

[0099] Next, 0.1 kg of the crushed manganese-containing byproduct and 2 NL / hr of 10% sulfur dioxide gas were added to the leached solution, and neutralized at 50° C. for 1 hour to obtain a neutralized solution having a manganese concentration of 80 g / L. The dissolution rates of manganese and zinc were 99.6% or more.

[0100] (First purification step)

[0101] Subsequently, a precipitation process is performed to remove impurities present in the neutralized solution. First, 1.2 equivalents of sodium hydrosulfide (NaSH) are added to the neutralized solution to remove heavy metal impurities, and the mixture is reacted at a temperature of 60° C. for 2 hours to remove 99% or more of lead and zinc through sulfide-based precipitation.

[0102] Next, 2.0 equivalents of sodium fluoride (NaF) were added to remove light metal impurities. The mixture was reacted at 70° C. for 2 hours to remove 30 mg / L of calcium and magnesium through fluorine-based precipitation.

[0103] (Second purification step)

[0104] Next, a solvent extraction process is performed to recover manganese from the first purified liquid after the first purification process that has been purified by precipitation. At this time, 30% di-2-ethylhexyl phosphoric acid (di-2-ethylhexyl phosphoric acid) extractant is used. The pH is 4.5, the volume ratio of the organic phase to the aqueous phase is 5, and the reaction is performed at a temperature of 35°C. The volume ratio of the organic phase to the aqueous phase can be expressed as O / A (Organic / Aqueous). Thus, manganese is loaded from the aqueous phase to the organic phase, and the manganese remaining in the aqueous phase at a content of 0.1 g / L or less is recovered.

[0105] Next, the organic phase containing manganese was reacted with water at a temperature of 35° C. and an O / A of 10. Thus, potassium, magnesium, sodium, etc. were washed. At this time, the contents of the main impurities removed were 30 mg / L of potassium, 1 mg / L of magnesium, and 350 mg / L of sodium.

[0106] Next, in order to recover the manganese contained in the washed organic phase into the aqueous phase, sulfuric acid was reacted with the organic phase at a temperature of 35° C. and an O / A of 10. Thus, manganese was recovered as an aqueous solution of manganese sulfate. The solubility of manganese was at the level of 99.6%.

[0107] Example 2

[0108] The average particle size of the crushed manganese-containing byproduct obtained by the crushing process and the washing process with a reaction time of 10 minutes was 130 μm. Other conditions, such as the reaction conditions of the leaching process, were the same as those of Example 1. The reaction conditions of the leaching process include, for example, solid-liquid ratio, sulfuric acid concentration, sulfur dioxide gas concentration, reaction time, reaction temperature, etc. In this case, the dissolution rate of manganese in the reduction leaching process was 82%.

[0109] Example 3

[0110] In the reduction leaching process of Example 1, the concentration of sulfur dioxide gas was changed to 99.9%. Other conditions were the same as those of Example 1. The leaching results were the same as those of Example 1. A post-leaching solution of manganese having a manganese dissolution rate of 99.6% or more and a manganese concentration of 61 g / L to 64 g / L was obtained. That is, the post-leaching solution was obtained regardless of the concentration of sulfur dioxide gas. When the concentration of sulfur dioxide gas was 10% (low concentration) and when the concentration of sulfur dioxide gas was 99.9% (high concentration), a manganese dissolution rate at the level of 99% was obtained. The dissolution rate was high regardless of the concentration of sulfur dioxide gas.

[0111] Comparative Example

[0112] Comparative Examples for comparison with the embodiment will be described below. In Comparative Examples 1 to 4, the conditions other than the following process conditions are the same as those of Embodiment 1.

[0113] Comparative Example 1

[0114] In the leaching process, manganese sulfate was produced by adding 300 g / L of sulfuric acid to the manganese-containing byproduct without adding a reducing agent and then roasting the mixture at a temperature of 600° C. for 5 hours. The manganese sulfate was dissolved in water to obtain a leachate. The dissolution rate of manganese was 75%.

[0115] Comparative Example 2

[0116] In the leaching process, sodium oxalate is added as a reducing agent in an amount of 1 to 3 times the molar mass of manganese to the manganese-containing byproduct. At this time, the dissolution rate of manganese is 95% or more, but impurities such as sodium are additionally generated. Such impurities increase the cost of additives in subsequent processes.

[0117] Comparative Example 3

[0118] In the first purification process, 0.75 equivalent of sodium hydrosulfide was added to the manganese-containing byproduct to remove heavy metal impurities. The removal rates of the main impurities were 98.7% for lead and 65.2% for zinc.

[0119] Comparative Example 4

[0120] In the first purification process, 0.5 times the equivalent ratio of sodium fluoride was added to the manganese-containing byproduct to remove light metal impurities. 52% of calcium, which was the main impurity, was removed.

[0121] Although the technical spirit of the present invention has been described through some embodiments and examples shown in the accompanying drawings, it should be understood that various substitutions, modifications and changes can be made without violating the technical spirit and scope of the present invention understood by ordinary technicians in the field. In addition, such substitutions, modifications and changes should be interpreted as being within the scope of the invention.

Claims

1. A method for producing an aqueous solution of manganese sulfate by using sulfur dioxide gas reduction leaching method, characterized in that: include: A raw material preparation step, preparing a manganese-containing byproduct containing manganese and impurities; A crushing step and a washing step, crushing and washing the manganese-containing by-product; a reduction leaching step of leaching the crushed manganese-containing byproduct obtained through the crushing step and the washing step; A neutralization step of neutralizing the post-leaching liquid generated in the reduction leaching step; a first purification step of purifying the neutralized liquid generated in the neutralization step; and A second purification step is to further purify the first purified liquid generated in the first purification step, Wherein, the reduction leaching process is carried out using inorganic acid and sulfur dioxide gas.

2. The method for producing an aqueous solution of manganese sulfate by sulfur dioxide gas reduction leaching according to claim 1, characterized in that: The average particle size of the crushed manganese-containing by-product is 1 μm to 25 μm.

3. The method for producing an aqueous solution of manganese sulfate by sulfur dioxide gas reduction leaching according to claim 1 or 2, characterized in that: The pulverizing step and the washing step are performed in the same reactor.

4. The method for producing an aqueous solution of manganese sulfate by sulfur dioxide gas reduction leaching according to claim 1 or 2, characterized in that: In the pulverizing step and the washing step, the manganese-containing by-product is washed with diluted acid and water. The diluted acid is at least one of sulfuric acid, hydrochloric acid and nitric acid, The concentration of the diluted acid is 10 g / L to 100 g / L.

5. The method for producing an aqueous solution of manganese sulfate by sulfur dioxide gas reduction leaching according to claim 4, characterized in that: In terms of weight ratio, the amount of the water added in the washing process is 1.5 to 3 times the amount of the manganese-containing by-product.

6. The method for producing an aqueous solution of manganese sulfate by sulfur dioxide gas reduction leaching according to claim 1 or 2, characterized in that: The neutralization step is performed using the manganese-containing by-product as a neutralizing agent.

7. The method for producing an aqueous solution of manganese sulfate by sulfur dioxide gas reduction leaching according to claim 6, characterized in that: In the neutralization step, sulfur dioxide gas is additionally injected.

8. The method for producing an aqueous solution of manganese sulfate by sulfur dioxide gas reduction leaching according to claim 1 or 2, characterized in that: The first purification process includes a process of removing the impurities by a precipitation method. The second purification process includes a process of removing the impurities by solvent extraction.

9. The method for producing an aqueous solution of manganese sulfate by sulfur dioxide gas reduction leaching according to claim 8, characterized in that: The first purification process is performed by adding at least one of sodium sulfide, sodium hydrogen sulfide, ammonium hydrogen sulfide and hydrogen sulfide as a precipitant to cause a precipitation reaction of the impurities.

10. The method for producing an aqueous solution of manganese sulfate by using sulfur dioxide gas reduction leaching method according to claim 8, characterized in that: The second purification step comprises: a loading step of extracting manganese contained in the first purified liquid into an organic phase; a washing step of washing the organic phase from which manganese has been extracted with water; and In a removal process, sulfuric acid is added to the organic phase after the washing process to recover manganese in the form of a manganese sulfate aqueous solution.

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