Solvent extraction apparatus and ion separation method

Abstract

Provided is a solvent extraction apparatus which has excellent phase separation performance between an organic phase and an aqueous phase, can effectively reduce the installation volume and area, and has a reduced exposed area of ​​the organic phase. [Solution] A solvent extraction apparatus 10 has a column 12 in an upright state into which a mixed liquid 5, which is a mixture of an aqueous phase 3 and an organic phase 4, is introduced and separated into the aqueous phase 3 and the organic phase 4, and a liquid inlet 14 for introducing the mixed liquid 5 into the column, and a ratio (C / L) of a cross-sectional area C of the column to a square value of a height difference L between an organic phase outlet 48A and an aqueous phase outlet 47A of the column 12 is calculated. 2 ) was less than 1.0, and the liquid introduction position Xc of the liquid introduction part 14 was located below the central position Xr in the vertical direction between the organic phase outlet and the aqueous phase outlet.

Description

[Technical field]

[0001] The present invention relates to a solvent extraction apparatus having a separation column. [Background technology]

[0002] The solvent extraction method is a method of separating metal elements by contacting an aqueous phase consisting of an aqueous solution containing the metal elements to be separated with an organic phase consisting of a metal extractant for extracting specific metal elements and an organic solvent for diluting the metal extractant, thereby extracting the metal elements into the metal extractant. Conventionally, various types of solvent extraction apparatuses have been proposed for separating multiple elements using an organic phase and an aqueous phase.

[0003] Patent Document 1 proposes a solvent extraction apparatus using a vertical multi-stage separation column called a pulse column. In this method, multiple perforated plates are arranged in one separation column, and this configuration improves the contact efficiency between the organic phase and the aqueous phase. In this separation column, the organic phase is introduced from the bottom of the column, and the aqueous phase is introduced from the top of the column. In this separation column, after the organic phase and the aqueous phase come into contact in the column, the aqueous phase is recovered from the bottom of the column, and the organic phase is recovered from the top of the column. Also, as described in Patent Document 2, a technique called emulsion flow is known. In this technique, an organic phase is introduced from the bottom of a separation column and an aqueous phase is introduced from the top of the separation column in the form of small droplets, and the two are brought into contact with each other in the separation column. In this method, the separation column is also configured such that, after the organic phase and the aqueous phase come into contact with each other, the organic phase moves to the top of the column and the aqueous phase moves to the bottom of the column.

[0004] In the solvent extraction apparatus as described in Patent Document 1, the organic phase and the aqueous phase are brought into contact with each other through a perforated plate in the separation column, and the organic phase and the aqueous phase are separated in the same column, so it is difficult to say that the efficiency of the separation between the organic phase and the aqueous phase is high. In particular, when separating metal ions, it is necessary to separate the organic phase and the aqueous phase over a long period of time in order to improve the separation performance, which results in a low time efficiency of the separation. In the method of Patent Document 2, similar to Patent Document 1, the mixing tank and separation tank are integrated, and both mixing and phase separation of the aqueous phase and the organic phase are performed in the same container. It is difficult to perform both mixing and phase separation sufficiently, and there are cases where the aqueous phase and the organic phase are not in contact with each other, the liquid that has been left to stand is not separated sufficiently due to insufficient standing time, or the liquid that has been left to stand is brought into contact with another phase again, making it difficult to obtain stable separation performance.

[0005] Patent Document 3 and Non-Patent Document 1 disclose a mixer-settler (MS) that is composed of a mixing tank (mixer section) that mixes the aqueous phase and the organic phase, and a separation tank (settler section) that separates the aqueous phase and the organic phase based on the difference in specific gravity. As shown in Patent Document 3 and Non-Patent Document 1, conventional MS devices generally use a method in which the mixed liquid discharged from the mixing tank that mixes the aqueous phase and the organic phase is separated over time in a horizontally wide stationary tank based on the difference in specific gravity. According to this method, the aqueous phase and the organic phase are well separated, and the aqueous phase and the organic phase are efficiently recovered in the discharge section. By arranging multiple extraction units of this mixer-settler (MS) in parallel and performing continuous extraction processing in multiple stages, two or more elements can be precisely separated and refined. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 06-160587 [Patent Document 2] JP 2020-203267 A [Patent Document 3] JP 2022-147876 A [Non-patent literature]

[0007] [Non-Patent Document 1] "Science of Rare Earths" edited by Ginya Adachi (Kagaku Dojin 1999) p.196 Summary of the Invention [Problem to be solved by the invention]

[0008] As described above, in the solvent extraction apparatus described in Patent Document 3 and Non-Patent Document 1, in order to enhance the element separation performance, the organic phase and the aqueous phase are separated over a long period of time in a horizontally wide settling tank. For this reason, a large volume of the settling tank is required for separating the organic phase and the aqueous phase, and an installation area is required. In addition, the aqueous phase and the organic phase during the phase separation must always remain in the settling tank, which reduces the efficiency of the phase separation. In addition, the exposed area of ​​the organic phase is large, which causes the organic phase to volatilize, resulting in high costs.

[0009] An object of the present invention is to provide a solvent extraction apparatus which has excellent phase separation performance between an organic phase and an aqueous phase, can effectively reduce the installation volume and area, and has a reduced exposed area of ​​the organic phase. [Means for solving the problem]

[0010] The present inventors have found that the above-mentioned problems can be solved by using a column having a shape that satisfies certain conditions and introducing a mixture of an aqueous phase and an organic phase into a specified position of the column.

[0011] The present invention provides a column in an upright position into which a mixed liquid obtained by mixing an aqueous phase and an organic phase is introduced and into which the mixed liquid is separated into the aqueous phase and the organic phase, and a liquid introduction part for introducing the mixed liquid into the column, The column has an aqueous phase outlet and an organic phase outlet through which the aqueous phase and the organic phase separated from the mixed liquid are discharged, respectively, and a ratio (C / L 2 ) is less than 1.0, and The column provides a solvent extraction apparatus, wherein the liquid introduction position of the liquid introduction part is lower than the center position in the vertical direction between the aqueous phase outlet and the organic phase outlet.

[0012] The present invention also provides a method for separating at least one ion from two or more ions using a solvent extraction apparatus having an upright column into which a mixed liquid obtained by mixing an aqueous phase and an organic phase is introduced and into which the mixed liquid is separated into the aqueous phase and the organic phase, and a liquid inlet portion for introducing the mixed liquid into the column, comprising: The aqueous phase contains two or more ions to be separated, the organic phase comprises an extractant capable of complexing at least one of the two or more ions; In the solvent extraction apparatus, The column has an aqueous phase outlet and an organic phase outlet through which the aqueous phase and the organic phase separated from the mixed liquid are discharged, respectively, and a ratio (C / L 2 ) is less than 1.0, and The column provides a method for separating ions, wherein the liquid introduction position of the liquid introduction part is lower than the center position in the vertical direction between the aqueous phase outlet and the organic phase outlet. Effect of the Invention

[0013] According to the present invention, it is possible to provide a solvent extraction apparatus which has excellent phase separation performance between an organic phase and an aqueous phase, can effectively reduce the installation volume and capacity, and has a reduced exposed area of ​​the organic phase. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing an example of the solvent extraction apparatus of the present invention. [Diagram 2] FIG. 2 is a schematic diagram for explaining the dimensions and area of ​​the column of the solvent extraction apparatus. [Diagram 3] FIG. 3 is a schematic diagram showing a solvent extraction apparatus according to still another embodiment of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a solvent extraction apparatus according to still another embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described below based on its preferred embodiments. FIG. 1 shows one embodiment of a solvent extraction apparatus 10 of the present invention. The solvent extraction apparatus 10 has a column 12 into which a mixed liquid 5, which is a mixture of an aqueous phase 3 and an organic phase 4, is introduced and separated into the aqueous phase 3 and the organic phase 4, and a liquid introduction section 14 for introducing the mixed liquid 5 into the column. In this embodiment, the liquid introduction section 14 is connected to the side of the column 12 arranged in an upright state. In this embodiment, the connection position of the liquid introduction section 14 to the side of the column 12 is the introduction position Xc of the mixed liquid into the column of the liquid introduction section 14. In the present invention, the organic phase 4 may have a larger or smaller specific gravity than the aqueous phase 3, but it is preferable to use one with a smaller specific gravity in terms of ease of selection of an organic solvent and less power required.

[0016] As shown in FIG. 1, the liquid introduction section 14 is provided with a pipe connecting the liquid mixing section 20 and the column 12. The liquid mixing section 20 has a container 21 in which the aqueous phase 3 and the organic phase 4 are mixed, and a stirring means 13 arranged in the container 21. The stirring means 13 is composed of a stirring blade 15 and a rotating shaft 16 to which the stirring blade 15 is attached. One end of the rotating shaft 16 is connected to a motor 19 that rotates the rotating shaft 16 around its axis. In this embodiment, the mixed liquid 5 obtained by stirring and mixing the aqueous phase 3 and the organic phase 4 by the stirring means 13 is introduced into the column 12 through the liquid introduction section 14, so that the contact efficiency between the aqueous phase 3 and the organic phase 4 is good. As a result, the solvent extraction apparatus 10 of this embodiment has excellent element separation efficiency. Instead of or in addition to the stirring means 13, the aqueous phase 3 and the organic phase 4 may be mixed by pressure-feeding using a pump. Alternatively, a static mixing method such as an in-line mixer or a static mixer may be used, or the aqueous phase 3 and the organic phase 4 may be mixed by generating bubbles or an emulsion using a perforated plate, a Raschig ring (a product of Raschig Co., Ltd.), a spray nozzle, or the like.

[0017] A vessel 21 (liquid mixing section 20) in which the stirring means 13 is disposed is connected to the liquid introduction section 14, and one end of an organic phase intake pipe 18 and one end of an aqueous phase intake pipe 17 are connected to the vessel 21. The organic phase 4 in the organic phase intake pipe 18 and the aqueous phase 3 in the aqueous phase intake pipe 17 are each configured to be pumped toward the liquid mixing section 20 by a pump (not shown). As these pumps, any pump used in this technical field can be used without any particular limitation. With the above structure, the organic phase 4 and the aqueous phase 5 join together in the vessel 21 of the liquid mixing section 20, are stirred and mixed by the stirring blade 15, and are introduced into the column 12 through the liquid introduction section 14. 1, a confluence pipe for the aqueous phase and the organic phase may be connected to the liquid inlet section 14, and an organic phase intake pipe and an aqueous phase intake pipe may be connected to the end of the confluence pipe opposite the liquid inlet section 14, so that the organic phase 4 and the aqueous phase 3 flow into the liquid mixing section 20 through the confluence pipe. In this case, in this embodiment, the aqueous phase 3 and the organic phase 4 are previously merged in the confluence pipe, and the resulting mixed liquid is pumped and supplied to the liquid mixing section 20, so that the aqueous phase 3 and the organic phase 4 can be sufficiently mixed.

[0018] As shown in FIG. 2, the mixed liquid 5 introduced into the column 12 through the liquid introduction part 14 is separated into the aqueous phase 3 and the organic phase 4 by moving up and down in the column 12 based on the specific gravity. The mixed liquid 5 immediately after being introduced into the column 12 may be in an emulsion state. Unlike the technology described in Patent Document 3, the solvent extraction apparatus 10 of this embodiment can obtain sufficient phase separation performance by forming the column 12 into a specific shape and adjusting the height of the liquid introduction position Xc (see FIG. 1) of the liquid introduction part 14 without providing a reaction tank between the liquid mixing part and the stationary part. As shown in FIG. 1, the liquid introduction position Xc of the liquid introduction part 14 is located above the lower end 12A of the column 12.

[0019] In this embodiment, the liquid mixing section 20 and the column 12 are connected through the liquid introduction section 14, which is a pipe. In other words, the liquid mixing section 20 and the column 12 are configured as separate containers. The mixed liquid in the liquid mixing section 20 is pumped through the liquid introduction section 14 and introduced into the column 12. With this configuration, the mixed liquid 5 in a uniform mixed state is stably supplied to the column 12, enabling stable separation and extraction. In addition, there is also the advantage that the installation area of ​​the solvent extraction apparatus 10 can be reduced.

[0020] The ratio of the liquid delivery rates (L / min) of the organic phase 4 and the aqueous phase 3 supplied to the liquid mixing section 20 is not limited, but can be freely selected within the range of 100:10 to 200 for the organic phase 4 and the aqueous phase 3, expressed as a volume ratio, for example.

[0021] The column 12 has an aqueous phase outlet 47A and an organic phase outlet 48A through which the aqueous phase 3 and the organic phase 4 separated from the mixed liquid 5 are respectively discharged. As shown in Fig. 1, in this embodiment, the aqueous phase outlet 47A is located at or near the lower end 12A of the column 12, and the organic phase outlet 48A is located at or near the upper end 12B of the column 12. In the example shown in Fig. 1, an organic phase extraction pipe 48 is connected to the upper end 12B side of the column 12, and an aqueous phase extraction pipe 47 is connected to the lower end 12A side of the column 12. In the example shown in Fig. 1, the organic phase extraction pipe 48 is connected to the column 12 at an organic phase outlet 48A, and the aqueous phase extraction pipe 47 is connected to the column 12 at an aqueous phase outlet 47A. In the example shown in Fig. 1, the organic phase outlet 48A is located at the same position as or lower than the upper end 12B of the column 12 in the vertical direction X, and the aqueous phase outlet 47A is located at the same position as or higher than the lower end 12A of the column 12 in the vertical direction.

[0022] The mixed liquid 5 introduced from the liquid mixing section 20 into the column 12 is separated into an organic phase 4 flowing upward in the column 12 and an aqueous phase 3 flowing downward. The organic phase 4 is introduced from an organic phase outlet 48A into an organic phase removal pipe 48 and removed from the column 12. The aqueous phase 3 is introduced from an aqueous phase outlet 47A into an aqueous phase removal pipe 47 and removed from the column 12.

[0023] In this embodiment, the column 12 is installed so that the vertical direction X and the central axis K are parallel to each other. The column 12 is cylindrical. As shown in FIG. 2, in this embodiment, the height difference L between the aqueous phase outlet 47A and the organic phase outlet 48A in the column 12 (hereinafter, simply referred to as "the height difference L of the column 12") refers to the distance in the vertical direction X between the uppermost end of the aqueous phase outlet 47A and the lowermost end of the organic phase outlet 48A. In addition, the cross-sectional area C of the column 12 refers to the area of ​​a portion in which liquid may exist in a cross section of the column 12 along a direction perpendicular to the X direction. Specifically, it refers to the area of ​​a hollow portion surrounded by the inner wall of the column 12.

[0024] The cross-sectional shape of the column 12 is not particularly limited, and may be, for example, a rectangle, a triangle, a circle, or an ellipse. If the cross-sectional shape of the column 12 is, for example, a polygon, gaps are unlikely to occur between adjacent columns 12 when a plurality of columns 12 are installed, and the installation area can be effectively reduced. In particular, a rectangular cross-sectional shape of the column 12 is preferable because it is easy to increase the volume of the column while suppressing the space used for installing the solvent extraction apparatus 10.

[0025] The cross-sectional area C of the column 12 may or may not be constant. When the cross-sectional area C of the column 12 is not constant along the X direction, the average value of the cross-sectional areas of the entire column 12 is used as the cross-sectional area C. Specifically, the cross-sectional areas C of nine points located at intervals of (1 / 10)L along the X direction from the organic phase outlet 48A to the aqueous phase outlet 47A of the column 12 are measured, and the average value is used.

[0026] The column 12 is preferably cylindrical with a substantially constant cross-sectional area C, or has a cylindrical shape with a part including the liquid introduction position Xc (specifically, a part in the vertical direction X including the introduction position Xc) that is wider (with a larger cross-sectional area C, see, for example, FIG. 3 described later), in terms of increasing the efficiency of oil-water separation by the column 12 and removing remaining air bubbles. In this specification, "having a substantially constant cross-sectional area C" means that, when the minimum value of the cross-sectional area C is Cm, the value of (C-Cm) / Cm×100 is 10% or less over the entire height difference L of the column 12. The widened portion does not have to have a substantially constant cross-sectional area C. For example, the widened portion may have a cross-sectional area C that is within a range of 1 to 3 times the minimum cross-sectional area Cm of the remaining portions with substantially constant cross-sectional areas.

[0027] The shape of the column 12 can be defined by the cross-sectional area C of the column 12 and the height difference L of the column 12. The column 12 is defined by the ratio of the cross-sectional area C to the square of the height difference L, that is, "C / L 2 The ratio of the column cross-sectional area C / (column height difference L×column height difference L) is preferably less than 1.0, more preferably 0.3 or less, even more preferably 0.1 or less, and even more preferably 0.01 or less. The smaller this value is below 1.0, the longer the column becomes, and the better the phase separation between the organic phase 4 and the aqueous phase 3 becomes. 2 The smaller the value, the better, but it is preferably 0.001 or more in terms of the balance between the ascending velocity of the organic phase liquid and the settling velocity of the aqueous phase liquid, and more preferably 0.005 or more.

[0028] Such a solvent extraction apparatus 10 differs from the conventional stationary column described in Patent Document 3 in that the organic phase 4 and the aqueous phase 3 do not flow in from above and below the partition plate separating the reaction vessel.

[0029] Another preferred feature of the solvent extraction apparatus 10 of this embodiment is that the mixed liquid 5 of the organic phase 4 and the aqueous phase 3 is introduced from a position below the central position Xr (a position that vertically bisects the height difference L) in the vertical direction X between the organic phase outlet 48A and the aqueous phase outlet 47A in the column 12. For example, as described above, in this embodiment, the liquid introduction part 14 is connected to the side of the column 12 in the upright state, and it is preferable that the liquid introduction position Xc of the liquid introduction part 14 is below the central position Xr of the column 12. As a result, in this embodiment, for example, as shown in FIG. 2, the length D in the vertical direction X from the aqueous phase outlet 47A to the liquid introduction position Xc is smaller than the length M in the vertical direction X from the aqueous phase outlet 47A to the central position Xr. With this configuration, it is possible to effectively reduce the aqueous phase (water droplets) that is entrained in the organic phase 4 rising in the column 12, and to maximize the phase separation effect of the column 12. The introduction position Xc of the mixed liquid refers to the height position of the introduction part of the mixed liquid, but when the introduction part of the mixed liquid has a certain width rather than being a single point in the vertical direction X, the center position of that width is referred to as the liquid introduction position Xc. For example, in the example shown in Figure 1, the liquid introduction position Xc is located at the center in the vertical direction X of liquid inlet 14A, which is the connection part of liquid introduction part 14 with the side surface of column 12.

[0030] From the viewpoint of achieving better phase separation between the aqueous phase 3 and the organic phase 4, it is preferable that the ratio (D / L) of the distance D (see FIG. 2) along the X direction between the liquid introduction position Xc of the liquid introduction part 14 and the lower end 12A of the column 12 to the height difference L of the column 12 is 0.2 or more and less than 0.5. By introducing the mixed liquid from this position, the separation ability between the aqueous phase 3 and the organic phase 4 is significantly improved. The ratio (D / L) of 0.25 or more and 0.45 or less is preferable because separation of water droplets in the organic phase 4 is particularly good, and 0.25 or more and 0.40 or less is particularly preferable.

[0031] In this embodiment, it is preferable that the interface between the aqueous phase 3 and the organic phase 4 is located below the liquid introduction position Xc of the liquid introduction part 14 when the mixed liquid 5 is introduced into the column 12. With this configuration, the rise of the organic phase 4 in the column 12 starts from a position lower than the liquid introduction position Xc, so that the moving distance of the organic phase 4 can be increased. Normally, when the organic phase 4 and the aqueous phase 3 are separated, the aqueous phase is likely to be mixed into the organic phase 4. Therefore, by adjusting the interface position Xi, the phase separation performance in this embodiment is further improved. As described above, during introduction of the mixed liquid 5 into the column 12, the aqueous phase 3 and the organic phase 4 are usually in a mixed state near the liquid introduction position Xc of the liquid introduction part 14 in the column 12, making it difficult to clearly see the interface Xi. In such a case, the introduction of the mixed liquid 5 into the column 12 can be temporarily interrupted to make the interface Xi (see FIG. 2) visible. When a transparent container is used as the column 12, the position of the interface Xi can be easily determined. However, when an opaque container is used as the column 12, the position of the interface Xi can be determined by measuring the height of the interface with a level meter attached to the side of the column 12 or by sampling the liquid from the top of the column 12 with a glass tube or the like.

[0032] When the interface Xi is lower than the liquid introduction position Xc, the distance Di between the interface Xi and the liquid introduction position Xc along the X direction is determined by the linear velocity of the mixed liquid and the cross-sectional area of ​​the column, but is preferably 2.5 cm or more, and particularly preferably 3 cm or more in order to improve phase separation. In Examples 1 and 2 described below, the distance Di was 4 cm, and in other Examples it was 3 to 5 cm. In Comparative Examples 3 and 4 it was 2 cm, and in other Comparative Examples it was equal to or less than the Examples.

[0033] Examples of methods for positioning the interface Xi below the liquid introduction position Xc include (1) a method of adjusting the interface position by adjusting the liquid withdrawal speed from the column 12 using a pump or the like for each of the aqueous phase withdrawal pipe 47 connected to the lower end 12A of the column 12 and / or the organic phase withdrawal pipe 48 connected to the upper end 12B of the column 12; (2) a method of adjusting the interface by adjusting the head pressure of each of the aqueous phase 3 and the organic phase 4; and (3) a method of adjusting the liquid delivery speed to the mixing section 20 of the aqueous phase 3 and the organic phase 4. In particular, the method (2) of adjusting the interface by adjusting the head pressure of each of the aqueous phase 3 and the organic phase 4 is preferred in that it is easy to improve extraction efficiency and phase separation efficiency.

[0034] As shown in FIG. 2, when the length from the liquid introduction position Xc of the liquid introduction part 14 to the bottom end of the organic phase outlet 48A of the column 12 is U, the ratio of the column cross-sectional area C to the square value of U (C / U 2 ) is preferably less than 3.0. 2 In addition to keeping the ratio of C / U below a specified upper limit, 2 By setting the upper limit of the ratio (C / U) to a predetermined value, the length of the organic phase 4 from the liquid introduction part 14 to the organic phase outlet 48A of the column 12 can be secured, so that the separation of the organic phase 4 and the aqueous phase 3 becomes more favorable. 2 ) is preferably 1.0 or less, more preferably 0.5 or less. 2 ) is preferably 0.01 or more in that the solvent extraction time can be reduced and production costs can be easily reduced, and is more preferably 0.02 or more.

[0035] In the column 12 of the solvent extraction apparatus 10 according to this embodiment, it is preferable that the linear velocity (velocity in the X direction) corresponding to the flow velocity of the liquid flowing in the column 12 is equal to or less than a predetermined value. If the flow velocity in the column 12 is too fast, it will hinder the falling separation of the aqueous phase 3 to be separated. The volume ratio of the aqueous phase 3 and the organic phase 4 flowing into the liquid mixing section 20 per unit time is r:1, and the flow rate of the mixed liquid into the column 12 is T (cm 3 / min, and the column cross-sectional area is C (cm2 ), the linear velocity of the organic phase 4 can be calculated from the following formula: Linear velocity of organic phase 4 (cm / min) = T / C × [1 / (r+1)] Similarly, the linear velocity of the aqueous phase 3 can be calculated from the following equation: Linear velocity of aqueous phase 3 (cm / min) = T / C × [r / (r+1)]

[0036] For example, if the inner diameter of column 12 is 5 cm, the column cross-sectional area C is 19.6 cm 2 (=2.5×2.5×3.14), the volume ratio of the aqueous phase 3 and the organic phase 4 per unit time flowing into the liquid mixing section 20 is 1:1, and the flow rate of the mixed liquid 5 into the column 12 is 1 L / min., the flow rate is 500 cm 3 Since the linear velocity of the organic phase 4 is calculated to be 25.5 cm / min (=500 / 19.6), the linear velocity of the organic phase 4 is calculated to be 25.5 cm / min (=500 / 19.6). Setting the linear velocity of the organic phase 4 to 50 cm / min or less has the advantage that the drop of the aqueous phase 3 (water droplets) in the organic phase 4 is less likely to be hindered due to an excessively fast liquid flow. From this viewpoint, the linear velocity of the organic phase 4 is more preferably 30 cm / min or less, and further preferably 15 cm / min or less. The linear velocity of the organic phase 4 is preferably 1 cm / min or more, since the time required for phase separation can be shortened and production costs are favorable.

[0037] Similarly, from the viewpoint of preventing the floating of the organic phase 4 (oil droplets) in the aqueous phase 3 from being hindered, the linear velocity of the aqueous phase 3 is, for example, preferably 50 cm / min or less, more preferably 30 cm / min or less, and even more preferably 15 cm / min or less. The linear velocity of the aqueous phase 3 is preferably 2 cm / min or more, since this can shorten the time required for phase separation and improves production costs.

[0038] During separation of the aqueous phase 3 and the organic phase 4, the aqueous phase 3 is usually likely to be mixed into the organic phase 4, and therefore, of the linear velocities, the linear velocity of the organic phase 4 is particularly important.

[0039] Furthermore, although there is no particular limitation on the internal structure of the column 12, a fluid inclusion may be installed near the liquid introduction position Xc of the liquid introduction part 14, if necessary. For example, a perforated plate or an inclined plate may be installed in the column 12 to increase the contact efficiency between the organic phase 4 and the aqueous phase 3. Also, a structure for suppressing the flow of the mixed liquid may be provided in the column 12. It is preferable that these inclusions are located at least above the liquid introduction position Xc in the column 12, in order to reduce the linear velocity of the organic phase 4 to facilitate better phase separation and to aggregate water droplets to increase the particle size and speed up the settling speed.

[0040] As described above, in the solvent extraction apparatus 10 of this embodiment, the organic phase 4 moves upward in the column 12, and the aqueous phase 3 moves downward in the separation column 12, thereby separating the two phases. The organic phase 4 is discharged to the outside of the system from an organic phase outlet 48A located at or near the upper end 12B of the column 12. The aqueous phase 3 is discharged to the outside of the system from an aqueous phase outlet 47A located at or near the lower end 12A.

[0041] Hereinafter, further another embodiment will be described. In the following description, the same components as those in the embodiment of Fig. 1 are designated by the same reference numerals and their description will be omitted, and the differences from the embodiment of Fig. 1 will be mainly described. For the sake of convenience in describing the liquid introduction position, Fig. 3 and Fig. 4 show a state in which a mixed liquid is introduced into an empty column. In the solvent extraction apparatus 110 shown in FIG. 3, the column 112 is cylindrical and has a shape in which a part in the vertical direction X including the liquid introduction position Xc (a part indicated by reference symbol 12W in FIG. 3) is wider. In the embodiment shown in FIG. 3, the liquid introduction section 114 is installed inside the column 112, not on the side of the column 112. Specifically, the liquid introduction section 114 is composed of a liquid jetting section 114A installed in the column 112 and having a plurality of liquid jetting ports 115, and a pipe 114B that connects the liquid jetting section 114A to a liquid mixing section outside the column 112 and introduces the mixed liquid from the liquid mixing section to the liquid jetting section 114A. The liquid introduction position Xc is the position of the liquid jetting port 115 of the liquid jetting section 114A (specifically, the center position in the vertical direction X of the liquid jetting port 115). In the example shown in FIG. 3, the pipe 114B is fixed to the bottom surface of the column and arranged to extend in the vertical direction X. 4, the liquid introduction part 214 is also installed inside the column 212, not on the side thereof. In this embodiment, the liquid introduction part 214, which is a pipe, is fixed to the upper surface of the column and extends downward in the vertical direction X. The mixed liquid is introduced into the column 212 from an opening 214A at the lower end of the liquid introduction part 214, which is a pipe, and the position of this opening 214A (specifically, the center position of the opening 214A in the vertical direction X) is the liquid introduction position Xc.

[0042] In addition, the solvent extraction apparatus 10 of the present invention may be, for example, a multi-stage solvent extraction apparatus in which a plurality of columns are arranged in parallel. For example, the aqueous phase separated in the Nth column may be introduced into a column adjacent to the N+1th stage together with a mixed liquid obtained by mixing the aqueous phase separated in the N+2th column, and separated. A multi-stage solvent extraction may be performed in which the aqueous phase separated in the Nth column is introduced into a column adjacent to the N-1th stage together with a mixed liquid obtained by mixing the aqueous phase separated in the N-2th column, and separated. According to such a multi-stage solvent extraction apparatus, the organic phase and the aqueous phase are separated well, and it is possible to precisely separate a plurality of ions contained in the aqueous phase. Moreover, in this type of solvent extraction apparatus, even if it is multi-stage, the installation area and volume can be reduced, and the exposed area of ​​the organic phase 4 can be reduced sufficiently.

[0043] The solvent extraction apparatus of each embodiment described above in the present invention is preferably used for a solvent extraction method, which is a method for separating metal elements by contacting an aqueous phase consisting of an aqueous solution containing the metal elements to be separated with an organic phase consisting of a metal extractant for extracting specific metal elements and an organic solvent for diluting the metal extractant, thereby extracting the metal elements into the metal extractant. In the solvent extraction method, the solvent extraction apparatus of the embodiment can be used in a method for separating two or more types of ions. In this separation method, an aqueous phase 3 contains two or more types of ions to be separated. An organic phase 4 contains an extractant capable of forming a complex with at least one of the two or more types of ions. The two or more types of ions are preferably two or more types of metal ions of different elements, and more preferably two or more types of rare earth elements of different elements.

[0044] Examples of the metal extractant used in the present invention include tributyl phosphate (TBP), carboxylic acid (versatic acid 10), phosphoric acid esters, phosphonic acid compounds, and phosphinic acid compounds. For example, examples of phosphoric acid esters include di-2-ethylhexyl phosphoric acid (D2EHPA). Examples of phosphonic acid compounds include 2-ethylhexyl phosphoric acid mono-2-ethylhexyl ester (PC-88A: product name manufactured by Daihachi Chemical Industry Co., Ltd.). Examples of phosphinic acid compounds include bis(2,4,4-trimethylpentyl)phosphoric acid (Cyanex272: product name manufactured by CYTEC Industries).

[0045] The organic solvent forming the organic phase in the solvent extraction of the reaction solvent used here may be any of naphthenic, paraffinic and aromatic, and specific examples thereof include toluene, xylene, hexane, isododecane, kerosene and higher alcohols (for example, linear alcohols having 5 to 8 carbon atoms).

[0046] The present invention is not limited to this embodiment. For example, when the organic phase moves downward and the aqueous phase moves upward, it goes without saying that the positions of the organic phase outlet 48A and the aqueous phase outlet 47A in Fig. 2 are upside down. Also, although the organic phase outlet 48A and the aqueous phase outlet 47A are oriented horizontally in Figs. 1 and 2, it goes without saying that they may be oriented vertically. EXAMPLES

[0047] Example 1 In this example, rare earth metal ions were extracted using a solvent extraction apparatus 10 shown in FIGS. A heavy specific gravity liquid (aqueous phase) was prepared by dissolving terbium salt and dysprosium salt in 120L of 12% by mass hydrochloric acid solution so that the concentration of terbium was 56g / L and the concentration of dysprosium was 42g / L. Separately from this operation, the terbium salt (56g / L of the light specific gravity liquid to be prepared) and dysprosium salt (42g / L) dissolved in hydrochloric acid were adjusted to pH 3, and this adjusted liquid was mixed and contacted with a solution in which 20% by mass of an extractant (PC-88A) was dissolved in kerosene, and all of the terbium salt and dysprosium salt were added to the oil phase to prepare 120L of a light specific gravity liquid (organic phase). Both liquids were constantly kept in a state of being stirred and mixed. The above-mentioned stirred mixture was introduced into the stationary column, which was made of a PVC pipe with an inner diameter of 10 cm and a total length of 50 cm, from a position 20 cm from the bottom. The stirred mixture was introduced by a metering pump at a flow rate of 2 L / min, i.e., a linear velocity of the organic phase of 12.7 cm / min (volume ratio of the organic phase to the total liquid was 0.5). This stationary column was designed so that the organic phase was discharged from the top and the aqueous phase was discharged from the bottom, and the total amount of the liquid introduced and the total amount of the liquid discharged were always the same, and circulated. 15 minutes after the start of circulation, the aqueous phase and the organic phase were each sampled in a measuring cylinder and left to stand for separation, and the content ratio of the different phase liquids contained in those phases was measured. As a result, the heavy specific gravity liquid (aqueous phase) did not contain any light specific gravity liquid (organic phase). On the other hand, the light specific gravity liquid (organic phase) contained 0.6 mass% of heavy specific gravity liquid (aqueous phase). Based on the content of the aqueous phase in the organic phase and the presence or absence of air bubbles, the following evaluation was made. AA: The content of the aqueous phase in the organic phase is less than 1.0% by mass, and there are no air bubbles in the organic phase. A: The content of the aqueous phase in the organic phase is less than 1.0% by mass, and there is almost no adhesion of air bubbles in the organic phase. B: The content of the aqueous phase in the organic phase is 1.0% by mass or more.

[0048] The presence of an aqueous phase in the organic phase indicates incomplete separation, but when testing was conducted using a mixer-settler type device of similar volume, which is known as a common solvent extraction device, the amount of adhering water was 1.0 mass%, so it is determined that if the amount of adhering water is less than 1.0 mass%, separation is better than with the current device. In Table 1, the linear velocity is shown as the value obtained by dividing the amount of the mixed liquid delivered by the cross-sectional area of ​​the column.

[0049] (Examples 2 to 7, Comparative Examples 1 to 6) The column inner diameter R, the column height difference L, the distance D between the liquid introduction position Xc of the introduction part of the aqueous-organic phase mixture in the column and the aqueous phase outlet, and the liquid flow rate (linear velocity) of the column 12 were changed as shown in Table 1, and the organic phase liquid discharged from the top of the column was collected and the amount of attached water contained therein was measured. The results are shown in Table 1. In addition, in Examples 2 to 7 and Comparative Examples 1 to 3 and 6, the heavy specific gravity liquid (aqueous phase) did not contain the light specific gravity liquid (organic phase) as in Example 1. In Comparative Examples 4 and 5, the heavy specific gravity liquid (aqueous phase) was confirmed to be mixed with the light specific gravity liquid (organic phase). Specifically, in Comparative Example 4, the aqueous phase discharge contained 15 mass % of the organic phase. In Comparative Example 5, the aqueous phase discharge also contained 6.2 mass % of the organic phase.

[0050] [Table 1]

[0051] As is clear from the evaluation results of the above examples and comparative examples, the solvent extraction apparatus 10 of the present invention has a compact configuration, yet provides better phase separation between the organic phase and the aqueous phase than the conventional mixer-settler, making it possible to provide an extremely high-performance solvent extraction apparatus. [Explanation of symbols]

[0052] 3 Water phase 4 Organic phase 5 Mixed liquid 10 Solvent Extraction Apparatus 12 Columns 14 Liquid introduction section 47A Water phase outlet 48A Organic phase outlet 12B Column top L Height difference L between the lower end of the organic phase outlet 48A and the upper end of the aqueous phase outlet 47A C column cross-sectional area Xc Liquid introduction position of liquid introduction part

Claims

1. a column in an upright position into which a mixed liquid obtained by mixing an aqueous phase and an organic phase is introduced and into which the mixed liquid is separated into the aqueous phase and the organic phase, and a liquid introduction part for introducing the mixed liquid into the column; The column has an aqueous phase outlet and an organic phase outlet through which the aqueous phase and the organic phase separated from the mixed liquid are discharged, respectively, and a ratio of a cross-sectional area C of the column to a square value of a height difference L between the aqueous phase outlet and the organic phase outlet (C / L ２ ) is less than 1.0, and the column has a liquid introduction position of the liquid introduction part that is lower than a center position in a vertical direction between the aqueous phase outlet and the organic phase outlet, A solvent extraction apparatus, wherein a length D from the liquid introduction position to the aqueous phase discharge outlet in a vertical direction is 0.25 or more and less than 0.5 of the height difference L.

2. The ratio of the column cross-sectional area C to the square of the length U from the liquid introduction position to the organic phase outlet (C / U ２ 2. The solvent extraction apparatus of claim 1, wherein the β- 3. The solvent extraction apparatus according to claim 1, wherein a ratio (C / U 2 ) of the column cross-sectional area C to the square of the length U from the liquid introduction position to the organic phase outlet is 0.5 or less.

4. A solvent extraction apparatus as described in claim 3, wherein the liquid introduction portion is provided on the side of the column.

5. 3. The solvent extraction apparatus according to claim 1, wherein the column is configured such that, when the mixed liquid is introduced into the column, an interface between the aqueous phase and the organic phase is located below the liquid introduction position.

6. 3. The solvent extraction apparatus according to claim 1, wherein the linear velocity of the organic phase in the column is 50 cm / min or less.

7. 3. The solvent extraction apparatus according to claim 1, wherein a fluid inclusion is provided in the column at least above the liquid introduction position.

8. A method for separating at least one ion from two or more ions using a solvent extraction apparatus having an upright column into which a mixed liquid obtained by mixing an aqueous phase and an organic phase is introduced and into which the mixed liquid is separated into the aqueous phase and the organic phase, and a liquid inlet portion for introducing the mixed liquid into the column, comprising: the aqueous phase contains two or more ions to be separated; the organic phase comprises an extractant capable of complexing at least one of the two or more ions; In the solvent extraction apparatus, The column has an aqueous phase outlet and an organic phase outlet through which the aqueous phase and the organic phase separated from the mixed liquid are discharged, respectively, and a ratio of a cross-sectional area C of the column to a square value of a height difference L between the aqueous phase outlet and the organic phase outlet (C / L ２ ) is less than 1.0, and the column has a liquid introduction position of the liquid introduction part that is lower than a center position in a vertical direction between the aqueous phase outlet and the organic phase outlet, A method for separating ions, wherein a length D from the liquid introduction position to the aqueous phase outlet in a vertical direction is 0.25 or more and less than 0.5 of the height difference L.

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