Method for separating manganese from solution containing manganese and calcium

Abstract

Provided is a method for separating manganese having a very high purity from a solution containing manganese and calcium. This method for separating manganese from a solution containing manganese and calcium comprises: a first manganese extraction step for adding a first acidic organophosphorus compound to a solution containing manganese and calcium to extract manganese and calcium; a first manganese reverse extraction step for reversely extracting manganese and calcium from the extract obtained in the first manganese extraction step; a second manganese extraction step for adding a second acidic organophosphorus compound to the manganese-containing solution obtained in the first manganese reverse extraction step to extract manganese; and a second manganese reverse extraction step for reversely extracting manganese from the extract obtained in the second manganese extraction step.

Description

Method for separating manganese from liquid containing manganese and calcium

[0001] The present invention relates to a method for separating manganese from a liquid containing manganese and calcium.

[0002] In recent years, with the widespread use of lithium ion batteries, methods have been investigated for recovering valuable metals such as cobalt, nickel, manganese, and lithium from discarded lithium ion batteries and reusing them as materials for the lithium ion batteries.

[0003] Conventionally, when recovering the valuable metals from the waste lithium-ion batteries, the waste lithium-ion batteries are subjected to a heat treatment (roasting), and then crushed, classified, and the like to obtain a powder containing the valuable metals. From the powder, cobalt, nickel, manganese, and lithium are separated and refined by a wet process (see, for example, Patent Document 1).

[0004] In the present invention, "waste lithium ion batteries" refers to used lithium ion batteries that have reached the end of their life as battery products, lithium ion batteries discarded as defective products during the manufacturing process, and residual positive and negative electrode materials used in the manufacturing process. Furthermore, powders containing positive and negative electrodes obtained from the waste lithium ion batteries are referred to as active material powders. Furthermore, "impurities" refers to metals contained in the active material powder that do not require recovery.

[0005] The powder containing valuable metals contains calcium, which is believed to be derived from the aluminum used in the casing or current collector (electrode foil) of the lithium-ion battery. Separating and purifying calcium and manganese in wet processes is extremely difficult, and calcium is contaminated as an impurity in the recovered aqueous manganese compound solution. Therefore, a method for separating manganese and calcium is desired. Patent Document 2 discloses a method for recovering an aqueous manganese compound solution, which includes the steps of: dissolving the valuable metal contained in the powder containing valuable metals in a first acid solution to obtain a valuable metal solution containing manganese and calcium as an impurity; performing a first solvent extraction from the valuable metal solution using bis(2-ethylhexyl) hydrogen phosphate as an extractant; performing a second solvent extraction from the residual solution obtained after the first solvent extraction using bis(2,4,4-trimethylpentyl)phosphinic acid as an extractant; and stripping the extract obtained by the second solvent extraction using the second acid solution as an extractant to obtain an aqueous manganese compound solution as a stripped solution.

[0006] Japanese Patent No. 7060899 Japanese Patent Application Laid-Open No. 2022-118636

[0007] In recent years, there has been a demand for a method for further improving the purity of manganese separated from a liquid containing manganese and calcium as an impurity.

[0008] The problem to be solved by the present invention is to provide a method for separating highly pure manganese from a liquid containing manganese and calcium.

[0009] The present inventors have conducted extensive research in light of the above-mentioned problems and have found that highly pure manganese can be isolated by repeatedly adding an acidic organophosphorus compound to a liquid containing manganese and calcium to extract manganese, and then stripping manganese from the resulting extract. The present invention was completed based on these findings.

[0010] The present invention relates to a method for separating manganese from a liquid containing manganese and calcium, comprising: a first manganese extraction step of adding a first acidic organophosphorus compound to a liquid containing manganese and calcium to extract manganese and calcium; a first manganese stripping step of strip-extracting manganese and calcium from the extract obtained in the first manganese extraction step; a second manganese extraction step of adding a second acidic organophosphorus compound to the manganese-containing liquid obtained in the first manganese stripping step to extract manganese; and a second manganese stripping step of strip-extracting manganese from the extract obtained in the second manganese extraction step.

[0011] The present invention preferably further includes the following steps: a dissolving step of dissolving active material powder obtained by pretreating waste lithium-ion batteries in a mineral acid to obtain an acid solution; a neutralization step of neutralizing the acid solution with an alkali; a cobalt extraction step of extracting cobalt from the extraction residue obtained in the first manganese extraction step using a first organic solvent as an extractant; a nickel extraction step of extracting nickel from the extraction residue of the cobalt extraction step using a second organic solvent as an extractant to obtain a first aqueous lithium salt solution as an extractant; and a membrane electrolysis step of subjecting the first aqueous lithium salt solution to membrane electrolysis using an ion exchange membrane to obtain an aqueous lithium hydroxide solution, an acid, and a second aqueous lithium salt solution that is more dilute than the first aqueous lithium salt solution, wherein the aqueous lithium hydroxide solution obtained in the membrane electrolysis step is reused in at least one selected from the group consisting of the neutralization step, the first manganese extraction step, the second manganese extraction step, the cobalt extraction step, and the nickel extraction step, and the acid obtained in the membrane electrolysis step is reused as the mineral acid used in the dissolving step.

[0012] Preferably, the first acidic organophosphorus compound comprises 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester, and the second acidic organophosphorus compound comprises bis(2,4,4-trimethylpentyl)phosphinic acid. Preferably, the first manganese extraction step is carried out at a pH range of 1.0 to 3.0, and the second manganese extraction step is carried out at a pH range of 2.5 to 5.0. The mineral acid preferably comprises at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, and more preferably comprises hydrochloric acid. Preferably, an alkali containing sodium hydroxide is added to the extraction residue obtained in the second manganese extraction step. The electricity used in the membrane electrolysis step preferably comprises electricity obtained from renewable energy, and more preferably comprises electricity obtained from at least one selected from the group consisting of solar power generation, wind power generation, geothermal power generation, hydroelectric power generation, and biomass power generation.

[0013] The method for separating manganese of the present invention provides a method for separating highly pure manganese from a liquid containing manganese and calcium.

[0014] The present invention relates to a method for separating manganese from calcium, and more particularly to a method for separating manganese from calcium.

[0015] The present invention will be described in more detail. Unless otherwise specified, the "to" in a numerical range indicates a range from above to below, and both end values ​​are included. When a numerical range is indicated, the upper and lower limits can be combined as appropriate, and the resulting numerical range is also considered to be disclosed. Furthermore, in the description of the drawings, identical elements are given the same reference numerals, and redundant explanations will be omitted. Also, the dimensional proportions in the drawings have been exaggerated for the sake of explanation and may differ from the actual proportions.

[0016] The method of the present invention for separating manganese from a liquid containing manganese and calcium (hereinafter, sometimes referred to as the Mn separation method) includes a first manganese extraction step of adding a first acidic organophosphorus compound to a liquid containing manganese and calcium to extract manganese and calcium.

[0017] The liquid containing manganese and calcium can be obtained by carrying out, for example, a dissolving step, a neutralizing step, and a manganese extraction step, which will be described later.

[0018] The first acidic organophosphorus compound is not limited to a specific phosphorus compound. The acidic organophosphorus compound preferably includes at least one selected from the group consisting of di(2-ethylhexyl)phosphate (D2EHPA), phosphonic acid esters, bis(2,4,4-trimethylpentyl)phosphinic acid, and 2-ethylhexylphosphonic acid mono 2-ethylhexyl ester, more preferably includes D2EHPA, and even more preferably is D2EHPA. The first acidic organophosphorus compound may be diluted with a hydrocarbon such as kerosene or decane, or a third petroleum product. A typical example of the third petroleum product is MC531 manufactured by Tobu Chemical Co., Ltd.

[0019] The first acidic organic phosphorus compound is commercially available, and examples thereof include PC-88A manufactured by Daihachi Chemical Industry Co., Ltd. as a phosphonate ester and CYANEX272 manufactured by Solvay as a bis(2,4,4-trimethylpentyl)phosphinic acid.

[0020] The pH during the first manganese extraction step is preferably adjusted to a range of 1.0 to 3.0. When the pH is within this range, the purity of the manganese separated in the second manganese stripping step described below is higher.

[0021] One embodiment of the Mn separation method of the present invention will be described in more detail with reference to the accompanying drawings. As shown in Figure 1, one embodiment of the Mn separation method of the present invention may start with an active material powder 1.

[0022] The active material powder 1 will now be described. When the used lithium-ion batteries are used lithium-ion batteries whose battery life as a battery product has expired or lithium-ion batteries discarded as defective products during the manufacturing process, they are first subjected to a discharge treatment. Various highly safe methods, such as resistance discharge, can be used for the discharge treatment. After discharging all remaining charge, openings are formed in the casings of the used lithium-ion batteries. The batteries are then heat-treated (roasted) at a temperature ranging from 100 to 800°C, or the batteries are pulverized in a pulverizer such as a hammer mill or jaw crusher without being heat-treated. The casings, current collectors, and other components of the used lithium-ion batteries are removed by sieving (classification), thereby obtaining the active material powder. Alternatively, the used lithium-ion batteries after the discharge treatment may be pulverized in the pulverizer, the casings, current collectors, and other components are removed by sieving, and the active material powder 1 may be obtained by heat-treating the batteries at a temperature within the range.

[0023] When the used lithium ion batteries are residual positive electrode materials or the like used in commercialization in a manufacturing process, the active material powder may be obtained by pulverizing the used lithium ion batteries in the pulverizer after heat treatment at a temperature in the above range or without heat treatment without performing the discharge treatment and forming openings, and removing current collectors and the like by sieving.Furthermore, the used lithium ion batteries may be pulverized in the pulverizer, removing current collectors and the like by sieving, and then heat treatment at a temperature in the above range or without heat treatment to obtain the active material powder.

[0024] The Mn separation method of the present invention may include a dissolving step (STEP 1 in FIG. 1 ) of dissolving the active material powder 1 in a mineral acid to obtain an acid solution. The active material powder 1 may contain valuable metals such as iron, aluminum, manganese, calcium, cobalt, and nickel in addition to lithium. The mineral acid preferably includes at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably includes hydrochloric acid, and even more preferably is hydrochloric acid.

[0025] The Mn separation method of the present invention may include a neutralization step (STEP 2 in FIG. 1 ) of neutralizing the acid solution with an alkali. The alkali may be added in at least one form selected from the group consisting of an aqueous solution and a solid. The alkali preferably includes at least one selected from the group consisting of an alkali metal hydroxide and ammonia. The alkali metal constituting the alkali metal hydroxide preferably includes at least one selected from the group consisting of lithium, sodium, potassium, rubidium, cesium, and francium, more preferably includes lithium, sodium, and potassium, even more preferably lithium, sodium, or potassium, and particularly preferably lithium.

[0026] The liquid containing manganese and calcium obtained in the neutralization step is subjected to the first manganese extraction step. The extract 2a obtained in the first manganese extraction step is subjected to scrubbing (STEP 3-1 in FIG. 2 ) using a mineral acid or an aqueous solution of a mineral salt, and the aqueous solution after scrubbing may be returned to the first manganese extraction step. In particular, when the extract 2a obtained in the first manganese extraction step contains valuable metals other than manganese, such as cobalt and nickel, the valuable metals other than manganese are recovered by scrubbing. The mineral acid preferably contains at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably hydrochloric acid, and even more preferably hydrochloric acid. The mineral acid contained in the aqueous solution of a mineral salt contains at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid, more preferably sulfuric acid, and even more preferably sulfuric acid.

[0027] The Mn separation method of the present invention includes a first manganese stripping step (STEP 3-2 in FIG. 2 ) in which manganese is stripped from the extract obtained in the first manganese extraction step, which has been scrubbed as needed.

[0028] The Mn separation method of the present invention includes a second manganese extraction step (STEP 3-3 in FIG. 2 ) in which a second acidic organophosphorus compound is added to the manganese-containing liquid obtained in the first manganese stripping step to extract manganese.

[0029] The second acidic organophosphorus compound is not limited to a specific phosphorus compound. The second acidic organophosphorus compound preferably includes at least one selected from the group consisting of bis(2,4,4-trimethylpentyl)phosphinic acid, D2EHPA, phosphonic acid esters, and 2-ethylhexylphosphonic acid mono 2-ethylhexyl ester, more preferably includes bis(2,4,4-trimethylpentyl)phosphinic acid, and even more preferably bis(2,4,4-trimethylpentyl)phosphinic acid. The second acidic organophosphorus compound may be diluted with a hydrocarbon such as kerosene or decane, or a third petroleum product. A typical example of the third petroleum product is MC531 manufactured by Tobu Chemical Co., Ltd.

[0030] The pH during the second manganese extraction step is preferably adjusted to a range of 2.5 to 5.0. When the pH is within this range, the purity of the manganese separated in the second manganese stripping step described below is higher.

[0031] The residual liquid obtained in the second manganese extraction step is a calcium-containing liquid 3a containing calcium. Preferably, an alkali containing sodium hydroxide is added to the residual liquid to recover calcium. If the residual liquid contains manganese, it may be subjected to the second manganese extraction step again. By repeating this process, the manganese recovery rate can be increased.

[0032] The extract 2b obtained in the second manganese extraction step is subjected to scrubbing (STEP 3-4 in FIG. 2), and the aqueous solution after the scrubbing may be returned to the second manganese extraction step.

[0033] The Mn separation method of the present invention includes a second manganese stripping step (STEP 3-5 in FIG. 2 ) in which manganese is stripped from the extract obtained in the second manganese extraction step, which has been scrubbed as needed. The extract may be stripped with sulfuric acid, for example, to recover manganese sulfate 2A. Since calcium, which could not be completely removed by conventional techniques, has been removed, the purity of the manganese sulfate 2A is very high.

[0034] The bottom solution from the first manganese extraction step is a solution containing lithium, cobalt, and nickel. If the bottom solution contains manganese, it may be subjected to the first manganese extraction step again. Repeating the first manganese extraction step further increases the manganese recovery rate. The Mn separation method of the present invention may include a cobalt extraction step (STEP 4 in FIG. 1 ) in which cobalt is extracted from the bottom solution from the first manganese extraction step using a first organic solvent as an extractant, and a nickel extraction step (STEP 6 in FIG. 1 ) in which nickel is extracted from the bottom solution from the cobalt extraction step using a second organic solvent as an extractant to obtain a first lithium salt aqueous solution as an extractant.

[0035] When the alkali used in the neutralization step is at least one selected from the group consisting of sodium hydroxide and potassium hydroxide, the first lithium salt aqueous solution and at least one salt of sodium and potassium are separated from the aqueous alkali mixed salt solution obtained in the nickel extraction step by the method disclosed in Japanese Patent No. 7084669. The lithium salt contained in the first lithium salt aqueous solution becomes lithium chloride when hydrochloric acid is used in the dissolution step.

[0036] The first and second organic solvents each preferably contain at least one organic phosphorus compound selected from the group consisting of a phosphate ester, a phosphonate ester, a phosphinic acid, and a phosphine oxide, more preferably an organic phosphorus compound, and even more preferably bis(2,4,4-trimethylpentyl)phosphinic acid. Examples of neutral phosphate esters include tributyl phosphate (TBP), and examples of phosphine oxides include tri-n-octylphosphine (TOPO).

[0037] The first and second organic solvents may be diluted with a hydrocarbon such as kerosene or decane, or a third petroleum product, such as MC531 manufactured by Tobu Chemical Co., Ltd.

[0038] Preferably, the cobalt extraction step is carried out at a pH in the range of 3.0 to 4.5, and the nickel extraction step is carried out at a pH in the range of 5.0 to 6.5.

[0039] Although not shown in Figure 1, after each of the cobalt extraction step and the nickel extraction step, scrubbing of each extract solution may be performed, and the resulting aqueous solution may be returned to the corresponding step. Unwanted valuable metals are extracted from each extract solution. Scrubbing can remove these unwanted valuable metals, improving the quality of the recovered metals. Furthermore, since the valuable metals are returned to each step along with the scrubbed aqueous solution, they can be recovered later, thereby increasing the recovery rate of the valuable metals. The extract solutions from each step may be back-extracted with, for example, sulfuric acid, to recover the valuable metals as sulfates 2B and 2C.

[0040] The Mn separation method of the present invention may next include a membrane electrolysis step of performing membrane electrolysis on the first lithium salt aqueous solution using an ion exchange membrane in STEP 7. The membrane electrolysis step in STEP 7 can be performed using, for example, an electrolytic cell 11 shown in FIG.

[0041] The electrolytic cell 11 is provided with an anode plate 12 on one of its inner surfaces and a cathode plate 13 on the inner surface opposite the anode plate 12, the anode plate 12 being connected to an anode 14 of a power supply, and the cathode plate 13 being connected to a cathode 15 of the power supply. The electrolytic cell 11 is also partitioned by an ion exchange membrane 16 into an anode chamber 17 containing the anode plate 12 and a cathode chamber 18 containing the cathode plate 13.

[0042] In the electrolytic cell 11, when membrane electrolysis is performed by supplying, for example, lithium chloride as the first lithium salt aqueous solution to the anode chamber 17, chloride ions are converted into chlorine gas (Cl) on the anode plate 12. ２ ), while the lithium ions migrate through the ion exchange membrane 16 to the cathode chamber 18.

[0043] In the cathode chamber 18, water (H ２ O) is hydroxide ion (OH － ) and hydrogen ions (H ＋ ) and hydrogen ions are ionized into hydrogen gas (H ２ ), while hydroxide ions combine with lithium to produce a lithium hydroxide aqueous solution 3.

[0044] The electricity used in the membrane electrolysis step preferably includes electricity obtained from renewable energy, and more preferably includes electricity obtained from at least one selected from the group consisting of solar power generation, wind power generation, geothermal power generation, hydroelectric power generation, and biomass power generation.

[0045] The hydrogen gas (H ２ ) and chlorine gas (Cl ２ ) to obtain hydrochloric acid as mineral acid 4, which can be used to dissolve active material powder 1 in STEP 1.

[0046] The lithium hydroxide aqueous solution 3 obtained by the membrane electrolysis is crystallized in STEP 7 to form lithium hydroxide monohydrate (LiOH·H ２ O), and by carbonating it in STEP 8, lithium carbonate (Li ２ CO ３ The carbonation can be carried out by converting the lithium hydroxide aqueous solution 3 into carbon dioxide gas (CO ２ ) can be reacted with

[0047] When the lithium hydroxide aqueous solution 3 is used in at least one selected from the group consisting of the manganese extraction step, the cobalt extraction step, and the nickel extraction step, the lithium hydroxide aqueous solution 3 is added to the extraction solvent in each of the extraction steps. As a result, the added lithium is not discharged outside the system and is recycled. The extraction solvent used in at least one selected from the group consisting of the manganese extraction step, the cobalt extraction step, and the nickel extraction step is a cation exchange extractant, and therefore, if used continuously, the liquid becomes acidic and the extraction rate decreases. However, by adding the lithium hydroxide aqueous solution 3, the decrease in extraction rate can be suppressed. Furthermore, the lithium hydroxide aqueous solution 3 may be used in the neutralization step.

[0048] In the membrane electrolysis step, the first lithium salt aqueous solution is subjected to membrane electrolysis, resulting in the production of a second lithium salt aqueous solution that is more dilute than the first lithium salt aqueous solution. Therefore, in the Mn separation method of the present invention, the second lithium salt aqueous solution may be concentrated in the concentration step of STEP 10 and added to the first lithium salt aqueous solution. The concentration step of STEP 10 can be performed using, for example, a reverse osmosis membrane (RO membrane).

[0049] In the Mn separation method of the present invention, since there is no unnecessary alkali source other than lithium, the lithium hydroxide obtained by membrane electrolysis can be returned to the process as is, making it possible to recycle resources.

[0050] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0051] In the examples and comparative examples, the content of valuable metals in each acid solution was measured by an inductively coupled plasma optical emission spectrometer (ICP-OES) using an OPTIMA 8300 manufactured by PerkinElmer.

[0052] Example 1 Active material powder was dissolved in hydrochloric acid adjusted to 9 to 10 mol / L, and then neutralized with a 3 mol / L aqueous solution of lithium hydroxide to obtain 180 L of a solution containing manganese and calcium at the concentrations shown in Table 1.

[0053]

[0054] 80 L of 1 mol / L D2EHPA diluted with MC531 (manufactured by Tobu Chemical Co., Ltd.) was added to 80 L of the manganese- and calcium-containing liquid, and lithium hydroxide was added to adjust the equilibrium pH to 2.5 to perform a first manganese extraction, yielding 80 L of extract obtained in the first manganese extraction step. 5 L of 1.8 mol / L sulfuric acid was added to the 80 L of extract obtained in the first manganese extraction step to perform a first manganese strip extraction, yielding 5 L of a solution containing manganese and calcium at the concentrations shown in Table 2. The cobalt content in the liquid obtained in the first manganese strip extraction step was reduced compared to the cobalt content in the liquid shown in Table 1, demonstrating that cobalt had been removed in the first manganese strip extraction step.

[0055]

[0056] 50 L of 1 mol / L bis(2,4,4-trimethylpentyl)phosphinic acid diluted with MC531 manufactured by Tobu Chemical Co., Ltd. was added to 5 L of the liquid shown in Table 2, and sodium hydroxide was added to adjust the pH to 2.5 to perform a second manganese extraction (second manganese extraction step), yielding 50 L of extract. 5 L of 3 mol / L sulfuric acid was added to the 50 L of extract obtained in the second manganese extraction step to perform a second manganese stripping step, yielding an aqueous manganese sulfate solution containing valuable metals at the concentrations shown in Table 3. The manganese sulfate was highly pure with a reduced calcium content.

[0057]

[0058] 50 L of 1 mol / L bis(2,4,4-trimethylpentyl)phosphinic acid diluted with MC531 manufactured by Tobu Chemical Co., Ltd. was added to 5 L of the liquid shown in Table 2, and sodium hydroxide was added to adjust the pH to 5.0 to perform a second manganese extraction (second manganese extraction step), yielding 50 L of extract. 5 L of 3 mol / L sulfuric acid was added to the 50 L of extract obtained in the second manganese extraction step to perform a second manganese stripping step, yielding an aqueous manganese sulfate solution containing valuable metals at the concentrations shown in Table 4. The manganese sulfate was highly pure with a reduced calcium content.

[0059]

[0060] 1: active material powder, 2A to 2C: valuable metal sulfate, 2a: extract obtained in first manganese extraction step, 2b: extract obtained in second manganese extraction step, 3a: calcium-containing liquid, 3: lithium hydroxide aqueous solution, 4: mineral acid, 5: lithium hydroxide monohydrate, 6: lithium carbonate, 11: electrolytic cell, 12: anode plate, 13: cathode plate, 14: anode, 15: cathode, 16: ion exchange membrane, 17: anode chamber, 18: cathode chamber.

Claims

1. A method for separating manganese from a liquid containing manganese and calcium, comprising: a first manganese extraction step of adding a first acidic organophosphorus compound to a liquid containing manganese and calcium to extract manganese and calcium; a first manganese stripping step of strip-extracting manganese and calcium from the extract obtained in the first manganese extraction step; a second manganese extraction step of adding a second acidic organophosphorus compound to the manganese-containing liquid obtained in the first manganese stripping step to extract manganese; and a second manganese stripping step of strip-extracting manganese from the extract obtained in the second manganese extraction step.

2. A method for separating manganese according to claim 1, further comprising: a dissolving step of dissolving active material powder obtained by pretreating waste lithium-ion batteries in a mineral acid to obtain an acid solution; a neutralization step of neutralizing the acid solution with an alkali; a cobalt extraction step of extracting cobalt from the extraction residue obtained in the first manganese extraction step using a first organic solvent as an extractant; a nickel extraction step of extracting nickel from the extraction residue of the cobalt extraction step using a second organic solvent as an extractant to obtain a first lithium salt aqueous solution as an extractant; and a membrane electrolysis step of subjecting the first lithium salt aqueous solution to membrane electrolysis using an ion exchange membrane to obtain a lithium hydroxide aqueous solution, an acid, and a second lithium salt aqueous solution that is more dilute than the first lithium salt aqueous solution, and reusing the lithium hydroxide aqueous solution obtained in the membrane electrolysis step in at least one step selected from the group consisting of the neutralization step, the first manganese extraction step, the second manganese extraction step, the cobalt extraction step, and the nickel extraction step, A method for separating manganese, wherein the acid obtained in the membrane electrolysis step is reused as the mineral acid used in the dissolution step.

3. The method for separating manganese as recited in claim 1, wherein the first acidic organophosphorus compound comprises 2-ethylhexylphosphonic acid mono 2-ethylhexyl ester, and the second acidic organophosphorus compound comprises bis(2,4,4-trimethylpentyl)phosphinic acid.

4. The method for separating manganese according to claim 1, wherein the first manganese extraction step is carried out at a pH in the range of 1.0 to 3.0, and the second manganese extraction step is carried out at a pH in the range of 2.5 to 5.

0.

5. A method for separating manganese as described in claim 2, wherein the mineral acid comprises at least one selected from the group consisting of hydrochloric acid, sulfuric acid, and nitric acid.

6. A method for separating manganese as recited in claim 5, wherein said mineral acid comprises hydrochloric acid.

7. A method for separating manganese as described in claim 1, wherein an alkali containing sodium hydroxide is added to the extraction residue obtained in the second manganese extraction step.

8. A method for separating manganese according to any one of claims 2 to 7, wherein the electricity used in the membrane electrolysis step includes electricity obtained from renewable energy.

9. A method for separating manganese according to claim 8, wherein the electricity obtained by renewable energy includes electricity obtained by at least one selected from the group consisting of solar power generation, wind power generation, geothermal power generation, hydroelectric power generation, and biomass power generation.

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