JP2023055031A - Recovery method of salt containing metal species constituting polyvalent rare metal ion or simple substance - Google Patents

Abstract

To provide an efficiently recovering method of a polyvalent rare metal ion-derived salt or a rare metal simple substance from a lithium ion battery, a mobile phone, a rare earth magnet and a waste material, a waste liquid, an ore and the like produced in their production processes.SOLUTION: A method to recover a salt containing metal species constituting a polyvalent rare metal ion or a simple substance from a solution X containing the polyvalent rare metal ion includes a step to concentrate the polyvalent rare metal ion by a membrane. The membrane has an isopropyl alcohol removal ratio of 40% or more when permeating an isopropyl alcohol aqueous solution having a pH value of 6.5 at 25°C in an operation pressure of 0.5 MPa.SELECTED DRAWING: None

Description

The present invention is a method for concentrating a solution containing polyvalent rare metal ions with a membrane, and recovering salts containing metal species that constitute polyvalent rare metal ions or simple rare metals with high purity and high recovery rate. intended to provide

In recent years, the demand for rare metals has increased remarkably along with the economic development of the world. For example, cobalt is widely used in various industries as an alloying element for specialty steels and magnetic materials. For example, special steel is used in the fields of aerospace, generators, and special tools, and magnetic materials are used in small headphones, small motors, and the like. Cobalt is also used as a raw material for positive electrode materials in lithium ion batteries, and with the spread of mobile information processing terminals such as smartphones, and batteries for automobiles and power storage, the demand for cobalt is increasing. Also, nickel is used as stainless steel because of its high luster and corrosion resistance, and in recent years, like cobalt, the demand for nickel as a material for lithium-ion batteries is increasing.

As the demand for various rare metals increases, efforts are being made to recover metal ions such as lithium, cobalt, and nickel from used lithium-ion batteries and waste materials generated from their manufacturing processes from the perspective of recycling valuable resources. ing.
For example, a separation and recovery method using separation membranes such as ultrafiltration membranes, nanofiltration membranes, and reverse osmosis membranes from an aqueous solution obtained by leaching waste lithium ion batteries with acid has been proposed (Patent Document 1).

International Publication No. 2019/18333

However, since the conventional method is premised on the recovery of monovalent rare metal ions, a nanofiltration membrane that selectively separates monovalent rare metal ions from divalent rare metal ions is used as a separation membrane. Therefore, there is a problem that expensive polyvalent rare metal ions such as cobalt and nickel are lost with respect to monovalent rare metal ions such as lithium.

Therefore, the object of the present invention is to extract salts derived from polyvalent rare metal ions or rare metal simple substances from lithium ion batteries, mobile phones, rare earth magnets, and waste materials, waste liquids, ores, etc. generated in their manufacturing processes, with small loss. To provide a method for efficiently collecting.

In order to solve the above problems, the present invention takes any of the following configurations.
[1] A method for recovering, from a solution X containing polyvalent rare metal ions, a salt or simple substance containing metal species constituting polyvalent rare metal ions, wherein the polyvalent rare metal ions in the solution X are separated by the following membrane: A recovery method, comprising a step of concentrating.
(Membrane) A membrane having an isopropyl alcohol removal rate of 40% or more when an isopropyl alcohol aqueous solution having a pH of 6.5 at 25° C. and an operating pressure of 0.5 MPa is permeated.
[2] The solution X has a pH of 3 or less, and the isopropyl alcohol solution when the membrane is permeated with an isopropyl alcohol aqueous solution having the same pH as the solution X at 25° C. under an operating pressure of 0.5 MPa. The recovery method according to the above [1], characterized in that the removal rate is 40% or more.
[3] The membrane has an isopropyl alcohol removal rate of 70% or more when an isopropyl alcohol aqueous solution of pH 6.5 at 25° C. is permeated at an operating pressure of 0.5 MPa, and/or The recovery method according to the above [1] or [2], wherein the isopropyl alcohol removal rate is 70% or more when an isopropyl alcohol aqueous solution having a pH of 3 or less at 25° C. at an operating pressure is permeated.
[4] The solution X is characterized in that the ratio of the total concentration of monovalent rare metal ions (mg/L)/the total concentration of polyvalent rare metal ions (mg/L) is 0 or more and less than 100. The recovery method according to any one of [1] to [3].
[5] The polyvalent rare metal ions are cobalt ions, nickel ions, gold ions, palladium ions, platinum ions, neodymium ions, indium ions, dysprosium ions, lanthanum ions, yttrium ions, tantalum ions, niobium ions, tungsten ions, The recovery method according to any one of the above [1] to [4], wherein the molybdenum ion is at least one type of molybdenum ion.
[6] The recovery method according to any one of the above [1] to [5], characterized by including either of the following (a) or (b).
(a) a concentration step of obtaining a non-permeated liquid having a higher polyvalent rare metal ion concentration than the solution X and a permeated liquid having a lower polyvalent rare metal ion concentration than the solution X by the membrane; A separation step of obtaining a liquid having a high concentration of polyvalent rare metal ions to be recovered and a liquid having a low concentration of polyvalent rare metal ions to be recovered from the liquid is performed in this order.
(b) a separation step of obtaining a liquid having a high concentration of polyvalent rare metal ions to be recovered and a liquid having a low concentration of polyvalent rare metal ions to be recovered from the solution X by solvent extraction; to obtain a non-permeated liquid having a high concentration of polyvalent rare metal ions and a permeated liquid having a low concentration of polyvalent rare metal ions in this order.
[7] If the total metal ion concentration in the solution X is 50,000 mg/L or less, perform the above (a), and if the total metal ion concentration in the solution X is greater than 50,000 mg/L, perform the above (b) The recovery method according to [6].
[8] The membrane contains a crosslinked aromatic polyamide, and the crosslinked aromatic polyamide has at least one structure represented by the following formula (1) or (2): [1] to The recovery method according to any one of [7].

(Ar ₁ to Ar ₃ are each independently an optionally substituted aromatic ring having 5 to 14 carbon atoms, and R ₁ is an atom having neither an aromatic ring nor a hetero atom group, X is a hydrogen atom or a carboxy group, and R ₂ to R ₅ are each independently a hydrogen atom or an aliphatic chain having 1 to 10 carbon atoms.)

According to the present invention, salts derived from polyvalent rare metal ions and simple rare metals can be efficiently recovered by treating a polyvalent rare metal ion-containing solution with a membrane that satisfies specific conditions. In particular, when a concentration step of treating with a membrane that satisfies specific conditions and a separation step by solvent extraction are used in combination, and these steps are performed together in an appropriate order, salts derived from polyvalent rare metal ions and simple rare metals can be added. Efficient recovery is possible.

[1] Solution X for use in the present invention
The solution X used in the present invention is a solution containing at least polyvalent rare metal ions, and may not contain monovalent rare metal ions.

(1) Monovalent Rare Metal Ions Specific examples of monovalent rare metal ions include ions of lithium, cesium, and rubidium.

(2) Polyvalent rare metal ions Examples of polyvalent rare metal ions include beryllium, boron, scandium, titanium, vanadium, chromium, manganese, cobalt, nickel, gallium, germanium, selenium, strontium, yttrium, zirconium, niobium, Ions of molybdenum, palladium, indium, antimony, tellurium, vanadium, hafnium, tantalum, tungsten, rhenium, platinum, thallium, bismuth, and lanthanide metals are included. Lanthanides are 15 elements with atomic numbers from 57 to 71, and refer to lanthanum, cerium, plutonium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, hofnium, erbium, thulium, ytterbium, and lutetium.

(3) Solution Containing Polyvalent Rare Metal Ions The solution containing polyvalent rare metal ions contains at least one of the polyvalent rare metal ions described above. Specifically, due to the high demand for reuse and the high purity of the rare metals contained, lithium ion batteries, mobile phones, rare earth magnets, and waste materials, waste liquids, ores, and slag generated in their manufacturing processes, etc. A solution containing polyvalent rare metal ions derived from rare metals contained in is preferable, and further cobalt ions, nickel ions, gold ions, palladium ions, platinum ions, neodymium ions, indium ions, dysprosium ions, lanthanum ions, A solution containing at least one polyvalent rare metal ion selected from yttrium ions, tantalum ions, niobium ions, tungsten ions, and molybdenum ions is preferred.

A lithium ion battery is composed of members such as a positive electrode material, a negative electrode material, a separator and an electrolyte. In particular, rare metals such as cobalt or nickel that become polyvalent ions are contained in the positive electrode material, so a solution containing polyvalent rare metal ions derived from the rare metals contained in the positive electrode material is more preferable.

In addition, the solution containing polyvalent rare metal ions contains alkali metals such as sodium and potassium, alkaline earth metals such as magnesium and calcium, typical elements such as aluminum, tin and lead, and transition elements such as iron and copper. It may further contain at least one element.

In the present invention, the solution containing the polyvalent rare metal ions preferably has a concentration of polyvalent rare metal ions to be recovered of 0.5 mg/L or more and 100,000 mg/L or less. If the concentration of polyvalent rare metal ions to be recovered is 0.5 mg/L or more, it is possible to recover a more useful amount of polyvalent rare metal. In addition, since the amount of polyvalent rare metal ions to be collected is 100,000 mg/L or less, precipitation of salts in the process can be further suppressed.

The solution containing polyvalent rare metal ions preferably has a total metal ion concentration of 100,000 mg/L or less, more preferably 90,000 mg/L or less. As the ion concentration in the liquid rises, solid matter is generated, which may damage the film surface.

Further, in the present invention, the solution containing the polyvalent rare metal ions has a ratio of the total concentration of monovalent rare metal ions (mg/L)/the total concentration of polyvalent rare metal ions (mg/L) of 0 or more and less than 100. It is preferably less than 10, more preferably less than 10. When the ratio is less than 100, the risk of precipitation of monovalent rare metal ion salts in the concentration step can be reduced, and polyvalent rare metal ions can be concentrated and separated more efficiently.

The mass of the polyvalent rare metal ions is calculated, for example, by summing the ion-equivalent masses of cobalt ions, nickel ions, and the like. Also, the mass of the monovalent rare metal ion is calculated by summing the ion-equivalent masses of lithium ions, cesium ions, and the like. Although some elements may exist in an aqueous solution as polyatomic ions instead of monoatomic ions, the reduced mass is the mass when it is assumed that they exist as monoatomic ions. The multivalent and monovalent rare metal ion equivalent masses are obtained, for example, by analyzing the aqueous solution to be measured using a P-4010 type ICP (Inductively Coupled Plasma Emission Spectrometer) device manufactured by Hitachi Co., Ltd., and determining the concentration of various rare metal ions. (mg/L) can be determined by quantification.

Further, the pH of the solution is preferably in the range of 3 or less, more preferably 2 or less. This is because precipitation may occur under basic conditions, causing clogging of piping. On the other hand, if the acidity of the solution becomes too high, deterioration of the membrane performance is accelerated.

[2] Concentration step In this step, by supplying the undiluted solution to the membrane, a non-permeated liquid having a higher concentration of polyvalent rare metal ions than the solution X and a permeated liquid having a lower concentration of polyvalent rare metal ions are obtained.

The concentration step may be carried out after the separation step when the separation step by solvent extraction, which will be described later, is carried out. However, since the concentration step has the effect of improving the recovery rate of polyvalent rare metal ions in the separation step and the recovery step by solvent extraction, when the total metal ion concentration of solution X is 50,000 mg / L or less, the solvent It is preferable to carry out the concentration step before the separation step by extraction.

However, when the total metal ion concentration in the solution X is more than 50,000 mg / L, if the solution X is treated directly in the concentration step, the salt is likely to precipitate in the process, so the concentration step is not performed, and solvent extraction is performed. Preferably, the separation step is performed first, followed by the concentration step. That is, in the separation step by solvent extraction, a liquid Y having a high concentration of polyvalent rare metal ions to be recovered and a remaining liquid Z are obtained. It is preferable to carry out the concentration step when the concentration becomes 5,0000 mg/L or less. Further, the residual liquid Z also contains desired polyvalent rare metal ions other than the polyvalent rare metal ions to be recovered, and the concentration of the desired polyvalent rare metal ions in the residual liquid Z is 5. ,0000 mg/L or less, it is preferable to carry out the concentration step using this as a stock solution.

(1) Membrane In the concentration step, by using the following membrane, loss of polyvalent rare metal ions is extremely small, and concentration can be performed at a high recovery rate. When the concentrate obtained in the concentration step is treated in the solvent extraction step described later, the loss of polyvalent metal ions in the solvent extraction step can be further reduced, so the recovery rate of polyvalent metal ions is further improved. Furthermore, in the step of recovering salts and rare metals derived from polyvalent rare metal ions, which will be described later, the loss of polyvalent rare metal ions can be reduced and the recovery rate can be improved.

(Membrane) A membrane having an isopropyl alcohol removal rate of 40% or more when a 1,000 mg/L isopropyl alcohol aqueous solution having a pH of 6.5 at 25° C. and an operating pressure of 0.5 MPa is permeated.

By using such a membrane, loss of polyvalent rare metal ions is extremely small, and concentration can be achieved at a high recovery rate. In addition, when a separation step, which will be described later, is performed, the loss of polyvalent metal ions can be further reduced, and the recovery rate of polyvalent metal ions can be further improved. As a result, even in the recovery step for recovering salts and rare metals derived from polyvalent rare metal ions, the loss of polyvalent rare metal ions can be reduced and the recovery rate can be improved.

As the membrane having the above characteristics, when the pH of the solution X is 3 or less, a 1,000 mg/L isopropyl alcohol aqueous solution having the same pH as the solution X was permeated at 25° C. at an operating pressure of 0.5 MPa. It is preferable that the removal rate of isopropyl alcohol at the time is 40% or more. When the pH of the solution X is 3 or less, especially when the removal rate of isopropyl alcohol at the pH of the solution X is 40% or more, the loss of polyvalent rare metal ions can be further reduced. In addition, even if the pH of the solution X to be treated is not limited, the membrane can be treated with an isopropyl alcohol aqueous solution of pH 6.5 at 25°C at an operating pressure of 0.5 MPa, and/or at 25°C at an operating pressure of 0.5 MPa, pH 3 or less. It is preferable that the removal rate of isopropyl alcohol is 70% or more when the isopropyl alcohol aqueous solution of is permeated. When the removal rate is 70% or more, the loss of polyvalent rare metal ions can be further reduced.

As the film having the above properties, details will be described later, but for example, it contains a crosslinked aromatic polyamide, and the crosslinked aromatic polyamide has at least one of the structures represented by the above formula (1) or (2). It preferably has a structure. The terminal amino group of the crosslinked aromatic polyamide becomes positively charged under acidic conditions, which causes swelling of the membrane and lowers the ion removal performance. , it is possible to maintain high ion removal properties even under acidic conditions, and to stably concentrate polyvalent rare metal ions with high efficiency over a long period of time.

(Ar ₁ to Ar ₃ are each independently an optionally substituted aromatic ring having 5 to 14 carbon atoms, and R ₁ is an atom having neither an aromatic ring nor a hetero atom group, X is a hydrogen atom or a carboxy group, and R ₂ to R ₅ are each independently a hydrogen atom or an aliphatic chain having 1 to 10 carbon atoms.)

Here, it is preferable that R ₂ to R ₅ are hydrogen atoms and Ar ₁ to Ar ₃ are optionally substituted benzene rings. Further, it is preferable that R ₁ has 1 to 5 carbon atoms. As such a membrane, for example, a composite semipermeable membrane comprising a support layer having a porous indicator membrane provided on a substrate and a separation function layer made of a crosslinked aromatic polyamide provided on the porous support layer. can be mentioned. The separation functional layer has substantially separation performance, while the support layer is permeable to water but has substantially no separation performance for ions and the like, and can give strength to the separation functional layer. . Among composite semipermeable membranes, reverse osmosis membranes capable of highly removing polyvalent rare metal ions are preferred.

(2) Stock solution The stock solution to be concentrated by the membrane is basically a solution containing the polyvalent rare metal ions, and the above solution X may be directly supplied to the membrane as the stock solution, or separated by solvent extraction, which will be described later. The separated liquid obtained in the process may be supplied to the membrane as a stock solution. At this time, the separation liquid may be a recovery liquid having a high concentration of polyvalent rare metal ions to be recovered, which is obtained in the separation step by solvent extraction, or may be a recovery liquid to be recovered in the separation step by solvent extraction. The residual liquid may be a residual liquid having a low polyvalent rare metal ion concentration and containing desired polyvalent rare metal ions other than the polyvalent rare metal ions to be recovered.

(3) Operating conditions The operating pressure (that is, the pressure of the undiluted solution) in the concentration step is preferably 0.5 MPa or more and 12 MPa or less. The higher the pressure, the higher the membrane permeation rate, and a pressure of 0.5 MPa or more can realize a practical membrane permeation rate. Further, by setting the operating pressure to 12 MPa or less, damage to the membrane can be suppressed. Further, the operating pressure is more preferably 1 MPa or more and 10 MPa or less, and further preferably 2 MPa or more and 8 MPa or less.

(4) Concentration times The concentration step may be a single-stage or multi-stage process as long as it is a membrane process. For example, it includes at least first and second membrane concentration steps, and A second concentration step may be performed with the permeate as the stock solution.

(5) Non-permeated liquid and permeated liquid In the concentration step, a raw liquid is supplied to the membrane, and a non-permeated liquid having a higher polyvalent rare metal ion concentration than the raw liquid and a permeated liquid having a lower polyvalent rare metal ion concentration than the raw liquid are used. get The non-permeated liquid can also be referred to as a concentrated liquid.

[3] Separation step In the present invention, a separation step may be performed in addition to the concentration step described above. In the separation step, a liquid having a high concentration of polyvalent rare metal ions to be recovered and the target to be recovered are separated from the solution X or the non-permeated liquid obtained in the concentration step by solvent extraction. It is preferable to obtain a liquid having a low concentration of polyvalent rare metal ions.

Here, the separation step may be repeated multiple times in order to extract a plurality of polyvalent rare metal ions. That is, the liquid having a low concentration of rare metal ions to be recovered, obtained in the previous separation step, contains multivalent rare metal ions different from the multivalent rare metal ions extracted in the previous separation step. In some cases, the liquid may be further subjected to a separation step by solvent extraction.

As described above, by performing the concentration step before the separation step, the efficiency of solvent extraction in the separation step is improved, and the recovery rate of the desired polyvalent rare metal ions is increased. When the total metal ion concentration in is 50,000 mg/L or less, it is preferable to perform the separation step after performing the concentration step.

(1) Solvent Extraction As described above, the solvent extraction may be performed multiple times depending on the type of the desired rare metal ion, but the case where the solvent extraction is performed once will be described below.

Solvent extraction includes forward extraction and may further include reverse extraction.

In forward extraction, the solution X or the non-permeated liquid obtained in the concentration step is used as an aqueous phase solution after pH adjustment, and most of the polyvalent rare metal ions to be recovered are extracted from the aqueous phase solution. Alternatively, most of the metal ions other than the polyvalent rare metal ions to be recovered are distributed to the organic phase by subjecting them to an organic phase containing an extractant and a diluent.

Reverse extraction is carried out after forward extraction, and when most of the polyvalent rare metal ions to be recovered are in the organic phase, an aqueous phase adjusted to a predetermined pH is applied to the organic phase to obtain the target to be recovered. Most of the multivalent rare metal ions are distributed to the aqueous phase. After forward extraction, if most of the polyvalent rare metal ions to be recovered are in the aqueous phase, the above-mentioned back extraction may be performed for the purpose of recovering the organic phase (extractant, diluent). .

The extractant in forward extraction is appropriately selected depending on the presence or absence of polyvalent rare metal ions to be recovered and other ion species. For example, in the case of processing a mixed solution of cobalt and nickel, when the polyvalent rare metal ions to be recovered are nickel ions or cobalt ions, tri-normal-octylamine (TNOA) or tri-iso-octylamine (TIOA) and other amine extractants, mono-2-ethylhexyl 2-ethylhexylphosphonate (product name: PC-88A), di-(2-ethylhexyl)phosphonic acid (D2EHPA), bis(2,4,4) -trimethylpentyl)phosphinic acid (product name: Cyanex 272) and other acidic phosphate extractants are preferably used.

The extractant concentration in the organic phase (extractant and diluent) is preferably 20% by volume or more and 40% by volume or less. When it is 20% by volume or more, the polyvalent rare metal ions to be recovered or the metal ions other than the polyvalent rare metal ions to be recovered can be efficiently distributed to the organic phase. On the other hand, by making it 40 volume% or less, the viscosity increase of the organic phase is suppressed, and the oil-water separation performance is improved.

In solvent extraction, the smaller the ratio O/A of the volume of the organic phase to the volume of the aqueous phase, the lower the flow rate of the organic phase. This is advantageous in terms of facility costs and operating costs. Therefore, O/A is preferably 10 or less.

In the solvent extraction, the higher the concentration of the polyvalent rare metal ions to be recovered or the metal ions other than the polyvalent rare metal ions to be recovered in the organic phase (extractant, diluent), the higher the O/A. Although it is preferable because it can be made small, it is preferable to manage it at 10,000 mg/L or less. If it exceeds 10,000 mg/L, the viscosity of the organic phase increases, and the oil-water separation performance tends to decrease.

Aromatic hydrocarbons are preferably used as diluents in positive extraction.

In the solvent extraction, the higher the polyvalent rare metal ion concentration to be recovered in the aqueous phase, the higher the recovery rate. Therefore, it is preferably 1,000 mg/L or more, more preferably 10,000 mg/L or more. On the other hand, the polyvalent rare metal ion concentration to be recovered in the aqueous phase is preferably 100,000 mg/L or less. When the amount is 100,000 mg/L or less, it is possible to suppress a decrease in the recovery rate due to the formation of precipitates derived from the polyvalent rare metal ions to be recovered.

From the viewpoint of the recovery rate of polyvalent rare metal ions, the solvent extraction is preferably carried out by a multi-stage countercurrent system, for example, using a mixer-settler system.

[4] Recovery step In the recovery step, a salt containing a metal species constituting a polyvalent rare metal ion or a Take out a single rare metal. The stock solution in this recovery step is the liquid having the higher concentration of polyvalent rare metal ions to be recovered, which is obtained when the concentration step and the separation step are performed in this order, and which is obtained when the separation step is performed. Moreover, when the separation step and the concentration step are carried out in this order, it is a non-permeated liquid obtained in the concentration step.

For the recovery step, for example, crystallization, electrowinning, or the like is preferably used, and a recovery step including both crystallization and electrowinning is also suitable.

Crystallization can precipitate a poorly soluble salt or hydroxide salt, for example, by adding a salt or an alkali to the stock solution in this step. In crystallization, the higher the concentration of the polyvalent rare metal ion to be recovered, the greater the difference in solubility from the polyvalent rare metal salt, so the recovery efficiency of the salt and rare metal derived from the polyvalent rare metal ion is improved. .

In electrowinning, for example, an insoluble anode made of a titanium plate coated with iridium oxide is used as a cathode, and a thin plate of pure metal of the polyvalent rare metal to be recovered is used as a cathode. A metal derived from polyvalent rare metal ions to be recovered can be deposited around the . Also in electrowinning, the higher the concentration of polyvalent rare metal ions to be recovered, the higher the current efficiency, so the recovery efficiency of the metal derived from the polyvalent rare metal ions is improved.

For the above reason, if the concentration step is performed in addition to the separation step, the recovery rate of the desired polyvalent rare metal ion-derived salt and rare metal can be further improved in the recovery step.

[5] Details of Membrane The membrane according to the present invention only needs to have the separation performance described above. A composite semipermeable membrane having a separation function membrane provided can be used. Such a composite semipermeable membrane is used as an element by being wound around a perforated central tube together with a raw liquid channel material and a concentrated liquid channel material. As a method for manufacturing the element, methods disclosed in Japanese Patent Publication No. 44-14216, Japanese Patent Publication No. 4-11928, or Japanese Patent Application Laid-Open No. 11-226366 can be used.

(1) Support layer In the present invention, the support layer preferably comprises a substrate and a porous support membrane, but is not limited to this configuration. For example, the support layer may be composed of only a porous support membrane without a substrate.

(2) Substrate Substrates include polyester-based polymers, polyphenylene sulfide-based polymers, polyamide-based polymers, polyolefin-based polymers, and mixtures or copolymers thereof. Among them, fabrics of polyester-based polymers or polyphenylene sulfide-based polymers having high mechanical and thermal stability are particularly preferable. As the form of the fabric, a long-fiber nonwoven fabric, a short-fiber nonwoven fabric, and a woven or knitted fabric can be preferably used.

(3) Porous Supporting Membrane In the present invention, the porous supporting membrane does not substantially have the ability to separate ions and the like, but provides strength to the separation function layer that has substantially the ability to separate ions. The pore size and distribution of the porous support membrane are not particularly limited. For example, it has uniform fine pores, or fine pores that gradually enlarge from the surface on which the separation functional layer is formed to the other surface, and the surface on which the separation functional layer is formed has fine pores. A porous support membrane having a size of 0.1 nm or more and 100 nm or less is preferred.

Materials for the porous support membrane include, for example, homopolymers or copolymers such as polysulfone, polyethersulfone, polyamide, polyester, cellulosic polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, and polyphenylene oxide, alone. Or they can be mixed and used. Cellulose-based polymers such as cellulose acetate and cellulose nitrate, and vinyl polymers such as polyethylene, polypropylene, polyvinyl chloride and polyacrylonitrile can be used.

Among them, homopolymers or copolymers such as polysulfone, polyamide, polyester, cellulose acetate, cellulose nitrate, polyvinyl chloride, polyacrylonitrile, polyphenylene sulfide and polyphenylene sulfide sulfone are preferred. Cellulose acetate, polysulfone, polyphenylene sulfide sulfone, or polyphenylene sulfone are more preferred. Furthermore, among these materials, polysulfone can generally be used because it has high chemical, mechanical and thermal stability and is easy to mold.

Polysulfone preferably has a mass average molecular weight (Mw) of 10,000 or more and 200,000 or less when measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a solvent and polystyrene as a standard substance. , more preferably 15,000 or more and 100,000 or less. When the Mw of polysulfone is 10,000 or more, it is possible to obtain mechanical strength and heat resistance that are preferable as a porous support membrane. Further, when the Mw is 200,000 or less, the viscosity of the solution is in an appropriate range, and good moldability can be achieved.

The thickness of the substrate and the porous support membrane affect the strength of the composite semipermeable membrane and the packing density when it is made into an element. In order to obtain sufficient mechanical strength and packing density, the total thickness of the substrate and the porous support membrane (that is, the thickness of the porous support layer) is preferably 30 μm or more and 300 μm or less, and 100 μm or more and 220 μm or less. is more preferable. Moreover, the thickness of the porous support membrane is preferably 20 μm or more and 100 μm or less. In addition, unless otherwise noted, the thickness represents an arithmetic mean value. That is, the thickness of the base material and the porous support membrane can be obtained by calculating the average value of 20 thicknesses measured at intervals of 20 μm in the direction perpendicular to the thickness direction (the surface direction of the membrane) by cross-sectional observation.

(4) Step of Forming Porous Support Membrane The step of forming a porous support film includes a step of applying a polymer solution to a base material and a step of immersing the base material coated with the solution in a coagulation bath to solidify the polymer. including.

In the step of coating the base material with the polymer solution, the polymer solution is prepared by dissolving the polymer, which is a component of the porous support membrane, in a good solvent for the polymer.

The temperature of the polymer solution during coating is preferably in the range of 10° C. to 60° C. when polysulfone is used as the polymer. If the temperature of the polymer solution is within this range, the polymer will not precipitate, and the polymer solution will solidify after being sufficiently impregnated between the fibers of the substrate. As a result, it is possible to obtain a porous support film firmly bonded to the base material by the anchor effect. The preferred temperature range of the polymer solution can be appropriately adjusted depending on the type of polymer used, desired solution viscosity, and the like.

The time from application of the polymer solution on the substrate to immersion in the coagulation bath is preferably in the range of 0.1 to 5 seconds. If the time until immersion in the coagulation bath is within this range, the polymer-containing organic solvent solution is sufficiently impregnated between the fibers of the base material and then solidified. The preferred range of time until immersion in the coagulation bath can be appropriately adjusted depending on the type of polymer solution to be used, the desired solution viscosity, and the like.

Water is usually used as the coagulation bath, but any bath that does not dissolve the polymer component of the porous support membrane may be used. The temperature of the coagulation bath is preferably -20°C to 100°C. More preferably, the temperature of the coagulation bath is between 10°C and 50°C. If the temperature of the coagulation bath is 100° C. or less, the vibration of the coagulation bath surface due to thermal motion can be suppressed, and the smoothness of the film surface after film formation can be maintained. Also, if the temperature is -20° C. or higher, the solidification rate can be maintained, so the film formability can be improved.

The support membrane thus obtained may then be washed with hot water to remove residual solvent in the membrane. The temperature of the hot water at this time is preferably 40°C to 100°C, more preferably 60°C to 95°C. If the washing temperature is equal to or lower than the upper limit, the degree of shrinkage of the support membrane does not become too large, and deterioration in water permeability can be suppressed. Also, if the washing temperature is 40° C. or higher, a high washing effect can be obtained.

(5) Separation Functional Layer The separation functional layer provided on the porous support layer is a layer that substantially exhibits the membrane performance described above. The separation functional layer preferably has a fold structure on the surface, which is a repetition of convex portions and concave portions. By having a pleated structure with protrusions and recesses, the surface area of the separation functional layer is increased, and high water permeability can be obtained.

The separation functional layer is generally composed of cellulose acetate-based polymer, polyamide, etc., but preferably composed of polyamide from the viewpoint of chemical stability against acids and alkalis and removal of ions, and crosslinked aromatic polyamide. is preferably contained as a main component. The main component refers to a component that accounts for 50% by mass or more of the components of the separation functional layer. The separation functional layer can exhibit high removal performance by containing 50% by mass or more of the crosslinked aromatic polyamide. Moreover, the content of the crosslinked aromatic polyamide in the separation functional layer is more preferably 90% by mass or more, further preferably 95% by mass or more.

The separating functional layer containing such crosslinked aromatic polyamide is a thin film of crosslinked aromatic polyamide, which is obtained by polymerizing a polyfunctional aromatic amine and a polyfunctional aromatic acid halide.

Here, at least one of the polyfunctional aromatic amine and the polyfunctional aromatic acid halide preferably contains a trifunctional or higher compound. This results in a rigid molecular chain and a good pore structure for concentrating solutes with small ion sizes such as lithium ions. Therefore, it preferably contains a crosslinked aromatic polyamide obtained by interfacial polymerization of a polyfunctional aromatic amine and a divalent or higher polyfunctional aromatic acid halide.

A polyfunctional aromatic amine has two or more amino groups of at least one of a primary amino group and a secondary amino group in one molecule, and at least one of the amino groups is a primary It means an aromatic amine which is an amino group. Examples of polyfunctional aromatic amines include o-phenylenediamine, m-phenylenediamine, p-phenylenediamine, o-xylylenediamine, m-xylylenediamine, p-xylylenediamine, o-diaminopyridine, m- Diaminopyridine, p-diaminopyridine, etc. Polyfunctional aromatic amines in which two amino groups are bonded to an aromatic ring in either the ortho-, meta-, or para-position, 1,3,5-triaminobenzene , 1,2,4-triaminobenzene, 3,5-diaminobenzoic acid, 3-aminobenzylamine, and polyfunctional aromatic amines such as 4-aminobenzylamine. In particular, m-phenylenediamine, p-phenylenediamine, and 1,3,5-triaminobenzene are preferably used in consideration of selective separation, permeability and heat resistance of the membrane. Among them, it is more preferable to use m-phenylenediamine (hereinafter also referred to as m-PDA) because of its availability and ease of handling. These polyfunctional aromatic amines may be used alone or in combination of two or more.

A polyfunctional aromatic acid halide is an aromatic acid halide having two or more halogenated carbonyl groups in one molecule, and the reaction with the polyfunctional aromatic amine gives an aromatic polyamide. is not particularly limited. Examples of polyfunctional aromatic acid halides include 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 1, Halides such as 3,5-benzenetrisulfonic acid and 1,3,6-naphthalenetrisulfonic acid can be used. Among acid halides, acid chlorides are preferred, and acid halides of 1,3,5-benzenetricarboxylic acid are particularly preferred from the viewpoints of economic efficiency, availability, ease of handling, ease of reactivity, and the like. Trimesic acid chloride, isophthalic acid chloride which is an acid halide of 1,3-benzenedicarboxylic acid, terephthalic acid chloride which is an acid halide of 1,4-benzenedicarboxylic acid, acid of 1,3,5-benzenetrisulfonic acid 1,3,5-Benzenetrisulfonic acid chloride which is a halide, 1,3,6-naphthalenetrisulfonic acid chloride which is an acid halide of 1,3,6-naphthalenetrisulfonic acid is preferred, and trimesic acid chloride is preferred. Especially preferred. The above polyfunctional acid halides may be used alone or in combination of two or more. - By mixing either difunctional isophthalic acid chloride or terephthalic acid chloride with naphthalenetrisulfonic acid chloride, the molecular gaps of the polyamide crosslinked structure are expanded, and a membrane with a uniform pore size distribution can be controlled over a wide range. can do. The mixing molar ratio of the trifunctional acid chloride and the bifunctional acid chloride is preferably 1:20 to 50:1, more preferably 1:1 to 20:1.

The crosslinked aromatic polyamide has an amide group derived from a polymerization reaction of a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride, and amino and carboxy groups derived from unreacted terminal functional groups. The amount of these functional groups affects the water permeability and salt removal rate of the composite semipermeable membrane.

If chemical treatment is performed after the formation of the crosslinked aromatic polyamide, it is possible to convert the functional groups in the crosslinked aromatic polyamide or introduce new functional groups into the crosslinked aromatic polyamide. It is possible to improve the amount of permeated water and the salt removal rate. Functional groups to be introduced include alkyl groups, alkenyl groups, alkynyl groups, hydroxyl groups, amino groups, carboxy groups, ether groups, thioether groups, ester groups, aldehyde groups, nitro groups, nitroso groups, nitrile groups, azo groups, and the like. be done.

(6) Separation Functional Layer Forming Step The separation functional layer forming step includes a polymerization step and a modification step.

The polymerization step is, for example, a layer containing a crosslinked aromatic polyamide having a structure represented by the following formula (3) on a porous support layer having a substrate and a porous support film on the substrate. It is a step of forming

(Ar ₁ to Ar ₃ are each independently an aromatic ring having 5 to 14 carbon atoms which may have a substituent, and R ₃ to R ₅ are each independently a hydrogen atom or a carbon Aliphatic chains with numbers from 1 to 10.)

Specifically, it is a step of forming a crosslinked aromatic polyamide by polycondensing a polyfunctional aromatic amine and a polyfunctional aromatic acid chloride, and more specifically, an aqueous solution containing a polyfunctional aromatic amine. is brought into contact with the porous support membrane, and then the porous support membrane is brought into contact with the polyfunctional aromatic acid chloride solution. Here, the case where the porous support layer includes a base material and a porous support film is taken as an example. ".

The concentration of the polyfunctional aromatic amine in the polyfunctional aromatic amine aqueous solution is preferably in the range of 0.1% by mass or more and 20% by mass or less, more preferably in the range of 0.5% by mass or more and 15% by mass or less. is. If the concentration of the polyfunctional aromatic amine is within this range, sufficient solute removal performance and water permeability can be obtained.

After bringing the polyfunctional aromatic amine aqueous solution into contact with the porous support membrane, it is drained so that no droplets remain on the membrane. By draining off the liquid, it is possible to prevent the droplet remaining portion from becoming a film defect and lowering the removal performance after the separation functional layer is formed. As a method of draining, the support layer after contact with the polyfunctional aromatic amine aqueous solution is held vertically and the excess aqueous solution is allowed to flow down naturally, or an air stream such as nitrogen is blown from an air nozzle to forcibly drain. and the like can be used. Also, after draining, the film surface can be dried to partially remove water from the aqueous solution.

The concentration of the polyfunctional aromatic acid chloride in the organic solvent solution is preferably in the range of 0.01% by mass or more and 10% by mass or less, and is in the range of 0.02% by mass or more and 2.0% by mass or less. It is even more preferable to have This is because a content of 0.01% by mass or more provides a sufficient reaction rate, and a content of 10% by mass or less can suppress the occurrence of side reactions.

The organic solvent is preferably one that is immiscible with water, dissolves the polyfunctional aromatic acid chloride, does not destroy the support film, and is inert to the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride. Anything is fine. Preferred examples include hydrocarbon compounds such as n-nonane, n-decane, n-undecane, n-dodecane, isooctane, isodecane and isododecane, and mixed solvents.

The organic solvent solution containing the polyfunctional aromatic acid chloride may be brought into contact with the porous support membrane in the same manner as the method of coating the porous support membrane with the polyfunctional aromatic amine aqueous solution.

After contact with the polyfunctional aromatic acid chloride solution, the liquid may be drained in the same manner as the polyfunctional aromatic amine aqueous solution. For draining, a method using a mixed fluid of water and air can also be adopted in addition to the method mentioned for the polyfunctional aromatic amine aqueous solution.

At the interface between the polyfunctional aromatic amine aqueous solution and the polyfunctional aromatic acid chloride solution, polycondensation of the polyfunctional aromatic amine and the polyfunctional aromatic acid chloride, which are monomers, produces a crosslinked aromatic polyamide. . Polycondensation is preferably carried out at 80° C. or lower. "Polycondensation is carried out at 80 ° C. or less" means that at least the temperature around the support film from the time of coating the polyfunctional aromatic acid chloride until the subsequent draining, and the temperature of the polyfunctional aromatic acid chloride solution are 80 ° C. It means that:

Unreacted monomers can be removed by washing the film thus obtained with hot water. The temperature of the hot water is 40°C or higher and 100°C or lower, preferably 60°C or higher and 100°C or lower.

Next, in the modification step, the film obtained through the polymerization step described above is reacted with an aliphatic carboxylic acid derivative. The aliphatic carboxylic acid derivative may be brought into contact as it is, or may be dissolved in a solvent that does not degrade the support layer and brought into contact with the membrane.

As a method of bringing the aliphatic carboxylic acid derivative into contact with the separation functional layer, the reaction may be carried out by coating the derivative, or the membrane containing the separation functional layer may be immersed in the aliphatic carboxylic acid derivative or a solution containing the same. may be reacted.

The reaction time and temperature when the aliphatic carboxylic acid derivative is applied as an aqueous solution or as it is to the film obtained in the polymerization step can be appropriately adjusted depending on the type of the aliphatic carboxylic acid derivative and the application method. When the aliphatic carboxylic acid derivative is applied as an aqueous solution, the concentration of the aqueous solution is preferably 10 mmol/L to 100 mmol/L, more preferably 30 mmol/L to 100 mmol/L, from the viewpoint of improving the acid resistance and chlorine resistance of the separation functional layer. L is more preferred.

EXAMPLES The present invention will be described below with reference to Examples, but the present invention is not limited to these Examples.

1. Measurement (Isopropyl alcohol removal rate of membrane)
For each aqueous solution of 1,000 mg/L isopropyl alcohol acidified with sulfuric acid at pH 6.5 and pH 1 at 25°C, the isopropyl alcohol concentrations of the permeate and feed water when permeated through the membrane at an operating pressure of 0.5 MPa were calculated. Evaluated by comparison.

That is, the isopropyl alcohol removal rate (%) was calculated as follows: 100×(1−(concentration of isopropyl alcohol in permeated water/concentration of isopropyl alcohol in feed water)). The isopropyl alcohol concentration was determined using a gas chromatograph (GC-18A manufactured by Shimadzu Corporation).

(Rare metal ion concentration in solution)
Using a P-4010 type ICP (Inductively Coupled Plasma Emission Spectrometer) device manufactured by Hitachi, Ltd., the lithium ion concentration, cobalt ion concentration, and nickel ion concentration in the solution were quantified.

(Ratio of total concentration of monovalent rare metal ions to total concentration of polyvalent rare metal ions)
Using various ion concentrations in the solution, the ratio of the total concentration of monovalent rare metal ions to the total concentration of polyvalent rare metal ions was calculated as the ratio of lithium ion concentration/(cobalt ion concentration+nickel ion concentration).

(Total metal ion concentration)
Using various ion concentrations in the solution, total metal ion concentration (mg/L)=lithium ion concentration (mg/L)+cobalt ion concentration (mg/L)+nickel ion concentration (mg/L) was calculated.

(Recovery rate)
In the present examples and comparative examples, the rare metal to be recovered is cobalt,
Recovery rate (%) = mass (g) of metallic cobalt precipitated in the recovery step/(concentration of cobalt ions in the solution (mg/L) x liquid volume (L) introduced in the step).

2. Fabrication of membrane (Fabrication of porous support layer)
A 15.0% by mass solution of polysulfone in dimethylformamide (DMF) was cast at room temperature (25° C.) to a thickness of 180 μm on a non-woven fabric made of polyester fiber (air permeability of 0.5 to 1 cc/cm ² /sec), and immediately purified. A porous support layer (thickness: 150 to 160 μm) consisting of a fiber-reinforced polysulfone support layer was prepared by immersing it in water and allowing it to stand for 5 minutes. This was used to prepare membranes AE below.

(Preparation of membrane A)
After the porous support layer was immersed in an aqueous solution containing 1.8% by mass of m-phenylenediamine (m-PDA) for 15 seconds, nitrogen was blown from an air nozzle to remove excess aqueous solution. A 30°C n-decane solution containing .07% by mass was uniformly applied to the entire surface of the porous support membrane, allowed to stand at 30°C for 1 minute, and two fluids (pure water and air) were sprayed onto the membrane surface. , to remove the surface solution. After that, it was washed with pure water at 80° C. to obtain a reverse osmosis membrane A having the performance shown in Table 1. The reverse osmosis membrane A did not include the structures of the formulas (1) and (2), but included the structure corresponding to the formula (3).

(Preparation of membrane B)
After the porous support layer was immersed in an aqueous solution containing 3.0% by mass of m-phenylenediamine (m-PDA) for 15 seconds, nitrogen was blown from an air nozzle to remove excess aqueous solution. A 40° C. n-decane solution containing 15% by mass was uniformly applied to the entire surface of the porous support membrane, dried by heating at 80° C. for 1 minute, and two fluids (pure water and air) were sprayed onto the membrane surface. , to remove the surface solution. Next, it was washed with pure water at 80°C. After that, it was immersed in a 1.0% by mass aqueous solution of acetic anhydride at 25° C. for 2 minutes, and then washed with pure water at 30° C. to obtain a reverse osmosis membrane B having the performance shown in Table 1. The reverse osmosis membrane B contained the structures represented by the formulas (1), (2) and (3).

(Preparation of film C)
The porous support layer was immersed in an aqueous solution containing 2.3% by weight of piperazine and 0.15% by weight of m-phenylenediamine (m-PDA) for 2 minutes, and the support layer was slowly pulled up in the vertical direction. After removing excess aqueous solution from the surface of the support layer by blowing nitrogen through a nozzle, an n-decane solution containing 0.2% by mass of trimesic acid chloride was added at a rate of 160 cm ³ /m ² so that the surface of the support layer was completely wetted. It was applied and heated in an atmosphere of 80° C. for 1 minute. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 1 minute to drain, and dried by blowing gas at 20° C. using an air blower. After drying, it was immediately washed with water and stored at room temperature to obtain a nanofiltration membrane C having the performance shown in Table 1. The nanofiltration membrane C did not include any of the structures of formulas (1), (2) and (3).

(Preparation of film D)
The porous support layer was immersed in an aqueous solution containing 1.5% by mass of piperazine for 2 minutes, the support layer was slowly lifted vertically, and nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support layer. After that, an n-decane solution containing 0.1% by mass of trimesic acid chloride was applied at a rate of 160 cm ³ /m ² so that the support layer surface was completely wetted, and heated in an atmosphere of 80° C. for 1 minute. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 1 minute to drain, and dried by blowing gas at 20° C. using an air blower. After drying, it was immediately washed with water and stored at room temperature to obtain a nanofiltration membrane D having the performance shown in Table 1. The nanofiltration membrane D did not include any of the structures represented by the formulas (1), (2) and (3).

(Preparation of membrane E)
The porous support layer was immersed in an aqueous solution containing 2.3% by weight of piperazine and 0.05% by weight of m-phenylenediamine (m-PDA) for 2 minutes, and the support layer was slowly lifted vertically and air was removed. After removing excess aqueous solution from the surface of the support layer by blowing nitrogen through a nozzle, an n-decane solution containing 0.2% by mass of trimesic acid chloride was added at a rate of 160 cm ³ /m ² so that the surface of the support layer was completely wetted. It was applied and heated in an atmosphere of 80° C. for 1 minute. Next, in order to remove excess solution from the membrane, the membrane was held vertically for 1 minute to drain, and dried by blowing gas at 20° C. using an air blower. After drying, it was immediately washed with water and stored at room temperature to obtain a nanofiltration membrane E having performance shown in Table 1. The nanofiltration membrane E did not include any of the structures of formulas (1), (2) and (3).

3. Preparation of solutions (solutions A to E)
Lithium sulfate, cobalt sulfate, and nickel sulfate were dissolved in a 1 mol/L sulfuric acid aqueous solution and adjusted to pH 1 with sulfuric acid to prepare solutions A to E having the compositions shown in Table 2.

4. Examples and Comparative Examples (Example 1)
50 L of solution A were first treated as stock solution for the concentration step by Membrane A and then the retentate from the concentration step was treated in the separation step.

The concentration step was performed at a liquid temperature of 25° C., an operating pressure of 12 MPa, and a volume ratio of permeated water:non-permeated water=6:4.

The separation step was carried out by a solvent extraction method using a mixer-settler apparatus. First, the non-permeated liquid obtained in the concentration step is used as an aqueous phase after adjusting the pH, and bis(2,4,4-trimethylpentyl)phosphinic acid, which is an extractant for cobalt, is used for kerosene, which is a diluent. (Product name: Cyanex 272) was dissolved at 30% by volume as an organic phase, which was brought into contact with an aqueous phase to carry out positive extraction. After that, the organic phase having a high concentration of cobalt ions was brought into contact with an aqueous sulfuric acid solution to back-extract to the aqueous phase.

A recovery step was performed on the aqueous phase obtained by back extraction.

In the recovery process, an insoluble anode made of a titanium plate coated with iridium oxide was used, and a pure metal thin plate of cobalt was used as a cathode, and electricity was applied to deposit cobalt around the cathode.

The recovery rate was calculated from the mass of precipitated cobalt and shown in Table 3.

(Example 2)
50 L of solution A was first processed through a separation step.

The separation step was performed in the same manner as described in Example 1, except that Solution A was used as the aqueous phase of the positive extraction.

The aqueous phase obtained by the back extraction in the separation step was used as the raw liquid, and was treated in the same concentration step using Membrane A as in Example 1. The resulting non-permeated liquid was subjected to the recovery step in the same manner as in Example 1. carried out.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Example 3)
It was carried out in the same manner as in Example 1, except that Solution B was used instead of Solution A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Example 4)
It was carried out in the same manner as in Example 2, except that Solution C was used instead of Solution A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Example 5)
It was carried out in the same manner as in Example 1, except that the solution C was used instead of the solution A, and the ratio of permeated water:non-permeated water in the concentration step was set to 3:7.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Example 6)
It was carried out in the same manner as in Example 1, except that film B was used instead of film A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Example 7)
It was carried out in the same manner as in Example 1, except that film C was used instead of film A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Example 8)
It was carried out in the same manner as in Example 1 except that Solution D was used instead of Solution A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Example 9)
It was carried out in the same manner as in Example 1, except that membrane E was used instead of membrane A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Example 10)
It was carried out in the same manner as in Example 1, except that Solution E was used instead of Solution A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Comparative example 1)
It was carried out in the same manner as in Example 1, except that membrane D was used instead of membrane A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Comparative example 2)
50 L of solution A was processed in the separation step.

The separation step was carried out by a solvent extraction method using a mixer-settler apparatus. First, 50 L of solution A was used as an aqueous phase after adjusting the pH, and bis (2,4,4-trimethylpentyl) phosphinic acid (product name: Cyanex 272 ) was dissolved at 30% by volume as an organic phase, which was brought into contact with an aqueous phase to carry out positive extraction. After that, the organic phase having a high concentration of cobalt ions was brought into contact with an aqueous sulfuric acid solution to back-extract to the aqueous phase.

A recovery step was performed on the aqueous phase obtained by back extraction.

In the recovery process, an insoluble anode made of a titanium plate coated with iridium oxide was used, and a pure metal thin plate of cobalt was used as a cathode, and electricity was applied to deposit cobalt around the cathode.

The recovery rate was calculated from the mass of precipitated cobalt and shown in Table 3.

(Comparative Example 3)
It was carried out in the same manner as in Comparative Example 2 except that Solution B was used instead of Solution A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Comparative Example 4)
It was carried out in the same manner as in Comparative Example 2 except that Solution C was used instead of Solution A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Comparative Example 5)
It was carried out in the same manner as in Comparative Example 2 except that Solution D was used instead of Solution A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

(Comparative Example 6)
It was carried out in the same manner as in Comparative Example 2 except that Solution E was used instead of Solution A.

In the recovery step, the recovery rate was calculated from the mass of cobalt deposited and shown in Table 3.

The present invention provides a salt containing metal species constituting polyvalent rare metal ions such as cobalt and nickel from lithium ion batteries, mobile phones, rare earth magnets, and waste materials, waste liquids, ores, slags, etc. generated in their manufacturing processes, or salts thereof. It can be suitably used as a method for efficiently separating and recovering simple rare metals.

Claims (8)

A method for recovering from a solution X containing polyvalent rare metal ions a salt or simple substance containing a metal species that constitutes a polyvalent rare metal ion, the step of concentrating the polyvalent rare metal ions in the solution X with the following membrane: A recovery method comprising:
(Membrane) A membrane having an isopropyl alcohol removal rate of 40% or more when an isopropyl alcohol aqueous solution having a pH of 6.5 at 25° C. and an operating pressure of 0.5 MPa is permeated. The pH of the solution X is 3 or less, and the isopropyl alcohol removal rate when the membrane is permeated with an isopropyl alcohol aqueous solution having the same pH as the solution X at 25° C. under an operating pressure of 0.5 MPa is The recovery method according to claim 1, characterized in that it is 40% or more. The membrane has an isopropyl alcohol removal rate of 70% or more when an isopropyl alcohol aqueous solution of pH 6.5 at 25 ° C. is permeated at an operating pressure of 0.5 MPa, and / or at an operating pressure of 0.5 MPa 3. The recovery method according to claim 1 or 2, wherein the removal rate of isopropyl alcohol is 70% or more when an isopropyl alcohol aqueous solution at 25°C and pH 3 or less is permeated. The solution X is characterized in that the ratio of the sum of monovalent rare metal ion concentrations (mg/L)/sum of polyvalent rare metal ion concentrations (mg/L) is 0 or more and less than 100. 4. The recovery method according to any one of 3. The polyvalent rare metal ions are cobalt ions, nickel ions, gold ions, palladium ions, platinum ions, neodymium ions, indium ions, dysprosium ions, lanthanum ions, yttrium ions, tantalum ions, niobium ions, tungsten ions, molybdenum ions, The recovery method according to any one of claims 1 to 4, wherein at least one ion of The recovery method according to any one of claims 1 to 5, characterized by including either of the following (a) or (b).
(a) a concentration step of obtaining a non-permeated liquid having a higher polyvalent rare metal ion concentration than the solution X and a permeated liquid having a lower polyvalent rare metal ion concentration than the solution X by the membrane; A separation step of obtaining a liquid having a high concentration of polyvalent rare metal ions to be recovered and a liquid having a low concentration of polyvalent rare metal ions to be recovered from the liquid is performed in this order.
(b) a separation step of obtaining a liquid having a high concentration of polyvalent rare metal ions to be recovered and a liquid having a low concentration of polyvalent rare metal ions to be recovered from the solution X by solvent extraction; to obtain a non-permeated liquid having a high concentration of polyvalent rare metal ions and a permeated liquid having a low concentration of polyvalent rare metal ions in this order. If the total metal ion concentration in the solution X is 50,000 mg/L or less, perform the above (a), and if the total metal ion concentration in the solution X is greater than 50,000 mg/L, perform the above (b). The recovery method according to claim 6. Any one of claims 1 to 7, wherein the membrane contains a crosslinked aromatic polyamide, and the crosslinked aromatic polyamide has at least one structure represented by the following formula (1) or (2): Collection method described in .

(Ar ₁ to Ar ₃ are each independently an optionally substituted aromatic ring having 5 to 14 carbon atoms, and R ₁ is an atom having neither an aromatic ring nor a hetero atom group, X is a hydrogen atom or a carboxy group, and R ₂ to R ₅ are each independently a hydrogen atom or an aliphatic chain having 1 to 10 carbon atoms.)