Metal ion extraction method

Abstract

The present invention provides a metal ion extraction method for extracting metal ions of at least one type into an oil phase by merging an aqueous phase containing two or more types of metal ions with an oil phase containing an extraction agent in mid-circulation, mixing both phases, and then separating the phases, the separation of the two phases being performed on the phases in a mixed state in which, out of the two or more types of metal ions, the metal ions of the at least one type to be extracted are in extraction equilibrium while the remaining metal ions are in non-extraction equilibrium.

Description

Method for extracting metal ions

[0001] The present invention relates to a method for extracting metal ions.

[0002] Valuable metals such as precious metals and rare earth metals are essential elements for precision equipment, and ensuring a stable supply and availability of high-purity metals is a major challenge. These valuable metals are typically mined as mixtures with two or more other metals, requiring isolation and purification (high-purity extraction) of the desired metal from the mining mixture. Furthermore, the amount of valuable metals that can be extracted from mines is limited, making the stable supply of precious metals, essential for precision equipment, a significant challenge. Therefore, technologies for recovering valuable metals from industrial waste without relying on mining are gaining importance. In particular, with the spread of electric vehicles, the amount of lithium-ion battery (LiB) waste is increasing year by year. LiBs use positive electrode active materials containing metallic elements such as cobalt and nickel, and the demand for cobalt, nickel, and manganese is expected to increase significantly. To meet this increased demand for valuable metals, it is desirable not only to increase mining volume but also to establish metal recycling technologies from waste LiBs.

[0003] Wet extraction (solvent extraction) is widely used as a method for isolating and purifying target valuable metals from mining mixtures and as a method for recycling metals from waste. In wet extraction, an organic phase containing a metal extractant is brought into contact with an aqueous solution (aqueous phase) containing metal element ions (simply called "metal ions"), mixed, and allowed to stand to separate the two phases. The metal ions to which the metal extractant is coordinated then move (extract) into the organic phase (oil phase). By removing this organic phase, the metal ions are back-extracted, and if necessary, purified, it becomes possible to isolate and purify the target metal and recycle it as (high-purity) metal.

[0004] In such wet extraction methods, typically, all metal ions in the aqueous phase are brought to extraction equilibrium, and then specific metal ions are extracted by setting conditions such as selecting an extractant and adjusting the pH. For example, when separating a specific metal ion from two or more metal ions in the aqueous phase, it is important to extract a large amount of the specific metal ion (high extraction yield) into the organic phase, while extracting a small amount of the remaining metal ions (extraction suppression), that is, to perform selective extraction of the specific metal ion.

[0005] As an example of a wet extraction method for metal ions, Patent Document 1 proposes a method for separating and recovering metals from a sulfuric acid solution containing molybdenum, vanadium, aluminum, cobalt, and nickel, using a phosphonic acid monoester as the extractant and a shaking method (batch type), using a sulfuric acid solution obtained by dissolving a spent desulfurization catalyst used to remove sulfur components from crude oil as the treatment target. In this separation and recovery method, as one of the separation and extraction steps for each metal, it is noted that the extraction of aluminum is extremely slow, and it is expected that aluminum can be effectively separated from vanadium and molybdenum in a relatively short time (for example, 4 hours). Furthermore, Patent Document 2 describes an extraction method using a multi-stage mixer settler, in which, in each stage of the extraction process, a specific component, in the example, copper ions or trivalent metal ions M, are extracted. ３＋ An extraction method has been proposed in which the extraction process separates into phases before reaching extraction equilibrium.

[0006] Japanese Patent Publication No. 09-235628 Japanese Patent Publication No. 2016-019939

[0007] The separation and extraction method described in Patent Document 1 is a batch extraction method using a shaker, and therefore requires a long time to separate and extract a specific metal ion from two or more metal ions. For example, as mentioned above, the separation of aluminum from vanadium and molybdenum requires a shaking time (mixing time) of up to four hours. Moreover, as described in Patent Document 2, batch extraction methods generally require a long time for phase separation after mixing. Therefore, in batch extraction methods, from the viewpoint of productivity, cost, and the realization of industrialization, it is desirable to achieve the extraction and separation process (mixing process and phase separation process) in a shorter time.

[0008] As mentioned above, in conventional wet extraction methods, it is common to extract specific metal ions when the extraction equilibrium for metal ions has been reached. However, in the extraction method described in Patent Document 2, it is proposed to deliberately separate the phase of specific metal ions before reaching extraction equilibrium, with the aim of improving the time efficiency of the extraction process. However, Patent Document 2 describes Cu ions and trivalent metal ions M. ３＋ Patent Document 1 and 2 only describe a method for extracting one type of metal ion, and do not discuss any method for separating and extracting a specific metal ion from two or more types of metal ions. Even if two or more types of metal ions are used in the extraction method of Patent Document 2, in order to achieve the objective of shortening the phase separation time, it is important that each metal ion separates before reaching extraction equilibrium. Thus, Patent Documents 1 and 2 do not discuss any extraction method for extracting a specific metal ion from two or more types of metal ions in a short time.

[0009] The object of this invention is to provide a method for extracting metal ions that can selectively extract a specific metal ion from two or more metal ions, even in a short amount of time.

[0010] In conventional wet extraction methods, as described above, it is common practice to extract a specific metal ion after all metal ions in the aqueous phase have reached extraction equilibrium. The inventors concluded that, even with consideration and improvement of normal extraction conditions such as the selection of extractants and pH adjustment during mixing, it is not easy to selectively extract a specific metal ion from two or more metal ions in a short time using such a general wet extraction method. Therefore, the inventors diligently investigated wet extraction methods and conceived the idea that if a specific metal ion from two or more metal ions is brought to extraction equilibrium (equilibrium state) while the remaining metal ions are separated in a mixed state before reaching extraction equilibrium (non-equilibrium state), the amount of remaining metal ions extracted can be suppressed, and as a result, a specific metal ion can be selectively extracted in a short time. Based on this idea, the inventors continued their research and found that by employing a flow-type extraction method, the two phases in a mixed state can be rapidly separated. This allows for phase separation while maintaining a mixed state of equilibrium for a specific metal ion and a non-equilibrium state for the remaining metal ions among two or more metal ions. As a result, they discovered that a specific metal ion can be extracted from two or more metal ions in a short time and with high selectivity. The present invention was completed after further research based on these findings.

[0011] In other words, the above problems were solved by the following means: <1> A method for extracting metal ions, comprising combining an aqueous phase containing two or more metal ions and an oil phase containing an extractant during flow, mixing the two phases, and then separating the phases to extract at least one metal ion into the oil phase, wherein the two or more metal ions are separated in a mixed state in which at least one metal ion to be extracted is in extraction equilibrium and the remaining metal ions are in non-extraction equilibrium. <2> The method for extracting metal ions according to <1>, wherein the mixing of the two phases is performed at 15 to 95°C. <3> The method for extracting metal ions according to <1> or <2>, wherein the liquid residence time from the start of mixing of the two phases to the end of phase separation is within 5 minutes. <4> The method for extracting metal ions according to any one of <1> to <3>, wherein the aqueous phase and the oil phase are combined by utilizing collisions between the respective phases in flow. <5> A method for extracting metal ions according to any one of <1> to <4>, wherein the flow rate of at least one of the aqueous phase and the oil phase is 6.0 to 30 mL / min. <6> A method for extracting metal ions according to any one of <1> to <5>, wherein the two phases are merged with a reduction ratio of the flow diameter of at least one of the aqueous phase and the oil phase of 0.05 to 0.9. <7> The kinetic energy per unit area and per unit time of at least one of the aqueous phase and the oil phase is 10 to 3.5 × 10 ２ J / sec / m ２ A method for extracting metal ions according to any one of <1> to <6>, wherein the two phases are set to merge. <8> A method for extracting metal ions according to any one of <1> to <7>, wherein the aqueous phase and the oil phase are flowed in a mixed state for a distance of 10 cm to 2 m. <9> A method for extracting metal ions according to any one of <1> to <8>, wherein the extractant is an acidic extractant. <10> A method for extracting metal ions according to <9>, wherein the acidic extractant contains a phosphoric acid compound. <11> A method for extracting metal ions according to <9> or <10>, wherein the acidic extractant is represented by the following formula (I). (Formula I), R １ and R ２ represents a substituent, at least one of which is a hydrocarbon group having 9 or more carbon atoms. X represents -OH or -SH. Y represents an oxygen atom or a sulfur atom. Z １ and Z ２represents a single bond, -O-, -NH-, or -S-.

[0012] The present invention provides a method for extracting metal ions that can selectively extract a specific metal ion from two or more metal ions, even in a short amount of time. The above and other features and advantages of the present invention will become clearer from the following description, with reference to the accompanying drawings as appropriate.

[0013] Figure 1 is a schematic front view showing an example of an extraction apparatus suitably used in the metal ion extraction method of the present invention. Figure 2 is a schematic front view showing another example of an extraction apparatus suitably used in the metal ion extraction method of the present invention. Figure 3 shows a modified example of a flow tube used in an extraction apparatus suitably used in the metal ion extraction method of the present invention.

[0014] In this invention, when describing the content, physical properties, etc., of components by indicating numerical ranges, if the upper and lower limits of the numerical range are described separately, either upper or lower limit can be appropriately combined to form a specific numerical range. On the other hand, when describing multiple numerical ranges represented by "~", the upper and lower limits forming the numerical range are not limited to the specific combination of upper and lower limits described before and after "~" as a specific numerical range, but can be a numerical range formed by appropriately combining the upper and lower limits of each numerical range. In this invention, a numerical range represented by "~" means a range that includes the values ​​described before and after "~" as the lower and upper limits. In this invention, the designation of a compound (for example, when referring to it with "compound" at the end) includes not only the compound itself, but also its salts and ions. It also includes derivatives in which parts have been altered, such as by introducing substituents, to the extent that the effects of this invention are not impaired. In the present invention, substituents, linking groups, etc. (hereinafter referred to as substituents, etc.) that are not explicitly stated as substituted or unsubstituted may have appropriate substituents. Therefore, in the present invention, even when simply referred to as a YYY group, this YYY group includes not only an unsubstituted form but also a further substituted form. The same applies to compounds that are not explicitly stated as substituted or unsubstituted. Preferred substituents include, for example, groups selected from substituent G described later. In the present invention, when there are multiple substituents, etc. indicated by a specific symbol, or when multiple substituents, etc. are specified simultaneously, it means that each substituent, etc. may be the same as or different from the others. Furthermore, even if not specifically stated, when multiple substituents, etc. are adjacent to each other, they may be linked to each other or fused to form a ring.

[0015] In this specification, "metallic elements belonging to different groups in the periodic table" are referred to as "heterogroup metallic elements," and "heterogroup metallic elements of the same period in the periodic table" are sometimes referred to as "same-period heterogroup metallic elements." Furthermore, "ions of heterogroup metallic elements" and "ions of heterogroup metallic elements of the same period" are sometimes referred to as "heterogroup metallic ions" and "same-period heterogroup metallic ions," respectively. In this invention, unless otherwise specified, "ppm" indicating content, etc., is based on mass and represents "mass ppm."

[0016] [[Method for Extracting Metal Ions of the Present Invention]] The method for extracting metal ions of the present invention (hereinafter sometimes referred to as "the extraction method of the present invention") relates to a flow-type wet extraction method in which an aqueous phase containing metal ions and an oil phase containing an extractant are combined during flow, mixed while flowing, and then phase-separated into an aqueous phase and an oil phase, thereby extracting the metal ions into the oil phase. The extraction method of the present invention, by performing the extraction operations described later (for example, each step described later) using the aqueous phase and oil phase described later in a flow-type wet extraction method, makes it possible to move (extract) at least one specific metal ion from two or more metal ions present in the aqueous phase to the oil phase with high selectivity and in a short time. The method for extracting metal ions of the present invention will be described with reference to an apparatus suitably used in the extraction method of the present invention.

[0017] [Extraction apparatus suitably used in the extraction method of the present invention] The extraction apparatus suitably used in the extraction method of the present invention (hereinafter sometimes referred to as "extraction apparatus suitable for the present invention") is not particularly limited, but for example, it has an aqueous phase flow pipe connected to an aqueous phase storage tank and for flowing (transferring) the aqueous phase to a confluence located downstream of the aqueous phase storage tank in the flow direction; an oil phase flow pipe connected to an oil phase storage tank and for flowing (transferring) the oil phase to a confluence located downstream of the oil phase storage tank in the flow direction; a confluence connected to the downstream side of the aqueous phase flow pipe and the oil phase flow pipe in the flow direction; a mixing section (mixing flow pipe) extending from the confluence section; a pH adjusting agent transfer pipe connecting a pH adjusting agent-containing aqueous solution storage tank and the mixing section or confluence section for flowing (transferring) the pH adjusting agent-containing aqueous solution from the pH adjusting agent-containing aqueous solution storage tank to the mixing section or confluence section; and a separation section connected to the downstream side of the mixing section in the flow direction. Here, the aqueous phase storage tank, aqueous phase flow pipe, oil phase storage tank, oil phase flow pipe, confluence section, mixing section, pH adjusting agent-containing aqueous solution storage tank, pH adjusting agent transfer pipe, and separation section can be the same as the configuration, arrangement, etc., of the aqueous phase storage tank, aqueous phase flow pipe, oil phase storage tank, oil phase flow pipe, confluence section, mixing section, pH adjusting agent-containing aqueous solution storage tank, pH adjusting agent transfer pipe, and separation section in the extraction apparatus 1 or 2 described later. In this apparatus, each step of the extraction method of the present invention can be suitably carried out. Hereinafter, the upstream side and the downstream side with respect to the flow direction of the oil phase, aqueous phase, or combined liquid may be simply referred to as the downstream side and the upstream side, respectively.

[0018] <Extraction device 1> As shown in Figure 1, the extraction device 1 includes a water phase storage tank 5 for containing and storing the water phase, a water phase flow pipe 11 connected to the water phase storage tank 5 and for the water phase to flow to a confluence 13 located downstream of the water phase in the flow direction from the water phase storage tank 5, an oil phase storage tank 6 for containing and storing the oil phase, and an oil phase flow pipe 12 connected to the oil phase storage tank 6 and for the oil phase to flow to a confluence 13 located downstream of the oil phase in the flow direction from the oil phase storage tank 6. Extraction apparatus 1, an example of an extraction apparatus suitable for the present invention, is suitable as an extraction apparatus for suitably carrying out an extraction method in which, among the extraction methods of the present invention described later, the following steps are performed in order: first, a step of combining the aqueous phase and the oil phase and continuing to flow; second, a step of combining the combined two-liquid solution with an aqueous solution containing a pH adjuster and continuing to flow; and third, a step of separating the combined three-liquid solution in a mixed state in which at least one metal ion to be extracted is in extraction equilibrium (after reaching extraction equilibrium) and the remaining metal ions are in non-extraction equilibrium (before reaching extraction equilibrium). The aqueous phase storage tank 5 and the oil phase storage tank 6 each only need to have a capacity that allows the extraction method (extraction and separation cycle) of the present invention to be carried out in a flow manner, and their capacities can be set to appropriate capacities according to the extraction conditions, etc.

[0019] As shown in Figure 1, the extraction device 1 has a water phase flow pipe 11 and an oil phase flow pipe 12 arranged opposite each other in a straight line, and has a confluence section 13 that connects the open end of the tapered section 11a and the open end of the tapered section 12a to merge the two phases. Here, the water phase flow pipe 11 has a tapered section 11a on the downstream side (confluence section 13 side) in the flow direction of the water phase, and the oil phase flow pipe 12 has a tapered section 12a on the downstream side (confluence section 13 side) in the flow direction of the oil phase. In this way, the water phase flow pipe 11 and the oil phase flow pipe 12 have their inner diameters reduced towards the downstream side by the tapered sections 11a and 12a, respectively, and depending on the shape of each tapered section, the opening diameter of the open end of each tapered section is smaller (narrower diameter) than the inner diameter of the upstream opening end of each tapered section (the connection part with a flow pipe having a constant inner diameter). The cross-sectional shape perpendicular to the centerline of each flow pipe 11 and 12 and the tip sections 11a and 12a is not particularly limited, and various shapes, such as circular, elliptical, semicircular, polygonal, etc., can be adopted. The constant inner diameter of each flow pipe 11 and 12 (the inner diameter of the upstream opening end of the tip section) is not particularly limited and can be determined as appropriate, for example, it can be 0.1 to 100 mm, and it is preferable to set it to 0.5 to 10 mm in order to improve the mixing state. The flow diameter (inflow diameter) of the water phase and oil phase flowing from each flow pipe 11 and 12 into the confluence section 13 is reduced by the tip sections 11a and 12a compared to the flow diameter of the water phase and oil phase flowing through each flow pipe 11 and 12. At this time, the ratio of the inner diameter of the opening end of the tip section to a constant inner diameter in each flow pipe 11 and 12 (inner diameter of the opening end of the tip section / inner diameter of the connection part with the constant inner diameter of the flow pipe) is not particularly limited and is determined appropriately according to the flow speed, etc., and is preferably the same as the reduction ratio of the flow diameters of both phases described later. The inner diameters of the water phase flow pipe 11 and the oil phase flow pipe 12 may be different, but it is preferable that they be set to be the same. Furthermore, the inner diameters of the opening ends of the tip section 11a and 12a, and the reduction ratio of the inner diameter of the tip section 11a (the ratio of the above inner diameters) and the reduction ratio of the inner diameter of the tip section 12a may be different, but are usually set to be the same considering the mixing state, etc. In the present invention, inner diameter refers to equivalent diameter, which will be described in detail later.

[0020] The aqueous phase flow pipe 11 and the oil phase flow pipe 12 are usually provided with a transfer mechanism (not shown in Figure 1) for circulating (transferring) the aqueous phase or the oil phase. The transfer mechanism is not particularly limited as long as it can circulate the aqueous phase or the oil phase, and various types of pumps can be used.

[0021] Furthermore, the extraction device 1 has a tubular mixing section 14 that extends from the confluence section 13 in a direction approximately perpendicular to the aqueous phase flow pipe 11, and a pH adjusting agent transfer pipe 15 is connected to the middle of the mixing section 14 to transfer the pH adjusting agent-containing aqueous solution from the pH adjusting agent-containing aqueous solution storage tank 7 to the mixing section 14. The mixing section 14 has a tapered section (reverse taper section) whose inner diameter gradually increases downstream from the connection point with the confluence section 13. The dimensions of this tapered section are not particularly limited and can be set as appropriate, for example, they can be the same ratio as the reduction ratio of the flow diameters of both phases, which will be described later. The mixing section 14 is divided into a pre-mixing section 14a from the connection point with the confluence section 13 to the connection point with the pH adjusting agent transfer pipe 15, and a post-mixing section 14b from the connection point with the pH adjusting agent transfer pipe 15 to the connection point with the separation section 16. The pH adjusting agent-containing aqueous solution storage tank 7 is a tank that contains and stores the pH adjusting agent-containing aqueous solution, and the pH adjusting agent transfer pipe 15 connects the pH adjusting agent-containing aqueous solution storage tank 7 and the mixing unit 14, and flows the pH adjusting agent-containing aqueous solution from the pH adjusting agent-containing aqueous solution storage tank 7 to the mixing unit 14 located downstream in the flow direction of the pH adjusting agent-containing aqueous solution. The pH adjusting agent-containing aqueous solution storage tank 7 only needs to have a capacity that allows the extraction method (extraction and separation cycle) of the present invention to be carried out in a flow manner, and is set to an appropriate capacity depending on the extraction conditions, etc. In addition, the pH adjusting agent transfer pipe 15 is usually provided with the above-mentioned transfer mechanism (not shown in Figure 1) for flowing (transferring) the pH adjusting agent-containing aqueous solution. The inner diameters of the mixing unit 14, pH adjusting agent transfer pipe, etc. can be set within the above range that can be taken as a constant inner diameter in each flow pipe 11 and 12.

[0022] The extraction apparatus 1 preferably has a heating device (not shown in Figure 1) in at least the downstream mixing section 14b that heats the three-liquid confluence. The extraction apparatus 1 may further have a heating device (not shown in Figure 1) in at least one of the following: the aqueous phase flow pipe 11 (especially the downstream portion such as the tip section 11a), the oil phase flow pipe 12 (especially the downstream portion such as the tip section 12a), the confluence section 13, the upstream mixing section 14a, and the pH adjusting agent transfer pipe 15 (especially the downstream portion such as the tip section) that heats the aqueous phase, oil phase, pH adjusting agent-containing aqueous solution, and confluence. The heating device can be any device capable of heating to a temperature higher than at least one of the temperatures of the aqueous phase stored in the aqueous phase storage tank 5, the oil phase stored in the oil phase storage tank 6, and, as appropriate, the pH adjusting agent-containing aqueous solution stored in the pH adjusting agent-containing aqueous solution storage tank 7. For example, various known heating devices such as heaters, electric heating tubes, jackets containing a heating medium, aluminum block heaters, water baths, oil baths, and microwave heating devices can be used.

[0023] Furthermore, the extraction device 1 has a separation unit 16 connected to the downstream end in the flow direction of the mixing unit 14, which allows the incoming three-liquid mixture to stand and separate into an aqueous phase and an oil phase. The separation unit 16 can be made of a general storage container, separation column, settler, separatory funnel, etc., and has an oil phase discharge pipe 16a for discharging the phase-separated oil phase and an aqueous phase discharge pipe 16b for discharging the phase-separated aqueous phase. Valves and transfer means, such as various pumps, may be interposed in the oil phase discharge pipe 16a and the aqueous phase discharge pipe 16b, respectively. The separation unit 16 may be equipped with various known heating devices.

[0024] In the extraction apparatus 1, it is preferable to install a static mixer in at least one of the flow paths of the pre-mixing section 14a and the post-mixing section 14b in the mixing section 14, and it is even more preferable to install the static mixer in the flow path of the post-mixing section 14b in order to further improve the mixing state of the three-liquid combined liquid.

[0025] A static mixer is a stationary mixer without a drive unit. It mixes a fluid that enters the mixer by sequentially dividing, rejoining, and reversing its direction using stationary mixing elements installed inside the mixer. Examples of static mixers include the Sulzer type, Kenix type, Toray type, and Noritake Company type. A static mixer preferably has four or more mixing elements, and more preferably has six to thirty. These mixing elements are preferably arranged continuously in a mixer tube with a length of 10 cm to 2 m. Alternatively, multiple static mixers of this configuration can be arranged in series. In this case, the entire series-arranged static mixers form a single unit, which constitutes the static mixer of this invention. The size of the static mixer used in this invention is appropriately set according to the scale of production, etc. For example, the equivalent diameter inside the tube of the static mixer can be 1 to 100 mm. Even if the internal cross-section of the static mixer is larger than that of the flow pipe, the flow pipe and the static mixer can be connected via a connecting tube or the like. The length of the static mixer can be approximately 5 mm to 20 m. When multiple static mixers are arranged in series, the above length refers to the total length of the multiple static mixers arranged in series (including the spacing between static mixers). When multiple static mixers are arranged in series, the spacing between adjacent static mixers can be appropriately set considering the difference between the internal cross-section of the static mixer and the internal cross-section of the reaction channel connected to it. For example, the spacing between adjacent static mixers can be 100 cm or less, 70 cm or less, 40 cm or less, 20 cm or less, or 10 cm or less.

[0026] Examples of materials for static mixers include perfluoroalkoxyalkanes (PFA), Teflon (registered trademark), aromatic polyetherketone resins, stainless steel, copper or copper alloys, nickel or nickel alloys, titanium or titanium alloys, quartz glass, lime soda glass, etc. From the viewpoint of flexibility and chemical resistance, PFA, Teflon (registered trademark), stainless steel, nickel alloys, or titanium are preferred.

[0027] In the extraction apparatus 1, a three-way pipe having (formed) terminal sections 11a and 12a, such as a T-tube or Y-tube, can be used as the aqueous phase flow pipe 11, the oil phase flow pipe 12, the confluence section 13, and the mixing section 14. In the extraction apparatus 1, the aqueous phase flow pipe 11, the oil phase flow pipe 12, the confluence section 13, and the pre-mixing section 14a may be referred to as the "oil-water mixing section," and the pH adjusting agent transfer pipe 15 and the post-mixing section 14b may be referred to as the "pH adjusting section."

[0028] <Extraction device 2> As shown in Figure 2, the extraction device 2 includes a water phase storage tank 5 for containing and storing the water phase, a water phase flow pipe 11 connected to the water phase storage tank 5 and for the water phase to flow to a confluence 23 located downstream of the water phase in the flow direction from the water phase storage tank 5, an oil phase storage tank 6 for containing and storing the oil phase, an oil phase flow pipe 12 connected to the oil phase storage tank 6 and for the oil phase to flow to a confluence 23 located downstream of the oil phase in the flow direction from the oil phase storage tank 6, a pH adjusting agent-containing aqueous solution storage tank 7 for storing the pH adjusting agent-containing aqueous solution, and a pH adjusting agent transfer pipe 15 connected to the pH adjusting agent-containing aqueous solution storage tank 7 and for the pH adjusting agent-containing aqueous solution to flow to a confluence 23 located downstream of the pH adjusting agent-containing aqueous solution in the flow direction from the pH adjusting agent-containing aqueous solution storage tank 7. This extraction device 2 has basically the same configuration as extraction device 1, except that the pH adjusting agent transfer pipe 15 is connected to the junction 23. However, the mixing section 24 of extraction device 2 is not divided into a pre-mixing section 14a and a post-mixing section 14b, unlike the mixing section 14 of extraction device 1.

[0029] Another example of an extraction apparatus suitable for the present invention, Extraction Apparatus 2, is suitable as an extraction apparatus for carrying out an extraction method in which, among the extraction methods of the present invention described later, the process of combining the aqueous phase and the oil phase and continuing to pass the mixture together, and then combining the two-liquid mixture with an aqueous solution containing a pH adjuster and continuing to pass the mixture together, is carried out in a single step.

[0030] In the extraction apparatus 2, the aqueous phase storage tank 5, the oil phase storage tank 6, and the pH adjusting agent-containing aqueous solution storage tank 7 are the same as those in the extraction apparatus 1.

[0031] As shown in Figure 2, the extraction apparatus 2 has a pH adjusting agent transfer pipe 15 positioned at approximately a right angle to the aqueous phase flow pipe 11 and oil phase flow pipe 12, which are arranged on the same line, and has a confluence section 23 that connects the open end of the tapered section 11a, the open end of the tapered section 12a, and the open end of the pH adjusting agent transfer pipe 15 to combine the aqueous phase, oil phase, and pH adjusting agent-containing aqueous solution. Here, the aqueous phase flow pipe 11 has a tapered section 11a on the downstream side (confluence section 23 side) in the flow direction of the aqueous phase, the oil phase flow pipe 12 has a tapered section 12a on the downstream side (confluence section 13 side) in the flow direction of the oil phase, and the pH adjusting agent transfer pipe 15 may also have a tapered section on the downstream side (confluence section 23 side) in the flow direction of the pH adjusting agent-containing aqueous solution. Here, the aqueous phase flow pipe 11 and oil phase flow pipe 12 are the same as the aqueous phase flow pipe 11 and oil phase flow pipe 12 of the extraction apparatus 1. For example, the water phase flow pipe 11 and the oil phase flow pipe 12 have their inner diameters reduced downstream by the terminal sections 11a and 12a, respectively. Depending on the shape of each terminal section, the opening diameter of the opening end of each terminal section is smaller than the inner diameter of the upstream opening end of each terminal section (the connection point with the flow pipe having a constant inner diameter). The flow diameter (inflow diameter) of the water phase and oil phase flowing from each flow pipe 11 and 12 into the confluence section 23 is reduced by the terminal sections 11a and 12a compared to the flow diameter of the water phase and oil phase flowing through each flow pipe 11 and 12. The ratio of the inner diameter of the opening end of the terminal section to the constant inner diameter of each flow pipe 11 and 12 (inner diameter of the opening end of the terminal section / inner diameter of the connection point with the constant inner diameter terminal section in the flow pipe) is not particularly limited and is determined appropriately according to the flow velocity, etc., and is preferably the same as the reduction ratio of the flow diameters of both phases described later. Furthermore, the pH adjusting agent transfer tube 15 is identical to the pH adjusting agent transfer tube 15 of the extraction device 1, except for the connection position.

[0032] Furthermore, the extraction device 2 has a mixing section 24 that extends from the confluence section 23 along the flow direction extension of the pH adjusting agent transfer pipe 15. The mixing section 24 has a tapered section (reverse taper section) whose inner diameter gradually increases toward the downstream side in the flow direction from the connection point with the confluence section 23. Preferably, the extraction device 2 has a heating device (not shown in Figure 2) in at least the mixing section 24 for heating the three-liquid confluence liquid. In the extraction device 2, a heating device may further be provided in at least one of the following: the aqueous phase flow pipe 11 (especially the downstream portion such as the tapered end 11a), the oil phase flow pipe 12 (especially the downstream portion such as the tapered end 12a), the confluence section 23, and the pH adjusting agent transfer pipe 15 (especially the downstream portion such as the tapered end) for heating the aqueous phase, oil phase, pH adjusting agent-containing aqueous solution, and confluence liquid. The heating device can be any device capable of heating to a temperature higher than at least one of the temperatures of the aqueous phase stored in the aqueous phase storage tank 5, the oil phase stored in the oil phase storage tank 6, and the pH adjusting agent-containing aqueous solution stored in the pH adjusting agent-containing aqueous solution storage tank 7, as described above.

[0033] Furthermore, the extraction device 2 is connected to the downstream end of the mixing unit 24 in the flow direction and has a separation unit 16 that allows the incoming three-liquid mixture to stand and separates it into an aqueous phase and an oil phase. This separation unit 16 has the same configuration as the separation unit 16 of the extraction device 1.

[0034] In the extraction apparatus 2, it is preferable to install a static mixer in the flow path of the mixing section 24 in order to greatly improve the mixing state of the three-liquid combined liquid. The static mixer is as described in the extraction apparatus 1. In the extraction apparatus 2, a four-sided pipe having (formed) tapered ends 11a and 12a, such as a cross pipe, can be used as the aqueous phase flow pipe 11, the oil phase flow pipe 12, the pH adjusting agent transfer pipe 15, the confluence section 23, and the mixing section 24. This extraction apparatus 2 is preferable in that the flow path length of the mixing section 24 can be shortened. In addition, in the extraction apparatus 2, the configuration of the aqueous phase flow pipe 11, the oil phase flow pipe 12, the pH adjusting agent transfer pipe 15, the confluence section 23, and the mixing section 24 also serves as the "oil-water mixing section" and the "pH adjustment section" of the extraction apparatus 1, and is sometimes referred to as the "oil-water mixing pH adjustment section".

[0035] In extraction devices 1 and 2, the aqueous phase flow pipe 11 and the oil phase flow pipe 12 are configured such that their inner diameter decreases (shrinks) toward the downstream side due to the tapered sections 11a and 12a. However, in an extraction device suitable for the present invention, the aqueous phase flow pipe and the oil phase flow pipe are not limited to having tapered sections. For example, as shown in Figure 3, pipes connected to a large diameter section 11b and a small diameter section 11c can be used. Similarly, the pH adjusting agent transfer pipe 15 is configured such that its inner diameter decreases (shrinks) toward the downstream side due to the tapered section. However, in an extraction device suitable for the present invention, the pH adjusting agent transfer pipe is not limited to having tapered sections. For example, it may be composed of a pipe with a constant inner diameter. In the present invention, a constant inner diameter means not only having exactly the same inner diameter, but also having an inner diameter ratio [maximum inner diameter / minimum inner diameter] greater than 1.0 and less than or equal to 1.1. Furthermore, in extraction devices 1 and 2, the flow pipes connected to the confluence section 13 or 23 are arranged at an angle that is approximately right-angle. However, in an extraction device suitable for the present invention, the angle of the pipes connected to the confluence section is not particularly limited. For example, a double pipe or a pipe with two internal flow paths can be used as the aqueous phase flow pipe and the oil phase flow pipe. In this case, the arrangement of the two pipes will be parallel, and the confluence angle between the flowing aqueous phase and oil phase will be small, approximately 0°. In the extraction method of the present invention, it is preferable to set the arrangement angle between the aqueous phase flow pipe and the oil phase flow pipe (the confluence angle between the aqueous phase and the oil phase) to a certain angle, in order to improve the mixing state due to the impact generated when the two phases merge due to collision. Specifically, this is the same as the confluence angle described later.

[0036] Although extraction apparatuses 1 and 2 are equipped with a pH adjusting agent-containing aqueous solution storage tank 7 and a pH adjusting agent transfer pipe 15, when using aqueous and / or oil phases to which a pH adjusting agent-containing aqueous solution has been pre-added in an amount that results in a predetermined pH at the time of mixing, the extraction apparatus used in the present invention does not need to be equipped with a pH adjusting agent-containing aqueous solution storage tank 7 and a pH adjusting agent transfer pipe 15. The amount added to achieve a predetermined pH at the time of mixing can be appropriately determined by the content of metal ions, the concentration of the pH adjusting agent-containing aqueous solution, the pH set for the metal ions, etc.

[0037] [Fluids used in the extraction method of the present invention] In the extraction method of the present invention, fluids consisting of an aqueous phase, an oil phase, and an aqueous solution containing a pH adjusting agent are prepared. <Aqueous phase> The water forming the aqueous phase is not particularly limited, but (ultra)pure water, ion-exchanged water, etc. can be used.

[0038] In the present invention, the aqueous phase contains at least two types of metal ions. The number of types of metal ions in the aqueous phase is not particularly limited as long as there are two or more types, for example, it can be 2 to 15 types, preferably 2 to 8 types, and more preferably 2 to 5 types. The metal ions in the aqueous phase may contain ions of metal elements belonging to groups 1 to 14 of the periodic table, preferably metal ions belonging to groups 2 to 14, and may also contain metal ions belonging to groups 15 to 17. In the present invention, it is preferable to contain two or more types of metal ions belonging to groups 1 to 14, more preferably two or more types of metal ions belonging to groups 2 to 14, and even more preferable to contain at least one ion of a transition metal element (metal elements belonging to groups 3 to 12). In embodiments containing at least one transition metal element, it is preferable to contain two or more metal ions belonging to groups 2 to 12, more preferably two or more metal ions belonging to groups 4 to 12, even more preferably two or more metal ions belonging to groups 7 to 12, particularly preferably two or more metal ions belonging to groups 8 to 12, even more preferably two or more metal ions belonging to groups 9 to 12, and most preferably two or more metal ions belonging to groups 9 and 10. The metal ions belonging to each group are not particularly limited, but metal ions belonging to periods 3 to 6 of the periodic table are preferred, and metal ions belonging to periods 4 or 5 are more preferred.

[0039] The combination of multiple metal ions is not particularly limited, but examples of combinations of groups include combinations of Group 2 and Group 7, combinations of Group 7 and Group 10, combinations of Group 9 and Group 10, combinations of Group 9 and Group 12, combinations of Group 9 and Group 11, combinations of Group 9, Group 10 and Group 12, combinations of Group 4 and Group 9, combinations of Group 10 and Group 11, combinations of Group 7, Group 9 and Group 10, and combinations of Group 7, Group 8, Group 9 and Group 10. In the present invention, there may be two or more metal ions belonging to each group, but it is preferable to have one type in order to show high selectivity.

[0040] Specific combinations of metal ions include, for example, combinations containing Mg and Mn, combinations containing Mn and Ni, combinations containing Co and Ni, combinations containing Co and Zn, combinations containing Co and Cu, combinations containing Rh and Ni, combinations containing Zr and Rh, combinations containing Ni and Cu, combinations containing Mn, Co and Ni, and combinations with Mn, Fe, Co and Ni. The multiple metal ions contained in the aqueous phase may include metal ions of the same group or metal ions of different groups. The number of different metal ions contained in the aqueous phase may be two or more, preferably two to four, and more preferably two. In the embodiments containing each of the above transition metal elements and combinations of multiple metal ions, metal ions belonging to Group 13, particularly Al, may be included, but it is preferable that they are not included.

[0041] The metal elements belonging to each group are not particularly limited, and appropriate atoms can be used. For example, as the metal elements belonging to Group 1, Li, Na, Rb, and Cs are preferably mentioned. As the metal elements belonging to Group 2, Mg, Ca, Sr, and Ba are preferably mentioned. As the metal elements belonging to Group 3, Sc and Y are preferably mentioned. As the metal elements belonging to Group 4, Ti, Zr, and Hf are preferably mentioned. As the metal elements belonging to Group 5, V, Nb, and Ta are preferably mentioned. As the metal elements belonging to Group 6, Cr, Mo, and W are preferably mentioned. As the metal elements belonging to Group 7, Mn and Tc are preferably mentioned. As the metal elements belonging to Group 8, Fe, Ru, and Os are preferably mentioned. As the metal elements belonging to Group 9, Co, Rh, and Ir are preferably mentioned. As the metal elements belonging to Group 10, Ni, Pd, and Pt are preferably mentioned. As the metal elements belonging to Group 11, Cu, Ag, and Au are preferably mentioned. As the metal elements belonging to Group 12, Zn, Cd, and Hg are preferably mentioned. As the metal elements belonging to Group 13, Al, Ga, In, and Tl are preferably mentioned. As the metal elements belonging to Group 14, Ga, Sn, and Pb are preferably mentioned. As the metal elements belonging to Group 15, Sb and Bi are preferably mentioned. The metal elements belonging to Group 16 are not particularly limited, and Te is preferably mentioned.

[0042] The metal ions can be prepared as appropriate. For example, various metal salts (salts of inorganic acids such as nitric acid and sulfuric acid of typical elements or organic acids such as acetic acid), mixtures of mined metals (ions), recovered materials from metal wastes, other wastes, such as metal recovered materials from waste batteries (LiB), etc., and further mixtures thereof can be used. As the metal recovered materials from waste LiB, recovered materials by known methods, such as wet treatment and electrolysis, etc., can be mentioned.

[0043] The total content of metal ions in the aqueous phase is not particularly limited and is set as appropriate. For example, it can be 1.0×10 ３ ~1.0×10 ６ mass ppm, and can be 1.0×10 ３~1.0 x 10 ５ The mass is preferably ppm, and is 1.0 × 10 ３ ~8.0 x 10 ４ It is more preferable that the concentration be in ppm by mass. In particular, since the extraction method of the present invention can achieve a high extraction yield, the total content of metal ions in the aqueous phase can be set to a high level. The total content of metal ions belonging to groups 9 to 12 among the metal ions is not particularly limited and can be set as appropriate, for example, 1.0 × 10⁻¹⁶ ３ ~8.0 x 10 ４ The mass can be ppm, and it is 1.0 × 10 ３ ~5.0 x 10 ４ It is preferable that the mass be ppm. The total content of metal ions belonging to groups 1 to 8 and groups 13 to 17 among the metal ions is not particularly limited and can be set as appropriate, for example, 1.0 × 10 ３ ~6.0 x 10 ４ The mass can be ppm, and it is 1.0 × 10 ３ ~3.0 x 10 ４ It is preferable that the mass be ppm. The content of metal ions belonging to each group is not particularly limited and can be set as appropriate, for example, 1.0 × 10 ３ ~6.0 x 10 ４ The mass can be ppm, and it is 1.0 × 10 ３ ~5.0 x 10 ４ The mass is preferably ppm. If two or more metal ions belonging to each group are present, the total content of metal ions belonging to each group shall be used.

[0044] In the present invention, when the aqueous phase contains metal ions from different groups, the content of metal ions belonging to one group may be greater or less than the content of metal ions belonging to other groups. The extraction method of the present invention allows for highly selective separation and recovery of metal ions when the aqueous phase contains metal ions from different groups, so it is not necessary to set the content of metal ions belonging to different groups in a specific ratio. For example, the mass ratio of the content of metal ions belonging to one other group (e.g., metal ions extracted at the maximum extraction rate) to the content of metal ions belonging to a specific group (e.g., metal ions extracted at the maximum extraction rate) [content of metal ions belonging to a specific group: content of metal ions belonging to one other group] is, for example, 1.0 × 10⁻⁶. ２ : 1 to 1.0 x 10 ４ It can be done as 1.0 × 10 ２ : 10-5.0 x 10 ３ It is preferable to do so, 1.0 × 10 ２ : 50-1.0 x 10 ３ It is preferable to do so.

[0045] The pH of the aqueous phase is not particularly limited and can be set as appropriate, but considering the solubility of metal ions, the formation of complex ions, etc., it is preferably 0.1 to 10, and more preferably 2.0 to 9.0. The pH of the aqueous phase is usually set within the above range, but in the present invention, an aqueous solution containing a pH adjusting agent can also be added to the aqueous phase in any amount, or in an amount that results in a predetermined mixed pH when the aqueous phase and oil phase are mixed. In these cases, the pH of the aqueous phase may be outside the above range. The pH of the aqueous phase can be adjusted, for example, using an acid or alkali (an aqueous solution containing a pH adjusting agent including an acid or alkali). As the acid, any known acid can be used without particular limitation, and examples include inorganic acids such as sulfuric acid, hydrochloric acid, nitric acid, and phosphoric acid, and organic acids such as formic acid, acetic acid, oxalic acid, organic phosphoric acid, and organic sulfonic acid. As the alkali, any known alkali can be used without particular limitation, and examples include inorganic alkalis and organic alkalis, with inorganic alkalis being preferred. Examples of inorganic alkalis include metal alkalis such as hydroxides and carbonates of Group 1 or Group 2 metals, as well as aqueous ammonia and ammonium chloride. Examples of organic alkalis include organic ammonium salts.

[0046] The temperature of the aqueous phase (during storage and at the start of distribution) is not particularly limited and can be, for example, 10 to 60°C, or between 15°C and less than 40°C. The density of the aqueous phase (kg / m³) ３ The temperature (25°C) is not particularly limited and cannot be uniquely determined by the metal ion content, etc., but for example, 9.0 × 10 ２ ~2.0 x 10 ３ kg / m ３ This is, for example, the kinetic energy E, which will be discussed later. ＳＴ It is preferable in that it is easy to set the kinetic energy E to a suitable value. ＳＴ Setting this value to a suitable value is preferable because it allows for an increase in the amount of metal ions extracted.

[0047] The aqueous phase may, if necessary, contain ligands (compounds) that coordinate to metal ions or compounds that generate ligands. The aqueous phase can be prepared by dissolving metal ions in water. The preparation conditions for the aqueous phase are not particularly limited. For example, the preparation temperature can usually be 10 to 60°C, but it can be determined considering the solubility of metal ions, etc.

[0048] The aqueous phase may contain a masking agent in addition to the metal ions mentioned above. Known masking agents can be used without particular limitation. Examples include monodentate ligands such as ammonia and chelating agents such as dithizone. In the extraction method of the present invention, the extractant can coordinate to the metal ions on its own and extract these metal ions into the oil phase. Therefore, the aqueous and oil phases do not need to contain compounds that cooperate with the extractant to extract the metal ions, such as compounds that coordinate to the metal ions or compounds that generate ligands, such as known extractants. In the extraction method of the present invention, typically, an aqueous phase containing specific metal ions as essential components and an oil phase containing an extractant as an essential component are used.

[0049] <Oil Phase> The extraction method of the present invention uses an oil phase (organic phase) containing one or more extractants. The oil phase may contain an organic solvent. The organic solvent that the oil phase may contain is not particularly limited, and any suitable organic solvent can be used, but it is preferable to determine it considering the mixing temperature described later. Examples of organic solvents include alcohol solvents, ether solvents, hydrocarbon solvents (aromatic solvents, aliphatic solvents), halogen solvents, etc. Among these, hydrocarbon solvents are preferred, and various solvents that are components of petroleum are more preferred, with aromatic, paraffinic, naphthenic, kerosene, gasoline, naphtha, kerosene, and diesel fuel hydrocarbon solvents being even more preferred. As the organic solvent, any suitable organic solvent can be selected from the above, but C ｎ H （２ｎ＋２） One preferred embodiment is an organic solvent that is neither a hydrocarbon solvent containing aliphatic hydrocarbons represented by (n being an integer between 19 and 40) nor an edible oil.

[0050] The extractant is not particularly limited as long as it exhibits solubility in organic solvents, is present in the oil phase, coordinates with metal ions present near the interface between the aqueous and oil phases, and has the function of moving these metal ions to the oil phase. An extractant can be appropriately selected and used from among various known metal extractants. In the present invention, solubility in organic solvents means the property that the extractant can dissolve in organic solvents at the content described later. As for the extractant, it is preferable to use an acidic extractant, which can extract a specific metal ion from two or more metal ions with high selectivity, more preferably an acidic extractant selected from phosphoric acid compounds, and even more preferably a compound represented by (Formula I) (acidic extractant), which will be described later. Extractants suitably used in the present invention will be described later.

[0051] The content of the extractant in the oil phase is set appropriately, taking into consideration the content of metal ions, the amount of coordination to metal ions, etc. For example, the content of the extractant in the oil phase is 20 to 1.0 × 10 ４ It can be expressed as millimoles / L (mM), and is 50 to 2.0 × 10 ３ It is preferable to use a ratio of millimoles / L, and 50 to 1.0 × 10 ３ It is preferable to use millimoles / L.

[0052] The temperature of the oil phase (during storage and at the start of flow) is not particularly limited and can be, for example, 10 to 60°C, or 15°C or more and less than 40°C. In the present invention, an aqueous solution containing a pH adjusting agent can be added to the oil phase in any amount, or in an amount that results in a predetermined mixed pH when the aqueous phase and oil phase are mixed. Density of the oil phase (kg / m³) ３ The temperature (25°C) is not particularly limited and cannot be uniquely determined by the type of organic solvent, the type or content of the extractant, etc., but for example, 5.0 × 10 ２ ~1.5 x 10 ３ kg / m ３ This is, for example, the kinetic energy E, which will be discussed later. ＳＴ It is preferable in that it is easy to set the kinetic energy E to a suitable value. ＳＴ Setting this value to a suitable value is preferable because it allows for an increase in the amount of metal ions extracted.

[0053] The oil phase is prepared by using the extractant (which is liquid in the operating environment) either in its original state or as a solution in an organic solvent. The oil phase as a solution of the extractant can be prepared by dissolving the extractant in an organic solvent. The preparation conditions for the oil phase are not particularly limited. For example, the preparation temperature can usually be 10 to 60°C, but it can be determined considering the solubility of metal ions, etc.

[0054] <Aqueous Solution Containing pH Adjuster> In the present invention, it is preferable to use an aqueous solution containing a pH adjuster. The water used to form the aqueous solution of the pH adjuster is not particularly limited, but (ultra)pure water, ion-exchanged water, etc., can be used. Examples of pH adjusters to be contained in the aqueous solution containing the pH adjuster include the acids and alkalis that can be used to adjust the pH of the aqueous phase. Among these, the inorganic acids and inorganic alkalis are preferred, and hydrochloric acid or an aqueous solution of hydrochloric acid, and alkali hydroxide (hydroxides of Group 1 elements) are more preferred. The content of the pH adjuster in the aqueous solution containing the pH adjuster is set appropriately and determined to achieve a predetermined pH. The temperature of the aqueous solution containing the pH adjuster (during storage and at the start of circulation) is not particularly limited, and can be, for example, 10 to 60°C, or 15°C or more and less than 40°C. The aqueous solution containing the pH adjuster can be prepared by dissolving the pH adjuster in water. The preparation conditions for the aqueous solution containing the pH adjuster are not particularly limited. For example, the preparation temperature can usually be 10 to 60°C, but can be determined considering the solubility of metal ions, etc.

[0055] [Extraction Method of the Present Invention] The extraction method of the present invention is a method of mixing an aqueous phase containing two or more metal ions and an oil phase containing an extractant during flow, and then separating the phases. The method separates the two phases in a mixed state in which at least one of the two or more metal ions to be extracted is in extraction equilibrium, and the remaining metal ions are in non-extraction equilibrium. In other words, in the present invention, the phase separation is performed in a mixed state (stage) in which at least one metal ion has reached extraction equilibrium, but the remaining metal ions have not yet reached extraction equilibrium. The present invention was completed based on the discovery that in batch extraction methods, if the mixing time of the two phases is short, phase separation is difficult, and if it is long, almost all metal ions reach extraction equilibrium during phase separation, whereas in flow extraction methods, phase separation proceeds rapidly, enabling the above-mentioned mixed state to be achieved and maintained while phase separation is performed. The extraction method of the present invention, which enables rapid phase separation in such a mixed state, can move (extract) specific metal ions coordinated with the extractant from the aqueous phase to the oil phase with high selectivity and in a short time.

[0056] In this invention, "residual metal ions" refers to metal ions whose extraction into the oil phase should be suppressed in relation to the metal ions to be extracted, and does not include metal ions that do not participate in the extraction into the oil phase. For example, metal ions derived from pH adjusters are not intended to be separated from the metal ions to be extracted, so even if they are present in the system, it is not necessary to consider whether they are in extraction equilibrium or non-extraction equilibrium. There may be one or more metal ions whose extraction into the oil phase should be suppressed.

[0057] In the extraction method of the present invention, the mixing of the aqueous phase and the oil phase is performed when the mixture of both phases has reached a pH suitable for the metal ions to be extracted. In the present invention, the "state at a suitable pH" is defined as the point at which the mixing of a predetermined amount of aqueous solution containing a pH adjusting agent into both phases is completed, or the point at which the mixing of the pH-adjusted aqueous phase or pH-adjusted oil phase, as described later, is completed, which serves as the starting point (start of mixing).

[0058] In this invention, extraction equilibrium refers to the usual meaning in wet extraction methods, but whether or not extraction equilibrium has been reached can be defined using the degree of equilibrium attainment obtained from prior experiments as an indicator. First, an aqueous phase, an oil phase, and an aqueous solution containing a pH adjusting agent to be used in the extraction method of this invention are prepared, and in a batch extraction method, the aqueous phase and the oil phase are mixed at various pH values, and the time dependence of the extraction rate of metal ions at each pH value is obtained, and the point in time when the extraction rate becomes unchanged with respect to the change in time (invariance start time) is defined as the equilibrium point. The mixing conditions in the batch method are basically the same as the conditions for performing the extraction method of this invention (except for conditions specific to flow extraction methods such as flow rate). Next, the extraction rate R at the equilibrium point of the metal ion is determined. Ｅ Determine the extraction rate R at any given mixing time. Ｒ The following formula is used to calculate the "equilibrium attainment" using these values. If the calculated equilibrium attainment value is 0.95 or higher at any given mixing time, the metal ion is considered to be in equilibrium (attained) in the extraction method of the present invention. If the calculated equilibrium attainment value is less than 0.95 at any given mixing time, the metal ion is considered to be in a non-equilibrium state (not reached) in the extraction method of the present invention. The "extraction rate" refers to the percentage calculated by the following formula from the content CI of the metal ion to be extracted contained in the aqueous phase and the content (residual amount) C1 of the metal ion remaining in the aqueous phase after the batch extraction method has been carried out. (Equilibrium attainment) = (Extraction rate R Ｒ ) / (R sampling rate at the equilibrium point) Ｅ ) (Extraction rate) = [(CI-C1) / CI] x 100 (%)

[0059] In the extraction method of the present invention, the means for achieving the above-described mixed state are not particularly limited and can be determined by prior studies, etc. The above-described mixed state can be appropriately achieved by, for example, the pH value at the time of mixing of both phases, the mixing ratio of the aqueous phase and the oil phase (the mixing ratio of metal ions and extractant), the type of metal ions to be extracted, the types of metal ions other than those to be extracted, and the confluence conditions and mixing conditions described later, as well as the temperature, the ratio of metal ions to be extracted to other metal ions, etc. Specifically, if the "liquid residence time," which indicates the time from the start of mixing until phase separation (until the end of phase separation) is made long, metal ions other than those to be extracted may also reach extraction equilibrium or near it, on the other hand, if the liquid residence time is made short, there is a possibility that the metal ions to be extracted will not reach extraction equilibrium. The liquid residence time can be set, for example, by comparing the time dependence of the degree to which each metal ion reaches the above equilibrium. Depending on the type and combination of metal ions, in the present invention, the above-described mixed state can be achieved if the liquid residence time is, for example, 15 minutes or less. The residence time is preferably 7 minutes or less, more preferably 5 minutes or less, even more preferably 4 minutes or less, and particularly preferably 3 minutes or less, as it allows for a high level of equilibrium attainment for the metal ions to be extracted while keeping the level of equilibrium attainment for metal ions other than the target of extraction low. The lower limit of the residence time can be determined by prior studies, for example, it can be 30 seconds or more, and preferably 1 minute or more.

[0060] The above liquid residence time is the sum of the mixing time and the time required for phase separation (phase separation time). In the present invention, the mixing time and the phase separation time can be determined by considering the time dependence of the equilibrium attainment. In the present invention, the mixing time is usually equal to or greater than the phase separation time, and preferably longer than the phase separation time. For example, the mixing time can be 1 or more times the phase separation time, preferably 1.2 to 20 times, and more preferably 1.5 to 10 times, in order to easily achieve the above mixed state. In the extraction method of the present invention, the three-liquid mixture undergoes phase separation in a relatively short time, so the above mixed state can be achieved if the liquid residence time is within the above range. The time required for the three-liquid mixture to undergo phase separation can be, for example, 10 minutes or less, preferably 3 minutes or less, more preferably 2 minutes or less, and even more preferably 90 seconds or less. The lower limit is not particularly limited, and can be, for example, 10 seconds or more, and preferably 30 seconds or more. In the present invention, "until phase separation occurs (completion of phase separation)" means until the two phases have separated to a degree that can be judged in a wet extraction method as "the aqueous phase and the oil phase have separated from each other," for example, until the phase separation operation can be started.

[0061] In the present invention, the above-described mixed state can also be achieved by setting the confluence conditions and mixing conditions to the conditions described later. Furthermore, means for achieving the above-described mixed state include, in addition to confluence conditions and mixing conditions such as liquid residence time, flow rate, and mixing section length, the metal ion concentration in the aqueous phase, the extractant concentration in the oil phase, and the ratio of the amount of metal ions to the amount of extractant in the mixing process of the aqueous phase and the oil phase. For example, the above-described mixed state can be achieved by setting the mixing section length (the distance over which both phases flow in a mixed state) to 2 m or less, although this depends on the flow rate (flow rate). The mixing section length is preferably 1.5 m or less, more preferably 1 m or less, and even more preferably 80 cm or less, in that it allows for a high value in the equilibrium attainment of the metal ions to be extracted while keeping the equilibrium attainment of metal ions other than the target of extraction low. The lower limit of the mixing section length can be determined by prior studies, and for example, it can be 10 cm or more, and preferably 20 cm or more. The above-mentioned confluence and mixing conditions, as well as the content and combination of metal ions present in the aqueous phase, and the type and content of the extractant, can serve as indicators for achieving the aforementioned mixed state if the following conditions are adopted, particularly if they are preferred.

[0062] In the extraction method of the present invention, the metal ions to be extracted are not particularly limited and can be determined as appropriate, for example, as described below.

[0063] As described above, the extraction method of the present invention can selectively move (extract) at least one specific metal ion from two or more metal ions from the aqueous phase to the oil phase, even in a short time (with high extraction resolution). In the extraction method of the present invention, the metal ions extracted into the oil phase are ideally one specific metal ion, but if those with low extraction rates are included, there may be two or more metal ions, or even all types. In other words, the extraction method of the present invention can separate and extract at least one metal ion from the other (residual) metal ions among the two or more metal ions contained in the aqueous phase. However, the metal ion extracted into the oil phase with high extraction resolution (also referred to in the present invention as "metal ion for extraction purpose or target of extraction") is at least one of the two or more metal ions (group) (not all types, but some types). For example, as ions of valuable metal elements, two or more heterogroup metal ions, specifically two or more metal ions belonging to groups 1 to 14 of the periodic table (preferably groups 2 to 14, more preferably groups 7 to 12, and even more preferably groups 8 to 11), preferably two or more heterogroup metal ions, and particularly preferably one metal ion from among cobalt ions and nickel ions, which are heterogroup metal ions of the same period, or one metal ion from among manganese ions, cobalt ions, and nickel ions, which are heterogroup metal ions of the same period, can be extracted into the oil phase with high extraction resolution.

[0064] The extraction method of the present invention was perfected by discovering the characteristic and function of being able to extract one of two or more metal ions (groups) present in the aqueous phase, including those with low extraction rates, into the oil phase with high extraction resolution (selectivity), preferably with a high extraction yield. In particular, it can be applied to new applications such as separating and recovering two or more metal ions, especially heterogroup metal ions. Heterogroup metal ions of the same period usually have similar physical and chemical behaviors, so it is not easy to separate and recover one of them with high extraction resolution (selectivity), preferably with a high extraction yield. However, in the extraction method of the present invention, heterogroup metal ions of the same period with similar physical and chemical behaviors, particularly metal ions belonging to Group 9 (especially cobalt ions) and metal ions belonging to Group 10 (especially nickel ions), which are required due to the rapid spread of lithium-ion batteries in recent years, can be extracted while recovering one of the metal ions with high extraction resolution (selectivity), preferably with a high extraction yield. Similarly, for metal ions belonging to Group 7 (especially manganese ions) and metal ions belonging to Group 10 (especially nickel ions), metal ions belonging to Group 9 (especially cobalt ions), or metal ions belonging to Group 2 (especially magnesium ions), and further, for metal ions belonging to Group 10 (especially nickel ions) and metal ions belonging to Group 11 (especially copper ions), regardless of the extraction rate, one of the metal ions can be recovered with high extraction resolution (selectivity) and preferably in a high extraction amount while extracting both. Therefore, the present invention can greatly contribute to the further spread of electric vehicles and, ultimately, to the construction of a sustainable society.

[0065] In the present invention, the ability to extract metal ions with high extraction resolution (high selectivity) is not unique, as it depends on the number and content of metal ions present in the aqueous phase and the content of the extractant in the oil phase, but it means that one specific metal ion can be selectively extracted from two or more metal ions present in the aqueous phase. Furthermore, when extracting two or more metal ions into the oil phase, including those with low extraction rates, the ability to extract metal ions with high selectivity is similarly not unique, but it means that among the two or more extracted metal ions, the amount extracted of the specific metal ion to be extracted (usually one) falls within the extraction amount range described later, and the amount of the remaining metal ions extracted is less than 30%. The amount of the remaining metal ions extracted is calculated in the same way as the amount extracted of the specific metal ion to be extracted, and under the conditions of the examples described later, it is preferably less than 20%, more preferably less than 15%, and even more preferably less than 10%. In the present invention, room temperature refers to the temperature in a room temperature environment, specifically a temperature range of 20 to 30°C.

[0066] In the present invention, the ability to extract metal ions in a high extraction amount is not unique, as it depends on the content of metal ions present in the aqueous phase, the content of the extractant in the oil phase, etc. However, for example, for the metal ions extracted into the oil phase in the extraction and separation cycle (for example, steps 1 to 3 described later) in the maximum extraction amount (a specific metal ion to be extracted), the amount of said metal ions extracted into the oil phase CA is a high value, calculated as the ratio of the difference between the content CI of said metal ions in the aqueous phase (before extraction) and the content (residual amount) C1 of said metal ions in the aqueous phase (after extraction) [(CI - C1) / CI] × 100 (%), and the amount of said metal ions extracted into the oil phase. In the present invention, the extraction amount (the above ratio) CA is preferably 80% or more, and under the conditions of the above examples described later, it is preferably 90% or more, and more preferably 95% or more. Ideally, the upper limit should be 100%, but in practice, it is preferable to have a value of, for example, 99.5% or less, and it can also be 99% or less.

[0067] In the extraction method of the present invention, the temperature when the two phases are mixed or during mixing (regardless of when they merge) (hereinafter referred to as the "mixing temperature") is not particularly limited and can be any temperature in the range of 15 to 95°C, and preferably any temperature in the range of 20 to 95°C. The mixing temperature can be appropriately determined considering the selectivity and amount of metal ions to be extracted (sometimes simply referred to as "selectivity and amount of extraction" in the present invention), and the amount of extraction tends to increase as the temperature rises. In addition, in the present invention, even if the mixing temperature and the merge temperature described later are increased, it is a flow-type extraction method, so the thermal history applied to the extractant can be minimized, thereby effectively suppressing the decomposition and deterioration of the extractant and achieving excellent repeated durability. In terms of further increasing the amount of extraction while maintaining high selectivity, the mixing temperature is preferably 40°C or higher, more preferably 50°C or higher, even more preferably above 60°C, and particularly preferably 80°C or higher within the above temperature range. The upper limit of the mixing temperature is not particularly limited, but it is preferably 95°C or lower in that it can suppress deterioration of the mixing state of the aqueous phase and the oil phase, and more preferably 93°C or lower, and especially preferably 91°C or lower, in that it provides an excellent balance between selectivity and extraction amount.

[0068] In the extraction method of the present invention, the mixing temperature is preferably higher than the temperature of at least one of the aqueous phase and the oil phase at the start of flow, and more preferably higher than the temperature of both the aqueous phase and the oil phase at the start of flow, in order to further increase the extraction amount while maintaining the selectivity of the metal ions to be extracted. Specifically, the extraction method of the present invention set to a preferred mixing temperature is a method in which an aqueous phase containing two or more metal ions and an oil phase containing an extractant are brought together during flow, the two phases are mixed at a temperature higher than the temperatures of the aqueous phase and the oil phase at the start of flow, and the phases are separated in a mixed state in which at least one of the two or more metal ions to be extracted is in extraction equilibrium and the remaining metal ions are in non-extraction equilibrium. That is, at least the temperature when the two phases are mixed or during mixing (regardless of when they are brought together) is adjusted to the above temperature relationship. A preferred extraction method of the present invention, which adjusts the temperature at least at the time of mixing (after adjusting the three-liquid mixture to a predetermined pH) to be higher than the temperature of at least one of the aqueous and oil phases at the start of flow, allows for the transfer (extraction) of specific metal ions coordinated by the extractant from the aqueous phase to the oil phase with high selectivity and high extraction yield, and in a short time. The mixing temperature should be higher than the temperature of at least one of the aqueous and oil phases at the start of flow, and preferably higher than the temperatures of both the aqueous and oil phases at the start of flow. In the present invention, the mixing temperature refers to the final temperature reached during the mixing process.

[0069] The temperature difference between the temperatures of both phases at the start of flow and the mixing temperature is not particularly limited, but it is preferably 0 to 90°C, more preferably 10 to 80°C, and even more preferably 20 to 70°C, in order to further increase the extraction amount while maintaining high selectivity.

[0070] When mixing the combined aqueous and oil phases with the pH adjusting agent-containing aqueous solution, the temperature of the pH adjusting agent-containing aqueous solution is not particularly limited and may be low, the same temperature as the mixing temperature, or high.

[0071] In the extraction method of the present invention, the temperature at the time of or during the joining of the two phases (hereinafter referred to as the "joining temperature") is not particularly limited and can be any temperature in the range of 15 to 95°C, preferably any temperature in the range of 20 to 95°C, and more preferably any temperature in the range of 40 to 95°C. The joining temperature may be the same temperature as or lower than the temperatures of the aqueous and oil phases at the start of flow, but it is preferable that it be higher than the temperature of at least one (more preferably both) of the aqueous and oil phases at the start of flow in order to further increase the extraction amount while maintaining high selectivity of the metal ions to be extracted. In the present invention, the joining temperature means the final temperature reached during the flow process. The joining temperature, which is set to a temperature higher than the temperatures of the aqueous and oil phases at the start of flow, is not particularly limited and is preferably within the same range as the mixing temperature. In the present invention, the joining temperature may be the same temperature as or different from the mixing temperature, and depending on the flow velocity and flow rate of both phases, the mixing temperature may be higher than the joining temperature. Furthermore, in the present invention, the temperature difference between the temperatures of both phases at the start of flow and the confluence temperature is not particularly limited, and it is preferable to set it within the same range as the temperature difference between the temperatures of both phases at the start of flow and the mixing temperature as described above. Note that the temperature difference between the temperatures of both phases at the start of flow and the mixing temperature, and the temperature difference between the temperatures of both phases at the start of flow and the confluence temperature, may be the same or different.

[0072] In this invention, the temperatures of the aqueous phase and the oil phase at the start of flow may be the same or different.

[0073] In the extraction method of the present invention, it is preferable to merge the aqueous phase and the oil phase by utilizing the collision of each phase (both phases) as they are flowing, in that this can further increase the extraction amount while maintaining selectivity. In the present invention, "merging by utilizing the collision of each phase" means merging the flowing aqueous phase and the flowing oil phase by bringing them into contact with each other. For example, the two phases can be brought into contact and merged while maintaining an angle between the flow direction of the aqueous phase and the flow direction of the oil phase. Here, the angle between the flow directions is not particularly limited and can be greater than 0° and less than or equal to 180°, and can be set to an angle (excluding 0°) as described in the section on merging angles later, in that it can improve the mixing state. Various conditions in the extraction method of the present invention will be described later in the section on the extraction method of the present invention.

[0074] [Preferred Extraction Method of the Present Invention] The present invention provides a method for extracting metal ions, which involves combining an aqueous phase containing two or more metal ions and an oil phase containing an extractant during flow, mixing the two phases, and then separating the phases to extract at least one metal ion into the oil phase. The method is characterized in that, of the two or more metal ions, at least one metal ion to be extracted is in extraction equilibrium, and the remaining metal ions are in non-extraction equilibrium, and the two phases are separated in a mixed state. The present invention provides an extraction method that is not particularly limited as long as it can mix and separate phases as described above, and is preferably a flow-type wet extraction method having at least the following steps 1 to 3 (sometimes referred to as "the preferred extraction method of the present invention"). In the preferred extraction method of the present invention, an aqueous phase containing metal ions, an oil phase containing an extractant, and an aqueous solution containing a pH adjuster are used as appropriate. Step 1: A process of combining the flowing aqueous phase and oil phase and continuing to flow. Step 2: A process of mixing the aqueous phase and oil phase with an aqueous solution containing a pH adjuster and continuing to flow. Step 3: A process of separating the phases of the three-liquid mixture in a mixed state where at least one of the two or more metal ions to be extracted is in extraction equilibrium and the remaining metal ions are in non-extraction equilibrium.

[0075] The preferred extraction method of the present invention can be suitably carried out using the extraction apparatus suitable for the present invention described above. The preferred extraction method of the present invention will be specifically described below with reference to the extraction apparatus 1 shown in Figure 1 and the extraction apparatus 2 shown in Figure 2.

[0076] <Step 1> In the extraction method of the present invention, the following Step 1 is performed using the prepared aqueous phase and oil phase. Step 1: A step in which the flowing aqueous phase and oil phase are combined and continued to flow.

[0077] In step 1, when using the extraction device 1, the aqueous phase or oil phase is transferred and circulated in the aqueous phase circulation pipe 11 and the oil phase circulation pipe 12 from the aqueous phase storage tank 5 and the oil phase storage tank 6 using a transfer mechanism, such as various pumps. In step 1, the aqueous phase and the oil phase are merged during the flow.

[0078] In Step 1 of the Preferred Extraction Method of the Present Invention and in the Preferred Extraction Method of the Present Invention (hereinafter referred to as "Step 1, etc."), the confluence conditions are not particularly limited and can be determined as appropriate. The mixing ratio of the aqueous phase and the oil phase is not particularly limited and may be mixed in an appropriate ratio, but it is preferable that the ratio to the content (moles) [content of extractant (moles) / total content of metal ions contained in the aqueous phase (moles)] and / or the ratio of the content of the extractant to the total content of metal ions to which the extractant can coordinate [moles of extractant / total number of moles of metal ions to which the extractant can coordinate] is satisfied, as described later. Setting the following conditions as confluence conditions, for example, conditions for transferring the aqueous phase and the oil phase, and conditions for confluence or mixing the two phases, is preferable in terms of selectivity and extraction amount. It is preferable that at least one of the aqueous phase and the oil phase satisfies the following preferred ranges, etc., for each of the following conditions, and it is more preferable that both satisfy the following preferred ranges, etc., in terms of metal ion selectivity and extraction amount. For each condition, if both the aqueous phase and the oil phase meet the following preferred ranges, the conditions for the aqueous phase and the conditions for the oil phase may be the same or different.

[0079] In step 1, etc., the temperature at the time of confluence of the aqueous phase and the oil phase (before pH adjustment) is not particularly limited and is as described above. The confluence temperature can be lower than the temperatures of the aqueous phase and the oil phase at the start of flow, but is usually the same, preferably the mixing temperature described later. Setting the temperature at confluence to the same range as the mixing temperature described later can further improve the extraction amount. When using a pH-adjusted aqueous phase or oil phase, the temperature at confluence is set to the same range as the mixing temperature described later.

[0080] In process 1, etc., the flow velocity of the water phase cannot be uniquely determined depending on the internal pressure, the inner diameter of the water phase flow pipe 11, the ratio of the above inner diameters (inner diameter of the open end of the tip section / inner diameter of the connection section with a constant inner diameter tip section in the flow pipe), etc., but for example, 1.0 × 10 －３ ~1.0 x 10 ３ It can be set to L / min, and the mixing state can be improved, hence 3.0 × 10 －３ ~5.0 x 10 ２ The flow rate is preferably L / min, more preferably 6.0 to 30 mL / min, even more preferably 4.0 to 28.0 mL / min, particularly preferably 5.0 to 25.0 mL / min, and most preferably 10 to 25 mL / min, in order to achieve a high level of both selectivity and extraction volume. Similarly, the internal pressure (flow pressure) of the aqueous phase cannot be uniquely determined, but for example it can be 0.01 to 5.0 MPa, and it is preferable to set it to 0.03 to 2.5 MPa in order to improve the mixing state. The flow rate of the oil phase cannot be uniquely determined depending on the internal pressure, the inner diameter of the oil phase flow pipe 12, the ratio of the above inner diameters, etc., but for example 1.0 × 10 －３ ~1.0 x 10 ３ It can be set to mL / min, and the mixing state can be improved, hence 3.0 × 10 －３ ~5.0 x 10 ２It is preferable to have a flow rate of mL / min, more preferably 6.0 to 30 mL / min, even more preferably 4.0 to 28.0 mL / min, particularly preferably 5.0 to 25.0 mL / min, and most preferably 10 to 25 mL / min, in order to achieve a high level of both selectivity and extraction volume. Similarly, the internal pressure (flow pressure) of the oil phase cannot be uniquely determined, but for example it can be 0.01 to 5.0 MPa, and it is preferable to have a flow rate of 0.03 to 2.5 MPa in order to improve the mixing state.

[0081] The flow rates of the aqueous phase and the oil phase per unit time can be appropriately determined by the inner diameter of each flow pipe, the ratio of the metal ion content to the extractant content, and the flow rates per unit time can be set to different amounts or to the same amount. In step 1, regardless of the flow rate per unit time, the ratio (moles) of the metal ion content to the extractant content when the aqueous phase and the oil phase are mixed [extractant content (moles) / total metal ion content (moles) in the aqueous phase] is preferably 0.5 to 50.0 times, more preferably 1.0 to 20.0 times, and even more preferably 1.0 to 10.0 times. Furthermore, the ratio of the extractant content to the total amount of metal ions to which the extractant can coordinate (also called the mixing amount) [moles of extractant / total moles of metal ions to which the extractant can coordinate] can be, for example, 1.0 to 25.0 times, preferably 1.0 to 15.0 times, more preferably 1.0 to 10.0 times, and even more preferably 1.0 to 7.0 times. Here, the metal ions to which the extractant can coordinate refer to the metal ions to which the extractant coordinates and is extracted into the oil phase.

[0082] As described above, the water phase flowing through the water phase flow pipe 11 and the oil phase flowing through the oil phase flow pipe 12 are led to the confluence section 13 and merged with each other. At this time, the flow diameters of both phases may be constant, decreasing, or increasing, but it is preferable that they are constant or decreasing. Here, a constant flow diameter is synonymous with a constant inner diameter of each flow pipe. When the flow diameters of both phases are decreased and the two phases are merged, the reduction ratio of the flow diameter (the ratio of the inner diameters mentioned above) is not uniquely determined by the flow velocity, internal pressure, etc., but for example, it is preferable that it is 0.9 or less with respect to the inner diameter and flow velocity of each flow pipe. The reduction ratio of the flow diameters of both phases is more preferably 0.8 or less, even more preferably 0.6 or less, and particularly preferably 0.55 or less, in terms of improving the mixing state, specifically, in terms of maintaining rapid phase separation (also called phase separation or liquid separation) of the two phases after mixing while achieving a high level of selectivity and extraction amount. The lower limit of the reduction ratio is not particularly limited, and can be 0.05 or more in terms of suppressing excessive internal pressure load and providing excellent workability, and is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more in terms of improving the mixing state as described above. The distance between the end opening of the aqueous phase flow pipe 11 and the end opening of the oil phase flow pipe 12 (length of the confluence section 13 (impact region)) is appropriately determined considering the mixing state (impact force) of the aqueous and oil phases, and can be, for example, 1 to 100 mm.

[0083] In the present invention, the flow conditions and confluence conditions of the aqueous phase and the oil phase can be appropriately selected from the above conditions, but the conditions for each phase converging, particularly for each phase converging due to collision between the two phases, are the kinetic energy per unit area and per unit time (in the present invention, this may simply be referred to as "kinetic energy") E ＳＴ Setting this is preferable because it allows for a good balance between selectivity and extraction yield at a high level. In the present invention, the kinetic energy E per unit area and per unit time ＳＴ (J / sec / m ２ ) is calculated from the density of the fluid (aqueous phase and oil phase), the linear velocity and volumetric flow rate at the confluence 13 (end opening of each flow pipe), and the cross-sectional area using the following formula (EＳＴ It can be calculated using the formula (E ＳＴ ) E ＳＴ = (1 / 2) × ρ × u ２ ×Q×(1 / A) Equation (E ＳＴ In this case, ρ is the density of the fluid being circulated (kg / m³). ３ ) where u is the linear velocity (m / sec) of the fluids being circulated at the time of confluence (when flowing into the confluence section 13), and Q is the volumetric flow rate (m) of the fluids being circulated at the time of confluence (when flowing into the confluence section 13). ３ / sec) where A is the cross-sectional area (m²) calculated from the inner diameter at the end opening (junction 13) of each flow pipe. ２ )

[0084] Here, the density of the fluid is ρ (kg / m³). ３ ) is calculated by measuring the mass W (g) of the fluid used when making up the fluid to be measured in a 100 mL volumetric flask, and then (W / 100) × 1000 (kg / m ３ The linear velocity u (m / sec) of the fluid is calculated by multiplying the fluid flow rate (mL / min) by 60 × 10⁻¹⁰. －６ × 1 / A(m) -２ It can be calculated by multiplying by ). In the present invention, the above linear velocities of the aqueous phase and the oil phase are not particularly limited, for example, 1.0 × 10 －４ ~1.0 x 10 －１ It is preferable to set it to m / sec, 5.0 × 10 －４ ~5.0 x 10 －２ It is more preferable to use m / sec. Fluid volume flow rate Q (m ３ The value ( / sec) can be converted from the above flow rate (mL / min).

[0085] In the present invention, the above kinetic energy E ＳＴ Increasing the kinetic energy E enhances the mixing state due to collisions between the aqueous and oil phases, further improving selectivity and extraction yield. ＳＴ This can be appropriately set considering the flow conditions and confluence conditions of the aqueous and oil phases as described above. For example, the kinetic energy E ＳＴ In that it can increase the interface area between the aqueous and oil phases, thereby further improving selectivity and extraction yield, it is effective at 50 J / sec / m ２It is preferable to be as above, 2.0×10 ２ J / sec / m ２ It is more preferable to be as above, 5.0×10 ２ J / sec / m ２ It is even more preferable to be as above. On the other hand, as the above-mentioned kinetic energy E ＳＴ in terms of being able to enhance the phase separation property, it is preferable to be 1.0×10 ５ J / sec / m ２ or less, and in terms of being able to further increase the selectivity and extraction amount while maintaining a high phase separation property, it is more preferable to be 1.6×10 ４ J / sec / m ２ or less, it is even more preferable to be 1.0×10 ４ J / sec / m ２ or less, it is particularly preferable to be 5.0×10 ３ J / sec / m ２ or less. One of the preferable embodiments of the kinetic energy E ＳＴ is that regardless of the above upper and lower limit values, it is preferably 5.0 to 5.0×10 ２ J / sec / m ２ and more preferably 10 to 3.5×10 ２ J / sec / m ２ and even more preferably 20 to 2.8×10 ２ J / sec / m ２

[0086] In the present invention, the conditions for carrying out Step 1 etc. can be appropriately selected from the above-mentioned respective conditions, and can be set by appropriately combining each condition. In the present invention, the conditions for carrying out Step 1 etc. are, in terms of being able to further improve the selectivity and extraction amount, among the above-mentioned respective conditions, it is preferable to set at least one of the flow rate, the reduction ratio of the flow diameter (ratio of the inner diameters), and the kinetic energy E ＳＴ and more preferably to set the flow rate and the reduction ratio of the flow diameter in combination within any of the above ranges in terms of being able to achieve both the selectivity and the extraction amount at a high level, and even more preferably to set the flow rate, the reduction ratio of the flow diameter, and the kinetic energy E ＳＴ ​It is even more preferable to combine the above and set them within any of the above ranges. For example, the flow rate is set within the range of 6.0 to 30 mL / min, the flow diameter reduction ratio is set within the range of 0.05 to 0.9, and the kinetic energy E ＳＴ 50 to 1.0 x 10 ５ J / sec / m ２ It is preferable to set each of these conditions within the range or within the range defined in one of the preferred embodiments. In this embodiment, each of the combined conditions can also be within the preferred range described above. In this embodiment, conditions other than these can be combined, for example, it is also preferable to combine the above ratio (moles) [extractant content (moles) / total content of metal ions contained in the aqueous phase (moles)] and / or content [moles of extractant / total number of moles of metal ions that the extractant can coordinate].

[0087] In this invention, the flow diameter, as well as the inner diameter of the flow pipe and the opening diameter of the tip section, are defined as "equivalent diameters." "Equivalent diameter" is also called the equivalent (straight) diameter and is a term used in the field of mechanical engineering. When an equivalent circular pipe is assumed for a pipe or flow path with an arbitrary internal cross-sectional shape, the diameter of the internal cross-section of that equivalent circular pipe is called the equivalent diameter. The equivalent diameter (deq) is defined as deq = 4A / p, where A is the internal cross-sectional area of ​​the pipe and p is the wet-edge length (internal circumference) of the pipe. When applied to a circular pipe, this equivalent diameter coincides with the diameter of the internal cross-section of the circular pipe. The equivalent diameter is used to estimate the flow or heat transfer characteristics of the pipe based on the data of the equivalent circular pipe, and represents the spatial scale (representative length) of the phenomenon. For a square pipe with an internal cross-section of side a, the equivalent diameter is deq = 4a ２ / 4a = a, in an equilateral triangular tube with side length a, deq = a / 3 １／２ For flow between parallel plates with a flow path height h, deq = 2h (see, for example, "Dictionary of Mechanical Engineering" edited by the Japan Society of Mechanical Engineers, 1997, Maruzen Co., Ltd.).

[0088] In step 1, the confluence angle of the aqueous phase and the oil phase is not particularly limited. In the extraction device 1, the confluence angle is 180° (opposing), but in the present invention, the confluence angle can be 0 to 180°, and it is preferable to set it to 30 to 180°, more preferably to 90 to 180°, and even more preferably to 150 to 180°, as the mixing state can be improved by using the collision of the aqueous phase and the oil phase to confluence them. In step 1, as described above, the flowing aqueous phase and the flowing oil phase are made to collide in the confluence section 13 to confluence and mix the two phases, and then transferred to the mixing section 14, where they continue to flow through the internal passage of the mixing section 14.

[0089] <Step 2> In the extraction method of the present invention, the following Step 2 is performed. Step 2 may be performed after Step 1, or together with Step 1. Step 2 is a pH adjustment step, which starts mixing of the aqueous phase and the oil phase, and in Step 2, a mixed state is achieved in which at least one of the two or more metal ions to be extracted is in extraction equilibrium, and the remaining metal ions are in non-extraction equilibrium. Step 2: A step of combining the aqueous phase, the oil phase and the aqueous solution containing the pH adjuster and further passing it through.

[0090] (Step 2A) Step 2A is a step in which pH adjustment is performed following Step 1. For example, when using the extraction device 1, the pH adjusting agent-containing aqueous solution is circulated from the pH adjusting agent-containing aqueous solution storage tank 7 into the pH adjusting agent transfer pipe 15 using a transfer mechanism, such as various pumps, and then transferred to the mixing section 14. At this time, the amount of pH adjusting agent-containing aqueous solution circulated is set to an amount such that the pH of the three-liquid confluence mixed in the mixing section 14 reaches a predetermined value. The set pH is not unique, but is appropriately determined considering the pKa of the extractant, the complex formation constant of the extractant and metal ions, the coordination number of the metal ions, etc. The pH of the three-liquid confluence (the aqueous phase in it) can be 0.01 to 14. For example, in terms of selectivity and extraction amount, it is preferably 0.1 to 10, more preferably 0.5 to 7.0, even more preferably 1.0 to 6.5, particularly preferably 2.5 to 6.5, and most preferably 3.0 to 6.5. A specific example of pH for metal ions is the range of ±0.2 of the pH value set for each metal ion in the examples described later. Furthermore, the flow rate of the aqueous solution containing the pH adjusting agent cannot be uniquely determined, depending on the internal pressure of the pH adjusting agent transfer pipe, the inner diameter of the pH adjusting agent transfer pipe 15, the internal pressure of the mixed liquid flowing in the mixing section 14, etc., but it can be, for example, 0.05 to 10.0 mL / min. Similarly, the internal pressure (flow pressure) of the aqueous solution containing the pH adjusting agent cannot be uniquely determined, and is set to a pressure that allows it to be transferred into the mixing section 14.

[0091] As described above, in step 2, the two-liquid mixture of the aqueous phase and oil phase that were combined in step 1 (also called the oil-water mixture) is combined with the pH adjusting agent-containing aqueous solution and further mixed. Specifically, in the extraction method of the present invention, when the extraction apparatus 1 is used, the pH adjusting agent-containing aqueous solution flowing through the pH adjusting agent transfer pipe 15 is transferred to the mixing section 14, where the oil phase and aqueous phase (two-liquid mixture) flowing through the downstream mixing section 14b are combined with the pH adjusting agent-containing aqueous solution and mixed. This results in a three-liquid mixture of both phases and the pH adjusting agent-containing aqueous solution (also called the adjusting agent mixture), and its pH can be adjusted to the predetermined value. After that, the three-liquid mixture is further mixed through the downstream mixing section 14b and transferred to the separation section 16. In step 2A, at least one of the mixing conditions described in the means for achieving the above-described mixed state is applied. By performing step 2A, which applies these mixing conditions, following step 1, the three-liquid mixture flows through the mixing section and reaches a mixed state in which at least one of the two or more metal ions contained in the aqueous phase is in extraction equilibrium, and the remaining metal ions are in non-extraction equilibrium. This mixed state is maintained as the mixture is transferred to the separation section 16.

[0092] Furthermore, in the present invention, when using the extraction apparatus 1, it is preferable to mix the aqueous phase, oil phase, and pH adjusting agent-containing aqueous solution (three-phase combined liquid) at a temperature higher than the temperature of at least one of the aqueous phase and oil phase at the start of flow. The temperature conditions at this time are as described in the extraction method of the present invention. When using the extraction apparatus 1 and the extraction apparatus 2, as described above, heating devices provided in the aqueous phase flow pipe 11 (especially the downstream portion such as the tip section 11a), the oil phase flow pipe 12 (especially the downstream portion such as the tip section 12a), the confluence section 13, the mixing section 14, the pH adjusting agent transfer pipe 15 (especially the downstream portion such as the tip section), etc., can heat both phases flowing through the pipes, as well as the pH adjusting agent-containing aqueous solution, and the combined phases (three-phase combined liquid) can be heated to a predetermined temperature. Furthermore, the temperature of the combined liquid of the two phases from the time of the confluence of the aqueous and oil phases until immediately before mixing with the pH adjusting agent-containing aqueous solution (confluence temperature) may be lower than or the same as the temperature of at least one of the aqueous and oil phases at the start of flow, but it is preferable that the temperature be higher than the temperature of the aqueous and oil phases at the start of flow, as this improves the mixing state and further increases the extraction amount.

[0093] (Step 2B) Step 2B is a step in which pH adjustment is performed in Step 1. For example, when using the extraction device 2, in Step 1, the pH adjusting agent-containing aqueous solution is directly introduced to the confluence 23 from the pH adjusting agent transfer pipe 15 connected to the confluence 23, and the three liquids flowing into the confluence 23, namely the aqueous phase, the oil phase, and the pH adjusting agent-containing aqueous solution, are combined. The flow conditions at this time can be set to be the same as the flow conditions in the method using the extraction device 1. In this way, the aqueous phase, the oil phase, and the pH adjusting agent aqueous solution are combined all at once. Specifically, the aqueous phase flowing through the aqueous phase flow pipe 11, the oil phase flowing through the oil phase flow pipe 12, and the pH adjusting agent-containing aqueous solution flowing through the pH adjusting agent transfer pipe 15 are transferred to the confluence 23, and the three liquids are combined (by collision) in the confluence 23 to obtain a three-liquid combined liquid with the pH adjusted to the predetermined value. Subsequently, the three-liquid combined liquid is further circulated through the mixing section 24, and the aqueous phase and oil phase are mixed while being transported to the separation section 16. In this step 2B, the pH of the three-liquid combined liquid is adjusted to a predetermined value in the confluence section 23, and mixing of the aqueous phase and oil phase begins (the confluence section 23 corresponds to a part of the mixing section 24).

[0094] In step 2B, at least one of the mixing conditions described above as means for achieving the mixed state is applied. By performing step 2B with such mixing conditions in step 1, the three-liquid mixture flows through the mixing section and reaches a mixed state in which at least one of the two or more metal ions contained in the aqueous phase is in extraction equilibrium, and the remaining metal ions are in non-extraction equilibrium. This mixed state is maintained as the mixture is transferred to the separation section 16.

[0095] In step 2B, it is preferable that the aqueous phase, oil phase, and pH adjusting agent-containing aqueous solution (three-liquid confluence) are combined and mixed at a temperature higher than the temperature of at least one of the aqueous phase and oil phase at the start of flow. The temperature conditions, location and type of heating device, etc., at this time are as described in the extraction method of the present invention. When combined and mixed at such a temperature, the mixing state is improved from the time the aqueous phase, oil phase, and pH adjusting agent-containing aqueous solution are combined, further increasing selectivity and extraction amount, and shortening the length of the mixing section 24 (mixing time).

[0096] In the present invention, in steps 2A and 2B, at least one of the aqueous phase and the oil phase may be a phase to which an aqueous solution containing a pH adjusting agent has been added in any amount.

[0097] (Step 2C) Step 2C is a step in which pH adjustment is performed in Step 1, and is performed using a pH-adjusted aqueous phase and / or pH-adjusted oil phase, in which an aqueous solution containing a pH adjusting agent has been added to the aqueous phase and / or oil phase in an amount that results in a predetermined mixed pH when the aqueous phase and oil phase are mixed. The pH adjusting agent added to the aqueous phase and / or oil phase in advance has been described above as an aqueous solution, but it may also be the pH adjusting agent itself. In Step 2C, for example, extraction devices 1 and 2 that do not have a pH adjusting agent transfer pipe 15 can be used. In Step 2C, for example, in Step 2 using extraction device 1 or 2, the aqueous phase and oil phase (at least one of which is pH-adjusted) are directly led from each transfer pipe 11 and 12 to the confluence section 13 or 23, and the two liquids flowing into the confluence section 13 or 23 are combined. The flow conditions, etc. at this time can be set to the same conditions as the flow conditions, etc. in the method using extraction device 1. In this way, the aqueous phase and the oil phase (at least one of which has been pH-adjusted) are combined all at once. Specifically, the aqueous phase flowing through the aqueous phase flow pipe 11 and the oil phase flowing through the oil phase flow pipe 12 are transferred to the confluence section 13 or 23, where the two liquids are mixed (by collision) in the mixing section 13 or 23. This mixing results in a pH-adjusted two-liquid confluence liquid (corresponding to the three-liquid confluence liquid described above) with a pH adjusted to a predetermined value. Subsequently, the pH-adjusted two-liquid confluence liquid is transferred to the separation section 16 by flowing it through the mixing section 14 or 24, while mixing the aqueous phase and the oil phase. In this step 2C, the pH of the three-liquid confluence liquid is adjusted to a predetermined value in the confluence section 23, and mixing of the aqueous phase and the oil phase begins (the confluence section 23 corresponds to a part of the mixing section 24).

[0098] In step 2C, at least one of the mixing conditions described above for achieving the mixed state is applied. By performing step 2C in step 1 with such mixing conditions applied, the two-liquid mixture flows through the mixing section and reaches a mixed state in which at least one of the two or more metal ions contained in the aqueous phase is in extraction equilibrium, and the remaining metal ions are in non-extraction equilibrium. This mixed state is maintained as the mixture is transferred to the separation section 16.

[0099] In step 2C, it is preferable that the aqueous phase and the oil phase (pH-adjusted two-liquid confluence) are combined and mixed at a temperature higher than the temperature of at least one of the aqueous phase and the oil phase at the start of flow. The temperature conditions, the location and type of the heating device, etc., at this time are as described in the extraction method of the present invention. When combined and mixed at such a temperature, the mixing state is improved from the time the aqueous phase and the oil phase (at least one of which is pH-adjusted) are combined, further increasing the selectivity and extraction amount, and shortening the length (mixing time) of the mixing section 14 or 24.

[0100] In the present invention, the three-liquid combined liquid is separated into an aqueous phase and an oil phase in step 3, which will be described later. However, the point at which the mixture is reached can be before the phase separation, or after it has been transferred to the separation section 16 of the extraction devices 1 and 2. However, it is generally preferable that the mixture is reached during the flow in step 1 or step 2 (until it is introduced into the standing section 16). Specifically, it is preferable that the mixture is reached while the three-liquid combined liquid is flowing through the downstream mixing section 14b or mixing section 24 of the mixing section 14.

[0101] In the present invention, it can be confirmed and identified by various methods that the extraction of the target metal ions has reached extraction equilibrium, while the extraction of other metal ions has not. For example, this can be confirmed and identified by measuring the amount of metal ions present in the aqueous phase sampled from the three-liquid confluence. In the present invention, in order to achieve the above-mentioned mixed state while the three-liquid confluence flows through the downstream mixing section 14b or mixing section 24, the flow time (flow path length), flow rate, inner diameter, etc. of the downstream mixing section 14b or mixing section 24 should be determined by referring to the value of the degree of equilibrium attainment in the batch extraction method described in the extraction method of the present invention. The time required to reach extraction equilibrium for the target metal ions cannot be uniquely determined depending on the amount of metal ions present in the aqueous phase, the type of extractant, the temperature, etc., but in the present invention, it can be a short time, and a time within the range of the above-mentioned liquid residence time can be cited.

[0102] In at least one of steps 1 and 2, it is preferable to circulate the combined liquid (combined liquid) through a channel containing a static mixer, as this greatly improves the mixing state of the combined liquid. When using extraction device 1, a static mixer can be installed in at least one of the channels of the pre-mixing section 14a and the post-mixing section 14b in the mixing section 14, and it is more preferable to install the static mixer in the channel of the post-mixing section 14b, as this further improves the mixing state of the three-liquid combined liquid. When using extraction device 2, a static mixer is installed in the channel of the mixing section 24.

[0103] <Step 3> In the extraction method of the present invention, the following Step 3 is then performed. Step 3: A step of separating the phases of the three-liquid mixture in a mixed state in which at least one of the two or more metal ions to be extracted is in extraction equilibrium and the remaining metal ions are in non-extraction equilibrium.

[0104] The separation method in step 3 is not particularly limited, and known separation methods such as the standing method and centrifugal separation method can be applied. The standing method is preferred because it has a simple apparatus configuration and excellent workability. The phase separation conditions are not particularly limited and can be set as appropriate, as long as they are conditions under which the three-liquid mixture separates into an aqueous phase and an oil phase. The standing time in the standing method is usually 30 seconds or more after being transferred to the separation unit 16, and can also be 1 to 30 minutes. In the extraction method of the present invention, since phase separation after mixing proceeds quickly, the standing time can also be set to a short time, for example, 1 to 10 minutes, and it is preferable to use the above-mentioned phase separation time. The temperature of the three-liquid mixture when separating the phases is not particularly limited, but from the viewpoint of phase separation properties, it is preferable that it be higher than the temperature of at least one of the aqueous phase and the oil phase at the start of flow, and it is preferable that it be approximately the same temperature as the temperature of the three-liquid mixture (mixing temperature) (mixing temperature ± 5°C).

[0105] In the extraction method of the present invention, the temperature at which each of steps 1 to 3 is carried out (excluding the confluence temperature and mixing temperature) is not particularly limited and may be at room temperature, a temperature higher than room temperature, or a temperature lower than room temperature.

[0106] In the extraction method of the present invention, by performing steps 1 to 3 described above, at least one metal ion to which the extractant is coordinately bonded can be extracted into the oil phase from among two or more metal ions present in the aqueous phase. Ideally, the number of types of metal ions extracted into the oil phase is one, but it may be two or more, including those with low extraction rates. In this case, for example, it can be 2 to 10 types, preferably 2 to 6 types, and more preferably 2 or 3 types. The two or more metal ions extracted into the oil phase from among the two or more metal ions are not particularly limited, but for example, it is preferable that they be the same as the two or more heterogroup metal ions (combinations) contained in the aqueous phase as described above.

[0107] In the extraction method of the present invention, steps 2B and 2C, in which a pH adjustment step is performed when the two phases are combined in step 1, are preferred in that they can improve the mixing state of the two phases, and step 2C, in which a pH-adjusted aqueous phase and / or a pH-adjusted oil phase is used, is more preferred in that it can further improve the mixing state of the two phases.

[0108] <Multi-cycle extraction method> The extraction method of the present invention can also perform a series of extraction and separation cycles of steps 1 to 3 described above a large number of times. The extraction method of the present invention, which performs a series of extraction and separation cycles a large number of times (sometimes referred to as the multi-cycle extraction method of the present invention), can perform the extraction and separation cycles including steps 1 to 3 as long as high selectivity, preferably high extraction yield, can be maintained, for example, 2 to 100 cycles, preferably 5 to 50 cycles. In the multi-cycle extraction method of the present invention, the oil phase separated in step 3 can be reused as the oil phase for the next extraction and separation cycle, thereby reducing extraction costs. At this time, if necessary, metal ions can be back-extracted from the phase-separated oil phase, and the content of the extractant can be adjusted. The oil phase obtained in step 3 (used oil phase) is usually used after back-extracting metal ions, but it can also be used without back-extraction, taking into consideration the content of metal ions in the aqueous phase, the amount extracted, etc. As a method for back-extracting (isolating) metal ions from the oil phase, known methods can be applied without particular limitation. For example, this can be done by making the liquid phase acidic, for example, pH 4 or lower, using an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid. This back-extraction method may be batch-type, but a flow-type method is preferable in that it does not impair the advantages of the extraction method of the present invention. There are no particular limitations on the back-extraction apparatus used in the flow-type back-extraction method, but an extraction apparatus suitable for the present invention can be used from the viewpoint of workability, cost reduction, etc. There are no particular limitations on the multi-cycle extraction apparatus suitably used in the multi-cycle extraction method of the present invention, and examples include the above-mentioned extraction apparatuses 1 and 2, and further extraction apparatuses 1 and 2 with the pH adjusting agent transfer pipe 15 removed. Furthermore, while there are no particular limitations on the multi-cycle extraction apparatus that is suitably used in the multi-cycle extraction method of the present invention that reuses the oil phase, examples include apparatuses in which, in the extraction apparatuses 1 and 2 described above, the oil phase discharge pipe 16a connected to the separation section 16 is connected to the oil phase storage tank 6, or to the middle of the confluence section with the oil phase storage tank 6 in the oil phase flow pipe 12, via an apparatus that back-extracts metal ions from the oil phase.

[0109] In the multi-cycle extraction method of the present invention, steps 2B and 2C, in which a pH adjustment step is performed when mixing the two phases in step 1 of each cycle, are preferred in that they can improve the mixing state of the two phases, and step 2C, in which a pH-adjusted aqueous phase and / or a pH-adjusted oil phase is used, is more preferred in that it can further improve the mixing state of the two phases.

[0110] <Other Steps> The extraction method of the present invention may include steps other than steps 1 to 3 described above. For example, steps include back-extracting (isolating) metal ions from the oil phase separated in step 3 (a step of recycling the oil phase by back-extracting metal ions from the oil phase), recovering the back-extracted metal ions as a compound (salt), purifying the back-extracted metal ions or their compound, purifying the extractant recovered from the oil phase, and further, removing ions of metal elements belonging to group 1 or group 2 of the periodic table from the aqueous phase in advance. Known methods can be applied without particular limitation as methods for recovering the back-extracted metal ions as a compound.

[0111] Despite being a simple method using the flow mixing method described above, the extraction method of the present invention can extract at least one metal ion from two or more metal ions contained in the aqueous phase into the oil phase with high selectivity, even in a short time, and preferably with a high extraction yield. Therefore, the extraction method of the present invention can also be described as a method for separating and recovering a specific metal ion from two or more metal ions present in the aqueous phase.

[0112] The specific metal ion to be extracted or separated and recovered is not uniquely determined by the group or period of the metal ion, its content, the type of extractant, etc. For example, when extracting metal ions belonging to Group 9 and metal ions belonging to Group 10 into the oil phase, the metal ions belonging to Group 9 can be separated and recovered with high selectivity, preferably with a high extraction amount. In particular, when extracting Co ions as Group 9 metal ions and Ni ions as Group 10 metal ions, Co ions can be separated and recovered with high selectivity, preferably with a high extraction amount. Similarly, when extracting metal ions belonging to Group 7 and metal ions belonging to Group 9 into the oil phase, the metal ions belonging to Group 7 can be separated and recovered with high selectivity, preferably with a high extraction amount. In particular, when extracting Mn ions as Group 7 metal ions and Co ions as Group 9 metal ions, Mn ions can be separated and recovered with high selectivity, preferably with a high extraction amount. Furthermore, when extracting metal ions belonging to Group 9 and metal ions belonging to Group 11 into the oil phase, the metal ions belonging to Group 11 can be separated and recovered with high selectivity, preferably with a high extraction yield. Also, when extracting metal ions belonging to Group 2 and metal ions belonging to Group 7 into the oil phase, the metal ions belonging to Group 7 can be separated and recovered with high selectivity, preferably with a high extraction yield. In particular, when extracting Mg ions as Group 2 metal ions and Mn ions as Group 7 metal ions, Mn ions can be separated and recovered with high selectivity, preferably with a high extraction yield. Also, when extracting metal ions belonging to Group 7 and metal ions belonging to Group 10 into the oil phase, the metal ions belonging to Group 7 can be separated and recovered with high selectivity, preferably with a high extraction yield. In particular, when extracting Mn ions as Group 7 metal ions and Ni ions as Group 10 metal ions, Mn ions can be separated and recovered with high selectivity, preferably with a high extraction yield. Furthermore, when extracting metal ions belonging to Group 10 and metal ions belonging to Group 11 into the oil phase, the metal ions belonging to Group 11 can be separated and recovered with high selectivity, preferably with a high extraction amount. In particular, when extracting Ni ions as metal ions belonging to Group 10 and Cu ions as metal ions belonging to Group 11, the Cu ions can be separated and recovered with high selectivity, preferably with a high extraction amount.Furthermore, when extracting metal ions belonging to Group 9, Group 10, and Group 12 into the oil phase, the metal ions belonging to Group 10 are usually not extracted, while the metal ions belonging to Group 12 can be separated and recovered with high selectivity, preferably in high quantities.

[0113] As described above, the extraction method of the present invention can extract a specific metal ion from among two or more metal ions present in the aqueous phase into the oil phase with high selectivity, preferably with a high extraction yield, and recover it. In particular, the extraction method of the present invention can extract two or more metal ions present in the aqueous phase while recovering one of them with high selectivity, preferably with a high extraction yield. Therefore, by subjecting the aqueous phase containing two or more metal ions back-extracted from the oil phase to the extraction method of the present invention, the selectivity of one metal ion can be further increased without significantly impairing the recovery amount (recovery rate), and as a result, high-purity metal ions can be recovered in high amounts (recovery rates).

[0114] <Extractant> The extractant used in the extraction method of the present invention is not particularly limited, and examples include extractants used in wet extraction methods, with extractants used in wet extraction methods for metal ions being preferred. More preferably, in terms of selectivity and extraction yield, the extractant used in the extraction method of the present invention is an acidic extractant consisting of an acidic compound having at least one active hydrogen atom, and examples of acidic extractants include various known acidic extractants or phosphoric acid compounds represented by the following formula (I). Examples of active hydrogen atoms include hydroxyl groups (including phenolic hydroxyl groups and hydroxyl groups bonded to phosphorus or sulfur atoms), carboxyl groups, and active hydrogen atoms in sulfanyl groups. The acidic extractant exhibits acidity, and the pKa is not particularly limited and can take an appropriate value, but is preferably 0.1 to 12. The pKa can be measured by neutralization titration.

[0115] Known acidic extractants include phosphoric acid compounds, carboxylic acid compounds, sulfonic acid compounds, oxime compounds, β-diketone compounds, and oxin compounds. Phosphoric acid compounds include phosphoric acid compounds, phosphonic acid compounds, phosphinic acid compounds, and various compounds in which the oxygen atom of these compounds is replaced with a sulfur atom or a nitrogen atom. Carboxylic acid compounds include compound VA-10, which was used in the examples described later.

[0116] The acidic extractant used in the extraction method of the present invention is preferably a compound represented by the following formula (I), as this can further enhance the selectivity of the metal ions to be extracted and preferably increase the extraction yield. The compound represented by the following formula (I) includes a phosphate group, a phosphonic acid group, a phosphinic acid group, and a compound having an acid group in which at least one oxygen atom of these acid groups is replaced with a sulfur atom or a nitrogen atom. For example, a phosphate ester compound (R １ OP(=O)(OH)-OR ２ ), phosphonic acid ester compounds (R １ -P(=O)(OH)-OR ２ , R １ OP(=O)(OH)-R ２ ) or phosphinate compounds (R １ -P(=O)(OH)-R ２ This includes phosphate compounds such as ), thiophosphate compounds obtained by converting at least one oxygen atom in each of the above phosphate compounds to a sulfur atom, and compounds obtained by further replacing the oxygen atom (-O-) bonded to P with a nitrogen atom. The acidic extractant represented by (Formula I) is preferably a phosphate compound in terms of selectivity and preferably the amount of extractable, more preferably a phosphate ester compound, a phosphonic acid ester compound, or a phosphinic acid ester compound, even more preferably a phosphonic acid ester compound or a phosphinic acid ester compound, and particularly preferably a phosphonic acid monoester compound or a phosphinic acid monoester compound.

[0117] In (Equation I), R １ and R ２Each of these indicates a substituent. However, R １ and R ２ At least one substituent is a hydrocarbon group having 9 or more carbon atoms. １ and R ２ The substituents that can be used are not particularly limited and include various substituents and groups formed by combinations of substituents. In the present invention, the above "various substituents" alone are R １ and R ２ A substituent is a substituent that becomes a substituent, and the above-mentioned "group with a combination of substituents" refers to a substituent formed by combining multiple substituents. In order to clearly distinguish between the above-mentioned "various substituents" and the above-mentioned "group with a combination of substituents," for convenience, the above-mentioned "various substituents" are sometimes called "single substituents," and the above-mentioned "group with a combination of substituents" are sometimes called "composite substituents." A composite substituent is formed by removing hydrogen atoms from a required number of single substituents from among the single substituents that constitute it, and then bonding multiple single substituents. In a composite substituent, the position in which a particular substituent is substituted by another substituent is not particularly limited and can be determined as appropriate. For example, when a phenyl group is substituted by another substituent, the substitution position may be any of the positions 2 to 4 with respect to the bonding position of the phenyl group. In the present invention, R １ and R ２ Substituents that can be taken as such are interpreted as single substituents whenever possible. For example, the 2-ethylhexyl group can be interpreted as a composite substituent in which an ethyl group substitutes a hexyl group, but it is interpreted as a branched alkyl group. Similarly, the hexyloxy group can be interpreted as a composite substituent combining a hexyl group and an oxygen atom, but it is interpreted as an alkoxy group.

[0118] R １ and R ２ The substituents that can be used (including single substituents and complex substituents) may be hydrocarbon groups composed only of carbon and hydrogen atoms, or they may be heteroatom-containing substituents containing at least one heteroatom such as a nitrogen atom, an oxygen atom, or a sulfur atom. １ and R ２It is preferable, in terms of selectivity and preferably extractable amount, that all possible substituents are hydrocarbon groups. The heteroatom-containing substituent preferably contains an oxygen atom or a sulfur atom as the heteroatom, and preferably contains an oxygen atom. The number of heteroatoms contained in the heteroatom-containing substituent is not particularly limited and can be 1 to 4, and preferably 1. In the heteroatom-containing substituent, the heteroatom may be located anywhere in the substituent, for example, inside or at the end of the atomic chain constituting the substituent. A heteroatom-containing substituent (e.g., an alkoxy group) in which the bonding heteroatom is located at the end is, on its own, R １ and R ２ It is preferable that the substituent does not become a substituent that can be taken as such. There are no particular limitations on heteroatom-containing substituents, and examples include complex substituents such as alkoxy groups, aryloxy groups, heterocyclic oxy groups, alkylthio groups, arylthio groups, heterocyclic thio groups, etc., which are combined with an aryl group (substituents including a ring structure), as described in substituent G below.

[0119] R １ and R ２ The individual substituents that can be used are not particularly limited, and any suitable substituents can be cited, for example, groups selected from substituent G described later. Among these, hydrocarbon groups such as alkyl groups, alkenyl groups, alkynyl groups, and aryl groups, and heterocyclic groups are preferred, and alkyl groups are even more preferred in terms of selectivity and preferably extractable amount.

[0120] The alkyl groups, alkenyl groups, and alkynyl groups that can be taken as individual substituents may be linear, branched, or cyclic, but branched chains are more preferred in terms of selectivity and preferably extractable amount. The aryl groups and heterocyclic groups that can be taken as individual substituents are the same as the corresponding groups in substituent G described later.

[0121] R １ and R ２The composite substituents that can be used are not particularly limited and include groups formed by combining multiple substituents selected from (single) substituents, for example, substituent G. The number of single substituents constituting the composite substituent is not particularly limited and can be 2 to 6, and preferably 2 to 4. Examples of composite substituents include groups formed by combining hydrocarbon groups (groups formed by combining an alkyl group, alkenyl group, or alkynyl group with an aryl group), groups formed by combining a hydroxyl group with an aryl group (hydroxyaryl group), groups formed by combining an alkoxy group or alkylthio group with an aryl group, and groups formed by combining an alkyl group, alkenyl group, or alkynyl group with an amino group. When the composite substituent contains an oxygen atom or sulfur atom bonded to an alkyl group, the oxygen atom and sulfur atom are interpreted as atoms derived from the alkoxy group or alkylthio group. For example, the composite substituent "alkyl group-oxygen atom-phenyl group-" is interpreted as a group formed by combining an alkoxy group and a phenyl group, and not as a group formed by combining an alkyl group and a phenoxy group, nor as a group formed by combining an alkyl group, an oxygen atom, and a phenyl group. The above interpretation also applies when the complex substituent contains an oxygen atom bonded to an alkenyl group or alkynyl group.

[0122] As for the compound substituent, those containing a ring structure are preferred in terms of selectivity, and preferably in terms of extractability. The ring structure contained in the compound substituent is not particularly limited, and examples include ring structures derived from cycloalkyl groups, aryl groups, heterocyclic groups, etc., with ring structures derived from aryl groups and aromatic heterocyclic groups being preferred, and ring structures derived from aryl groups being more preferred in terms of selectivity, and preferably in terms of extractability. Specifically, as for the compound substituent containing a ring structure, preferred are groups that combine an alkyl group and an aryl group, alkoxy groups or groups that combine an alkylthio group and an aryl group, alkoxyaryl groups are more preferred, and alkoxyphenyl groups are even more preferred.

[0123] R １ and R ２As for the substituents that can be used, among those mentioned above, alkyl groups, or composite substituents containing a ring structure combining an alkoxy group or an alkylthio group with an aryl group are preferred in terms of selectivity and preferably the amount of extractable material. Of the above preferred substituents, alkoxy groups, alkylthio groups, and composite substituents containing a ring structure are preferably those with 9 or more carbon atoms.

[0124] R １ Possible substituents and R ２ The combinations with substituents that can be taken as are not particularly limited, R １ and R ２ The substituents that can be taken as described above can be combined as appropriate. For example, the molecular structure of the substituent is not particularly limited, １ and R ２ The substituents that can be used are preferably combinations that include substituents having a branched structure (combinations in which at least one substituent has a branched structure) in terms of selectivity and preferably extractability, and more preferably combinations of substituents having branched structures, and more preferably combinations of substituents having a branched structure and substituents having a ring structure (particularly complex substituents). Here, the substituents having a branched structure are not particularly limited, but among those mentioned above, examples include hydrocarbon groups such as alkyl groups, alkenyl groups, and alkynyl groups, single substituents or complex substituents containing hydrocarbon groups, and more preferably single substituents such as alkyl groups, or complex substituents such as groups combining alkoxy groups or alkylthio groups with aryl groups, and more preferably groups combining alkyl groups or alkoxy groups with aryl groups. In the present invention, the substituent having a branched structure may be any substituent having 3 or more carbon atoms, but in terms of selectivity and preferably preferably extractability, it is preferable that the substituent has 9 or more carbon atoms.

[0125] Furthermore, there are no particular restrictions on the type of substituent, R １ and R ２In terms of selectivity, and preferably extractability, combinations of single substituents or combinations of a single substituent and a complex substituent are preferred. In the case of combinations of single substituents, the same (type) substituents may be combined, or different (type) substituents may be combined. Examples of combinations of the same substituents include combinations of alkyl groups, alkenyl groups, and alkynyl groups. In the above combinations of the same substituents, the carbon chains of the individual substituents to be combined may be the same or different, but it is preferable that they are all branched chains. Also, the number of carbon atoms of the individual substituents to be combined may be the same or different.

[0126] On the other hand, examples of combinations of different substituents include combinations in which one of the substituents is a hydrocarbon group, and combinations of two of alkyl groups, alkenyl groups, and alkynyl groups are more preferred. In the above combinations of different substituents, the carbon chains of the alkyl group, alkenyl group, or alkynyl group may be the same or different, but it is preferable that they are all branched chains. Also, the number of carbon atoms of the alkyl group, alkenyl group, or alkynyl group may be the same or different.

[0127] Preferred combinations of single substituents and composite substituents include alkyl groups, alkenyl groups, alkynyl groups, and composite substituents containing a ring structure, while preferred combinations of alkyl groups and composite substituents combining alkoxy and aryl groups are preferred.

[0128] R １ Possible substituents and R ２ Among the possible substituent combinations mentioned above, combinations of alkyl groups are particularly preferred in terms of selectivity, and preferably in terms of extractable amount.

[0129] In the compound represented by (Formula I), R １ and R ２ The substituents that can be taken as are the substituents mentioned above, which can be selected as appropriate, １ and R ２At least one substituent shall be a hydrocarbon group having 9 or more carbon atoms. １ and R ２ If at least one substituent is a hydrocarbon group having 9 or more carbon atoms, high selectivity can be achieved, and preferably a high extraction yield can also be achieved. In the present invention, in terms of selectivity, preferably extraction yield, R １ and R ２ When at least one of them is a hydrocarbon group having 9 or more carbon atoms, Z １ and Z ２ Preferably, one of the bonds is a single bond and the other is -O-. The total number of carbon atoms constituting the hydrocarbon group having 9 or more carbon atoms (hereinafter simply referred to as the number of carbon atoms) is preferably 10 or more, more preferably 12 or more, even more preferably 14 or more, and particularly preferably 16 or more, in terms of selectivity and preferably extractable amount. On the other hand, the upper limit of the number of carbon atoms is not particularly limited and can be determined as appropriate, for example, it can be 30 or less, preferably 24 or less, and more preferably 20 or less.

[0130] The hydrocarbon group having 9 or more carbon atoms is not particularly limited, but among the hydrocarbon groups mentioned above, alkyl groups, alkenyl groups, or alkynyl groups are preferred, and alkyl groups are more preferred. The hydrocarbon group having 9 or more carbon atoms may be linear or branched, but branched is preferred. When the hydrocarbon group having 9 or more carbon atoms is branched, the number of branched carbon atoms is not particularly limited as long as there is one or more, and examples include one or two branches and three or more branches. In the embodiment having three or more branched carbon atoms, the number of branched carbon atoms is the same as that of the hydrocarbon group having three or more branched carbon atoms described later. As for the hydrocarbon group having 9 or more carbon atoms, alkyl groups having 9 or more carbon atoms are preferred, and branched alkyl groups having one or more branched carbon atoms and 9 or more carbon atoms are more preferred. Examples of linear alkyl groups having 9 or more carbon atoms include n-nonyl group, n-decyl group, n-dodecyl group, n-tetradecyl group, n-hexadecyl group, etc. Examples of alkyl groups having 9 or more carbon atoms and one or two branched carbon atoms include 1-ethyl-1-methylhexane, 8-methylnonane, 2-butyloctane, 2-hexyldecane, 2-ethyldecane, 2-octyldecane, 2-hexyldodecane, 2-octyldodecane, and 2-decyltetradecane. Examples of alkyl groups having 9 or more carbon atoms and three or more branched carbon atoms include 2,5,7,7-tetramethyloctane, 2-(1,3,3-trimethyl-1-butyl)-5,7,7-trimethyloctane, 2-(1,3,3-trimethyl-1-butyl)-5,7,7-trimethyloctane, and 2-(4-methylhexyl)-8-methyldecyl.

[0131] In the compound represented by (Formula I), R １ and R ２ The substituents that can be taken can be appropriately selected from the substituents mentioned above, but when considering the molecular structure and number of carbon atoms of the substituent, in terms of selectivity, preferably in terms of extractable amount, R １ and R ２ Preferably, at least one of them is a hydrocarbon group having three or more branched carbon atoms.

[0132] Hydrocarbon groups having three or more branched carbon atoms are not particularly limited, but typically include alkyl groups, alkenyl groups, or alkynyl groups with a branched structure that have three or more branched carbon atoms (tertiary carbon atoms). The number of branched carbon atoms present in this hydrocarbon group is not particularly limited as long as there are three or more, for example, it can be 3 to 8, preferably 3 to 6, and more preferably 4 to 6. The number of carbon atoms in a hydrocarbon group having three or more branched carbon atoms is not particularly limited, but preferably 9 or more, and preferably 12 or more. That is, it is preferable for a hydrocarbon group with 9 or more carbon atoms to have three or more branched carbon atoms. Such hydrocarbon groups are as described above.

[0133] R １ and R ２ The other of these may be a hydrocarbon group having 9 or more carbon atoms, or a substituent other than a hydrocarbon group having 9 or more carbon atoms. In the present invention, in terms of selectivity, preferably in terms of extractable amount, R １ and R ２ The other substituent is preferably a hydrocarbon group, and a hydrocarbon group having 8 or fewer carbon atoms is also a preferred embodiment. Examples of hydrocarbon groups having 8 or fewer carbon atoms include alkyl groups, alkenyl groups, alkynyl groups, and aryl groups, with alkyl groups being preferred. The hydrocarbon group may be linear, branched, or cyclic, but a branched chain is more preferred in terms of selectivity and preferably extractable amount. The number of branched carbon atoms in the branched chain may be one or more, for example, preferably 1 to 5, and preferably 1. The total number of carbon atoms constituting the hydrocarbon group having 8 or fewer carbon atoms is preferably 1 to 8, more preferably 3 to 8, and even more preferably 5 to 8.

[0134] In this embodiment, R １ Possible substituents and R ２ The possible combinations with substituents are not particularly limited, and either substituent may be a hydrocarbon group having 9 or more carbon atoms, and it is preferable that the substituent includes a hydrocarbon group having 9 or more carbon atoms and 3 or more branched carbon atoms.１ and R ２ The substituent that can be the other is not particularly limited and may be a hydrocarbon group having 9 or more carbon atoms, or a substituent other than a hydrocarbon group having 9 or more carbon atoms (preferably a hydrocarbon group having 8 or fewer carbon atoms).

[0135] In formula I, X represents -OH or -SH, and is preferably -OH. In formula I, Y represents an oxygen atom or a sulfur atom, and is preferably an oxygen atom. In formula I, Z １ and Z ２ Each represents a single bond, -O-, -NH-, or -S-, and is preferably a single bond or -O-. In (Formula I), Z １ and Z ２ Both are preferably single bonds or -O- bonds, Z １ and Z ２ Among these combinations, in terms of selectivity and preferably the amount extracted, Z １ and Z ２ It is more preferable that one of the bonds is a single bond and the other is -O-.

[0136] The compound represented by (Formula I) is, in (Formula I), R １ and R ２ And Y, X, Z １ and Z ２ They can be formed by combining them as appropriate, and it is preferable to form them by combining preferred symbols. In formula (I), R １ -Z １ - and R ２ -Z ２ Even if - has a substituent -O-, -S-, or -NH-, and these can be interpreted as a single substituent (e.g., an alkoxy group), if these are not interpreted as a single substituent, -O-, -S-, or -NH- are treated as Z １ or Z ２ Let the substituent be R １ or R ２ This is how it is interpreted. In the present invention, R １ and R ２ and Z １ and Z ２As for combinations, various combinations are possible, but in terms of initial extraction volume and repeated durability, R １ and R ２ In a preferred embodiment, both are hydrocarbon groups having 9 or more carbon atoms, and R １ and R ２ In another preferred embodiment, one of the atoms is a hydrocarbon group having 9 or more carbon atoms, and the other is a substituent other than a hydrocarbon group having 9 or more carbon atoms (preferably a hydrocarbon group having 8 or fewer carbon atoms). In another preferred embodiment, the hydrocarbon group having 9 or more carbon atoms forms a single bond with Z １ or Z ２ Z may be bound to -O-, -NH-, or -S- in terms of initial extraction volume and repeated durability. １ or Z ２ It is preferable that it is bonded to R. １ and R ２ and Z １ and Z ２ A preferred specific combination is the combination of extractants E-1 to E-3 in the examples described later.

[0137] The molecular weight of the compound represented by (Formula I) is not particularly limited, but can be, for example, 350 to 50,000, and if the oil phase contains an organic solvent, it is preferably 400 to 10,000 in terms of solubility in the organic solvent.

[0138] The compound represented by (Formula I) may have substituents, and examples of substituents include groups selected from substituent G described later. The compound represented by (Formula I) can be synthesized by referring to known synthesis methods, such as the synthesis method described in the examples described later.

[0139] Specific examples of compounds represented by (Formula I) include those synthesized in the examples, as shown below, but the present invention is not limited to these.

[0140]

[0141] - Substituent G - Alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, e.g., methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), alkenyl group (preferably an alkenyl group having 2 to 20 carbon atoms, e.g., vinyl, allyl, oleyl, etc.), alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, e.g., ethynyl, butadiinyl, phenylethynyl, etc.), cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms, e.g., cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.) In this invention, the term alkyl group usually includes cycloalkyl groups, but this is described separately here.), aryl groups (preferably aryl groups having 6 to 26 carbon atoms, e.g., phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), aralkyl groups (preferably aralkyl groups having 7 to 23 carbon atoms, e.g., benzyl, phenethyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, more preferably heterocyclic groups of 5 or 6 members having at least one oxygen atom, a sulfur atom, or a nitrogen atom. Heterocyclic groups include aromatic heterocyclic groups and aliphatic heterocyclic groups.For example, tetrahydropyran ring group, tetrahydrofuran ring group, 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, pyrrolidone group, etc.), alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyloxy, benzyloxy, etc.), aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.), heterocyclic oxy group (a group in which an -O- group is bonded to the above heterocyclic group), alkoxycarbonyl group (preferably Or, alkoxycarbonyl groups having 2 to 20 carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxycarbonyl, dodecyloxycarbonyl, etc.), aryloxycarbonyl groups (preferably aryloxycarbonyl groups having 7 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl, 4-methoxyphenoxycarbonyl, etc.), heterocyclic oxycarbonyl groups (groups in which an -O-CO- group is bonded to the above heterocyclic group), amino groups (preferably amino groups having 0 to 20 carbon atoms, alkylamino groups, arylamino groups, for example, amino(-NH). ２), N,N-dimethylamino, N,N-diethylamino, N-ethylamino, anilino, etc.), sulfamoyl group (preferably a sulfamoyl group having 0 to 20 carbon atoms, for example, N,N-dimethylsulfamoyl, N-phenylsulfamoyl, etc.), acyl group (including alkylcarbonyl group, alkenylcarbonyl group, alkynylcarbonyl group, arylcarbonyl group, heterocyclic carbonyl group, preferably an acyl group having 1 to 20 carbon atoms, for example, acetyl, propionyl, butyryl, octanoyl, hexadecanoyl, acryloyl, methacryloyl, crotonoyl, benzoyl, naphthoyl, nicotinoyl, etc.), acyl Oxy groups (including alkylcarbonyloxy groups, alkenylcarbonyloxy groups, alkynylcarbonyloxy groups, and heterocyclic carbonyloxy groups, preferably acyloxy groups having 1 to 20 carbon atoms, for example, acetyloxy, propionyloxy, butyryloxy, octanoyloxy, hexadecanoyloxy, acryloyloxy, methacryloyloxy, crotonoyloxy, nicotinoyloxy, etc.), allyloxy groups (preferably allyloxy groups having 7 to 23 carbon atoms, for example, benzoyloxy, naphthoyloxy, etc.), carbamoyl groups (preferably carbamoyl groups having 1 to 20 carbon atoms, for example, N,N-dimethylcarbamoyl, N-phenylcarbamoyl, etc.), acylamino group (preferably an acylamino group having 1 to 20 carbon atoms, e.g., acetylamino, benzoylamino, etc.), alkylthio group (preferably an alkylthio group having 1 to 20 carbon atoms, e.g., methylthio, ethylthio, isopropylthio, benzylthio, etc.), arylthio group (preferably an arylthio group having 6 to 26 carbon atoms, e.g., phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio, etc.), heterocyclic thio group (a group in which an -S- group is bonded to the above heterocyclic group), alkylsulfonyl group (preferably an alkylsulfonyl group having 1 to 20 carbon atoms, e.g., methylsulfonyl, ethylsulfonyl, etc.), arylsulfonyl group (preferably carbon Arylsulfonyl groups with 6 to 22 carbon atoms, for example, benzenesulfonyl), alkylsilyl groups (preferably alkylsilyl groups with 1 to 20 carbon atoms, for example, monomethylsilyl, dimethylsilyl, trimethylsilyl, triethylsilyl), arylsilyl groups (preferably arylsilyl groups with 6 to 42 carbon atoms, for example, triphenylsilyl), alkoxysilyl groups (preferably alkoxysilyl groups with 1 to 20 carbon atoms, for example, monomethoxysilyl, dimethoxysilyl, trimethoxysilyl, triethoxysilyl), aryloxysilyl groups (preferably aryloxysilyl groups with 6 to 42 carbon atoms, for example, triphenyloxysilyl), phosphoryl groups (preferably phosphate groups with 0 to 20 carbon atoms, for example, -OP(=O)(R, Ｐ ) ２ ), phosphonyl group (preferably a phosphonyl group having 0 to 20 carbon atoms, for example, -P(=O)(R Ｐ ) ２ ), phosphenyl group (preferably a phosphenyl group having 0 to 20 carbon atoms, for example, -P(R Ｐ ) ２ ), phosphonic acid group (preferably a phosphonic acid group having 0 to 20 carbon atoms, for example, -PO(OR Ｐ ) ２ Examples include sulfo groups (sulfonic acid groups), carboxyl groups, hydroxyl groups, sulfanyl groups, cyano groups, and halogen atoms (e.g., fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc.). Ｐis a hydrogen atom or a substituent (preferably a group selected from substituent G). Furthermore, each of the groups listed as substituent G may be further substituted with substituent G. The alkyl group, alkylene group, alkenyl group, alkenylene group, alkynyl group and / or alkynylene group, etc. may be cyclic or linear, and may be linear or branched.

[0142] The present invention will be described in more detail below based on examples, but the present invention is not to be construed as being limited thereto. In the following examples, "parts" and "%" representing the composition are by mass unless otherwise specified. In the present invention, "room temperature" means 25°C.

[0143] [Synthesis and Preparation of Compounds] The compounds shown below will be synthesized or prepared. PC-88A ((2-ethylhexyl)phosphonic acid mono-2-ethylhexyl) shown below will be a commercially available product (manufactured by Tokyo Chemical Industry Co., Ltd.). VA-10 shown below will be a commercially available product (Versatic acid 10, manufactured by Hexion Co., Ltd.). Cyanex272 shown below will be a commercially available product (di(2,4,4-trimethylpentyl)phosphinic acid, manufactured by Science Co., Ltd.).

[0144]

[0145] <Synthesis of Compound E-1> Compound E-1 can be synthesized as follows. Specifically, 89 g of diethyl phosphite (manufactured by Tokyo Chemical Industries, Ltd.) and 450 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) are added to a 1 L three-necked round-bottom flask and stirred well. While cooling the three-necked round-bottom flask with ice, 23.2 g of sodium hydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is added and stirred for 20 minutes while still ice-cooled. After that, the reaction mixture is heated and stirred in a flux state for 30 minutes. Next, while cooling the three-necked round-bottom flask with ice, 70.0 g of 1-bromo-2-ethylhexane (manufactured by Tokyo Chemical Industries, Ltd.) is added dropwise to the obtained reaction mixture over 20 minutes, and then stirred at an internal temperature of 45°C for 24 hours. After adding 300 g of water to the reaction mixture obtained in this way, extraction is performed with toluene, and the solvent is removed by vacuum distillation to obtain 105 g of a yellow liquid.

[0146] Next, add the obtained yellow liquid and 400 g of dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to a 1 L three-necked round-bottom flask and stir well. Add 113 g of bromotrimethylsilane (manufactured by Tokyo Chemical Industries, Ltd.) to the three-necked round-bottom flask and stir at room temperature for 4 hours. After removing the solvent from the obtained reaction solution under reduced pressure, add 530 g of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and stir at an internal temperature of 40°C for 3 hours. Add 200 mL of aqueous sodium hydroxide solution (4 mol / L) to the reaction solution obtained in this way, and wash the aqueous phase twice with toluene. Add 65 mL of concentrated hydrochloric acid to the obtained aqueous solution, extract with toluene, and then remove the solvent under reduced pressure to obtain 41.2 g of compound A (yield 59%, 2 steps). Add 20.0 g of compound A to a 500 mL three-necked flask and Fineoxocol 180N (branched C １８ H ３７ Add 23.6 g of OH (manufactured by Nissan Chemical Industries) and 120 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), stir, and raise the temperature to a flux state. Then, add a solution of 23.4 g of dicyclohexylcarbodiimide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) dissolved in 120 g of tetrahydrofuran dropwise over 3 hours, and stir for 4 hours. Allow the resulting reaction solution to return to room temperature, remove the white solid by filtration, and remove the solvent from the obtained filtrate under reduced pressure. Dissolve the obtained crude product in toluene, wash with water, and then remove the solvent under reduced pressure to obtain 30.5 g (yield 71%) of compound E-1, a pale yellow liquid.

[0147] The synthesized compound E-1 is, １ Identification can be performed using m / z values ​​obtained from H-NMR (instrument: BRUKER 400) and HPLC-MS.

[0148] <Synthesis of Compound E-2> In the synthesis of Compound E-1, 1-bromo-2-ethylhexane and fineoxocol 180N are used as shown in the above chemical formula R １ and R ２ Compound E-2 can be synthesized in the same manner as compound E-1, except that the corresponding group is changed to a bromide and an alcohol. The synthesized compound E-2 can be identified in the same manner as compound E-1.

[0149] <Synthesis of Compound E-3> Fineoxocol 180N (branched C) in a 500 mL three-necked round-bottom flask. １８ H ３７ Add 20.0 g of OH (manufactured by Nissan Chemical Industries), 39.4 g of carbon tetrabromide (manufactured by Fujifilm Wako Pure Chemical Industries), and 130 g of dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries), and stir while cooling in an ice bath. To the resulting reaction solution, add a solution consisting of 39.0 g of triphenylphosphine (manufactured by Fujifilm Wako Pure Chemical Industries) and 110 g of dichloromethane dropwise over 10 minutes. Then, raise the temperature of the reaction solution to room temperature and stir for 2 hours. Add a 4 M sodium hydroxide solution to this solution, extract with dichloromethane, and then remove the solvent under reduced pressure to obtain the product (branched C １８ H ３７ Br) can be obtained as a pale yellow liquid (yield 92%). Add 1.5 g of magnesium (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 100 g of diethyl ether to a 300 mL three-necked round-bottom flask and stir at room temperature. Add 18.0 g of the above product dropwise to generate Grignard's reagent. Subsequently, while maintaining the temperature of the reaction mixture below 15°C, add 4.2 g of dibutyl phosphite, then raise the temperature of the reaction mixture and stir under flux for 5 hours. While cooling the resulting reaction mixture in an ice bath, add 10% sulfuric acid dropwise, wash the organic layer with 15% aqueous sodium carbonate solution, and remove the solvent under reduced pressure. The obtained crude product is purified by column chromatography and branched C is obtained by substituting the two hydroxyl groups respectively. １８ H ３７ Two-group phosphorous acid can be obtained as a colorless, transparent liquid (85% yield). 78 g of hydrogen peroxide solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 10.0 g of the above-mentioned phosphorous acid are added to a 200 mL three-necked round-bottom flask and stirred at room temperature. The reaction mixture is then heated to 65°C and stirred for 24 hours. After adding 100 g of saturated sodium thiosulfate aqueous solution, the mixture is extracted with toluene, and the solvent is removed by reduced pressure to obtain compound E-3 as a colorless, transparent liquid (95% yield). The synthesized compound E-3 can be identified in the same manner as compound E-1.

[0150] [Preparation of Metal Ion-Containing Aqueous Solutions W1 to W4] <Preparation of Co Ion and Ni Ion-Containing Aqueous Solution W1> Add 57.2 g of cobalt(II) sulfate heptahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 53.7 g of nickel(II) sulfate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to a 1 L volumetric flask, make up with ultrapure water, and dissolve by stirring at 40°C. Then cool to room temperature (25°C) to prepare Co ion and Ni ion-containing aqueous solutions as metal ion-containing aqueous solution W1. The density of this aqueous solution W1 according to the above measurement method is 1.06 × 10⁻⁶ ３ kg / m ３ The following is the preparation of the Mn and Ni ion-containing aqueous solution W2: <Preparation of Mn and Ni ion-containing aqueous solution W2> Except for adding 52.6 g of manganese(II) sulfate pentahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) instead of 57.2 g of cobalt(II) sulfate heptahydrate in the preparation of the Co and Ni ion-containing aqueous solution W1, the Mn and Ni ion-containing aqueous solution W2 is prepared in the same manner as the preparation of the Co and Ni ion-containing aqueous solution W1. The density of this aqueous solution W2 measured by the above method is 1.06 × 10⁻⁶ ３ kg / m ３ The following is the preparation of the Mn and Mg ion-containing aqueous solution W3: In the preparation of the Co and Ni ion-containing aqueous solution W1, the Mn and Mg ion-containing aqueous solution W3 is prepared in the same manner as the preparation of the Co and Ni ion-containing aqueous solution W1, except that 52.6 g of manganese(II) sulfate pentahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is added instead of 57.2 g of cobalt(II) sulfate heptahydrate, and 121.5 g of magnesium(II) sulfate heptahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is added instead of 53.7 g of nickel(II) sulfate hexahydrate. The density of this aqueous solution W3 according to the above measurement method is 1.08 × 10⁻⁶. ３ kg / m ３The following is the preparation of the Cu and Ni ion-containing aqueous solution W4: <Preparation of Cu and Ni ion-containing aqueous solution W4> The Cu and Ni ion-containing aqueous solution is prepared in the same manner as the preparation of the Co and Ni ion-containing aqueous solution W1, except that 47.1 g of copper(II) sulfate pentahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is added instead of 57.2 g of cobalt(II) sulfate heptahydrate. The density of this aqueous solution W4 measured by the above method is 1.05 × 10⁻⁶. ３ kg / m ３ That is the case.

[0151] The content (concentration CI) of each metal ion in each ion-containing aqueous solution W1 to W4 prepared as described above is 1.2 × 10⁻⁶. ４ It is ppm.

[0152] <Preparation of Extractant Solution (Oil Phase)> Add the synthesized or prepared extractant and the required amount of pH adjusting agent-containing aqueous solution (4M sodium hydroxide aqueous solution or 4M hydrochloric acid) to the pH at the time of mixing shown in the "pH" column of Table 1 to a 1 L volumetric flask. Dissolve each extractant solution by stirring after making up the volume with kerosene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) at room temperature. The extractant concentration in each extractant solution is 500 mM. The density of each extractant solution measured by the above method is 8.4 × 10⁻⁶. ２ kg / m ３ That is the case.

[0153] As the extraction device, the extraction device 1 (flow reactor) shown in Figure 1 is prepared. The inner diameter (equivalent diameter) of the aqueous phase flow pipe 11 and the oil phase flow pipe 12 is 8 mm. The length of the tip section 11a and the tip section 12a and the inner diameter (equivalent diameter) of the open end are 8 mm and 0.8 mm, respectively. Therefore, the ratio of the inner diameter of the open end of the tip section to the inner diameter of each flow pipe (reduction ratio of flow diameter) is 0.1. The confluence section 13 is a cylindrical pipe body with the same diameter as the inner diameter of the open ends of the tip sections 11a and 12a, and its length (distance between the aqueous phase flow pipe 11 and the oil phase flow pipe 12) is 20 mm. The mixing section 14 has a pre-mixing section 14a and a post-mixing section 14b, which consist of a wide tip section and a pipe section with a constant inner diameter. The connection port diameter (equivalent diameter) of the wide tip section to the confluence section 13 is 0.5 mm, and the inner diameter (equivalent diameter) of the pipe section is 8 mm. The inner diameter (equivalent diameter) of the downstream mixing section 14b shall be 8 mm. The total length of the upstream mixing section 14a and the downstream mixing section 14b shall be adjusted to the length indicated in the "Mixing Section Length" column of Table 1. The total length of the mixing section 14 shall be determined by referring to the value of the equilibrium attainment in the batch extraction method described above in the extraction method of the present invention, so as to achieve the above-mentioned mixing state. The separation section 16 shall use a vial tube with an inner diameter of 36 mm. Note that the pH adjusting agent-containing aqueous solution storage tank 7 and the pH adjusting agent transfer pipe 15 are not provided.

[0154] [Example 1] In Example 1, metal ions are extracted using an extraction apparatus 1 equipped with a mixing section 14 having the length shown in the "Length of Confluence Section" column of Table 1, under the conditions shown in Table 1. Specifically, a metal ion-containing aqueous solution W1 (25°C) stored in the aqueous phase storage tank 5 is sent from the aqueous phase flow pipe 11 to the confluence section 13 at a flow rate (flow velocity) of 12.0 mL / min (internal pressure of 0.13 MPa), and the metal ion-containing aqueous solution W1 and the oil phase are combined in the confluence section 13, and the combined liquid is continued to flow through the mixing section 14 at 25°C (Steps 1 and 2C). The confluence conditions and mixing conditions in Steps 1 and 2C are shown in the "Confluence Conditions and Mixing Conditions" column of Table 1 (the same applies to Examples 2 to 11 and Comparative Examples 3 and 4). The flow rate of the combined liquid circulating within the confluence section 14 is 24.0 mL / min. As shown in the "Co equilibrium reached" and "Ni equilibrium reached" columns of Table 1, the three-liquid combined liquid flowing out from the downstream mixing section 14b shows that the Co ions have reached extraction equilibrium, while the Ni ions have not. The three-liquid combined liquid is then transferred to a vial tube serving as the separation section 16 and collected. The three-liquid combined liquid is then allowed to stand at the same temperature to confirm that the organic phase (oil phase) and aqueous phase have separated into two phases. The aqueous phase is then separated (step 3) to perform selective extraction of Co ions. In Example 1, the liquid residence time was 10 minutes, the flow time in the mixing section 14 (from the confluence section 13 to the separation section 16) was 9 minutes, and the time required for phase separation was 1 minute. The pH and the content of Co ions and Ni ions in the aqueous phase (25°C) thus extracted are measured. The content (residual amount) of Co ions and Ni ions is measured using an inductively coupled plasma atomic emission spectrometer (ICP-OES) (Optima 7300D (trade name), manufactured by PerkinElmer). The pH is measured using a pH meter (SK-620pHII, manufactured by Satotec).

[0155] [Examples 2-5] Examples 2-5 involve extracting metal ions by changing the length of the mixing section 14. Specifically, in Example 1, the total length of the mixing section 14 is changed to the length shown in the "Mixing Section Length" column of Table 1, and the flow rates of the metal ion-containing aqueous solution W1 and the oil phase are changed to the values ​​shown in the "Flow Rate" column of Table 1 as necessary. Otherwise, selective extraction of Co ions in Examples 2-5 is performed in the same manner as in Example 1, and the pH of the aqueous phase and the content of Co ions and Ni ions are measured in the same manner as in Example 1. In Example 2, the liquid residence time was 5 minutes, the flow time in the mixing section 14 was 4 minutes, and the time required for phase separation was 1 minute. In Example 3, the liquid residence time was 3 minutes, the flow time in the mixing section 14 was 2 minutes, and the time required for phase separation was 1 minute. In Example 4, the liquid residence time was 3 minutes, the flow time in the mixing section 14 was 2 minutes, and the time required for phase separation was 1 minute. In Example 5, the liquid residence time was 1 minute, the flow time in the mixing section 14 was 0.5 minutes, and the time required for phase separation was 0.5 minutes. In each example, the three-liquid mixture flowing out from the downstream mixing section 14b shows that the Co ions have reached extraction equilibrium, while the Ni ions have not, as shown in the "Co equilibrium attainment" and "Ni equilibrium attainment" columns of Table 1.

[0156] [Examples 6, 8-11] In Examples 6, 8-11, selective extraction of Co ions was performed in the same manner as in Example 3, except that the oil phase containing the extractant PC-88A in Example 3 was replaced with an oil phase containing the extractant shown in the "Extractant (Solution)" column of Table 1, to which the necessary amount of pH adjusting agent-containing aqueous solution to achieve the pH at the time of mixing shown in the "pH" column of Table 1 was added. The pH of the aqueous phase and the content of Co ions and Ni ions were measured in the same manner as in Example 1. In Examples 6, 8-11, the liquid residence time was 3 minutes in all cases, the flow time in the mixing section 14 was 2 minutes in all cases, and the time required for phase separation was 1 minute in all cases. In each example, the three-liquid mixture flowing out from the downstream mixing section 14b showed that Co ions had reached extraction equilibrium, while Ni ions had not reached extraction equilibrium, as shown in the "Co Equilibrium Achieved" column and "Ni Equilibrium Achieved" column of Table 1.

[0157] [Example 7] In Example 3, instead of the oil phase containing the extractant PC-88A, an oil phase containing the extractant shown in the "Extractant (Solution)" column of Table 1, with the necessary amount of pH adjusting agent-containing aqueous solution to achieve the pH at the time of mixing shown in the "pH" column of Table 1 added, was used. Furthermore, the three-liquid combined liquid was heated to 60°C using heaters installed on the outer circumference of the confluence section 13 and the mixing section 14, and the liquid was allowed to flow through the confluence section 13 and the mixing section 14 at the same temperature. Except for these differences, the selective extraction of Co ions in Example 7 was carried out in the same manner as in Example 1, and the pH of the aqueous phase and the content of Co ions and Ni ions after cooling to 25°C were measured in the same manner as in Example 1. In Example 7, the liquid residence time was 3 minutes, the flow time in the mixing section 14 was 2 minutes, and the time required for phase separation was 1 minute. In Example 7, the three-liquid mixture flowing out from the downstream mixing section 14b shows that the Co ions have reached extraction equilibrium, while the Ni ions have not, as shown in the "Co equilibrium attainment" and "Ni equilibrium attainment" columns of Table 1.

[0158] [Comparative Example 1] Comparative Example 1 extracts metal ions using a batch extraction method with a mixer settler (5L) instead of a flow extraction method. Specifically, a metal ion-containing aqueous solution W1 (25°C) and an oil phase (25°C) containing the extractant PC-88A are added to the mixer settler in amounts of 50% by volume of the mixer settler's capacity and stirred. Then, an aqueous solution containing a pH adjusting agent is added to control the pH to 4.7. After adjusting the internal temperature of the mixer settler to 25°C and stirring, the three-liquid mixture is allowed to stand at the same temperature. In Comparative Example 1, the liquid residence time was 10 minutes, the stirring time (corresponding to the flow time) was 5 minutes, and the standing time (time required for phase separation) was 5 minutes. As a result, the three-liquid mixture in Comparative Example 1 does not undergo phase separation.

[0159] [Comparative Example 2] The extraction for Comparative Example 2 was carried out in the same manner as in Comparative Example 1, except that the liquid residence time was changed to 20 minutes (the stirring time was changed to 10 minutes and the standing time was changed to 10 minutes). The phase-separated aqueous phase was recovered, and its pH and the content of Co ions and Ni ions were measured in the same manner as in Example 1. In Comparative Example 2, the three-liquid mixture flowing out from the downstream mixing section 14b had reached extraction equilibrium for both Co ions and Ni ions, as shown in the "Co equilibrium attainment" and "Ni equilibrium attainment" columns of Table 1.

[0160] [Comparative Examples 3 and 4] Examples 3 and 4 use an extraction apparatus 1 in which the length of the mixing section 14 is changed to the length shown in the "Confluence Section Length" column of Table 1, and metal ions are extracted under the conditions shown in Table 1. Specifically, the extraction for Comparative Examples 3 and 4 is carried out in the same manner as in Example 1, except that the total length of the mixing section 14 is changed to the length shown in the "Mixing Section Length" column of Table 1, and the liquid residence time is changed to the time shown in the "Liquid Residence Time" column of Table 1. In Comparative Example 3, the liquid residence time is 20 minutes, the flow time is 18 minutes, and the standing time is 2 minutes. In Comparative Example 4, the liquid residence time is 30 minutes, the flow time is 27 minutes, and the standing time is 3 minutes. The pH and the content of Co ions and Ni ions of each aqueous phase obtained in this manner are measured in the same manner as in Example 1. In each comparative example, the three-liquid mixture flowing out from the downstream mixing section 14b has reached extraction equilibrium for both Co and Ni ions, as shown in the "Co equilibrium attainment" and "Ni equilibrium attainment" columns of Table 1.

[0161] <Measurement of Equilibrium Achievement> For each metal ion in each example and comparative example, the degree of equilibrium achievement was measured and calculated using the batch extraction method described above, and the results of the equilibrium state determination (in parentheses) are shown in Table 1.

[0162] <Calculation of Kinetic Energy> In each example and comparative example, the kinetic energy E of both the aqueous phase and the oil phase was calculated. ＳＴ The results calculated as described above are shown in Table 1.

[0163] <Evaluation: Evaluation of Extraction Amount> In each example and comparative example, for the same metal ion, the extraction rate (unit: %) of the metal ion is calculated based on the following formula, using the metal ion concentration CI in the prepared metal ion-containing aqueous solution W1 and the metal ion concentration C1 in the aqueous phase after the extraction operation. Extraction rate (%) = [(CI - C1) / CI] × 100 In this test, for metal ions that reached extraction equilibrium (metal ions to be extracted), the extraction amount is evaluated based on evaluation criterion 1 below. The results are shown in Table 1. For metal ions to be extracted, a larger extraction rate indicates that a larger amount can be extracted into the oil phase. In this test, a value of D or higher is considered a pass. On the other hand, for metal ions that did not reach extraction equilibrium (metal ions other than those to be extracted), the extraction amount is evaluated based on evaluation criterion 2 below. The results are shown in Table 1. For metal ions other than those to be extracted, a smaller extraction rate indicates that the amount extracted into the oil phase can be reduced. In this test, a value of D or higher is considered a pass. For each example and comparative example, if the extraction ratio is D or higher for the target metal ion and D or higher for other metal ions, it is shown that the extraction of other metal ions can be suppressed, and the target metal ion can be selectively extracted into the oil phase. Note that the extraction rate R at the equilibrium point obtained in the calculation process of the equilibrium attainment in some examples and comparative examples is shown. Ｅ and the extraction rate R during the mixing time of each example and comparative example. Ｒ This is shown in Table 1A. - Evaluation Criteria 1 - A: Extraction rate of 98% or higher B: Extraction rate of 95% or higher, less than 98% C: Extraction rate of 90% or higher, less than 95% D: Extraction rate of 80% or higher, less than 90% E: Extraction rate of less than 80% - Evaluation Criteria 2 - A: Extraction rate of less than 10% B: Extraction rate of 10% or higher, less than 15% C: Extraction rate of 15% or higher, less than 20% D: Extraction rate of 20% or higher, less than 30% E: Extraction rate of 30% or higher

[0164]

[0165]

[0166] [Examples 12-14] Examples 12-14 are performed in the same manner as in Example 3, except that the metal ion-containing aqueous solution W1 used in Example 3 is replaced with the metal ion-containing aqueous solution shown in the "Aqueous Phase" column of Table 1, and the oil phase used in Example 3 is replaced with an oil phase containing the extractant shown in the "Extractant (Solution)" column of Table 2, to which the necessary amount of pH adjusting agent-containing aqueous solution is added to achieve the pH at the time of mixing as shown in the "pH" column of Table 2. The pH of the aqueous phase (25°C) and the metal ion content are measured in the same manner as in Example 1. The confluence conditions and mixing conditions in steps 1 and 2C of Examples 12-14 are shown in the "Confluence Conditions and Mixing Conditions" column of Table 2. The flow time of the mixing section 14 and the time required for phase separation in Examples 12-14 are approximately the same as in Example 3. Furthermore, in each example, as shown in the "Equilibrium Achievement" column of Table 2, the three-liquid mixture flowing out from the downstream mixing section 14b shows that Mn ions in Examples 12 and 13 and copper ions in Example 14 have reached extraction equilibrium, while Ni ions in Examples 12 and 14 and Mg ions in Example 13 have not reached extraction equilibrium.

[0167] <Measurement of Equilibrium Achievement> For each metal ion in Examples 12 to 14, the degree of equilibrium achievement was measured and calculated using the batch extraction method described above. The results, along with the determination of the equilibrium state (in parentheses), are shown in Table 2.

[0168] <Calculation of Kinetic Energy> In Examples 12 to 14, the kinetic energy E of both the aqueous phase and the oil phase was calculated. ＳＴ The results calculated as described above are shown in Table 2.

[0169] <Evaluation: Evaluation of Extraction Amount> For Examples 12 to 14, the extraction rate (unit: %) of each metal ion was calculated in the same manner as in Example 1, and the extraction amount was evaluated. The results are shown in Table 2.

[0170]

[0171] The results in Tables 1 and 2 show the following: In the batch extraction method using a mixer-settler, the three-liquid mixture does not undergo phase separation when the liquid residence time is shortened (Comparative Example 1). On the other hand, in the batch extraction method, although the three-liquid mixture undergoes phase separation when the liquid residence time is lengthened, metal ions other than the target of extraction (Ni ions) also reach extraction equilibrium, making it impossible to selectively extract the target metal ions (Co ions) (Comparative Example 2). Similarly, in the flow extraction method using a flow reactor, lengthening the liquid residence time also causes metal ions other than the target of extraction (Ni ions) to reach extraction equilibrium, making it impossible to selectively extract the target metal ions (Co ions) (Comparative Examples 3 and 4).

[0172] In contrast, in a flow extraction method using a flow reactor, by adjusting the liquid residence time to bring the target metal ions (Co ions) to extraction equilibrium while preventing other metal ions (Ni ions) from reaching extraction equilibrium, and then separating the phase of the three-liquid mixture, it can be seen that the target metal ions (Co ions) can be extracted with high selectivity and quantity in a short time (Examples 1-11). Furthermore, in the flow extraction method, as the liquid residence time is shortened, the amount of extracted target metal ions (Co ions) decreases gradually, but the amount of extracted other metal ions (Ni ions) can be significantly reduced, further increasing the selectivity of the target metal ions (Co ions) (Examples 1-3 and 5). Moreover, by using a phosphate-based compound among acidic extractants as the extractant, the selectivity of the target metal ions (Co ions) can be further increased (Examples 3, 6, 8-11). Furthermore, in the flow extraction method, mixing the aqueous and oil phases at a temperature higher than the initial temperature of the aqueous and oil phases at the start of flow can further increase the amount of target metal ions (Co ions) extracted, and as a result, the selectivity of the target metal ions (Co ions) can be greatly enhanced (Examples 6 and 7).

[0173] Furthermore, as shown in Table 2, in a flow extraction method using a flow reactor, by adjusting the liquid residence time to bring the target metal ions to extraction equilibrium while preventing other metal ions from reaching extraction equilibrium, and then separating the phases of the three-liquid mixture, it can be seen that even when the combination of metal ions is changed, the target metal ions (Mn ions or Cu ions) can be extracted with high selectivity and quantity, and in a short time (Examples 12-14).

[0174] From the above results, it can be understood that, according to the present invention, which separates the phase of the three-liquid mixture while maintaining the above-described mixed state in a flow extraction method, it is not limited to a combination of Co ions and Ni ions, but rather it is possible to extract a specific metal ion (the metal ion to be extracted) from two or more metal ions with high selectivity, preferably with a high extraction amount, and in a short time. The technical significance of the present invention, which achieves such effects, is great.

[0175] Although we have described the present invention along with its embodiments, we do not intend to limit our invention in any detail of the description unless specifically designated, and we believe that it should be interpreted broadly without contradicting the spirit and scope of the invention as set forth in the appended claims.

[0176] This application claims priority based on Japanese Patent Application No. 2024-228730, filed in Japan on 25 December 2024, the contents of which are incorporated herein by reference as part of this specification.

[0177] 1, 2 Extraction device 5 Water phase storage tank 6 Oil phase storage tank 7 pH adjuster-containing aqueous solution storage tank 11 Water phase flow pipe 11a Tapered part (tapered part) 11b Large diameter part 11c Small diameter part 12 Oil phase flow pipe 12a Tapered part (tapered part) 13, 23 Merging part 14, 24 Mixing part 14a Pre-mixing part 14b Post-stage mixing section 15 pH adjuster transfer pipe 16 Separation section 16a Oil phase discharge pipe 16b Water phase discharge pipe

Claims

1. A method for extracting metal ions, comprising combining an aqueous phase containing two or more metal ions and an oil phase containing an extractant during flow, mixing the two phases, and then separating the phases to extract at least one metal ion into the oil phase, wherein the two or more metal ions are separated in a mixed state in which at least one metal ion to be extracted is in extraction equilibrium and the remaining metal ions are in non-extraction equilibrium.

2. The method for extracting metal ions according to claim 1, wherein the mixing of the two phases is performed at 15 to 95°C.

3. The method for extracting metal ions according to claim 1, wherein the liquid residence time from the start of mixing of the two phases to the end of phase separation is 5 minutes or less.

4. The method for extracting metal ions according to claim 1, wherein the aqueous phase and the oil phase are brought together by utilizing collisions between the flowing phases.

5. The method for extracting metal ions according to claim 1, wherein the flow rate of at least one of the aqueous phase and the oil phase is 6.0 to 30 mL / min.

6. The method for extracting metal ions according to claim 1, wherein the two phases are merged with a reduction ratio of the flow diameter of at least one of the aqueous phase and the oil phase of 0.05 to 0.

9.

7. The kinetic energy per unit area and per unit time of at least one of the aqueous phase and the oil phase is 10 to 3.5 × 10 ２ J / sec / m ２ A method for extracting metal ions according to any one of claims 1 to 6, wherein the settings are configured to merge both phases.

8. The method for extracting metal ions according to claim 1, wherein the aqueous phase and the oil phase are circulated in a mixed state over a distance of 10 cm to 2 m.

9. The method for extracting metal ions according to claim 1, wherein the extractant is an acidic extractant.

10. The method for extracting metal ions according to claim 6, wherein the acidic extractant contains a phosphate compound.

11. The method for extracting metal ions according to claim 6, wherein the acidic extractant is represented by the following formula (I). (Formula I), R １ and R ２ represents a substituent, at least one of which is a hydrocarbon group having 9 or more carbon atoms. X represents -OH or -SH. Y represents an oxygen atom or a sulfur atom. Z １ and Z ２ represents a single bond, -O-, -NH-, or -S-.

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