Resource recovery method and resource reuse method

Abstract

The present invention recovers resources such as phosphorus from a product such as a used nonaqueous electrolyte battery that contains a nonaqueous electrolyte solution. This resource recovery method for recovering resources from a cleaning liquid that is generated when a product which contains a nonaqueous electrolyte solution is disassembled and cleaned comprises: an acid treatment step (step S2) for adding an acid to the cleaning liquid and heating the same; and a step (step S3) for adding a pretreated layered hydroxide to the cleaning liquid after the acid treatment step. The pretreatment applied to the layered hydroxide includes applying a heat treatment to the layered hydroxide.

Description

Resource recovery and recycling methods

[0001] The present invention relates to a resource recovery method and a resource reuse method, and more specifically to a method for recovering specific elements that become useful resources from products containing nonaqueous electrolytes, such as used nonaqueous electrolyte batteries, and a method for reusing the recovered resources (specific elements).

[0002] With the shift to electric vehicles expected to progress by 2030, the amount of lithium-ion batteries (hereinafter referred to as "LIBs") discarded and recycled is expected to increase. There is a demand for the recovery and reuse of useful resources from these LIBs, and in particular, legal regulations regarding recycling rates have been introduced in the EU. Although there are no numerical restrictions in Japan, the situation remains one in which resource recycling is required.

[0003] Many useful resources are used in LIBs, including elements such as Ni, Co, Mn, and Li contained in the active material, as well as Al and Cu used as current collectors, and Li, P, and F used as electrolyte salts in the electrolyte. Among these useful resources, the development of recovery processes for elements with particularly high resource value, such as Ni, Co, and Al, is progressing, and commercial recovery of some of these elements is beginning. However, there are few reports of processes targeting P and F.

[0004] Although it is not related to battery recycling, Japanese Patent Application Laid-Open No. 2000-106221 describes the use of lithium hexafluorophosphate (LiPF ６ This treatment method involves separating LiPF4 from LIB by a specific sorting process. ６ The method is characterized by including a step of adding a heated acid aqueous solution to a solution containing fluoride ions and phosphate ions to separate the ions into fluoride ions and phosphate ions, and then adding a fixative such as slaked lime to the ion aqueous solution to fix the ions. ６ (2) The crushed LIB is heated by means of pyrolysis or roasting to release LiPF into the exhaust gas. ６ It also states that the following should be included:

[0005] Japanese Patent Application Laid-Open No. 2000-106221

[0006] Currently, there is no prospect of recovering and reusing the P and F contained as electrolyte salts in the electrolyte solution. However, P and F are also materials for which there are concerns that their resources will be depleted on Earth. In particular, it is expected that reusing P, which has exceeded planetary boundaries (Earth's limits), will become an important issue in the future. In fact, the spread of EVs is cited as a factor in the future depletion of P resources.

[0007] A typical recycling process for LIB involves crushing and burning the LIB, followed by refining and recovering each element. Even in these methods, the main targets for recovery are elements such as Ni and Co, and there are few processes aimed at P and F.

[0008] The process disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2000-106221 is LiPF ６ The purpose of this process is to safely treat LIB while preventing the generation of toxic gases associated with the decomposition of LIB, and not to recover P or F. In the process disclosed in JP 2000-106221 A, a mixture of precipitates containing Li, P, and F is deposited, and therefore, these mixtures must be further separated before recycling. Furthermore, the formation of the precipitate is not element-selective, and various other metal elements are also precipitated at the same time, making their separation even more difficult.

[0009] In addition, development of non-aqueous electrolyte batteries such as sodium ion batteries (SIBs) is also underway as an alternative to lithium ion batteries, and it is necessary to consider the recovery of P and F from non-aqueous electrolyte batteries other than LIBs, as with LIBs.

[0010] An object of the present invention is to provide a resource recovery method capable of recovering resources, particularly phosphorus (P), from products containing a nonaqueous electrolyte, such as used nonaqueous electrolyte batteries, and to provide a method for reusing the recovered resources (particularly phosphorus).

[0011] A resource recovery method according to one embodiment of the present invention is a method for recovering resources from a cleaning solution produced when a product containing a nonaqueous electrolyte is disassembled and cleaned, and includes an acid treatment step of adding an acid to the cleaning solution and heating the solution, and a step of adding a pretreated layered hydroxide to the cleaning solution after the acid treatment step, wherein the pretreatment of the layered hydroxide includes subjecting the layered hydroxide to a heat treatment.

[0012] In the resource recovery method according to one embodiment of the present invention, the pretreatment of the layered hydroxide may further include intercalating monovalent anions into the heat-treated layered hydroxide.

[0013] A resource recycling method according to one embodiment of the present invention includes a step of immersing the sediment recovered by the resource recovery method described above in a liquid.

[0014] According to the present invention, resources such as phosphorus can be recovered and reused from products containing a non-aqueous electrolyte, such as used non-aqueous electrolyte batteries.

[0015] Fig. 1 is a flow diagram of a resource recovery method according to one embodiment of the present invention. Fig. 2 is a flow diagram showing an example of pretreatment applied to a layered hydroxide. Fig. 3 is a flow diagram of a resource reuse method according to one embodiment of the present invention. Fig. 4 is a graph showing the relationship between the type of anion pre-intercalated into the layered hydroxide, the recovery rate when phosphoric acid is recovered using this layered hydroxide, and the discharge rate during reuse.

[0016] Hereinafter, the present invention will be described mainly using LIB as a specific example, but the subject matter of the present invention is not limited to LIB and can be applied to various products containing non-aqueous electrolytes.

[0017] In recycling LIBs, the process of crushing and roasting used LIBs without separating them ultimately reduces the CO2 emissions from burning LIBs. ２ However, as waste disposal is a problem, it is expected that this will decrease in the future. In recent years, therefore, a process has been developed to disassemble and clean LIBs after use and reuse each of their components.

[0018] The cleaning solution generated at this time contains the electrolyte component of LIB, specifically LiPF６ The metal components contained in the active material and current collector foil that make up the electrodes of LIBs are separated and recovered without destroying them, so the only substances contained in the cleaning solution are small amounts of solid matter that has peeled off from the electrodes, etc., and trace amounts of Co ions and Mn ions that have eluted from the active material into the electrolyte during battery operation.

[0019] The inventors came up with the idea of ​​recovering useful resources contained in the LIB electrolyte from the cleaning solution in a recyclable form, and after various experiments and studies, they completed the present invention. Hereinafter, a resource recovery method and resource reuse method according to one embodiment of the present invention will be described.

[0020] [Resource Recovery Method] Figure 1 is a flow diagram of a resource recovery method according to one embodiment of the present invention. This resource recovery method recovers resources from a cleaning solution produced when a product containing a nonaqueous electrolyte (hereinafter referred to as a "nonaqueous electrolyte-containing product") is disassembled and cleaned. The method includes the steps of: separating an oil layer and an aqueous layer from the cleaning solution and removing the oil layer (Step S1); acid treatment (Step S2) in which an acid is added to the cleaning solution and the solution is heated; adding a layered hydroxide that has been pretreated to the cleaning solution after the acid treatment (Step S3); recovering a precipitate formed by the addition of the layered hydroxide (Step S4); and recovering a fluorine compound from the cleaning solution after the precipitate has been recovered (Step S5). Each step is described in detail below.

[0021] [Cleaning Solution] The resource recovery method according to this embodiment is a method for recovering resources from cleaning solution generated when a non-aqueous electrolyte-containing product is disassembled and cleaned. The non-aqueous electrolyte-containing product is, for example, but not limited to, a non-aqueous electrolyte battery. The non-aqueous electrolyte battery is, for example, but not limited to, a non-aqueous electrolyte battery that has been recovered after its discharge capacity has decreased due to repeated charging and discharging, making it unsuitable for reuse.

[0022] The non-aqueous electrolyte battery in question is, for example, lithium hexafluorophosphate (LiPF ６) dissolved in an organic solvent such as ethylene carbonate or diethyl carbonate. Non-aqueous electrolyte batteries other than LIBs, such as sodium ion batteries, can also be subject to the resource recovery method of this embodiment if they use a non-aqueous electrolyte containing phosphorus as a component, such as one containing sodium hexafluorophosphate as an electrolyte salt in the non-aqueous electrolyte.

[0023] A used non-aqueous electrolyte-containing product is disassembled in a recycling process, and each component is washed with water to reuse it. In this embodiment, the washing liquid generated during this process is collected and used for resource recovery. In this specification, the term "washing liquid" does not refer to the liquid used to wash the non-aqueous electrolyte-containing product (the liquid before washing), but rather to the liquid generated as a result of washing the non-aqueous electrolyte-containing product. The washing liquid includes not only the liquid used for washing (i.e., water), but also the components of the electrolyte (e.g., LiPF) that have adhered to or permeated each component of the non-aqueous electrolyte-containing product. ６ and an organic solvent), and usually there is a layer containing water as the solvent and a layer containing the organic solvent.

[0024] There are no particular limitations on the method for cleaning the non-aqueous electrolyte-containing product, but one possible method is to store water in a container or the like and immerse the disassembled components in the water for cleaning.

[0025] LiPF contained in cleaning solution ６ The concentration of the electrolyte salt, such as LiPF , is not particularly limited. The resource recovery method according to this embodiment is applicable regardless of whether the concentration of the electrolyte salt contained in the cleaning solution is high or low. However, when cleaning a non-aqueous electrolyte-containing product after use in a recycling process, it is expected that each component will be washed consecutively or multiple non-aqueous electrolyte-containing products will be washed at once. ６ It is believed that electrolyte salts such as LiPF are contained at a fairly high concentration, for example, 0.1 to 1 mg / L. When the inventors disassembled a small LIB1 cell into the positive electrode, negative electrode, and laminate film and washed it with water, the washing solution contained about 0.2 mg / L of LiPF ６ In contrast, the amounts of eluted metal ions such as Co, Ni, Al, and Cu were all less than that of LiPF ６ It was less than 1 / 100 of the original value.

[0026] [Separation of Oil and Water Layers] The oil and water layers in the cleaning solution are separated and the oil layer is removed (Step S1). Among the liquids contained in the cleaning solution, organic solvents (ethylene carbonate, diethyl carbonate, dimethyl carbonate, propylene carbonate, etc.) used as solvents for the electrolyte are incompatible with water. Therefore, by leaving the solution to stand, the solution can be separated into an oil layer (organic solvent layer) and a water layer (water-based solvent layer). The standing time is not limited to, but is preferably 3 hours or more, more preferably 6 hours or more, even more preferably 8 hours or more, and even more preferably 12 hours or more. After the water and oil layers are separated, it is desirable to remove the oil layer to leave only the water layer. The oil layer can be removed, for example, by decantation.

[0027] LiPF ６ Electrolyte salts such as LiPF exist in a uniform concentration in the water layer and the oil layer due to diffusion. By removing the oil layer from the cleaning solution, an aqueous solution of the electrolyte salt is obtained. Since the cleaning solution is mostly water, most of the electrolyte salt contained in the cleaning solution can be recovered even if the oil layer is removed. ６ It has been reported that in the presence of a small amount of moisture, Li reacts with water and decomposes. ＋ Ions and PF ６ － It exists stably as an ion, Li ＋ Ions and PF ６ － Very few decomposition products other than ions are formed.

[0028] The step of separating the oil layer from the aqueous layer and removing the oil layer (Step S1) is an optional step. That is, the step of separating the oil layer from the aqueous layer and removing the oil layer (Step S1) may be omitted. When the proportion of the oil layer is small, even if the oil layer remains in the cleaning solution, there are cases where no problems occur in the acid treatment step (Step S2) described below. On the other hand, depending on the type and amount of the remaining organic solvent, there are cases where problems such as excessive pressure increase occur in the acid treatment step (Step S2). Therefore, it is preferable to perform the step of separating the oil layer from the aqueous layer and removing the oil layer (Step S1).

[0029] [Acid treatment] PF ６ － Ion to F － Ion and PO ｘ ｙ－ Ions (mainly PO ４ ３－ In order to further dissociate the water ions from the oil layer, an acid treatment step is carried out (step S2). Specifically, an acid is added to the cleaning solution (or the cleaning solution that has become only the water layer when the oil layer has been removed) and heated.

[0030] The type of acid to be added is not particularly limited, and hydrochloric acid, nitric acid, sulfuric acid, etc. can be used. The acid is preferably added as an aqueous solution. From the viewpoint of ease of handling and the degree of deviation (F after treatment), － ions or PO ｘ ｙ－ (number of ions) / (PF before treatment ６ － The number of ions). The same applies below. From the viewpoint of increasing the ion concentration, it is preferable to use hydrochloric acid. On the other hand, when hydrochloric acid is used, chloride ions may remain in the final solution, and a process for treating the chloride ions may be required. Nitric acid is preferable from the viewpoint of being able to omit such a process.

[0031] The concentration of the acid in the cleaning solution after the acid is added is preferably 1.5% by weight or more. If the acid concentration is too low, the degree of dissociation may not be increased even when heated. The acid concentration is more preferably 1.8% by weight or more. The upper limit of the acid concentration is preferably 3.0% by weight. Even if the acid concentration is too high, there is no problem in terms of increasing the degree of dissociation, but there is no advantage to adding an excessive amount. The upper limit of the acid concentration is more preferably 2.5% by weight.

[0032] The cleaning solution to which the acid has been added is heated. The cleaning solution is preferably heated by hydrothermal treatment in a sealed container. By heating in a sealed container while applying pressure, the degree of deviation can be further increased. The pressure in the sealed container is, but is not limited to, 1.2 to 2.0 MPa, for example. The sealed container can be a general hydrothermal container or a pressure container.

[0033] The heating temperature is preferably 80 to 100°C. If the heating temperature is too low, it may not be possible to increase the degree of deviation. On the other hand, when heating is performed in a sealed container, the pressure inside the container rises rapidly when the temperature exceeds the boiling point of water, so from the viewpoint of ease of handling, it is preferable to set the heating temperature to 100°C or less.

[0034] The heating time is preferably 3 hours or more. If the heating time is too short, it may not be possible to increase the degree of deviation. The heating time is preferably 4 hours or more. On the other hand, there is no advantage to extending the heating time excessively. The upper limit of the heating time is preferably 10 hours, and more preferably 6 hours.

[0035] After the acid treatment step, the cleaning solution is allowed to return to room temperature by natural cooling or the like. During or after cooling, water may be added to adjust the concentration. ６ － F formed by dissociation of ions － Ion and PO ｘ ｙ－ Ions (mainly PO ４ ３－ An aqueous solution containing ions is obtained.

[0036] [Addition of Layered Hydroxide] A layered hydroxide that has been subjected to a predetermined pretreatment is added to the cleaning solution after the acid treatment step (step S3), thereby selectively recovering P from the cleaning solution after the acid treatment step.

[0037] <Layered hydroxide> A layered hydroxide is a compound having a layered structure that can intercalate anions between layers. Examples of the layered hydroxide include layered double hydroxides (LDHs) represented by the following general formula (I), layered hydroxides of divalent metals represented by the following general formula (II), and layered rare earth hydroxides represented by the following general formula (III). [Md ２＋ （１－ｚ） Me ３＋ ｚ (OH － ) ２ ][(A ｍ－ ) ｚ／ｍ ・nH ２O]...(I) where Md, Me: metal element, A ｍ－ : an anion, 0<z<1 (however, in the case of a combination of Mg and Al, 0.16<z<0.33), m: an integer, n≧0. [Mf ２＋ ａ (OH － ) ｂ ][(D ｃ－ ) （２ａ―ｂ）／ｃ ・gH ２ O] (II) where Mf is a metal element, D ｃ－ : an anion, a, b, c: integers, g≧0. [RE ３＋ ２ (OH － ) ５ ][(X － )・hH ２ O] (III) where RE: rare earth element, X-: anion, and h is 1.0 to 2.0.

[0038] There are various combinations of metal elements and anions in layered hydroxides. For example, when the layered hydroxide is a layered double hydroxide represented by the general formula (I), examples of the divalent metal element (Md) include Mg, Cu, Ni, Zn, Fe, and Mn. Examples of the trivalent metal element (Me) include Al, Fe, Mn, Cr, and Co. The anion (A ｍ－ ) is CO ３ ２－ , O.H. － , Cl － , NO ３ － , S.O. ４ ２－ , F － , P.O. ｓ ｍ－ (s is an integer) and Fe(CN ６ ) ３－ etc.

[0039] Representative compositions of layered double hydroxides are shown in Table 1 (K. Morimoto, Rock and Mineral Chemistry 48, 46-50 (2019)).

[0040] When the layered hydroxide is a layered hydroxide of a divalent metal represented by the general formula (II), examples of the metal element (Mf) include Cu and Zn. ｃ－ ) is Cl － , O.H. － , C.H. ３ COO － , NO ３ － , S.O. ４ ２－ , CO ３ ２－ and P.O. ｔ ｃ－ (t is an integer) and the like. Specifically, Cu ２ (OH) ３ (NO ３ ) H ２ O, Zn ５ (OH) ８ (NO ３ ) ２ ・2H ２ O, Zn ５ (OH) ８ Cl ２ ・H ２ O and Zn ５ (OH) ８ (OCOCH ３ ) ２ ・2H ２ Examples include O.

[0041] In the case of layered hydroxides of divalent metals, many have a structure that incorporates positive ions (cations), but in this embodiment, the purpose is to recover phosphate ions, i.e., to insert anions between the layers. Therefore, Zn is preferred as the metal element (Mf). However, layered hydroxides containing metal elements other than Zn can also be used as long as they are capable of incorporating anions between the layers.

[0042] When the layered hydroxide is a layered rare earth hydroxide represented by the general formula (III), the trivalent rare earth element (RE) is preferably Y, and the anion (X － ) is Cl － ,Br － , NO ３ － and CH ３ COO － etc.

[0043] Among the layered hydroxides, Mg ６ Al ２ (CO ３ ) (OH) １６ ・4H ２ O (hydrotalcite), Zn ５ (OH) ８ Cl ２ ・H ２ O and Zn(OH) ８ (OCOCH ３ ) ２ ・2H ２ O is preferred.

[0044] <Pretreatment of Layered Hydroxide> In this embodiment, the pretreated layered hydroxide is added to the cleaning solution. Fig. 2 is a flow diagram showing an example of the pretreatment of the layered hydroxide. The pretreatment in Fig. 2 includes subjecting the layered hydroxide to a heat treatment (step SA1) and intercalating the heat-treated layered hydroxide with monovalent anions (step SA2).

[0045] Among the pretreatment steps shown in FIG. 2 , intercalating monovalent anions into the heat-treated layered hydroxide (step SA2) is an optional step. That is, the pretreatment of the layered hydroxide may include heat treatment of the layered hydroxide (step SA1), but may not include intercalating monovalent anions into the heat-treated layered hydroxide (step SA2). In other words, the layered hydroxide used in the resource recovery method according to this embodiment may be one that has been heat-treated. As will be described later, using a layered hydroxide in which monovalent anions have been intercalated after heat treatment increases the efficiency of phosphorus recovery and subsequent reuse of the recovered phosphorus. On the other hand, phosphorus recovery is possible even if the layered hydroxide is not intercalated with monovalent anions.

[0046] The pretreatment applied to the layered hydroxide includes a heat treatment (step SA1). The layered structure of the layered hydroxide is destroyed by heat treatment in the atmosphere. When the layered hydroxide is added to a solution containing anions in a destroyed state, the layered hydroxide reconstructs its layered structure while incorporating anions in the solution between the layers. This allows the anions in the solution to be efficiently incorporated between the layers.

[0047] Depending on the type of interlayer anion contained in the layered hydroxide, it may be possible to cause ion exchange between the interlayer anion and the anion in the solution, without carrying out heat treatment (without destroying the layered structure of the layered hydroxide), and thereby incorporate the anion in the solution into the interlayer space of the layered hydroxide. In this case, the heat treatment can be omitted.

[0048] The heating temperature when heat-treating the layered hydroxide is, for example, 400 to 650°C. If the heating temperature is too high, depending on the type of layered hydroxide, crystallization of the constituent elements (for example, crystallization of MgO in hydrotalcite) will proceed and stabilize, which may hinder recrystallization in the subsequent recovery process, resulting in a slight decrease (by about several percent) in the recovery rate of phosphate ions. On the other hand, if the heating temperature is too low, depending on the type of layered hydroxide, structural destruction may not proceed sufficiently, resulting in a decrease in the recovery rate of phosphate ions in the subsequent recovery process. The lower limit of the heating temperature is preferably 450°C, more preferably 500°C. The upper limit of the heating temperature is preferably 600°C, more preferably 550°C. The heating time when heat-treating the layered hydroxide is, for example, 0.5 to 5 hours, preferably 1 to 3 hours.

[0049] It is preferable to further intercalate monovalent anions into the heat-treated layered hydroxide (step SA2). Intercalation can be performed, for example, by stirring the heat-treated layered hydroxide in an aqueous solution of a salt containing monovalent anions (e.g., sodium acetate). The temperature at this time can be room temperature. The mixing time is preferably 15 minutes to 2 hours. After stirring, the layered hydroxide intercalated with monovalent anions is recovered by filtration, drying, etc.

[0050] In the resource recovery method according to this embodiment, as will be described later, a layered hydroxide is added to the cleaning solution, and PO in the cleaning solution is removed. ｘ ｙ－ Ions (mainly PO ４ ３－ Phosphorus is recovered by incorporating monovalent anions (phosphate ions, hereafter referred to simply as "phosphate ions") between the layers of the layered hydroxide compound. When recycling phosphorus, the layered hydroxide with phosphate ions incorporated between the layers is immersed in a liquid, and the phosphate ions are discharged from the interlayer space into the liquid. Intercalating monovalent anions into the layered hydroxide before adding it to the cleaning solution (i.e., the pretreatment step) can increase the amount of phosphate ions discharged in the recycling step (i.e., the step of discharging phosphate ions from the layered hydroxide with phosphate ions). This means that phosphorus can be recycled more efficiently. The mechanism behind this is unclear, but it is thought that the stability of monovalent anions is higher than that of phosphate ions in layered hydroxides, and their simultaneous presence with phosphate ions promotes the preferential discharge of phosphate ions.

[0051] The monovalent anions intercalated into the layered hydroxide include, but are not limited to, CH ３ COO － , Cl － Or NO ３ － is preferred, and CH ３ COO － is particularly preferred.

[0052] The pretreatment of the layered hydroxide may be carried out immediately before adding it to the cleaning solution, or may be carried out in advance separately from the treatment of the cleaning solution. ２ For example, if stored in the atmosphere, CO contained in the atmosphere ２ Due to the presence of carbon dioxide and moisture, carbonate ions may spontaneously intercalate into the layered hydroxide, which may reduce the recovery rate of phosphoric acid.

[0053] <Fixation of Phosphoric Acid by Addition of Layered Hydroxide> The layered hydroxide pretreated as described above is added to the cleaning solution after the acid treatment step. The amount of layered hydroxide added is not particularly limited, but is, for example, 0.01 to 50 g / cc. The lower limit of the amount of layered hydroxide added is preferably 0.1 g / cc, more preferably 0.3 g / cc. The upper limit of the amount of layered hydroxide added is preferably 10 g / cc, more preferably 5 g / cc.

[0054] After adding the layered hydroxide, the washing solution is stirred and mixed. The temperature at this time can be room temperature. The mixing time is preferably 15 minutes to 2 hours. If the mixing time is too short, recovery may not be sufficient. On the other hand, if the mixing time is too long, the recovery amount will be saturated. In addition, the layered hydroxide may dissolve in the acidic washing solution.

[0055] The pH of the washing solution when the layered hydroxide is added is preferably acidic (less than 7.0). The pH of the washing solution when the layered hydroxide is added is more preferably 5.0 or less, and even more preferably 2.0 to 4.0. The recovery rate is best when the pH is 2.0 to 4.0, and the recovery rate tends to decrease as the pH increases. This tendency is more pronounced when a layered hydroxide that has only been heat-treated is used, and the difference tends to be smaller when a layered hydroxide that has been heat-treated and then intercalated with a monovalent anion is used.

[0056] By adding a layered hydroxide, anions in the cleaning solution can be intercalated between the layers and recovered. In many cases, the intercalation reaction between the layers has a priority depending on the ion species, ion valence, ion size, etc. In this embodiment, the cleaning solution contains F － Ion and PO ｘ ｙ－ Ions (mainly PO ４ ３－ ions), but due to the selectivity of the ions, ｘ ｙ－ ions are preferentially intercalated between the layers. ｘ ｙ－ The ions can be fixed and recovered as a solid (precipitate).

[0057] [Recovery of phosphorus-containing precipitate] The phosphorus-containing precipitate (PO) formed by the addition of layered hydroxide was recovered. ｘ ｙ－ The layered hydroxide having ions trapped between the layers is recovered (step S4 (FIG. 1)). The precipitate can be recovered by a general-purpose operation such as filtration.

[0058] [Recovery of Fluorine Compounds] Fluorine compounds are recovered from the cleaning solution after the phosphorus-containing precipitate has been recovered (step S5 ( FIG. 1 )). The recovery of fluorine compounds can be performed by a general process. For example, by adding a calcium compound such as calcium chloride, fluorine ions are precipitated as calcium fluoride, and fluorine can be recovered.

[0059] [Resource Recycling Method] Next, a method for recycling phosphorus recovered by the above-described resource recovery method will be described. More specifically, the precipitate (PO ｘ ｙ－ PO ｘ ｙ－ A method for extracting ions will now be described.

[0060] 3 is a flow diagram of a resource recycling method according to one embodiment of the present invention. This method includes a step (step SB1) of immersing the precipitate recovered in step S4 of FIG. 1 in a liquid capable of eluting phosphate ions. By immersing the precipitate in the liquid, the intercalated PO ｘ ｙ－ Ions are expelled into the liquid.

[0061] The liquid in which the phosphorus-containing precipitate is immersed is not particularly limited as long as it can dissolve the phosphate ions trapped between the layers, but is preferably water, and may be a mixed solvent of water and other solvents such as alcohol. The pH of the liquid in which the precipitate is immersed is preferably basic (above pH 7.0). Immersing the precipitate in a basic liquid can dissolve PO ｘ ｙ－ The mechanism behind this is unclear, but PO ｘ ｙ－The discharge of ions is caused by, for example, Cl contained in an acidic solution. － Rather than exchange with OH contained in basic solvents, － This is thought to be because the exchange with HCl proceeds more remarkably. The pH of the liquid in which the precipitate is immersed is preferably 8.0 or higher, and more preferably 10.0 or higher. The upper limit of the pH of the liquid in which the precipitate is immersed is not particularly limited, but is, for example, 13.0.

[0062] As described above, when a layered hydroxide intercalated with monovalent anions is used in the step of adding the layered hydroxide (step S3 in FIG. 1) in the resource recovery method according to this embodiment, the amount of PO discharged into the liquid is reduced compared to when a layered hydroxide that has only been subjected to heat treatment is used. ｘ ｙ－ The amount of ions increases.

[0063] The resource recovery method and resource reuse method according to one embodiment of the present invention have been described above. According to this embodiment, resources such as phosphorus can be recovered and reused from used nonaqueous electrolyte-containing products such as LIB. Specifically, phosphorus in the cleaning solution is recovered into a layered hydroxide, and then phosphate ions are extracted from the layered hydroxide at the timing of use, thereby allowing the phosphorus to be reused. Furthermore, fluorine compounds can be recovered from the cleaning solution after phosphorus recovery, allowing the fluorine to be reused.

[0064] As described above, the layered hydroxide used in the resource recovery method according to this embodiment may be one that has been heat-treated. Phosphorus recovery is possible even if it is not one that has been intercalated with a monovalent anion. That is, the resource recovery method according to this embodiment is a method for recovering resources from a cleaning solution produced when a nonaqueous electrolyte-containing product is disassembled and cleaned, and may include an acid treatment step of adding an acid to the cleaning solution and heating it, and a step of adding the heat-treated layered hydroxide to the cleaning solution after the acid treatment step.

[0065] Although the above description mainly deals with cases in which the nonaqueous electrolyte-containing product is a used nonaqueous electrolyte battery, the nonaqueous electrolyte-containing product is not limited to a used nonaqueous electrolyte battery. The nonaqueous electrolyte-containing product may be any product that contains a nonaqueous electrolyte containing the element to be recovered, such as a lithium ion capacitor or other electrochemical element. Furthermore, the nonaqueous electrolyte-containing product does not have to be a used product, but may also be an unused product.

[0066] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0067] [Resource Recovery] [No. 1] The positive and negative electrode components of the disassembled LIB were immersed in water for cleaning, and the cleaning solution was recovered. ６ The concentration of Li was 1.36 wt%, and approximately 11 wt% of the electrolyte was dissolved in water. The concentrations of Li, P, and F calculated from the above were 0.06 wt%, 0.28 wt%, and 1.02 wt%, respectively. This cleaning solution was left to stand for about 12 hours to separate into an oil layer and an aqueous layer, after which the oil layer was removed and only the aqueous layer was extracted. The pH of the extracted aqueous layer was 2.1.

[0068] To the washing solution, which now consisted of only an aqueous layer, hydrochloric acid was added so that the concentration of hydrogen chloride after the addition was 2.0 wt %. Specifically, 3.3 g of hydrochloric acid with a concentration of 36 wt % was added to 55 g of the aqueous layer. At this point, PO ４ ３－ The concentration was measured and found to be almost 0%. ６ At this point, almost all of ６ － ions and Li ＋ It is thought to exist as an ion.

[0069] The acid-added cleaning solution (aqueous layer) was placed in a pressure-resistant sealed container, sealed, and then subjected to hydrothermal treatment at 90°C for 6 hours. ６ － Ion to F － Ion and PO ｘ ｙ－ Ions (mainly PO ４ ３－ ions).４ ３－ Measure the concentration and PF ６ － It was confirmed that the ions were dissociated. ４ ３－ (number of ions) / (PF before treatment ６ － The number of ions (hereinafter the same) was about 95%. The pH of the cleaning solution (aqueous solution after acid treatment) remained at 2.1.

[0070] Next, phosphoric acid was recovered using layered hydroxide. ６ Al ２ (CO ３ ) (OH) １６ ・4H ２ Hydrotalcite (O) was used. The layered hydroxide had been previously heat-treated in air at 500°C for 2 hours to destroy the layered structure. Before adding the layered hydroxide, the acid-treated cleaning solution was diluted 25 times with water. The pH after dilution was approximately 3.5. The heat-treated layered hydroxide powder was added to this diluted cleaning solution at a weight ratio of 0.01 g / cc, and the mixture was stirred for 30 minutes.

[0071] Thereafter, the precipitate formed by the addition of the layered hydroxide was collected by filtration. ４ ３－ The concentration was measured, and the remaining amount (PO after treatment with layered hydroxide) ４ ３－ ions) / (PO before treatment with layered hydroxide ４ ３－ The total number of ions was 2.9%, resulting in a recovery rate of 97.1%. In other words, approximately 92% (= 0.95 × 0.971) of the P contained in the cleaning solution was recovered. This confirmed that phosphoric acid can be successfully recovered using layered hydroxide.

[0072] Next, the remaining solution was diluted with CaCl ２ 0.8 g of the compound was dissolved in the solution to obtain a white precipitate, and the fluorine compound was recovered by centrifugation. The composition of the recovered powder was CaF ２It was confirmed that the fluorine recovery rate ((number of recovered fluorines) / (PF contained in the washing solution (aqueous layer)) ６ － The number of F in the ion (=PF ６ － Six times the number of ions))) was about 85%.

[0073] [No. 2] The experiment was conducted in the same manner as No. 1, except that the hydrothermal treatment time in the acid treatment step was set to 3 hours. When the hydrothermal treatment time was set to 3 hours, the degree of dissociation was about 81%. Subsequent treatments were also carried out in the same manner, and about 97% of the phosphoric acid was recovered from the phosphoric acid after dissociation. The overall P recovery rate ((number of recovered P) / (PF contained in the washing solution (aqueous layer)) ６ － The number of ions) was approximately 79%.

[0074] [No. 3] An experiment similar to No. 1 was conducted, except that nitric acid was used instead of hydrochloric acid in the acid treatment step. When nitric acid was used, the deviation rate was about 87%, and the overall P recovery rate was about 85%.

[0075] [No. 4] The experiment was conducted in the same manner as No. 1, except that NaOH was added to the cleaning solution to adjust the pH to 5.5. When the pH of the cleaning solution was adjusted to 5.5, the recovery rate of phosphoric acid was approximately 63%, and the overall recovery rate of P was approximately 60%.

[0076] [No. 5] An experiment similar to No. 1 was conducted, except that NaOH was added to the cleaning solution to adjust the pH to 8.0. When the pH of the cleaning solution was adjusted to 8.0, the recovery rate of phosphoric acid was approximately 43%, and the overall recovery rate of P was approximately 41%.

[0077] [No. 6] An experiment similar to No. 1 was conducted, except that in the step of adding the layered hydroxide, layered hydroxide heat-treated at 400°C was used instead of layered hydroxide heat-treated at 500°C. When layered hydroxide heat-treated at 400°C was used, the phosphoric acid recovery rate was approximately 82%, slightly lower than in No. 1, and the overall P recovery rate was approximately 78%.

[0078] [No. 7] An experiment similar to No. 1 was conducted, except that in the step of adding the layered hydroxide, layered hydroxide heat-treated at 600°C was used instead of layered hydroxide heat-treated at 500°C. When layered hydroxide heat-treated at 600°C was used, the phosphoric acid recovery rate was approximately 97%, almost the same as No. 1, and the overall P recovery rate was approximately 92%.

[0079] [No. 8] An experiment similar to No. 1 was conducted, except that in the step of adding the layered hydroxide, layered hydroxide heat-treated at 700°C was used instead of layered hydroxide heat-treated at 500°C. When layered hydroxide heat-treated at 700°C was used, the phosphoric acid recovery rate was approximately 94%, slightly lower than in No. 1, and the overall P recovery rate was approximately 89%.

[0080] [No. 9] An experiment similar to No. 1 was conducted, except that the hydrothermal treatment time in the acid treatment step was set to 1 hour. When the hydrothermal treatment time was set to 1 hour, the deviation was approximately 60%, and the overall P recovery rate was approximately 58%.

[0081] [No. 10] An experiment similar to No. 1 was conducted, except that the hydrothermal treatment temperature in the acid treatment step was set to 80°C. When the hydrothermal treatment temperature was set to 80°C, the deviation was approximately 71%, and the overall P recovery rate was approximately 69%.

[0082] [No. 11] An experiment similar to No. 1 was conducted, except that the hydrothermal treatment temperature in the acid treatment step was set to 70°C. When the hydrothermal treatment temperature was set to 70°C, the deviation was approximately 55%, and the overall P recovery rate was approximately 53%.

[0083] [No. 12] An experiment similar to No. 1 was conducted, except that the hydrochloric acid concentration in the acid treatment step was set to 1.5 wt%. When the hydrochloric acid concentration was set to 1.5 wt%, the deviation was approximately 69%, and the overall P recovery rate was approximately 67%.

[0084] [No. 13] An experiment similar to No. 1 was conducted, except that the hydrochloric acid concentration in the acid treatment step was set to 1.0 wt%. When the hydrochloric acid concentration was set to 1.0 wt%, the deviation was about 40%, and the overall P recovery rate was about 38%.

[0085] [No. 14] In the acid treatment step, boiling was performed at 95°C for 6 hours without using a sealed container. During this process, the temperature was maintained while adding small amounts of water as needed to prevent changes in the concentration of the cleaning solution. Otherwise, the experiment was conducted in the same manner as No. 1. The deviation was approximately 43%, and the overall P recovery rate was approximately 41%.

[0086] [No. 15] Chloride-based layered zinc hydroxide (Zn ５ (OH) ８ Cl ２ ・H ２ The experiment was conducted in the same manner as in No. 1, except that phosphate recovery was approximately 98%, and the overall P recovery was approximately 93%.

[0087] [No. 16] Acetic acid-based layered zinc hydroxide (Zn(OH) ８ (OCOCH ３ ) ２ ・2H ２ The experiment was conducted in the same manner as in No. 1, except that phosphate recovery was approximately 99%, and the overall P recovery was approximately 94%.

[0088] [No. 17] The cleaning solution, which had become only an aqueous layer, was subjected to recovery treatment using a layered hydroxide without acid treatment, but phosphoric acid could not be recovered even when the mixing time was extended to 60 minutes. ６ － Ion to F － Ion and PO ｘ ｙ－ Ions (mainly PO ４ ３－ It was confirmed that P cannot be recovered unless it is dissociated into P and ions.

[0089] [No. 18] In the step of adding the layered hydroxide, the layered hydroxide is subjected to heat treatment at 600°C for 2 hours, and then immersed and stirred in a sodium acetate aqueous solution with a concentration of 1 mol / L to add monovalent anions (CH ３ COO －The layered hydroxide intercalated with phosphate was used. Otherwise, the experiment was conducted in the same manner as in No. 1. The recovery rate of phosphoric acid was approximately 94%, and the overall recovery rate of P was approximately 89%.

[0090] [No. 19] In the same manner as No. 18, monovalent anions (CH ３ COO － After preparing a layered hydroxide intercalated with phosphate phosphate (P), the layered hydroxide was stored in the air for two days. The experiment was conducted in the same manner as in No. 1, except that this layered hydroxide was used in the layered hydroxide addition step. The phosphoric acid recovery rate was approximately 53%, and the overall P recovery rate was approximately 50%.

[0091] The results of the resource recovery experiment are summarized in Table 2.

[0092]

[0093] [Resource Reuse] Next, an experimental example of reuse will be described. ４ ３－ ion-intercalated layered hydroxide) to PO ４ ３－ An experiment was carried out to re-eject the ions.

[0094] [No. 101] The precipitate (PO) collected in experiment No. 1 ４ ３－ 0.5 g of powder of the layered hydroxide in which ions are intercalated was immersed in 50 mL of an aqueous solution of NaOH adjusted to pH 11.0, and stirred for 30 minutes to allow the phosphoric acid to be discharged into the aqueous solution. As a result, about 10% (PO ４ ３－ Number of ions / PO contained in layered hydroxide ４ ３－ The phosphoric acid (number of ions; same below) was released into the aqueous solution, making it possible to reuse it.

[0095] [No. 102] Phosphoric acid was discharged into an aqueous solution in the same manner as in No. 101, except that the pH of the aqueous solution to be discharged was adjusted to 2.1. As a result, approximately 8% of the phosphoric acid was discharged into the aqueous solution, making it possible to reuse it.

[0096] [No. 103] Phosphoric acid was discharged into water in the same manner as in No. 101, except that ion-exchanged water was used as the discharge medium without adjusting the pH. As a result, approximately 9% of the phosphoric acid was discharged into the aqueous solution, making it possible to reuse it.

[0097] [No. 104] The precipitate (CH) collected in experiment No. 18 ３ COO － ions and PO ４ ３－ 0.5 g of powder of the ion-intercalated layered hydroxide was immersed in 50 mL of an aqueous NaOH solution adjusted to pH 11.0 and stirred for 30 minutes to remove phosphoric acid from the solution. As a result, approximately 60% of the phosphoric acid was removed and could be reused.

[0098] [No. 105] Phosphoric acid was discharged into an aqueous solution in the same manner as in No. 104, except that the pH of the aqueous solution to be discharged was adjusted to 2.1. As a result, approximately 8% of the phosphoric acid was discharged into the aqueous solution, making it possible to reuse it.

[0099] [No. 106] Phosphoric acid was discharged into water in the same manner as in No. 104, except that ion-exchanged water was used as the discharge medium without adjusting the pH. As a result, approximately 7% of the phosphoric acid was discharged into the aqueous solution, making it possible to reuse it.

[0100] The results of the resource reuse experiment are summarized in Table 3.

[0101]

[0102] These results confirmed that a predetermined amount of phosphoric acid can be reused by the resource recycling method according to the present embodiment. Furthermore, it was found that phosphoric acid can be reused particularly efficiently when phosphoric acid is recovered using a layered hydroxide in which monovalent anions have been intercalated in advance, and when the phosphoric acid is reused, it is discharged in an alkaline aqueous solution.

[0103] [Study on Anions] Next, the type of anion intercalated in advance into the layered hydroxide and the recovery rate (1-(PO after treatment with the layered hydroxide)) when phosphoric acid is recovered using this layered hydroxide were investigated. ４ ３－ ions) / (PO before treatment with layered hydroxide ４ ３－ ions)), and the release rate during reuse (PO released into the aqueous solution). ４ ３－ Number of ions / PO contained in layered hydroxide ４ ３－ The relationship between the number of ions and the amount of ions was investigated.

[0104] As the layered hydroxide, Mg ６ Al ２ (CO ３ ) (OH) １６ ・4H ２ Hydrotalcite (O) was used. The layered hydroxide was previously heat-treated in air at 600°C for 2 hours to destroy the layered structure. The heat-treated layered hydroxide powder was added to a sodium acetate aqueous solution, a sodium chloride aqueous solution, and a sodium nitrate solution, each with a concentration of 1 mol / L, in a weight ratio of 10 g / 300 cc, and stirred for 60 minutes. After that, the powder was filtered and dried to remove the anions (CH ３ COO － , Cl － and NO ３ － ) intercalated layered hydroxide was prepared.

[0105] The layered hydroxide powder prepared above was added to an aqueous solution of phosphoric acid with a concentration of 311 mg / L at a weight ratio of 3 g / 100 cc, and mixed by stirring for 60 minutes. After that, the mixture was filtered and dried to recover the precipitate (layered hydroxide in which monovalent anions and phosphate ions were intercalated).

[0106] The collected precipitate powder was added to aqueous NaOH solutions adjusted to concentrations of 0.02 mol / L and 0.1 mol / L at a weight ratio of 1 g / 100 cc, and mixed by stirring for 60 minutes. The phosphoric acid concentration in the aqueous solution after stirring was measured, and the discharge rate was calculated.

[0107] For comparison, a similar experiment was carried out using a layered hydroxide that had only been subjected to heat treatment. The results are shown in Table 4 and Figure 4.

[0108]

[0109] Regarding the release rate of phosphate ions during reuse, CH ３ COO － , Cl － and NO ３ － In addition, the effect of improving the discharge rate was confirmed in both cases. ３ COO － , Cl － and NO ３ － A common trend was observed.

[0110] On the other hand, regarding recovery rate, CH ３ COO － The intercalated form is Cl － Or NO ３ － The overall efficiency was significantly higher than that of the intercalated CH ３ COO － was found to be particularly excellent.

[0111] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention.

Claims

1. A method for recovering resources from a cleaning solution produced when a product containing a non-aqueous electrolyte is disassembled and cleaned, the method comprising: an acid treatment step of adding an acid to the cleaning solution and heating the solution; and a step of adding a pretreated layered hydroxide to the cleaning solution after the acid treatment step, wherein the pretreatment of the layered hydroxide includes subjecting the layered hydroxide to a heat treatment.

2. The resource recovery method according to claim 1, further comprising a step of separating an oil layer and a water layer in the washing solution and removing the oil layer prior to the acid treatment step.

3. The resource recovery method according to claim 1, wherein the layered hydroxide is a layered double hydroxide represented by the following general formula (I), a layered hydroxide of a divalent metal represented by the following general formula (II), or a layered rare earth hydroxide represented by the following general formula (III): [Md ２＋ （１－ｚ） Me ３＋ ｚ (OH － ) ２ ][(A ｍ－ ) ｚ／ｍ ・nH ２ O]...(I) where Md, Me: metal element, A ｍ－ : an anion, 0<z<1 (however, in the case of a combination of Mg and Al, 0.16<z<0.33), m: an integer, n≧0. [Mf ２＋ ａ (OH － ) ｂ ][(D ｃ－ ) （２ａ―ｂ）／ｃ ・gH ２ O] (II) where Mf is a metal element, D ｃ－ : an anion, a, b, c: integers, g≧0. [RE ３＋ ２ (OH － ) ５ ][(X － )・hH ２ O] (III) where RE: rare earth element, X － : an anion, and h is 1.0 to 2.

0.

4. The layered hydroxide is a layered double hydroxide, wherein the divalent metal element (Md) in the general formula (I) is Mg, Cu, Ni, Zn, Fe, or Mn, the trivalent metal element (Me) is Al, Fe, Mn, Cr, or Co, and the anion (A ｍ－ ) is CO ３ ２－ , O.H. － , Cl － , NO ３ － , S.O. ４ ２－ , F － , P.O. ｓ ｍ－ (s is an integer) or Fe(CN ６ ) ３－ The resource recovery method according to claim 3, wherein 5. The layered hydroxide is a layered hydroxide of a divalent metal, wherein the metal element (Mf) in the general formula (II) is Cu or Zn, and the anion (D ｃ－ ) is Cl － , O.H. － , C.H. ３ COO － , NO ３ － , S.O. ４ ２－ , CO ３ ２－ or P.O. ｔ ｃ－ The resource recovery method according to claim 3, wherein t is an integer.

6. The layered hydroxide is a layered rare earth hydroxide, wherein the rare earth element (RE) in the general formula (III) is Y and the anion (X － ) is Cl － ,Br － , NO ３ － or CH ３ COO － The resource recovery method according to claim 3, wherein 7. The layered hydroxide is Mg ６ Al ２ (CO ３ ) (OH) １６ ・4H ２ O, Zn ５ (OH) ８ Cl ２ ・H ２ O or Zn(OH) ８ (OCOCH ３ ) ２ ・2H ２ The resource recovery method according to claim 1, wherein O is the total amount of the raw material.

8. The resource recovery method according to claim 1, wherein the layered hydroxide is subjected to heat treatment at a temperature of 400 to 650°C.

9. The resource recovery method according to claim 1, wherein the acid treatment step is a step of heating the cleaning solution to which the acid has been added in a sealed container.

10. The resource recovery method according to claim 1, wherein the heating temperature in the acid treatment step is 80 to 100°C.

11. The resource recovery method according to any one of claims 1 to 10, further comprising the steps of: recovering a precipitate formed by the addition of the layered hydroxide; and recovering a fluorine compound from the washing liquid remaining after the precipitate has been recovered.

12. The resource recovery method according to any one of claims 1 to 10, wherein the pretreatment applied to the layered hydroxide further comprises intercalating the heat-treated layered hydroxide with monovalent anions.

13. The monovalent anion intercalated in the layered hydroxide is CH ３ COO － , Cl － Or NO ３ － The resource recovery method according to claim 12, wherein 14. The monovalent anion intercalated in the layered hydroxide is CH ３ COO － The resource recovery method according to claim 12, wherein 15. The resource recovery method according to claim 12, further comprising a step of recovering the precipitate formed by the addition of the layered hydroxide.

16. The resource recovery method according to claim 15, further comprising a step of recovering fluorine compounds from the washing liquid obtained after recovering the precipitate.

17. A resource recycling method, comprising the step of immersing the sediment recovered by the resource recovery method according to claim 15 in a liquid.

18. The resource recycling method according to claim 17, wherein the liquid in which the precipitate is immersed has a pH of 8.0 or higher.

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