Method for separating lithium ions and apparatus for separating lithium ions

Abstract

By separating water containing lithium ions and divalent cations through nanofiltration membrane treatment, lithium ions and divalent cations are separated highly efficiently. [Solution] A method for separating lithium ions, comprising a membrane separation step of a water to be treated containing lithium ions and divalent cations by nanofiltration membrane separation treatment to permeate lithium ions into membrane-permeated water and concentrate divalent cations into membrane-concentrated water, characterized in that the nanofiltration membrane has the following separation performance. <Separation performance of nanofiltration membranes> The magnesium ion removal rate R when passing a magnesium chloride aqueous solution with a magnesium equivalent concentration of 500 mg / L through water at any pH between pH 4 and 9. Mg (%) and the sodium ion removal rate R when passing a sodium chloride aqueous solution with a Na equivalent concentration of 500 mg / L through water. Na (%) Difference (R Mg -R Na ) is 20% or more.

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for selectively separating lithium ions in wastewater or lithium ion-extracted water in which lithium ions and divalent cations coexist. [Background technology]

[0002] Lithium-ion batteries are lighter, have higher capacity, and generate higher electromotive force compared to conventional lead-acid and nickel-cadmium batteries, and are widely used in personal computers, electric vehicles, and portable devices. In particular, in recent years, with the global progress toward the SDGs (Sustainable Development Goals), the use of lithium-ion batteries in electric vehicles (EVs) has attracted attention.

[0003] Thus, while the use of lithium-ion batteries is expected to expand further in the future, from the perspective of securing mineral resources, it is desirable to recover valuable materials such as lithium from lithium-ion batteries that are discarded due to defects generated during the manufacturing process or due to the lifespan of the equipment and batteries used.

[0004] Conventionally, a method for recovering lithium from lithium-ion battery waste has been proposed, which includes an acid leaching step in which lithium-containing metals in the lithium-ion battery waste are leached with acid to obtain a metal-containing solution, and an extraction step in which the metals are separated from the metal-containing solution by solvent extraction (Patent Document 1).

[0005] Conventionally, membrane separation treatment has been considered a promising method for separating and recovering lithium ions from lithium-ion-containing water. As a method for separating and recovering lithium ions by membrane separation treatment, a method has been proposed in which monovalent lithium and divalent cations such as cobalt and nickel are separated using a nanofiltration membrane from a solution obtained by extracting with acid the calcined residue obtained by calcining used lithium-ion batteries and waste materials generated in the lithium-ion battery manufacturing process (Patent Document 2). Patent Document 2 describes the performance of the nanofiltration membrane to be used as follows: "When a 2000 mg / L aqueous solution of magnesium sulfate and a 2000 mg / L aqueous solution of magnesium chloride are passed through at an operating pressure of 0.5 MPa at 25°C and pH 6.5, the difference between the removal rate of magnesium sulfate and the removal rate of magnesium chloride ions is 20 percentage points or less, and when a 1000 mg / L aqueous solution of glucose and a 1000 mg / L aqueous solution of isopropyl alcohol are passed through at an operating pressure of 0.5 MPa at 25°C and pH 6.5, the difference between the removal rate of glucose and the removal rate of isopropyl alcohol is 40 percentage points or more, and it is preferable that the glucose removal rate is 70% or more." [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Patent No. 7100211 [Patent Document 2] Patent No. 7375953 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Patent Document 1 does not clearly define the separation conditions for monovalent and divalent cations, resulting in insufficient separation of lithium ions and divalent cations. Therefore, multi-stage nanofiltration membrane treatment was necessary to concentrate and sufficiently remove the divalent cations on the concentrated water side. On the other hand, since some lithium ions are also concentrated on the concentrated water side along with the divalent cations, there was a problem in that increasing the removal rate of divalent cations in the multi-stage system as a whole reduced the recovery rate of lithium ions.

[0008] The present invention aims to solve the problems of the above-mentioned prior art and to provide a lithium ion separation method and apparatus that can highly and efficiently separate lithium ions and divalent cations by separating treated water containing lithium ions and divalent cations through a nanofiltration membrane. [Means for solving the problem]

[0009] As a result of intensive studies to solve the above problems, the present inventors have found that the above problems can be solved by using a nanofiltration membrane having specific separation performance as the nanofiltration membrane used for the membrane separation treatment. That is, the gist of the present invention is as follows.

[0010] [1] In a method for separating lithium ions, which includes a membrane separation step of subjecting water to be treated containing lithium ions and divalent cations to nanofiltration membrane separation treatment to permeate the lithium ions into the permeated water through the membrane and concentrate the divalent cations in the concentrated water through the membrane, a method for separating lithium ions, characterized in that a nanofiltration membrane having the following separation performance is used as the nanofiltration membrane. <Separation performance of the nanofiltration membrane> At any pH of 4 to 9, the removal rate R of magnesium ions when passing a magnesium chloride aqueous solution with a magnesium equivalent concentration of 500 mg / L

[0011] ,

[0013] , , , , , ,

[0012] (%) and the removal rate R of sodium ions when passing a sodium chloride aqueous solution with a sodium equivalent concentration of 500 mg / L Na (%), and the difference (R Mg -R Na ) is 20% or more.

[0011] [2] The method for separating lithium ions according to [1], wherein the water to be treated is an aqueous solution adjusted in pH obtained through an acid treatment step of bringing a heat-treated product of a used lithium ion battery and scraps generated in the manufacturing process of a lithium ion battery into contact with a monovalent mineral acid aqueous solution to obtain an acidic aqueous solution containing lithium ions and divalent cations, and a pH adjustment step of adding an alkali to the acidic aqueous solution to obtain an aqueous solution adjusted in pH.

[0012] [3] The method for separating lithium ions according to [2], wherein the monovalent mineral acid aqueous solution used in the acid treatment step is a hydrochloric acid aqueous solution or a nitric acid aqueous solution.

[0013] [4] The method for separating lithium ions according to [2] or [3], wherein the alkali used in the pH adjustment step is calcium hydroxide or magnesium hydroxide, and the pH adjustment aqueous solution is adjusted to a pH of 4 to 9.

[0014] [5] The nanofiltration membrane has a magnesium ion removal rate R when an aqueous solution containing magnesium chloride and sodium chloride, containing magnesium chloride at a concentration of 500 mg / L (Mg equivalent) and sodium chloride at a concentration of 500 mg / L (Na equivalent), is passed through it at any pH in the range of pH 4 to 9. Mg (%) is 90% or more, and the sodium ion removal rate R Na A method for separating lithium ions as described in any of [1] to [4], wherein the (%) is 20% or less.

[0015] [6] The method for separating lithium ions according to any one of [1] to [5], wherein the water to be treated contains 50 to 50,000 mg / L of lithium and a total of 50 to 150,000 mg / L of at least one divalent cation from nickel, cobalt, and manganese as a divalent cation.

[0016] [7] A method for separating lithium ions according to any one of [1] to [6], further comprising an adsorption step of adsorbing and removing divalent cations in the membrane permeate.

[0017] [8] The method for separating lithium ions according to [6], wherein a strongly acidic cation exchange resin is used in the adsorption step.

[0018] [9] A lithium ion separation apparatus comprising a membrane separation means for separating water to be treated containing lithium ions and divalent cations through a nanofiltration membrane to permeate lithium ions into membrane-permeated water and concentrate divalent cations into membrane-concentrated water, A lithium ion separation apparatus characterized by using a nanofiltration membrane having the following separation performance as the nanofiltration membrane. <Separation performance of nanofiltration membranes> Removal rate R of magnesium ions when passing through an aqueous magnesium chloride solution with a magnesium equivalent concentration of 500 mg / L at any pH from pH 4 to 9 Mg (%), and the removal rate R of sodium ions when passing through an aqueous sodium chloride solution with a sodium equivalent concentration of 500 mg / L Na (%), and the difference (R Mg -R Na ) is 20% or more.

[0019]

[10] Acid treatment means for obtaining an acidic aqueous solution containing lithium ions and divalent cations by contacting a heat-treated product of used lithium-ion batteries and waste materials generated in the manufacturing process of lithium-ion batteries with a monovalent mineral acid aqueous solution, and pH adjustment means for obtaining a pH-adjusted aqueous solution by adding an alkali to the acidic aqueous solution, and the pH-adjusted aqueous solution is introduced into the membrane separation means as the water to be treated, the lithium-ion separation device according to [9].

[0020]

[11] The lithium-ion separation device according to

[10] , wherein in the acid treatment means, a hydrochloric acid aqueous solution or a nitric acid aqueous solution is used as the monovalent mineral acid aqueous solution.

[0021]

[12] The lithium-ion separation device according to

[10] or

[11] , wherein in the pH adjustment means, calcium hydroxide or magnesium hydroxide is used as the alkali, and the pH of the pH-adjusted aqueous solution is adjusted to pH 4 to 9.

[0022]

[13] The nanofiltration membrane has a removal rate R of magnesium ions of 90% or more when passing through an aqueous solution containing magnesium chloride and sodium chloride containing magnesium chloride with a magnesium equivalent concentration of 500 mg / L and sodium chloride with a sodium equivalent concentration of 500 mg / L at any pH in the range of pH 4 to 9 Mg (%), and the removal rate R of sodium ions Na (%) is 20% or less, the lithium-ion separation device according to any one of [9] to

[12] .

[0023]

[14] A lithium ion separation apparatus according to any one of [9] to

[13] , wherein the water to be treated contains 50 to 50,000 mg / L of lithium ions and a total of 50 to 150,000 mg / L of at least one divalent cation from nickel, cobalt, and manganese as a divalent cation.

[0024]

[15] A lithium ion separation apparatus according to any one of [9] to

[14] , further comprising an adsorption means for adsorbing and removing divalent cations in the membrane permeate.

[0025]

[16] The lithium ion separation apparatus according to

[15] , wherein the adsorption means comprises a strongly acidic cation exchange resin. [Effects of the Invention]

[0026] According to the lithium ion separation method and apparatus of the present invention, by separating water to be treated containing lithium ions and divalent cations using a nanofiltration membrane, the divalent cations can be concentrated on the membrane-concentrated water side and lithium ions can be permeated to the membrane-permeated water side in a single membrane separation process, without the need for multi-stage membrane separation using nanofiltration membranes. This allows for highly efficient separation of lithium ions and divalent cations. However, the present invention does not preclude multi-stage membrane separation using nanofiltration membranes, and other membrane separation processes can be combined with this method. This invention is particularly useful for separating and recovering lithium ions from a pH-adjusted aqueous solution obtained by immersing used lithium-ion batteries and heat-treated waste materials generated in the manufacturing process of lithium-ion batteries in a monovalent mineral acid aqueous solution to obtain an acidic aqueous solution containing lithium ions and divalent cations, and then adjusting the pH of the resulting acidic aqueous solution by adding alkali. This allows for the recovery and effective utilization of valuable materials from waste materials, thereby promoting the SDGs. [Brief explanation of the drawing]

[0027] [Figure 1] This is a diagram showing the configuration of the flat membrane testing apparatus used in the examples and comparative examples. [Figure 2]This graph shows the experimental results of the separation of supply water I (NaCl: 500 mg / L (as Na), MgCl2: 500 mg / L (as mg)) using an NF membrane (PRO-XS2) in Experimental Example 1. [Figure 3] This graph shows the experimental results of the separation of supply water I (NaCl: 500 mg / L (as Na), MgCl2: 500 mg / L (as mg)) using an NF membrane (ESNALFLD) in Experimental Example 1. [Figure 4] This graph shows the experimental results of separating supply water I (NaCl: 500 mg / L (as Na), MgCl2: 500 mg / L (as mg)) using an NF membrane (HYDRACoRe10LD) in Experimental Example 1. [Figure 5] This graph shows the experimental results of separating supply water I (NaCl: 500 mg / L (as Na), MgCl2: 500 mg / L (as mg)) using an NF membrane (HYDRACoRe50LD) in Experimental Example 1. [Figure 6] This graph shows the experimental results of separating supply water II (Na2SO4: 500 mg / L (as Na), MgSO4: 500 mg / L (as Mg)) using an NF membrane (PRO-XS2) in Experimental Example 1. [Modes for carrying out the invention]

[0028] Embodiments of the present invention will be described in detail below.

[0029] [Method for separating lithium ions] The present invention relates to a lithium ion separation method that includes a membrane separation step of separating water to be treated containing lithium ions and divalent cations through a nanofiltration membrane (hereinafter sometimes referred to as "NF membrane") to permeate lithium ions into membrane-permeated water and concentrate divalent cations into membrane-concentrated water, characterized in that the nanofiltration membrane used has the following separation performance. <Separation performance of nanofiltration membranes> The magnesium ion removal rate R when passing a magnesium chloride aqueous solution with a magnesium equivalent concentration of 500 mg / L through water at any pH between pH 4 and 9.Mg (%) and the removal rate R of sodium ions when passing through an aqueous sodium chloride solution with a concentration of 500 mg / L in terms of Na Na (%), and the difference (R Mg -R Na ) is 20% or more.

[0030] <Mechanism> When the present inventors examined the separation characteristics of an NF membrane for treated water containing lithium ions and divalent cations, the following was found. (1) At pH 2 - 3, when the counter ion is sulfate ion, the removal rate of divalent cations is almost 100%. However, the removal rate of monovalent lithium ions is also 60% or more, and the separation efficiency of lithium ions and divalent cations is poor (Figure 6 shown later). Also, when the counter ion is chloride ion, the removal rate of divalent cations decreases, and divalent cations coexist with lithium ions on the permeate side. (2) At pH 4 - 9, when the counter ion is sulfate ion, the removal rate of divalent cations is high, but the removal rate of lithium ions is also 70% or more, and both are concentrated on the concentrate side. In contrast, when the counter ion is chloride ion, in a specific NF membrane, the removal rate of divalent cations is about 90%, and the removal rate of lithium ions is 10% or less, enabling efficient separation of lithium ions and divalent cations. That is, this condition is a condition that can effectively separate lithium ions and divalent cations. Depending on the NF membrane, even when using chloride ions, there are cases where the removal rate of lithium ions is 20% or more, resulting in a decrease in the separation and recovery rate of lithium ions, so it is not effective. Also, there are NF membranes with a removal rate of divalent cations of 20% or less, and such NF membranes are not effective for the present invention. For these reasons, in the present invention, the separation performance of the aforementioned NF membrane was defined.

[0031] <NF Membrane> The NF membrane used in the present invention satisfies the aforementioned separation performance. In this invention, the removal rate is the percentage of the amount (mass) of ions separated and concentrated from the NF membrane supply water to the NF membrane concentrated water side, and is calculated as follows. Magnesium ion removal rate R Mg (%) = {(Mg concentration of NF membrane supply water - Mg concentration of NF membrane permeate) / Mg concentration of NF membrane supply water} × 100 Sodium ion removal rate R Na (%) = {(Na concentration of NF membrane supply water - Na concentration of NF membrane permeate) / Na concentration of NF membrane supply water} × 100

[0032] There are no particular restrictions on the method for measuring each ion in water, but magnesium ion concentration is measured, for example, by ion chromatography or ICP emission spectrometry. The same applies to nickel ions, cobalt ions, manganese ions, and calcium ions in the examples described later. Lithium ions in water can be measured, for example, by ion chromatography or ICP emission spectrometry.

[0033] In the specification of the separation performance of the above NF membrane, R Mg -R Na The pH range satisfying 20% ​​or more can be any pH value between pH 4 and 9. This pH value can be within the pH range used for lithium ion separation, but preferably between pH 6 and 8, more preferably between pH 5 and 9, and particularly preferably the entire range between pH 4 and 9. Mg -R Na Achieving a level of 20% or more is preferable, as it allows for more stable acquisition of the effects of the present invention.

[0034] Also, from a similar perspective, R Mg -R Na It is 20% or more, preferably 40% or more, more preferably 50% or more, and particularly preferably 60% or more. Mg -R Na There is no particular upper limit, but it is usually 90% or less.

[0035] In the aforementioned specification for the separation performance of the NF membrane, the removal rates R when magnesium chloride (MgCl2) aqueous solution and sodium chloride (NaCl) aqueous solution are passed through the membrane are specified. Mg , R Na This specifies the removal rate R Mg , R Na This refers to the removal rate R when an aqueous solution containing magnesium chloride and sodium chloride, with a magnesium equivalent concentration of 500 mg / L and a sodium equivalent concentration of 500 mg / L, is passed through water. Mg , R Na This is equivalent to the R when an aqueous solution of MgCl2 and NaCl containing MgCl2 with a Mg equivalent concentration of 500 mg / L and NaCl with a Na equivalent concentration of 500 mg / L is passed through it. Mg -R Na It is preferable that the above upper limit is met. Also, the magnesium ion removal rate R at this time Mg The removal rate of sodium ions is 80% or more, especially 90% or more. Na It is preferable that it is 30% or less, and particularly 20% or less. Mg There is no particular upper limit, but it is usually 95% or less. Na There is no specific lower limit, but it is usually 5% or higher.

[0036] Based on the above, in the present invention, an NF membrane that satisfies the above separation performance is selected from commercially available products and used as the NF membrane, or the separation performance is improved by treating the RO membrane with an oxidation treatment, or an NF membrane is prepared by the method described in Japanese Patent Publication No. 7491040 and used for lithium ion separation.

[0037] <Water to be treated> In this invention, the water to be treated for lithium ion separation contains lithium ions and divalent cations. The treated water in the present invention is not particularly limited as long as it contains lithium ions and divalent cations, but examples of its water quality include water containing 50 to 50,000 mg / L of lithium, preferably 200 to 40,000 mg / L, more preferably 500 to 35,000 mg / L, and containing at least one divalent cation from nickel, cobalt, and manganese in a total of 50 to 150,000 mg / L, preferably 200 to 120,000 mg / L, more preferably 500 to 100,000 mg / L, and containing 50 to 50,000 mg / L each of nickel, cobalt, and manganese, preferably 200 to 40,000 mg / L, more preferably 500 to 35,000 mg / L.

[0038] As mentioned above, in light of the recent demand for the separation and recovery of lithium ions from lithium-ion battery waste, it is preferable that the water to be treated in this invention be an extract obtained by acid extraction of used lithium-ion batteries and heat-treated waste materials (hereinafter sometimes referred to as "black mass, etc.") generated in the lithium-ion battery manufacturing process. In other words, the water to be treated in the present invention is preferably a pH-adjusted aqueous solution obtained through an acid treatment step in which black mas or the like is brought into contact with a monovalent mineral acid aqueous solution to obtain an acidic aqueous solution containing lithium ions and divalent cations, and a pH adjustment step in which alkali is added to the acidic aqueous solution to obtain a pH-adjusted aqueous solution.

[0039] As the monovalent mineral acid aqueous solution used in the above acid treatment process, a hydrochloric acid aqueous solution or nitric acid aqueous solution with a pH of 0 to 3 can be used. Immersion treatment is a simple method for bringing black trout and other similar organisms into contact with such mineral acid solutions. The acidic aqueous solution obtained in this acid treatment process typically has a pH of 0-3, a lithium ion concentration of 500-50,000 mg / L, a nickel ion concentration of 500-50,000 mg / L, a cobalt ion concentration of 500-50,000 mg / L, and a manganese ion concentration of 50-50,000 mg / L.

[0040] As the alkali used for adjusting the pH of the obtained acidic aqueous solution, when using a monovalent alkali (alkali metal hydroxide) such as sodium hydroxide, the recovery efficiency of lithium ions decreases due to the coexistence of monovalent cations other than lithium ions. Therefore, it is preferable to use a divalent alkali (alkaline earth metal hydroxide), and it is preferable to use calcium hydroxide or magnesium hydroxide. In this pH adjustment step, by adding such an alkali, the pH is adjusted to pH 4 to 9, preferably pH 5 to 9.

[0041] In the present invention, the pH-adjusted aqueous solution thus obtained is used as the treated water for NF membrane separation.

[0042] As described above, when using the pH-adjusted aqueous solution obtained by acid-treating black mass or the like and then adjusting the pH as the treated water, the treated water contains, together with lithium ions, at least one divalent cation of nickel, cobalt, and manganese as a divalent cation. Generally, it is treated water with a pH of 4 to 9, preferably 5 to 9, a lithium ion concentration of 500 to 50,000 mg / L, a nickel ion concentration of 500 to 50,000 mg / L, a cobalt ion concentration of 500 to 50,000 mg / L, and a manganese ion concentration of 50 to 50,000 mg / L.

[0043] <NF Membrane Separation Treatment> The NF membrane separation treatment of the treated water is not particularly limited except for using an NF membrane that satisfies the above-described separation performance. For example, it is preferable to adopt the following conditions. pH: 4 to 9, preferably 5 to 9 Water temperature: 10 to 30 °C Flux: 0.3 to 3 m / day (25 °C)

[0044] <Ion Exchange Resin Treatment> In the present invention, the above NF membrane separation treatment allows lithium ions in the water to be treated to permeate into the NF membrane permeate and concentrate, and divalent cations to concentrate on the NF membrane concentrated water side, thereby effectively separating lithium ions. However, a small amount of divalent cations usually remains in the obtained NF membrane permeate. To further remove the divalent cations in the NF membrane permeate, the NF membrane permeate may be treated with an ion exchange resin to adsorb and remove the divalent cations. A strongly acidic cation exchange resin is preferred as the ion exchange resin used here. By using a strongly acidic cation exchange resin, divalent cations can be adsorbed and removed without significantly reducing the lithium ions in the NF membrane permeate, thereby obtaining treated water with a higher lithium ion concentration. Furthermore, as shown in Reference Example 1 below, when a weakly acidic cation exchange resin is used as the ion exchange resin, neither lithium ions nor divalent cations can be removed. Therefore, it is preferable to use a strongly acidic cation exchange resin, particularly an H-type strongly acidic cation exchange resin, as the ion exchange resin.

[0045] Although not particularly limited, according to the present invention, water of the following quality can be recovered from treated water of the following quality, which is an acid-treated or pH-adjusted aqueous solution of black mas, etc., as described above. (Water to be treated) Li: 1266 mg / L Ni: 2292 mg / L Co: 2335 mg / L Mn: 484 mg / L Ca: 174 mg / L (when pH is adjusted with calcium hydroxide) (NF membrane permeated water) Li: 1209 mg / L Ni: 71 mg / L Co: 95 mg / L Mn: 30 mg / L Ca: 13 mg / L (Ion exchange resin treated water) Li: 1141 mg / L Ni: 21 mg / L Co: 28 mg / L Mn: 8 mg / L Ca: 2.9 mg / L

[0046] [Lithium ion separation device] The lithium ion separation apparatus of the present invention includes a membrane separation means for separating water to be treated containing lithium ions and divalent cations through a nanofiltration membrane to permeate lithium ions into membrane-permeated water and concentrate divalent cations into membrane-concentrated water, characterized in that the nanofiltration membrane is a nanofiltration membrane having the aforementioned specific separation performance.

[0047] Preferably, the lithium ion separation apparatus of the present invention comprises an acid treatment means for obtaining an acidic aqueous solution containing lithium ions and divalent cations by contacting the aforementioned black mass, etc., with a monovalent mineral acid aqueous solution, such as by immersion; a pH adjustment means for obtaining a pH-adjusted aqueous solution by adding alkali to the acidic aqueous solution; and an NF membrane separation means for performing NF membrane separation treatment using the aforementioned NF membrane having specific separation performance as the water to be treated. Here, there are no particular restrictions on the means for NF membrane separation, acid treatment, and pH adjustment, and conventionally known general NF membrane separation apparatuses, immersion / solid-liquid separation apparatuses, pH adjustment tanks, etc., can be used. [Examples]

[0048] The present invention will be described in more detail below with reference to experimental examples, examples, and reference examples.

[0049] [NF film experimental setup] In the following experimental examples and embodiments, the performance of each NF film was evaluated using the flat film testing apparatus shown in Figure 1. In this test apparatus, the NF membrane feed water is supplied from pipe 11 by high-pressure pump 4 to the raw water chamber 1A below the flat membrane cell 2 equipped with the NF membrane in the sealed container 1. As shown in Fig. 1(b), the sealed container 1 is composed of a lower case 1a on the raw water chamber 1A side and an upper case 1b on the permeate water chamber 1B side. Between the lower case 1a and the upper case 1b, the flat membrane cell 2 is fixed via an O-ring 8. The flat membrane cell 2 is configured such that the permeate water side of the NF membrane 2A is supported by a porous support plate 2B. The inside of the raw water chamber 1A below the flat membrane cell 2 is stirred by rotating a stirrer 5 with a stirrer 3. The NF membrane permeate water is taken out from pipe 12 through the permeate water chamber 1B above the flat membrane cell 2. The concentrated water is taken out from pipe 13. The pressure inside the sealed container 1 is adjusted by a pressure gauge 6 provided in the feed water pipe 11 and a pressure regulating valve 7 provided in the concentrated water extraction pipe 13. The analysis methods for each ion in the following experimental examples, examples, and reference examples are as described above.

[0050] [Experimental Example 1: Performance Evaluation Experiment of NF Membrane] An experiment was conducted to evaluate the performance of the NF membrane under the following experimental conditions using the following NF membranes.

[0051] <NF Membrane> Four types from Nitto Denko Corporation: "PRO-XS2", "ESNALFLD", "HYDRACoRe10LD", "HYDRACoRe50LD"

[0052] <Experimental Conditions> Feed water I: An aqueous solution of NaCl: 500 mg / L (as Na), MgCl2: 500 mg / L (as Mg) Feed water II: An aqueous solution of Na2SO4: 500 mg / L (as Na), MgSO4: 500 mg / L (as Mg) pH: 2 - 9 (adjusted with HCl (for feed water I) or H2SO4 (for feed water II) and NaOH) Water temperature: 20 - 25 °C Feed water flow rate: 2.0 mL / min Operating pressure: 0.9 - 1.0 MPa Flux: 1.0 - 1.2 m / day (25 °C)

[0053] <Results and Discussion> Figs. 2 to 5 show the experimental results of the NF membranes for Feed Water I (NaCl: 500 mg / L (as Na), MgCl2: 500 mg / L (as Mg)) at pH 2 to 9 and Flux of 1.0 to 1.2 m / day (25°C). In the case of PRO-XS2, at pH 5 to 7, the removal rate of sodium ions is 20% or less, and the removal rate of magnesium ions is about 90%. In contrast, for ESNALFLD, the removal rates of sodium and magnesium ions are 70% or more. Also, for HYDRACoRe10LD and HYDRACoRe50LD, the removal rates of both sodium and magnesium ions are about 20%. Therefore, it can be said that PRO-XS2 is suitable for separating monovalent lithium ions and divalent cations.

[0054] Fig. 6 shows the experimental results of the NF membranes for Feed Water II (Na2SO4: 500 mg / L (as Na), MgSO4: 500 mg / L (as Mg)) at pH 2 to 9 and Flux of 1.0 to 1.2 m / day (25°C). Even when using PRO-XS2 and the counter ion is sulfate ion, the removal rates of sodium and magnesium ions are 90% or more, indicating that it is not suitable for separating monovalent lithium ions and divalent cations.

[0055] [Example 1] Using the flat membrane experimental device shown in Fig. 1, membrane separation of lithium ions and divalent cations was performed on the following NF membranes under the following experimental conditions. The following feed water was adjusted to the ion ratio as the composition of the black mass treatment liquid based on the above-mentioned Patent Document 1.

[0056] <NF Membrane> NF Membrane: "PRO-XS2" manufactured by Nitto Denko Corporation

[0057] <Experimental Conditions> Supply water: LiCl: 1500mg / L (asLi), NiCl2: 2500mg / L (asNi), CoCl2: 2500mg / L (asCo), MnCl2: 500mg / L (asMn) pH: 5 (Adjusted to pH 2 with HCl, then adjusted with Ca(OH)2) Water temperature: 22℃ Supply water amount: 2.0mL / min Operating pressure: 1.3~1.4MPa Flux: 0.5 m / day (25℃)

[0058] <Results / Discussion> Table 1 below shows the concentrations and removal rates of each ion in the supply water and NF membrane permeate. The removal rate for lithium ions was 4.5%, while the removal rate for divalent cations was over 90% for both. This indicates that lithium ions were effectively separated.

[0059] [Table 1]

[0060] [Example 2] The separation was performed in the same manner as in Example 1, except that the feedwater was adjusted to pH 2 with HCl and then to pH 5 with NaOH.

[0061] <Results / Discussion> Table 2 shows the concentrations and removal rates of each ion in the supply water and NF membrane permeate. The removal rate for lithium ions was 0.1%, while the removal rate for divalent cations was over 90%. However, the removal rate for sodium ions was 3.7%, indicating that approximately 15% of sodium ions were present in the NF membrane permeate relative to lithium ions.

[0062] [Table 2]

[0063] [Example 3] The NF membrane permeate water obtained in Example 1 was immersed with the following ion exchange resins under the experimental conditions described below, and then solid-liquid separation was performed to obtain ion exchange resin-treated water.

[0064] <Ion exchange resin> Strong acid cation exchange resin: Kurita Water Industries Ltd. "KR-UC-1"

[0065] <Experimental conditions> Water temperature: 20~25℃ Volume: 50 mL Resin amount: 300mg Soaking time: 72h Stirring speed: 150rpm

[0066] <Results / Discussion> Table 3 below shows the concentrations and removal rates of each ion in NF membrane permeate water and ion exchange resin treated water. The lithium ion removal rate was 5.6%, while the divalent cation removal rate was over 70% for all types. This indicates that lithium ions were effectively separated.

[0067] [Table 3]

[0068] [Example 4] Ion-exchange resin treated water was obtained in the same manner as in Example 3, except that the amount of ion-exchange resin was set to 150 mg.

[0069] <Results / Discussion> Table 4 below shows the concentrations and removal rates of each ion in NF membrane permeate water and ion exchange resin treated water. The lithium ion removal rate was 3.2%, and the divalent cation removal rate was over 30% for both. This indicates that lithium ions were effectively separated.

[0070] [Table 4]

[0071] [Example 5] Ion-exchange resin treated water was obtained in the same manner as in Example 3, except that the amount of ion-exchange resin was set to 600 mg.

[0072] <Results / Discussion> Table 5 below shows the concentrations and removal rates of each ion in the NF membrane permeate water and the ion exchange resin treated water. The lithium ion removal rate was 10.8%, and the divalent cation removal rate was over 80% for both. This indicates that lithium ions were effectively separated.

[0073] [Table 5]

[0074] Furthermore, the results from Examples 3 to 5 show that in order to obtain the desired lithium ion separation efficiency, it is necessary to adjust the amount of ion exchange resin to a suitable ratio to the liquid volume.

[0075] [Reference example 1] Ion-exchange resin treated water was obtained in the same manner as in Example 3, except that a weakly acidic cation exchange resin (Purolite's "C104Plus") was used instead of a strongly acidic cation exchange resin as the ion exchange resin.

[0076] <Results / Discussion> Table 6 below shows the concentrations and removal rates of each ion in NF membrane permeate water and ion exchange resin treated water. Since none of the ions were removed, it is clear that a strongly acidic cation exchange resin is needed for further separation of lithium ions from NF membrane permeate, rather than a weakly acidic cation exchange resin.

[0077] [Table 6] [Explanation of Symbols]

[0078] 1 container 2 Flat membrane cells 2A NF membrane 2B Porous support plate 3 Stirrers 4. High-pressure pump 5 Stirring bar 6. Pressure gauge 7. Pressure regulating valve 8 O-rings

Claims

1. A method for separating lithium ions, which includes a membrane separation step in which water to be treated containing lithium ions and divalent cations is separated by a nanofiltration membrane to allow lithium ions to permeate into membrane-permeated water and divalent cations to be concentrated into membrane-concentrated water, A method for separating lithium ions, characterized in that the nanofiltration membrane having the following separation performance is used as the nanofiltration membrane. <Separation performance of nanofiltration membranes> The magnesium ion removal rate R when an aqueous magnesium chloride solution with a magnesium equivalent concentration of 500 mg / L is passed through water at a pH of any of the pH 4 to 9. Ｍｇ (%) and the sodium ion removal rate R when passing a sodium chloride aqueous solution with a Na equivalent concentration of 500 mg / L through water. Ｎａ (R) Ｍｇ -R Ｎａ ) is 20% or more.

2. The lithium ion separation method according to claim 1, wherein the water to be treated is a pH-adjusted aqueous solution obtained through an acid treatment step in which a used lithium-ion battery and a heat-treated waste material generated in the manufacturing process of lithium-ion batteries are brought into contact with a monovalent mineral acid aqueous solution to obtain an acidic aqueous solution containing lithium ions and divalent cations, and a pH adjustment step in which an alkali is added to the acidic aqueous solution to obtain a pH-adjusted aqueous solution.

3. The lithium ion separation method according to claim 2, wherein the monovalent mineral acid aqueous solution used in the acid treatment step is a hydrochloric acid aqueous solution or a nitric acid aqueous solution.

4. The method for separating lithium ions according to claim 2, wherein the alkali used in the pH adjustment step is calcium hydroxide or magnesium hydroxide, and the pH of the pH-adjusted aqueous solution is adjusted to a pH of 4 to 9.

5. The nanofiltration membrane has a magnesium ion removal rate R when an aqueous solution containing magnesium chloride and sodium chloride, with a magnesium equivalent concentration of 500 mg / L and a sodium equivalent concentration of 500 mg / L, is passed through it at any pH in the range of pH 4 to 9. Ｍｇ (%) is 90% or more, and the sodium ion removal rate R Ｎａ The method for separating lithium ions according to claim 1, wherein the (%) is 20% or less.

6. The method for separating lithium ions according to claim 1, wherein the treated water contains 50 to 50,000 mg / L of lithium and a total of 50 to 150,000 mg / L of at least one divalent cation from nickel, cobalt, and manganese as a divalent cation.

7. Furthermore, the lithium ion separation method according to any one of claims 1 to 6, further comprising an adsorption step of adsorbing and removing divalent cations in the membrane permeate.

8. The method for separating lithium ions according to claim 6, wherein a strongly acidic cation exchange resin is used in the adsorption step.

9. A lithium ion separation apparatus comprising a membrane separation means for separating water to be treated containing lithium ions and divalent cations through a nanofiltration membrane to permeate lithium ions into membrane-permeated water and concentrate divalent cations into membrane-concentrated water, A lithium ion separation apparatus characterized by using a nanofiltration membrane having the following separation performance as the nanofiltration membrane. <Separation performance of nanofiltration membranes> Removal rate R of magnesium ions when an aqueous magnesium chloride solution with a magnesium equivalent concentration of 500 mg / L is passed through at any pH from 4 to 9 Ｍｇ (%) and the removal rate R Ｎａ (%) of sodium ions when an aqueous sodium chloride solution with a sodium equivalent concentration of 500 mg / L is passed through, and the difference (R Ｍｇ −R Ｎａ ) is 20% or more.

10. A lithium ion separation apparatus according to claim 9, further comprising: an acid treatment means for contacting used lithium-ion batteries and heat-treated waste materials generated in the manufacturing process of lithium-ion batteries with a monovalent mineral acid aqueous solution to obtain an acidic aqueous solution containing lithium ions and divalent cations; and a pH adjustment means for adding alkali to the acidic aqueous solution to obtain a pH-adjusted aqueous solution, wherein the pH-adjusted aqueous solution is introduced into the membrane separation means as the water to be treated.

11. The lithium ion separation apparatus according to claim 10, wherein in the acid treatment means, an aqueous hydrochloric acid solution or an aqueous nitric acid solution is used as the monovalent mineral acid solution.

12. The lithium ion separation apparatus according to claim 10, wherein, in the pH adjusting means, calcium hydroxide or magnesium hydroxide is used as the alkali, and the pH adjusting aqueous solution is adjusted to a pH of 4 to 9.

13. The nanofiltration membrane has a magnesium ion removal rate R when an aqueous solution containing magnesium chloride and sodium chloride, with a magnesium equivalent concentration of 500 mg / L and a sodium equivalent concentration of 500 mg / L, is passed through it at any pH in the range of pH 4 to 9. Ｍｇ (%) is 90% or more, and the sodium ion removal rate R Ｎａ The lithium ion separation apparatus according to claim 9, wherein the (%) is 20% or less.

14. The lithium ion separation apparatus according to claim 9, wherein the water to be treated contains 50 to 50,000 mg / L of lithium ions and a total of 50 to 150,000 mg / L of at least one divalent cation from nickel, cobalt, and manganese as a divalent cation.

15. Furthermore, the lithium ion separation apparatus according to any one of claims 9 to 14, further comprising adsorption means for adsorbing and removing divalent cations in the membrane permeate.

16. The lithium ion separation apparatus according to claim 15, wherein the adsorption means includes a strongly acidic cation exchange resin.

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