JP2017200684A - Separation membrane and solute separation module - Google Patents

Abstract

A separation membrane in which a plurality of carbon nanotubes are held by a self-supporting membrane is provided. One embodiment of the present invention is a separation membrane including a plurality of carbon nanotubes 13 and a paraxylylene-based polymer membrane 14 which is a self-supporting membrane embedded between the plurality of carbon nanotubes. [Selection] Figure 1

Description

  The present invention relates to a separation membrane and a solute separation module having carbon nanotubes.

  The shortage of fresh water that is the raw material for clean water is progressing worldwide. Therefore, there is an increasing need for water treatment such as sewage, industrial wastewater, purification of polluted water (black water), and desalination of seawater. On the other hand, there are an evaporation method and a membrane separation method as water purification technologies, but the former is energetically boiling due to the solute and is energy intensive. Although the membrane separation method has been put to practical use, the reverse osmosis membrane used for obtaining highly purified water requires a high-pressure pump, so that a separation membrane having a higher flux is required.

  On the other hand, it has been proposed that a CNT film made of carbon nanotubes (CNT) is formed on the surface of a substrate, and a part of the CNT film is pulled out by tweezers to spin the CNT in a rope shape. For this purpose, Patent Document 1 discloses a technique for forming CNTs in a direction perpendicular to the surface of a substrate.

  Since the inner diameter of CNT is very small, it can be considered to be applied to the separation membrane that performs the above water treatment. However, it is not easy to hold a large number of CNTs in an area suitable for water treatment. Although a separation membrane using vertically grown CNTs has been proposed in Patent Document 2, the area of each membrane is 1 mm or less, which is extremely small and cannot be said to be suitable for industrialization.

JP 2013-6708 A US Patent US8038887

An object of one embodiment of the present invention is to provide either a separation membrane in which a plurality of carbon nanotubes are held by a self-supporting membrane, or a solute separation module using the separation membrane.
Another object of one embodiment of the present invention is to provide either a separation membrane in which a plurality of carbon nanotubes are held by a self-supporting membrane using a polymer, or a solute separation module using the separation membrane.

Hereinafter, various aspects of the present invention will be described.
[1] A separation membrane comprising a plurality of carbon nanotubes and a self-supporting membrane filled with the plurality of carbon nanotubes.

[2] The separation membrane according to [1], wherein the plurality of carbon nanotubes are not in contact with each other, and a mutual interval between the plurality of carbon nanotubes is 1 nm or more.

[2-1] The separation membrane according to the above [2], wherein an interval between the plurality of carbon nanotubes is 3 nm or more.

[3] The separation membrane according to any one of [1], [2], and [2-1], wherein the carbon nanotube has an inner diameter of 10 nm or less.

[3-1] The separation membrane according to [3], wherein the carbon nanotube has an inner diameter of 7 nm or less.
[3-2] The separation membrane according to [3-1], wherein an inner diameter of the carbon nanotube is 4 nm or less.
[3-3] The separation membrane according to [3-2] above, wherein an inner diameter of the carbon nanotube is 2 nm or less.

[4] The above-mentioned [1], [2], [2-1], [3], [3-1], [3-2] and [3-] are characterized in that the self-supporting film is a polymer film. [3] The separation membrane according to any one of [3].
[4-1] The separation membrane according to [4], wherein the self-supporting membrane is a polymer membrane containing carbon.
[4-2] The separation membrane according to [4], wherein the self-supporting membrane is a polymer membrane containing a hydrocarbon.
[5] The above-mentioned [1], [2], [2-1], [3], [3-1], [3-, wherein the self-supporting film is a polymer film containing a perfluoro-based material. The separation membrane according to any one of [2], [3-3] and [4].

[6] Any one of the above-mentioned [4], [4-1], [4-2], [4-3] and [5], wherein the self-supporting film has a thickness of 1 μm or more. The separation membrane according to 1.
[6-1] The separation membrane according to [6], wherein the self-supporting membrane has a thickness of 10 μm or more.
[6-2] The separation membrane according to [6-1], wherein the self-supporting membrane has a thickness of 20 μm or more.

[7] In any one of the above [1] to [6], when a solvent is passed through the separation membrane, a regular structure of solvent molecules occurs inside the carbon nanotube, whereby the carbon nanotube A separation membrane characterized by losing the fluidity of the solvent inside.
In this specification, in one solution, a component dissolved in making the solution is called a solute, and a component used to dissolve the solute is called a solvent. If it is difficult to distinguish between solute and solvent, the solvent that exists in a large amount is used.

[8] The separation membrane according to [7], wherein the temperature at which the ordered structure of the solvent molecules occurs inside the carbon nanotube is in the range of −20 ° C. to 60 ° C.
[8-1] The separation membrane according to [7], wherein the temperature at which the ordered structure of the solvent molecules occurs in the carbon nanotube is in the range of −10 ° C. to 50 ° C.

[8-2] The separation membrane according to [7] above, wherein the temperature at which the ordered structure of the solvent molecules occurs in the carbon nanotube is in the range of 10 ° C to 30 ° C.

[9] The above [1], [2], [2-1], [3], [3-1], [3-2], [3-3], [4], [4-1], [4-2], [4-3], [5], [6], [6-1], [6-2], [7], [8], [8-1] and [8-2] ], When a solvent having a carbon nanotube inner diameter of 4 nm or less is passed through the separation membrane at a temperature of 35 ° C. or higher, a regular structure of solvent molecules does not occur inside the carbon nanotube. A separation membrane.

[10] The above [1], [2], [2-1], [3], [3-1], [3-2], [3], and [2] 3-3], [4], [4-1], [4-2], [4-3], [5], [6], [6-1], [6-2], [7] , [8], [8-1], [8-2] and [9].

[11] The above [1], [2], [2-1], [3], [3-1], [3-2], [3-3], [4], [4-1], [4-2], [4-3], [5], [6], [6-1], [6-2], [7], [8], [8-1], [8-2 ], A separation method for separating the one or more solutes from the fluid by passing a fluid containing one or more solutes through the separation membrane according to any one of [9] and [10]. A solute separation module characterized by being used.
In the present specification, the “solute (particle)” refers to a chemical species that is less likely to permeate the membrane among two or more chemical species contained in a fluid (liquid or gas).

[12] The solute separation module according to [11], wherein the fluid containing the one or more solutes is a liquid or a gas.

[13] a housing;
A first separation membrane disposed in the housing and partitioning the first space and the second space;
The first separation membrane is defined in claim 1, [2], [2-1], [3], [3-1], [3-2], [3-3], [4], [4- 1], [4-2], [4-3], [5], [6], [6-1], [6-2], [7], [8], [8-1], [ 8-2], [9], [10], [11] and the separation membrane according to any one of [12],
A first introduction flow path provided in the housing and connected to the first space into which a liquid containing one or more solutes and a solvent is introduced;
A first discharge flow path provided in the housing, connected to the second space, for discharging the solvent that has passed through the first separation membrane;
A solute separation module comprising:

[14] In the above [13], a second separation membrane disposed in the housing and facing the first separation membrane,
The second separation membrane is the separation membrane according to any one of claims 1 to 16,
The first space is located between the first separation membrane and the second separation membrane;
The second separation membrane partitions the first space and the third space in the housing;
A second discharge channel provided in the housing and connected to the third space;
The solute separation module, wherein the second discharge channel is a channel for discharging the solvent that has passed through the second separation membrane.

[15] In the above [13], the apparatus has a second introduction flow path provided in the housing and connected to the second space, and the second introduction flow path is a flow path for introducing a cleaning liquid. A solute separation module characterized by being.

According to one embodiment of the present invention, it is possible to provide either a separation membrane in which a plurality of carbon nanotubes are held by a self-supporting membrane, or a solute separation module using the separation membrane.
In addition, according to one embodiment of the present invention, it is possible to provide either a separation membrane in which a plurality of carbon nanotubes are held by a self-supporting membrane using a polymer, or a solute separation module using the separation membrane.

(A)-(E) are sectional drawings which show the manufacturing method of the separation membrane which concerns on 1 aspect of this invention. (A)-(D) are perspective views which show the manufacturing method of the separation membrane which concerns on 1 aspect of this invention. (A)-(E) are sectional drawings which show the manufacturing method of the separation membrane which concerns on 1 aspect of this invention. It is a block diagram which shows schematically the thermal CVD apparatus for synthesize | combining the double-walled carbon nanotube shown in FIG. It is a block diagram which shows schematically the film-forming apparatus which forms the paraxylylene-type polymer film shown in FIG. (A)-(C) are the figures for demonstrating reaction in the vaporization furnace of a film-forming apparatus shown in FIG. 5, a decomposition furnace, and a vapor deposition chamber. (A) is a sectional view for schematically illustrating a solute separation module incorporating the separation membrane shown in FIG. 1 and FIG. 2, and illustrating a step of filtering a liquid stock solution, and (B) is a diagram of FIG. 1 and FIG. It is sectional drawing for demonstrating the process which shows typically the solute separation module incorporating the separation membrane shown in 2, and performs back washing | cleaning. (A) is a SEM photograph of the sample of Example 1 in which a large number of DWCNTs were grown on a silicon wafer, and (B) is an SEM photograph in which the upper part of the DWCNT of the sample shown in (A) is enlarged. (A) is the photograph which shows the sample which coat | covered parylene on DWCNT of the sample of FIG. 8, (B) is sectional drawing of the sample shown to (A). It is the photograph which tested the softness | flexibility of the separation membrane of the sample of FIG.9 (C), (D). It is a figure which shows the apparatus for performing a dead end system filtration experiment. It is a figure which shows the relationship between the frequency | count of the permeation | transmission experiment by Example 2, and water flux.

  Hereinafter, embodiments and examples of the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the following description, and it will be easily understood by those skilled in the art that modes and details can be variously changed without departing from the spirit and scope of the present invention. Therefore, the present invention should not be construed as being limited to the description of the embodiments and examples below.

[First Embodiment]
<Method for producing separation membrane>
1A to 1E are cross-sectional views illustrating a method for manufacturing a separation membrane according to one embodiment of the present invention. 2A to 2D are perspective views illustrating a method for manufacturing a separation membrane according to one embodiment of the present invention.

  As shown in FIGS. 1A and 2A, a catalyst layer 12 is formed on a substrate 11. For example, a silicon substrate can be used as the substrate 11. As the catalyst layer 12, a metal catalyst such as iron can be used. Next, the catalyst layer 12 is activated by heating the catalyst layer 12 in an inert atmosphere or a reducing atmosphere.

  Next, a large number of carbon nanotubes (CNT) 13 are formed on the catalyst layer 12 using the thermal CVD apparatus shown in FIG. Many CNTs 13 grow in a direction crossing the substrate 11 (for example, a direction perpendicular to the substrate 11) (see FIGS. 1B and 2B).

Here, the thermal CVD apparatus shown in FIG. 4 will be described.
This thermal CVD apparatus has a vacuum chamber 21 and a vacuum pump (not shown) for evacuating the inside of the vacuum chamber 21. A holding unit 24 that holds the substrate 10 is disposed in the vacuum chamber 21. A heater 23 is disposed below the holding unit 24, and the heater 23 heats the substrate 10 held by the holding unit 24. The thermal CVD apparatus has a supply port 22 for supplying a gas in a shower-like manner, and the supply port 22 is connected to a source gas supply source (not shown) via a gas path.

  The substrate 10 is introduced into the vacuum chamber 21 and the substrate 10 is held in the holding unit 24. Next, the inside of the vacuum chamber 21 is evacuated by a vacuum pump, and a source gas containing carbon is supplied from the supply port 22 to the substrate 10 in a shower shape, so that the inside of the vacuum chamber 21 is predetermined depending on the balance between exhaust and source gas supply. Adjust to the pressure of. Then, the heater 10 heats the substrate 10 to a predetermined temperature. In this way, as shown in FIGS. 1B and 2B, a large number of carbon nanotubes (CNT) 13 are formed on the catalyst layer 12 of the substrate 10.

  Next, the substrate 10 on which the CNTs 13 are formed is taken out from the vacuum chamber 21 of the thermal CVD apparatus.

  The above-mentioned many CNTs 13 are not in contact with each other and are separated from each other, and the mutual interval is preferably 1 nm or more, more preferably 3 nm or more. If the interval between the CNTs 13 is less than 1 nm, when the polymer film 14 is formed, the raw material gas particles are less likely to enter the gaps between the CNTs 13, making it difficult to form the polymer film 14.

  The inner diameter of each of the CNTs 13 is such that the fluid (liquid or gas) can pass but one or more solutes contained in the liquid or gas (solutes that are desired to be separated from the liquid or gas) cannot pass. Specifically, specifically, it is 10 nm or less, preferably 7 nm or less, more preferably 4 nm or less, and still more preferably 2 nm or less. Moreover, the length of CNT13 should just be a length which functions as a separation membrane, for example, may be 50 micrometers and may be 110 micrometers.

  The CNT 13 is preferably a double-walled carbon nanotube (DWCNT). The reason is that non-hydrophilicity is not strong compared with multi-walled carbon nanotubes, so that water permeates into the hollow interior of double-walled carbon nanotubes even if the opening of double-walled carbon nanotubes is not subjected to a hydrophilic treatment. Moreover, it is because a hollow part does not have a structure like a bamboo node like a multi-walled carbon nanotube.

  Thereafter, a polymer film 14 is formed between the CNTs 13 and on the CNTs 13 (see FIGS. 1C and 2C). The polymer film 14 is, for example, a carbon-based polymer film (carbon-containing polymer film), preferably a hydrocarbon-based polymer film (hydrocarbon-containing polymer film), more preferably a film made of polymer polymerized from paraxylylene (paraxylylene). Polymer film). The polymer film 14 may be a polymer film containing a perfluoro material. A parylene film is particularly preferably used as the paraxylylene polymer film. For example, Parylene C has one of the hydrogen atoms in the benzene ring replaced with chlorine, and has a good balance between electrical and physical properties, and is particularly excellent in barrier properties against moisture and corrosive gases. In the case where a paraxylylene polymer film is used as the polymer film 14, it is preferable to form a paraxylylene polymer film between the many CNTs 13 and on the many CNTs 13 by a gas phase polymerization method using the film forming apparatus shown in FIG. . In the following, a case where a paraxylylene polymer film is used as the polymer film 14 will be described.

Here, the film forming apparatus shown in FIG. 5 will be described.
As shown in FIG. 6A, this film forming apparatus includes a vaporizing furnace 31 that vaporizes a solid dimer into dimer gas by heat. The vaporizing furnace 31 is connected to the cracking furnace 32 by piping. The cracking furnace 32 is a furnace that decomposes dimer gas into monomer gas by heat as shown in FIG. The decomposition furnace 32 is connected to the vapor deposition chamber 33 by piping. In the vapor deposition chamber 33, a holding portion 34 for holding the substrate 20 of FIG. The vapor deposition chamber 33 is connected to a vacuum pump 36 via a pipe and a valve 35, and the vacuum pump 36 evacuates the vapor deposition chamber 33. In the vapor deposition chamber 33, as shown in FIG. 6C, a paraxylylene polymer film is formed on the substrate 20 by vapor phase polymerization of monomer gas.

  A solid dimer as a raw material is introduced into the vaporizing furnace 31. The solid dimer is, for example, paraxylylene. Further, the substrate 20 is introduced into the vapor deposition chamber 33, and the substrate 20 is held in the holding unit 34. Next, the valve 35 is opened, the inside of the vapor deposition chamber 33 is evacuated by the vacuum pump 36, and the solid dimer is vaporized into dimer gas by heat in the vaporizing furnace 31. The dimer gas is introduced into the cracking furnace 32 through a pipe, and the dimer gas is decomposed into monomer gas by heat in the cracking furnace 32. The monomer gas is supplied to the vapor deposition chamber 33 through a pipe, and the vapor deposition chamber 33 adjusts the inside of the vapor deposition chamber 33 to a predetermined pressure by the balance between exhaust gas and monomer gas supply. Then, a paraxylylene-based polymer film 14 is formed by vapor phase polymerization between the CNTs 13 on the substrate 20 and on the CNTs 13 at room temperature in the vapor deposition chamber 33 (see FIGS. 1C and 2C). .

  Thereafter, the paraxylylene polymer film 14 and the upper portions of the CNTs 13 are polished (polished), thereby removing the paraxylylene polymer film 14 covering the CNTs 13 and opening the upper portions of the CNTs 13 (FIG. 1 ( D)). Since the upper part of the CNT 13 before polishing is covered with a cap, the CNT 13 can be opened by removing the cap by polishing.

  Next, as shown in FIGS. 1E and 2D, the substrate 11 is peeled from the CNT 13 and the paraxylylene-based polymer film 14. In this way, a separation membrane in which a large number of CNTs 13 are fixed by the paraxylylene polymer membrane 14 can be produced. Both sides of this separation membrane have an asymmetric structure.

  The thickness of the above-mentioned paraxylylene polymer film 14 after polishing is preferably 1 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. Even when a polymer film other than the paraxylylene polymer film is used, the thickness of the polymer film is preferably 1 μm or more, more preferably 10 μm or more, and further preferably 20 μm or more. This is because if the thickness of the polymer film such as the paraxylylene-based polymer film 14 is less than 1 μm, the separation film shown in FIG. That is, the minimum film thickness for a polymer film such as the paraxylylene-based polymer film 14 to function as a self-supporting film is 1 μm (preferably 10 μm).

  The paraxylylene polymer film can be self-supporting with a thickness of 1 μm because the paraxylylene polymer film has flexibility. Even if a hard film having no flexibility such as a silicon nitride film is buried between many CNTs 13, it cannot function as a self-supporting film.

  In the present embodiment, a paraxylylene-based polymer film 14, which is a self-supporting film, is embedded between a large number of CNTs 13 to produce a self-supporting separation membrane. However, a paraxylylene-based polymer film is formed between a large number of CNTs 13. It is also possible to produce a separation membrane by filling a self-supporting membrane other than (such as a polymer membrane such as a carbon-based polymer membrane, a hydrocarbon-based polymer membrane, or a polymer membrane containing a perfluoro-based material). However, the self-supporting film may be a film that has few defects and does not allow water or gas to pass through.

  Further, by using the substrate 11 having a length of 20 mm or more and a width of 20 mm or more, the planar size of each of the paraxylylene polymer membrane 14 and the separation membrane, which are self-supporting membranes, can be 20 mm or more and 20 mm or more. Thereby, the separation membrane which ensured the area suitable for water treatment, such as purification of sewage and industrial wastewater, and desalination of seawater, can be realized. In other words, a separation membrane with a small planar area is not suitable for actually performing a large amount of water treatment.

<Separation method>
By passing a fluid (liquid or gas) containing one or more solutes through the separation membrane, the solute can be separated from the fluid. For example, a liquid (seawater) containing a solute (salt) is passed through a separation membrane. At this time, water passes through the hollow interior of the CNT 13 of the separation membrane, but salt does not pass. The paraxylylene polymer membrane 14 does not pass seawater (water and salt). Therefore, the water that has passed through the hollow interior of the separation membrane CNT 13 and the salt that does not pass through the separation membrane can be separated. In this example, salt and water are separated, but solutes other than salt and water can also be separated, and solutes other than salt and liquids other than water can be separated.

  Further, a gas (for example, air) containing one or more solutes (for example, an organic phosphorus material) is passed through the separation membrane. At this time, air passes through the hollow interior of the CNT 13 of the separation membrane, but organic phosphorus molecules do not pass. The paraxylylene-based polymer film 14 is impermeable to organic phosphorus molecules and air. Therefore, the air that has passed through the hollow interior of the separation membrane CNT 13 and the organic phosphorus that does not pass through the separation membrane can be separated.

<Freezing of hollow carbon nanotubes>
When the inner diameter of the CNT 13 is small, when water (solvent) at room temperature under pressure passes through the hollow interior of the CNT 13 of the separation membrane, the water molecules (solvent molecules) have a regular structure inside the CNT 13. (Regular structuring of the solvent molecules occurs) affects the permeability inside the CNT 13 of the separation membrane, loses the fluidity of water, and enters a frozen state. Further, it is preferable to use a separation membrane in which the temperature at which the regular structure of water molecules occurs inside the CNT 13 when water is passed through the separation membrane is in the range of −20 ° C. to 60 ° C., more preferably −10 ° C. To 50 ° C., more preferably 10 ° C. to 30 ° C.

  Moreover, it can suppress that water (solvent) freezes inside CNT13 by making the water temperature which passes a separation membrane high. Specifically, when the inner diameter of the CNT 13 is 4 nm or less, the temperature of the liquid (liquid containing one or more solutes and water) passed through the separation membrane is considered to be 35 ° C. or higher.

In addition, when the inner diameter of the CNT 13 is large, even when normal temperature water passes through the hollow interior of the CNT 13 of the separation membrane, the water does not freeze inside the CNT 13. Specifically, when the inner diameter of the CNT 13 exceeds 10 nm, the water does not freeze inside the CNT 13 even when the temperature of the liquid (a liquid containing one or more solutes and water) passed through the separation membrane is normal temperature.
In other words, when the above-mentioned liquid at room temperature is passed through the separation membrane having the CNT 13 having an inner diameter of 10 nm or less, a part of the water is frozen inside the CNT 13 and the remaining water passes through the inside of the CNT 13 without freezing. . Then, when the liquid at room temperature is passed through the separation membrane having the inner diameter of the CNT 13 reduced to 4 nm, all the water is frozen inside the CNT 13 and there is no water that can pass through the CNT 13.
When this property is used, it is possible to separate the solute and water by passing the liquid at room temperature through a separation membrane having CNTs 13 having an inner diameter of more than 4 nm and not more than 10 nm. For example, if the liquid at room temperature is passed through the CNT 13 having an inner diameter of 8 nm, a part of water freezes inside the CNT 13, so that the substantial inner diameter of the CNT 13 becomes smaller than 8 nm.
Therefore, by controlling the temperature of the solution that is a liquid that passes through the hollow interior of the CNT 13 within the range where the inner diameter of the CNT 13 is greater than 4 nm and less than or equal to 10 nm, the substantial inner diameter of the CNT 13 can be controlled. It is possible to control the type of solute that is adjusted or blocked. Moreover, it becomes possible to stop the flow of the solute passing through the hollow interior of the CNT by setting the temperature to 20 ° C. or lower.

[Second Embodiment]
3A to 3E are cross-sectional views illustrating a separation membrane manufacturing method according to one embodiment of the present invention. The same parts as those in FIG. 1 are denoted by the same reference numerals, and only different parts will be described.

  As shown in FIG. 3C, a polymer film 14 is formed by vapor phase polymerization between a large number of CNTs 13 and on a large number of CNTs 13. This polymer film 14 is not filled up to the bottom of many CNTs 13. Therefore, a gap is formed between the polymer film 14 and the substrate 10, and both surfaces of the polymer film have an asymmetric structure.

  The thickness of the polymer film 14 after polishing shown in FIG. 3D is preferably 1 μm or more. The reason is that by setting the thickness of the polymer film 14 to 1 μm or more, the polymer film 14 after peeling off the substrate shown in FIG.

[Third Embodiment]
FIGS. 7A and 7B are cross-sectional views schematically showing a solute separation module incorporating the separation membrane shown in FIGS. 1 and 2. FIG. 7A is a diagram for explaining a step of filtering a liquid stock solution, and FIG. 7B is a diagram for explaining a step of performing reverse cleaning.

  As shown in FIG. 7A, the solute separation module has a casing 71, and the casing 71 has a plurality of separation chambers 80. Two separation membranes 72 are arranged opposite to each other in the separation chamber 80, and the separation chamber 80 is divided into three spaces by the two separation membranes 72. The three spaces are a space 73 a facing the separation membrane 72, and two spaces 73 b and 73 c surrounded by the two separation membranes 72 and the inner wall of the separation chamber 80. The space 73a is also referred to as a first space, the space 73b is also referred to as a second space, and the space 73c is also referred to as a third space.

  The solute separation module has a flow path 76 that is continuously connected inside the casing 71, and the flow path 76 is connected to the space 73 a by a first introduction flow path 81. The space 73 a is connected to the discharge channel 75. Each of the spaces 73 b and 73 c is connected to the discharge flow path 74. The discharge channel 74 is also referred to as a first discharge channel or a second discharge channel.

  Next, the process of filtering the stock solution will be described. The stock solution is a liquid containing one or more solutes and a solvent, and is a step of filtering the stock solution by separating the solute and the solvent by passing the stock solution through the separation membrane 72.

  As shown in FIG. 7A, the stock solution 82 to which pressure is applied is supplied to the flow channel 76, and the separation membrane 72 is introduced into the opposing space 73a. When the stock solution 82 in the space 73 a passes through the separation membrane 72 and flows into the spaces 73 b and 73 c, the stock solution 82 is filtered by the separation membrane 72. Thereby, the solute and the solvent are separated, the concentrated solution (solute and part of the solvent) in which the stock solution is concentrated remains in the space 73a, and the filtrate (solvent) flows into the spaces 73b and 73c. As a result, the filtrate in the spaces 73b and 73c is discharged from the discharge flow path 74, and the concentrated liquid in the space 73a is discharged from the discharge flow path 75.

  Next, a cleaning process for removing one or more solutes attached to the separation membrane 72 by passing the cleaning liquid through the separation membrane 72 in the direction opposite to the filtration will be described with reference to FIG. In this cleaning process, a cleaning solution is introduced into the spaces 73b and 73c, and the cleaning solution is passed through the separation membrane to remove solutes attached to the surface of the separation membrane 72 on the space 73a side.

  As shown in FIG. 7B, when the cleaning process is performed, the discharge channel 74 shown in FIG. 7A is closed and the second introduction channel 83 is opened. At this time, the first introduction flow path 81 may be closed. The second introduction channel 83 is a channel connecting the channel 76 and the spaces 73b and 73c.

  The cleaning liquid 77 to which pressure is applied is supplied to a flow path 76 a provided separately from the flow path 76 for supplying the stock solution, and is introduced into the spaces 73 b and 73 c through the second introduction flow path 83. The cleaning liquid 77 in the spaces 73b and 73c passes through the separation membrane 72 and flows into the space 73a. As described above, the cleaning liquid 77 is allowed to flow through the separation membrane 72 from the opposite direction to the filtration, thereby removing one or more solutes adhering to the membrane surface of the separation membrane 72 from the separation membrane 72. The removed solute is discharged together with the cleaning liquid from the space 73a through the discharge channel 75 to the outside. As a result, the separation membrane 72 is washed.

  The separation membrane 72 has a unit having a surface having the same structure. By arranging a plurality of these units, the flow path 76 for supplying the stock solution 82, the flow path 76a for supplying the cleaning liquid 77, the discharge flow path 74 for discharging the filtrate, and the discharge flow path 75 for discharging the concentrated liquid can be efficiently used. It becomes possible to arrange. As a result, the solute separation module becomes compact, and the floor area for installing the apparatus can be greatly saved.

  It should be noted that the first to third embodiments can be implemented by appropriately combining with each other.

  FIG. 8A is an SEM photograph of the sample of Example 1 in which a large number of double-walled carbon nanotubes (DWCNT) were grown vertically on a silicon wafer, and FIG. 8B is shown in FIG. It is the SEM photograph which expanded the upper part of DWCNT of a sample.

The method for producing the sample of FIG. 8 is as follows.
A catalyst layer such as iron was formed on a silicon wafer, and the catalyst layer was heated in a reducing atmosphere to activate the catalyst layer. Next, a number of DWCNTs were grown on the catalyst layer in a direction perpendicular to the surface of the silicon wafer by a thermal CVD method. The length of DWCNT was 100 μm, and the average outer diameter of DWCNT was 4 nm.

  FIG. 9A is a photograph showing a sample in which parylene is coated on the DWCNT of the sample of FIG. 8, and FIG. 9B is a cross-sectional view of the sample shown in FIG. 9A.

A method for producing the samples of FIGS. 9A and 9B is as follows.
A monomer gas was supplied onto the sample DWCNT of FIG. 8 using the film forming apparatus shown in FIG. 5, and a paraxylylene-based polymer film was formed on the DWCNT by a gas phase polymerization method.

  FIG. 9C is an SEM photograph showing an enlarged DWCNT film of the sample obtained by polishing the surface of the paraxylylene polymer film shown in FIGS. 9A and 9B. FIG. ) Is an SEM photograph in which the surface of the paraxylylene polymer film of the sample is enlarged.

The method for producing the samples of FIGS. 9C and 9D is as follows.
By polishing (polishing) the upper part of the paraxylylene polymer film and DWCNT in the samples of FIGS. 9A and 9B, the paraxylylene polymer film covering the DWCNT is removed and the upper parts of many DWCNTs are opened. did. Since the upper part of the DWCNT before polishing is covered with a cap, the DWCNT can be opened by removing the cap by polishing. As shown in FIG. 9D, an opening was observed at the top of the DWCNT.

  Next, the silicon wafer was peeled from the DWCNT and paraxylylene polymer film. In this manner, the sample (separation membrane) shown in FIGS. 9C and 9D in which a large number of DWCNTs are fixed by the paraxylylene-based polymer membrane can be produced. This separation membrane is a self-supporting membrane.

  The distance between the plurality of DWCNTs in the separation membrane was at least 1 nm, and the inner diameter of the DWCNTs was estimated to be 3.33 nm.

  FIG. 10 is a photograph in which the flexibility of the separation membrane of the samples of FIGS. 9C and 9D was tested. Even when the separation membrane was bent 180 °, the separation membrane was not broken. Therefore, it was confirmed that the separation membrane is strong against breakage and highly flexible.

  FIG. 11 is a diagram illustrating a dead-end device. A salt water separation experiment was performed on the separation membrane of the sample shown in FIGS. 9C and 9D using the dead end apparatus shown in FIG. The dead end device has a mantle heater (not shown), and the temperature of the solution (salt water before separation) can be controlled by the mantle heater.

  A solution is supplied onto the separation membrane. In this solution, the solute is NaCl, the solvent is water, and the NaCl concentration is 500 mg / L. The temperature of the solution was 24 ° C. Next, pressure was applied to the solution to separate into water that passed through the separation membrane and NaCl that did not pass through, and the water flux and the removal rate of NaCl in the separation membrane were measured. At this time, the pressure difference between the surfaces of the separation membrane was 0.9 MPa.

As a result of the salt water separation experiment, the water flux was 1.72 L / m ² h, and the removal rate of NaCl was 41.4%. As a result, both the water flux and NaCl removal rate are low. However, since it is considered that not all of the DWCNT of the separation membrane is opened, the water flux can be further increased by improving the opening ratio of the DWCNT. Further, the removal rate of NaCl can be further increased by adjusting the inner diameter of the DWCNT of the separation membrane. Therefore, it was suggested that it is possible to realize a separation membrane having performance that can withstand practical use.

In this example, an experiment was performed in which water was permeated through the separation membrane of the sample of Example 1 using the dead end apparatus shown in FIG. The result is shown in FIG.
FIG. 12 is a diagram showing the relationship between the number of permeation experiments according to Example 2 and the water flux.

The temperature of water was 20 ° C., and the first water permeation experiment was performed on the separation membrane. As a result of this experiment, the water flux was 1.75 L / m ² h.
Subsequently, a second water permeation experiment was performed on the separation membrane with water at 20 ° C. As a result of this experiment, the water flux was 0.55 L / m ² h.
Subsequently, a third water permeation experiment was performed on the separation membrane with water at 20 ° C. As a result of this experiment, the water flux was 0.25 L / m ² h.
Subsequently, a fourth water permeation experiment was performed on the separation membrane with 20 ° C. water. As a result of this experiment, although the pressure difference between the surfaces of the separation membrane increased, water did not permeate through the separation membrane at all.

  After that, even when a water permeation experiment was performed with 20 ° C. water on the separation membrane, water did not permeate the separation membrane at all.

Next, the separation membrane was taken out from the dead end device, the separation membrane was washed with 95% ethanol, and ultrasonic cleaning was performed for 40 minutes. Then, a water permeation experiment was performed on the separation membrane with water at 60 ° C. As a result of this experiment, the water flux was 0.75 L / m ² h.

  From the first to fourth water permeation experiments, it was confirmed that when 20 ° C. water was permeated through the separation membrane, water was adsorbed inside the hollow of DWCNT and water was frozen inside the hollow. In addition, it was confirmed that freezing of water did not occur inside the hollow space of DWCNT even when water whose temperature was raised to 60 ° C. was permeated through the separation membrane.

  According to the present example, when water at 20 ° C. under pressure passes through the hollow inside of the DWCNT of the separation membrane, the regular structure of water molecules occurs inside the DWCNT, so that the permeability inside the DWCNT is obtained. It is considered that the fluidity of water is lost and the water becomes frozen.

  In addition, when the water permeation experiment was performed on the separation membrane with water at 20 ° C. and the water inside the DWCNT was frozen, the water permeation experiment with water at 40 ° C. was performed on the separation membrane. It was confirmed that water inside passed. For this reason, when the inner diameter of the DWCNT is 4 nm or less, the temperature of the liquid (liquid containing one or more solutes and water) passed through the separation membrane is set to 35 ° C. or higher, so that the water is frozen inside the DWCNT. It is thought that it can suppress doing.

  It should be noted that the first to third embodiments and Examples 1 and 2 can be implemented in combination as appropriate.

10, 11, 20 Substrate 12 Catalyst layer 13 Carbon nanotube (CNT)
14 Paraxylylene polymer film 21 Vacuum chamber 22 Supply port 23 Heater 24 Holding part 31 Vaporization furnace 32 Separation furnace 33 Deposition chamber 34 Holding part 35 Valve 36 Vacuum pump 71 Module housing 72 Separation film 73a Space (first space)
73b space (second space)
73c space (third space)
74, 75 Discharge flow path 76, 76a Flow path 77 Cleaning liquid 80 Separation chamber 81 First introduction flow path 82 Stock solution 83 Second introduction flow path

Claims (15)

  A separation membrane comprising a plurality of carbon nanotubes and a self-supporting membrane in which the plurality of carbon nanotubes are filled with each other.   2. The separation membrane according to claim 1, wherein the plurality of carbon nanotubes are not in contact with each other, and a mutual interval between the plurality of carbon nanotubes is 1 nm or more.   The separation membrane according to claim 1 or 2, wherein an inner diameter of the carbon nanotube is 10 nm or less.   The separation membrane according to any one of claims 1 to 3, wherein the self-supporting membrane is a polymer membrane.   The separation membrane according to any one of claims 1 to 4, wherein the self-supporting membrane is a polymer membrane containing a perfluoro-based material.   The separation membrane according to claim 4 or 5, wherein the self-supporting membrane has a thickness of 1 µm or more.   The flow of the solvent according to any one of claims 1 to 6, wherein when a solvent is passed through the separation membrane, a regular structure of solvent molecules occurs in the carbon nanotubes. Separation membrane characterized by loss of sex.   The separation membrane according to claim 7, wherein the temperature at which the ordered structure of the solvent molecules occurs in the carbon nanotube is in the range of −20 ° C. to 60 ° C.   9. The ordered structure of solvent molecules in the carbon nanotubes according to claim 1, when a solvent of 35 ° C. or higher is passed through the separation membrane having an inner diameter of the carbon nanotubes of 4 nm or less. Separation membrane characterized by not occurring.   The separation membrane according to any one of claims 1 to 9, wherein both surfaces of the self-supporting membrane have an asymmetric structure.   A separation method for separating the one or more solutes from the fluid by passing a fluid containing one or more solutes through the separation membrane according to any one of claims 1 to 10. Characteristic solute separation module.   The solute separation module according to claim 11, wherein the fluid containing the one or more solutes is a liquid or a gas. A housing,
A first separation membrane disposed in the housing and partitioning the first space and the second space;
The first separation membrane is the separation membrane according to any one of claims 1 to 12,
A first introduction flow path provided in the housing and connected to the first space into which a liquid containing one or more solutes and a solvent is introduced;
A first discharge flow path provided in the housing, connected to the second space, for discharging the solvent that has passed through the first separation membrane;
A solute separation module comprising: In Claim 13, it has the 2nd separation membrane which is arranged in the case and counters the 1st separation membrane,
The second separation membrane is the separation membrane according to any one of claims 1 to 16,
The first space is located between the first separation membrane and the second separation membrane;
The second separation membrane partitions the first space and the third space in the housing;
A second discharge channel provided in the housing and connected to the third space;
The solute separation module, wherein the second discharge channel is a channel for discharging the solvent that has passed through the second separation membrane.   14. The method according to claim 13, further comprising a second introduction flow path provided in the housing and connected to the second space, wherein the second introduction flow path is a flow path for introducing a cleaning liquid. Solute separation module.