Metal ion extraction method

Abstract

Provided is a metal ion extraction method in which, after an aqueous phase containing metal ions and an oil phase containing an acidic extractant are merged while being circulated to mix the two phases, phase separation is performed, and the metal ions are extracted into the oil phase, wherein the metal ion extraction method comprises: a step in which the content of the acidic extractant in the oil phase being circulated is 35-100 vol%, and, after reducing the respective flow diameters for the circulating aqueous phase and oil phase, the phases are merged with each other and subsequently circulated; a step in which the aqueous phase, the oil phase, and an aqueous pH adjuster solution are merged and further circulated; and a step in which, after the extraction of the metal ions being extracted reaches extraction equilibrium, the merged three-component liquid is phase-separated.

Description

Metal ion extraction method

[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 instruments, and ensuring a stable supply of high-purity valuable metals presents a major challenge. These valuable metals are typically mined as a mixture of multiple metals, requiring isolation and refinement (high purification) of the desired valuable metal from the mined mixture. Furthermore, since the amount of valuable metals that can be extracted from mines is limited, ensuring a stable supply of precious metals, which are essential for precision instruments, presents a major challenge. Therefore, technologies for recovering valuable metals from industrial waste without relying on mining are gaining importance. In particular, with the widespread use of electric vehicles, the amount of discarded lithium-ion batteries (LiBs) is increasing year by year. LiBs use positive electrode active materials containing metal elements such as cobalt and nickel, and demand for cobalt and nickel is expected to increase significantly. To meet the resulting increase in demand for valuable metals, it is desirable not only to increase mining volume but also to establish metal recycling technologies for discarded LiBs.

[0003] Wet extraction (solvent extraction) is a widely used method for isolating and purifying valuable metals from mining mixtures and for recycling metals from waste materials. In wet extraction, an aqueous solution (aqueous phase) containing metal element ions (simply referred to as metal ions) is brought into contact with an organic phase containing a metal extractant, mixed, and allowed to stand to separate. The metal ions coordinated with the metal extractant are then transferred (extracted) into the organic phase. The organic phase is then removed, and the metal ions are stripped and, if necessary, purified, enabling the isolation and purification of the target metal and recycling as (high-purity) metal.

[0004] As such a wet extraction method, a flow extraction method has been studied in recent years, with the aim of improving extraction workability, etc., in which the aqueous phase and the oil phase are merged while flowing, thereby extracting metal ions in the oil phase into the aqueous phase. For example, Patent Document 1 describes an extraction method for extracting a specific component from a raw material fluid into an extractant using an extraction apparatus having extractors in multiple stages, each having a flow path for extraction, and the extractors in each stage being connected to each other so that at least a portion of the fluid discharged from the flow path of the extractor in each stage is supplied to the flow path of the extractor in the next stage, the method comprising: an extraction step of extracting the specific component from the raw material fluid into the extractant while circulating the raw material fluid and the extractant through the flow path of the extractor in each stage; a withdrawal step of withdrawing a mixed fluid of the raw material fluid and the extractant from the flow path of the extractor in each stage before extraction of the specific component from the raw material fluid in the flow path of the extractor in each stage reaches extraction equilibrium; a separation step of separating the mixed fluid withdrawn from the flow path of the extractor in each stage into the raw material fluid and the extractant; and a raw material fluid supply step of supplying each raw material fluid withdrawn from the flow path of the extractor in each stage and separated in the separation step to the flow path of the extractor in the next stage. and a pH adjustment step of adjusting the pH of the raw fluid, which is drawn out from the flow path of the extractor of a specific stage and separated in the separation step, to restore the pH of the raw fluid to the original pH value resulting from the extraction of the specific component in the extraction step, before the raw fluid is supplied to the flow path of the extractor of the next stage. One of the features of this method is that, in order to improve the time efficiency of the extraction process, when extracting a specific component from the raw fluid into an extractant, the mixed fluid of the raw fluid and the extractant is drawn out from the flow path and separated before the extraction of the specific component reaches extraction equilibrium.

[0005] JP 2016-019939 A

[0006] In wet extraction methods, whether batch or flow, increasing the amount of metal ions extracted into the oil phase (the mass of metal ions extracted into the oil phase per unit volume, also referred to as the absolute extraction amount) is required for the purposes of reducing extraction costs and achieving industrialization. It is also required to maintain a high extraction rate of metal ions into the oil phase (the mass ratio of metal ions extracted into the oil phase to the metal ions present in the aqueous phase) even when the oil phase is reused and multiple extraction and separation cycles are performed. Generally, in wet extraction methods, fluctuations in extraction conditions tend to cause fluctuations in extraction resolution (extraction selectivity). Therefore, suppressing fluctuations in extraction conditions (extraction environment), such as extraction temperature, requires the installation of additional manufacturing equipment, such as temperature control equipment, which also reduces workability. Therefore, in order to reduce extraction costs and achieve industrialization, maintaining the high extraction resolution achieved at room temperature, even under extraction conditions such as extraction temperature, is also required. However, Patent Document 1 does not consider at all how to increase the amount extracted into the oil phase or how to achieve high extraction resolution under low-temperature conditions.

[0007] An object of the present invention is to provide a method for extracting metal ions, which enables a high extraction yield into an oil phase, maintains a high extraction rate even after multiple extraction and separation cycles, and maintains high extractive resolution even under low-temperature conditions.

[0008] The present inventors conceived the idea that, in a wet extraction method, mixing the oil and aqueous phases in a flow system with a large interfacial area between the oil and aqueous phases and a small reaction field could improve the mixing state of the oil and aqueous phases even when the extractant content in the oil phase is increased. Based on this idea, the present inventors continued to conduct intensive research and found that in a flow wet extraction method (flow mixing method) in which the oil and aqueous phases are merged and mixed during flow, followed by phase separation, by reducing the flow diameters of the oil and aqueous phases before merging, and then merging the two phases, preferably setting the pH at a predetermined level, and then continuing to flow while mixing the two phases, the amount of metal ions extracted into the oil phase can be increased and high extraction resolution can be maintained even under low temperature conditions. Furthermore, they found that the extractant in the oil phase separated from the aqueous phase is inhibited from deterioration, decomposition, etc., and that even when this oil phase is reused in the above-mentioned flow wet extraction method, the desired high extraction rate can be maintained multiple times. Based on these findings, further research led to the completion of the present invention.

[0009] That is, the above-mentioned problems have been solved by the following means: <1> A method for extracting metal ions, in which an aqueous phase containing metal ions and an oil phase containing an acidic extractant are joined midway through flow, the two phases are mixed, and then phase-separated to extract the metal ions into the oil phase, the method comprising the steps of: setting the content of the acidic extractant in the flowing oil phase to 35 to 100 volume %, reducing the flow diameters of the flowing aqueous phase and oil phase, then joining them and continuing to flow them; joining the aqueous phase and the oil phase with an aqueous pH adjuster solution and further flowing them; and phase-separating the three-liquid combined liquid after the extraction of the target metal ions reaches extraction equilibrium. <2> The method for extracting metal ions according to <1>, in the further flowing step, the two-liquid combined liquid of the aqueous phase and the oil phase joined in the continued flowing step and the aqueous pH adjuster solution are joined and further flowed. <3> The method for extracting metal ions according to <1>, wherein in the subsequent flowing step, a further flowing step is carried out to merge the aqueous phase, the oil phase, and the aqueous pH adjuster solution all at once and further flow them. <4> The method for extracting metal ions according to any one of <1> to <3>, wherein in at least one of the subsequent flowing step and the further flowing step, the merged liquid is flowed through a flow path equipped with a static mixer. <5> The method for extracting metal ions according to any one of <1> to <4>, wherein the aqueous phase and the oil phase are merged by utilizing collision of the flowing phases. <6> The method for extracting metal ions according to any one of <1> to <5>, wherein, when the aqueous phase and the oil phase are merged, the reduction ratio of the flow diameters of the respective phases is 0.1 to 0.8. <7> When the aqueous phase and the oil phase are merged by utilizing collision of the flowing phases, the kinetic energy per unit area and per unit time of the aqueous phase and the oil phase is 50 to 100,000 J / sec / m ２The method for extracting metal ions according to any one of <1> to <6>, wherein the combined three-liquid solution is allowed to stand to separate into an aqueous phase and an oil phase. <8> The method for extracting metal ions according to any one of <1> to <7>, wherein the combined three-liquid solution is allowed to stand to separate into an aqueous phase and an oil phase. <9> The method for extracting metal ions according to any one of <1> to <8>, wherein the metal ions contain multiple types of metal ions, and at least one of the types of metal ions is separated and extracted from the other types of metal ions. <10> The method for extracting metal ions according to any one of <1> to <9>, wherein an extraction and separation cycle consisting of a subsequent flowing step, a further flowing step, and a phase separation step is performed multiple times, and the oil phase separated in the phase separation step is reused as the oil phase in the next extraction and separation cycle. <11> The method for extracting metal ions according to any one of <1> to <10>, wherein the acidic extractant contains a phosphoric acid compound. <12> The method for extracting metal ions according to <11>, wherein the acidic extractant is represented by the following formula (I): In 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—.

[0010] The present invention provides a method for extracting metal ions, which can achieve a high extraction amount into an oil phase, maintain a high extraction rate even after multiple extraction and separation cycles, and maintain high extraction resolution even under low-temperature conditions. The above and other features and advantages of the present invention will become more apparent from the following description, taken in conjunction with the accompanying drawings, where appropriate.

[0011] Fig. 1 is a schematic front view showing an example of an extraction apparatus suitable for use in the metal ion extraction method of the present invention. Fig. 2 is a schematic front view showing another example of an extraction apparatus suitable for use in the metal ion extraction method of the present invention. Fig. 3 is a diagram showing a modified flow pipe used in the extraction apparatus suitable for use in the metal ion extraction method of the present invention. Fig. 4 is a graph showing the relationship between the content of acidic extractant in the oil phase and the extraction rate at the 20th extraction separation cycle in an example.

[0012] In the present invention, when describing the content, physical properties, etc. of a component by indicating a numerical range, if the upper and lower limits of the numerical range are described separately, any of the upper and lower limits can be appropriately combined to form a specific numerical range. On the other hand, when describing multiple numerical ranges represented using "to", the upper and lower limits forming the numerical range are not limited to the combination of the specific upper and lower limits written before and after "to" as a specific numerical range, but can be any numerical range obtained by appropriately combining the upper and lower limits of each numerical range. Note that in the present invention, a numerical range represented using "to" means a range that includes the numerical values ​​written before and after "to" as the upper and lower limits. In the present invention, when a compound is referred to (for example, when "compound" is added to the end), it is used to mean not only the compound itself, but also its salts and ions. Furthermore, it also means to include derivatives that have been partially modified, such as by introducing a substituent, within a range that does not impair the effects of the present invention. In the present invention, with respect to substituents, linking groups, etc. (hereinafter referred to as substituents, etc.) that are not specified as substituted or unsubstituted, this means that the group may have an appropriate substituent. Therefore, in the present invention, even when simply described as a YYY group, this YYY group includes not only an embodiment in which it has no substituent, but also an embodiment in which it further has a substituent. This also applies to compounds in which substituted or unsubstituted is not specified. Preferred substituents include, for example, groups selected from the substituent G described below. In the present invention, when there are multiple substituents, etc., designated by a specific symbol, or when multiple substituents, etc. are specified simultaneously, this means that the respective substituents, etc. may be the same or different from each other. Furthermore, even if not otherwise specified, when multiple substituents, etc., are adjacent, they may be linked to each other or fused to form a ring.

[0013] In this specification, a "metal element belonging to a different group in the periodic table of elements" is referred to as a "different group metal element," and in particular, a "different group metal element in the same period in the periodic table" may be referred to as a "same-period, different-group metal element." Furthermore, an "ion of a different group metal element" and an "ion of a different group metal element in the same period" may be referred to as a "different group metal ion" and an "same-period, different-group metal ion," respectively. In the present invention, "ppm" indicating a content, etc., is based on mass and represents "mass ppm" unless otherwise specified.

[0014] The metal ion 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 acidic extractant are joined during flow, the two phases are mixed while flowing, and then phase-separated into the aqueous and oil phases, and the metal ions are extracted into the oil phase. The extraction method of the present invention involves a flow-type wet extraction method in which the aqueous and oil phases are used in the steps described below. This method achieves high extraction yields of metal ions present in the aqueous phase, maintains a high extraction rate (also known as recovery rate) even after multiple extraction and separation cycles, and transfers (extracts) them to the oil phase with high extraction resolution even under low-temperature conditions. The metal ion extraction method of the present invention (hereinafter sometimes referred to as the extraction method of the present invention) will be described with reference to an apparatus suitable for use in the extraction method of the present invention.

[0015] [Extraction Apparatus Suitable for Use in the Extraction Method of the Present Invention] The extraction apparatus suitable for use in the extraction method of the present invention (hereinafter sometimes referred to as the extraction apparatus suitable for the present invention) is not particularly limited, and may, for example, have an aqueous phase flow pipe for circulating (transporting) the aqueous phase to the confluence section, an oil phase flow pipe for circulating (transporting) the oil phase to the confluence section, a confluence section connected downstream 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, and a separation section connected downstream of the mixing section in the flow direction. Herein, the aqueous phase flow pipe, the oil phase flow pipe, and the mixing section may have the same configuration, arrangement, etc. as the aqueous phase flow pipe, the oil phase flow pipe, and the mixing section in extraction apparatus 1 or 2 described below. Each step of the extraction method of the present invention can be suitably carried out in this apparatus. Hereinafter, the upstream side and the downstream side with respect to the flow direction of the oil phase, the aqueous phase, or the confluence liquid may be simply referred to as the downstream side and the upstream side, respectively.

[0016] <Extraction Apparatus 1> Extraction apparatus 1, an example of an extraction apparatus suitable for the present invention, is suitable as an apparatus that performs, in this order, a step of first mixing an aqueous phase and an oil phase and continuously flowing them, and then a step of combining the combined two-liquid combined liquid with an aqueous pH adjuster solution and further flowing them. As shown in Figure 1, this extraction apparatus 1 has an aqueous phase flow pipe 11, through which the aqueous phase flows to the confluence, and having a tapered portion (tapered portion) 11a downstream in the direction of flow of the aqueous phase, and an oil phase flow pipe 12, through which the oil phase flows to the confluence, and having a tapered portion (tapered portion) 12a downstream in the direction of flow of the oil phase, with the aqueous phase flow pipe 11 and the oil phase flow pipe 12 arranged opposite each other so as to be aligned. The extraction apparatus 1 also has a confluence portion 13 that connects the open end of tapered portion 11a and the open end of tapered portion 12a to combine the two phases. Here, the inner diameters of the aqueous phase flow pipe 11 and the oil phase flow pipe 12 are reduced downstream by the tapered portions 11a and 12a, respectively. Depending on the shape of each tapered portion, the opening diameter of the open end of each tapered portion is smaller (thinner) than the inner diameter of the upstream open end of each tapered portion (the connection portion with the flow pipe having a constant inner diameter). The cross-sectional shape perpendicular to the center line of each of the flow pipes 11 and 12 and the tapered portions 11a and 12a is not particularly limited, and various shapes, such as circular, elliptical, semicircular, polygonal, etc., can be employed. The constant inner diameter of each of the flow pipes 11 and 12 (the inner diameter of the upstream open end of the tapered portion) is not particularly limited and can be determined appropriately. It can be, for example, 0.1 to 100 mm, with a value of 0.5 to 10 mm being preferred in terms of improving the mixing state. The flow diameters (inflow diameters) of the aqueous phase and oil phase flowing from each of the flow pipes 11 and 12 into the confluence 13 are reduced by the tapered portions 11a and 12a compared to the flow diameters of the aqueous phase and oil phase flowing through each of the flow pipes 11 and 12. The ratio of the inner diameter of the open end of the tapered portion to the constant inner diameter of each of the flow pipes 11 and 12 (inner diameter of the open end of the tapered portion / inner diameter of the connection portion of the flow pipe with the constant inner diameter tapered portion) is not particularly limited and is determined appropriately depending on the flow rate, etc., and is preferably the same as the reduction ratio of the flow diameters of the two phases, which will be described later. The inner diameters of the aqueous phase flow pipe 11 and the oil phase flow pipe 12 may be different, but are preferably set to the same.The inner diameters of the open ends of the tapered portions 11a and 12a, and further the inner diameter reduction ratios of the tapered portions 11a and 12a (the ratio of the inner diameters) may be different from each other, but are usually set to be the same in consideration of the mixing state, etc. In the present invention, the inner diameter refers to an equivalent diameter, which will be described in detail later.

[0017] The extraction apparatus 1 has a tubular mixing section 14 extending from the confluence section 13 in a direction approximately perpendicular to the aqueous phase flow pipe 11. A pH adjuster transfer pipe 15 for transferring an aqueous pH adjuster solution is connected to the mixing section 14. The mixing section 14 has a tapered section (reverse tapered section) whose inner diameter gradually increases from the connection with the confluence section 13 toward the downstream side. The dimensions of this tapered section are not particularly limited and can be set appropriately, for example, to the same ratio as the reduction ratio of the flow diameters of the two phases described below. The extraction apparatus 1 has a separation section 16 connected to the downstream end of the mixing section 14 in the flow direction. The separation section 16 allows the incoming three-liquid mixture to stand and separate into an aqueous phase and an oil phase. In the mixing section 14, the section from the connection with the confluence section 13 to the connection with the pH adjuster transfer pipe 15 is referred to as the front-stage mixing section 14a, and the section from the connection with the pH adjuster transfer pipe 15 to the connection with the separation section 16 is referred to as the rear-stage mixing section 14b. The separation section 16 can be configured with a general storage container, a separation tower, a mixer settler, a separating funnel, or the like, 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. The oil phase discharge pipe 16a and the aqueous phase discharge pipe 16b may each be equipped with a valve and a transfer means, such as various pumps.

[0018] In the extraction apparatus 1, it is preferable to install a static mixer in the flow path of at least one of the front-stage mixing section 14a and the rear-stage mixing section 14b in the mixing section 14, and it is more preferable to install a static mixer in the flow path of the rear-stage mixing section 14b, in order to further improve the mixed state of the three-liquid confluent liquid.

[0019] A static mixer is a static mixer without a driving section. It mixes and stirs fluids entering the mixer by repeatedly dividing, recombining, and reversing direction using static mixing elements installed inside the mixer. Examples of static mixers include Sulzer, Kenix, Toray, and Noritake Company types. Static mixers preferably have four or more mixing elements, more preferably six to 30. These numbers of mixing elements are preferably arranged consecutively in a mixer pipe 10 cm to 2 m long. Alternatively, multiple static mixers of this type can be arranged in series. In this case, the entire series of multiple static mixers forms a single unit, forming the static mixer of the present invention. The size of the static mixer used in the present invention is appropriately determined depending on factors such as the production scale. For example, the equivalent diameter of the static mixer pipe can be 1 to 100 mm. Even if the internal cross-section of the static mixer is larger than the internal cross-section of the flow pipe, the flow pipe and the static mixer can be connected via a tube or the like that can connect the two. 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 overall length of the multiple static mixers arranged in series (including the spacing between the static mixers). When multiple static mixers are arranged in series, the spacing between adjacent static mixers can be set appropriately, taking into account the difference in the internal cross-sectional size of the static mixer and the internal cross-sectional size of the reaction flow channel connected to it. The spacing between adjacent static mixers can be, for example, 100 cm or less, 70 cm or less, 40 cm or less, 20 cm or less, or 10 cm or less.

[0020] Examples of materials for the static mixer include perfluoroalkoxyalkane (PFA), Teflon (registered trademark), aromatic polyether ketone resin, stainless steel, copper or copper alloy, nickel or nickel alloy, titanium or titanium alloy, quartz glass, lime soda glass, etc. From the viewpoints of flexibility, chemical resistance, etc., PFA, Teflon (registered trademark), stainless steel, nickel alloy, or titanium is preferred.

[0021] In the extraction apparatus 1, the aqueous phase flow pipe 11, the oil phase flow pipe 12, and the mixing section 14 can be three-way pipes having (or forming) tapered portions 11a and 12a, such as a T-shaped pipe or a Y-shaped pipe. In the extraction apparatus 1, the aqueous phase flow pipe 11, the oil phase flow pipe 12, the confluence section 13, and the front-stage mixing section 14a are sometimes referred to as the "oil-water mixing section," and the pH adjuster transfer pipe 15 and the rear-stage mixing section 14b are sometimes referred to as the "pH adjustment section."

[0022] Extraction Apparatus 2, another example of an extraction apparatus suitable for the present invention, is an apparatus that can perform, in a single step, the steps of mixing the aqueous phase and the oil phase and continuously flowing them, and then merging the two-liquid merged liquid with the aqueous pH adjuster solution and further flowing them, and is suitable as an apparatus that performs the steps of merging the aqueous phase, the oil phase, and the aqueous pH adjuster solution all at once and further flowing them. This extraction apparatus 2 has basically the same configuration as extraction apparatus 1, except that the aqueous pH adjuster solution transfer pipe 15 is connected to the merging section 23. As shown in FIG. 2 , this extraction apparatus 2 includes an aqueous phase flow pipe 11, which flows the aqueous phase to the confluence and has a tapered portion 11a downstream in the direction of aqueous phase flow; an oil phase flow pipe 12, which flows the oil phase to the confluence and has a tapered portion 12a downstream in the direction of aqueous phase flow; and a pH adjuster transfer pipe 15, which transfers the aqueous pH adjuster solution to the confluence. The pH adjuster transfer pipe 15 is disposed at a substantially right angle to the aqueous phase flow pipe 11 and the oil phase flow pipe 12, which are disposed on the same line. The pH adjuster transfer pipe 15 may have a tapered portion downstream in the direction of flow. The pH adjuster transfer pipe 15 also includes a confluence 23, which connects the open end of the tapered portion 11a, the open end of the tapered portion 12a, and the open end of the pH adjuster transfer pipe 15, and where the aqueous phase, oil phase, and aqueous pH adjuster solution are combined. Here, the aqueous phase flow pipe 11 and the oil phase flow pipe 12 are the same as the aqueous phase flow pipe 11 and the oil phase flow pipe 12 of the extraction apparatus 1. For example, the aqueous phase flow pipe 11 and the oil phase flow pipe 12 have tapered portions 11a and 12a, respectively, whose inner diameters decrease toward the downstream side. The shape of each tapered portion causes the opening diameter of the open end of each tapered portion to be smaller than the inner diameter of the upstream open end of each tapered portion (the connection portion with a flow pipe having a constant inner diameter). The flow diameters (inflow diameters) of the aqueous phase and oil phase flowing from each flow pipe 11 and 12 into the confluence 23 are reduced by the tapered portions 11a and 12a to be smaller than the flow diameters of the aqueous phase and oil phase flowing through each flow pipe 11 and 12. The ratio of the inner diameter of the open end of the tapered portion to the constant inner diameter of each flow pipe 11 and 12 (the inner diameter of the open end of the tapered portion / the inner diameter of the connection portion with the constant inner diameter tapered portion of the flow pipe) is not particularly limited and may be determined appropriately depending on the flow rate, etc., and is preferably the same as the reduction ratio of the flow diameters of the two phases, which will be described later.

[0023] The extraction apparatus 2 has a mixing section 24 extending from the confluence section 23 on an extension of the flow direction of the pH adjuster transfer pipe 15. The mixing section 24 has a tapered section (reverse tapered section) whose inner diameter gradually increases from the connection with the confluence section 23 toward the downstream side in the flow direction. The extraction apparatus 2 has a separation section 16 connected to the downstream end of the mixing section 24 in the flow direction, which allows the incoming combined liquid to stand and separate into an aqueous phase and an oil phase. This separation section 16 has the same configuration as the separation section 16 of the extraction apparatus 1.

[0024] In the extraction apparatus 2, it is preferable to install a static mixer in the flow path of the mixing section 24, as this can highly improve the mixing state of the three-liquid confluence. Static mixers are as described in the extraction apparatus 1. In the extraction apparatus 2, the aqueous phase flow pipe 11, the oil phase flow pipe 12, the pH adjuster transfer pipe 15, and the mixing section 24 can be four-sided pipes having (or formed with) tapered portions 11a and 12a, such as cross pipes. This extraction apparatus 2 is preferable in that it can shorten the flow path length of the mixing section 24. In the extraction apparatus 2, the configuration of the aqueous phase flow pipe 11, the oil phase flow pipe 12, the pH adjuster transfer pipe 15, the confluence section 23, and the mixing section 24 doubles as the "oil-water mixing section" and "pH adjustment section" of the extraction apparatus 1, and is sometimes referred to as the "oil-water mixing pH adjustment section."

[0025] In both extraction devices 1 and 2, the aqueous phase flow pipe 11 and the oil phase flow pipe 12 are configured such that their inner diameters decrease (reduced) by tapered portions 11a and 12a on the downstream side. 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 a structure having a tapered portion. For example, as shown in FIG. 3, a pipe connected to a large diameter portion 11b and a small diameter portion 11c can be used. Furthermore, in extraction devices 1 and 2, the flow pipes connected to the confluence portion 13 or 23 are arranged at an angle that is approximately right angles. However, in an extraction device suitable for the present invention, the angle of the pipes connected to the confluence portion is not particularly limited. For example, the aqueous phase flow pipe and the oil phase flow pipe can be double pipes or pipes having two internal flow paths. In this case, the two pipes are arranged parallel to each other, and the confluence angle between the flowing aqueous phase and the oil phase is 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 degree, since this can improve the mixing state due to the impact generated when the two phases confluence, and specifically, this is the same as the confluence angle described below.

[0026] [Fluids used in the extraction method of the present invention] In the extraction method of the present invention, fluids including an aqueous phase, an oil phase, and an aqueous solution of a pH adjuster 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.

[0027] In the present invention, the aqueous phase may contain one type of metal ion, but preferably contains at least two 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 3 to 14, and may also contain metal ions belonging to Groups 15 to 17. In the present invention, the aqueous phase preferably 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 3 to 14, and even more preferably contains ions of at least one transition metal element (metal element belonging to Groups 3 to 12). In an embodiment containing at least one transition metal element, the composition preferably contains two or more metal ions belonging to Groups 4 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 8 to 12, particularly 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 are preferably metal ions belonging to Periods 4 to 6 of the periodic table, and more preferably metal ions belonging to Periods 4 or 5. The number of types of metal ions is not particularly limited as long as it is two or more, and can be, for example, 2 to 15 types, preferably 2 to 8 types, and more preferably 2 to 5 types. The combination of multiple metal ions is not particularly limited, and examples of combinations of groups include 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 7, Group 9 and Group 10, and combinations of Group 7, Group 8, Group 9 and Group 10. In the present invention, two or more types of metal ions belonging to each group may be used, but it is preferred that only one type be used in terms of high selectivity.

[0028] Specific combinations of metal ions include, for example, combinations including Co and Ni, combinations including Co and Zn, combinations including Co and Cu, combinations including Rh and Ni, combinations including Zr and Rh, combinations including Mn, Co and Ni, and combinations of Mn, Fe, Co and Ni. The multiple types of metal ions contained in the aqueous phase may include metal ions of the same group, or may include metal ions of different groups. The number of types of different metal ions contained in the aqueous phase may be two or more, and is preferably, for example, two to four types, and more preferably two types.

[0029] The metal elements belonging to each group are not particularly limited, and appropriate atoms can be used. For example, preferred metal elements belonging to Group 1 include Li, Na, Rb, and Cs. Preferred metal elements belonging to Group 2 include Mg, Ca, Sr, and Ba. Preferred metal elements belonging to Group 3 include Sc and Y. Preferred metal elements belonging to Group 4 include Ti, Zr, and Hf. Preferred metal elements belonging to Group 5 include V, Nb, and Ta. Preferred metal elements belonging to Group 6 include Cr, Mo, and W. Preferred metal elements belonging to Group 7 include Mn and Tc. Preferred metal elements belonging to Group 8 include Fe, Ru, and Os. Preferred metal elements belonging to Group 9 include Co, Rh, and Ir. Preferred metal elements belonging to Group 10 include Ni, Pd, and Pt. Preferred metal elements belonging to Group 11 include Cu, Ag, and Au. Preferred examples of metal elements belonging to Group 12 include Zn, Cd, and Hg. Preferred examples of metal elements belonging to Group 13 include Al, Ga, In, and Tl. Preferred examples of metal elements belonging to Group 14 include Ga, Sn, and Pb. Preferred examples of metal elements belonging to Group 15 include Sb and Bi. Preferred examples of metal elements belonging to Group 16 include, but are not limited to, Te.

[0030] The metal ions can be prepared appropriately, and examples thereof include 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), materials recovered from metal waste, metals recovered from other wastes such as waste batteries (LiBs), and mixtures thereof. Metals recovered from waste LiBs can be recovered by known methods such as wet treatment and electrolysis.

[0031] The total content of metal ions in the aqueous phase is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 1,000,000 ppm by mass, preferably 1,000 to 100,000 ppm by mass, and more preferably 1,000 to 80,000 ppm by mass. In particular, the extraction method of the present invention can achieve a high extraction yield, so the total content of metal ions in the aqueous phase can be set high. 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, but can be, for example, 1,000 to 80,000 ppm by mass, and preferably 1,000 to 50,000 ppm by mass. The total content of metal ions belonging to Groups 3 to 7 and Groups 13 to 16 among the metal ions is not particularly limited and can be set as appropriate, but can be, for example, 1,000 to 60,000 ppm by mass, and preferably 1,000 to 30,000 ppm by mass. The content of the metal ions belonging to each group is not particularly limited and may be set as appropriate, but may be, for example, 1,000 to 60,000 ppm by mass, and preferably 1,000 to 50,000 ppm by mass. When two or more types of metal ions belonging to each group are contained, the content of the metal ions belonging to each group is the total content.

[0032] In the present invention, when the aqueous phase contains metal ions of different groups, the content of metal ions belonging to one group may be greater or less than the content of metal ions belonging to another group. When the aqueous phase contains metal ions of different groups, the extraction method of the present invention can separate and recover metal ions with high selectivity, so it is not necessary to set the content of metal ions belonging to different groups to a specific ratio. For example, the mass ratio of the content of metal ions belonging to a specific group (e.g., metal ions extracted at the maximum extraction rate) to the content of metal ions belonging to another group (e.g., metal ions other than the metal ions extracted at the maximum extraction rate (including metal ions that are not extracted)) [content of metal ions belonging to a specific group:content of metal ions belonging to another group] can be, for example, 100:1 to 10,000, preferably 100:10 to 5,000, and more preferably 100:50 to 1,000.

[0033] The pH of the aqueous phase is not particularly limited and can be set as appropriate. However, taking into consideration the solubility of metal ions, the formation of complex ions, and the like, it is preferably set to, for example, 0.1 to 10, and more preferably 2.0 to 9.0. The pH of the aqueous phase can be adjusted, for example, using an acid or alkali. Known acids can be used without any particular limitation, and examples thereof 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. Known alkalis can be used without any particular limitation, and examples thereof 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 is not particularly limited and can be set to, for example, 10 to 60°C. The aqueous phase used in the extraction method of the present invention, which is carried out under low-temperature conditions, is preferably set to the low-temperature conditions described below. The density (kg / m) of the aqueous phase ３ , 25°C) is not particularly limited and cannot be uniquely determined depending on the content of metal ions, etc., but is, for example, 900 to 2000 kg / m ３ This is because the kinetic energy EＳＴ is easily set to a suitable value, which results in improved extraction amount of metal ions, maintenance of a high extraction rate when performing multiple extraction and separation cycles (also referred to as durability), and extraction resolution (meaning room temperature resolution and low temperature resolution unless otherwise specified; the same applies hereinafter).

[0034] The aqueous phase may contain, as necessary, a ligand (compound) that coordinates with the metal ion or a compound that generates the ligand. The aqueous phase can be prepared by dissolving metal ions in water. The conditions for preparing the aqueous phase are not particularly limited. For example, the preparation temperature can usually be 10 to 60°C, but low temperature conditions, as described below, can also be used in consideration of the solubility of the metal ions, etc.

[0035] The aqueous phase may contain a masking agent in addition to the metal ions. Any known masking agent can be used without any particular limitation. Examples include monodentate ligands such as ammonia and chelating agents such as dithizone. In the extraction method of the present invention, the acidic extractant can coordinate to the metal ions alone and extract the metal ions into the oil phase. Therefore, the aqueous phase and the oil phase do not need to contain compounds that cooperate with the acidic extractant to extract the metal ions, such as compounds that coordinate to the metal ions or compounds that generate ligands, such as known acidic extractants. The extraction method of the present invention typically uses an aqueous phase containing a specific metal ion as an essential component and an oil phase containing an acidic extractant as an essential component.

[0036] <Oil Phase> The extraction method of the present invention uses an oil phase (organic phase) containing one or more acidic extractants. The oil phase may contain an organic solvent. The organic solvent that the oil phase may contain is not particularly limited, and any appropriate organic solvent can be used. Examples include alcohol solvents, ether solvents, hydrocarbon solvents (aromatic solvents, aliphatic solvents), halogenated solvents, etc. Among these, hydrocarbon solvents are preferred, and various solvents that are fractions of petroleum are more preferred, with aromatic, paraffinic, naphthenic, kerosene, gasoline, naphtha, kerosene, and diesel hydrocarbon solvents being even more preferred.

[0037] The acidic 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 phase and the oil phase, and transfers the metal ions to the oil phase. An appropriate acidic extractant can be selected from various known metal extractants and used. Furthermore, in terms of maintaining a high extraction yield and a high extraction rate even after multiple extraction and separation cycles, as well as maintaining high extractive resolution even under low-temperature conditions, it is preferable to use an acidic extractant selected from phosphoric acid compounds, and it is more preferable to use a compound represented by formula (I) described below. In the present invention, solubility in organic solvents refers to the ability of the acidic extractant to dissolve in an organic solvent at the content described below. The acidic extractant will be described later.

[0038] The content of the acidic extractant in the oil phase is determined taking into consideration the content of metal ions, the amount of coordination to the metal ions, etc. However, in the present invention, which employs a flow-type mixing method, the content of the acidic extractant can be set high, specifically, to 35 to 100% by volume. Therefore, by strengthening the interactions between the acidic extractants in the oil phase, the present invention can increase the amount of metal ions extracted and also suppress deterioration or decomposition of the acidic extractant due to pH adjusters, etc. Furthermore, by minimizing temperature-dependent changes in the viscosity of the oil phase or suppressing temperature-dependent changes in the frequency of contact between the acidic extractant and metal ions, fluctuations in the amount and extraction rate due to the operating temperature can be suppressed. In the present invention, the content of the acidic extractant in the oil phase is preferably 40% by volume or more, more preferably 50% by volume or more, even more preferably 60% by volume or more, and particularly preferably 70% by volume or more, in order to further enhance the amount of metal ions extracted, durability, and extraction resolution. The upper limit of the content of the acidic extractant can be set to 100% by volume, or to 80% by volume or less from the viewpoint of enhancing the low-temperature decomposition ability. The temperature of the oil phase is not particularly limited and can be set to, for example, 10 to 60°C. The oil phase used in the extraction method of the present invention, which is carried out under low-temperature conditions, is preferably set to low-temperature conditions as described below. The density of the oil phase (kg / m ３, 25°C) is not particularly limited and cannot be uniquely determined depending on the type of organic solvent, the type or content of the acidic extractant, etc., but is, for example, 500 to 1500 kg / m ３ This is because the kinetic energy E ＳＴ is easily set to a suitable value, and as a result, the amount of metal ions extracted, durability, and extraction resolution can be improved, which is preferable.

[0039] The oil phase is prepared by using an acidic extractant (liquid in the environment of use) either as is or as a solution in an organic solvent. The oil phase as a solution of the acidic extractant can be prepared by dissolving the acidic 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 low temperature conditions, as described below, can also be used in consideration of the solubility of metal ions, etc.

[0040] <pH Adjuster Aqueous Solution> The water forming the pH adjuster aqueous solution is not particularly limited, and (ultra)pure water, ion-exchanged water, etc. can be used. Examples of pH adjusters contained in the pH adjuster aqueous solution include the acids and alkalis described above that can be used to adjust the pH of the aqueous phase. Among these, the inorganic acids and inorganic alkalis described above are preferred, with hydrochloric acid or an aqueous hydrochloric acid solution and alkali hydroxides (hydroxides of Group 1 elements) being more preferred. The content of the pH adjuster in the pH adjuster aqueous solution is appropriately set to achieve a predetermined pH. The temperature of the pH adjuster aqueous solution is not particularly limited and can be, for example, 10 to 60°C. The pH adjuster aqueous solution used in the extraction method of the present invention, which is performed under low-temperature conditions, is preferably set under the low-temperature conditions described below. The pH adjuster aqueous solution can be prepared by dissolving a pH adjuster in water. The preparation conditions for the pH adjuster aqueous solution are not particularly limited. For example, the preparation temperature can usually be 10 to 60°C, but low-temperature conditions described below can also be used in consideration of the solubility of metal ions, etc.

[0041] [Extraction method of the present invention] The extraction method of the present invention is a flow-type wet extraction method using an aqueous phase containing metal ions, an oil phase containing an acidic extractant at a concentration of 35 to 100% by volume, and an aqueous pH adjuster solution, and includes at least the following steps 1 to 3: Step 1: Reducing the flow diameters of the aqueous and oil phases flowing through the system, and then merging and continuing to flow them together; Step 2: Merging the aqueous and oil phases with the aqueous pH adjuster solution and continuing to flow them together; Step 3: Separating the three liquids (the combined liquid) after the extraction of the target metal ions reaches extraction equilibrium.

[0042] The extraction method of the present invention, which includes steps 1 to 3 described above, can transfer (extract) specific metal ions coordinated with an acidic extractant from the aqueous phase to the oil phase in a high extraction amount, maintaining a high extraction rate even after multiple extraction and separation cycles, and maintaining high extraction resolution even under low-temperature conditions. In the extraction method of the present invention, if the aqueous phase contains only one type of metal ion, the metal ion extracted into the oil phase is this metal ion. On the other hand, if the aqueous phase contains multiple types of metal ions, the metal ions extracted into the oil phase are ideally one specific metal ion, but may be two or more metal ions, or may be all of the metal ions. However, the metal ion extracted into the oil phase with a high extraction amount, high extraction rate, and high extraction resolution (also referred to in the present invention as the metal ion to be extracted) is at least one type (not all types, but some types) of the multiple types of metal ions (group). For example, two or more different metal ions of valuable metal elements, specifically two or more metal ions belonging to Groups 1 to 14 of the periodic table (preferably Groups 4 to 12, more preferably Groups 9 to 12, and even more preferably Groups 8 to 11 of the periodic table), desirably one metal ion of cobalt ion and nickel ion, which are different metal ions of the same period, or one metal ion of manganese, cobalt ion, and nickel ion, which are different metal ions of the same period, can be extracted into the oil phase with a high extraction amount, high extraction rate, and high extraction resolution.

[0043] The extraction method of the present invention has been developed based on the discovery of the characteristic and function that, although two or more metal ions among a plurality of metal ions (groups) present in an aqueous phase can be extracted together into an oil phase, one of the metal ions can be extracted with a high extraction amount, high extraction rate, and high extraction resolution. In particular, the method can be applied to a new application of separating and recovering two or more metal ions, particularly different-group metal ions. Since different-group metal ions of the same period usually have similar physical and chemical behaviors, it is not easy to separate and recover one of them with a high recovery amount, high extraction rate, and high extraction resolution. However, the extraction method of the present invention can extract both different-group metal ions of the same period that have similar physical and chemical behaviors, particularly Group 9 metal ions (particularly cobalt ions) and Group 10 metal ions (particularly nickel ions), which are in demand due to the recent rapid spread of lithium-ion batteries, while recovering one of the metal ions with a high extraction amount, high extraction rate, and high extraction resolution. Similarly, for metal ions belonging to Group 7 (particularly manganese ions) and metal ions belonging to Group 9 (particularly cobalt ions), the present invention can extract both metal ions and recover one of the metal ions with a high extraction amount, extraction rate, and extraction resolution. Therefore, the present invention can greatly contribute to the further spread of electric vehicles and, ultimately, to the creation of a sustainable society.

[0044] In the present invention, being able to extract metal ions in a high extraction amount (also referred to as recovery amount) means that a large mass of metal ions is extracted into the oil phase per unit volume among the metal ions contained in the aqueous phase. This extraction amount is not unique, depending on the content of metal ions present in the aqueous phase, the content of the acidic extractant in the oil phase, etc. For example, for the metal ions extracted in the maximum extraction amount among the extracted metal ions (specific metal ions to be extracted), the content (concentration) of the metal ions in the oil phase under the conditions of the examples described below (when using metal ion-containing aqueous solution W3 or W4) is 25,000 ppm or more, preferably 30,000 ppm or more. The upper limit is not particularly limited, but is, for example, 50,000 ppm or less, and is 36,000 ppm under the conditions of the above examples described below. The extraction rate at this time is not particularly limited, but is preferably, for example, 70% or more.

[0045] Furthermore, in the present invention, "being able to extract metal ions at a high extraction rate" means that, for the metal ions extracted in the maximum amount in the initial extraction / separation cycle (steps 1 to 3), the ratio of the amount of the metal ions extracted into the oil phase to the content of the metal ions in the aqueous phase (before extraction) [(amount of metal ions extracted into the oil phase) / (content of the metal ions in the aqueous phase)] is preferably 90% or more under the conditions described in the Examples below (when 20 cycles are performed using metal ion-containing aqueous solution W1 or W2). This ratio (extraction rate) is more preferably 95% or more, and even more preferably 98% or more. The upper limit is not particularly limited, and ideally is the total amount of the metal ions present in the aqueous phase (100%). For example, it is preferably 99% or less, and can also be 95% or less. In the extraction method of the present invention, when a series of extraction / separation cycles comprising steps 1 to 3 is performed multiple times, the extraction rate in multiple cycles is maintained without a significant decrease from the extraction rate in the initial cycle. For example, under the conditions of the examples described below (when using metal ion-containing aqueous solution W1 or W2), the extraction rate (the above ratio) after multiple cycles is preferably 85% or higher, more preferably 90% or higher, and even more preferably 95% or higher, while maintaining the high extraction rate of the first extraction / separation cycle. The upper limit is ideally the total amount (100%), but can be, for example, 98% or lower. In the extraction method of the present invention, when multiple cycles of the series of extraction / separation cycles comprising steps 1 to 3 are performed, the difference between the extraction rate in the first extraction / separation cycle and the extraction rates in multiple extraction / separation cycles [(extraction rate in the first extraction / separation cycle) - (difference between extraction rates in multiple extraction / separation cycles)] serves as an index for evaluating durability, and is preferably 12% or lower, more preferably 8% or lower, and even more preferably 4% or lower. The lower limit is ideally 0%, but can be, for example, 1%.

[0046] Furthermore, in the present invention, "being able to extract metal ions with high extraction resolution (high selectivity)" means that only one specific metal ion can be selectively extracted from the metal ions present in the aqueous phase. Furthermore, when two or more types of metal ions are extracted into the oil phase, "being able to extract metal ions with high selectivity" means that, among the two or more types of metal ions extracted, the ratio of the specific metal ion (usually one type) to the total amount of other metal ions extracted [(amount of specific metal ion extracted) / (total amount of other metal ions extracted)] can be extracted and separated from other metal ions at room temperature under the conditions described in the examples below (when using metal ion-containing aqueous solution W1 or W2) at a ratio of 2.0 or more. This ratio (selectivity ratio) is preferably 4.0 or more, more preferably 5.0 or more, and even more preferably 6.0 or more. The upper limit is not particularly limited, but can be, for example, 20. In the present invention, maintaining a high extraction resolution even under low-temperature conditions means maintaining the above-mentioned high extraction resolution achieved under room temperature conditions. For example, at a temperature of 5°C, under the conditions of the examples described below (when using metal ion-containing aqueous solution W1 or W2), the ratio [(amount of specific metal ion extracted) / (total amount of other metal ions extracted)] is preferably 2.0 or more, more preferably 3.0 or more, and even more preferably 4.0 or more. The upper limit is not particularly limited, but can be, for example, 20 or less, for example, 15 or less. In the present invention, room temperature refers to a temperature in a room temperature environment, specifically, a temperature range of 15 to 60°C, with a temperature range of 20 to 30°C being common. Low-temperature conditions are not particularly limited, but refer to, for example, a temperature lower than 15°C. Considering the actual implementation environment, specifically, 0 to 10°C is preferable, and 5 to 10°C is more preferable.

[0047] The extraction method of the present invention can be suitably carried out using the extraction apparatus suitable for the present invention described above. The extraction method of the present invention will be specifically described below with reference to the extraction apparatus 1 shown in Figure 1. <Step 1> In the extraction method of the present invention, the following step 1 is carried out using the prepared aqueous phase, oil phase, and pH adjuster aqueous solution. Step 1: A step of reducing the flow diameters of the flowing aqueous phase and oil phase, allowing them to merge and continue to flow.

[0048] In step 1, when an extraction apparatus 1 is used, the aqueous phase or oil phase is transferred and circulated from an aqueous phase tank and an oil phase tank (not shown) to an aqueous phase flow pipe 11 and an oil phase flow pipe 12 using a transfer mechanism, for example, various pumps. In step 1, the conditions for transferring the aqueous phase and the oil phase and the conditions for mixing the two phases can be set as appropriate, and for example, it is preferable to set the following conditions. For each condition, it is preferable that at least one of the aqueous phase and the oil phase satisfy the following preferred ranges, etc., and it is more preferable that both satisfy the following preferred ranges, etc., in terms of the amount of metal ion extracted, durability, and extraction resolution. For each condition, when both the aqueous phase and the oil phase satisfy the following preferred ranges, etc., the conditions for the aqueous phase and the oil phase may be the same or different.

[0049] In step 1, the flow rate of the aqueous phase cannot be uniquely determined depending on the internal pressure, the inner diameter of the aqueous phase flow pipe 11, the ratio of the inner diameters (inner diameter of the open end of the tapered portion / inner diameter of the connection portion of the flow pipe with the constant inner diameter tapered portion), etc., but can be, for example, 1.0 to 20.0 mL / min, with 3.0 to 15.0 mL / min being preferred in terms of improving the mixing state, and 5.0 to 13.0 mL / min being more preferred in terms of achieving a high level of metal ion extraction amount, durability, and extraction resolution, and 6.0 to 12.0 mL / min being even more preferred. Similarly, the internal pressure (flow pressure) of the aqueous phase cannot be uniquely determined, but can be, for example, 0.01 to 5.0 MPa, with 0.03 to 2.5 MPa being preferred in terms of improving the mixing state. The flow rate of the oil phase cannot be uniquely determined depending on the internal pressure, the internal diameter of the oil phase flow pipe 12, the ratio of the internal diameters, etc., but can be, for example, 1.0 to 20.0 mL / min, with 3.0 to 15.0 mL / min being preferred in terms of improving the mixed state, and 5.0 to 13.0 mL / min being more preferred in terms of achieving a high level of metal ion extraction amount, durability, and extraction resolution, with 6.0 to 12.0 mL / min being even more preferred. Similarly, the internal pressure (flow pressure) of the oil phase cannot be uniquely determined, but can be, for example, 0.01 to 5.0 MPa, with 0.03 to 2.5 MPa being preferred in terms of improving the mixed state.

[0050] The flow rates of the aqueous phase and the oil phase per unit time can be appropriately determined by factors such as the inner diameter of each flow tube and the ratio of the metal ion content to the acidic extractant content. The flow rates per unit time can be set to different or equal amounts. In the extraction method of the present invention, regardless of the flow rates per unit time, the ratio (molar) of the metal ion content to the acidic extractant content at the time of mixing the aqueous phase and the oil phase [content (molar) of acidic extractant / total content (molar) of metal ions contained in the aqueous phase] is preferably 0.5 to 20.0 times, and more preferably 1.0 to 10.0 times. Furthermore, the content of the acidic extractant (also referred to as the mixed amount) relative to the total content of metal ions that can be coordinated by the acidic extractant [molar number of acidic extractant / total moles of metal ions that can be coordinated by the acidic extractant] can be, for example, 1.0 to 10.0 times, and preferably 1.0 to 7.0 times. Here, the metal ions to which the acidic extractant can be coordinated refer to metal ions that can be extracted into the oil phase by coordination with the acidic extractant.

[0051] As described above, the flow diameters of the aqueous phase flowing through the aqueous phase flow pipe 11 and the oil phase flowing through the oil phase flow pipe 12, i.e., the inner diameters of the respective flow pipes, are reduced, and the aqueous phase and the oil phase are then introduced into the confluence 13 to be merged. At this time, the reduction ratio of the flow diameters of the two phases (the ratio of the inner diameters) is not uniquely determined by the flow speed, internal pressure, etc., but is preferably 0.8 or less for the inner diameters and flow speeds of the respective flow pipes. The reduction ratio of the flow diameters of the two phases is more preferably 0.6 or less, and even more preferably 0.55 or less, from the viewpoint of improving the mixing state, specifically, from the viewpoint of maintaining rapid phase separation (also referred to as phase separation or liquid separation) of the two phases after mixing while balancing the amount of metal ion extraction, durability, and extraction resolution at high levels. The lower limit of the reduction ratio is not particularly limited, and can be 0.1 or more from the viewpoint of suppressing excessive internal pressure load and providing excellent workability, etc., and is preferably 0.2 or more, and more preferably 0.3 or more, from the viewpoint of improving the above-mentioned mixed state. The distance between the end opening of the aqueous phase flow pipe 11 and the end opening of the oil phase flow pipe 12 (the length of the confluence part 13 (collision region)) is appropriately determined taking into consideration the mixed state (collision force) of the aqueous phase and the oil phase, etc., and can be, for example, 1 to 100 mm.

[0052] In the present invention, the flow conditions and joining conditions of the aqueous phase and the oil phase can be appropriately selected from the conditions described above. However, as the conditions for each phase at the time of joining (when the two phases collide), the kinetic energy per unit area and per unit time (sometimes simply referred to as "kinetic energy" in the present invention) E ＳＴ In the present invention, it is preferable to set the kinetic energy E per unit area and unit time to be 1 / 2 or less, since this can improve the amount of extracted metal ions, durability, and extraction resolution in a well-balanced manner. ＳＴ (J / sec / m ２ ) is calculated from the density of the fluid (water phase and oil phase), the linear velocity and volume flow rate at the confluence 13 (the end opening of each flow pipe), and the cross-sectional area by the following formula (E ＳＴ ) can be calculated using the formula (E ＳＴ ) E ＳＴ = (1 / 2) × ρ × u ２× Q × (1 / A) formula (E ＳＴ ) where ρ is the density of the fluid being circulated (kg / m ３ ), u is the linear velocity (m / sec) of the fluids to be circulated when they join (when they flow into the junction 13), and Q is the volumetric flow rate (m ３ / sec), and A is the cross-sectional area (m ２ ) where the density of the fluid is ρ (kg / m ３ ) is calculated by measuring the mass W (g) of the fluid used to measure the fluid to be measured in a 100 mL measuring flask, and then multiplying it by (W / 100) x 1000 (kg / m ３ The linear velocity u (m / sec) of the fluid is calculated by multiplying the flow rate of the fluid (mL / min) by 60×10 －６ × 1 / A (m -２ In the present invention, the linear velocity of each of the aqueous phase and the oil phase is not particularly limited, and is preferably, for example, 0.01 to 2.0 m / sec, and more preferably 0.05 to 1.0 m / sec. The volumetric flow rate Q (m ３ / sec) can be converted from the flow rate (mL / min).

[0053] In the present invention, the kinetic energy E ＳＴ When the kinetic energy E is increased, the mixing state due to collision between the aqueous phase and the oil phase increases, which tends to decrease the phase separation property, but the amount of metal ions extracted, durability, and extraction resolution (particularly room temperature resolution) can be improved. ＳＴ can be appropriately set in consideration of the above-mentioned flow conditions and joining conditions of the aqueous phase and the oil phase. ＳＴ As for the energy density, it is preferable that the energy density is 10 J / sec / m because it can increase the interfacial area between the water phase and the oil phase, thereby increasing the amount of metal ions extracted, durability, and extraction resolution. ２ It is preferable to set it to 50 J / sec / m or more. ２ More preferably, it is 200 J / sec / m or more. ２ More preferably, it is 500 J / sec / m or more. ２On the other hand, it is particularly preferable that the kinetic energy E ＳＴ As a result, it is possible to improve the phase separation property, and it is 100,000 J / sec / m ２ It is preferable that the energy density is 16,000 J / sec / m or less, and that the amount of metal ions extracted, durability, and extraction resolution can be improved while maintaining high phase separation. ２ More preferably, it is 10,000 J / sec / m or less. ２ More preferably, it is 5000 J / sec / m or less. ２ It is particularly preferable to set it to 100 J / sec / m or less. ２ Most preferably, the following is true:

[0054] In the present invention, the conditions for carrying out step 1 can be appropriately selected from the above-mentioned conditions, and can be set by appropriately combining the above-mentioned conditions. In the present invention, the conditions for carrying out step 1 can be selected from the above-mentioned conditions in terms of improving the amount of extracted metal ions, durability, and extraction resolution, and the conditions for carrying out step 1 can be selected from the above-mentioned conditions in terms of the flow rate, the reduction ratio of the flow diameter (ratio of inner diameters), and the kinetic energy E ＳＴ It is preferable to set at least one of the above, and it is more preferable to set the flow velocity and the flow diameter reduction ratio in combination within any of the above ranges in order to achieve a high level of balance between the amount of extraction of metal ions, durability, and extraction resolution, and it is more preferable to set the flow velocity, the flow diameter reduction ratio, and the kinetic energy E ＳＴ For example, it is more preferable to set the flow rate in the range of 3.0 to 15.0 mL / min, the flow diameter reduction ratio in the range of 0.2 to 0.6, and the kinetic energy E ＳＴ 50 to 100,000 J / sec / m ２In one preferred embodiment, the respective conditions are set within the ranges shown in the table. In this embodiment, the combined conditions may also be within the preferred ranges described above. In this embodiment, conditions other than these conditions may be combined. For example, it is also preferred to combine the above ratio (moles) [content (moles) of acidic extractant / total content (moles) of metal ions contained in the aqueous phase] and / or the content [number of moles of acidic extractant / total number of moles of metal ions that can be coordinated by the acidic extractant].

[0055] In the present invention, the flow diameter, the inner diameter of a flow pipe, the opening diameter of a tapered portion, etc. are referred to as "equivalent diameters." "Equivalent diameter" is also called 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 pipe internal cross-sectional shape, the diameter of the pipe internal cross section of the equivalent circular pipe is called the equivalent diameter. The equivalent diameter (deq) is defined as deq = 4A / p, where A is the pipe internal cross-sectional area and p is the pipe wetted edge length (inner circumference). When applied to a circular pipe, this equivalent diameter coincides with the diameter of the pipe internal cross section. The equivalent diameter is used to estimate the flow or heat transfer characteristics of the pipe based on data on the equivalent circular pipe, and represents the spatial scale (representative length) of the phenomenon. For a regular square pipe with an internal cross section of side a, the equivalent diameter is deq = 4a ２ / 4a = a, and for an equilateral triangle tube with one side a, deq = a / 3 １／２ In the case of a flow between parallel plates with a flow path height h, deq=2h (see, for example, "Mechanical Engineering Dictionary," edited by the Japan Society of Mechanical Engineers, 1997, Maruzen Co., Ltd.).

[0056] In step 1, the confluence angle of the aqueous phase and oil phase is not particularly limited. In the extraction apparatus 1, the confluence angle is 180° (opposite), but in the present invention, the confluence angle can be 0 to 180°. In terms of improving the mixed state, the confluence angle is preferably 30 to 180°, more preferably 90 to 180°, and even more preferably 150 to 180°. In step 1, the flowing aqueous phase and flowing oil phase are confluent and mixed in the confluence section 13 as described above, preferably by colliding the two phases to be confluent and mixed, and then transferred to the mixing section 14, where they continue to flow through the internal passage of the mixing section 14.

[0057] In addition, when the content of the acidic extractant in the oil phase used in step 1 is 35 to 100% by volume, there is no need to adjust the content. However, when the content is less than 35% by volume, an acidic extractant is added to adjust the content to 35 to 100% by volume.

[0058] <Step 2> In the extraction method of the present invention, the following step 2 is carried out. The following step 2 may be carried out after step 1 or together with step 1. Step 2: A step of combining the aqueous phase, the oil phase, and the aqueous pH adjuster solution and further passing them through the mixture.

[0059] In step 2, when the extraction apparatus 1 is used, a pH adjuster aqueous solution is transferred from a pH adjuster aqueous solution tank (not shown) to a pH adjuster transfer pipe 15 using a transfer mechanism, such as various pumps, and then transferred to the mixing section 14. The amount of pH adjuster aqueous solution flowing at this time is set to an amount that will result in a predetermined pH value for the three-liquid combined solution mixed in the mixing section 14. The pH to be set is not unique and is determined appropriately taking into consideration the pKa of the acidic extractant, the complex formation constant between the acidic extractant and the metal ion, the coordination number of the metal ion, and the like. The pH of the three-liquid combined solution (the aqueous phase therein) can be 0.01 to 14. For example, in terms of extraction amount, durability, and extraction resolution, 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. The flow rate of the aqueous pH adjuster solution cannot be uniquely determined, but can be set to, for example, 0.05 to 10.0 mL / min, depending on factors such as the internal pressure of the pH adjuster transfer pipe, the internal diameter of the pH adjuster transfer pipe 15, and the internal pressure of the mixed solution flowing through the mixing section 14. Similarly, the internal pressure (flow pressure) of the aqueous pH adjuster solution cannot be uniquely determined, and is set to a pressure that allows transport into the mixing section 14.

[0060] As described above, in the further flowing step 2, the two-liquid combined liquid (also referred to as the oil-water combined liquid) of the aqueous phase and the oil phase combined in the subsequent flowing step 1 is combined with the aqueous pH adjuster solution and further flowed. Specifically, when the extraction apparatus 1 is used in the extraction method of the present invention, the aqueous pH adjuster solution flowing through the pH adjuster transfer pipe 15 is transferred into the mixing section 14, and the oil and aqueous phases (two-liquid mixed liquid) flowing through the subsequent mixing section 14b are combined with the aqueous pH adjuster solution and mixed. This results in a three-liquid combined liquid (also referred to as the adjuster combined liquid) consisting of both phases and the aqueous pH adjuster solution, the pH of which can be adjusted to the predetermined value. The three-liquid combined liquid is then further flowed through the subsequent mixing section 14b and transferred to the separation section 16.

[0061] In the extraction method of the present invention, when the extraction apparatus 2 is used, step 2 is carried out in step 1. Specifically, in step 1 using the extraction apparatus 1, the aqueous pH adjuster solution is directly led to the confluence 23 from the pH adjuster transfer pipe 15 connected to the confluence 23, and the three liquids flowing through the confluence 23, i.e., the aqueous phase, the oil phase, and the aqueous pH adjuster solution, are merged. The flow conditions, etc. at this time can be set to the same as those in the method using the extraction apparatus 1. In this way, step 2 is further carried out in step 1, and the aqueous pH adjuster solution is merged all at once and further flowed. 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 aqueous pH adjuster solution flowing through the pH adjuster transfer pipe 15 are transferred to the confluence 23, and the three liquids are mixed (by colliding) in the mixing section 23 to produce a three-liquid merged liquid whose pH has been adjusted to the predetermined value. Thereafter, the three-liquid confluence liquid is further passed through the mixing section 24 and transferred to the separation section 16 .

[0062] In the present invention, the three-liquid combined liquid is phase-separated into an aqueous phase and an oil phase in step 3 described below. The point at which extraction equilibrium is reached may be before phase separation, or after transfer to the separation section 16 of the extraction apparatuses 1 and 2. In order to achieve even higher levels of extraction yield, durability, and extraction resolution, it is preferable that the extraction of the target metal ions from the three-liquid combined liquid reaches extraction equilibrium during flow in step 1 or step 2 (until introduction into separation section 16). Specifically, it is preferable that the extraction of the target metal ions reaches extraction equilibrium while the three-liquid combined liquid is flowing through the downstream mixing section 14b of the mixing section 14 or the mixing section 24. In the present invention, the aqueous phase and the oil phase are merged after reducing the flow diameter, thereby improving the mixing state even at the time of merging and enabling the extraction of metal ions. Since the two phases continue to mix during subsequent flow (after pH adjustment), it is believed that metal ion extraction is promoted during flow through the mixing section 14 or 24, resulting in a rapid reach of extraction equilibrium. In the present invention, whether the extraction of the target metal ions has reached extraction equilibrium can be confirmed or identified by various methods. For example, this can be confirmed or identified by the fact that the pH of the three-liquid combined liquid after pH adjustment with a pH adjuster (flowing through the downstream mixing section 14b or the mixing section 24) remains constant, or by the content (residual amount) of the target metal ions in the aqueous phase sampled from the three-liquid combined liquid remaining constant. In the present invention, in order to ensure that the extraction of the target metal ions reaches extraction equilibrium while the three-liquid combined liquid is flowing through the downstream mixing section 14b or the mixing section 24, the above confirmation and identification method can be performed on the three-liquid combined liquid in advance, and the flow time (flow path length) of the downstream mixing section 14b or the mixing section 24 can be determined based on the results obtained. The time required for the extraction of the target metal ions to reach extraction equilibrium cannot be uniquely determined depending on the content of metal ions in the aqueous phase, the type of acidic extractant, the temperature, etc., but can be, for example, 1 minute to 24 hours, preferably 1 to 60 minutes, as the elapsed time after mixing the aqueous phase and the oil phase.

[0063] In at least one of steps 1 and 2, it is preferable to circulate the merged liquid (merged liquid) through a flow path equipped with a static mixer, since this highly improves the mixed state of the merged liquid and further enhances resolution (including low-temperature resolution). When using the extraction device 1, a static mixer can be installed in the flow path of at least one of the front-stage mixing section 14a and the rear-stage mixing section 14b in the mixing section 14, and it is more preferable to install a static mixer in the flow path of the rear-stage mixing section 14b, since this further improves the mixed state of the three-liquid merged liquid. When using the extraction device 2, a static mixer is installed in the flow path of the mixing section 24.

[0064] <Step 3> In the extraction method of the present invention, the following Step 3 is then carried out. Step 3: A step of separating the three-liquid merged liquid into an aqueous phase and an oil phase (phase separation) after the extraction of the target metal ions reaches extraction equilibrium.

[0065] The separation method in step 3 is not particularly limited, and known separation methods such as a static standing method or a centrifugation method can be applied. The static standing method is preferred because it requires a simple apparatus configuration and is easy to work with. The phase separation conditions are not particularly limited and can be set appropriately as long as the conditions allow the three-liquid merged liquid to separate into an aqueous phase and an oil phase. The static standing time in the static standing method is typically 10 minutes to 24 hours after transfer to the separation section 16. In the extraction method of the present invention, since phase separation after mixing proceeds quickly, the static standing time can be set to a short time, preferably 10 to 60 minutes, for example.

[0066] In the extraction method of the present invention, the temperature at which each of the above steps 1 to 3 is performed is not particularly limited and may be room temperature or a low temperature. Since the extraction method of the present invention can achieve high low-temperature resolution, it can also be applied to low-temperature environments. Room temperature and low temperature are as described above.

[0067] In the extraction method of the present invention, by carrying out the above steps 1 to 3, metal ions present in the aqueous phase that are coordinately bonded to an acidic extractant can be extracted into the oil phase. The number of types of metal ions extracted into the oil phase is ideally one, but can be two or more, and in this case, can be, for example, 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 the multiple types of metal ions are not particularly limited, but are preferably the same as the two or more types (combination) of heterogeneous metal ions contained in the aqueous phase described above.

[0068] <Multi-cycle extraction method of the present invention> As described above, the extraction method of the present invention can suppress deterioration and decomposition of the acidic extractant. As a result, even when the series of extraction and separation cycles comprising steps 1 to 3 described above are performed multiple times using a used oil phase, high extraction yield, high durability, and high extraction and resolution properties can be maintained. Therefore, the series of extraction and separation cycles comprising steps 1 to 3 described above can be performed multiple times while reusing the oil phase. The extraction method of the present invention, which performs a series of extraction and separation cycles multiple times (sometimes referred to as the multi-cycle extraction method of the present invention), can perform the extraction and separation cycles including steps 1 to 3 as long as the extraction yield, durability, and extraction and resolution properties of the acidic extractant in the oil phase 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 is reused as the oil phase for the next extraction and separation cycle, after stripping metal ions and adjusting the content of the acidic extractant, as necessary. The multi-cycle extraction method of the present invention can further reduce extraction costs. The oil phase (used oil phase) obtained in step 3 is usually used after back-extraction of 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 of extraction, etc. As a method for back-extracting (isolating) metal ions from the oil phase, any known method can be applied without particular limitation. For example, back-extraction can be performed by acidifying the liquid phase, for example, to a pH of 4 or less, using an inorganic acid such as sulfuric acid, hydrochloric acid, or nitric acid. This back-extraction method may be a batch method, but a flow method is preferred in order not to impair the advantages of the extraction method of the present invention. The back-extraction apparatus used in the flow-type back-extraction method is not particularly limited, but an extraction apparatus suitable for the present invention can be used from the viewpoints of workability, cost reduction, etc. The multi-cycle extraction apparatus suitable for use in the multi-cycle extraction method of the present invention is not particularly limited, but examples thereof include an apparatus in which the oil phase discharge pipe 16a connected to the separation section 16 in the above-mentioned extraction apparatuses 1 and 2 is connected to an oil phase tank (not shown in FIGS. 1 and 2 ) or to the middle of the part of the oil phase tank and the oil phase flow pipe 12 that joins the oil phase tank, via a device that back-extracts metal ions in the oil phase.

[0069] <Other Steps> The extraction method of the present invention may include steps other than steps 1 to 3 described above. Examples include a step of stripping (isolating) metal ions from the oil phase separated in step 3 (a step of stripping metal ions from the oil phase and recycling the oil phase), a step of recovering the stripped metal ions as a compound (salt), a step of purifying the stripped metal ions or their compounds, a step of purifying the acidic extractant recovered from the oil phase, and a step of previously removing ions of metal elements belonging to Group 1 or Group 2 of the periodic table from the aqueous phase. Known methods can be applied as a method for recovering the stripped metal ions as a compound without any particular limitation.

[0070] Although the extraction method of the present invention is a simple method using the above-mentioned flow-type mixing method, it can extract metal ions from an aqueous phase into an oil phase while maintaining a high extraction yield in a single extraction / separation cycle, maintaining a high extraction rate even after multiple extraction / separation cycles, and maintaining a high extraction resolution even under low-temperature conditions. In particular, when multiple types of metal ions are contained in the aqueous phase, a specific metal ion can be extracted into the oil phase while maintaining a high extraction yield in a single extraction operation, maintaining a high extraction rate even after multiple extraction operations, and maintaining a high extraction resolution even under low-temperature conditions. 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. 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 acidic extractant, or the like. For example, when extracting metal ions belonging to Group 9 and metal ions belonging to Group 10 into an oil phase, the metal ions belonging to Group 9 can be separated and recovered with a high extraction amount, high extraction rate, and high extraction resolution (including low-temperature resolution). In particular, when extracting Co ions as the metal ions belonging to Group 9 and Ni ions as the metal ions belonging to Group 10, the Co ions can be separated and recovered with a high extraction amount, high extraction rate, and high extraction resolution. Furthermore, when extracting metal ions belonging to Group 7 and metal ions belonging to Group 9 into an oil phase, the metal ions belonging to Group 7 can be separated and recovered with a high extraction amount, high extraction rate, and high extraction resolution (including low-temperature resolution). In particular, when extracting Mn ions as the metal ions belonging to Group 7 and Co ions as the metal ions belonging to Group 9, the Mn ions can be separated and recovered with a high extraction amount, high extraction rate, and high extraction resolution. Furthermore, when extracting metal ions belonging to Group 9 and metal ions belonging to Group 11 into an oil phase, the metal ions belonging to Group 11 can be separated and recovered with a high extraction amount, high extraction rate, and high extraction resolution. Furthermore, when metal ions belonging to Group 9, metal ions belonging to Group 10, and metal ions belonging to Group 12 are extracted into an oil phase, the metal ions belonging to Group 10 are usually not extracted, but the metal ions belonging to Group 12 can be separated and recovered with a high extraction amount, high extraction rate, and high extraction resolution.

[0071] As described above, the extraction method of the present invention can extract and recover specific metal ions present in the aqueous phase into the oil phase with a high extraction amount, high extraction rate, and high extraction resolution. In particular, the extraction method of the present invention can extract two or more metal ions present in the aqueous phase while recovering one of the metal ions with a high extraction amount, high extraction rate, and high extraction resolution. Therefore, by subjecting the aqueous phase containing two or more metal ions stripped from the oil phase to the extraction method of the present invention, the selectivity for one metal ion can be further increased regardless of the operating temperature without significantly impairing the recovery amount (recovery rate), and as a result, high-purity metal ions can be recovered with a high recovery amount (recovery rate).

[0072] <Acidic Extractant> The acidic extractant used in the extraction method of the present invention may be any metal extractant consisting of an acidic compound having at least one active hydrogen atom, and examples thereof include various known acidic extractants and phosphoric acid compounds represented by the following formula (I). Examples of active hydrogen atoms include active hydrogen atoms in hydroxy groups (including phenolic hydroxy groups and hydroxy groups bonded to phosphorus or sulfur atoms), carboxy groups, and sulfanyl groups. The acidic extractant exhibits acidity, and its pKa is not particularly limited and can take any appropriate value, preferably 0.1 to 12. The pKa can be measured by neutralization titration.

[0073] Examples of various known acidic extractants include phosphoric acid compounds, carboxylic acid compounds, sulfonic acid compounds, oxime compounds, β-diketone compounds, oxine compounds, etc. Examples of phosphoric acid compounds include phosphoric acid compounds, phosphonic acid compounds, phosphinic acid compounds, and further compounds in which the oxygen atom of these compounds is replaced with a sulfur atom, such as the various compounds described in paragraph 0046 of Patent Document 1, and examples of carboxylic acid compounds include compound VA-10 used in the examples described below.

[0074] The acidic extractant used in the extraction method of the present invention is preferably a compound represented by the following formula (I), in that it can balance the extraction amount, durability, and extraction resolution at a high level. Compounds represented by the following formula (I) include compounds having a phosphate group, a phosphonate group, a phosphinate group, and also compounds having an acid group in which at least one oxygen atom of these acid groups is replaced with a sulfur atom or a nitrogen atom. For example, a phosphate ester compound (R １ OP(=O)(O)-OR ２ ), phosphonate ester compounds (R １ -P(=O)(O)-OR ２ , R １ OP(=O)(O)-R ２ ) or phosphinic acid compounds (R １ -P(=O)(O)-R ２ ), thiophosphoric acid compounds in which at least one oxygen atom in each of the above phosphoric acid compounds is converted to a sulfur atom, and further compounds in which the oxygen atom (—O—) bonded to P is replaced with a nitrogen atom. The acidic extractant represented by formula (I) is preferably a phosphoric acid compound, more preferably a phosphoric acid ester compound, a phosphonic acid ester compound, or a phosphinic acid ester compound, even more preferably a phosphonic acid ester compound, and particularly preferably a phosphonic acid monoester compound, in that it can balance the extraction amount, durability, and extraction resolution at an even higher level.

[0075] In formula (I), R １ and R ２ Each represents a substituent. １ and R ２ At least one of the substituents in R is a hydrocarbon group having 9 or more carbon atoms. １ and R ２ The substituents that can be taken as R are not particularly limited, and include various substituents and groups that combine substituents. In the present invention, the above-mentioned "various substituents" do not represent R alone. １ and R ２The above "groups with a combination of substituents" refers to substituents formed by combining multiple substituents. In order to clearly distinguish between the above "various substituents" and the above "groups with a combination of substituents," for convenience, the above "various substituents" are sometimes referred to as "single substituents," and the above "groups with a combination of substituents" are sometimes referred to as "composite substituents." A composite substituent is formed by combining multiple single substituents, usually by removing hydrogen atoms from a required number of single substituents among the single substituents that constitute it. In a composite substituent, the position at which a specific substituent is substituted with another substituent is not particularly limited and can be determined appropriately. For example, when a phenyl group is substituted with another substituent, the substitution position may be any of the 2nd to 4th positions relative to the bonding position of the phenyl group. In the present invention, R １ and R ２ Substituents that can be used as a group are interpreted as single substituents whenever possible. For example, a 2-ethylhexyl group can be interpreted as a compound substituent in which an ethyl group substitutes for a hexyl group, but it is interpreted as a branched alkyl group. Furthermore, a hexyloxy group can be interpreted as a compound substituent combining a hexyl group and an oxygen atom, but it is interpreted as an alkoxy group.

[0076] R １ and R ２ The substituents (including single substituents and composite substituents) that can be taken as R may be hydrocarbon groups composed only of carbon atoms and hydrogen atoms, or may be heteroatom-containing substituents containing at least one heteroatom such as a nitrogen atom, an oxygen atom, or a sulfur atom. １ and R ２It is preferable that all of the substituents that can be used as the heteroatom are hydrocarbon groups, as this allows for a better balance between the extraction amount, durability, and extraction resolution at even higher levels. The heteroatom-containing substituent preferably contains an oxygen atom or a sulfur atom as the heteroatom, and preferably contains an oxygen atom. The number of heteroatoms contained in the heteroatom-containing substituent is not particularly limited and can be 1 to 4, preferably 1. In the heteroatom-containing substituent, the heteroatom may be present in any of the substituents, for example, inside or at the end of the atomic chain constituting the substituent. The heteroatom-containing substituent is not particularly limited, and examples include composite substituents such as groups combining a single substituent such as an alkoxy group, an aryloxy group, a heterocyclic oxy group, an alkylthio group, an arylthio group, or a heterocyclic thio group with an aryl group (substituents containing a ring structure), as described below.

[0077] R １ and R ２ The single substituent that can be taken as is not particularly limited and includes appropriate substituents, for example, groups selected from the substituent G described below. Among these, hydrocarbon groups such as alkyl groups, alkenyl groups, alkynyl groups, and aryl groups, heterocyclic groups, etc. are preferred, and alkyl groups are more preferred in that they can achieve a good balance between the extraction amount, durability, and extraction resolution at an even higher level.

[0078] The alkyl group, alkenyl group, and alkynyl group that can be used as a single substituent may be any of linear, branched, and cyclic groups, but branched groups are more preferred in that they can achieve a good balance between the amount of extraction, durability, and extraction resolution at a higher level. The aryl group and heterocyclic group that can be used as a single substituent are the same as the corresponding groups in the substituent G described below.

[0079] R １ and R ２The composite substituent that can be used as the substituent is not particularly limited, and examples thereof include (single) substituents, such as groups combining multiple substituents selected from the substituent G. The number of single substituents constituting the composite substituent is not particularly limited, and can be 2 to 6, preferably 2 to 4. Examples of composite substituents include groups combining hydrocarbon groups (groups combining an alkyl group, alkenyl group, or alkynyl group with an aryl group), groups combining a hydroxyl group with an aryl group (hydroxyaryl group), groups combining an alkoxy group or alkylthio group with an aryl group, and groups combining an alkyl group, alkenyl group, or alkynyl group with an amino group. In addition, when the composite substituent contains an oxygen atom or sulfur atom bonded to the alkyl group, the oxygen atom and sulfur atom are interpreted as atoms derived from the alkoxy group or alkylthio group, respectively. For example, the composite substituent "alkyl group-oxygen atom-phenyl group-" is interpreted as a group combining an alkoxy group and a phenyl group, not as a group combining an alkyl group and a phenoxy group, nor as a group combining an alkyl group, an oxygen atom, and a phenyl group. The above interpretation is the same when the composite substituent contains an oxygen atom or the like bonded to an alkenyl group or an alkynyl group.

[0080] As the composite substituent, those containing a ring structure are preferred in terms of extraction amount, durability and extraction resolution. The ring structure contained in the composite substituent is not particularly limited, and examples thereof 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 in terms of extraction amount, durability and extraction resolution, ring structures derived from aryl groups are more preferred. Specific examples of the composite substituent containing a ring structure include groups combining an alkyl group and an aryl group, groups combining an alkoxy group or an alkylthio group and an aryl group, etc., with alkoxyaryl groups being more preferred, and alkoxyphenyl groups being even more preferred.

[0081] R １ and R ２Among the above-mentioned substituents, preferred are alkyl groups, or composite substituents containing a ring structure combining an alkoxy group or an alkylthio group with an aryl group, in terms of the extraction amount, durability, and extraction resolution. Of the preferred substituents, the alkoxy group, alkylthio group, and composite substituents containing a ring structure preferably have 9 or more carbon atoms.

[0082] R １ The substituents that can be used as R ２ The combination of substituents that can be taken as R is not particularly limited, and １ and R ２ The above-mentioned substituents that can be taken as R can be appropriately combined. For example, the molecular structure of the substituent is not particularly limited. １ and R ２ The substituents that can be used as the branched structure are preferably combinations containing branched substituents (combinations in which at least one of the substituents has a branched structure), in that they can balance the extraction amount, durability, and extraction resolution at even higher levels. Combinations of branched substituents, and combinations of branched substituents with substituents containing a ring structure (particularly composite substituents) are more preferred. Here, the branched structure substituent is not particularly limited, but examples thereof include hydrocarbon groups such as alkyl groups, alkenyl groups, and alkynyl groups, as well as single or composite substituents containing hydrocarbon groups. Single substituents such as alkyl groups, or composite substituents such as groups combining alkoxy groups or alkylthio groups with aryl groups are preferred, and alkyl groups or groups combining alkoxy groups with aryl groups are more preferred. In the present invention, the branched structure substituent is preferably a substituent having 9 or more carbon atoms, in that it can balance the extraction amount, durability, and extraction resolution at even higher levels.

[0083] The type of the substituent is not particularly limited, but R １ and R ２As for possible combinations of substituents, in terms of extraction amount, durability, and extraction resolution, combinations of single substituents or combinations of single substituents and complex substituents are preferred. In combinations of single substituents, the same (type) of substituents may be combined, or different (types) of 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 combined single substituents may be the same or different, but it is preferable that both are branched chains. Furthermore, the number of carbon atoms of the combined single substituents may be the same or different.

[0084] On the other hand, examples of combinations of different substituents include combinations in which one of the substituents is a hydrocarbon group, and more preferred are combinations of two of alkyl groups, alkenyl groups, and alkynyl groups. In the combinations of different substituents, the carbon chains of the alkyl groups, alkenyl groups, and alkynyl groups may be the same or different, but it is preferable that all of them are branched chains. In addition, the number of carbon atoms in the alkyl groups, alkenyl groups, and alkynyl groups may be the same or different.

[0085] As a combination of a single substituent and a composite substituent, a combination of an alkyl group, an alkenyl group, or an alkynyl group with a composite substituent containing a ring structure is preferred, and a combination of an alkyl group with an alkoxy group and an aryl group is more preferred.

[0086] R １ The substituents that can be used as R ２ Among the above-mentioned combinations, the combination of alkyl groups is particularly preferred in that it allows for a balance of the extraction amount, durability, and extraction decomposition ability at an even higher level.

[0087] In the compound represented by formula (I), R １ and R ２ The substituents that can be taken as R can be appropriately selected from the above-mentioned substituents. １ and R２ At least one of the substituents in R is a hydrocarbon group having 9 or more carbon atoms. １ and R ２ In the present invention, when at least one of the substituents is a hydrocarbon group having 9 or more carbon atoms, the extraction amount, durability, and extraction resolution can be balanced at an even higher level. １ and R ２ is a hydrocarbon group having 9 or more carbon atoms, Z １ and Z ２ Preferably, one of the carbon atoms 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 better balance between the amount of extraction, durability, and extractive resolution 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 appropriately, and can be, for example, 30 or less, preferably 24 or less, and more preferably 20 or less.

[0088] The hydrocarbon group having 9 or more carbon atoms is not particularly limited, but among the above-mentioned hydrocarbon groups, an alkyl group, an alkenyl group, or an alkynyl group is preferred, and an alkyl group is more preferred. The hydrocarbon group having 9 or more carbon atoms may be linear or branched, but a branched chain 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 it is 1 or more, and examples include an embodiment having 1 or 2, and an embodiment having 3 or more. In an embodiment having 3 or more branched carbon atoms, the number of branched carbon atoms is the same as that of a hydrocarbon group having 3 or more branched carbon atoms, as described below. As the hydrocarbon group having 9 or more carbon atoms, an alkyl group having 9 or more carbon atoms is preferred, and a branched alkyl group having 1 or more branched carbon atoms and 9 or more carbon atoms is more preferred. Examples of linear alkyl groups having 9 or more carbon atoms include an n-nonyl group, an n-decyl group, an n-dodecyl group, an n-tetradecyl group, and an n-hexadecyl group. 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, 2-decyltetradecane, etc. 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, 2-(4-methylhexyl)-8-methyldecyl, etc.

[0089] In the compound represented by formula (I), R １ and R ２ The substituents that can be used for R can be selected appropriately from the above-mentioned substituents. However, when paying attention to the molecular structure and the number of carbon atoms of the substituents, R １ and R ２ At least one of the groups is preferably a hydrocarbon group having three or more branched carbon atoms.

[0090] The hydrocarbon group having three or more branched carbon atoms is not particularly limited, but typically includes alkyl, alkenyl, or alkynyl groups having a branched structure, each of which has 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 it is three or more, and can be, for example, 3 to 8, preferably 3 to 6, and more preferably 4 to 6. The number of carbon atoms in the hydrocarbon group having three or more branched carbon atoms is not particularly limited, and is preferably 9 or more, and more preferably 12 or more. In other words, it is preferable that a hydrocarbon group having 9 or more carbon atoms has three or more branched carbon atoms. Examples of such hydrocarbon groups are as described above.

[0091] R １ and R ２ The other of R may be a hydrocarbon group having 9 or more carbon atoms, or may be a substituent other than a hydrocarbon group having 9 or more carbon atoms. In the present invention, R １ and R ２ The substituent that the other group may take is preferably a hydrocarbon group, and preferably a hydrocarbon group having 8 or less carbon atoms. Examples of hydrocarbon groups having 8 or less carbon atoms include alkyl groups, alkenyl groups, alkynyl groups, and aryl groups, with alkyl groups being preferred. The hydrocarbon group may be linear, branched, or cyclic, but a branched chain is more preferred in terms of achieving a higher level of balance between extraction amount, durability, and extraction resolution. The number of branched carbon atoms present in the branched chain may be one or more, and is preferably 1 to 5, for example, and preferably 1. The total number of carbon atoms constituting the hydrocarbon group having 8 or less carbon atoms is preferably 1 to 8, more preferably 3 to 8, and even more preferably 5 to 8.

[0092] In this embodiment, R １ The substituents that can be used as R ２The combination of the substituents that can be used as the substituent is not particularly limited, and any one of the substituents may be a hydrocarbon group having 9 or more carbon atoms. The substituent is preferably a substituent containing a hydrocarbon group having 9 or more carbon atoms and one or more branched carbon atoms, and more preferably a substituent containing a hydrocarbon group having 3 or more branched carbon atoms.

[0093] 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 represents a single bond, —O—, —NH— or —S—, and is preferably a single bond or —O—. １ and Z ２ are each preferably a single bond or —O—, and Z １ and Z ２ Among these combinations, Z is the best in terms of extraction amount, durability, and extraction resolution. １ and Z ２ It is more preferred that one of the groups is a single bond and the other is —O—.

[0094] The compound represented by formula (I) can be prepared by the reaction of R １ and R ２ and Y and X and Z １ and Z ２ In formula (I), R １ -Z １ - and R ２ -Z ２ Even when - takes the substituent -O-, the substituent -S-, or the substituent -NH- and these can be interpreted as one substituent (for example, an alkoxy group), these are not interpreted as one substituent, and -O-, -S-, or -NH- is not used in Z. １ or Z ２ and the substituent is R １ or R ２ This is interpreted as follows.

[0095] The molecular weight of the compound represented by formula (I) is not particularly limited, but can be, for example, 350 to 50,000. When the oil phase contains an organic solvent, it is preferably 400 to 10,000 in terms of solubility in the organic solvent, etc.

[0096] The compound represented by formula (I) may have a substituent, and examples of the substituent that may be had include groups selected from the substituent G described below. The compound represented by formula (I) can be synthesized by a known synthesis method, for example, by referring to the synthesis method described in the examples described below.

[0097] Specific examples of the compound represented by formula (I) include those shown below in addition to those synthesized in the examples, but the present invention is not limited to these.

[0098]

[0099] - Substituent G - an alkyl group (preferably an alkyl group having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.), an alkenyl group (preferably an alkenyl group having 2 to 20 carbon atoms, for example, vinyl, allyl, oleyl, etc.), an alkynyl group (preferably an alkynyl group having 2 to 20 carbon atoms, for example, ethynyl, butadiynyl, phenylethynyl, etc.), a cycloalkyl group (preferably a cycloalkyl group having 3 to 20 carbon atoms, for example, cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.), In the present invention, alkyl groups usually include cycloalkyl groups, but will be described separately here.), aryl groups (preferably aryl groups having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl, 4-methoxyphenyl, 2-chlorophenyl, 3-methylphenyl, etc.), aralkyl groups (preferably aralkyl groups having 7 to 23 carbon atoms, for example, benzyl, phenethyl, etc.), heterocyclic groups (preferably heterocyclic groups having 2 to 20 carbon atoms, more preferably 5- or 6-membered heterocyclic groups having at least one oxygen atom, sulfur atom, or nitrogen atom. Heterocyclic groups include aromatic heterocyclic groups and aliphatic heterocyclic groups.For example, a tetrahydropyran ring group, a tetrahydrofuran ring group, 2-pyridyl, 4-pyridyl, 2-imidazolyl, 2-benzimidazolyl, 2-thiazolyl, 2-oxazolyl, a pyrrolidone group, etc.), an alkoxy group (preferably an alkoxy group having 1 to 20 carbon atoms, for example, methoxy, ethoxy, isopropyloxy, benzyloxy, etc.), an aryloxy group (preferably an aryloxy group having 6 to 26 carbon atoms, for example, phenoxy, 1-naphthyloxy, 3-methylphenoxy, 4-methoxyphenoxy, etc.), a heterocyclic oxy group (a group in which an -O- group is bonded to the above heterocyclic group), an alkoxycarbonyl group (preferably or an alkoxycarbonyl group having 2 to 20 carbon atoms, for example, ethoxycarbonyl, 2-ethylhexyloxycarbonyl, dodecyloxycarbonyl, etc.), an aryloxycarbonyl group (preferably an aryloxycarbonyl group having 7 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl, 4-methoxyphenoxycarbonyl, etc.), a heterocyclic oxycarbonyl group (a group in which an —O—CO— group is bonded to the above heterocyclic group), an amino group (preferably an amino group having 0 to 20 carbon atoms, an alkylamino group, or an arylamino group, 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 an alkylcarbonyl group, an alkenylcarbonyl group, an alkynylcarbonyl group, an arylcarbonyl group, or a 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, and nicotinoyloxy), aryloyloxy groups (preferably aryloyloxy groups having 7 to 23 carbon atoms, for example, benzoyloxy and naphthoyloxy), carbamoyl groups (preferably carbamoyl groups having 1 to 20 carbon atoms, for example, N,N-dimethylcarbamoyl, N-phenylcarbamoyl, etc.), acylamino groups (preferably acylamino groups having 1 to 20 carbon atoms, for example, acetylamino, benzoylamino, etc.), alkylthio groups (preferably alkylthio groups having 1 to 20 carbon atoms, for example, methylthio, ethylthio, isopropylthio, benzylthio, etc.), arylthio groups (preferably arylthio groups having 6 to 26 carbon atoms, for example, phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio, etc.), heterocyclic thio groups (groups in which an -S- group is bonded to the above heterocyclic group), alkylsulfonyl groups (preferably alkylsulfonyl groups having 1 to 20 carbon atoms, for example, methylsulfonyl, ethylsulfonyl, etc.), arylsulfonyl groups (preferably an arylsulfonyl group having 6 to 22 carbon atoms, for example, benzenesulfonyl; an alkylsilyl group (preferably an alkylsilyl group having 1 to 20 carbon atoms, for example, monomethylsilyl, dimethylsilyl, trimethylsilyl, triethylsilyl; an arylsilyl group (preferably an arylsilyl group having 6 to 42 carbon atoms, for example, triphenylsilyl; an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 20 carbon atoms, for example, monomethoxysilyl, dimethoxysilyl, trimethoxysilyl, triethoxysilyl; an aryloxysilyl group having 6 to 42 carbon atoms, for example, triphenyloxysilyl; an aryloxysilyl group having 6 to 42 carbon atoms, for example, triphenyloxysilyl; a phosphoryl group (preferably a phosphoric acid group having 0 to 20 carbon atoms, for example, -OP(=O)(R, Ｐ ) ２ ), a phosphonyl group (preferably a phosphonyl group having 0 to 20 carbon atoms, for example, —P(═O)(R Ｐ ) ２ ), a phosphinyl group (preferably a phosphinyl group having 0 to 20 carbon atoms, for example, —P(R Ｐ ) ２ ), a phosphonic acid group (preferably a phosphonic acid group having 0 to 20 carbon atoms, for example, —PO(OR Ｐ ) ２ ), sulfo group (sulfonic acid group), carboxy group, hydroxy group, sulfanyl group, cyano group, halogen atom (for example, fluorine atom, chlorine atom, bromine atom, iodine atom, etc.). Ｐis a hydrogen atom or a substituent (preferably a group selected from the substituents G). Each of the groups listed as the substituents G may be further substituted with the substituent G. The alkyl group, alkylene group, alkenyl group, alkenylene group, alkynyl group and / or alkynylene group may be cyclic or chain-like, and may be linear or branched.

[0100] The present invention will be described in more detail below based on examples, but the present invention should not be construed as being limited thereto. In the following examples, "parts" and "%" representing compositions are based on mass unless otherwise specified. In the present invention, "room temperature" means 25°C.

[0101] [Synthesis and Preparation of Compounds] The compounds shown below were synthesized or prepared. PC-88A (mono-2-ethylhexyl (2-ethylhexyl)phosphonate) shown below was a commercially available product (manufactured by Tokyo Chemical Industry Co., Ltd.). VA-10 shown below was a commercially available product (Versatic acid 10, manufactured by Hexion).

[0102]

[0103] <Synthesis of Compound E-1> Compound E-1 was synthesized as follows. Specifically, 89 g of diethyl phosphite (manufactured by Tokyo Chemical Industry Co., Ltd.) and 450 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 1 L three-necked recovery flask and stirred thoroughly. While the three-necked recovery flask was ice-cooled, 23.2 g of sodium hydride (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was further added and stirred for 20 minutes while still ice-cooled. Thereafter, the reaction solution was heated and stirred for 30 minutes under reflux. Next, while the three-necked recovery flask was ice-cooled, 70.0 g of 1-bromo-2-ethylhexane (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise to the resulting reaction solution over 20 minutes, and the mixture was stirred at an internal temperature of 45°C for 24 hours. 300 g of water was added to the resulting reaction solution, followed by extraction with toluene, and the solvent was removed by distillation under reduced pressure to obtain 105 g of a yellow liquid.

[0104] Next, the obtained yellow liquid and 400 g of dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added to a 1 L three-necked recovery flask and stirred thoroughly. 113 g of bromotrimethylsilane (manufactured by Tokyo Chemical Industry Co., Ltd.) was further added to the three-necked recovery flask and stirred at room temperature for 4 hours. The solvent was removed from the obtained reaction solution by distillation under reduced pressure, and then 530 g of methanol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was added and stirred at an internal temperature of 40°C for 3 hours. 200 mL of aqueous sodium hydroxide solution (4 mol / L) was added to the reaction solution obtained in this manner, and the aqueous phase was washed twice with toluene. 65 mL of concentrated hydrochloric acid was added to the obtained aqueous solution, and the mixture was extracted with toluene. The solvent was then removed by distillation under reduced pressure to obtain 41.2 g of compound A (yield 59%, 2 steps). 20.0 g of compound A and Fine Oxocol 180N (branched C １８ H ３７ 23.6 g of cyclohexylcarbodiimide (manufactured by Nissan Chemical Industries, Ltd.) and 120 g of tetrahydrofuran (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added and stirred, and the temperature was raised to a reflux state. A solution of 23.4 g of dicyclohexylcarbodiimide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) dissolved in 120 g of tetrahydrofuran was added dropwise thereto over 3 hours, and the mixture was stirred for 4 hours. The resulting reaction solution was returned to room temperature, and the white solid was removed by filtration. The solvent was distilled off under reduced pressure from the resulting filtrate. The resulting crude product was dissolved in toluene and washed with water, and the solvent was distilled off under reduced pressure to obtain 30.5 g (yield 71%) of compound E-1 as a pale yellow liquid.

[0105] The synthesized compound E-1 was １ The compound was identified by m / z obtained by H-NMR (apparatus: BLUKER 400) and HPLC-MS.

[0106] <Synthesis of Compound E-2> In the synthesis of Compound E-1, 1-bromo-2-ethylhexane and Fineoxocol 180N were used in the synthesis of Compound E-2. １ and R ２ Compound E-2 was synthesized in the same manner as in the synthesis of compound E-1, except that the bromide and alcohol were changed to introduce the groups corresponding to the following: The synthesized compound E-2 was identified in the same manner as compound E-1.

[0107] <Synthesis of Compound E-3> Fine Oxocol 180N (branch C) was placed in a 500 mL three-necked recovery flask. １８ H ３７ 20.0 g of tetrabromide (manufactured by Nissan Chemical Industries, Ltd.), 39.4 g of carbon tetrabromide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and 130 g of dichloromethane (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) were added, and the mixture was stirred while cooling in an ice bath. To the resulting reaction solution, a solution consisting of 39.0 g of triphenylphosphine (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 110 g of dichloromethane was added dropwise over 10 minutes. The reaction solution was then warmed to room temperature and stirred for 2 hours. 4 M sodium hydroxide solution was added to this solution, and the mixture was extracted with dichloromethane. The solvent was then evaporated under reduced pressure to obtain the product (branch C １８ H ３７ Br) was obtained as a pale yellow liquid (yield 92%). 1.5 g of magnesium (Fujifilm Wako Pure Chemical Industries, Ltd.) and 100 g of diethyl ether were added to a 300 mL three-necked recovery flask and stirred at room temperature. 18.0 g of the above product was added dropwise to generate a Grignard reagent. Subsequently, 4.2 g of dibutyl phosphite was added while maintaining the temperature of the reaction solution below 15°C, and the reaction solution was then heated and stirred under reflux for 5 hours. While cooling the resulting reaction solution in an ice bath, 10% sulfuric acid was added dropwise, the organic layer was washed with a 15% aqueous sodium carbonate solution, and the solvent was distilled off under reduced pressure. The resulting product was purified by column chromatography to identify branched C １８ H ３７ Phosphorous acid having two groups was obtained as a colorless, transparent liquid (yield 85%). 78 g of hydrogen peroxide solution (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 10.0 g of the above-mentioned phosphorous acid were added to a 200 mL three-necked recovery flask and stirred at room temperature. The reaction solution was then heated to 65°C and stirred for 24 hours. 100 g of saturated aqueous sodium thiosulfate solution was added, followed by extraction with toluene and distillation of the solvent under reduced pressure to obtain compound E-3 as a colorless, transparent liquid (yield 95%). The synthesized compound E-3 was identified in the same manner as compound E-1.

[0108] [Preparation of Metal Ion-Containing Aqueous Solution W1] 57.2 g of cobalt (II) sulfate heptahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) and 57.4 g of nickel (II) sulfate heptahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) were added to a 1 L volumetric flask, and the mixture was diluted with ultrapure water. The mixture was stirred at 40° C. to dissolve the mixture, and then cooled to room temperature to prepare metal ion-containing aqueous solution W1. [Preparation of Metal Ion-Containing Aqueous Solution W2] Metal ion-containing aqueous solution W2 was prepared in the same manner as in the preparation of metal ion-containing aqueous solution W1, except that 52.7 g of manganese (II) sulfate pentahydrate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) was further added.

[0109] [Preparation of Metal Ion-Containing Aqueous Solution W3] Metal ion-containing aqueous solution W3 was prepared in the same manner as metal ion-containing aqueous solution W1, except that nickel(II) sulfate heptahydrate was not added and the amount of cobalt(II) sulfate heptahydrate used was changed so that the Co ion content was 36,000 ppm. [Preparation of Metal Ion-Containing Aqueous Solution W4] Metal ion-containing aqueous solution W4 was prepared in the same manner as metal ion-containing aqueous solution W2, except that cobalt(II) sulfate heptahydrate and nickel(II) sulfate heptahydrate were not added and the amount of manganese(II) sulfate pentahydrate used was changed so that the Mn ion content was 36,000 ppm. The density (g / cm) at 25°C of each of the prepared metal ion-containing aqueous solutions was ３ ) are shown in Table 1-2. The density at 5°C was within the error range of the density at 25°C.

[0110] <Preparation of Extractant Solution (Oil Phase)> Each synthesized or prepared compound was added to a 100 mL volumetric flask, and kerosene (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) was used to fill the flask at room temperature to prepare extractant solutions Y1 to Y8 and Yc1 to Yc3 containing each compound as an acidic extractant in the amounts shown in Table 1-2. Note that extractant solution Y4 did not use kerosene, and contained only compound PC-88A. The density (g / cm ) of each prepared extractant solution at 25°C was ３ ) are shown in Table 1-2. The density at 5°C was within the error range of the density at 25°C.

[0111] An extraction apparatus 1 shown in FIG. 1 was prepared as an extraction apparatus. The inner diameters (equivalent diameters) of the aqueous phase flow pipe 11 and the oil phase flow pipe 12 were both 1 mm. The lengths and inner diameters (equivalent diameters) of the tapered portions 11a and 12a at their open ends were both 1 mm and 0.5 mm. Thus, the ratio of the inner diameter of the open end of the tapered portion to the inner diameter of each flow pipe (flow diameter reduction ratio) was 0.5. Furthermore, flow pipes were prepared in which only the inner diameters (equivalent diameters) of the open ends of the tapered portions 11a and 12a were changed to 0.15 mm (flow diameter reduction ratio: 0.15), 0.35 mm (flow diameter reduction ratio: 0.35), 0.55 mm (flow diameter reduction ratio: 0.55), or 0.65 mm (flow diameter reduction ratio: 0.65). The aqueous phase flow pipe 11 and the oil phase flow pipe 12 used in Comparative Example 2 were prepared as pipes having the above-mentioned inner diameters up to the confluence section without tapered portions. The confluence section 13 was a circular pipe having the same diameter as the inner diameter of the open ends of the tapered portions 11a and 12a, and its length (the distance between the aqueous phase flow pipe 11 and the oil phase flow pipe 12) was 2 mm. The mixing section 14 had a front-stage mixing section 14a and a rear-stage mixing section 14b, each consisting of a thickened section and a pipe section with a constant inner diameter. The connection diameter (equivalent diameter) of the thickened section to the confluence section 13 was 0.5 mm, the length of the pipe section was 100 mm, and the inner diameter (equivalent diameter) of the pipe section was 1 mm. The length of the rear-stage mixing section 14b was 100 mm, and the inner diameter (equivalent diameter) of the pipe section was 1 mm. The total length of the first-stage mixing section 14a and the second-stage mixing section 14b was determined by confirming and identifying the time (length) required for the three-liquid mixture to reach extraction equilibrium. The length of the pH adjuster transfer pipe 15 was 50 mm, and its inner diameter was 1 mm. The separation section 16 was a vial with an inner diameter of 36 mm.

[0112] An extraction apparatus 2 shown in Fig. 2 was prepared as an extraction apparatus. In the extraction apparatus 1, which was equipped with an aqueous phase flow pipe 11 and an oil phase flow pipe 12, the inner diameters (equivalent diameters) of the open ends of the tapered portions 11a and 12a of which were set to 0.5 mm (reduction ratio of flow diameter: 0.5), a pH adjuster transfer pipe 15 was connected to the mixing section 13 at a right angle to the aqueous phase flow pipe 11 and the oil phase flow pipe 12, which were arranged on the same line (forming a mixing section 23), thereby producing the extraction apparatus 2.

[0113] Example 1 Implementation of One Cycle of Extraction Method at 25°C In Example 1, metal ions were extracted under the conditions shown in Tables 1-1 to 1-3 using an extraction apparatus 1 equipped with an aqueous phase flow pipe 11 and an oil phase flow pipe 12 having inner diameters (specifically, 0.5 mm) at the open ends of the tapered portion 11a and the tapered portion 12a shown in the "Aqueous Phase Inner Diameter Ratio" and "Oil Phase Inner Diameter Ratio" columns of Table 1-2. A metal ion-containing aqueous solution W1 was sent from the aqueous phase flow pipe 11, and an extractant solution Y1 was sent from the oil phase flow pipe 12, each at a flow rate (flow rate) of 6.0 mL / min (internal pressure of 0.06 MPa) toward the confluence 13. The metal ion-containing aqueous solution W1 and the extractant solution Y1 were merged at the confluence 13, and the merged solution was allowed to continue flowing through the mixing section 14 (Step 1). The mixing conditions in Step 1 are shown in the "Mixing Conditions" column of Table 1-2 (the same applies to Examples 2 to 19 and Comparative Examples 1 to 3). After one minute or more had elapsed since the start of the liquid transfer, the transfer of a pH adjuster aqueous solution (4 M sodium hydroxide aqueous solution or 4 M hydrochloric acid) from the pH adjuster transfer pipe 15 was initiated to form a three-liquid combined liquid, which was then further circulated through the downstream mixing section 14b (Step 2). The amount of pH adjuster aqueous solution transferred was adjusted so that the pH of the three-liquid combined liquid (aqueous phase) in the downstream mixing section 14b was the value shown in the "pH at mixing" column in Table 1-2. The flow rate of the combined liquid flowing through the downstream mixing section 14 was 12.0 mL / min. The mixing temperature in the downstream mixing section 13, upstream mixing section 14a, and downstream mixing section 14b was 25°C. The three-liquid combined liquid flowing out of the downstream mixing section 14b had already reached extraction equilibrium, as confirmed by collecting the three-liquid combined liquid in vial tubes for one minute each and observing that their pHs had become constant. The three-liquid combined liquid was then transferred to and collected in the vial tube serving as the separation section 16. The combined solution of the three liquids was then allowed to stand at the same temperature for 30 minutes, and after confirming that the organic phase (oil phase) and the aqueous phase had separated into two phases, the aqueous phase was separated and removed (step 3), and the metal ions were separated and recovered. The pH was measured using a pH meter (SK-620pHII, manufactured by Satotec Co., Ltd.).

[0114] In <Performing one cycle of extraction method at 25°C>, the dissolved metal ion content of the aqueous phase used and the aqueous phase after the first extraction and separation cycle was quantified using an inductively coupled plasma optical emission spectroscopy (ICP-OES) analyzer (Optima 7300D (trade name), manufactured by PerkinElmer). The measured value of the dissolved metal ion content of the aqueous phase used is shown in the "Metal ion concentration (ppm) in aqueous phase before extraction" column of Table 1-1, and the measured value of the dissolved metal ion content of the aqueous phase after the first extraction and separation cycle is shown in the "Metal ion concentration (ppm) in aqueous phase after first extraction at 25°C" column of Table 1-1. The metal ions extracted in Example 1 are shown in the "Type" column of the "Extracted metal ions" column of Table 1-2, and the metal ions extracted at the maximum extraction amount are shown in the "Maximum extracted ions" column of the same column of Table 1-2. The results for the metal ions extracted in the <20 cycles of extraction method at 25°C> described below and the <1 cycle of extraction method at 5°C> were the same.

[0115] <Implementation of 20 Cycles of Extraction Method at 25°C> Twenty consecutive extraction and separation cycles were performed in the same manner as in the above <Implementation of One Cycle of Extraction Method at 25°C>, except that the extractant solution Y1 (used extractant solution Y1) phase-separated from the aqueous phase in the separation section 16 was used as the extractant solution Y1 for the next cycle. That is, the prepared extractant solution Y1 was used in 20 consecutive extraction and separation cycles. It was confirmed that the three-liquid combined liquid flowing out of the downstream mixing section 14b had already reached extraction equilibrium in each extraction and separation cycle. Each oil phase recovered by phase separation in the separation section 16 was used for back-extraction of metal ions as follows. That is, 10 mL of purified water was added to 10 mL of each recovered oil phase, and 10 M hydrochloric acid was added to adjust the pH of the mixture to 1.0. The mixture was stirred at room temperature for 30 minutes and then allowed to stand at the same temperature for 1 hour. After confirming that the mixture had separated into two layers, an organic phase (oil phase) and an aqueous phase, the oil phase was separated and recovered.

[0116] The dissolved metal ion content of the aqueous phase obtained after 20 consecutive extraction and separation cycles was quantified in the same manner as in <Performing one cycle of extraction method at 25°C> above. The measured value of the dissolved metal ion content of the aqueous phase after the 20th extraction and separation cycle is shown in the column "Metal ion concentration (ppm) 25°C in aqueous phase after 20 extractions" in Table 1-1.

[0117] <Performing One Cycle of the Extraction Method at 5°C> One cycle of the extraction method was performed at 5°C in the same manner as in <Performing One Cycle of the Extraction Method at 25°C> above, except that the metal ion-containing aqueous solution W1 and the extractant solution Y1 were cooled to an internal temperature of 5°C (the mixing temperature in the confluence section 13, the front-stage mixing section 14a, and the rear-stage mixing section 14b was 5°C). It was confirmed that the three-liquid combined solution flowing out from the rear-stage mixing section 14b had reached extraction equilibrium. The dissolved metal ion content of the aqueous phase obtained by performing one extraction and separation cycle at 5°C was quantified in the same manner as in <Performing One Cycle of the Extraction Method at 25°C> above. The measured value of the dissolved metal ion content in the aqueous phase after the first extraction and separation cycle at 5°C is shown in the column "Metal ion concentration (ppm) 5°C in the aqueous phase after one extraction" in Table 1-1.

[0118] [Examples 2 to 18 and Comparative Examples 1 to 3] For Examples 2 to 8, 10 to 17 and Comparative Examples 1 to 3, metal ions were extracted under the conditions shown in Tables 1-1 to 1-3 using the extraction apparatus 1 equipped with an aqueous phase circulation pipe 11 and an oil phase circulation pipe 12 having the inner diameters at the open ends of the tapered portion 11a and the tapered portion 12a shown in the "Aqueous Phase Inner Diameter Ratio" and "Oil Phase Inner Diameter Ratio" columns of Table 1-2. Note that for Example 10, the aqueous solution shown in the "Aqueous Phase" column of Table 1-1 was used as the aqueous phase. For Examples 9 and 18, metal ions were extracted under the conditions shown in Tables 1-1 to 1-3 using an extraction apparatus 1 equipped with an aqueous phase circulation pipe 11 and an oil phase circulation pipe 12 having the inner diameters at the open ends of the tapered portion 11a and the tapered portion 12a shown in the "Aqueous Phase Inner Diameter Ratio" and "Oil Phase Inner Diameter Ratio" columns of Table 1-2, and having one static mixer with the following characteristics built into the downstream mixing section 14b. (Static mixer characteristics) Inner diameter (equivalent diameter inside the pipe): 1 mm Total length: 12 mm Number of mixing elements: 6 Material: Stainless steel

[0119] <Implementation of One Cycle of Extraction Method at 25°C> In <Implementation of One Cycle of Extraction Method at 25°C> of Example 1, <Implementation of One Cycle of Extraction Method at 25°C> of Examples 2 to 18 and Comparative Examples 1 to 3 was carried out in the same manner as in <Implementation of One Cycle of Extraction Method at 25°C> of Example 1, except that in <Implementation of One Cycle of Extraction Method at 25°C> of Example 1, the metal ion-containing aqueous solution was changed to the metal ion-containing aqueous solution shown in the "Aqueous Phase" column of Table 1-1 as necessary, the extractant solution was changed to the extractant solution shown in the "Oil Phase" column of Table 1-2, the pH of the three-liquid confluence liquid (aqueous phase) in the subsequent mixing section 14b was set to the value shown in the "pH at Mixing" column of Table 1-2, and further, in Examples 14 to 17, each flow rate was changed to the flow rate shown in the "Aqueous Phase Flow Rate" column and the "Oil Phase Flow Rate" column in the "Mixing Conditions" column of Table 1-2. In each Example and Comparative Example, the content of dissolved metal ions in the aqueous phase obtained after the first extraction and separation cycle was quantified in the same manner as in Example 1 (<Implementation of one cycle of the extraction method at 25°C>). The results are shown in the "Metal ion concentration (ppm) in the aqueous phase after one extraction at 25°C" column of Table 1-1. The metal ions extracted in Examples 2 to 18 and Comparative Examples 1 to 3 are shown in the "Type" column of the "Extracted metal ions" column of Table 1-2, and the metal ions extracted in the maximum amount are shown in the "Maximum extracted ions" column of the same column of Table 1-2. Note that in each Example and Comparative Example, the results for the metal ions extracted in <Implementation of 20 cycles of the extraction method at 25°C> and <Implementation of one cycle of the extraction method at 5°C> were the same.

[0120] <Implementation of 20 Cycles of Extraction Method at 25°C> In <Implementation of 20 Cycles of Extraction Method at 25°C> of Example 1, <Implementation of 20 Cycles of Extraction Method at 25°C> of Examples 2 to 18 and Comparative Examples 1 to 3 were carried out in the same manner as in <Implementation of 20 Cycles of Extraction Method at 25°C> of Example 1, except that in <Implementation of 20 Cycles of Extraction Method at 25°C> of Example 1, the metal ion-containing aqueous solution was changed to the metal ion-containing aqueous solution shown in the "Aqueous Phase" column of Table 1-1 as necessary, the extractant solution was changed to the extractant solution shown in the "Oil Phase" column of Table 1-2, the pH of the three-liquid confluence liquid (aqueous phase) in the subsequent mixing section 14b was set to the value shown in the "pH at Mixing" column of Table 1-2, and further, in Examples 14 to 17, each flow rate was changed to the flow rate shown in the "Aqueous Phase Flow Rate" column and the "Oil Phase Flow Rate" column in the "Mixing Conditions" column of Table 1-2. In the same manner as in Example 1 <Implementation of one cycle of extraction method at 25°C>, the content of dissolved metal ions in the aqueous phase obtained after the 20th extraction and separation cycle was quantified in each Example and Comparative Example, and the results are shown in the column "Metal ion concentration (ppm) 25°C in aqueous phase after 20 extractions" in Table 1-1.

[0121] <Implementation of one cycle of extraction method at 5°C> In <Implementation of one cycle of extraction method at 5°C> of Example 1, the metal ion-containing aqueous solution was changed to the metal ion-containing aqueous solution shown in the "Aqueous Phase" column of Table 1-1 as necessary, the extractant solution was changed to the extractant solution shown in the "Oil Phase" column of Table 1-2, the pH of the three-liquid combined liquid (aqueous phase) in the subsequent mixing section 14b was set to the value shown in the "pH at mixing" column of Table 1-2, and further, in Examples 14 to 17, the respective flow rates were changed to the flow rates shown in the "Aqueous Phase Flow Rate" and "Oil Phase Flow Rate" columns in the "Mixing Conditions" column of Table 1-2. Except for this, <Implementation of one cycle of extraction method at 5°C> of Examples 2 to 18 and Comparative Examples 1 to 3 were carried out in the same manner as in <Implementation of one cycle of extraction method at 5°C> of Example 1. In the same manner as in Example 1, <Performing one cycle of extraction method at 25°C>, the first extraction and separation cycle was carried out at 5°C in each Example and Comparative Example, and the content of dissolved metal ions in the aqueous phase obtained was quantified. The results are shown in the column "Metal ion concentration (ppm) 5°C in aqueous phase after one extraction" in Table 1-1.

[0122] Example 19 For Example 19, metal ion extraction was performed using the extraction apparatus 2 under the conditions shown in Tables 1-1 to 1-3. That is, in Example 19, the pH during mixing was changed to the value shown in the "pH during mixing" column of Table 1-2, and the same mixing conditions as in Example 1 were used to perform the above-mentioned <1 cycle of extraction method at 25°C>, <20 cycles of extraction method at 25°C>, and <1 cycle of extraction method at 5°C>. The results are shown in the "Metal ion concentration (ppm) in the aqueous phase after one extraction at 25°C" column, the "Metal ion concentration (ppm) in the aqueous phase after 20 extractions at 25°C" column, and the "Metal ion concentration (ppm) in the aqueous phase after one extraction at 5°C" column in Table 1-1, respectively.

[0123] It was confirmed that the three-liquid combined liquid flowing out from the rear-stage mixing section 14b reached extraction equilibrium in all cases in Examples 1 to 19 and Comparative Examples 1 to 3. In Examples 1 to 19 and Comparative Examples 1 to 3, the extracted metal ions are shown in the "Type" column of the "Extracted Metal Ions" section in Table 1-2, and the metal ions extracted in the maximum extraction amount are shown in the "Maximum Extracted Ions" column in the same section in Table 1-2.

[0124] <Evaluation 1: Evaluation of Extraction Rate> In each Example and Comparative Example, the extraction rate (unit: %) of the metal ion extracted at the maximum extraction amount was calculated using the following formula from the metal ion concentration CI in the prepared aqueous phase (the aqueous phase before the first separation / extraction cycle) and the metal ion concentration C1 in the aqueous phase obtained in <Implementation of one cycle of the extraction method at 25°C> or the metal ion concentration C20 in the aqueous phase after 20 extraction / separation cycles in <Implementation of 20 cycles of the extraction method at 25°C>. The results are shown in the "First" or "20th" column of the "Extraction Rate" column in Table 1-2, respectively. In this test, a larger value for each extraction rate indicates a better extraction ability (recovery ability) for a specific metal ion in each extraction / separation cycle. Furthermore, the smaller the difference between the initial extraction rate and the 20th extraction rate (initial extraction rate - 20th extraction rate), the more specific metal ions can be recovered while maintaining the high extractability of an unused acidic extractant, even when the acidic extractant (oil phase) is repeatedly used (even when extraction and separation cycles are repeatedly performed), and the more durable the acidic extractant is, allowing for multiple extraction and separation cycles to be performed while maintaining the initial high extraction rate (high durability can be achieved). In this test, durability was evaluated according to the following evaluation criteria. The results are shown in the "Durability" column of Table 1-2. Regarding the durability results for Comparative Example 1 and Examples 1 to 4, the relationship between the content of acidic extractant in the oil phase and the extraction rate at the 20th extraction and separation cycle is shown in Figure 4. In this test, a durability rating of D or higher is considered acceptable. The initial extraction rate and the 20th extraction rate were each evaluated as reference tests, with the initial extraction rate being preferably 95% or higher and the 20th extraction rate being preferably 90% or higher. First extraction rate (%) = [(CI - C1) / CI] x 100 20th extraction rate (%) = [(CI - C20) / CI] x 100 - Evaluation criteria - A: The difference between the first extraction rate and the 20th extraction rate is 1% or less. B: The difference between the first extraction rate and the 20th extraction rate is more than 1% and 4% or less. C: The difference between the first extraction rate and the 20th extraction rate is more than 4% and 8% or less. D: The difference between the first extraction rate and the 20th extraction rate is more than 8% and 12% or less. E: The difference between the first extraction rate and the 20th extraction rate is more than 12% and 16% or less. F: The difference between the first extraction rate and the 20th extraction rate is more than 16%.

[0125] <Evaluation 2: Evaluation of Low-Temperature Resolution> In each Example and Comparative Example, <Implementation of one cycle of the extraction method at 5°C>, the extraction amount (difference, unit: ppm) of each metal ion was calculated from the metal ion concentration in the aqueous phase before extraction and the metal ion concentration in the aqueous phase after the first extraction and separation cycle. The extraction amount (ppm) of the maximum extraction amount of metal ion was divided by the total extraction amount (ppm) of other metal ions to calculate the low-temperature resolution (selectivity) as the ratio of the extraction amounts. The results are shown in the "Low Temperature" column of the "Resolution" column in Table 1-2. In this test, a higher value of the low-temperature resolution indicates better resolution (selectivity) of specific metal ions, and a value of 2.0 or higher is acceptable. In Table 1-2, the room temperature resolution in <Implementation of one cycle of the extraction method at 25°C> in each Example and Comparative Example was evaluated as a reference test, and the results calculated in the same manner as the low-temperature resolution described above were shown in the "Room Temperature" column of the "Resolution" column in Table 1-2.

[0126] <Evaluation 3: Evaluation of Extraction Amount> In each Example and Comparative Example, in <Implementation of One Cycle of Extraction Method at 25°C>, metal ions were extracted in the same manner as in <Implementation of One Cycle of Extraction Method at 25°C>, except that metal ion-containing aqueous solution W3 or W4 shown in Table 1-3 was used instead of metal ion-containing aqueous solution W1 or W2 shown in Table 1-1, and the contents of dissolved metal ions in the aqueous phase used (metal ion-containing aqueous solution W3 or W4) and in the aqueous phase after extraction were quantified. The measured values ​​of the dissolved metal ion contents in the aqueous phase used are shown in the column "Metal ion concentration (ppm) in aqueous phase before extraction" in Table 1-3, and the measured values ​​of the dissolved metal ion contents in the aqueous phase after the first extraction separation cycle are shown in the column "Metal ion concentration (ppm) in aqueous phase after first extraction" in Table 1-3. The amount of extraction (difference, unit: ppm) of each metal ion was calculated from the metal ion concentration in the aqueous phase before extraction and the metal ion concentration in the aqueous phase after the first extraction / separation cycle, and the extraction rate (unit: %) of the metal ion extracted at the maximum extraction rate was calculated in the same manner as in <Evaluation 1: Evaluation of Extraction Rate> above. The results are shown in the "Extraction Amount" and "Extraction Rate" columns of Table 1-3, respectively. In this test, the larger the extraction amount and extraction rate, the greater the amount of metal ion extracted into the oil phase, meaning that a larger mass of metal ion is extracted into the oil phase per unit volume. In this test, an extraction amount of 25,000 ppm or more is considered acceptable. Note that the extraction rate is a reference test, and it is preferable that it is 70% or more.

[0127]

[0128]

[0129]

[0130] In Table 1-2, "aqueous phase flow rate" and "oil phase flow rate" indicate the "flow rates" of the aqueous phase and the oil phase, and "aqueous phase inner diameter", "oil phase inner diameter" and "junction inner diameter" indicate the inner diameters (equivalent diameters) of the aqueous phase flow pipe 11, the oil phase flow pipe 12 and the junction, respectively. Furthermore, "aqueous phase inner diameter ratio" and "oil phase inner diameter ratio" indicate the ratio of the inner diameter of the open end of the tapered portion to the inner diameter of each flow pipe 11 or 12 (reduction ratio of the flow diameter). ＳＴ " and "Oil Phase E ＳＴ" is the kinetic energy E of the water phase or oil phase ＳＴ In Table 1-2, the unit of "content" of the acidic extractant is "volume %", the unit of "flow rate" is "mL / min", the unit of "inner diameter" is "mm", and the unit of "density" is "g / cm ３ " and the unit of "cross-sectional area" is "mm ２ " and "E ＳＴ The unit is "J / sec / cm ２ ", but will be omitted.

[0131] The results shown in Tables 1-1 to 1-3 and Figure 4 reveal the following: Comparative Examples 1 and 3, in which the content of the acidic extractant in the oil phase used was too low, were inferior in extraction amount and durability, even though they employed a flow-type mixing method. The poor durability is thought to be due to the deterioration and decomposition of the acidic extractant caused by the pH adjuster or the like. Furthermore, Comparative Example 2, in which the flow-type mixing method was employed but the flow diameter was not reduced before the aqueous phase and oil phase were joined, was inferior in durability and resolution. One of the reasons for this is thought to be that the two phases could not be sufficiently mixed at the joining point.

[0132] In contrast, Examples 1 to 19, which employed a flow-type mixing method, used an oil phase containing 35 to 100 volume percent of an acidic extractant, and reduced the flow diameter before merging the aqueous and oil phases, all achieved high extraction yields, high durability, and high resolution of the two metal ions present in the aqueous phase (Examples 1 to 9 and 11 to 19: Co ions, Example 10: Mn ions). Furthermore, Examples 9 and 18, which used a static mixer, significantly improved resolution, extraction rate, and extraction amount. Even when using the conventional extractant VA-10, which has poor extraction ability (Example 18), resolution, extraction rate, and extraction amount were all achieved at even higher levels. As described above, the extraction method of the present invention can separate and recover a specific metal ion from two or more metal ions belonging to different groups that have similar physical and chemical behaviors, particularly one metal ion from among the metal ions belonging to groups 7, 9, and 10 that can be recovered from waste LiB, with a high extraction yield, high durability, and high resolution (high selectivity).

[0133] The above results demonstrate that stripping the oil phase obtained in each of the above examples using conventional methods and conditions enables the metal ions extracted into the oil phase with high extraction yields and high resolution to be separated and recovered in high yields without sacrificing high selectivity, and in a simple and highly productive manner. However, in technologies for recovering a specific metal ion from an aqueous phase containing multiple metal ions, it is generally difficult to recover a specific metal ion with high extraction yields and high resolution. Maintaining high resolution reduces the extraction yield, and multiple separation and recovery cycles are required to achieve a desired extraction yield. In contrast, the present invention uses a simple and highly workable flow-type mixing method to extract one of two different metal ions from the aqueous phase with high extraction yields, high durability, and high resolution. Therefore, in light of the above-mentioned circumstances, the present invention is of great technical significance in that it allows the extraction of one metal ion from the resulting oil phase in high extraction yield, while further improving high resolution (high selectivity) and in a simple and productive manner.

[0134] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0135] This application claims priority based on Japanese Patent Application No. 2023-165476 filed in Japan on September 27, 2023, and Japanese Patent Application No. 2024-055406 filed in Japan on March 29, 2024, the contents of which are incorporated herein by reference.

[0136] 1, 2 Extraction device 11 Aqueous phase distribution pipe 11a Tapered part (tapered part) 11b Large diameter part 11c Small diameter part 12 Oil phase distribution pipe 12a Tapered part (tapered part) 13, 23 Confluence part 14, 24 Mixing part 14a First stage mixing part 14b Second stage mixing part 15 pH adjuster transfer pipe 16 Separation part 16a Oil phase discharge pipe 16b Water phase discharge pipe

Claims

1. A method for extracting metal ions, in which an aqueous phase containing metal ions and an oil phase containing an acidic extractant are joined during flow, the two phases are mixed, and then phase-separated to extract the metal ions into the oil phase, comprising the steps of: setting the content of the acidic extractant in the oil phase to be flowed to 35-100 volume %, reducing the flow diameters of the aqueous phase and oil phase flowing, then joining them together and continuing to flow them; joining the aqueous phase and the oil phase with an aqueous pH adjuster solution, and further flowing them; and separating the phases of the three-liquid combined liquid after the extraction of the metal ions to be extracted has reached extraction equilibrium.

2. The method for extracting metal ions according to claim 1, wherein in the further flowing step, the two-liquid mixture of the aqueous phase and the oil phase that were combined in the continued flowing step and the aqueous pH adjuster solution are combined and further flowed.

3. The method for extracting metal ions according to claim 1, wherein in the continuing flowing step, a further flowing step is carried out to combine the aqueous phase, the oil phase and the aqueous solution of pH adjuster all at once and flow further.

4. The method for extracting metal ions according to claim 1, wherein in at least one of the subsequent flowing step and the further flowing step, the combined liquid is caused to flow through a flow path having a static mixer installed therein.

5. The method for extracting metal ions according to claim 1, wherein the aqueous phase and the oil phase are merged by utilizing collision of the flowing phases.

6. The method for extracting metal ions according to claim 1, wherein the ratio of reduction in flow diameter when the aqueous phase and the oil phase are joined is 0.1 to 0.

8.

7. When the aqueous phase and the oil phase are joined by utilizing the collision of the flowing phases, the kinetic energy per unit area and per unit time of the aqueous phase and the oil phase is set to 50 to 100,000 J / sec / m ２ The method for extracting metal ions according to claim 1 .

8. The method for extracting metal ions according to claim 1, wherein the three-liquid mixture is allowed to stand to separate into an aqueous phase and an oil phase.

9. The method for extracting metal ions according to claim 1, wherein the metal ions include a plurality of types of metal ions, and at least one of the types of metal ions is separated and extracted from the other types of metal ions.

10. A method for extracting metal ions according to claim 1, in which an extraction and separation cycle consisting of the continued flowing step, the further flowing step, and the phase separation step is carried out a plurality of times, and the oil phase separated in the phase separation step is reused as the oil phase in the next extraction and separation cycle.

11. The method for extracting metal ions according to claim 1, wherein the acidic extractant comprises a phosphoric acid compound.

12. The method for extracting metal ions according to claim 11, wherein the acidic extractant is represented by the following formula (I): In 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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