JP5305382B2 - Counterflow emulsion flow continuous liquid-liquid extraction device - Google Patents

Description

  The present invention continuously develops an emulsion state without using mechanical external force such as stirring and shaking, and uses an emulsion state flow (referred to as emulsion flow) to extract an aqueous phase and an aqueous phase. The present invention relates to a continuous liquid-liquid extraction device that uses two-liquid phase contact by emulsion flow to quickly complete efficient contact with a solvent phase.

  The liquid-liquid extraction method (solvent extraction method), which extracts the target component contained in the aqueous solution into a solvent (such as an organic solvent) that does not mix with the water containing the extractant, is used for metal purification, nuclear fuel reprocessing, and hazardousness in wastewater. It is widely used in various industries such as removal of components and recycling by separation and recovery of valuable substances. In addition to the liquid-liquid extraction method, there is a solid extraction method that uses a solid such as a resin packed in a column or the like as a method for extracting components in an aqueous solution. The liquid-liquid extraction method is said to be less convenient than the solid extraction method, but is superior to the solid extraction method in terms of the size and speed of extraction capacity. In order to efficiently perform liquid-liquid extraction of the target component in the aqueous solution, it is necessary to increase the area of the liquid-liquid interface by well mixing the aqueous phase and the extraction solvent phase to promote the interfacial reaction. Therefore, normally, stirring and vibration (shaking) are continuously performed to maintain the state of the emulsion (water and organic solvent are mixed and milky) for a sufficient period of time. Allow the mass transfer between them to reach equilibrium.

As an apparatus for continuously extracting a component in an aqueous phase into an extraction solvent phase while introducing a constant flow rate of an aqueous phase and an extraction solvent phase, a mixer setra using a stirrer is widely used. In addition, relatively new continuous liquid-liquid extraction devices (see Patent Document 1) such as a pulse column that uses vibration generated by pulse generation for droplet dispersion and a centrifugal extractor that performs dispersion / phase separation using centrifugal force are also available, such as nuclear power. Are used (or are being used). In particular, the centrifugal extractor is excellent in contact efficiency and phase separation efficiency of two liquid phases, and has high performance and compactness. Therefore, it is expected to be applied to a technique for reprocessing spent nuclear fuel.
JP 09-085120 A

  However, both devices are common in that two liquid phase mixing is performed by applying mechanical external force (stirring, vibration, etc.) continuously or intermittently. This makes it difficult to handle and running. Demerits such as high costs, maintenance costs, device manufacturing costs (initial costs), and safety concerns arise. For example, 1) Large energy burden required to generate mechanical external force, 2) Load / fatigue of drive unit that generates mechanical external force, 3) Long adjustment work required at the start of operation, 4) Friction or static electricity at drive unit There are dangers of ignition, 5) high-strength and expensive materials required for the drive unit, 6) noise associated with stirring, vibration, or high-speed rotation, and 7) anxiety in ensuring safety during an earthquake.

  On the other hand, the recently developed emulsion flow can develop an emulsion state (emulsion) of two-liquid phase mixing only by liquid feeding, and unlike a conventional liquid-liquid device, it does not require mechanical external force (special (Application No. 2007-136496: Unpublished). This eliminates all the disadvantages of the conventional apparatus as described above. Emulsion flow is an epoch-making technique capable of performing liquid-liquid extraction (solvent extraction) with the same simplicity as column-type solid-liquid extraction used by filling a column with a solid such as a resin. In other words, in addition to the advantages (large extraction capacity and quickness) of conventional solvent extraction devices (such as mixer-settler), the extraction device using emulsion flow has the advantages (ease of handling, low power) of the column type solid-liquid extractor. Together with running costs). Large extraction capacity and rapidity could not be realized with a column type solid-liquid extractor, and handling and low running cost could not be realized with a conventional solvent extraction apparatus.

  Although the emulsion flow is an epoch-making technique as described above, it has some problems. First, in the conventional single-flow method, it is difficult to generate a fine-grained emulsion flow and there is some unevenness in the emulsion, so it is not easy to obtain an extraction rate exceeding 90%. In the single flow method, it is difficult to keep the emulsion flow stable in a wide area, and it is difficult to increase the size of the apparatus. In addition, there was a fatal weakness that the pores of the head part that makes the aqueous solution finer and ejected are clogged by particle components. In many cases, particle components are mixed as a suspension in an aqueous solution, and the problem of clogging of the head portion is a major problem in emulsion flow. Note that the single-flow method refers to a method in which the extraction solvent is not sent or refined, and only the aqueous solution is refined at the head portion and ejected into the extraction solvent.

  The object of the present invention is to solve the disadvantages of a single-flow emulsion flow (initial type), 1) to obtain an extraction rate exceeding 90% by generating a better quality emulsion flow, and 2) to obtain an emulsion flow over a wide range. 3) Provided is a countercurrent emulsion flow continuous liquid-liquid extraction device that can easily increase the size of the device by maintaining a stable flow rate, and 3) can avoid clogging of holes in the head portion due to particle components in an aqueous solution. There is.

  As a result of intensive studies to solve the above problems, the present inventor has succeeded in significantly improving the extraction rate and increasing the size of the apparatus by applying the countercurrent method. In addition, by using a countercurrent system in which only the extraction solvent phase is refined and circulated, clogging of the head portion has been successfully avoided.

  A counter-current emulsion flow continuous liquid-liquid extraction device according to one aspect of the present invention includes a first head unit that ejects an aqueous phase, and a first head unit that ejects an extraction solvent phase that is disposed to face the first head unit. The apparatus main body is composed of two head parts, a column part where an emulsion flow is generated, an upper phase separation part installed above the column part, and a lower phase separation part installed below, and a liquid feed pump.

  By adopting the counter-flow system, the emulsion flow is more stabilized and a finer emulsion flow can be generated as compared with a single-flow apparatus. In addition, the counter-current system in which the extraction solvent is refined and circulated enables stable operation without being affected by the particle components. This utilizes the property that the particle component in the aqueous solution is not distributed to the extraction solvent at all. That is, when the extraction solvent phase is miniaturized, there is no fear that the head portion (second head portion) is clogged. In the countercurrent emulsion flow, it was also found that the structure of the second head part determines the quality of the emulsion flow, and the structure of the first head part for ejecting the aqueous phase is not important. That is, for the first head part, even if the structure allows the particle component to pass sufficiently (structure that does not refine the aqueous phase), there is no significant effect on the extraction rate. The present invention has been completed based on the above new findings.

  According to the present invention, quality improvement and stabilization of an emulsion that could not be obtained with a single-flow emulsion flow apparatus can be realized, and target components can be extracted at a higher extraction rate, and the apparatus can be easily enlarged. In addition, the use of the counterflow system can also solve the problem of clogging of the head part due to particle components such as suspension, which was a major weakness of the single-flow system emulsion flow apparatus.

  The countercurrent emulsion flow continuous liquid-liquid extraction apparatus according to the present invention will be described in detail below with reference to the drawings. First, refer to FIG. FIG. 1 shows a schematic configuration diagram of a countercurrent emulsion flow continuous liquid-liquid extraction apparatus of the present invention.

  In FIG. 1, the emulsion flow apparatus 10 is installed in the 1st head part 11 which ejects a water phase, the 2nd head part 12 which ejects a solvent phase, the column part 13 which an emulsion flow generate | occur | produces, and the upper part and the lower part of the column part. The apparatus main body is composed of a phase separation unit (upper phase separation unit 14 and lower phase separation unit 15) and a liquid feed pump 16 (one duplex unit or two single units). The head part does not necessarily need to be in contact with the liquid phase (aqueous phase, solvent phase, or emulsion mixed phase). A water sample in the reservoir 20 is sent to the emulsion flow device 10 via a conduit 21. The first head portion 11 is a cylinder whose both ends are open, a cylinder whose one end is covered with a sheet having a mesh of 1 μm to 5 mm or a hole, a cylinder which is closed at one end, its closed part or its periphery. A structure in which an appropriate number of holes having a diameter of 1 μm to 5 mm are formed in both of the parts, or a structure in which the perforated cylinder is further covered with a sheet having a hole of 1 μm to 1 mm or a hole, or 10 μm to 1 mm. It has a structure in which a porous body (for example, sintered glass) having a pore size is bonded to a cylinder. The second head portion has a structure similar to that of the first head portion, but the size of the hole or mesh of the second head portion is different from the size of the hole or mesh of the first head portion. May be.

  Next, the operation will be described. The aqueous solution from the reservoir 20 is fed into the extraction solvent through the cylinder that is the first head portion 11 of the emulsion flow device 10 by the liquid feeding pump 16 provided in the conduit 21 that connects the water sample reservoir 20 and the emulsion flow device 10. It spouts toward. At the same time, the extraction solvent is ejected through the cylinder that is the second head portion 12 of the apparatus so as to face the flow of the aqueous solution. Thereby, in the column part 13 of the emulsion flow apparatus 10, the flow (it calls an emulsion flow) which consists of an emulsion mixed phase of aqueous solution and an extraction solvent generate | occur | produces. FIG. 2 shows a state in which the emulsion flow is generated in the column portion 13. From FIG. 2, it can be seen that the aqueous phase and the extraction solvent phase are mixed to form an emulsion-specific emulsion state. When the emulsion mixed phase reaches the upper phase separation part 14 above the column part 13 or the lower phase separation part 15 below the column part 13, the state of the emulsion flow is released, and the water phase and the extraction solvent Phase separate into phases. 2 and 3, it can be seen that the emulsion flow has disappeared in the upper phase separation unit 14 and the lower phase separation unit 15. The extraction solvent phase gathers in the upper phase separation unit 14, and the aqueous phase gathers in the lower phase separation unit 15. The clean extraction solvent in the upper phase separation unit 14 is circulated through the second head unit 12. Moreover, the clean aqueous phase in the lower phase separation part 15 is taken out as waste water after processing. Some specific examples are shown below, but the present invention is not limited to these examples. For example, the head portions (11, 12) are not necessarily cylindrical, and may be square tubes, for example. Further, the shapes of the column portion 13 and the phase separation portions 14 and 15 are not necessarily cylindrical, and may be, for example, a quadrangular prism shape.

  Continuous extraction of ytterbium Yb (III) from aqueous nitric acid solution

A continuous extraction experiment of ytterbium Yb (III) from an aqueous nitric acid solution was performed using a countercurrent emulsion flow extraction apparatus 10 having a height of 70 cm shown in the photograph of FIG. The first head unit 11 has a hole of 38 holes (diameter 2 mm) around a polypropylene tube having a diameter of 1.5 cm and a length of 5 cm and one end closed, and further has a mesh of 70 μm around the hole. The structure is covered with a Teflon (registered trademark) sheet. The second head portion has a structure in which a sintered glass plate having a hole diameter of 40 μm is bonded to a cylinder. The upper phase separation unit 14 has a structure in which a container with a squeezed mouth is inserted above the column unit 13. The lower phase separation unit 15 has a structure in which a container having a diameter larger than that of the column unit 13 is coupled to the lower side of the column unit 13.

Using ytterbium Yb (III) as the metal ion and using bis (2-ethylhexyl) phosphate: DEHPA as the extractant, the relationship between the extraction rate of ytterbium Yb (III) and the amount of liquid fed was examined. The volume of the sample aqueous solution (aqueous phase) was 200 L, the volume of the extraction solvent phase was 2 L, and isooctane was used as the extraction solvent. The aqueous phase was adjusted to pH 2.0 by adding nitric acid, and the concentration of ytterbium Yb (III) in the aqueous phase was 6 × 10 ⁻⁶ M. The concentration of the extractant (DEHPA) in the extraction solvent phase was 1 × 10 ⁻² M.

  The experiment was carried out at a flow rate of 184 L / hour for the aqueous phase and 30 L / hour for the extraction solvent phase circulation (treatment capacity = 184 L / hour). A small amount of the drained aqueous phase was collected every 25 L, and the concentration of ytterbium Yb (III) was measured by an inductively coupled plasma mass spectrometer (ICP-MS). FIG. 5 shows the result. Regardless of the amount of liquid fed, the extraction rate of ytterbium Yb (III) was approximately 99%.

Continuous extraction of ytterbium Yb (III) in the presence of particulate components

  Using the same counter-current type emulsion flow extraction device used in (Example 1) (however, the structure of the first head part is different), continuous extraction experiments of ytterbium Yb (III) in the presence of particle components were conducted. went. The first head part 11 used at this time has a structure in which six holes having a diameter of 1.5 cm and a length of 5 cm and having a diameter of 5 cm and a closed end of a polypropylene tube are formed by six holes having a diameter of 4.8 mm (mesh). No sheet). The second head portion 12 is the same as in (Example 1), and has a structure in which a sintered glass plate having a hole diameter of 40 μm is bonded to a cylinder.

Using the above counter-current emulsion flow extraction device, fine particles of aluminum oxide Al ₂ O ₃ (particle size of 40 μm or less) are added to nitric acid aqueous solution (pH = 2.0) containing 6 × 10 ^-6 M ytterbium Yb (III). An experiment was conducted to extract ytterbium Yb (III) into isooctane containing 1 × 10 ⁻² M DEHPA from the coexisting aqueous solution. The volume of the sample aqueous solution (aqueous phase) was 200 L, and the volume of the extraction solvent phase was 2 L. The conditions are the same as in Example 1 except that aluminum oxide Al ₂ O ₃ fine particles coexist. The amount of aluminum oxide Al ₂ O ₃ coexisting is 0.02 M in terms of molar concentration.

  The experiment was conducted at a water flow rate of 237 L / hour and an extraction solvent phase circulation flow rate of 30 L / hour (processing capacity = 237 L / hour). A small amount of the drained aqueous phase was collected every 25 L, and the concentration of ytterbium Yb (III) was measured by ICP-MS. FIG. 6 shows the result. The extraction rate of ytterbium Yb (III) was approximately 97% regardless of the amount of liquid fed. That is, a sufficiently large extraction rate was obtained although it was slightly lower than the value of 99% in Example 1. Moreover, clogging did not occur at all in the first head portion 11 and the second head portion 12. In addition, the chain line of FIG. 6 shows the data of FIG.

  From the above, it was found that metal ions in an aqueous solution can be extracted without being affected by particle components even when a large amount of particle components coexist. It was also found that in the countercurrent emulsion flow, the structure of the second head portion 12 determines the quality of the emulsion flow, and the structure of the first head portion 11 is not important.

Time required to restart when the device is stopped

  Using the countercurrent emulsion flow extraction device (the structure of the first head portion 11 and the second head portion 12 is the same) used in (Example 2), the time required for restarting when the device was stopped was measured. After the apparatus that had been operating was once completely stopped, the time from when the liquid feed pump was started to when a stable emulsion flow was generated was measured again.

  The liquid feed pump was suddenly stopped while the apparatus was operating with the flow rate of the aqueous phase feed being 205 L / hour and the extraction solvent phase circulation being 30 L / hour. After 2 minutes, when the liquid feed pump was operated again under the same conditions, it was found that the emulsion flow reached a stable state in about 5 seconds. That is, it has been found that even if the liquid feeding is completely stopped, the operation can be resumed immediately without requiring adjustment work.

Extraction of uranium U from low-level radioactive liquid waste (simulated liquid waste)

Simulating the decontamination waste liquid (waste liquid generated by washing and removing the attached radioactive material with an acid) that accompanies the dismantling and removal of the equipment used in the nuclear facility, Al (8.4 × 10 ^-4 M), Ti (4.6 x 10 ^-4 M), Cr (1.1 x 10 ^-4 M), Fe (4.2 x 10 ^-2 M), Co (4.3 x 10 ^-3 M), Ni (6.1 x 10 ^-3 M), Cu A sulfuric acid aqueous solution (pH 0.5) containing (2.1 × 10 ⁻⁴ M), Mo (3.8 × 10 ⁻⁴ M), and U (5.0 × 10 ⁻⁷ M) was ^prepared , and the same structure as in (Example 2) The selective extraction of uranium U was tried using the counter-current type emulsion flow extraction device. Further, trioctylamine: TOA was used as the extractant, and isooctane containing 2.5 vol% (volume percent) of n-octanol was used as the extraction solvent. The TOA concentration was 0.3 M. The experiment was conducted at a water flow rate of 225 L / hour and an extraction solvent phase circulation flow rate of 30 L / hour (treatment capacity = 225 L / hour). As a result, among various metal ions coexisting at a high concentration, only a low concentration of uranium U could be extracted with a high extraction rate of approximately 97%. FIG. 7 shows the result. Although molybdenum Mo is also extracted in a small amount, molybdenum Mo, which is difficult to remove by precipitation, may be an object to be extracted.

  The counter-current emulsion flow continuous liquid-liquid extraction device of the present invention has a number of features that are advantageous in industrial use as compared with conventional continuous liquid-liquid extraction devices (mixer-settler, pulse column, centrifugal extractor, etc.). For example, from the viewpoint of cost effectiveness, it is important that the running cost and the maintenance cost are small. Unlike conventional liquid-liquid extraction devices, there is no need to continue to apply mechanical external force (stirring, vibration, etc.), so there is no power consumption. The only solution that requires driving force is the introduction of a non-powered system using the difference in elevation and the flow of drainage. In addition, being easy to handle is an important factor. For example, in a conventional continuous liquid-liquid extraction device, a long adjustment work is required at the start of operation, and fine adjustment is required even during steady operation. Moreover, such adjustment work requires skill. On the other hand, the emulsion flow continuous liquid-liquid extraction device is resistant to changes in the amount of liquid delivered and can be returned to the steady state in about 5 seconds even if the liquid delivery stops suddenly. No skill is required. This leads to a significant reduction in labor costs. In addition, it is also advantageous in planting that a simple structure is easy and inexpensive to manufacture, and the initial cost required for equipment is small, and that a compact device does not require a large space for installation. Furthermore, there is an advantage that the safety is higher than that of the existing apparatus. The device based on the emulsion flow is less susceptible to vibration (high earthquake resistance) like the column-type solid-liquid extractor, and the compact device can control the amount of organic solvent used. Safety is enhanced by the absence of frictional heat generated by continuously applying external force (stirring, vibration, etc.). In addition, the fact that the amount of waste liquid associated with adjustment work is very small and the noise is low is a highly valuable merit from the viewpoint of environmental considerations. The above advantages are due to the fact that an emulsion flow apparatus that does not use mechanical external force can realize efficient liquid-liquid extraction with the same simplicity as column-type solid-liquid extraction.

  From the above, it is expected that the countercurrent emulsion flow continuous liquid-liquid extraction device will be greatly utilized in many industries related to liquid-liquid extraction (metal purification technology, rare metal recycling technology, etc.). In addition, it can be expected that a new market for liquid-liquid extraction will be cultivated from the many excellent features that liquid-liquid extraction devices have not so far. For example, because of the features of the equipment using the principle of emulsion flow, such as safe, easy to handle, low cost, and compact, next-generation type continuous liquid-liquid extraction equipment for wet reprocessing of spent nuclear fuel, low level generated in large quantities It can be expected greatly as a low-cost and quick purification device for radioactive liquid waste (see Example 4). In the past, it was difficult to apply the liquid-liquid extraction method to the purification of environmental water and the treatment of large-scale wastewater from the viewpoint of cost, operation, safety, etc. Therefore, it can be expected that rapid and efficient water purification and wastewater treatment can be realized.

It is a schematic block diagram of a counterflow system emulsion flow continuous liquid-liquid extraction apparatus. It is a figure explaining generation | occurrence | production of the emulsion flow in a column part, and extinction of the emulsion flow in an upper phase separation part. It is a figure explaining a mode that an emulsion flow disappears in a lower phase separation part. It is a figure which shows the countercurrent system emulsion flow apparatus used in the Example. It is a graph which shows the result of the continuous extraction of ytterbium Yb (III) from nitric acid aqueous solution. It is a graph which shows the result of the continuous extraction of ytterbium Yb (III) in the presence of a particle component (Al ₂ O ₃ ). It is a graph which shows the highly selective extraction result of uranium U from the decontamination waste liquid simulation waste liquid by a counter-current system emulsion flow apparatus.

Explanation of symbols

10: Emulsion flow device 11: First head part 12: Second head part 13: Column part 14: Upper phase separation part 15: Lower phase separation part 16: Liquid feed pump 20: Reservoir 21: Conduit

Claims (2)

Feed pump,
A first head part for ejecting the aqueous phase sent by the liquid feed pump;
A second head part arranged opposite to the first head part, for finely extracting the extraction solvent phase circulated by the liquid feed pump and ejecting it toward the aqueous phase;
A column part where an emulsion flow of an aqueous phase and an extraction solvent phase occurs,
An upper phase separation unit installed above the column unit; and
A lower phase separation unit installed below the column unit;
An extraction solvent phase gathers in the upper phase separation part, an aqueous phase gathers in the lower phase separation part, and the extraction solvent phase of the upper phase separation part is circulated through the second head part. Counterflow type emulsion flow continuous liquid-liquid extraction device. 2. The apparatus according to claim 1, wherein the upper phase separation unit has a structure in which a mouth-squeezed container is inserted above the column unit, and the lower phase separation unit has a larger diameter than the column unit. A counter-current emulsion flow continuous liquid-liquid extraction device having a structure in which a container is coupled to the lower part of a column part .

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