Metal ion extraction method

Abstract

The present invention provides a metal ion extraction method for extracting metal ions into an oil phase by merging an aqueous phase containing metal ions with an oil phase containing an extraction agent in mid-circulation, mixing both phases, and then separating the phases, wherein both phases are mixed at a temperature higher than the temperatures of the aqueous phase and the oil phase at the start of circulation.

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 usually mined as mixtures with 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] Such wet extraction methods typically require the ability to separate residual metal ions by extracting specific metal ions from multiple metal ions into an organic phase using an aqueous phase containing multiple metal ions. As examples of wet extraction methods for separating and extracting metal ions, Patent Document 1 proposes a batch-type wet extraction method in which both phases are mixed at 22 to 40°C using a multi-stage countercurrent mixer-settler to remove calcium from a sulfuric acid solution containing nickel, cobalt, and calcium. Patent Document 2 also proposes a batch-type wet extraction method in which both phases are mixed at 25 to 30°C using a multi-stage countercurrent mixer-settler to remove metal component B from a mixed aqueous metal solution containing metal component A, which includes nickel and / or cobalt, and metal component B, which includes at least one of zinc, chromium, and cadmium.

[0005] Japanese Patent Publication No. 2018-039682 Japanese Patent Publication No. 2016-194105

[0006] In wet extraction methods, it is important to achieve selective extraction of specific metal ions, where a large amount of a particular metal ion is extracted into the organic phase (with a high extraction yield), while the remaining metal ions are extracted in small amounts or their extraction is suppressed. To achieve such selective extraction, it is first necessary to increase the amount of the specific metal ion extracted into the oil phase, that is, to be able to extract the target metal ion into the organic phase with a high extraction yield.

[0007] Furthermore, since wet extraction is usually performed under relatively mild conditions regarding extraction conditions (contact conditions between the aqueous phase and the oil phase), such as temperature and pressure, it is common to perform numerous extraction and separation cycles to mix and separate the two phases in order to reduce recycling costs. However, even if the amount of metal ions extracted when a metal extractant is first used in a wet extraction method (sometimes referred to as the "initial extraction amount" in this invention) is high, the amount of metal ions extracted gradually decreases when the wet extraction method (extraction and separation cycle) is repeated while reusing the metal extractant. Therefore, there is a need for a metal ion extraction method with excellent repeatability that can maintain a high extraction amount (recovery amount) of metal ions even when the wet extraction method is repeated. However, Patent Documents 1 and 2 do not consider increasing the amount extracted into the oil phase or developing a wet extraction method with high repeatability.

[0008] The present invention aims to provide a method for extracting metal ions that enables high extraction rates into the oil phase and also exhibits excellent durability for repeated use.

[0009] In wet extraction methods, while it is possible to increase the extraction amount of metal ions by selecting the extractant and adjusting the pH during mixing, it is currently difficult to achieve a sufficient extraction amount through selection and adjustment alone. Under these circumstances, the inventors conceived the idea that in wet extraction methods, if the oil phase and aqueous phase are mixed in a flow-type manner, where the interface area between the oil phase and aqueous phase is large and the reaction field is small, the mixing state and phase separation properties of the oil phase and aqueous phase can be improved, enabling an increase in the initial extraction amount while suppressing a decrease in the extraction amount even when multiple extraction and separation cycles are performed. Based on this idea, the inventors continued their diligent research and found that in a flow-type wet extraction method (flow-type mixing method), in which the oil phase and aqueous phase are merged and mixed during flow and then phase-separated, mixing the oil phase and aqueous phase at a temperature higher than the temperature at the start of flow, in conjunction with the improvement in the mixing state and phase separation properties mentioned above, not only can the initial extraction amount of specific metal ions into the oil phase be increased, but a high extraction amount can also be maintained over many cycles even when the extraction and separation cycle is repeated. This invention was completed after further consideration based on these findings.

[0010] In other words, the above problems were solved by the following means: <1> A method for extracting metal ions, wherein an aqueous phase containing metal ions and an oil phase containing an extractant are brought together during flow, the two phases are mixed, and then phase separation is performed to extract the metal ions into the oil phase, wherein the two phases are mixed at a temperature higher than the temperatures of the aqueous and oil phases at the start of flow. <2> The method for extracting metal ions according to <1>, wherein the two phases are mixed at a temperature exceeding 60°C. <3> The method for extracting metal ions according to <1> or <2>, wherein the two phases are mixed at a temperature of 95°C or lower. <4> The method for extracting metal ions according to any one of <1> to <3>, wherein the aqueous phase and the oil phase are brought together by utilizing collisions between the respective flowing phases. <5> The method for extracting metal ions according to any one of <1> to <4>, wherein the reduction ratio of each flow diameter when mixing the aqueous phase and the oil phase is 0.1 to 0.9. <6> When mixing the aqueous phase and the oil phase using collisions of the circulating phases, the kinetic energy of the aqueous phase and the oil phase per unit area and per unit time are 1 to 1.0 × 10⁻¹⁰, respectively. ５ J / sec / m ２ A method for extracting metal ions according to any one of <1> to <5>. <7> A method for extracting metal ions according to any one of <1> to <6>, wherein the aqueous phase contains multiple types of metal ions, and at least one of these metal ions is separated and extracted from the other types of metal ions. <8> A method for extracting metal ions according to any one of <1> to <7>, wherein the extractant is an acidic extractant. <9> A method for extracting metal ions according to <8>, wherein the acidic extractant contains a phosphate compound. <10> A method for extracting metal ions according to <8> or <9>, 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-.

[0011] The present invention provides a method for extracting metal ions that can achieve a high extraction rate into the oil phase and also exhibits excellent durability for repeated use. 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.

[0012] 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.

[0013] In the present 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 multiple numerical ranges represented by "~" are set and described, 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 the present invention, a numerical range represented by "~" means a range that includes the numbers described before and after "~" as the lower and upper limits.

[0014] In this invention, the designation of a compound (for example, when referred to as a compound) includes not only the compound itself, but also its salts and ions. It also includes derivatives in which a part has been altered, such as by introducing substituents, to the extent that it does not impair the effects of this invention. In this invention, substituents, linking groups, etc. (hereinafter referred to as substituents, etc.) that are not specified as substituted or unsubstituted mean that the group may have appropriate substituents. Therefore, in this invention, even when simply referred to as a YYY group, this YYY group includes not only the unsubstituted form but also the form with substituents. This is also true for compounds that are not specified as substituted or unsubstituted. Preferred substituents include, for example, groups selected from substituent G described later. In this 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, 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 (for example, each step described below) described below using the aqueous phase and oil phase described below in a flow-type wet extraction method, makes it possible to move (extract) metal ions present in the aqueous phase to the oil phase with a high initial extraction amount, and while maintaining a high extraction amount (also called recovery amount) even after performing the extraction separation cycle many times. In the present invention and this specification, when simply referred to as "extraction amount," it includes the amount of metal ions extracted when the extractant is first used in the extraction separation cycle and the amount extracted when the extraction separation cycle is performed many times. When the former and the latter are clearly distinguished, the former is referred to as "initial extraction amount." 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 Apparatus 1> As shown in Figure 1, the extraction apparatus 1 includes an aqueous phase storage tank 5 for containing and storing the aqueous phase, an aqueous phase flow pipe 11 connected to the aqueous phase storage tank 5 and for the aqueous phase to flow to a confluence 13 located downstream of the aqueous phase in the flow direction from the aqueous 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. The extraction apparatus 1, which is an example of an extraction apparatus suitable for the present invention, is suitable as an extraction apparatus for suitably implementing an extraction method in which, among the extraction methods of the present invention described later, the steps are taken in the following order: first, the step of combining the aqueous phase and the oil phase and continuing to flow them; then, the step of combining the combined two-liquid solution and the pH adjusting agent-containing aqueous solution and further flowing them; and after the extraction of the metal ions to be extracted reaches extraction equilibrium, the step of separating the combined three-liquid solution. 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 an appropriate level depending on 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 has a heating device (not shown in Figure 1) that heats the three-liquid confluence in at least the downstream mixing section 14b. The extraction apparatus 1 may further have a heating device (not shown in Figure 1) that heats the aqueous phase, oil phase, pH adjusting agent-containing aqueous solution, and confluence in at least one of the following: aqueous phase flow pipe 11 (especially the downstream portion such as the tip section 11a), oil phase flow pipe 12 (especially the downstream portion such as the tip section 12a), confluence section 13, upstream mixing section 14a, and pH adjusting agent transfer pipe 15 (especially the downstream portion such as the tip section). The heating device can be any device that can heat 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 optionally 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 including 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. 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. The extraction device 2 may also have a heating device 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. 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 may contain one type of metal ion, but it is preferable that it contains at least two types. The number of types of metal ions contained in the aqueous phase is not particularly limited as long as it is one 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 contained 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 that it contains 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 preferably at least one transition metal element ion (a metal element 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.

[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 substances from metal wastes, other wastes, such as metal recovered substances from waste batteries (LiB), etc., and further mixtures thereof can be used. Examples of the metal recovered substances from waste LiB include recovered substances by known methods such as wet treatment and electrolysis.

[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 to 1.0×10 ６ mass ppm, and 1.0×10 ３~1.0 x 10 ５ Preferably, the mass is ppm, and 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. The temperature of the aqueous phase (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. 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 level is preferable because it allows for an increase in the initial extraction amount of metal ions, and also allows for maintaining a high extraction amount even after numerous extraction and separation cycles.

[0046] 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.

[0047] 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.

[0048] <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.

[0049] 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 in order to achieve a high initial extraction amount and to maintain a high extraction amount even after performing many extraction and separation cycles. It is more preferable to use an acidic extractant selected from phosphoric acid compounds, and even more preferable to use a compound represented by (Formula I) (acidic extractant) described later. Extractants suitably used in the present invention will be described later.

[0050] 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.

[0051] 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. ＳＴSetting this value to a suitable level is preferable because it allows for an increase in the initial extraction amount of metal ions, and also allows for maintaining a high extraction amount even after numerous extraction and separation cycles.

[0052] 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.

[0053] <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.

[0054] [Extraction Method of the Present Invention] The extraction method of the present invention involves combining an aqueous phase containing metal ions and an oil phase containing an extractant during the flow process, mixing the two phases at a temperature higher than the temperatures of the aqueous and oil phases at the start of the flow process, and then separating the phases. That is, in the present invention, the temperature (referred to as the "mixing temperature" in the present invention) is adjusted to the above temperature relationship at least when the two phases are being mixed or during mixing (regardless of when they are being combined). The extraction method of the present invention, which adjusts the temperature at least at the time of mixing (after the three-liquid mixture has been adjusted to a predetermined pH) to a temperature higher than the temperatures of the aqueous and oil phases at the start of the flow process, allows for the movement (extraction) of specific metal ions coordinated by the extractant from the aqueous phase to the oil phase with a high initial extraction amount, and while maintaining a high extraction amount even after performing numerous extraction and separation cycles. The mixing state for phase separation in the extraction method of the present invention is not particularly limited, but is usually a mixing state in which (all) the metal ions contained in the aqueous phase are in extraction equilibrium. 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 a pH suitable for the metal ions to be extracted. In the present invention, the "state with a suitable pH" is defined as the point at which mixing of a predetermined amount of pH adjusting agent-containing aqueous solution into both phases is completed, or the point at which mixing of the pH-adjusted aqueous phase or pH-adjusted oil phase, as described later, is completed.

[0055] 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 this invention, the mixing temperature refers to the final temperature reached during the mixing process. The mixing temperature should be higher than the temperature at the start of flow and can be appropriately determined considering the initial extraction amount and repeated durability, with higher temperatures generally resulting in higher initial extraction amounts and repeated durability. In this invention, even if the mixing temperature and the confluence temperature described later are increased, since it is a flow-type extraction method, 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. 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, in terms of excellent initial extraction amount and repeated durability. 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 between the aqueous phase and the oil phase, more preferably 93°C or lower, and even more preferably 91°C or lower in that it is excellent in terms of initial extraction amount and repeated durability.

[0056] The temperature difference between the temperatures of both phases at the start of distribution and the mixing temperature is not particularly limited, but it is preferably greater than 0°C and less than or equal to 90°C, more preferably between 10°C and 80°C, and even more preferably between 20°C and 70°C, as this allows for a higher initial extraction amount and exhibits high repeatability.

[0057] 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.

[0058] In the extraction method of the present invention, the temperature at the time of or during the merging of the two phases (hereinafter referred to as the "merging temperature") is not particularly limited and may be the same temperature as or lower than the temperatures of the aqueous and oil phases at the start of flow. It is preferable that the merging temperature is 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 initial extraction amount and maintain a high extraction amount even when the extraction and separation cycle is performed many times. In the present invention, the merging temperature means the final temperature reached during the flow process. The merging 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 merging temperature may be the same temperature as or different from the mixing temperature, and depending on the flow velocity, flow rate, etc. of both phases, the mixing temperature may be higher than the merging temperature. Also, in the present invention, the temperature difference between the temperatures of both phases at the start of flow and the merging temperature is not particularly limited and is preferably within the same range as the temperature difference between the temperatures of both phases at the start of flow and the mixing temperature described above. Furthermore, 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.

[0059] In this invention, the temperatures of the aqueous phase and the oil phase at the start of flow may be the same or different.

[0060] 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 flow, in conjunction with setting the mixing temperature to be at least higher than the temperatures of the aqueous and oil phases at the start of flow, as described above, in order to further increase the initial extraction amount and achieve high repeatability. 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 order to improve the mixing state. Various conditions in the extraction method of the present invention will be described later in the section on preferred extraction methods of the present invention.

[0061] As described above, the extraction method of the present invention can move (extract) specific metal ions from the aqueous phase to the oil phase with a high initial extraction yield, and maintain a high extraction yield even after performing numerous extraction and separation cycles. In the extraction method of the present invention, the metal ion extracted into the oil phase is the single metal ion contained in the aqueous phase. On the other hand, if the aqueous phase contains multiple types of metal ions, the metal ion extracted into the oil phase is ideally one specific metal ion, but including those with low extraction rates, it may be two or more types of metal ions, or even all of them. In other words, the extraction method of the present invention can separate and extract at least one of the metal ions from the other (residual) metal ions when the aqueous phase contains multiple types of metal ions. However, the metal ion extracted into the oil phase with a high extraction yield (also referred to in the present invention as the "metal ion for extraction or target of extraction") is at least one of the multiple types of 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, cobalt ions, and nickel ions, which are heterogroup metal ions of the same period, can be extracted into the oil phase in high extraction amounts.

[0062] The extraction method of the present invention allows for the extraction of two or more metal ions from multiple types of metal ions (groups) present in the aqueous phase, including those with low extraction rates, into the oil phase. In this case, one of the metal ions can be extracted with a high extraction yield, preferably with high extraction resolution (selectivity), and is particularly applicable to new applications such as the separation and recovery of two or more metal ions, especially heterogroup metal ions. Heterogroup metal ions of the same period usually have similar physical and chemical behaviors, making it difficult to separate and recover either one with a high recovery yield and high extraction resolution. However, the extraction method of the present invention allows for the extraction of both heterogroup metal ions of the same period that have 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. In this case, one of the metal ions can be recovered with a high extraction yield and preferably with high extraction resolution. Similarly, for metal ions belonging to Group 7 (especially manganese ions) and 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), it is possible to extract both while recovering one of the metal ions with a high extraction yield, preferably with a high extraction resolution. Therefore, the present invention can greatly contribute to the further spread of electric vehicles and, ultimately, to the construction of a sustainable society.

[0063] 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 initial extraction amount (the above ratio) CA is preferably 80% or more, and under the conditions of the examples described later, it is preferably 85% or more, and more preferably 90% 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.

[0064] In the present invention, maintaining a high extraction amount even after performing the extraction and separation cycle (for example, a series of cycles of steps 1 to 3 described later) many times means that the extraction amount CB in the subsequent cycles is maintained without significantly reducing the initial extraction amount CA. Specifically, although it is not unique and depends on the content of metal ions present in the aqueous phase, the content of the extractant in the oil phase, etc., for example, it means that the difference between the initial extraction amount CA and the extraction amount CB after performing the extraction and separation cycle many times [CA - CB] is small, and the metal ions can be extracted into the oil phase. Here, the extraction amount CB in the subsequent cycles is the ratio of the difference between the content CI of the metal ions in the aqueous phase (before extraction) and the content (residual amount) CR of the metal ions in the aqueous phase (after extraction) in the subsequent cycles [(CI - CR) / CI] × 100 (%). In the present invention, the above difference [CA-CB] serves as an evaluation index for repeated durability, and is preferably less than 8%, more preferably less than 6% and even more preferably less than 4% under the conditions of the examples described later. Ideally, the lower limit should be 0%, but in practice it can be, for example, 0.5%.

[0065] Furthermore, 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, the content of the extractant in the oil phase, etc., but it means that a specific metal ion can be selectively extracted from among the metal ions present in the aqueous phase. Also, 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 of the specific metal ion to be extracted (usually one) can be separated from the other metal ions at a ratio of 2.0 or more [(amount of specific metal ion extracted) / (total amount of other metal ions extracted)] under the conditions of the examples described later. The above ratio (selectivity ratio) is preferably 4.0 or more, more preferably 5.0 or more, and even more preferably 6.0 or more. There is no particular upper limit, but for example, 1.0 × 10 ４ This can be done. In this invention, "room temperature" refers to the temperature in a normal environment, and specifically, it is a temperature range of 20 to 30°C.

[0066] [Preferred Extraction Method of the Present Invention] The extraction method of the present invention is a method in which an aqueous phase containing metal ions and an oil phase containing an extractant are combined during flow, the two phases are mixed at a temperature higher than the temperature of at least one of the aqueous and oil phases at the start of flow, and then the phases are separated. Preferably, it is a flow-type wet extraction method (sometimes referred to as "the preferred extraction method of the present invention") having at least the following steps 1 to 3. 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 adjusting agent are used as appropriate. Step 1: A step of combining the flowing aqueous phase and oil phase and continuing to flow Step 2: A step of mixing the aqueous phase, oil phase and the aqueous solution containing a pH adjusting agent at a temperature higher than the temperature of the aqueous phase and oil phase at the start of flow and continuing to flow Step 3: A step of separating the three-liquid mixture after the extraction of the metal ions to be extracted has reached extraction equilibrium.

[0067] 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.

[0068] <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.

[0069] 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.

[0070] 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 that it can further improve the initial extraction amount and repeated durability. 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 the initial extraction amount of metal ions and repeated durability. 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.

[0071] In step 1, etc., the temperature at the time of confluence of the aqueous and oil phases (before pH adjustment) is not particularly limited and is as described above. The confluence temperature can be lower than the temperatures of the aqueous and oil phases at the start of flow, but is usually the same, preferably the mixing temperature described later. Setting the confluence temperature within the same range as the mixing temperature described later can further improve the initial extraction amount and repeated durability. When using a pH-adjusted aqueous or oil phase, the confluence temperature is set within the same range as the mixing temperature described later.

[0072] 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 It is preferable to set the flow rate to L / min, more preferably to 4.0 to 13.0 mL / min, and even more preferably to 5.0 to 13.0 mL / min, in order to achieve a high level of both initial extraction amount of metal ions, repeatability, and extraction resolution. Similarly, the internal pressure (flow pressure) of the aqueous phase cannot be uniquely determined, but for example it can be set to 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 ２ The flow rate is preferably mL / min, more preferably 4.0 to 13.0 mL / min, and even more preferably 5.0 to 13.0 mL / min, in that it allows for a high level of both initial metal ion extraction and repeated durability. 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 is preferably 0.03 to 2.5 MPa in that it improves the mixing state.

[0073] 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.

[0074] 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 that it improves the mixing state, specifically, in that it maintains a high level of both the initial extraction amount of metal ions and the durability of repeated extractions while maintaining the rapid phase separation (also called phase separation or liquid separation) of both phases after mixing. The lower limit of the reduction ratio is not particularly limited, and it can be 0.1 or more in that it suppresses excessive internal pressure load and is also excellent in terms of workability, and it is preferably 0.2 or more, and more preferably 0.3 or more, in that it improves 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 phase and the oil phase, and can be, for example, 1 to 100 mm.

[0075] 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 the initial extraction amount of metal ions and the durability of repeated extractions. 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 (E ＳＴ 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 )

[0076] 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).

[0077] 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 the initial extraction amount of metal ions and the durability of repeated extractions. In the present invention, the kinetic energy E 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 EＳＴ As for, in terms of increasing the interfacial area between the aqueous phase and the oil phase and further enhancing the initial extraction amount of metal ions and the repetitive durability, it is preferably 1 J / sec / m ２ or more, and more preferably 2 J / sec / m ２ or more. In one aspect of the present invention, the kinetic energy E ＳＴ is preferably 2.0×10 ２ J / sec / m ２ or more, and particularly preferably 5.0×10 ２ J / sec / m ２ or more. On the other hand, as for the above kinetic energy E ＳＴ , in terms of enhancing the phase separation property, it can be 1.0×10 ５ J / sec / m ２ or less, and in terms of further enhancing the initial extraction amount of metal ions and the repetitive durability while maintaining a high phase separation property, it is preferably 1.6×10 ４ J / sec / m ２ or less, more preferably 1.0×10 ４ J / sec / m ２ or less, still more preferably 5.0×10 ３ J / sec / m ２ or less, even more preferably 1.0×10 ２ J / sec / m ２ or less, particularly preferably 10 J / sec / m ２ or less, and most preferably 10 J / sec / m ＳＴ or less. One of the preferred embodiments of the kinetic energy E ２ is preferably 1.0 to 1.5×10 ２ J / sec / m ２ regardless of the above upper and lower limits, more preferably 2.0 to 1.0×10 ２ J / sec / m ２ even more preferably 3.0 to 80 J / sec / m ２ and particularly preferably 3.0 to 10 J / sec / m

[0078] In the present invention, the conditions for carrying out step 1 etc. can be appropriately selected from the above conditions, and the conditions can be appropriately combined and set. In the present invention, the conditions for carrying out step 1 etc. can further improve the initial extraction amount of metal ions and the durability of repeated extraction, and among the above conditions, the flow rate, the reduction ratio of the flow diameter (ratio of inner diameters), and the kinetic energy E can be appropriately selected. ＳＴ It is preferable to set at least one of the following, and in order to achieve a high level of both the initial extraction amount of metal ions and the durability of repeated extractions, it is more preferable to set the flow rate and the reduction ratio of the flow diameter to any of the above ranges by combining them, and in order to achieve an even higher level of both the initial extraction amount of metal ions and the durability of repeated extractions, the flow rate and 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 3.0 to 15.0 mL / min, the reduction ratio of the flow diameter is set within the range of 0.2 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].

[0079] 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.).

[0080] 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 collisions between 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 confluenced and mixed in the confluence section 13, preferably by colliding the two phases to confluence and mix them, and then transferred to the mixing section 14, where they continue to flow through the internal passages of the mixing section 14.

[0081] <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 the mixing of the aqueous phase and the oil phase. Step 2: A step in which the aqueous phase, the oil phase and the pH adjusting agent-containing aqueous solution are combined and further passed through.

[0082] (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 is 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 the initial extraction amount and repeated durability, 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.

[0083] As described above, in step 2 of further circulation, the two-liquid mixture of the aqueous phase and oil phase that were combined in step 1 of the subsequent circulation process (also called the oil-water mixture) is combined with the pH adjusting agent-containing aqueous solution and further circulated. Specifically, in the extraction method of the present invention, when the extraction apparatus 1 is used, the pH adjusting agent-containing aqueous solution circulating in the pH adjusting agent transfer pipe 15 is transferred to the mixing section 14, where the oil phase and aqueous phase (two-liquid mixture) circulating in 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 circulated in the downstream mixing section 14b and transferred to the separation section 16.

[0084] In the present invention, when using the extraction apparatus 1, the aqueous phase, oil phase, and pH adjusting agent-containing aqueous solution (three-phase combined liquid) are 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 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 (combination temperature) from the time of confluence of the aqueous and oil phases until immediately before mixing with the pH adjusting agent-containing aqueous solution may be lower than or the same as the temperature of the aqueous and oil phases at the start of flow, but it is preferable that the temperature be higher than the temperature of at least one of the aqueous and oil phases at the start of flow, as this improves the mixing state and further enhances the initial extraction amount and repeated durability.

[0085] (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).

[0086] In step 2B, 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. By combining and mixing 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, the initial extraction amount and repeated durability can be further increased, and the length of the mixing section 24 (mixing time) can be shortened.

[0087] 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.

[0088] (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).

[0089] In step 2C, the aqueous phase and the oil phase (pH-adjusted two-liquid mixture) are combined and mixed at a temperature higher than the temperature of at least one of the aqueous and oil phases 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. By combining and mixing 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, the initial extraction amount and repeated durability can be further increased, and the length (mixing time) of the mixing section 14 or 24 can be shortened.

[0090] In the present invention, the three-liquid mixture is separated into an aqueous phase and an oil phase in step 3, which will be described later. However, the point at which extraction equilibrium is reached does not have to be before the phase separation, and it may also be after it has been transferred to the separation section 16 of the extraction apparatus 1 and 2. In order to achieve an even higher level of both initial extraction volume and repeated durability, it is preferable that the extraction of the metal ions to be extracted from the three-liquid mixture reaches extraction equilibrium during the flow in step 1 or step 2 (until it is introduced into the standing section 16). Specifically, it is preferable that the extraction of the metal ions to be extracted reaches extraction equilibrium while the three-liquid mixture is flowing through the downstream mixing section 14b or mixing section 24 of the mixing section 14. In the present invention, the aqueous phase and the oil phase are 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. Subsequently, since both phases are mixed in the same temperature range during flow (after pH adjustment), it is considered that the extraction of metal ions is promoted while flowing through the mixing section 14 or 24, and extraction equilibrium is reached quickly. In the present invention, the fact that the extraction of the target metal ions has reached extraction equilibrium can be confirmed and identified by various methods. For example, it can be confirmed and identified by measuring that the pH of the three-liquid confluence liquid is constant after pH adjustment with a pH adjusting agent (flowing through the downstream mixing section 14b or mixing section 24), or by measuring that the content (residual amount) of the target metal ions in the aqueous phase sampled from the three-liquid confluence liquid is constant. In the present invention, in order to reach extraction equilibrium for the extraction of the target metal ions while the three-liquid confluence liquid is flowing through the downstream mixing section 14b or mixing section 24, the above confirmation and identification methods should be performed on the three-liquid confluence liquid in advance, and the flow time (flow path length), as well as the flow rate, inner diameter, etc. of the downstream mixing section 14b or mixing section 24 should be determined based on the results obtained. The time required to reach extraction equilibrium for the target metal ions cannot be uniquely determined, as it depends on the content of metal ions in the aqueous phase, the type of extractant, the temperature, etc. However, it can be measured as the elapsed time from mixing the aqueous phase and the oil phase (after pH adjustment), ranging from 1 minute to 24 hours, and preferably from 1 to 60 minutes.

[0091] 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.

[0092] <Step 3> In the extraction method of the present invention, the following Step 3 is then performed. Step 3: After the extraction of the metal ions to be extracted has reached extraction equilibrium, the three-liquid mixture is separated into an aqueous phase and an oil phase (phase separation).

[0093] 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 the conditions under which the three-liquid mixture separate into an aqueous phase and an oil phase. In the standing method, the standing time is usually 10 minutes to 24 hours after being transferred to the separation unit 16. 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, preferably 10 to 60 minutes. 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 the temperature is 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 the temperature is approximately the same as the temperature of the three-liquid mixture (mixing temperature) (mixing temperature ± 5°C).

[0094] 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.

[0095] In the extraction method of the present invention, by performing steps 1 to 3 described above, metal ions present in the aqueous phase to which the extractant has coordinated can be extracted into the oil phase. If the aqueous phase contains two or more types of metal ions, at least one type of metal ion present in the aqueous phase to which the extractant has coordinated can be extracted into the oil phase. Ideally, the number of types of metal ions extracted into the oil phase is one, but it may be two or more. 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 types of metal ions extracted into the oil phase from among multiple types of 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.

[0096] 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.

[0097] <Multi-cycle extraction method> As described above, the extraction method of the present invention can maintain high repeatability even when the series of extraction and separation cycles of steps 1 to 3 is performed many times, so the series of extraction and separation cycles of steps 1 to 3 can be performed many times. The extraction method of the present invention, which performs a series of extraction and separation cycles many times (sometimes called the multi-cycle extraction method of the present invention), can perform the extraction and separation cycle including steps 1 to 3 as long as repeatability 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 of 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.

[0098] 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.

[0099] <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.

[0100] The extraction method of the present invention, despite being a simple flow-type mixing method as described above, can extract metal ions from the aqueous phase into the oil phase with a high extraction amount in a single extraction and separation cycle, and maintains a high extraction amount even when the extraction and separation cycle is repeated many times. In particular, when the aqueous phase contains multiple types of metal ions, a specific metal ion can be extracted into the oil phase with a high extraction amount in a single extraction operation, and maintains a high extraction amount even when the extraction operation is repeated many times. Therefore, the extraction method of the present invention can also be described as a method for separating and recovering a specific metal ion from metal ions present in the aqueous phase.

[0101] 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 a high initial extraction yield and high repeatability. 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 a high initial extraction yield and high repeatability. 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 a high initial extraction yield and high repeatability. 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 a high initial extraction yield and high repeatability. Furthermore, when extracting metal ions belonging to Group 9 and Group 11 into the oil phase, the metal ions belonging to Group 11 can be separated and recovered with a high initial extraction yield and high repeatability. Moreover, 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, and the metal ions belonging to Group 12 can be separated and recovered with a high initial extraction yield and high repeatability.

[0102] As described above, the extraction method of the present invention can extract and recover specific metal ions from among the metal ions present in the aqueous phase into the oil phase with a high initial extraction yield and high repeatability. In particular, the extraction method of the present invention can extract two or more metal ions present in the aqueous phase and recover one of them with a high initial extraction yield and high repeatability. 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).

[0103] <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 high initial extraction yield and high repeat durability, 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.

[0104] 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.

[0105] The acidic extractant used in the extraction method of the present invention is preferably a compound represented by the following formula (I), as it can achieve a high level of both initial extraction yield and repeated durability. The compound represented by the following formula (I) includes compounds having a phosphate group, a phosphonic acid group, a phosphinic acid group, and further, 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 replacing the oxygen atom (-O-) bonded to P with a nitrogen atom. The acidic extractant represented by (Formula I) is preferably a phosphate compound, 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, in order to achieve an even higher level of both initial extraction yield and repeated durability.

[0106] In (Equation I), R １ and R ２ Each 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 ２Substituents 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.

[0107] 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 ２ It is preferable that all possible substituents are hydrocarbon groups, as this allows for a better balance between initial extraction yield and repeated durability at an even higher level. The heteroatom-containing substituent preferably contains an oxygen atom or a sulfur atom as the heteroatom, and preferably 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.

[0108] R １ and R ２The 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, heterocyclic groups, etc. are preferred, and alkyl groups are even more preferred in that they can achieve a good balance between the initial extract yield and repeated durability at an even higher level.

[0109] The alkyl, alkenyl, and alkynyl groups that can be taken as individual substituents may be linear, branched, or cyclic, but branched chains are more preferred because they allow for a better balance between initial extraction yield and repeated durability. The aryl and heterocyclic groups that can be taken as individual substituents are the same as the corresponding groups in substituent G described later.

[0110] R １ and R ２ The 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.

[0111] As for the compound substituent, those containing a ring structure are preferred in terms of initial extract yield and repeated durability. 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 initial extract yield and repeated durability. 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.

[0112] R １ and R ２ As 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 initial extraction yield and repeated durability. 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.

[0113] 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 ２The 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 order to achieve an even higher level of both initial extraction yield and repeated durability. More preferably, combinations of substituents having branched structures, and combinations of substituents having branched structures and substituents having a ring structure (particularly complex substituents) are preferred. 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, etc. Single substituents such as alkyl groups, or complex substituents such as groups combining alkoxy groups or alkylthio groups with aryl groups are preferred, and groups combining alkyl groups or alkoxy groups with aryl groups are more preferred. In the present invention, the substituent having a branched structure may be any substituent with 3 or more carbon atoms, but it is preferable that the substituent has 9 or more carbon atoms in order to achieve an even higher level of both initial extraction yield and repeated durability.

[0114] Furthermore, there are no particular restrictions on the type of substituent, R １ and R ２ In terms of initial extraction yield and repeated durability, 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.

[0115] 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.

[0116] 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.

[0117] R １ Possible substituents and R ２ Among the possible substituent combinations, combinations of alkyl groups are particularly preferred because they allow for an even higher level of both initial extraction yield and repeated durability.

[0118] 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 ２ At 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, then both the initial extract yield and the durability of repeated extractions can be achieved at an even higher level. In the present invention, in terms of the initial extract yield and the durability of repeated extractions, 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 ２Preferably, 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 order to achieve a good balance between the initial extraction amount and repeated durability at an even higher level. 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.

[0119] 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.

[0120] 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 substituents, in terms of the initial extraction amount and repeated durability, R １ and R ２ Preferably, at least one of them is a hydrocarbon group having three or more branched carbon atoms.

[0121] 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.

[0122] 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, R can achieve an even higher level of both initial extraction yield and repeated durability. 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 preferable in that it can achieve an even higher level of both initial extraction yield and repeated durability. 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.

[0123] In this embodiment, R １ Possible substituents and R ２The 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).

[0124] 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 initial extraction volume and repeated durability, Z １ and Z ２ It is more preferable that one of the bonds is a single bond and the other is -O-.

[0125] 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 ones of each symbol. 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 R１ or R ２ This is how it is interpreted. In the present invention, R １ and R ２ and Z １ and Z ２ As 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.

[0126] 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.

[0127] 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.

[0128] 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.

[0129]

[0130] - 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.

[0131] 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.

[0132] [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.).

[0133]

[0134] <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.

[0135] 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.

[0136] 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.

[0137] <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.

[0138] <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.

[0139] [Preparation of Metal Ion-Containing Aqueous Solutions] <Preparation of Co Ion-Containing Aqueous Solution> Add 57.2 g of cobalt(II) sulfate heptahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) to a 1 L volumetric flask, make up with ultrapure water, dissolve by stirring at 40°C, and then cool to room temperature (25°C) to prepare a Co ion-containing aqueous solution. The density of this aqueous solution measured by the above method is 1.03 × 10⁻⁶. ３ kg / m ３ The above describes the preparation of a Mn ion-containing aqueous solution. The Mn ion-containing aqueous solution is prepared in the same manner as the Co ion-containing aqueous solution, except that 52.6 g of manganese(II) sulfate pentahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is used instead of 57.2 g of cobalt sulfate heptahydrate. The density of this aqueous solution, measured by the above method, is 1.03 × 10⁻⁶. ３ kg / m ３ The Ni ion-containing aqueous solution is prepared in the same manner as the Co ion-containing aqueous solution, except that 53.7 g of nickel(II) sulfate hexahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is used instead of 57.2 g of cobalt sulfate heptahydrate in the preparation of the Co ion-containing aqueous solution. The density of this aqueous solution measured by the above method is 1.03 × 10⁻⁶. ３ kg / m ３ The above is correct. <Preparation of Mg ion-containing aqueous solution> The Mg ion-containing aqueous solution is prepared in the same manner as the Co ion-containing aqueous solution, except that 121.5 g of magnesium(II) sulfate heptahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is used instead of 57.2 g of cobalt sulfate heptahydrate in the preparation of the Co ion-containing aqueous solution. The density of this aqueous solution measured by the above method is 1.05 × 10⁻⁶. ３ kg / m ３ The Cu ion-containing aqueous solution is prepared in the same manner as the Co ion-containing aqueous solution, except that 47.1 g of copper(II) sulfate pentahydrate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) is used instead of 57.2 g of cobalt sulfate heptahydrate in the preparation of the Co ion-containing aqueous solution. The density of this aqueous solution measured by the above method is 1.03 × 10⁻⁶. ３ kg / m ３The following is the preparation of the Co and Ni ion-containing aqueous solution: 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.) are added to a 1 L volumetric flask. After making up the volume with ultrapure water, the solution is stirred and dissolved at 40°C, and then cooled to room temperature to prepare the Co and Ni ion-containing aqueous solution. The density of this aqueous solution measured by the above method is 1.06 × 10⁻⁶. ３ kg / m ３ That is the case.

[0140] The content (concentration CI) of each metal ion in the ion-containing aqueous solutions prepared as described above is 1.2 × 10⁻⁶. ４ It is ppm.

[0141] <Preparation of Extractant Solution (Oil Phase)> Add each synthesized or prepared extractant and a pH adjusting agent-containing aqueous solution (4M sodium hydroxide aqueous solution or 4M hydrochloric acid) in an amount less than the amount required to achieve the pH at the time of mixing shown in 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.

[0142] 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 1 mm. The length and inner diameter (equivalent diameter) of the opening end of the tip section 11a and tip section 12a are 1 mm and 0.8 mm, respectively. Therefore, the ratio of the inner diameter of the opening end of the tip section to the inner diameter of each flow pipe (reduction ratio of flow diameter) is 0.8. In addition, each flow pipe is prepared in which only the inner diameter (equivalent diameter) of the opening end of the tip section 11a and tip section 12a is changed to 0.5 mm (reduction ratio of flow diameter: 0.5). The confluence section 13 is a cylindrical pipe body with the same diameter as the inner diameter of the opening end 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 2 mm. The mixing section 14 has a pre-mixing section 14a and a post-mixing section 14b, which consist of a wide-ended section and a tubular section with a constant inner diameter. The connection diameter (equivalent diameter) of the wide-ended section to the confluence section 13 is 0.5 mm, the length of the tubular section is 100 mm, and the inner diameter (equivalent diameter) of the tubular section is 1 mm. The length of the post-mixing section 14b is 100 mm, and the inner diameter (equivalent diameter) of the tubular section is 1 mm. The total length of the pre-mixing section 14a and the post-mixing section 14b is set after confirming and identifying the time (length) required for extraction equilibrium for the three-liquid combined solution. The length of the pH adjusting agent transfer tube 15 is 50 mm, and its inner diameter is 1 mm. The separation section 16 uses a vial tube with an inner diameter of 36 mm.

[0143] [Example 1] <Implementation of one-cycle extraction method> In Example 1, an extraction apparatus 1 equipped with a confluence section 13 having the inner diameter and cross-sectional area shown in the "Confluence Section" column of Table 1 is used to extract Co ions under the conditions shown in Table 1. Specifically, a Co ion-containing aqueous solution (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 6.0 mL / min (internal pressure of 0.06 MPa), and the Co ion-containing aqueous solution and the oil phase are combined in the confluence section 13, and the combined liquid is then continuously flowed through the mixing section 14 (pre-mixing section 14a) (Step 1). The temperature in the confluence section 13 and the pre-mixing section 14a is 25°C (the confluence section 13 and the pre-mixing section 14a are not heated). Furthermore, the confluence conditions in step 1 are shown in the "Confluence and Mixing Conditions" column of Table 1 (the same applies to Examples 2 to 12 and Comparative Example 2, and to the <Implementation of 10-cycle extraction method> in each example and comparative example). One minute after the start of liquid transfer of both phases, the pH adjusting agent-containing aqueous solution (4M sodium hydroxide aqueous solution or 4M hydrochloric acid) stored in the pH adjusting agent-containing aqueous solution storage tank 7 is transferred from the pH adjusting agent transfer pipe 15 to form a three-liquid confluence. This three-liquid confluence is heated by a heater installed on the outer circumference of the downstream mixing section 14b and further circulated within the downstream mixing section 14b at the temperature shown in the "Mixing Section" column of the "Temperature" column in Table 1 (step 2). The amount of pH adjusting agent-containing aqueous solution transferred is adjusted so that the pH of the aqueous phase, which is recovered and separated from the three-liquid confluence in the downstream mixing section 14b and cooled to 25°C, is the value shown in the "pH" column of Table 1. The flow rate of the combined liquid circulating within the confluence section 14 was 12.5 mL / min. The three-liquid combined liquid flowing out from the downstream mixing section 14b had already reached extraction equilibrium, which could be confirmed by collecting the three-liquid combined liquid into vials every minute and observing that the pH of the aqueous phases had become constant. The three-liquid combined liquid was then transferred and collected into vials serving as the separation section 16. After that, the three-liquid combined liquid was allowed to stand to confirm that the organic phase (oil phase) and the aqueous phase had separated into two phases. The aqueous phase was then separated (step 3) to extract Co ions. After cooling the extracted aqueous phase to 25°C, the pH and Co ion content of this aqueous phase were measured.The Co ion content (residual amount) 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).

[0144] <Implementation of 10 Extraction Cycles> Except for using the oil phase containing the extractant PC-88A that was phase-separated from the aqueous phase in the separation unit 16 in the <Implementation of 1 Extraction Cycle> above as the oil phase for the next cycle, the extraction separation cycle is performed 10 times consecutively in the same manner as in the <Implementation of 1 Extraction Cycle> above. That is, the oil phase containing the prepared extractant PC-88A is used in the extraction separation cycle for 10 consecutive cycles. In each extraction separation cycle, it can be confirmed that the three-liquid mixture flowing out from the downstream mixing unit 14b has already reached extraction equilibrium. The oil phases recovered by phase separation in the separation unit 16 are used after back-extracting metal ions as follows. That is, 10 mL of purified water is added to 10 mL of each recovered oil phase, 10 M hydrochloric acid is added to adjust the pH of the mixture to 1.0, and after stirring at room temperature for 30 minutes, it is left to stand at the same temperature for 1 hour. After confirming that the mixture has separated into two layers, an organic phase (oil phase) and an aqueous phase, the oil phase is recovered by liquid-liquid extraction. The pH and Co ion content (residual amount) of the aqueous phase (25°C) obtained by performing 10 consecutive extraction and separation cycles are measured in the same manner as in the <Implementation of the extraction method for one cycle> described above.

[0145] [Examples 2-4, 7 and Comparative Example 2] <Implementation of one cycle of extraction method> Except for changing the final temperature reached in the downstream mixing section 14b, the temperature of the aqueous phase stored in the aqueous phase storage tank 5 (corresponding to the aqueous phase at the start of flow) and the temperature of the oil phase stored in the oil phase storage tank 6 (corresponding to the oil phase at the start of flow) as shown in the "Temperature" column of Table 1, the <Implementation of one cycle of extraction method> for Examples 2-4 and Comparative Example 2 is carried out in the same manner as the <Implementation of one cycle of extraction method> for Example 1, and the pH of the aqueous phase and the Co ion content are measured in the same manner as in Example 1. It can be confirmed that in the extraction separation cycle in each example and comparative example, the three-liquid combined liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0146] <Implementation of 10-Cycle Extraction Method> In the <Implementation of 10-Cycle Extraction Method> of Example 1, the <Implementation of 10-Cycle Extraction Method> is carried out in the same manner as in Example 1, except that the final temperature reached in the downstream mixing section 14b, the temperature of the aqueous phase stored in the aqueous phase storage tank 5 (corresponding to the aqueous phase at the start of flow) and the temperature of the oil phase stored in the oil phase storage tank 6 (corresponding to the oil phase at the start of flow) are changed to the temperatures shown in the "Temperature" column of Table 1. The <Implementation of 10-Cycle Extraction Method> of Examples 2 to 4 and Comparative Example 2 are carried out in the same manner as in Example 1, and the pH and Co ion content of the aqueous phase (25°C) obtained by performing 10 consecutive extraction and separation cycles are measured in the same manner as in Example 1. It can be confirmed that in each extraction and separation cycle in each example, the three-liquid combined liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0147] [Example 5] In Example 5, Co ions are extracted using the extraction apparatus 1A equipped with a confluence section 13 having the inner diameter and cross-sectional area shown in the "Confluence Section" column of Table 1. In this extraction apparatus 1, both opening ends of the tip section 11a of the aqueous phase flow pipe 11 and the tip section 12a of the oil phase flow pipe 12 have the same inner diameter as the confluence section 13. The inner diameter of the mixing section 14 is 0.5 mm. <Implementation of one cycle of extraction method> The <Implementation of one cycle of extraction method> of Example 1 is carried out in the same manner as the <Implementation of one cycle of extraction method> of Example 1, except that the extraction apparatus 1A equipped with a confluence section 13 having the inner diameter and cross-sectional area shown in the "Confluence Section" column of Table 1 is used instead of the extraction apparatus 1 used in Example 1. The pH of the aqueous phase (25°C) and the Co ion content are measured in the same manner as in Example 1. Furthermore, in the extraction and separation cycle in Example 5, it can be confirmed that the three-liquid mixture flowing out from the downstream mixing unit 14b has already reached extraction equilibrium.

[0148] <Implementation of 10-Cycle Extraction Method> In the <Implementation of 10-Cycle Extraction Method> of Example 1, the <Implementation of 10-Cycle Extraction Method> of Example 5 is carried out in the same manner as in the <Implementation of 10-Cycle Extraction Method> of Example 1, except that an extraction device 1A equipped with a confluence section 13 having the inner diameter and cross-sectional area shown in the "Confluence Section" column of Table 1 is used instead of the extraction device 1 used in Example 1, and the pH and Co ion content of the aqueous phase (25°C) obtained by performing 10 consecutive extraction and separation cycles are measured in the same manner as in Example 1. It can be confirmed that in each extraction and separation cycle, the three-liquid confluence liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0149] [Example 6] <Implementation of one-cycle extraction method> The <Implementation of one-cycle extraction method> of Example 6 is carried out in the same manner as the <Implementation of one-cycle extraction method> of Example 3, except that the flow rates of the aqueous phase and the oil phase are changed to the values ​​shown in the "Flow Rate" column of Table 1, and the pH and Co ion content of the aqueous phase (25°C) are measured in the same manner as in Example 1. It can be confirmed that in the extraction separation cycle in Example 6, the three-liquid combined liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0150] <Implementation of 10-Cycle Extraction Method> In the <Implementation of 10-Cycle Extraction Method> of Example 3, the <Implementation of 10-Cycle Extraction Method> of Example 6 is carried out in the same manner as in the <Implementation of 10-Cycle Extraction Method> of Example 3, except that the flow rates of the aqueous phase and the oil phase are changed to the values ​​shown in the "Flow Rate" column of Table 1. After performing 10 consecutive extraction and separation cycles, the pH and Co ion content of the aqueous phase (25°C) obtained are measured in the same manner as in Example 1. It can be confirmed that in each extraction and separation cycle, the three-liquid combined liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0151] [Examples 8-12] <Implementation of one-cycle extraction method> Except for the fact that, in the <Implementation of one-cycle extraction method> of Example 7, an oil phase containing the extractant shown in the "Extractant (Solution)" column of Table 1 is used instead of the oil phase containing the extractant PC-88A, and the pH is adjusted to the pH shown in the "pH" column of Table 1, the <Implementation of one-cycle extraction method> of Examples 8-12 is carried out in the same manner as in Example 7, and the pH and Co ion content of the aqueous phase (25°C) are measured in the same manner as in Example 1. It can be confirmed that in the extraction separation cycle in each example, the three-liquid combined liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0152] <Implementation of 10-Cycle Extraction Method> Except for the fact that, in the <Implementation of 10-Cycle Extraction Method> of Example 7, an oil phase containing the extractant shown in the "Extractant (Solution)" column of Table 1 is used instead of the oil phase containing the extractant PC-88A, and the pH is adjusted to the pH shown in the "pH" column of Table 1, the <Implementation of 10-Cycle Extraction Method> of Examples 8 to 12 is carried out in the same manner as in Example 7, and the pH and Co ion content of the aqueous phase (25°C) obtained by performing 10 consecutive extraction and separation cycles are measured in the same manner as in Example 1. It can be confirmed that in each extraction and separation cycle in each example, the three-liquid combined liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0153] [Comparative Example 1] Comparative Example 1 extracts Co ions using a batch extraction method with a mixer settler (5L) instead of a flow extraction method. <Implementation of one cycle of extraction method> An aqueous solution containing Co ions and an oil phase containing the extractant PC-88A are each added to the mixer settler in amounts of 50% by volume of the mixer settler's capacity and stirred. An aqueous solution containing a pH adjusting agent is then added to control the pH to 4.2. The internal temperature of the mixer settler is adjusted to the temperature shown in the "Temperature" column of Table 1 and stirred for 30 minutes. After that, only the aqueous phase is removed from the settler section and Co ions are extracted. The pH and Co ion content of the recovered aqueous phase (25°C) are measured in the same manner as in Example 1.

[0154] <Implementation of 10-Cycle Extraction Method> Except for using the oil phase obtained by back-extracting the oil phase containing the extractant PC-88A removed from the settler section in the <Implementation of 1-Cycle Extraction Method> described above as the oil phase for the next cycle, the extraction and separation cycle is performed 10 times consecutively in the same manner as in the <Implementation of 1-Cycle Extraction Method> described above. That is, the prepared oil phase containing the extractant PC-88A is used in the extraction and separation cycle for 10 consecutive cycles. The Co ion content (residual amount) of the aqueous phase (25°C) obtained by performing the extraction and separation cycle for 10 consecutive cycles is measured in the same manner as in the <Implementation of 1-Cycle Extraction Method> described above. It can be confirmed that the three-liquid combined liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium in each extraction and separation cycle. Each oil phase removed from the settler section is recovered in the same manner as in the <Implementation of 10-Cycle Extraction Method> of Example 1.

[0155] [Comparative Examples 3-5] <Implementation of a 1-cycle extraction method> Except for changing the temperature during mixing in the <Implementation of a 1-cycle extraction method> of Comparative Example 1 to the value shown in the "Mixing Section" column of the "Temperature" column in Table 1, the <Implementation of a 1-cycle extraction method> of Comparative Examples 3-5 is carried out in the same manner as the <Implementation of a 1-cycle extraction method> of Comparative Example 1, and the pH and Co ion content of the aqueous phase cooled to 25°C are measured in the same manner as in Example 1. It can be confirmed that in the extraction separation cycle in each comparative example, the three-liquid mixture flowing out from the downstream mixing section 14b has already reached extraction equilibrium. <Implementation of a 10-cycle extraction method> Except for changing the temperature during mixing in the <Implementation of a 1-cycle extraction method> of Comparative Examples 3-5 is carried out in the same manner as the <Implementation of a 1-cycle extraction method> of Comparative Example 1, and the pH and Co ion content of the aqueous phase cooled to 25°C are measured in the same manner as in Example 1. Furthermore, in the extraction and separation cycle of each comparative example, it can be confirmed that the three-liquid mixture flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0156] <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. ＳＴThe results calculated as described above are shown in Table 1.

[0157] <Evaluation 1: Evaluation of Initial Extraction Amount> In each example and comparative example, the initial extraction rate (unit: %) of the extracted metal ions is calculated based on the following formula, using the metal ion concentration CI in the prepared aqueous phase (aqueous phase before the first separation and extraction) and the metal ion concentration C1 in the aqueous phase after the first separation and extraction operation. Initial extraction rate (%) = [(CI - C1) / CI] × 100 In this test, the initial extraction amount is evaluated based on the calculated initial extraction rate according to the following evaluation criteria. The results are shown in Table 1. In this test, a larger initial extraction rate indicates that a larger amount of a specific metal ion can be extracted into the oil phase in one extraction and separation cycle. In this test, a score of E or higher is considered a pass. Specifically, the initial extraction rates are 87.5% for Example 1, 92.9% for Example 3, 95.8% for Example 7, 85.8% for Comparative Example 2, and 82.5% for Comparative Example 3. - Evaluation Criteria - A: Initial sampling rate of 98% or higher B: Initial sampling rate of 95% or higher but less than 98% C: Initial sampling rate of 92% or higher but less than 95% D: Initial sampling rate of 90% or higher but less than 92% E: Initial sampling rate of 85% or higher but less than 90% F: Initial sampling rate less than 85%

[0158] <Evaluation 2: Evaluation of Repeated Durability> In each example and comparative example, the 10-time extraction rate (unit: %) of the extracted metal ions is calculated from the metal ion concentration CI in the prepared aqueous phase (aqueous phase before the first separation and extraction operation) and the metal ion concentration C10 in the aqueous phase after the 10th separation and extraction operation, based on the following formula: 10-time extraction rate (%) = [(CI - C10) / CI] × 100 In this test, the difference between the initial extraction rate and the 10-time extraction rate (initial extraction rate - 10-time extraction rate) in <Evaluation 1: Evaluation of Initial Extraction Amount> above is calculated, and this extraction rate difference is evaluated based on the following evaluation criteria. The results are shown in Table 1. In this test, the smaller the extraction rate difference, the more it indicates that even if the extractant is used repeatedly (even if the separation and extraction operation is performed repeatedly), the high extraction rate shown by the unused metal extractant can be maintained and specific metal ions can be recovered, and the extractant (compound used as a metal extractant) shows high durability. In this test, E or higher is considered a pass. Specifically, the differences in extraction rates were 6.7% for Example 1, 4.6% for Example 3, 5.0% for Example 7, 9.2% for Comparative Example 2, and 9.2% for Comparative Example 3. - Evaluation Criteria - A: Difference in extraction rate is less than 1.0% B: Difference in extraction rate is 1.0% or more and less than 2.5% C: Difference in extraction rate is 2.5% or more and less than 4.0% D: Difference in extraction rate is 4.0% or more and less than 6.0% E: Difference in extraction rate is 6.0% or more and less than 8.0% F: Difference in extraction rate is 8.0% or more and less than 10% G: Difference in extraction rate is 10% or more

[0159]

[0160] [Examples 13-16] <Implementation of one cycle of extraction method> Except for using a Mn ion-containing aqueous solution, Ni ion-containing aqueous solution, Mg ion-containing aqueous solution, or Cu ion-containing aqueous solution instead of the Co ion-containing aqueous solution in Example 3, and adjusting the pH to the pH shown in the "pH" column of Table 2, Examples 13-16 are carried out in the same manner as in Example 3, and the pH of the aqueous phase (25°C) and the content of metal ions are measured in the same manner as in Example 1. The confluence conditions and mixing conditions in steps 1 and 2C of each example are shown in the "Confluence Conditions and Mixing Conditions" column of Table 2 (the same applies to the <Implementation of 10 cycles of extraction method> of each example). In each example, it can be confirmed that the three-liquid confluence liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium in the extraction separation cycle.

[0161] <Implementation of 10-Cycle Extraction Method> In the <Implementation of 10-Cycle Extraction Method> of Example 3, a Mn-containing aqueous solution, Ni-containing aqueous solution, Mg-containing aqueous solution, or Cu-containing aqueous solution is used instead of the Co-containing aqueous solution, and the pH is adjusted to the pH shown in the "pH" column of Table 2. Except for these differences, the <Implementation of 10-Cycle Extraction Method> of Examples 13 to 16 is carried out in the same manner as in Example 3, and the pH and metal ion content of the aqueous phase (25°C) obtained by performing 10 consecutive extraction and separation cycles are measured in the same manner as in Example 1. It can be confirmed that in each extraction and separation cycle in each example, the three-liquid combined liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0162] <Calculation of Kinetic Energy> In each embodiment, the kinetic energy E of both the aqueous phase and the oil phase ＳＴ The results calculated as described above are shown in Table 2.

[0163] <Evaluation 1: Evaluation of initial extraction amount> For Examples 13 to 16, the initial extraction amount of each metal ion was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0164] <Evaluation 2: Evaluation of Repeat Durability> For Examples 13 to 16, the difference between the initial extraction amount and the extraction rate after 10 times (initial extraction rate - extraction rate after 10 times) for each metal ion was calculated in the same manner as in Example 1, and this difference in extraction rate was evaluated. The results are shown in Table 2.

[0165] [Example 17] <Implementation of one-cycle extraction method> The <Implementation of one-cycle extraction method> of Example 17 was carried out in the same manner as the <Implementation of one-cycle extraction method> of Example 3, except that an aqueous solution containing both Co ions and Ni ions was used instead of the aqueous solution containing Co ions. The pH of the aqueous phase (25°C) and the content of metal ions were measured in the same manner as in Example 1. As a result, the content of Ni ions in the aqueous phase (residual amount) was 9.0 × 10⁻⁶. ３ ppm, Co ion content (residual amount) is 8.5 × 10 ２ The concentration is ppm, and Co ions can be selectively extracted. The confluence and mixing conditions in steps 1 and 2C of Example 17 are shown in the "Confluence and Mixing Conditions" column of Table 2 (the same applies to the <Implementation of 10 cycles of extraction method> of Example 17). It can be confirmed that in the extraction and separation cycle of Example 17, the three-liquid confluence liquid flowing out from the downstream mixing section 14b has already reached extraction equilibrium.

[0166] <Implementation of 10-Cycle Extraction Method> In the <Implementation of 10-Cycle Extraction Method> of Example 3, the <Implementation of 10-Cycle Extraction Method> of Example 17 was carried out in the same manner as in the <Implementation of 10-Cycle Extraction Method> of Example 3, except that an aqueous solution containing both Co ions and Ni ions was used instead of the Co ion-containing aqueous solution. The pH and metal ion content of the aqueous phase (25°C) obtained by performing 10 consecutive extraction and separation cycles were measured in the same manner as in Example 1. As a result, Co ions were selectively extracted in each extraction and separation cycle. It can be confirmed that in each extraction and separation cycle in each example, the three-liquid mixture flowing out from the downstream mixing section 14b had already reached extraction equilibrium.

[0167] <Calculation of Kinetic Energy> In Example 17, the kinetic energy E of both the aqueous phase and the oil phase was calculated. ＳＴThe results calculated as described above are shown in Table 2.

[0168] <Evaluation 1: Evaluation of Initial Extraction Amount> For Example 17, the initial extraction amount of selectively extracted Co ions was evaluated in the same manner as in Example 1. The results are shown in Table 2. The initial extraction amount of Co ions was 92.9%.

[0169] <Evaluation 2: Evaluation of Repeat Durability> For Example 17, the difference between the initial extraction amount of selectively extracted Co ions and the extraction rate after 10 attempts (initial extraction rate - extraction rate after 10 attempts) was calculated in the same manner as in Example 1, and this extraction rate difference was evaluated. The results are shown in Table 2. The extraction rate difference was 5.4%.

[0170]

[0171] The results in Tables 1 and 2 show the following: In the batch extraction method using a mixer-settler, increasing the temperature of the mixing section can improve the initial extraction volume and repeated durability, but the improvement effect is small and not sufficient (Comparative Examples 1 and 3-5). On the other hand, in the flow extraction method in which both phases are mixed at the same temperature as the water and oil phases at the start of flow, there is some improvement in the initial extraction volume and repeated durability compared to the batch extraction method using a mixer-settler, but the improvement effect is not sufficient (Comparative Example 2). In contrast, in the flow extraction method using a flow reactor, mixing both phases at a temperature higher than the water and oil phases at the start of flow can improve the initial extraction volume and repeated durability, and it can be seen that the higher the mixing temperature, the greater the improvement effect on the initial extraction volume and repeated durability (Examples 1-12). Furthermore, it can be seen that the initial extraction volume and repeated durability can be improved by changing the flow conditions of the water and oil phases, and that the improvement effect on the initial extraction volume and repeated durability can be further enhanced by adjusting the flow velocity, the inner diameter of the mixing section (reduction ratio of flow diameter), and the kinetic energy. Furthermore, it was found that using a phosphate-based compound among acidic extractants allows for an even higher level of both initial extraction yield and repeated durability. Also, as shown in Table 2, in a flow extraction method using a flow reactor, mixing the aqueous and oil phases at a temperature higher than the initial flow temperature of the aqueous and oil phases improves the initial extraction yield and repeated durability even when the metal ions are changed (Examples 13-16). Moreover, even if the aqueous phase contains multiple types of metal ions, it is possible to selectively extract specific metal ions, and excellent initial extraction yield and repeated durability for specific metal ions are achieved (Example 17).

[0172] From the above results, it can be seen that, according to the present invention, which mixes the aqueous and oil phases at a temperature higher than the initial temperature of the aqueous and oil phases in a flow extraction method, even if the aqueous phase contains multiple types of ions, it is not limited to combinations of Co ions and Ni ions, and specific metal ions can be selectively extracted. Furthermore, it is possible to achieve both an increased initial extraction amount and repeated durability for specific ions. For this reason, the extraction method of the present invention is useful for reducing extraction costs and realizing industrialization.

[0173] 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.

[0174] This application claims priority based on Japanese Patent Application No. 2024-228729, filed in Japan on 25 December 2024, the contents of which are incorporated herein by reference as part of this specification.

[0175] 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-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 metal ions and an oil phase containing an extractant during flow, mixing the two phases, and then separating the phases to extract the metal ions into the oil phase, wherein the two phases are mixed at a temperature higher than the temperatures of the aqueous and oil phases at the start of flow.

2. The method for extracting metal ions according to claim 1, wherein both phases are mixed at a temperature exceeding 60°C.

3. The method for extracting metal ions according to claim 1, wherein both phases are mixed at a temperature of 95°C or lower.

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 ratio of the reduction in each flow diameter when the aqueous phase and the oil phase are mixed is 0.1 to 0.

9.

6. When mixing the aqueous phase and the oil phase using collisions between the circulating phases, the kinetic energy per unit area and per unit time of the aqueous phase and the oil phase are 1 to 1.0 × 10⁻¹⁰, respectively. ５ J / sec / m ２ The method for extracting metal ions according to claim 1.

7. The method for extracting metal ions according to claim 1, wherein the aqueous phase contains multiple types of metal ions, and at least one of these metal ions is separated and extracted from the other types of metal ions.

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

9. The method for extracting metal ions according to claim 8, wherein the acidic extractant contains a phosphate compound.

10. The method for extracting metal ions according to claim 8, 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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