Valuable material separation method and separation device

Abstract

To provide a method of separating a polyvalent valuable material and a univalent valuable material with a simple method, and a valuable material separation device.SOLUTION: A method of separating a univalent valuable material and a polyvalent valuable material includes: an alkaline treatment step of bringing a material into contact with alkali aqueous solution; and a separation step A of obtaining permeable water a having a ratio (P / Q) of a total sum P of ion concentrations of a univalent valuable material and a total sum Q of ion concentrations of a polyvalent valuable material of equal to or greater than 5 by nano-filtration membrane from valuable material containing alkali aqueous solution containing an ion of the univalent valuable material and an ion of the polyvalent valuable material obtained in the alkali treatment step.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for separating valuable materials from waste materials, waste liquids, ores, slag, etc. generated in batteries and in the manufacturing process thereof. [Background technology]

[0002] In recent years, with the rapid spread of communication devices, hybrid cars, and electric vehicles, the development of lithium secondary batteries has become increasingly important.

[0003] Generally, the components of lithium secondary batteries use various precious resources. For example, the solid electrolyte is an oxide-based solid electrolyte called LAGP (Li 1+x Al x Ge 2-x (PO4)3) and sulfide-based solid electrolytes, such as LGPS, which is a material composed of lithium, germanium, phosphorus, and sulfur, are being developed as promising materials. These materials use rare and valuable materials such as lithium and germanium.

[0004] In recent years, with the growing demand for precious resources and concerns about shortages of these resources, efforts have been made to reuse valuable materials from used lithium secondary batteries and waste materials generated during their manufacturing process. For example, Patent Document 1 discloses a method for producing lithium hydroxide in which lithium ions are recovered from a lithium ion extract extracted from processing materials for lithium secondary batteries using a lithium permselective membrane. Furthermore, Patent Document 2 discloses a method for recovering valuable metals from used lithium ion batteries by performing pretreatment, dissolution in mineral acid, and electrolysis using an ion exchange membrane. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-075619 [Patent Document 2] Japanese Patent Publication No. 2023-051697 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the method described in Patent Document 1 has the problem that only lithium is separated and recovered, and other valuable materials cannot be separated and recovered. In addition, the method described in Patent Document 2 has the problem that it involves multiple steps and requires labor for separation. An object of the present invention is to provide a method for separating polyvalent valuable materials and monovalent valuable materials using a simple technique, and a valuable material separation device. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention comprises the following configuration. [1] A method for separating monovalent and polyvalent valuables, comprising: an alkaline treatment step of contacting a material with an alkaline aqueous solution; and a separation step A of obtaining, from the valuable-containing alkaline aqueous solution containing ions of monovalent valuables and ions of polyvalent valuables obtained in the alkaline treatment step, permeate a having a ratio (P / Q) of 5 or more between the sum of the ion concentrations of the monovalent valuables, P, and the sum of the ion concentrations of the polyvalent valuables, Q, using a nanofiltration membrane. [2] The separation method according to [1] above, wherein the alkaline aqueous solution contains an organic base and / or ammonia. [3] The separation method according to [2] above, wherein the alkaline aqueous solution contains a quaternary ammonium salt. [4] The separation method according to [2] or [3] above, wherein the organic base has a formula weight of 90 or more. [5] The separation method according to any one of [1] to [4] above, wherein the material contains sulfur, and the non-permeated water b obtained in the separation step A contains sulfide ions. [6] The separation method according to [5] above, further comprising the step of adjusting the pH of the non-permeated water b to 8 or less and recovering the hydrogen sulfide generated. [7] The separation method according to any one of [1] to [6] above, wherein the monovalent valuable material contains lithium. [8] The separation method according to any one of [1] to [7] above, wherein the material includes a battery electrolyte. [9] A method for recovering a lithium salt, comprising the separation method according to [7] above.

[10] The separation method according to any one of [1] to [9] above, wherein the difference between the glucose removal rate when a 1000 mg / L aqueous glucose solution at pH 6.5 is passed through the nanofiltration membrane used in the separation step A at an operating pressure of 0.5 MPa, 25°C, and a 1000 mg / L aqueous isopropyl alcohol solution at pH 6.5 is 50% or more, and the glucose removal rate is 70% or more.

[11] The separation method according to [4] above, comprising a separation step B in which permeate water c, in which the ratio (R / Q) of the sum of the organic base concentrations R to the sum of the polyvalent ion concentrations Q, is obtained from non-permeate water b containing organic bases and polyvalent ions using the nanofiltration membrane, is 3 or more.

[12] The separation method according to

[11] above, wherein the organic base has a formula weight of 90 to 210.

[13] The separation method according to

[11] or

[12] above, wherein the difference between the glucose removal rate when a 1000 mg / L aqueous glucose solution at pH 6.5 is passed through the nanofiltration membrane used in the separation step B at an operating pressure of 0.5 MPa, 25°C, and 25°C and the isopropyl alcohol removal rate when a 1000 mg / L aqueous isopropyl alcohol solution at pH 6.5 is passed through the nanofiltration membrane at an operating pressure of 0.5 MPa, 25°C, and 25°C is 60% or more, and the glucose removal rate is 70% or more.

[14] A valuable resource separation device comprising: an alkaline treatment means for contacting a material with an alkaline aqueous solution; and a first nanofiltration means for separating the alkaline aqueous solution containing monovalent valuable resources and polyvalent valuable resources obtained by the alkaline treatment means into a permeate having a ratio (P / Q) of the sum of the ion concentrations of the monovalent valuable resources P to the sum of the ion concentrations of the polyvalent valuable resources Q of 5 or more, and a non-permeate.

[15] The valuable resource separation device according to

[14] above, comprising a pH adjusting device for adjusting the pH of the non-permeated water to 8 or less, and a device for recovering the generated gas.

[16] The valuable resource separation device according to

[14] or

[15] above, further comprising a second nanofiltration means for separating the non-permeated water containing polyvalent ions of valuable resources and organic bases into a permeated water having a ratio (R / Q) of the sum of the organic base concentrations R to the sum of the polyvalent ion concentrations Q of 3 or more, and a non-permeated water, wherein the nanofiltration membrane of at least one nanofiltration membrane element constituting the nanofiltration membrane unit used in the nanofiltration means B has a difference of 60% or more between the glucose removal rate when a 1000 mg / L glucose aqueous solution at 25°C and pH 6.5 is passed through it at an operating pressure of 0.5 MPa and the isopropyl alcohol removal rate when a 1000 mg / L isopropyl alcohol aqueous solution at 25°C and pH 6.5 is passed through it at an operating pressure of 0.5 MPa. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a method for separating monovalent and polyvalent valuables using a simple technique, and an apparatus for separating valuables. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic process diagram showing one embodiment of the valuable resource separation method of the present invention. [Figure 2] FIG. 2 is a schematic process diagram showing one embodiment of the separation step A. [Figure 3] FIG. 2 is a schematic process diagram showing another embodiment of the separation step A. [Figure 4] FIG. 2 is a schematic process diagram showing one embodiment of the separation step B. [Figure 5] 1 is a schematic diagram showing an embodiment of a valuable resource separation device of the present invention, which is equipped with a pH adjustment device and a gas recovery device. [Figure 6] FIG. 2 is a schematic diagram showing one embodiment of a valuables separation device of the present invention, which is equipped with a second nanofiltration membrane unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] The method for separating polyvalent and monovalent valuables of the present invention includes an alkali treatment step in which a material is brought into contact with an alkaline aqueous solution to obtain a solution containing the valuables, and a separation step A in which the material is separated using a nanofiltration membrane into permeate a containing the valuables present as monovalent ions and non-permeate b containing the valuables present as polyvalent ions. Each step is described below.

[0011] (1) Alkali treatment process The method for separating valuable materials of the present invention includes an alkaline treatment step of contacting a material containing monovalent and polyvalent valuable materials with an alkaline aqueous solution to obtain an alkaline aqueous solution containing the valuable materials.

[0012] (1-1) Material The material contains monovalent and polyvalent values.

[0013] "Valuables" refers to elements that are valuable and can be traded without being discarded, such as various metals. In this specification, a monovalent valuable is referred to as a monovalent ion in an aqueous solution, and a polyvalent valuable is referred to as a polyvalent ion in an aqueous solution. Examples of monovalent valuables include lithium and cerium. Examples of polyvalent valuables include beryllium, titanium, chromium, manganese, cobalt, nickel, gallium, germanium, selenium, strontium, zirconium, vanadium, tin, silicon, iron, lead, copper, aluminum, gold, silver, platinum, and polyvalent ions containing rare earth elements. Polyvalent ions may be in the form of either cations or anions. Furthermore, the material may further contain at least one element that does not fall under the category of monovalent or polyvalent valuables. Hereinafter, in this specification, ions of monovalent valuables will be referred to as "monovalent valuable ions," ions of polyvalent valuables will be referred to as "polyvalent valuable ions," and ions of monovalent valuables and polyvalent valuables will be collectively referred to as "valuable ions."

[0014] The material containing valuables is not particularly limited as long as it contains at least one of the monovalent valuables and one of the polyvalent valuables described above. Examples of the material include lithium secondary batteries and waste materials, waste liquids, cleaning solutions, ores, and slags generated in the manufacturing process thereof. The material can also be prepared in a mixed state of multiple types. Since it is possible to prepare a large amount of materials of the same quality, waste materials, waste liquids, or cleaning solutions are preferred as the material.

[0015] In the manufacturing process of a lithium secondary battery, components such as a cathode material, an anode material, a separator, and an electrolyte are formed. Materials used in the separation method of the present invention preferably include, for example, waste materials, waste liquids, or cleaning solutions from the manufacturing process of a lithium secondary battery containing a sulfide-based solid electrolyte. Examples of sulfide-based solid electrolytes include well-known materials. Representative examples include materials containing lithium, sulfur, and phosphorus, such as Li2S-P2S5, and materials containing at least one of halogen, germanium, tin, silicon, and the like.

[0016] (1-2) Alkaline aqueous solution In the alkali treatment step, the material is brought into contact with an alkaline aqueous solution. The alkaline aqueous solution brought into contact with the material may be any aqueous solution that exhibits alkaline properties, and examples thereof include an aqueous solution containing an inorganic base and an aqueous solution containing an organic base. Examples of inorganic bases include sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium silicate, sodium metasilicate, calcium hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, ammonia, and hydroxylamine. Examples of organic bases include primary amines such as ethylamine, diglycolamine, and ethylenediamine; secondary amines such as diethylamine and diethanolamine; tertiary amines such as dimethylethanolamine; quaternary ammonium salts such as tetramethylammonium hydroxide (hereinafter "TMAH"), tetraethylammonium hydroxide (hereinafter "TEAH"), tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, ethyltrimethylammonium hydroxide, benzyltrimethylammonium hydroxide, dimethylbis(2-hydroxyethyl)ammonium hydroxide, and choline; and heterocyclic amines such as pyrrole, piperidine, and 1,8-diazabicyclo[5.4.0]-7-undecene.

[0017] The alkaline aqueous solution used in the separation method of the present invention preferably contains an organic base and / or ammonia. For example, when the monovalent valuables to be separated are other than sodium and potassium, the use of an organic base and / or ammonia can prevent the monovalent alkali metals sodium and potassium from being mixed in, thereby improving the purity of the monovalent valuables to be separated other than sodium and potassium. Furthermore, because organic bases and ammonia are more soluble in water than inorganic bases made of alkaline earth metals such as calcium hydroxide, the aqueous solution can be made more alkaline. This improves the efficiency of alkaline elution of the material in the alkaline treatment step. That is, the concentration of valuable ions in the alkaline aqueous solution containing monovalent and polyvalent valuable ions obtained by contacting the material with the alkaline aqueous solution (hereinafter also referred to as the "leachate") can be increased. Furthermore, the concentration of monovalent valuable ions in the permeate and the concentration of polyvalent valuable ions in the retentate obtained in the separation step A, which will be described later, and the concentration of polyvalent valuable ions in the retentate obtained in the separation step B can be increased.

[0018] The formula weight of the organic base contained in the alkaline aqueous solution is preferably 90 or more. The formula weight of the organic base is more preferably 90 to 260, even more preferably 120 to 230, and particularly preferably 140 to 210. If the formula weight of the organic base is 90 or more, the permeability of the organic base through the first nanofiltration membrane decreases in the separation step A described below, thereby improving the purity of the monovalent valuables in the permeate a. Furthermore, if the formula weight of the organic base is 260 or less, the organic base can be separated into the permeate c in the separation step B described below, and the organic base can be recovered and reused.

[0019] The organic base contained in the alkaline aqueous solution preferably contains a quaternary ammonium salt. Examples of quaternary ammonium salts include TMAH, TEAH, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, ethyltrimethylammonium hydroxide, benzyltrimethylammonium hydroxide, and dimethylbis(2-hydroxyethyl)ammonium hydroxide. By including a quaternary ammonium salt in the alkaline aqueous solution, the efficiency of alkaline elution of the material can be improved. In other words, the concentration of valuable ions in the leachate can be increased, and the concentrations of valuable ions in the permeate and retentate obtained in the separation process can be increased.

[0020] The method for contacting the material with the alkaline aqueous solution includes, for example, immersing the material in the alkaline aqueous solution. Any method may be used as long as it can elute the desired valuable substance.

[0021] The temperature of the alkaline aqueous solution when contacting the material is preferably 10 to 100°C from the viewpoint of the efficiency of eluting valuable substances, and more preferably in the range of 20 to 80°C from the viewpoints of cost and safety.

[0022] The pH of the alkaline aqueous solution is preferably 8 to 14, more preferably 10 to 14, and even more preferably 12 to 13. A pH of 8 or higher can improve the efficiency of alkaline elution of the material. Furthermore, if the material contains sulfur, the generation of hydrogen sulfide, a toxic gas, can be suppressed. On the other hand, a pH of 14 or lower can prevent deterioration of the nanofiltration membranes used in the separation steps A and B described below, and the microfiltration membranes and ultrafiltration membranes used in the pretreatment step described below.

[0023] (2) Pretreatment process The separation method of the present invention may include, between the alkali treatment step and the separation step A, a pretreatment step of treating the alkaline aqueous solution containing valuable ions with a microfiltration membrane and / or an ultrafiltration membrane.

[0024] (2-1) Microfiltration membrane Components in the alkaline aqueous solution containing valuable ions may cause clogging of the nanofiltration membrane due to fouling in the subsequent separation step A. Therefore, it is preferable to filter the alkaline aqueous solution containing valuable ions through a microfiltration membrane before supplying it to the separation step A using the nanofiltration membrane. Preventing clogging of the nanofiltration membrane can suppress a decrease in the amount of water produced and a decrease in the selective separation ability between monovalent valuable ions and polyvalent valuable ions (hereinafter also referred to as "monovalent / polyvalent selective separation ability").

[0025] On the other hand, a small average surface pore size of a microfiltration membrane can lead to foulant accumulation within the pores, causing clogging of the microfiltration membrane surface. When membrane clogging reduces filtration performance, performance can be restored by cleaning with chemicals such as sodium hypochlorite. However, the residual sodium hypochlorite after cleaning comes into contact with the nanofiltration membrane in the subsequent separation process and the reverse osmosis membrane in the concentration process. Prolonged exposure of nanofiltration membranes or reverse osmosis membranes exposed to sodium hypochlorite under strongly acidic conditions significantly deteriorates the separation layer, resulting in a decrease in monovalent / multivalent ion selectivity in the separation process and a decrease in the recovery rate of monovalent ions in the concentration process. Therefore, to maintain excellent foulant rejection, suppress clogging of the microfiltration membrane surface, and reduce the frequency of chemical cleaning, the average surface pore size of the microfiltration membrane used in the pretreatment process is preferably 0.05 to 10 μm, more preferably 0.1 to 5 μm, and even more preferably 0.5 to 1 μm.

[0026] The average surface pore size of a microfiltration membrane can be calculated by analyzing images of the surface of the microfiltration membrane observed with a scanning electron microscope (hereinafter referred to as "SEM"). Specifically, the surface of the microfiltration membrane is observed using an SEM at a magnification of 30,000 to 100,000 times, and the area of 300 randomly selected pores is measured. From the area of each pore, the diameter of each pore, assuming that the pore is circular, is calculated as the pore size, and the average of these is taken as the average surface pore size.

[0027] (2-2) Ultrafiltration membrane Components in the alkaline aqueous solution containing valuable ions may cause clogging of the nanofiltration membrane due to fouling in the subsequent separation step A. Therefore, it is preferable to filter the solution using an ultrafiltration membrane before supplying it to the separation step A using a nanofiltration membrane. In order to exhibit excellent separation properties, the ultrafiltration membrane used in the pretreatment step preferably has an average surface pore size of 3 to 16 nm, more preferably 6 to 14 nm, and even more preferably 8 to 11 nm.

[0028] The average surface pore size of an ultrafiltration membrane can be calculated by observing the surface of the ultrafiltration membrane with an SEM. Specifically, the surface of the ultrafiltration membrane is observed using an SEM at a magnification of 30,000 to 100,000 times, and the area of 300 randomly selected pores is measured. From the area of each pore, the diameter of each pore is calculated assuming that the pore is circular, and the average of these values is taken as the average surface pore size.

[0029] (2-3) Raw water "Raw water" refers to an aqueous solution supplied to a microfiltration membrane and / or an ultrafiltration membrane in the pretreatment step, a nanofiltration membrane in the separation step, and a reverse osmosis membrane in the concentration step. As the raw water in the pretreatment step, the aqueous alkaline solution containing valuable ions obtained in the alkaline treatment step may be used as is, or an aqueous alkaline solution containing valuable ions that has been subjected to other treatments such as pH adjustment may also be used.

[0030] The sum of the monovalent ion concentration P and the polyvalent ion concentration Q in the raw water in the pretreatment step is preferably 500 to 100,000 mg / L, more preferably 1,000 to 70,000 mg / L, and even more preferably 2,000 to 50,000 mg / L. When the ion concentration in the raw water is low, the effect of ion blocking due to charge repulsion becomes significant, reducing the permeability of monovalent ions. On the other hand, when the ion concentration of valuable substances in the raw water is high, solids are generated during filtration, which can damage the membrane surface and reduce separation performance.

[0031] (2-4) Temperature conditions The temperature of the raw water in the pretreatment step is preferably 0 to 100°C, more preferably 5 to 70°C, even more preferably 10 to 60°C, and even more preferably 15 to 40°C. Because the pore size of micro- and ultrafiltration membranes can change with temperature, maintaining the raw water temperature at 100°C or below can suppress changes in pore size to a degree that effectively blocks foulants. On the other hand, maintaining a temperature of 0°C or above can keep the viscosity of the raw water low, allowing the amount of treated water per unit time, i.e., treatment efficiency, to be maintained high. Furthermore, the movement of foulants in the water is promoted, preventing foulants from accumulating inside the pores and suppressing membrane surface clogging.

[0032] (3) Separation process A (3-1) Nanofiltration membrane The method for separating valuable resources of the present invention includes a separation step A in which permeate a is obtained from an alkaline aqueous solution containing monovalent valuable ions and polyvalent valuable ions obtained in the alkali treatment step using a nanofiltration membrane, the permeate a having a ratio (P / Q) of 5 or more between the sum of the monovalent valuable ion concentrations P and the sum of the polyvalent valuable ion concentrations Q. Here, "permeate a" and "non-permeate b" refer to the permeate and non-permeate obtained in the separation step A. The nanofiltration membrane used in the separation step A is not particularly limited as long as it is a nanofiltration membrane that can separate monovalent valuable ions and polyvalent valuable ions. Examples of materials for the nanofiltration membrane include polymeric materials such as cellulose acetate polymers, polyamides, sulfonated polysulfones, polyacrylonitrile, polyesters, polyimides, and vinyl polymers, as well as inorganic materials such as ceramics. Among them, it is preferable to use a nanofiltration membrane in which the difference between the glucose removal rate when a 1000 mg / L glucose aqueous solution at 25 ° C. and pH 6.5 is passed through at an operating pressure of 0.5 MPa and the isopropyl alcohol removal rate when a 1000 mg / L isopropyl alcohol aqueous solution at 25 ° C. and pH 6.5 is passed through at an operating pressure of 0.5 MPa is 40% or more, and the glucose removal rate is 70% or more. Hereinafter, when simply referred to as "glucose removal rate" in this specification, it means the glucose removal rate when a 1000 mg / L glucose aqueous solution at 25 ° C. and pH 6.5 is passed through at an operating pressure of 0.5 MPa, and when referred to as "isopropyl alcohol removal rate", it means the isopropyl alcohol removal rate when a 1000 mg / L isopropyl alcohol aqueous solution at 25 ° C. and pH 6.5 is passed through at an operating pressure of 0.5 MPa.

[0033] From the viewpoint of achieving both high alkali resistance and high selective separation performance, the glucose removal rate of the nanofiltration membrane used in separation step A is more preferably 75% or more, and on the other hand, is preferably 95% or less. Furthermore, from the viewpoint of obtaining high selective separation performance, the difference between the glucose removal rate and the isopropyl alcohol removal rate is more preferably 45% or more, and even more preferably 50% or more.

[0034] When a nanofiltration membrane that satisfies the above requirements is used, it is possible to selectively separate monovalent and polyvalent ions with high efficiency over a long period of time under alkaline conditions, and multi-stage treatment of the permeate due to a decrease in the efficiency of selective separation of the ions is unnecessary or can be reduced, making it a highly efficient process.

[0035] As will be described later, when multiple nanofiltration steps are performed in separation step A, it is sufficient to perform at least one nanofiltration step using a nanofiltration membrane that satisfies the above requirements, and it is preferable to use a nanofiltration membrane that satisfies the above requirements in all of the nanofiltration steps.

[0036] (3-2) Raw water The raw water for the separation step A is the valuable substance-containing alkaline aqueous solution obtained in the alkaline treatment step. The valuable substance-containing alkaline aqueous solution that serves as the raw water may have been subjected to a pretreatment step, pretreatment such as dilution or concentration, or a mixing step described below.

[0037] The sum P of ion concentrations of monovalent valuables in the raw water is preferably 0.5 to 50,000 mg / L, more preferably 5 to 20,000 mg / L. For example, when the monovalent valuable to be separated is lithium, the lithium ion concentration is preferably within the above range. That is, the raw water in the separation step A preferably contains lithium as a monovalent valuable, and the lithium ion concentration in the raw water is preferably 0.5 to 50,000 mg / L.

[0038] Furthermore, the sum Q of the ion concentrations of polyvalent valuables in the raw water is preferably 0.5 to 100,000 mg / L. If the sum Q of the ion concentrations of polyvalent valuables in the raw water is 0.5 mg / L or more, it is possible to recover a useful amount of polyvalent valuables. If the sum Q of the ion concentrations of polyvalent valuables is 100,000 mg / L or less, it is easy to separate them from monovalent valuables.

[0039] The raw water preferably contains at least one polyvalent valuable element selected from the group consisting of germanium, tin, and silicon.

[0040] In addition, raw water contains hydrogen sulfide ions (hereinafter referred to as "HS") as a sulfur source. - "), sulfide ions (hereinafter referred to as "S 2- When the raw water contains hydrogen sulfide, the pH of the raw water is preferably 8 or higher, and more preferably 10 or higher, in order to prevent the generation of hydrogen sulfide, a toxic gas. To adjust the pH of the raw water, an inorganic base, an organic base, or an aqueous solution of these may be added. The temperature of the raw water may also be adjusted as necessary.

[0041] (3-3) Permeated water a, non-permeated water b The separation step A is a step in which the difference in permeability of the nanofiltration membrane between monovalent and polyvalent ions is utilized to separate the monovalent ions from the polyvalent ions, thereby obtaining permeated water a having a ratio (hereinafter also referred to as "P / Q") of 5 or more between the sum of the monovalent ion concentrations P and the sum of the polyvalent ion concentrations Q. In other words, the P / Q of permeated water a is greater than the P / Q of the raw water, which is an alkaline aqueous solution containing valuables. On the other hand, the P / Q of non-permeated water b is smaller than the P / Q of the raw water.

[0042] The P / Q of the permeate a obtained in separation step A is preferably 9 or more, and it is more preferable to obtain a permeate a with a P / Q of 15 or more. In separation step A, if the P / Q of the permeate obtained in a single separation using a nanofiltration membrane (hereinafter also referred to as the "nanofiltration step") is less than 5, the nanofiltration step may be performed multiple times. When the nanofiltration step is performed multiple times, the permeate obtained in the final nanofiltration step or a mixture of the permeates obtained in each nanofiltration step is referred to as permeate a. In other words, permeate a1 or non-permeate b1 obtained in nanofiltration step A1 is used as raw water to perform nanofiltration step A2, and the obtained permeate a2 can be mixed as necessary to obtain permeate a with a P / Q of 5 or more. Furthermore, a circulation step may be provided in which the non-permeate b obtained in separation step A is mixed with the raw water for separation step A and separation step A is performed again, and similarly, a circulation step may be provided in each nanofiltration step.

[0043] The mass of polyvalent ions is calculated as the sum of the ion-equivalent masses, for example, of germanium ions. The mass of monovalent ions is calculated as the sum of the ion-equivalent masses, for example, of lithium ions and cesium ions. Some elements may exist in aqueous solution as polyatomic ions rather than monoatomic ions, but the equivalent mass is the mass assuming they exist as monoatomic ions. The ion-equivalent masses of polyvalent and monovalent ions can be determined by quantifying the concentration (mg / L) of each ion in the aqueous solution to be measured, for example, using a Hitachi P-4010 ICP (inductively coupled plasma atomic emission spectrometry) instrument.

[0044] The purity of the monovalent valuables in the permeate a obtained in the separation step A is preferably 20% or more, more preferably 25% or more, and even more preferably 30% or more. The "purity of the monovalent valuables" is calculated by the following formula (1). Purity (%) of monovalent valuables = (total ion concentration of monovalent valuables in aqueous solution (mg / L) / total ion concentration of aqueous solution (mg / L)) × 100 Equation (1).

[0045] If the purity of the monovalent valuables in the permeate a is high, impurities can be reduced when the permeate a is subsequently refined and recovered as a resource, making it applicable to a variety of uses.

[0046] It is also preferable that the recovery rate of the monovalent valuable material is high in the separation step A. The recovery rate of the monovalent valuable material is calculated by the following formula (2). Recovery rate of monovalent valuables (%) = {total ion concentration of monovalent valuables in the permeate recovered in the separation process (g / L) × amount of permeate recovered in the separation process (L)} / amount of monovalent valuables contained in the material contacted in the alkaline treatment process (g) Equation (2).

[0047] The higher the recovery rate of the monovalent valuable materials, the more efficiently the valuable materials can be reused. The recovery rate of the monovalent valuable materials is preferably 35% or more, more preferably 50% or more, even more preferably 55% or more, and particularly preferably 60% or more.

[0048] If organic bases or inorganic bases not containing alkali metals or alkaline earth metals (e.g., ammonia, hydroxylamine) remain in the permeate a, they can be removed by known methods. For example, removal methods using ion exchange resins or adsorbents can be used. As the ion exchange resin, it is preferable to use a cation exchange resin. As the adsorbent, for example, porous materials such as activated carbon, silica-based materials, and ceramics can be used. By removing the organic bases from the permeate a, the purity can be improved when recovering monovalent valuables from the permeate a.

[0049] (3-4) Pressure The operating pressure (pressure on the raw water side) in the separation step A is preferably 0.1 to 8 MPa. Since the higher the pressure, the higher the membrane permeation rate, a pressure of 0.1 MPa or higher can achieve a practical membrane permeation rate. Furthermore, a pressure of 8 MPa or lower can minimize damage to the nanofiltration membrane. Furthermore, the operating pressure is more preferably 0.5 to 6 MPa.

[0050] When the nanofiltration step is carried out multiple times in the separation step A, the operating pressure in each nanofiltration step is preferably within the above range.

[0051] (3-5) Number of times In the separation step A, the nanofiltration step may be performed multiple times. When the nanofiltration step is performed twice, for example, a nanofiltration step A2 may be provided in which permeate a1 obtained in the nanofiltration step A1 is used as raw water to obtain permeate a2 and non-permeate b2 (FIG. 2). In FIG. 2, permeate a2 becomes permeate a in the separation step A.

[0052] The separation step A may further include a nanofiltration step A3 in which the non-permeated water b1 obtained in the nanofiltration step A1 is used as raw water to obtain permeated water a3 and non-permeated water b3, and may further include a nanofiltration step A4 in which the permeated water a3 is separated (FIG. 3). In FIG. 3, the permeated water a2 and the permeated water a4 are mixed to produce the permeated water a of the separation step A.

[0053] The nanofiltration step (e.g., nanofiltration steps A2, A3, and A4) in which the permeate and retentate are separated using a nanofiltration membrane may be combined with a step of diluting the permeate and retentate, which is commonly known as diafiltration. The solution used in the dilution step is not particularly limited and may be, for example, pure water or an alkaline aqueous solution.

[0054] When the nanofiltration step is performed multiple times in the separation step A, the resulting permeates can be mixed or used separately in the subsequent concentration step. The non-permeates can also be mixed together or used separately to recover polyvalent valuables, or they can be mixed with the valuable-containing aqueous alkaline solution obtained in the alkaline treatment step.

[0055] (4) Separation process B The method for separating valuable materials of the present invention preferably includes a separation step B in which permeated water c, in which the ratio (R / Q) of the total concentration of organic bases R to the total concentration of polyvalent valuable ions Q is 3 or more, is obtained from non-permeated water b containing organic bases and polyvalent valuable ions obtained in separation step A (FIG. 4). Here, "permeated water c" and "non-permeated water d" refer to the permeated water and non-permeated water obtained in separation step B.

[0056] (4-1) Nanofiltration membrane The nanofiltration membrane used in the separation step B is not particularly limited as long as it can selectively separate an organic base from a polyvalent valuable substance. In particular, it is preferable that the difference between the glucose removal rate and the isopropyl alcohol removal rate is 60% or more, and the glucose removal rate is 70% or more.

[0057] By using a nanofiltration membrane that satisfies the above-mentioned requirements, it is possible to selectively separate the organic base used as the alkaline component from the polyvalent ions, and the organic base used as the alkaline component can be recovered and reused.Furthermore, impurities can be reduced when the polyvalent ions are later purified and recovered as resources.

[0058] (4-2) Raw water As described above, the raw water for the separation step B is the non-permeated water b obtained in the separation step A, and examples thereof include the non-permeated water b1, the non-permeated water b3, and a mixed solution thereof. The aqueous solution may be subjected to pretreatment such as dilution or concentration, or to a mixing step described below.

[0059] The total concentration R of the organic base in the raw water in the separation step B is preferably 100 to 100,000 mg / L, and more preferably 1,000 to 10,000 mg / L. If the total concentration R of the organic base is 100 mg / L or more, it is possible to recover a useful amount of organic base. Furthermore, if the total concentration R of the organic base is 100,000 mg / L or less, separation from polyvalent valent ions is easy. As the organic base, the compounds described in (1-2) Alkaline aqueous solution in the above (1) Alkaline treatment step can be used. The concentration of the organic base can be measured by ion chromatography or the like.

[0060] The sum Q of ion concentrations of polyvalent valuables in the raw water of the separation step B is preferably 0.5 to 100,000 mg / L. If the sum Q of ion concentrations of polyvalent valuables is 0.5 mg / L or more, it is possible to recover a useful amount of polyvalent valuables. Furthermore, if the sum Q of ion concentrations of polyvalent valuables is 100,000 mg / L or less, separation from the organic base is easy.

[0061] The raw water preferably contains at least one polyvalent valuable element selected from the group consisting of germanium, tin, and silicon.

[0062] (4-3) Permeated water c, non-permeated water d In the separation step B, the organic base and the polyvalent ion are separated by utilizing the difference in permeability of the nanofiltration membrane between the organic base and the polyvalent ion. This is the step to obtain permeate c, in which the ratio (R / Q) of the sum of the organic base concentrations R to the sum of the polyvalent ion concentrations Q is 3 or more. In other words, the R / Q of permeate c is greater than the R / Q of the raw water. On the other hand, the R / Q of retentate d is smaller than the R / Q of the raw water.

[0063] The R / Q of the permeate c obtained in the separation step B is preferably 4 or more, and more preferably 5 or more.

[0064] The formula weight of the organic base contained in the non-permeated water b is preferably 90 to 210. When the formula weight of the organic base is 210 or less, the permeability of the organic base through the second nanofiltration membrane is improved, and the R / Q of the permeated water c is also improved. On the other hand, when the formula weight of the organic base is 90 or more, the concentration of the organic base in the non-permeated water b can be increased.

[0065] The permeate c recovered in the separation step B can be reused as an aqueous alkaline solution in the alkaline treatment step. If necessary, water, an inorganic base, or an organic base may be added.

[0066] The organic base purity of the permeate c obtained in the separation step B is preferably 30% or more, and more preferably 50% or more. The higher the organic base purity, the more the elution efficiency in the alkali treatment step can be improved. The "organic base purity" is calculated using the following formula (3). Organic base purity (%) = (total concentration of organic base in aqueous solution (mg / L)) / (total ion concentration in aqueous solution (mg / L)) × 100 Equation (3).

[0067] In the separation step B, if a permeate with an R / Q of 3 or more cannot be obtained in a single nanofiltration step, the nanofiltration step may be performed multiple times. When the nanofiltration step is performed multiple times, the permeate obtained in the final nanofiltration step or a mixture of the permeates obtained in each nanofiltration step is referred to as permeate c. In other words, permeate c1 or non-permeate d1 obtained in nanofiltration step B1 is used as raw water, and nanofiltration step B2 is further performed, and the resulting permeate c2 is mixed as necessary to obtain permeate c with an R / Q of 3 or more.

[0068] The recovery rate of the organic base is preferably 15% or more, more preferably 25% or more, and even more preferably 30% or more. The higher the recovery rate of the organic base, the greater the amount of organic base that can be reused, and the amount of organic base consumed in the alkaline treatment step can be reduced. The "recovery rate of the organic base" is calculated using the following formula (4). Recovery rate of organic base (%) = {total concentration of organic base in recovered permeate c (g / L) × volume of recovered permeate c (L)} / amount of organic base contained in the alkaline aqueous solution used to soak the material (g) × 100 Equation (4).

[0069] (4-4) Pressure The preferred range of the operating pressure in the separation step B is the same as that described in (2-4) of the separation step A.

[0070] (4-5) Number of times The nanofiltration step may be carried out multiple times in the separation step B. An example of carrying out the nanofiltration step multiple times is the same as that described in (3-5) of the separation step A.

[0071] (5) Hydrogen sulfide recovery process In the method for separating valuable materials of the present invention, the material contains sulfur, and the non-permeated water b obtained in the separation step A contains S 2- and / or H.S. - When the material contains hydrogen sulfide, it is preferable to include a step of adjusting the pH of at least a portion of the non-permeated water b obtained in the separation step A, the permeated water c obtained in the separation step B, and the non-permeated water d to 8 or less, and recovering hydrogen sulfide. 2- and / or H.S. - Therefore, S 2- and / or H.S. - By lowering the pH of the non-permeated water containing hydrogen sulfide, hydrogen sulfide can be generated as a gas and recovered from the system. The hydrogen sulfide recovery process includes at least the following steps: (5-1) pH adjustment step; and (5-2) gas recovery step.

[0072] (5-1) pH adjustment process In the pH adjustment step, hydrogen sulfide is generated by lowering the pH of the non-permeated water. From the viewpoint of increasing the amount of hydrogen sulfide generated, the pH of the non-permeated water is preferably adjusted to 8 or less, more preferably 6 or less. To adjust the pH, a common acid such as hydrochloric acid or sulfuric acid may be added. Furthermore, the temperature of the non-permeated water may be adjusted as necessary.

[0073] (5-2) Gas recovery process In the gas recovery step, the generated hydrogen sulfide is recovered from the system. Known methods can be used for recovery. Examples include a method of trapping in liquid, a method using a scrubber device, and a method using an exhaust gas treatment device. Among these, the method using a scrubber device is preferred because it allows for a large amount of treatment. The recovered hydrogen sulfide can be used as a resource. For example, when it is reacted with an aqueous sodium hydroxide solution and recovered as a solution, it can be used as sodium hydrogen sulfide or sodium sulfide. The gas recovery step may be performed simultaneously with the pH adjustment step or after the pH adjustment step.

[0074] (6) Valuable resource recovery process In the valuable resource recovery step, for example, monovalent valuable ions are recovered as compounds from the permeated water a obtained in the separation step A, and polyvalent valuable ions are recovered as compounds from the non-permeated water b obtained in the separation step A or the non-permeated water d obtained in the separation step B. When recovering valuable resources, it is preferable to concentrate the permeated water or non-permeated water in advance to increase the concentration of the valuable ions to be recovered. Methods for concentrating the permeated water or non-permeated water include, for example, a method of concentrating using a reverse osmosis membrane and a method of concentrating by heating.

[0075] As a method for recovering monovalent valuable ions from the permeate a obtained in the separation step A, for example, known methods can be used, such as a method for recovering them as hydroxides by crystallization or a method for recovering them as carbonates by adding sodium carbonate or blowing in carbon dioxide gas. In particular, when the monovalent valuable contained in the permeate a is lithium, lithium can be recovered as a lithium salt in the recovery step. Specifically, lithium can be recovered as lithium hydroxide by crystallization while the pH is high, and lithium carbonate can be recovered by adding sodium carbonate or blowing in carbon dioxide gas.

[0076] Examples of a method for recovering polyvalent ions from the non-permeated water b obtained in the separation step A or the non-permeated water d obtained in the separation step B include a method of forming a precipitate by adjusting the pH and recovering the ions.

[0077] (7) Nanofiltration membrane Preferred forms of the nanofiltration membrane used in separation step A and separation step B are described below. As described above, the nanofiltration membrane used in separation step A may be any membrane capable of separating monovalent ions and polyvalent ions, while the nanofiltration membrane used in separation step B is not particularly limited as long as it can separate organic bases and polyvalent ions.

[0078] The nanofiltration membrane according to this embodiment is preferably a composite semipermeable membrane obtained by coating a porous support membrane with a separation functional layer made of a crosslinked polyamide obtained by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide.

[0079] (7-1) Support membrane The nanofiltration membrane according to this embodiment has a support membrane. The support membrane comprises a substrate and a porous support layer. However, the present invention is not limited to this configuration. For example, the support membrane may be composed of only a porous support layer without a substrate.

[0080] (7-1-1) Base material Examples of the substrate include polyester polymers, polyphenylene sulfide polymers, polyamide polymers, polyolefin polymers, and mixtures or copolymers thereof. Among these, fabrics of polyester polymers or polyphenylene sulfide polymers, which have high mechanical and thermal stability, are particularly preferred. As the form of the fabric, long-fiber nonwoven fabrics, short-fiber nonwoven fabrics, and even woven and knitted fabrics can be preferably used.

[0081] (7-1-2) Porous support layer The porous support layer according to this embodiment does not substantially have the ability to separate ions, etc., but serves to provide strength to the separation functional layer, which does have the ability to separate ions, etc. The size and distribution of the pores in the porous support layer are not particularly limited. For example, a porous support layer having uniform fine pores, or pores that gradually increase in size from the surface on which the separation functional layer is formed to the other surface, and in which the size of the fine pores on the surface on which the separation functional layer is formed is 0.1 to 100 nm, is preferred. The material used for the support layer and its shape are not particularly limited.

[0082] The porous support layer may be made of a homopolymer or copolymer, such as polysulfone, polyethersulfone, polyamide, polyester, cellulose-based polymer, vinyl polymer, polyphenylene sulfide, polyphenylene sulfide sulfone, polyphenylene sulfone, or polyphenylene oxide, either singly or in combination. Cellulose-based polymers include cellulose acetate and cellulose nitrate, and vinyl polymers include polyethylene, polypropylene, polyvinyl chloride, and polyacrylonitrile.

[0083] Among these, 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, and polyphenylene sulfone are more preferred. Furthermore, among these materials, polysulfone is generally used because of its high chemical, mechanical, and thermal stability and ease of molding.

[0084] The polysulfone preferably has a mass average molecular weight (Mw) of 10,000 to 200,000, more preferably 15,000 to 100,000, as measured by gel permeation chromatography (GPC) using N-methylpyrrolidone as a solvent and polystyrene as a standard.

[0085] When the Mw of the polysulfone is 10,000 or more, the porous support layer can have favorable mechanical strength and heat resistance. When the Mw is 200,000 or less, the viscosity of the solution falls within an appropriate range, and good moldability can be achieved.

[0086] The thicknesses of the substrate and the porous support layer affect the strength of the composite semipermeable membrane and the packing density when it is made into an element. To obtain sufficient mechanical strength and packing density, the total thickness of the substrate and the porous support layer is preferably 30 to 300 μm, more preferably 100 to 220 μm. The thickness of the porous support layer is preferably 20 to 100 μm. In this specification, unless otherwise specified, thickness refers to the average value. Here, the average value represents the arithmetic mean value. In other words, the thickness of the substrate and the porous support layer can be determined by calculating the average value of the thickness at 20 points measured at 20 μm intervals in a direction perpendicular to the thickness direction (in the plane direction of the membrane) during cross-sectional observation.

[0087] (7-1-3) Support film formation process The support membrane forming process can also be referred to as a porous support layer forming process, and includes the steps of applying a polymer solution to a substrate and immersing the substrate with the applied solution in a coagulation bath to coagulate the polymer.

[0088] In the step of applying the polymer solution to the substrate, the polymer solution is prepared by dissolving the polymer, which is a component of the porous support layer, in a good solvent for the polymer.

[0089] When polysulfone is used as the polymer, the temperature of the polymer solution during application is preferably in the range of 10 to 60°C. If the temperature of the polymer solution is within this range, the polymer does not precipitate, and the polymer solution is sufficiently impregnated into the spaces between the fibers of the substrate and then solidified. As a result, a porous support layer that is firmly bonded to the substrate due to the anchor effect can be obtained. The preferred temperature range of the polymer solution can be adjusted as appropriate depending on the type of polymer used, the desired solution viscosity, etc.

[0090] After the polymer solution is applied to the substrate, the time until the substrate is immersed in the coagulation bath is preferably in the range of 0.1 to 5 seconds. If the time until the substrate is immersed in the coagulation bath is within this range, the organic solvent solution containing the polymer is sufficiently impregnated into the spaces between the fibers of the substrate and then solidified. The preferred range of the time until the substrate is immersed in the coagulation bath can be appropriately adjusted depending on the type of polymer solution used, the desired solution viscosity, etc.

[0091] Water is usually used as the coagulation bath, but any solution that does not dissolve the polymers that are components of the porous support layer will suffice. The temperature of the coagulation bath is preferably -20 to 100°C. The temperature of the coagulation bath is more preferably 10 to 50°C. If the temperature of the coagulation bath is 100°C or less, vibration of the coagulation bath surface due to thermal motion can be suppressed, and the smoothness of the membrane surface after membrane formation can be maintained. Furthermore, if the temperature is -20°C or higher, the coagulation rate can be maintained, improving membrane formability.

[0092] Next, the support membrane thus obtained may be washed with hot water to remove any remaining solvent in the membrane. The temperature of the hot water used here is preferably 40 to 100°C, more preferably 60 to 95°C. If the washing temperature is below the upper limit, the shrinkage of the support membrane will not be too great, and a decrease in water permeability can be suppressed. Furthermore, if the washing temperature is 40°C or higher, a high washing effect can be obtained.

[0093] (7-2) Separation functional layer Materials for the separation functional layer of the nanofiltration membrane according to this embodiment include polymeric materials such as cellulose acetate polymers, polyamides, sulfonated polysulfones, polyacrylonitrile, polyesters, polyimides, and vinyl polymers. The membrane is not limited to being composed of only one of these materials, and may also comprise multiple materials. The membrane structure may also be an asymmetric membrane having a dense layer on at least one side of the membrane, with gradually increasing pore sizes from the dense layer toward the interior of the membrane or toward the other side, or a composite membrane having a very thin functional layer made of a different material on the dense layer of the asymmetric membrane. Examples of composite membranes that can be used include the composite membrane described in JP 62-201606 A, in which a nanofilter made of a polyamide functional layer is formed on a support membrane made of polysulfone as the membrane material.

[0094] Among these, composite semipermeable membranes with a separation functional layer made of polyamide, which has excellent potential for combining high pressure resistance, high water permeability, and high solute removal performance, are preferred. To maintain durability against operating pressure, high water permeability, and blocking performance, a structure in which a polyamide is used as a separation functional layer and is supported by a support made of a porous membrane or nonwoven fabric is suitable. Furthermore, as a separation functional layer made of polyamide, a composite semipermeable membrane having a support made of a functional layer of crosslinked polyamide obtained by a polycondensation reaction of a polyfunctional aliphatic amine and a polyfunctional acid halide is suitable.

[0095] Compared with polyamide membranes made of unsubstituted piperazine, which are known as common nanofiltration membranes, polyamide membranes made of substituted piperazine have higher resistance to chemicals and can suppress a decrease in ion selectivity when treating acidic aqueous solutions, and are therefore preferably used for long-term operation for this purpose.

[0096] In particular, the polyamide separation functional layer in the nanofiltration membrane according to this embodiment preferably contains a crosslinked polyamide having a structure derived from a polyfunctional aliphatic amine (piperazine-based compound) represented by the following general formula (I).

[0097] In the method for separating valuables according to this embodiment, the nanofiltration membrane preferably comprises a substrate, a porous support layer on the substrate, and a separation functional layer on the porous support layer, and the separation functional layer preferably contains a crosslinked polyamide having a structure derived from a polyfunctional aliphatic amine represented by the following general formula (I):

[0098] [ka]

[0099] R in general formula (I) 1 and R 2 are each independently an alkyl group having 1 to 6 carbon atoms, a phenyl group, a benzyl group, COOR 5 ,CONHR 5 , CON(R 5 )2 OR 5 represents R 5 represents hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group. 3 and R 4 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a benzyl group, COOR 6 ,CONHR 6 , CON(R 6 )2 OR 6 represents R 6 represents hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group. 1 ~R 6Examples of the alkyl group having 1 to 6 carbon atoms in R include linear or branched methyl, ethyl, propyl, butyl, pentyl, and hexyl, as well as cyclic cyclopropyl, cyclobutyl, cyclopentyl, and cyclohexyl. 1 and R 2 are each independently preferably an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group, and particularly preferably an alkyl group having 3 to 6 carbon atoms, a phenyl group, or a benzyl group. 3 and R 4 are each independently preferably hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group. By introducing the above substituents into the piperazine structure, the steric hindrance near the amide group and the pore size distribution (intermolecular gap) of the polyamide crosslinked structure can be suitably controlled, making it possible to improve durability against acids and alkalis while maintaining water permeability and selective separation properties. If the number of carbon atoms in the substituents is too large, the crosslinking reaction of the polyamide becomes difficult to proceed due to steric hindrance, resulting in reduced selective separation properties and durability against acids and alkalis. The piperazine compounds represented by general formula (I) may be used alone or in combination of two or more types.

[0100] Specifically, it preferably contains a crosslinked polyamide obtained by interfacial polymerization of a piperazine compound represented by general formula (I) with a divalent or higher polyfunctional acid halide. The separating functional layer preferably contains 90 mass % or more of this crosslinked polyamide, and more preferably consists of only this crosslinked polyamide.

[0101] The nanofiltration membrane of this embodiment has a separation functional layer containing a polymer of a piperazine compound represented by general formula (I) and a divalent or higher polyfunctional acid halide. The substituents near the amide groups of the piperazine rings widen the gaps between the crosslinked polyamide chains, resulting in a membrane with an appropriate pore size distribution. Furthermore, steric hindrance occurs near the amide groups, suppressing hydrolysis of the amide groups by acids or alkalis, improving durability. This allows for long-term operation and is advantageous in that it allows for a highly efficient process, eliminating or reducing the need for multi-stage treatment of permeate and non-permeate due to reduced ion selectivity.

[0102] The term "polyfunctional acid halide" refers to an acid halide having two or more carbonyl halide groups per molecule, and is not particularly limited as long as it can give a polyamide upon reaction with a piperazine compound. Examples of polyfunctional acid halides that can be used include halides of oxalic acid, malonic acid, maleic acid, fumaric acid, glutaric acid, 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, 1,4-benzenedicarboxylic acid, 1,3,5-benzenetrisulfonic acid, and 1,3,6-naphthalenetrisulfonic acid. Among acid halides, acid chlorides are preferred, and in particular, from the standpoints of economy, availability, ease of handling, ease of reactivity, and the like, trimesoyl chloride, which is an acid halide of 1,3,5-benzenetricarboxylic acid, isophthaloyl chloride, which is an acid halide of 1,3-benzenedicarboxylic acid, terephthaloyl chloride, which is an acid halide of 1,4-benzenedicarboxylic acid, 1,3,5-benzenetrisulfonic acid chloride, which is an acid halide of 1,3,5-benzenetrisulfonic acid, and 1,3,6-naphthalenetrisulfonic acid chloride, which is an acid halide of 1,3,6-naphthalenetrisulfonic acid, are preferred. The above polyfunctional acid halides may be used alone or in combination of two or more. However, by mixing the trifunctional trimesic acid chloride, 1,3,5-benzenetrisulfonic acid chloride, or 1,3,6-naphthalenetrisulfonic acid chloride with either the difunctional isophthalic acid chloride or terephthalic acid chloride, the intermolecular gaps in the crosslinked polyamide structure are enlarged, enabling the production of membranes with a uniform pore size distribution over a wide range. The molar ratio of the trifunctional acid chloride to the difunctional acid chloride is preferably 1:20 to 50:1, more preferably 1:1 to 20:1.

[0103] The separation functional layer of the nanofiltration membrane according to this embodiment has a thin film of crosslinked polyamide, and this thin film preferably forms a pleated structure consisting of repeated convex and concave portions. The pleated structure with convex and concave portions increases the surface area of the separation functional layer, resulting in high water permeability and excellent alkali resistance, and enabling the selective monovalent / polyvalent separation to be maintained under alkaline conditions for an extended period of time. The presence or absence of a pleated structure and the specific surface area can be measured using an electron microscope or molecular force microscopy.

[0104] In the method for separating valuables according to this embodiment, the nanofiltration membrane preferably comprises a substrate, a porous support layer on the substrate, and a separation functional layer on the porous support layer, the separation functional layer contains a crosslinked aromatic polyamide, and the crosslinked aromatic polyamide preferably has a structure represented by the following general formula (II):

[0105] [ka]

[0106] R in general formula (II) 1 ~R 4 represents R in the above general formula (I). 1 ~R 4 It is synonymous with R. 7 is a hydrogen atom or COR 8 and R 8 is an aliphatic chain or aliphatic ring whose constituent elements are only carbon and hydrogen atoms, and Ar 9 is an aromatic ring having 6 to 14 carbon atoms, which may or may not have a substituent.

[0107] The crosslinked polyamide according to this embodiment is preferably a crosslinked semi-aromatic polyamide, and more preferably has a structure represented by the following general formula (II): Since the terminal amino groups of the crosslinked polyamide are positively charged under acidic conditions, which leads to a decrease in the selective separation ability of ions due to swelling of the membrane, by having the structure represented by the following general formula (II), it is possible to stably maintain high selective separation ability for monovalent and polyvalent valuables for a long period of time even under alkaline conditions.

[0108] (7-3) Manufacturing method of nanofiltration membrane The process for forming the separation functional layer constituting the nanofiltration membrane according to this embodiment will now be described. As an example of a method for producing a nanofiltration membrane containing a crosslinked polyamide having a structure derived from a piperazine compound represented by general formula (I), the process for forming the separation functional layer will be described in this section, which includes the following polymerization and modification steps.

[0109] In the process of forming the separation function layer, an aqueous solution containing a piperazine-based compound, which is a polyfunctional aliphatic amine, and an organic solvent solution containing a polyfunctional acid halide are used to perform interfacial polycondensation on the surface of the porous support layer, thereby forming a polyamide separation function layer.

[0110] The organic solvent that dissolves the polyfunctional acid halide must be immiscible with water, not destroy the support film, and not inhibit the crosslinked polyamide production reaction. The solubility parameter (hereinafter referred to as "SP value") must be 15.2 (MPa). 1 / 2 Use an organic solvent with an octanol / water partition coefficient (logP) of 3.2 or more. SP value is 15.2 (MPa). 1 / 2 By satisfying the above conditions and by ensuring that the logP is 3.2 or greater, the distribution and diffusion of the polyfunctional aliphatic amine during interfacial polycondensation are optimized, and the amount of functional groups can be increased.Typical examples that are preferably used include octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, hexadecane, cyclooctane, ethylcyclohexane, 1-octene, 1-decene, and the like, alone or in combination.

[0111] The aqueous solution containing the piperazine compound may contain a surfactant. Examples include sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyldiphenyletherdisulfonate, styrenebis(sodiumnaphthalenesulfonate), and sodium polyoxyethylene alkyl ether sulfate. The inclusion of a surfactant allows the surface of the porous support layer to be uniformly coated with the aqueous solution of the piperazine compound, resulting in the uniform formation of a separation functional layer, which stabilizes membrane performance and improves adhesion between the separation functional layer and the porous support layer.

[0112] The aqueous solution containing the piperazine compound may contain alcohol. Examples include ethanol, 1-propanol, 2-propanol, and butanol. The inclusion of alcohol provides the same effects as the surfactants described above.

[0113] The aqueous solution containing the piperazine compound may contain an alkaline compound. Examples include sodium hydroxide, trisodium phosphate, and triethylamine. The inclusion of an alkaline compound can remove hydrogen halide generated in the interfacial polycondensation reaction, suppress a decrease in the reactivity of the piperazine compound, promote the polyamidation reaction, and improve the selective separation property as well as durability against acids and alkalis.

[0114] The aqueous solution containing a piperazine compound and the organic solvent solution containing a polyfunctional acid halide may each contain compounds such as an acylation catalyst, a polar solvent, an acid scavenger, and an antioxidant, as necessary.

[0115] To carry out interfacial polycondensation on a porous support layer, the surface of the porous support layer is first coated with an aqueous solution containing a piperazine compound represented by general formula (I). The method for coating the surface of the porous support layer with the aqueous solution containing the piperazine compound can be any method that uniformly and continuously coats the surface of the porous support layer with the aqueous solution, and includes known coating methods such as coating the surface of the porous support layer with the aqueous solution and immersing a support membrane in the aqueous solution. The contact time between the porous support layer and the aqueous solution containing the piperazine compound is preferably 5 seconds to 10 minutes, and more preferably 10 seconds to 2 minutes.

[0116] Next, it is preferable to remove the excess applied aqueous solution by a draining step. For example, the method of draining the solution may be a method of holding the membrane surface vertically and allowing the solution to flow down naturally. After draining the solution, the membrane surface may be dried to remove all or part of the water in the aqueous solution.

[0117] The concentration of the piperazine compound in the aqueous solution is preferably 0.5 to 5.0% by mass, more preferably 1.0 to 4.0% by mass, and even more preferably 2.0 to 3.0% by mass. By setting the concentration to 0.5% by mass or more, a uniform separation functional layer is easily formed, and a membrane with sufficient selective separation properties and durability against acids and alkalis is obtained. Furthermore, by setting the concentration to 5.0% by mass or less, the separation functional layer does not become too thick, and a decrease in water permeability can be suppressed.

[0118] Then, the organic solvent solution containing the polyfunctional acid halide is applied to the porous support layer coated with the aqueous solution containing the piperazine compound, preferably at a temperature of 5 to 45°C.

[0119] When trimesoyl chloride is contained as the polyfunctional acid halide, the concentration of trimesoyl chloride in the organic solvent solution is preferably 0.05 to 0.70% by mass, more preferably 0.08 to 0.3% by mass. Within this range, sufficient water permeability, selective separation performance, and durability against acids and alkalis can be obtained. When other trifunctional acid chlorides or difunctional acid chlorides are used, the molar concentrations of the acid chlorides are adjusted to be approximately the same as those of the above-mentioned trimesoyl chloride in terms of molecular weight ratio.

[0120] As described above, the polyfunctional aliphatic amine and the polyfunctional acid halide are brought into contact with each other to cause interfacial polymerization. The interfacial polymerization is preferably carried out at a temperature of 30°C or higher, more preferably at a temperature of 50°C or higher. Furthermore, the interfacial polymerization is preferably carried out at a temperature of 120°C or lower. By carrying out the interfacial polymerization at 30°C or higher, the crosslinking of the polyamide is enhanced in the interfacial polymerization reaction, thereby increasing the removal rate of polyvalent ions. Furthermore, by carrying out the interfacial polymerization at 120°C or lower, excessive drying of the separation functional layer and the porous support layer can be prevented, ensuring practical water permeability.

[0121] The time for carrying out the interfacial polymerization is preferably from 0.1 seconds to 3 minutes, more preferably from 0.1 seconds to 1 minute.

[0122] Next, the organic solvent solution after the reaction is preferably removed by a draining process. The organic solvent can be removed, for example, by holding the membrane vertically and allowing the excess organic solvent to flow down by gravity, by drying the organic solvent by blowing air onto the membrane with a fan, or by removing the excess organic solvent with a water-air mixture. Removal using a water-air mixture is particularly preferred. When a water-air mixture is used, the separation functional layer contains water, causing it to swell and increase its water permeability. In the case of gravity flow, the vertical holding time is preferably 1 to 5 minutes, more preferably 1 to 3 minutes. Holding the membrane for 1 minute or longer makes it easier to obtain a separation functional layer with the desired function, while holding the membrane for 3 minutes or less can prevent membrane defects due to excessive drying of the organic solvent, thereby suppressing performance degradation.

[0123] The composite semipermeable membrane obtained by the above-mentioned method can be further subjected to a step of washing with hot water at a temperature in the range of 25 to 90°C for 1 to 60 minutes, thereby further improving the solute blocking performance and water permeability of the composite semipermeable membrane.

[0124] (8) Valuable material separation device The valuable resource separation device of the present invention comprises an alkaline treatment means for bringing a material into contact with an alkaline aqueous solution, and a first nanofiltration means for separating the valuable resource-containing alkaline aqueous solution containing monovalent valuable resources and polyvalent valuable resources obtained by the alkaline treatment means into a permeate and a non-permeate in which the ratio (P / Q) of the sum of the ion concentrations of the monovalent valuable resources P to the sum of the ion concentrations of the polyvalent valuable resources Q is 5 or more.

[0125] The valuable resource separation device of the present invention can use a separation membrane unit containing a nanofiltration membrane as the first nanofiltration means. A "separation membrane unit" refers to a single pressure vessel containing one or more separation membrane elements connected in series, integrated with a booster pump, piping, and valves, and one that uses a nanofiltration membrane is called a nanofiltration membrane unit. Furthermore, one that uses a microfiltration membrane and / or an ultrafiltration membrane used in the pretreatment step is called a pretreatment unit. A "separation membrane element" refers to a vessel containing a separation membrane so that liquid can be filtered, and one that uses a nanofiltration membrane is called a nanofiltration membrane element.

[0126] In the valuable resource separation device of the present invention, the nanofiltration membrane elements in the first nanofiltration means may use the same nanofiltration membrane, or different nanofiltration membranes may be used for each element.

[0127] In the valuable resource separation device of the present invention, the nanofiltration membrane of at least one nanofiltration membrane element constituting the nanofiltration membrane unit used as the first nanofiltration means preferably has a difference of 40% or more between the glucose removal rate when a 1000 mg / L glucose aqueous solution at 25°C and pH 6.5 is passed through it at an operating pressure of 0.5 MPa and the isopropyl alcohol removal rate when a 1000 mg / L isopropyl alcohol aqueous solution at 25°C and pH 6.5 is passed through it at an operating pressure of 0.5 MPa and the glucose removal rate is 70% or more. Furthermore, it is more preferable that the nanofiltration membranes of all nanofiltration membrane elements constituting the nanofiltration membrane unit used as the first nanofiltration means are nanofiltration membranes that satisfy the above requirements.

[0128] The valuable resource separation device of the present invention preferably includes a pH adjusting device that adjusts the pH of at least a portion of the non-permeated water obtained by the first nanofiltration means to 8 or less, and a device for recovering the generated gas.

[0129] Furthermore, the valuable resource separation device of the present invention preferably includes a second nanofiltration means for separating the non-permeated water containing polyvalent valuable resources obtained by the first nanofiltration means into a permeated water having a ratio (R / Q) of the sum of the organic base concentrations R to the sum of the polyvalent ion concentrations Q of 3 or more, and a non-permeated water containing polyvalent valuable resources.

[0130] The valuable resource separation device of the present invention can use a nanofiltration unit as the second nanofiltration means. Furthermore, it is preferable that the nanofiltration membrane included in at least one nanofiltration membrane element constituting the nanofiltration membrane unit used as the second nanofiltration means has a difference of 60% or more between the glucose removal rate when a 1000 mg / L glucose aqueous solution at 25°C and pH 6.5 is passed through it at an operating pressure of 0.5 MPa and the isopropyl alcohol removal rate when a 1000 mg / L isopropyl alcohol aqueous solution at 25°C and pH 6.5 is passed through it at an operating pressure of 0.5 MPa and an operating pressure of 25°C, and that the glucose removal rate is 70% or more. Furthermore, it is more preferable that the nanofiltration membranes included in all nanofiltration membrane elements constituting the nanofiltration membrane unit used as the second nanofiltration means are nanofiltration membranes that satisfy the above requirements.

[0131] One embodiment of the valuable resource separation device of the present invention is shown in FIGS. 5 and 6. In the valuable resource separation device shown in FIG. 5, raw water 1, which is a valuable resource-containing alkaline aqueous solution containing monovalent valuables, polyvalent valuables, and sulfide ions, is temporarily stored in raw water tank 2 and then treated in pretreatment unit 3. The pretreated raw water is sent to first nanofiltration unit 4, where it is separated into permeate a (5), which has a ratio (P / Q) of 5 or more between the sum of the ion concentrations of the monovalent valuables, P, and the sum of the ion concentrations of the polyvalent valuables, Q, and non-permeate b (6), which contains polyvalent valuables and sulfide ions. The non-permeate b (6) may be circulated back to raw water tank 2. The pH of the non-permeate b (6) is adjusted to 8 or less using a pH adjuster 7, generating hydrogen sulfide. The generated hydrogen sulfide is then recovered using a gas recovery device 8, yielding a hydrogen sulfide aqueous solution 9 and non-permeate b (10) containing polyvalent valuables. As described in (5-2) Gas Recovery Step of (5) Hydrogen Sulfide Recovery Step above, examples of the gas recovery device include a submerged trap device, a scrubber device, and an exhaust gas treatment device. Note that the pH of the non-permeated water b may be adjusted in part or in whole by a pH adjuster 7.

[0132] In the valuable resource separation device shown in FIG. 6, raw water 1 is separated by a first nanofiltration membrane unit 4 into permeate a (5), in which the ratio (P / Q) of the sum of the ion concentrations of monovalent valuables, P, to the sum of the ion concentrations of polyvalent valuables, Q, is 5 or more, and non-permeate b (6), which contains polyvalent valuables. Non-permeate b (6) may be circulated to the raw water tank 2. Non-permeate b (6) is supplied to a second nanofiltration membrane unit 4 (12) via an intermediate tank 11, where it is separated into permeate c (13), in which the ratio (R / Q) of the sum of the concentrations of organic bases, R, to the sum of the concentrations of polyvalent ions, Q, is 3 or more, and non-permeate d (14), which contains polyvalent valuables. Some or all of non-permeate c (14) may be circulated to the intermediate tank 11.

[0133] The valuable resource separation device of the present invention can be incorporated as part of a valuable resource recovery device that recovers monovalent and / or polyvalent valuable resources as compounds. [Example]

[0134] The present invention will be described below with reference to examples, but the present invention is not limited to these examples in any way.

[0135] 1. Measurement (Glucose removal rate, isopropyl alcohol removal rate) A 1000 mg / L glucose aqueous solution at 25°C and pH 6.5 was passed through the nanofiltration membrane at an operating pressure of 0.5 MPa. The glucose removal rate was calculated from the glucose concentrations in the permeate and feed water using the following formula (5). The glucose concentration was determined using a refractometer (Shimadzu RID-6A). A 2000 mg / L isopropyl alcohol aqueous solution at 25°C and pH 6.5 was passed through the nanofiltration membrane at an operating pressure of 0.5 MPa. The isopropyl alcohol removal rate was calculated from the isopropyl alcohol concentrations in the permeate and feed water using the following formula (6). The isopropyl alcohol concentration was determined using a gas chromatograph (Shimadzu GC-18A). Note that each removal rate was rounded to one decimal place. Glucose removal rate (%) = 100 × (1 - (glucose concentration in permeate water / glucose concentration in feed water)) Equation (5) Isopropyl alcohol removal rate (%) = 100 × (1 - (isopropyl alcohol concentration in permeate water / isopropyl alcohol concentration in feed water)) Equation (6).

[0136] (ion concentration measurement) The ion concentrations of lithium, germanium, sulfur, and calcium in the aqueous solution were quantified using a Hitachi P-4010 ICP (inductively coupled plasma emission spectrometry) instrument. The ion concentrations of organic bases were also quantified using a Tosoh IC-8100 ion chromatograph. The values for each ion concentration (mg / L) were rounded to the nearest whole number.

[0137] (pH) The pH was measured with a pH meter.

[0138] (The ratio (P / Q) of the sum of the ion concentrations of monovalent substances, P, to the sum of the ion concentrations of polyvalent substances, Q) In the examples described below, lithium is used as the monovalent valuable and germanium is used as the polyvalent valuable, so the sum of the ion concentrations of the monovalent valuables, P, corresponds to the lithium ion (hereinafter "Li ion") concentration (mg / L), and the sum of the ion concentrations of the polyvalent valuables, Q, corresponds to the germanium ion (hereinafter "Ge ion") concentration (mg / L). The ratio of the Li ion concentration to the Ge ion concentration was calculated as the ratio (P / Q) of the sum of the ion concentrations of the monovalent valuables in the aqueous solution, P, to the sum of the ion concentrations of the polyvalent valuables, Q, using the following formula (7): P / Q = Li ion concentration (mg / L) / Ge ion concentration (mg / L) ···Eq. (7).

[0139] (Li purity) The purity of lithium (Li) in the aqueous solution was calculated using the following formula (8). Li purity (%) = Li ion concentration (mg / L) / {Li ion concentration (mg / L) + Ge ion concentration (mg / L) + sulfur concentration (mg / L) + alkali component concentration (mg / L)) ··· Equation (8).

[0140] (Organic base purity) The purity of the organic base in the aqueous solution was calculated using the following formula (9). Organic base purity (%) = organic base concentration (mg / L) / {Li ion concentration (mg / L) + Ge ion concentration (mg / L) + sulfur concentration (mg / L) + organic base concentration (mg / L)} Equation (9).

[0141] (Li recovery rate) The lithium (Li) recovery rate was calculated using the following formula (10). Li recovery rate (%) = Li ion concentration in recovered permeate (g / L) × amount of recovered permeate (L) / amount of lithium contained in solid electrolyte used for immersion in alkaline aqueous solution (g) × 100 Equation (10).

[0142] (organic base recovery rate) The recovery rate of the organic base was calculated using the following formula (11). Organic base recovery rate (%) = {organic base concentration in permeate c (mg / L) × total amount of permeate c (L)} / amount of organic base in alkaline aqueous solution used to soak the material (mg) × 100 Equation (11).

[0143] (The ratio (R / Q) of the sum of the concentrations of organic bases R to the sum of the concentrations of polyvalent ions Q) The ratio of the organic base concentration to the Ge ion concentration was calculated as the ratio (R / Q) of the sum of the organic base concentrations in the aqueous solution R to the sum of the ion concentrations of the polyvalent substances Q using the following formula (12). R / Q = organic base concentration (mg / L) / Ge ion concentration (mg / L) Equation (12).

[0144] 2. Nanofiltration Membrane Fabrication (Preparation of porous support membrane) Nonwoven fabric made of polyester fiber (breathability 0.5-1cc / cm 2 A 15.0 mass% solution of polysulfone in dimethylformamide (DMF) was cast onto a substrate (semiconductor substrate) at room temperature (25°C) to a thickness of 180 μm, and the substrate was immediately immersed in pure water and left for 5 minutes to prepare a porous support membrane (thickness 150-160 μm) made of fiber-reinforced polysulfone support membrane.

[0145] (Preparation of nanofiltration membrane N1) The porous support membrane obtained above was immersed in an aqueous solution containing 2.0% by mass of 2,5-diethylpiperazine for 2 minutes, and then slowly pulled up vertically. Nitrogen was blown from an air nozzle to remove excess aqueous solution from the surface of the support membrane, and then an n-decane solution containing 0.1% by mass of trimesoyl chloride was poured into the membrane at a flow rate of 160 cm. 3 / m 2 The support membrane surface was completely wetted with the solution, and the membrane was left to stand for 1 minute in an atmosphere of 25°C. Next, to remove excess solution from the membrane, the membrane was held vertically for 1 minute to drain, and then dried by blowing gas at 20°C onto it using a fan. After drying, the membrane was immediately washed with water and stored at room temperature to obtain nanofiltration membrane N1.

[0146] (Preparation of nanofiltration membrane N2) Nanofiltration membrane N2 was obtained in the same manner as nanofiltration membrane N1, except that 2,5-dimethylpiperazine was used instead of 2,5-diethylpiperazine.

[0147] (Preparation of nanofiltration membrane N3) Nanofiltration membrane N3 was obtained in the same manner as nanofiltration membrane N2, except that the one minute of standing in an atmosphere of 25°C was changed to one minute of heating in an atmosphere of 50°C.

[0148] (Preparation of nanofiltration membrane N4) Nanofiltration membrane N4 was obtained in the same manner as nanofiltration membrane N2, except that the amount of 2,5-dimethylpiperazine used was changed to 1.0 mass %.

[0149] The glucose and isopropyl alcohol removal rates of the obtained nanofiltration membranes N1 to N4 were evaluated, and the results are shown in Table 1.

[0150] [Table 1]

[0151] (Nanofiltration membrane spiral element) Using the above nanofiltration membranes N1 to N4, an effective membrane area of 0.5 m 2 A spiral element with a diameter of 6.4 cm and a length of 30 cm was prepared. 3 / m 2 / d) is the permeate flow rate (m 3 / d) was divided by the effective membrane area.

[0152] 3. Separation of valuable resources (1) Alkali treatment process (Preparation of solid electrolyte E1) 39 g of Li2S (Sigma-Aldrich), 37 g of P2S5 (Sigma-Aldrich), and 24 g of GeS2 (Kojundo Chemical Laboratory Co., Ltd.) were weighed out, and then placed in a zirconia pot together with 10 mm diameter zirconia balls. The pot was then sealed under an argon atmosphere. The pot was then mixed for 40 hours by rotating it in a ball mill at a speed of 370 revolutions per minute. The resulting mixed powder was then reduced in pressure to 30 Pa and sealed. It was then heated at 550°C for 8 hours to produce a sulfide-based solid electrolyte E1 containing lithium, germanium, sulfur, and phosphorus as its constituent components. The composition of the sulfide solid electrolyte was Li 3.35 Ge 0.35 P 0.65 It was S4.

[0153] (Preparation of valuables-containing alkaline aqueous solution AL1) 55 g of solid electrolyte E1 was immersed in 1 L of an alkaline aqueous solution containing 0.1 mass % of calcium hydroxide, an inorganic base, for 6 hours to extract various valuable substances, thereby obtaining alkaline aqueous solution AL1 containing valuable substances. During the procedure for obtaining AL1, there was no unpleasant odor due to the generation of hydrogen sulfide.

[0154] (Preparation of valuable alkaline aqueous solution AL2) A valuable-material-containing alkaline aqueous solution AL2 was obtained in the same manner as AL1, except that an aqueous solution containing 1.0 mass% of ammonia (manufactured by Sigma-Aldrich Co.) was used as the alkaline aqueous solution. During the procedure for obtaining AL2, there was no unpleasant odor due to the generation of hydrogen sulfide.

[0155] (Preparation of valuable alkaline aqueous solution AL3) A valuable-material-containing alkaline aqueous solution AL3 was obtained in the same manner as AL1, except that an aqueous solution containing 1.0 mass% TMAH (Sigma-Aldrich), an organic base and a quaternary ammonium salt, was used as the alkaline aqueous solution. During the procedure for obtaining AL3, there was no unpleasant odor due to the generation of hydrogen sulfide.

[0156] (Preparation of valuable alkaline aqueous solution AL4) A valuable-material-containing alkaline aqueous solution AL4 was obtained in the same manner as AL1, except that an aqueous solution containing 1.0 mass% TEAH (Sigma-Aldrich), an organic base and a quaternary ammonium salt, was used as the alkaline aqueous solution. During the procedure for obtaining AL4, there was no unpleasant odor due to the generation of hydrogen sulfide.

[0157] The compositions of the prepared alkaline aqueous solutions containing valuable substances are shown in Table 2.

[0158] [Table 2]

[0159] (2) Separation process A [Example 1] A nanofiltration membrane spiral element fabricated using nanofiltration membrane N1 was used as the first nanofiltration membrane. 10 L of a solution prepared by diluting the valuables-containing alkaline aqueous solution AL1 with water 10 times was placed in the raw water tank as the raw water for the separation process. The system was operated using crossflow filtration under the following conditions: permeate flow rate: retentate flow rate = 1:9, permeate flow rate 0.07 L / min. The retentate was circulated back to the raw water tank so that it would mix with the raw water. Operation was stopped when 9 L of permeate was obtained, and the concentrations of valuables and alkaline components in the permeate and retentate were measured. The retentate used for concentration measurements was the solution in the raw water tank after operation was stopped. The results are shown in Table 3. The separation process using nanofiltration membrane N1 successfully separated the raw water into permeate with a higher P / Q than the raw water and retentate with a lower P / Q than the raw water.

[0160] [Example 2] The same operation as in Example 1 was carried out, except that the raw water for the separation step was changed to 10 L of a solution prepared by diluting the valuables-containing alkaline aqueous solution AL2 tenfold with water. The results are shown in Table 3. Because the ammonia aqueous solution does not contain alkaline earth metal ions, the efficiency of alkaline elution of the material was improved compared to when calcium hydroxide, an inorganic base in Example 1, was used, and the Li recovery rate was also improved.

[0161] [Example 3] The same procedure as in Example 1 was carried out, except that the raw water for the separation process was changed to 10 L of a solution prepared by diluting the valuables-containing alkaline aqueous solution AL3 tenfold with water. The results are shown in Table 3. TMAH, a quaternary ammonium salt, is highly basic, resulting in a high alkaline elution efficiency of the material and an improved Li recovery rate. Furthermore, because TMAH is less permeable through nanofiltration than ammonia, the Li purity was also improved.

[0162] [Example 4] The same operation as in Example 1 was carried out, except that the raw water for the separation step was changed to 10 L of a solution prepared by diluting the valuables-containing alkaline aqueous solution AL4 tenfold with water. The results are shown in Table 3. TEAH, a quaternary ammonium salt with a large molecular weight, is even less likely to permeate the nanofiltration membrane than TMAH in Example 3, and therefore the Li purity was improved.

[0163] [Example 5] The same operation as in Example 3 was carried out except that the nanofiltration membrane was changed to N2. The results are shown in Table 3. Nanofiltration membrane N2, which had a difference between the glucose removal rate and the isopropyl alcohol removal rate of 50% or more, was less permeable to polyvalent cations and TMAH and more permeable to small-sized Li than nanofiltration membrane N1 in Example 3, resulting in improved P / Q, Li purity, and Li recovery rate.

[0164] [Example 6] The same operation as in Example 3 was carried out except that the nanofiltration membrane was changed to N3. The results are shown in Table 3. The nanofiltration membrane N3, which has a glucose removal rate of 75% or more, is less permeable to polyvalent cations than the nanofiltration membrane N1 in Example 3, and therefore the P / Q and Li purity were improved.

[0165] [Table 3]

[0166] (3) Recovery of H2S [Example 7] In a flask connected from above via piping to 1 L of a trap solution containing 1 mol / L aqueous sodium hydroxide, 1 mol / L hydrochloric acid was added to 100 mL of the non-permeated water from Example 4 to adjust the pH to 8. 1 mol / L hydrochloric acid was added continuously for 1 hour to maintain the pH at 8. The sulfur concentration of the trap solution after treatment was measured and found to be 2500 mg / L, indicating that sulfur could be recovered from the non-permeated water.

[0167] (4) Separation process B [Example 8] The second nanofiltration membrane was the nanofiltration membrane N2. 1 L of the retentate obtained in Example 4 was diluted 10-fold with water, and 10 L of this solution was placed in an intermediate tank as the raw water for separation step B. The system was operated using crossflow filtration under conditions of a permeate flow rate: retentate flow rate = 1:9 and a permeate flow rate of 0.07 L / min. The retentate was circulated through the intermediate tank so that it would mix with the raw water. Operation was stopped when 9 L of permeate was obtained, and the concentrations of valuable materials and alkaline components in the permeate and retentate were measured to calculate the amounts of the components. The retentate used for concentration measurements was the solution in the intermediate tank after operation was stopped. The results are shown in Table 4. The separation step using the nanofiltration membrane N2 successfully separated the raw water into permeate with an R / Q ratio of 3 or greater and retentate with an R / Q lower than that of the raw water. In other words, a solution with a low Ge ion content and high organic base purity was obtained, which can be reused for extracting valuable materials from materials.

[0168] [Example 9] The same operation as in Example 7 was carried out except that nanofiltration membrane N4 was used as the second nanofiltration membrane. The results are shown in Table 4. Nanofiltration membrane N4, which had a difference between the glucose removal rate and the isopropyl alcohol removal rate of 60% or more, had high permeability to organic bases, and the R / Q of the permeate, the organic base purity, and the organic base recovery rate were improved.

[0169] [Table 4] [Industrial Applicability]

[0170] The present invention can be suitably used as a method for efficiently separating and recovering valuable materials such as lithium and germanium from waste materials, waste liquids, ores, slag, etc. generated in batteries and in the manufacturing process thereof. [Explanation of symbols]

[0171] 1 raw water 2 Raw water tank 3 Pretreatment Unit 4. First nanofiltration membrane unit 5 Permeate of the first nanofiltration membrane unit a 6. Retentate from the first nanofiltration membrane unit b 7 pH adjustment device 8. Gaseous hydrogen sulfide 9 Gas recovery device 10 Hydrogen sulfide aqueous solution 11 Aqueous solutions containing polyvalent substances 12 Intermediate Tank 13 Second nanofiltration membrane unit 14 Permeate of the second nanofiltration membrane unit c 15 Retentate from the second nanofiltration membrane unit d

Claims

1. A method for separating monovalent and polyvalent valuables, comprising: an alkaline treatment step of contacting a material with an alkaline aqueous solution; and a separation step A of obtaining, from the valuable-containing alkaline aqueous solution containing ions of monovalent valuables and ions of polyvalent valuables obtained in the alkaline treatment step, permeate a having a ratio (P / Q) of 5 or more between the sum of the ion concentrations of the monovalent valuables, P, and the sum of the ion concentrations of the polyvalent valuables, Q, using a nanofiltration membrane.

2. 2. The separation method according to claim 1, wherein the aqueous alkaline solution contains an organic base and / or ammonia.

3. 3. The separation method according to claim 2, wherein the alkaline aqueous solution contains a quaternary ammonium salt.

4. 4. The separation method according to claim 2 or 3, wherein the organic base has a formula weight of 90 or more.

5. 4. The separation method according to claim 1, wherein the material contains sulfur, and the non-permeated water b obtained in the separation step A contains sulfide ions.

6. 6. The separation method according to claim 5, further comprising the step of adjusting the pH of the non-permeated water b to 8 or less and recovering the hydrogen sulfide generated.

7. The separation method according to any one of claims 1 to 3, wherein the monovalent valuables include lithium.

8. The separation method according to any one of claims 1 to 3, wherein the material comprises a battery electrolyte.

9. A method for recovering lithium salts, comprising the separation method of claim 7.

10. The nanofiltration membrane used in the separation step A is used in the separation step A. The difference between the glucose removal rate when a 1000 mg / L aqueous glucose solution at 25 ° C. and pH 6.5 is passed through the nanofiltration membrane at an operating pressure of 0.5 MPa and the isopropyl alcohol removal rate when a 1000 mg / L aqueous isopropyl alcohol solution at 25 ° C. and pH 6.5 is passed through the nanofiltration membrane is 50% or more, and the glucose removal rate is 70% or more. The separation method according to any one of claims 1 to 3.

11. and a separation step B of obtaining, from the non-permeated water b containing the organic base and the polyvalent ions, a permeated water c having a ratio (R / Q) of the sum of the organic base concentrations R to the sum of the polyvalent ions concentrations Q of 3 or more by using the nanofiltration membrane.

12. The separation method according to claim 11, wherein the organic base has a formula weight of 90 to 210.

13. The nanofiltration membrane used in the separation step B has a glucose removal rate when a 1000 mg / L aqueous glucose solution at 25 ° C. and pH 6.5 is permeated at an operating pressure of 0.5 MPa. The difference between the glucose removal rate and the isopropyl alcohol removal rate when a 1000 mg / L aqueous isopropyl alcohol solution at 25 ° C. and pH 6.5 is permeated at an operating pressure of 0.5 MPa is 60% or more, and the glucose removal rate is 70% or more. The separation method according to claim 12.

14. A valuable resource separation device comprising: an alkaline treatment means for bringing a material into contact with an alkaline aqueous solution; and a first nanofiltration means for separating the alkaline aqueous solution containing monovalent valuable resources and polyvalent valuable resources obtained by the alkaline treatment means into a permeate having a ratio (P / Q) of the sum of the ion concentrations of the monovalent valuable resources P to the sum of the ion concentrations of the polyvalent valuable resources Q of 5 or more, and a non-permeate.

15. The valuable resource separation device according to claim 14, further comprising: a pH adjusting device that adjusts the pH of the non-permeated water to 8 or less; and a device that recovers the generated gas.

16. The nanofiltration membrane unit includes a nanofiltration membrane provided in at least one nanofiltration membrane element constituting the nanofiltration membrane unit used in the nanofiltration means B. The nanofiltration membrane has a glucose removal rate when a 1000 mg / L aqueous glucose solution at 25°C and pH 6.5 is permeated at an operating pressure of 0.5 MPa, a difference between the glucose removal rate and the isopropyl alcohol removal rate when a 1000 mg / L aqueous isopropyl alcohol solution at 25°C and pH 6.5 is permeated at an operating pressure of 0.5 MPa, a difference between the glucose removal rate and the isopropyl alcohol removal rate is 60% or more, and the glucose removal rate is 70% or more.

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