JP2009183870A - Method and device for centrifugal extraction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for centrifugal extraction, which enable a countercurrent contact between a continuous phase and a dispersion phase and can perform high-resolution multi-stage extraction conveniently and stably. <P>SOLUTION: In a method for countercurrent centrifugal extraction, where a continuous phase and a dispersion phase are brought into countercurrent contact, emulsion is formed between two phases of the continuous phase and dispersion phase, and a Taylor-Couette flow is generated while maintaining the formed emulsion state as it is. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a centrifugal extraction method and a centrifugal extraction apparatus applied to solvent extraction such as separation of biochemical substances, removal of environmental pollutants, treatment of radioactive waste, and chemical analysis.

  In recent years, in addition to the development of new extractants that are applied to the separation of biochemical substances, the removal of environmental pollutants, the treatment of radioactive waste, etc., the development of high-performance extraction devices has been desired, There is also a need for more advanced extraction techniques in the field of chemical conversion, nuclear fuel reprocessing, nuclide separation technology, biochemical separation, new drug development, rare metal recycling, and the like. However, at present, development of highly functional extractants is underway, but little research and development has been conducted on extraction methods for efficiently using small amounts of expensive extractants.

  As an extraction method generally performed so far, there is a method in which oil water is flowed in a centrifugal flow extraction apparatus such as a mixer-settler extraction apparatus in parallel flow (two phases of an oil phase and an aqueous phase flow in the same direction). . Specifically, the oil phase and the water phase flow into the mixer-settler extraction device, and an emulsion is formed between the oil phase and the water phase by a rotating means (for example, a propeller unit) provided in the device, and By transferring this emulsion to the settling part, water and oil are separated, and harmful substances contained in the aqueous phase are extracted by transferring to the oil phase.

  According to this extraction method, the extraction equilibrium can be achieved in a short time and the residence time of the oil water can be shortened, so that it is widely used in nuclear facilities and the like. However, in this extraction method, since the flow of oil and water is parallel, only one extraction equilibrium is achieved with one extraction device, and multi-stage extraction devices are required for advanced separation.

  There is also an extraction technique using a microreactor. This microreactor is mainly used in technical fields such as chemical synthesis. Currently, the use of ultra-small reactors in the analytical chemistry field and small-scale production of drugs and the like is being studied. The oil / water extraction operation using a microreactor is performed by flowing oil / water through a narrow channel (width of about 100 μm) by a co-current operation. According to this extraction method, oil and water can be efficiently contacted in a narrow flow path, and therefore more efficient extraction can be expected as compared with the above-described extraction method.

  Further, unlike these extraction techniques, for example, there is a centrifugal extraction method using a centrifugal extraction device developed by Bair et al., University of Wisconsin, USA, as a method for performing extraction by countercurrent operation. This extraction method is an extraction method performed by rotating both the inner cylinder and the outer cylinder using a centrifugal extraction apparatus consisting of a double circular tube consisting of an inner cylinder and an outer cylinder. More specifically, the rotational speed of both the inner cylinder and the outer cylinder is controlled to form a double Taylor vortex array of the oil phase and the water phase in the gap between the two cylinders, and the counter current flows in a state where the oil water is separated. It is controlled to flow through. According to this extraction method, the Taylor vortex street is formed so that the oil and water are brought into countercurrent contact. Therefore, it is possible to perform multi-stage extraction, and the extraction method is compared with the extraction method performed by the cocurrent operation. The performance can be improved (for example, see Patent Documents 1 to 3).

Baier, G.G. , And M.M. D. Graham, “Two-Fluid Taylor-Couette Flow: Experiments and Linear Theory for Immiscible Liquids Between Rotating Cylinders,” Phys. Fluids, 10, 3045 (1998) Baier, G.G. , And M.M. D. Graham, “Two-Fluid Taylor-Couette Flow: Experiments and Linear Theory for Immiscible Liquids Cylinders Flow CounterCourtcounters. Flnids, 12, 294 (2000) Baier, G.G. , M.M. D. Graham, and E.M. N. Lightfoot, “Mass Transport in a Novel Two-Fluid Taylor Vortex Extractor”, AIChE J, 46, 2395 (2000) Y. Okada, K .; Takeshita and Y.T. Usui, Proc. of International Workshop on Process Intensification in Fluid and Particle Engineering, 66-67 (2006)

  However, although many researchers have been studying liquid-liquid extraction using a microreactor so far, the oil phase and water phase are simultaneously stabilized in the microchannel (50 μm to several mm) of the microreactor. However, even if it is a co-current operation that is easy in terms of operation, the operating conditions such as flow velocity and the physical properties (surface tension, viscosity, etc.) of the fluid used are severely limited.

  Specifically, a stable two-phase interface cannot be formed due to a difference in surface tension between the organic phase and the aqueous phase at a low flow rate, and a difference in viscosity at a high flow rate. Therefore, the stable range of the two-phase flow is limited to a narrow range. One researcher showed that a conventional micro extractor (fine channel width 0.1 mm, channel length 3 cm) using a phosphate ester and toluene in the oil phase and an aqueous nitric acid solution containing Cu in the water phase was used. An extraction experiment was conducted, and it was reported that the stage efficiency of one extractor was less than 0.2 (2003 Proceedings of the 22nd Solvent Extraction Discussion Meeting B-6). Therefore, to achieve high stage efficiency, a stable two-phase flow must be achieved with a long flow path.

  As described above, the extraction method using a microreactor such as a microreactor can efficiently contact oil and water through a narrow flow path, but the oil / water flow is unstable and ensures a stable flow. However, the operating conditions such as the flow rate and the physical properties of the fluid used are severely limited, and it cannot be said that the extraction method is simple and versatile. Furthermore, since this extraction method is basically a co-current operation of oil and water, only one stage of extraction equilibrium can be achieved with one reactor, and it is necessary to connect a number of microreactors in order to perform advanced separation. In addition, since a large number of liquid feeding pumps are installed, the apparatus configuration and operation become very complicated.

  On the other hand, in the centrifuge device comprising a double cylindrical tube of an inner cylinder and an outer cylinder, the extraction method in which two cylinders are rotated to form a double Taylor vortex street enables countercurrent contact and multistage extraction. Although it has become possible to achieve this, it is extremely difficult to control the flow of oil and water in a countercurrent flow in a countercurrent state, making it difficult to maintain stable extraction performance. It is not a centrifugal extraction method.

  The present invention has been proposed in view of such circumstances, and enables countercurrent contact between a continuous phase and a dispersed phase, and can perform advanced multistage extraction simply and stably. An object of the present invention is to provide a centrifugal extraction method and a centrifugal extraction device.

  As a result of intensive research from various viewpoints, the inventors of the present invention perform an advanced multistage extraction by forming an emulsion state between oil and water and forming a Taylor Couette flow while maintaining this emulsion state. As a result, the present invention has been completed.

  That is, the countercurrent centrifugal extraction method according to the present invention is a countercurrent centrifugal extraction method in which a continuous phase and a dispersed phase are brought into countercurrent contact, and an emulsion is formed between the two phases of the continuous phase and the dispersed phase. It is characterized by having an emulsion forming step and a Taylor Couette flow generating step of generating a Taylor Couette flow while maintaining the emulsion formed in the emulsion forming step.

  In addition, the centrifugal extraction device used in the countercurrent centrifugal extraction method according to the present invention includes an outer cylinder, an inner cylinder disposed with a gap inside the outer cylinder, and a rotation driving unit that rotates the inner cylinder. And the surface of the inner cylinder in contact with the gap exhibits hydrophobicity in a centrifugal extraction device in which the continuous phase and the dispersed phase are in countercurrent contact in the gap.

  According to the present invention, an emulsion state is formed, and a Taylor Couette flow is generated while maintaining this emulsion state, so that high-level multistage extraction is performed while maintaining a high mass transfer rate by the emulsion. It becomes possible.

  Hereinafter, the present invention will be described in detail with reference to the drawings.

  In the extraction method according to the present embodiment, the emulsion forming step for forming an emulsion between the two phases of the continuous phase and the dispersed phase, and the state of the emulsion formed in the emulsion forming step are maintained while maintaining the Taylor- And a Taylor Couette flow generation process for generating a Couette flow. As described above, the extraction method according to the present embodiment uses the emulsion for the purpose of greatly improving the extraction performance and the extraction agent utilization efficiency, and performs the extraction in the Taylor Couette flow while maintaining the emulsion state. ing.

  FIG. 1 shows an example of a centrifugal extraction apparatus suitably used for the centrifugal extraction method according to the present invention. As shown in FIG. 1, the centrifugal extraction device 10 according to the present embodiment includes an outer cylinder 11, an inner cylinder 12, and rotation driving means (not shown) that rotates the inner cylinder. In addition, the centrifugal extraction apparatus for performing the centrifugal extraction method according to the present embodiment is not limited to the centrifugal extraction apparatus 10 described in detail below, and the dimensions, surface materials, and the like of each component of the apparatus are as follows. An example thereof is shown and is not limited to the following.

  The outer cylinder 11 has a cylindrical shape, and the surface material is not particularly limited, such as resin, glass, metal steel, etc., but is preferably a hydrophilic material such as a hydrophilic resin. For example, an acrylamide polymer, a methacrylamide polymer, polyacrylic acid, polymethacrylic acid, polyvinyl alcohol, polyethylene glycol, polyvinyl pyrrolidone, cellulose, or a mixture thereof can be used. Further, for example, the above hydrophilic resin may be coated on metal steel. Note that the use of a hydrophilic material will be described later.

  The inner cylinder 12 has a cylindrical shape concentric with the outer cylinder 11 and is disposed in the outer cylinder 11 with a predetermined gap 13 provided between the inner cylinder 12 and the outer cylinder 11. The surface material of the inner cylinder 12 is not particularly limited, such as resin or glass, but preferably has hydrophobicity. For example, polytetrafluoroethylene, polyhexafluoropropene, polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, molybdenum disulfide, boron nitride, cobalt oxide, graphite, or a mixture thereof can be used. In the example described in detail here, it is assumed that an inner cylinder having a surface of polytetrafluoroethylene (Teflon: registered trademark) is used. The gap 13 between the outer cylinder 11 and the outer cylinder 11 is not particularly limited. For example, the gap 13 is a gap (space) of about 5 mm. The continuous phase and the dispersed phase are introduced into the gap 13 so as to make a countercurrent contact between the two phases. It has become.

  The rotation driving means is provided in the inner cylinder 12, and is configured to be able to control the rotation speed of the inner cylinder. The rotation driving means includes, for example, a motor unit that generates power and a power transmission unit that transmits power of the motor unit. The motor unit is connected to the power transmission unit via a timing pulley, a timing belt, or the like. The power is transmitted to. This rotation driving means is capable of rotating the inner cylinder at a high speed of 1500 rpm or more, and has a rotation control unit, and the rotation speed is less than 600 rpm, 600 rpm to 1200 rpm, 1200 rpm or more, as desired. The rotation speed can be adjusted. Note that the internal configuration and power transmission mechanism of the rotation driving means are not limited to the above.

  The centrifugal extraction device 10 according to the present embodiment includes a continuous phase inlet 14 and a dispersed phase outlet 15 at the upper portion of the device, and a dispersed phase inlet 16 and a continuous phase flow at the lower portion of the device. And an outlet 17. From the continuous phase inlet 14, for example, a continuous phase containing substances to be separated and extracted such as heavy metals and environmental pollutants flows into a gap 13 provided between the outer cylinder 11 and the inner cylinder 12, while the dispersed phase From the inflow port 16, a dispersed phase containing an extractant for extracting substances to be separated and extracted such as heavy metals and environmental pollutants flows into the gap 13, and flows in from the upper and lower parts of the centrifugal extractor 10. The continuous phase and the dispersed phase are configured to be in countercurrent contact in the gap 13. Then, by the centrifugal extraction method described in detail below, the dispersed phase obtained by separating and extracting the extraction target substance such as heavy metal contained in the continuous phase with the extractant is discharged from the dispersed phase outlet 15. It is collected. On the other hand, a continuous phase from which heavy metals and the like are removed by countercurrent contact with the dispersed phase flows out from the continuous phase outlet 17, and the continuous phase is collected. The inflow / outflow of the dispersed phase and the continuous phase are driven by pumps provided at the inflow ports 14 and 16 and the outflow ports 15 and 17, but are driven by a pump mechanism. It is not limited to.

  More specifically, the basic operation procedure will be described. First, the gap 13 of the centrifugal extraction device 10 composed of a double circular tube of the outer cylinder 11 and the inner cylinder 12 is filled with a continuous phase, and the motor of the rotational drive means is installed. The cylinder 12 is rotated by being driven. When the inner cylinder is rotated and the rotational speed is gradually increased, the flow of the water phase filled in the gap 13 shifts to a transition region (Taylor Couette flow region) from laminar flow to turbulent flow. By maintaining the flow in the centrifugal extraction device 10 in the region, a Taylor vortex array in which Taylor vortices are arranged in multiple stages in the direction of the rotation axis of the inner cylinder 12 is formed. FIG. 2 is a diagram schematically showing a state in which a Taylor vortex street is generated in a Taylor-Couette flow state in the centrifugal extraction device 10 according to the present embodiment. This Taylor vortex train is formed by gradually increasing the rotational speed of the inner cylinder 12 from a laminar flow state (inner cylinder rotational speed less than 600 rpm) to a Taylor Couette flow state (600 to 1200 rpm). A shearing force is generated on the surface of the inner cylinder 12, and the centrifugal force of the fluid rotating in the vicinity of the inner cylinder 12 is larger than the centrifugal force of the fluid rotating in the vicinity of the outer cylinder 11, thereby making a donut shape. Taylor vortexes are formed in a row. In the centrifugal extraction method according to the present embodiment, with the Taylor vortex street formed as described above, the continuous phase is introduced from the upper part of the centrifugal extraction apparatus 10 and the dispersed phase is introduced from the lower part of the centrifugal extraction apparatus 10, respectively. The two phases are brought into countercurrent contact.

  In addition, it is needless to say that the dimensions and the like of each component described in FIG. 1 are not limited to this, and can be changed as appropriate.

  In the previous studies by the present inventors, in a centrifugal extraction device consisting of a double circular tube, the rotational speed of the inner tube was increased, and the Taylor Couette flow in the transition region from laminar flow to turbulent flow in the device. It is clarified that multistage extraction is possible in the liquid-liquid (oil-water) countercurrent operation of the continuous phase (aqueous phase) and the dispersed phase (organic phase), and the extraction efficiency can be improved. (For example, refer nonpatent literature 4). This is considered to be caused by increasing the inner cylinder rotation speed, increasing the shear stress on the surface of the inner cylinder of the centrifugal extraction device, and increasing the amount of organic phase retained in the device (hold-up). More specifically, by making the swirl flow transition from laminar flow to Taylor Couette flow, the organic phase is sheared and atomized by the rotating inner cylinder surface, and the atomized organic phase becomes the inner cylinder surface. It is considered that the extraction performance is improved by collecting oil at the Taylor vortex suction position and increasing the oil phase hold-up as the flow rate increases due to the transition of the swirling flow.

  However, in order to operate the oil-water counterflow in a stable state, it is necessary to control the operation at an inner cylinder rotational speed that does not cause turbulence in the continuous phase (water phase) and flooding. There are limits to improvement. Moreover, in order to enable higher performance extraction using a small device, it is necessary to increase the mass transfer rate, and there is a limit to the mass transfer rate in the extraction operation in the Taylor Couette flow region. As it is, advanced separation and extraction cannot be realized.

  By increasing the inner cylinder rotation speed and making the flow in the apparatus turbulent, the two phases of the organic phase and the aqueous phase shift to an emulsion state. In this state, the contact area of the two phases is increased and the emulsion is atomized by high-speed rotation, so that a large mass transfer rate can be expected. Therefore, although the extraction efficiency can be greatly improved, Because of the operation, the axial mixing and diffusion of the inner cylinder is increased, and the clean countercurrent contact realized under the Taylor-Couette flow region cannot be maintained. That is, it becomes impossible to form a concentration gradient of the target substance in the apparatus necessary for the countercurrent multistage extraction operation, and it becomes impossible to realize advanced separation and extraction.

  Therefore, in the centrifugal extraction method according to the present embodiment, first, an emulsion is formed between the continuous phase (aqueous phase) and the dispersed phase (organic phase) at a high rotational speed, and then the emulsion state is maintained. In order to achieve multistage extraction, the inner cylinder rotation speed is controlled to be lowered to the Taylor Couette flow region. As a result, the mass transfer speed of the emulsion and the increase of the contact area between the two phases can be realized, and a stable oil-water counter-current flow in the Taylor Couette flow can be realized at the same time. Compared to the extraction method, it is possible to achieve a significant improvement in extraction performance.

  Moreover, since extraction is performed in the Taylor Couette flow region, it is possible to suppress mixing and diffusion in the axial direction of the inner cylinder, and a flow closer to plug flow is generated in an emulsion state. In addition, efficient multistage extraction can be performed by oil-water countercurrent. Hereinafter, the centrifugal extraction method according to the present embodiment will be described in more detail using an example in which the centrifugal extraction device 10 is used.

  In the extraction method according to the present embodiment, an emulsion is formed between the continuous phase (aqueous phase) and the dispersed phase (organic phase). More specifically, first, the gap 13 of the double tube cylinder composed of the outer cylinder 11 and the inner cylinder 12 is filled with the water phase, and the inner cylinder 12 is rotated to change the state of the water phase flow to a laminar flow (less than 600 rpm). By maintaining the transition region from turbulent flow (inner cylinder rotation speed of 1200 rpm or more), that is, Taylor Couette flow, Taylor vortex streets are formed in the rotation axis direction. A Taylor Couette flow is generated by setting the rotational speed of the inner cylinder 12 to about 600 to 1200 rpm. In this state, a continuous phase is introduced from the continuous phase inlet 14 at the upper part of the apparatus and a dispersed phase is introduced from the lower dispersed phase inlet 16 to the gap 13 between the outer cylinder 11 and the inner cylinder 12, respectively. In countercurrent contact.

  The dispersed phase used here is dispersed in the form of droplets in the apparatus, while the continuous phase is a solution surrounding the droplet-shaped dispersed phase. Need to be liquids that do not mix with each other. For example, when one of the dispersed phase or the continuous phase is an aqueous phase, the other needs to be an organic phase (oil phase) insoluble in water. In the present embodiment, as described above, the continuous phase is an aqueous phase containing a heavy metal or the like for extraction, and the dispersed phase is an organic phase (oil phase) containing an extractant. Will be described.

  Subsequently, the rotational speed of the inner cylinder 12 is increased while the two phases are in countercurrent contact. As the rotational speed of the inner cylinder 12 is increased, the organic vortex and the organic cylinder holdup increase with the increase in the shear stress of the Taylor vortex and the inner cylinder 12, and the extraction performance is improved. That is, as the rotational speed of the inner cylinder 12 increases, an organic phase is accumulated in a portion where Taylor vortex is sucked, and a plurality of annular oil phase structures are formed on the surface of the inner cylinder 12, thereby increasing the number of rotations. , A large shearing force acts on the surface of the inner cylinder 12, whereby the organic phase is finely dispersed (atomized), and the organic phase holdup is further increased, thereby improving the extraction performance.

  In the centrifugal extraction method according to the present embodiment, the rotational speed of the inner cylinder 12 is increased in order to enable more advanced separation and extraction, and the rotational speed of the inner cylinder 12 is increased to about 1200 rpm or more. By doing so, the inside of the apparatus is made a turbulent state. By doing so, an emulsion is formed between the two phases.

  In this emulsion state, the contact area between the two phases of the water phase and the organic phase (oil phase) becomes large, and it is possible to realize a high mass transfer rate between the oil and water, thereby greatly improving the extraction performance. It becomes possible to make it. The centrifugal extraction method according to the present embodiment thus improves the extraction performance by turbulently flowing in the apparatus into which the aqueous phase and the organic phase have been introduced, and forming an emulsion between the oil and water two phases. .

  Here, in order to form an emulsion, the rotational speed of the inner cylinder 12 was increased to about 1200 rpm or more to make it turbulent. In operation in this turbulent state, mixing and diffusion gradually in the axial direction of the inner cylinder 12 was performed. However, Taylor's vortex line observed under the Taylor-Couette flow region is not formed, although a high mass transfer speed in the emulsion state can be exhibited. Therefore, it becomes impossible to obtain a clean concentration gradient of the target substance necessary for the multistage extraction, and the extraction operation cannot be performed effectively. Furthermore, since the operation is in a turbulent state, the mechanical burden on the centrifugal extractor increases, and it becomes difficult to operate for a long time.

  Therefore, in the centrifugal extraction method according to the present embodiment, control is performed so as to reduce the rotational speed of the inner cylinder 12 while maintaining the emulsion state formed as described above. That is, after the emulsion is formed in the turbulent state, the inner cylinder 12 is rotated to the Taylor Couette flow region where a mixed concentration is avoided and a clean concentration gradient is obtained while maintaining the formed emulsion state. Control is performed to reduce the speed. Specifically, the rotational speed of the inner cylinder 12 is reduced to a rotational speed of 600 to less than 1200 rpm, more preferably to a rotational speed of 600 to 800 rpm.

  Thus, by extracting while maintaining the emulsion state in the Taylor Couette flow region, effective multi-stage extraction can be realized, and the utilization efficiency of the extractant can be greatly improved. In addition, since it is possible to exhibit a high level of extraction performance with a small amount of oil phase, it is possible to greatly reduce the mechanical burden on the extraction apparatus applied to the centrifugal extraction method according to the present embodiment. Thus, a smaller centrifugal extractor can be created.

  However, since control is performed to reduce the inner cylinder rotation speed to the Taylor Couette flow region, the emulsion formed in the turbulent flow state can be maintained for a long time under the Taylor Couette flow region. There is a risk that an effective extraction operation cannot be performed. That is, there is a possibility that the formed emulsion may disappear due to the Taylor Couette flow.

  Therefore, in the centrifugal extraction method according to the present embodiment, the surface of the inner cylinder 11 of the applied centrifugal extraction device 10 is made of a hydrophobic material, for example, a hydrophobic resin such as polytetrafluoroethylene. ing. When the inner cylinder is rotated in the Taylor Couette flow region, it is originally possible to apply a predetermined shearing force by the rotation. In this situation, the inner cylinder 12 is made of a hydrophobic material. The hydrophobic interaction can be exerted between the inner cylinder surface and the emulsion, and a larger shearing force can be applied to the inner cylinder surface. In the centrifugal extraction method according to the present embodiment, the shear force of the inner cylinder surface is effectively applied in this way, so that the emulsion state formed in the turbulent state is maintained for a long time. It is possible. As described above, as the hydrophobic resin, polytetrafluoroethylene, polyhexafluoropropene, polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, molybdenum disulfide, boron nitride, cobalt oxide, graphite, or These mixtures can be used, but are not particularly limited. Of these, those having a particularly high hydrophobicity are more preferable because they can exhibit a more hydrophobic interaction.

  In the centrifugal extraction method according to the present embodiment, it is more preferable that the surface of the outer cylinder 12 of the applied centrifugal extraction device 10 is made of a hydrophilic material. Thus, in the double cylindrical tube comprising the outer cylinder 11 and the inner cylinder 12, the surface in contact with the gap 13 of the inner cylinder 12 is made of a hydrophobic surface material, and the inner wall surface of the outer cylinder 11 is hydrophilic. By using the surface material having the structure, it becomes possible to form a Taylor vortex array more efficiently due to the interaction between the outer cylinder 11 and the inner cylinder 12, and the multistage extraction based on the systematic flow is effective. Therefore, the extraction performance can be greatly improved.

  In addition, you may make it provide the disperser which forms an emulsion in the site | part which supplies an aqueous phase and an organic phase for the purpose of maintaining the above-mentioned emulsion state over a longer time. By providing a dispersing device in the supply section in this way, it becomes possible to supplement the lost emulsion in the Taylor Couette flow region at any time, maintain the emulsion state for a longer time, and increase the mass transfer of the emulsion. The extraction performance can be improved by increasing the speed and the contact area.

  As described above, according to the centrifugal extraction method according to the present embodiment, the rotational speed of the inner cylinder is increased, an emulsion is formed, and separation and extraction are effectively performed in this emulsion state. The contact area can be increased, and the high rotation speed of the inner cylinder enables the emulsion to be atomized on the surface of the inner cylinder to exhibit a high mass transfer speed, greatly improving the extraction performance. Can be improved.

  Further, according to the centrifugal extraction method according to the present embodiment, after the emulsion is formed, the rotational speed of the inner cylinder is controlled to be lowered to the Taylor Couette flow region while maintaining the emulsion state. Therefore, while exhibiting the extraction effect in the emulsion state, it is possible to reduce the mixing and diffusion in the axial direction of the inner cylinder, and to generate a flow closer to the plug flow, between the efficient oil and water in the Taylor Couette flow region Multistage extraction based on countercurrent contact can be realized.

  Furthermore, according to the centrifugal extraction method according to the present embodiment, by using a centrifugal extraction device including an inner cylinder whose surface is made of a material having a high hydrophobicity, the inner cylinder is placed under the Taylor Couette flow region. In addition to the shearing force accompanying the rotation of the inner cylinder, it is possible to greatly improve the shearing force based on the hydrophobic interaction of the inner cylinder. It is possible to maintain it underneath, and it is possible to improve the utilization efficiency of the extractant such as an analyzer and drug production, and to use it suitably in a place where quick and advanced extraction is required.

  In addition, according to the centrifugal extraction method according to the present embodiment, high-level extraction is possible at a slower inner cylinder rotation speed, so that the mechanical burden on the extraction device applied to the extraction method is greatly reduced. Furthermore, it is possible to reduce the size of the extraction device and to perform a simple and quick extraction operation.

  Hereinafter, more specific examples will be described, but the present invention is not limited to these examples.

<Experiment on the extraction rate of Zn ions with respect to the inner cylinder rotation speed>
The basic extraction operation in this example is to fill an aqueous phase containing a zinc nitrate (Zn (NO ₃ ) ₂ ) solution having a Zn ion concentration of 65 ppm (= 65 mg / L) in the gap between the inner cylinder and the outer cylinder. The cylinder was rotated to generate a Taylor vortex. After the Taylor vortex was stabilized, an aqueous phase containing a Zn (NO ₃ ) ₂ solution having a Zn ion concentration of 65 ppm (= 65 mg / L) was added from the upper part of the apparatus, and a 10 mmol / L phosphate ester extractant (D2EHPA: A dodecane solution (organic phase) containing di-2-ethylhexylphosphoric acid) was introduced into the gap between the inner cylinder and the outer cylinder at a constant flow rate of 10 ml / min, respectively, and an oil-water countercurrent operation was performed. The temperature was room temperature (25 ° C.). The centrifugal extraction apparatus used in the following experiment uses the same apparatus as the apparatus shown in FIG. 1 with dimensions and the like, and uses a centrifugal extraction apparatus whose inner cylinder surface in contact with the gap is made of polytetrafluoroethylene. did.

Example 1
(Extraction operation in the emulsion state)
By the above basic operation, the water phase is introduced from the upper part of the device and the organic phase is introduced from the lower part of the device and brought into countercurrent contact. First, the inner cylinder is rotated to 1500 rpm to form an emulsion between the aqueous phase and the organic phase. I let you. And with the state of the formed emulsion, the inner cylinder rotational speed was decreased to a predetermined rotational speed, and the change with time in the amount of Zn extracted from the flowing out oil water at each rotational speed was measured.

(Comparative Example 1)
(Extraction operation without forming an emulsion)
According to the above basic operation, the aqueous phase is introduced from the upper part of the apparatus and the organic phase is introduced from the lower part of the apparatus and brought into countercurrent contact, and unlike Example 1, the organic phase is extracted without forming an emulsion and flows out of the apparatus. The water phase was collected and the relationship between the inner cylinder rotation speed and the Zn extraction performance was investigated.

(Extraction experiment results in Example 1 and Comparative Example 1)
FIG. 3 is a graph showing experimental results of extraction performance at each inner cylinder rotation speed in the Zn extraction experiments of Example 1 and Comparative Example 1.

  As can be seen from this graph, in the experiment of Example 1, the operation while maintaining the emulsion state showed a higher extraction rate in the low rotation range of 800 rpm or lower than the high rotation range of 1000 rpm or higher. The extraction rate was much larger than the extraction operation in the Couette flow. In particular, at a rotational speed of 800 rpm, the result of theoretical plate analysis was about 96%, and an extremely high extraction rate of 30 or more theoretical plates was shown. From this result, it is understood that a large oil / water contact area and a stable oil / water countercurrent are simultaneously achieved by operating at a low rotation speed while maintaining the emulsion state. Moreover, as shown in FIG. 1, a high extraction rate of about 96% was made possible even though the oil / water was simply brought into countercurrent contact with a device having a small rotating part having an actual movable length of 18 cm. Therefore, it was found that a high-level extraction can be easily realized using a small apparatus. In addition, although the extraction performance rapidly decreases at 1000 rpm or more, this is because the turbulent flow in the column increases the effect of mixing and diffusing in the axial direction. This is thought to be due to the fact that the multistage extraction effect due to the countercurrent flow becomes smaller.

  On the other hand, in the extraction operation that is simply operated in the Taylor Couette flow without forming the emulsion of Comparative Example 1, the extraction rate increases when the number of rotations of the inner cylinder is increased. Especially at 1200 rpm or more, the organic phase in the apparatus is increased. It can be seen that the extraction performance is improved by increasing the hold-up. However, as a result of theoretical plate analysis by this method, only a maximum of about three theoretical plates (at a rotational speed of 1400 rpm) was obtained at the maximum, and the extraction rate was much lower than that of Example 1. Also, if the inner cylinder is rotated at a rotational speed of 1400 rpm or more, the inside of the tower is turbulent to form an emulsion, a stable Taylor Couette flow cannot be maintained, the burden on the apparatus increases, and the number of theoretical plates continues to be three. It turned out to be difficult to show the extraction rate.

<Experiment on sustainability of Zn extraction performance in emulsion state>
(Example 2)
Under the same conditions as in Example 1 (flow rates of organic phase and aqueous phase: 10 mL / min), oil water was counterflowed, and the oil water was emulsified at 1500 rpm, and then the inner cylinder rotation speed was adjusted to 600 rpm. An aqueous phase composed of a Zn (NO ₃ ) ₂ solution containing a Zn ion concentration of 65 ppm (= 65 mg / L) from the upper part of the apparatus is introduced into the dodecane solution (organic phase) containing 10 mmol / L of D2EHPA from the lower part of the apparatus. Counter-current operation was performed. The time change of the Zn extraction performance was examined with the time when the inner cylinder rotation speed was changed to 600 rpm as 0 minutes.

(Experimental result)
FIG. 4 is a graph showing the results of this example regarding the change in the extraction performance of Zn with respect to time. The plot indicated by the white circle in the graph represents the Zn concentration in the organic phase flowing out from the upper part of the apparatus, and the plot indicated by the black circle represents the Zn concentration in the aqueous phase flowing out from the lower part of the apparatus. . As can be seen from this graph, the extraction performance of Zn is stably maintained over a long period of about 150 minutes, and this extraction method can be used effectively in chemical analysis and substance purification. It turned out to be. It is considered that the flow after 150 minutes suddenly changed from an oil-water emulsion to a normal Taylor Couette flow, and the Zn extraction performance was greatly reduced accordingly. This change in flow was confirmed by visual observation of the flow in the apparatus. That is, from this result, it can be concluded that the emulsion formed in the turbulent state can be maintained for about 150 minutes in the Taylor-Couette flow region to achieve a stable extraction performance.

<Experiment on tracer response of oil phase after emulsion formation>
(Example 3)
In order to investigate the flow of the oil phase in the apparatus, an organic phase (10 mmol / L D2EHPA solution diluted with dodecane) containing a trace amount of tracer (beta-carotene) in an emulsion state was continuously flowed (stepped). The response curve was examined.

  First, in the same manner as in Examples 1 and 2, the water phase and the organic phase were caused to flow counter-currently at a flow rate of 10 ml / min, and an oil-water emulsion was formed at an inner cylinder rotational speed of 1500 rpm. Thereafter, the inner cylinder rotation speed was adjusted to 800 rpm, 1000 rpm, and 1500 rpm, and the organic phase containing the tracer was continuously added (stepped).

(Experimental result)
FIG. 5 is a graph showing the results of the tracer experiment in the emulsion state. The horizontal axis of this graph represents the operation time (t / T) normalized by the average residence time of the organic phase. The vertical axis represents the tracer concentration in the organic phase that flows out, and is a value (C / C ₀ ) normalized by the tracer concentration in the supplied organic phase. In this graph, the time when the tracer is turned on is defined as time 0 (zero). If the mixing diffusion in the axial direction of the apparatus can be ignored, it is considered that the continuously input tracer appears in a step shape at the standard time 1 (plug flow), and when the mixing diffusion is large, the response curve of the complete mixing flow, that is, the time It is thought that it flows out while gradually increasing the concentration from 0 (zero).

  As a result of the experiment, when the inner cylinder was rotated at 800 rpm, the mixing and diffusion effect in the axial direction was small. As a result of analysis of the response curve by the complete mixing tank row model, it was found that the number of complete mixing tank rows was 10 at 800 rpm, and the flow was very close to plug flow. When the number of rotations is increased from 1000 rpm to 1500 rpm, the number of complete mixing tank rows decreases to 4 tanks at 1000 rpm and 2 tanks at 1500 rpm (the influence of mixing and diffusion in the axial direction increases), and the flow in the apparatus becomes a completely mixed flow. You can see that they are close. Therefore, as shown in Example 1, it was found that this extraction method exhibits the maximum extraction performance at 800 rpm. This is considered to be because the multistage extraction effect between oil and water was efficiently expressed at 800 rpm where the flow of the organic phase was closest to the plug flow. In addition, since the multi-stage extraction effect can be efficiently exhibited at 800 rpm, the operation of the centrifugal extraction apparatus to which the present extraction method is applied can be efficiently performed, and extraction with reduced mechanical burden can be performed. It turns out that it can be realized.

It is the figure which showed roughly the structure of the centrifugal extraction apparatus applicable to the centrifugal extraction method which concerns on this Embodiment. It is a figure for demonstrating the state in which the Taylor vortex row was formed in the centrifugal extraction apparatus applicable to the centrifugal extraction method which concerns on this Embodiment. It is a graph which shows the experimental result about the extraction rate of Zn ion with respect to an inner cylinder rotation speed. It is a graph which shows the experimental result about the sustainability of the extraction performance of Zn ion in an emulsion state. It is a graph which shows the experimental result about the tracer response of the oil phase after emulsion formation.

Claims (8)

In the centrifugal extraction method in which the continuous phase and the dispersed phase are in countercurrent contact,
An emulsion forming step of forming an emulsion between the two phases of the continuous phase and the dispersed phase;
And a Taylor Couette flow generating step of generating a Taylor Couette flow while maintaining the emulsion formed in the emulsion forming step. The centrifugal extraction method is performed using a centrifugal extraction device including an outer cylinder, an inner cylinder disposed with a gap inside the outer cylinder, and a rotation driving unit that rotates the inner cylinder.
The centrifugal extraction method according to claim 1, wherein in the emulsion forming step, the inner cylinder is rotated to form an emulsion.   3. The centrifugal extraction method according to claim 2, wherein, in the Taylor Couette flow generation step, the Taylor Couette flow is generated by rotating the cylinder at a rotation speed lower than the rotation speed in the emulsion formation step. . Centrifugal extraction comprising an outer cylinder, an inner cylinder disposed with a gap inside the outer cylinder, and a rotation driving means for rotating the inner cylinder, wherein the continuous phase and the dispersed phase are brought into countercurrent contact in the gap. In the device
The centrifugal extraction device according to claim 1, wherein the surface of the inner cylinder in contact with the gap is made of a hydrophobic material.   The centrifugal extraction device according to claim 4, wherein the outer cylinder is made of a material having an inner wall having hydrophilicity.   The surface of the inner cylinder is made of a material selected from polytetrafluoroethylene, polyhexafluoropropene, polyethylene, polypropylene, polyethylene terephthalate, polyethylene naphthalate, polyacetal, polycarbonate, molybdenum disulfide, boron nitride, cobalt oxide, and graphite. The centrifugal extraction device according to claim 4.   The centrifugal extraction device according to claim 6, wherein the surface of the inner cylinder is polytetrafluoroethylene.   The centrifugal extraction device according to claim 4, further comprising a disperser for forming an emulsion.

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