JPH0817907B2 - Separation method of mixed solution - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for separating a mixed solution using a permeable membrane, which is also called vaporization permeation method.

[0002]

2. Description of the Related Art A method for separating a specific liquid component such as alcohol from a mixed solution in which two or more liquid components such as a mixed solution of water and alcohol are mixed by using a permeable membrane is called a pervaporation method. Methods are conventionally known. In this pervaporation method, the inside of the tank is partitioned by a permeable membrane into an upper solution chamber and a lower decompression chamber, and a mixed solution is introduced into the upper solution chamber, and the decompression chamber is brought into contact with the solution to the permeable membrane. By reducing the pressure, a specific liquid component in the mixed solution is preferentially permeated and diffused into the permeable membrane, and the liquid component that has passed through the permeable membrane is vaporized from the surface of the permeable membrane to the decompression chamber, In this way, by collecting the components in the decompression chamber that have been permeated through the permeable membrane, a specific liquid component can be separated and collected from the mixed solution. However, in this pervaporation method, the mixed solution is in direct contact with the permeable membrane, and generally the permeable membrane formed of a polymer material is often swollen by the mixed solution. When the permeable membrane is swollen in this way, the membrane function of the permeable membrane is reduced, and the separation performance of the mixed solution by the permeable membrane may be significantly impaired.

[0003] For this purpose, the present inventors have developed a technique which can also be referred to as a vaporization and infiltration method. A method for separating a mixed solution using the vaporization and infiltration method is disclosed in Japanese Patent Application Laid-Open No. 63-162003.
It is already provided in Japanese Patent Publication No. That is, as shown in the principle of this method in FIG. 3, the decompression chamber 1 and the solution chamber 3 into which the mixed solution 2 is introduced are partitioned by a permeable membrane 4 so as not to contact the mixed solution 2, and the decompression chamber 1 is decompressed. The vapor of the mixed solution 2 generated in the solution chamber 3 is permeated through the permeable membrane 4. In this method, since the permeable membrane 4 does not come into contact with the mixed solution 2, there is no problem that the membrane function is deteriorated due to the swelling of the permeable membrane 4, and the separation performance of the mixed solution 2 by the permeable membrane 4 can be improved.

[0004]

As described above, in the vaporization permeation method, the mixed solution 2 can be separated with a higher separation performance than the pervaporation method, but the separation performance is still sufficient. Has not arrived. Further, in this method, as in the case of the pervaporation method, the liquid component is diffused in the permeable membrane 4 and permeated to be separated, so that the liquid component permeates through the permeable membrane 4 at a low speed, and thus is sufficiently separated. It is difficult to allow the liquid to permeate the permeable membrane 4 at the permeation rate for liquid separation, and there is a problem in terms of productivity of liquid separation, which makes practical use difficult.

The present invention has been made in view of the above points, and it is possible to further enhance the liquid separation performance by the vaporization permeation method and to increase the permeation rate of the separated liquid to a practical level. The purpose is.

[0006]

In the method for separating a mixed solution according to the present invention, a mixed solution 2 is introduced between a decompression chamber 1 and a solution chamber 3 into which a mixed solution 2 in which a plurality of liquid components are mixed is introduced. By providing the permeable membrane 4 in a state where the permeable membrane 4 is not contacted, decompressing the decompression chamber 1 to allow the vapor of the mixed solution 2 generated in the solution chamber 3 to permeate the permeable membrane 4 from the solution chamber 3 side to the decompression chamber 1 side, When separating a specific liquid component in the mixed solution 2, a porous membrane having a high affinity for this specific liquid component that separates from other components among the components in the mixed solution 2 is used as the permeable membrane 4. The gas is supplied into the solution chamber 3.

The present invention will be described in detail below. FIG. 1 shows an example of the principle device for liquid separation according to the present invention based on the vaporization permeation method as described above, in which the separation tank 5 is formed by the permeable membrane 4 into the upper decompression chamber 1 and the lower solution chamber 3. A space is formed between the liquid surface of the mixed solution 2 introduced into the solution chamber 3 and the lower surface of the permeable membrane 4 so that the mixed solution 2 does not come into contact with the permeable membrane 4. A vacuum pump or the like is connected to 1 to reduce the pressure. A gas such as air can be introduced into the solution chamber 3. For example, as shown in FIG. 1, a pipe 10 provided with a cock 9 and the like is connected into the solution chamber 3 so as to be introduced between the permeable membrane 4 and the liquid surface of the mixed solution 2, and a gas such as air is piped from a pump. 10
By supplying the gas to the solution chamber 3, a gas such as air can be introduced into the solution chamber 3. The gas to be supplied into the solution chamber 3 is not limited to air, and various gases such as nitrogen gas can be used, and are not particularly limited. Further, as the mixed solution 2, for example, a mixed solution of two or more liquid components such as a mixed solution of water and alcohol in the case of concentrating and separating alcohol from fermentation alcohol is used.

In the present invention, the permeable membrane 4 is a porous membrane having a large number of communicating pores.
The size of the pores of this porous membrane is 1 × 1
It is preferable to use one having a range of 0 ⁻³ μ to 5 μ. If the size of the pores is larger than this, a large amount of components pass through the pores without being affected by the liquid separation by the permeable membrane 4, and it becomes impossible to obtain a high liquid separation performance. If the size of the pores is smaller than this, on the contrary, the liquid component cannot easily pass through the pores, and the permeation rate of the separated liquid cannot be increased to a practical level. is there. Here, in the present application, the diameter of the pore is defined as the diameter of this circle assuming a circle having the same area as the area of the pore, and the average diameter is defined as the average value of the diameter of each pore. Is what is done. Further, it is preferable to use one having a ratio of the area of pores to the surface area of this porous membrane, that is, a porosity of 5% or more. When the porosity is lower than this, the amount of permeation of the liquid component decreases, and it becomes difficult to increase the permeation rate of the separated liquid to a practical level.

In the present invention, as the porous permeable membrane 4, one having a critical surface tension close to the surface tension of the liquid component of each liquid component in the mixed solution 2 which is separated by permeating the permeable membrane 4 is used. It is a thing. That is, the mixed solution is A,
When the liquid components B, C ... Are mixed and the liquid component A is permeated through the permeable membrane 4 and separated from the other liquid components B, C ..., the surface tension of the liquid components B, C. Permeable membrane 4 having a critical surface tension closer to the surface tension of the liquid component of A than
Is used. In this case, the critical surface tension of the permeable membrane 4 is larger than the surface tension of the liquid component that permeates and separates the permeable membrane 4 and is smaller than the surface tension of other liquid components in the mixed solution 2, that is, the permeable membrane. 4, which is larger than the surface tension of the liquid component A which allows the other component B to pass through,
Those having a surface tension smaller than that of the liquid component of C ... are preferable. For example, the surface tensions of various liquids are as shown in "Table 1",
If the permeable membrane 4 having a critical surface tension closer to the surface tension of other liquids in "Table 1" than the surface tension of water is used, the mixed solution 2 of water and other liquids in "Table 1" will be A permeable membrane 4 is used which is capable of separating the other liquids in Table 1 and which has a critical surface tension between the surface tension of water and the surface tension of the other liquids in Table 1. For example, the other liquid in "Table 1" can be more efficiently separated from the mixed solution 2 of water and the other liquid in "Table 1". Here, the critical surface tension of a solid is defined as follows.
That is, assuming that the contact angle of a homologous series of liquid hydrocarbons and other organic liquid compounds on the solid surface is θ and the surface tension of the liquid is γ, cos θ to γ are constant straight lines regardless of the type of homologue. In many cases, γ corresponding to θ = 0 in this case
The value is defined as the critical surface tension of the solid.

[0010]

[Table 1]

The porous permeable membrane 4 is not limited to a particular one, but a polypropylene porous membrane, a polytetrafluoroethylene porous membrane, a polycarbonate porous membrane, or the like is used. You can
As a porous film of polypropylene, "Celgard" manufactured by Hoechst, etc., as a porous film of polytetrafluoroethylene, "Fluoropore" manufactured by Sumitomo Electric Co., Ltd., etc., as a porous film of polycarbonate manufactured by Nuclepore. Nuclepore ”and the like can be obtained and used.

In the apparatus of FIG. 1, however, when the pressure inside the decompression chamber 1 is reduced, the inside of the solution chamber 3 is also depressurized through the holes of the permeable membrane 4, and the vapor of each liquid component is generated from the mixed solution 2 in the solution chamber 3. Then, vapor of each liquid component reaches the porous permeable membrane 4. Here, of the components of the mixed solution 2, a liquid component having a surface tension close to the critical surface tension of the permeable membrane 4 easily wets the permeable membrane 4 and has a high affinity. It is difficult to wet the permeable membrane 4 and has no affinity. Further, in particular, a liquid component having a surface tension smaller than the critical surface tension of the permeable membrane 4 is easily wetted and has an affinity for the permeable membrane 4, and conversely, a liquid component having a surface tension larger than the critical surface tension of the permeable membrane 4 is It is difficult to wet the permeable membrane 4 and has no affinity. Therefore,
Of the vapor of each liquid component reaching the porous permeable membrane 4, the liquid component having a surface tension close to the critical surface tension of the permeable membrane 4 and a surface tension smaller than the critical surface tension of the permeable membrane 4 is the permeable membrane 4.
Of the permeable membrane 4 easily passing through the pores and easily passing through the permeable membrane 4 from the solution chamber 3 side to the decompression chamber 1 side.
The liquid component whose surface tension is not close to the critical surface tension of the permeable membrane 4 and whose surface tension is larger than the critical surface tension of the permeable membrane 4 is
It is difficult to pass through the fine pores due to being repelled by the surface of the membrane, and the permeable membrane 4 cannot easily permeate from the solution chamber 3 side to the decompression chamber 1 side. In this way, the surface tension of each liquid component in the mixed solution 2 is close to the critical surface tension of the permeable membrane 4, and the permeable membrane 4
A liquid component having a surface tension lower than the critical surface tension is preferentially permeated through the permeable membrane 4 to separate a predetermined liquid component from the mixed solution 2 to obtain a liquid having a high concentration of this liquid component. Is. At this time, the necessary liquid component is added to the permeable membrane 4
When liquid is separated by permeating the liquid, it is sufficient to collect the liquid that has reached the decompression chamber 1. On the contrary, the liquid that is needed is obtained by permeating the unnecessary liquid component through the permeable membrane 4 and separating the liquid. When the solution is left inside, the solution may be recovered from the solution chamber 3.

When liquid separation is performed using the porous permeable membrane 4 in the vaporization and permeation method as described above, the separated liquid component passes through the pores of the permeable membrane 4 and is decompressed from the solution chamber 3 side. It is transmitted to the chamber 1 side. Therefore, as compared with the case of permeating a liquid component by diffusing and permeating into the permeable membrane as in the non-porous permeable membrane used in the vaporization permeation method described in JP-A-63-162003 and the like, separation The speed of the liquid component to be transmitted through the permeable membrane 4 becomes extremely high, and it becomes possible to obtain a practical level of the transmission speed.

In the present invention, when the decompression chamber 1 is decompressed as described above to perform the liquid separation operation, the cock 9 is further added.
Is opened and a gas such as air is supplied from the pipe 10 to the solution chamber 3 to perform liquid separation operation, thereby enhancing the separation performance of the mixed solution 2. It is not clear why the separation performance improves, but
For example, the following can be considered. That is, the gas such as air supplied to the solution chamber 3 is transferred to the decompression chamber 1 through the pores of the permeable membrane 4 because the decompression chamber 1 is decompressed. Molecules are generally much smaller than the vapor particles of the mixed solution 2 and therefore the permeable membrane 4
Of the mixed solution 2 as a result, each liquid component of the vapor of the mixed solution 2 is hindered by the gas molecules and becomes difficult to enter the pores of the permeable membrane 4, and the vapor of the permeable membrane 4 It is considered that the performance of separating the mixed solution 2 is enhanced because the liquid components of the vapor stay in the vicinity and the liquid separating action of the permeable membrane 4 is sufficiently received. By thus supplying the gas into the solution chamber 3, it is possible to increase the concentration of the liquid component that is permeated through the permeable membrane 4 to be separated, and if the gas supply amount is increased, the separation is accompanied. The performance is improved, and the concentration of the liquid component that permeates the permeable membrane 4 can also be increased. However, as the supply amount of gas is increased, the speed at which the liquid component permeates the permeable membrane 4 becomes slower, and the permeation speed cannot be kept high. Therefore, it is preferable to set the gas supply amount in consideration of the balance between the liquid separation performance in the permeable membrane 4 and the permeation rate. Well
In addition, by depressurizing the decompression chamber 1, the porous permeable membrane 4
The inside of the solution chamber 3 is also in a depressurized state through
When the gas is supplied into the solution chamber 3 in the state, the gas becomes a solution.
It rapidly expands in the chamber 3. And the gas expands rapidly
Then, the heat in the solution chamber 3 is absorbed due to adiabatic expansion,
The vapor evaporating from the mixed solution 2 is cooled in the solution chamber 3.
The vapor becomes a state in which it easily condenses, and the vapor of the mixed solution 2
The speed of passing through the permeable membrane 4 can be reduced. this
Permeation also by the cooling action due to the adiabatic expansion of the gas
The separating action of the liquid by the membrane 4 is performed by each liquid component of vapor of the mixed solution
Is sufficiently received and the performance of separating the mixed solution 2 is improved,
It is also conceivable that there is not.

When performing the liquid separation operation as described above, it is preferable to heat the mixed solution 2 in the solution chamber 3 and cool the permeable membrane 4. As shown in FIG. 1, heating of the mixed solution 2 is performed by immersing the solution chamber 3 in the heating bath 7, or by mounting a heating jacket on the outer periphery of the solution chamber 3,
A heater is installed in the solution chamber 3, and further the separation tank 5
The whole can be heated or can be performed by any method. This heating may be performed by raising the temperature of the mixed solution 2 to a temperature higher than at least the ambient temperature in which the separation tank 5 is placed, and the heating temperature is not regulated at all. The permeable membrane 4 can be cooled by, for example, attaching a jacket 8 around the permeable membrane 4 and passing a coolant through the jacket 8. In this cooling, the temperature of the permeable membrane 4 is the solution chamber 3
Any material can be used as long as it can be kept lower than the liquid temperature of the mixed solution 2. When the liquid separation operation is performed while heating the mixed solution 2 and cooling the permeable membrane 4 as described above,
Mixed solution 2 in which two or more liquid components having different boiling points are mixed, for example, mixed solution 2 of water and ethanol (boiling point 78.3 ° C) or mixed solution 2 of water and methanol (boiling point 64.1 ° C) 2 And the like, which is used as the porous permeable membrane 4 to selectively and preferentially permeate a liquid component having a low boiling point in the mixed solution 2, that is, the surface of the liquid component having a low boiling point in the mixed solution 2. The critical surface tension is close to the tension, the critical surface tension is higher than the surface tension of the liquid component having a low boiling point, and the critical surface tension is not close to the surface tension of the liquid component having a high boiling point in the mixed solution 2; Further, the permeable membrane 4 having a critical surface tension smaller than the surface tension of the liquid component having a high boiling point is used.

In this case, when the decompression chamber 1 is decompressed and the liquid separation operation is performed as described above, when the mixed solution 2 in the solution chamber 3 is heated, the boiling point of each component of the mixed solution 2 is changed. Since the low liquid components are easily evaporated, the permeable membrane 4
Since the vapor reaching the temperature reaches a high concentration of the liquid component having a low boiling point, and the liquid component having a low boiling point has a surface tension smaller than the critical surface tension of the permeable membrane 4, this liquid having a low boiling point gives priority to the permeable membrane 4. As a result, the concentration of the liquid component to be separated by passing through the permeable membrane 4 can be increased, and the separation performance of the mixed solution 2 can be improved. Moreover, at this time, by cooling the permeable membrane 4 as described above,
The separation performance of the mixed solution 2 can be further enhanced. The reason for this is not clear, but the mixed solution 2 in the solution chamber 3
When the vapor evaporated from the vapor reaches the permeable membrane 4, the liquid component having a high boiling point in the vapor is more easily condensed than the liquid component having a low boiling point by the cooling action of the permeable membrane 4, and therefore the liquid component having a high boiling point is easily associated with each other. As a result, the aggregated form of molecules becomes large, and as a result, it becomes more difficult for the liquid component having a high boiling point to permeate through the pores of the permeable membrane 4, and accordingly, the liquid component having a low boiling point passes through the pores of the permeable membrane 4. It is expected that it will be transmitted with higher priority. By thus heating the mixed solution 2 and cooling the permeable membrane 4, it is possible to increase the concentration of the liquid component which is transmitted through the permeable membrane 4 and separated. At this time, when the liquid separation operation is performed by cooling the permeable membrane 4 in this way, the mixed solution 2 is applied to the permeable membrane 4.
The permeable membrane 4 is heated by this vapor due to the action of the vapor that is heated by heating the vapor and the effect obtained by cooling the permeable membrane 4 cannot be sufficiently obtained. By supplying a gas such as air to the permeable membrane 4, the permeable membrane 4 can be cooled by this gas, and also in this respect, the separation performance of the permeable membrane 4 can be enhanced in the present invention.

[0017]

The invention will now be illustrated by the examples. Example As the porous permeable membrane 4, "Duraguard # 2400" manufactured by Hoechst Co. was used. This "Jura Guard # 2
400 "has a thickness of 25μ and a critical surface tension of 35 dyne.
/ Cm porous polypropylene film, the pores are formed as long holes (average diameter 0.079μ) with an average size of major axis × minor axis = 0.125 × 0.05μ,
The porosity is 38%. Then, as the mixed solution 2, 100 cc of a water-ethanol solution containing 10% by weight of ethanol
1, the decompression chamber 1 has a volume of 100 cc, the solution chamber 3 has a volume of 350 cc, and the effective area of the permeable membrane 4 is 20 cm ² .
While heating the permeable membrane 4 with the jacket 8 at 0 ° C. while supplying the room temperature (25 ° C.) air to the solution chamber 3 from the pipe 10, the decompression chamber 1 is decompressed to 10 ⁻¹ Torr. The liquid was separated by depressurizing it with an activated vacuum pump. At this time, the amount of air supplied to the solution chamber 3 is 8 ml / min, 10 ml / min, 20 m
1 / min, 32 ml / min, 44 ml / min, 6
Each was set to 3 ml / min. Then, ethanol has a surface tension of 22.6 dyne / cm and a boiling point of 78.
The surface tension of water is 72.8 dyn, while the temperature is 3 ° C.
Since e / cm 2 and the boiling point were 100 ° C., ethanol was preferentially permeated through the permeable membrane 4, and the liquid in which the concentration of ethanol was increased was collected and collected in the decompression chamber 1.

Comparative Example A liquid separation operation was carried out in the same manner as in Example except that the air was not supplied to the solution chamber 3, and the liquid with the increased concentration of ethanol was collected in the decompression chamber 1. Collected. Conventional example Non-porous polydimethylsiloxane film as a permeable membrane (“SE-952” manufactured by Toray Dow Corning Co., Ltd.
0 ") was used. After that, a liquid separation operation was performed in the same manner as in the comparative example, and the liquid with the increased concentration of ethanol was collected and collected in the decompression chamber 1.

In Examples, Comparative Examples and Conventional Examples, the concentration of ethanol in the liquid recovered from the decompression chamber 1 was measured as the concentration of permeate, and the rate at which this liquid permeated through the permeable membrane 4 was measured as the rate of permeation. The separation coefficient α of was measured. The separation coefficient α is defined by the following equation. α = (Y ₁ / Y ₂ ) / (X ₁ / X ₂ ) where X ₁ and X ₂ are the weight fraction of ethanol and the weight fraction of water of the mixed solution 2 introduced into the solution chamber 3, respectively. ₁ and Y ₂ represent the weight fraction of ethanol and the weight fraction of water of the solution collected in the decompression chamber 1, respectively. Therefore, when α is a numerical value of 1 or more, it permeates the permeable membrane 4. The liquid means that the amount of ethanol is larger than the amount of water, and the larger the value of α, the more preferentially the ethanol permeates the permeable membrane 4. The results of these measurements are shown in Table 2. The relationship between the air supply amount and the permeate concentration and the permeation rate for the examples and comparative examples is shown in the graph of FIG.

[0020]

[Table 2]

As shown in Table 2, the conventional example using the non-porous permeable membrane is difficult to put into practical use because the permeation rate is extremely low, and the comparative example is porous. Since the permeation membrane is used, the permeation rate is high, but the permeate concentration is not sufficient. On the other hand, it was confirmed that in the embodiment in which the porous permeable membrane is used and the air is supplied to the solution chamber, a predetermined level can be obtained for both the permeation rate and the permeate concentration. It Further, as seen in FIG. 2, the permeate concentration can be increased as the amount of air supplied to the solution chamber is increased, but it is confirmed that the permeation rate tends to decrease.

[0022]

As described above, according to the present invention, since a porous membrane having a high affinity for a specific liquid component in the mixed solution is used as the permeable membrane, each liquid of the mixed solution reaching the permeable membrane is used. Of the component vapors, a specific liquid component with a high affinity for the permeable membrane has an affinity for the surface of the permeable membrane and easily permeates through the pores, while other liquid components are repelled by the surface of the permeable membrane and form pores. It is difficult to permeate through the membrane, and it is possible to separate a predetermined liquid component from the mixed solution by the permeable membrane. Moreover, the separated liquid component passes through the pores of the porous permeable membrane and from the decompression chamber side to the solution chamber. The liquid component to be separated permeates the permeable membrane as compared with the case where the liquid component is diffused and permeated into the permeable membrane to allow the separated liquid component to permeate to the side. The transmission speed becomes extremely fast, and it is possible to obtain a practical level of transmission speed. Is shall. Also in the present invention
For example, the gas was supplied to the solution chamber.
And is generally much smaller than the particles of the vapor of the mixed solution
The gas molecules easily enter the pores of the porous permeable membrane.
While passing through the decompression chamber where the pressure is reduced,
The vapor is blocked by the molecules of this gas and enters the pores of the permeable membrane.
It becomes difficult to control the speed at which the vapor of the mixed solution passes through the permeable membrane.
It can be slowed down and the decompression chamber is reduced.
Pressurize the solution chamber through the porous permeable membrane.
It is in a depressurized state, and inside the solution chamber in this depressurized state
When gas is supplied, the gas expands rapidly in the solution chamber.
And absorbs heat in the solution chamber by this adiabatic expansion
However, the vapor evaporated from the mixed solution is cooled in the solution chamber.
It becomes easy to condense and vapor of the mixed solution becomes permeable membrane.
That can slow down the speed at which
Of air molecules and cooling by adiabatic expansion of gas
Combined with the use of a permeable membrane to separate the liquid
You can ensure that each liquid component of the vapor is fully received,
A practical level of permeability is obtained by using a porous permeable membrane.
The performance of separating the mixed solution is high while maintaining the overspeed.
It can be held by a bell.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an improved example of a principle device for liquid separation by a vaporization permeation method used in the present invention.

FIG. 2 is a graph showing a relationship between an air supply amount, a permeate concentration, and a permeation rate.

FIG. 3 is a cross-sectional view showing a principle device of liquid separation by a vaporization permeation method.

[Explanation of symbols]

 1 decompression chamber 2 mixed solution 3 solution chamber 4 permeable membrane

Claims (5)

[Claims] 1. A permeable membrane is provided between a decompression chamber and a solution chamber into which a mixed solution in which a plurality of liquid components are mixed is introduced, and the decompression chamber is decompressed to generate a permeable membrane inside the solution chamber. By passing the vapor of the mixed solution from the solution chamber side to the decompression chamber side through the permeable membrane, when separating a specific liquid component in the mixed solution, the other component of each component in the mixed solution is used as the permeable membrane. A method for separating a mixed solution, which comprises using a porous membrane having a higher affinity for this specific liquid component to be separated than the above, and supplying gas into the solution chamber. 2. A porous membrane having a critical surface tension close to the surface tension of a specific liquid component separated from other components among the components in the mixed solution is used as the permeable membrane. The method for separating a mixed solution according to. 3. A porous membrane having a critical surface tension which is higher than the surface tension of a specific liquid component to be separated in the mixed solution and smaller than the surface tension of other liquid components in the mixed solution as the permeable membrane. The method for separating a mixed solution according to claim 1 or 2, which is characterized. 4. The porous membrane constituting the permeable membrane has an average pore diameter of 1 × 10 ⁻³ to 5 μm and a porosity of 5% or more. The method for separating a mixed solution according to 1. 5. A mixed solution in which the liquid component to be separated has a boiling point lower than the boiling points of other liquid components is used, and the mixed solution in the solution chamber is heated and the permeable membrane is cooled to a temperature lower than this heating temperature. The method for separating a mixed solution according to any one of claims 1 to 4, which is characterized in that.