WO2018079604A1 - Nanocarbon separation membrane, composite nanocarbon separation membrane, and production method for nanocarbon separation membrane - Google Patents

Nanocarbon separation membrane, composite nanocarbon separation membrane, and production method for nanocarbon separation membrane Download PDF

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WO2018079604A1
WO2018079604A1 PCT/JP2017/038512 JP2017038512W WO2018079604A1 WO 2018079604 A1 WO2018079604 A1 WO 2018079604A1 JP 2017038512 W JP2017038512 W JP 2017038512W WO 2018079604 A1 WO2018079604 A1 WO 2018079604A1
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separation membrane
graphene oxide
mass
nanocarbon
membrane
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PCT/JP2017/038512
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French (fr)
Japanese (ja)
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知行 福世
ゴメス アーロン モレロス
シルバ ロドルフォ クルス
遠藤　守信
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昭和電工株式会社
国立大学法人信州大学
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Priority to JP2018547721A priority Critical patent/JP6679117B2/en
Publication of WO2018079604A1 publication Critical patent/WO2018079604A1/en

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/10—Supported membranes; Membrane supports
    • B01D69/108—Inorganic support material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
    • B01D69/12—Composite membranes; Ultra-thin membranes
    • B01D69/1214—Chemically bonded layers, e.g. cross-linking
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
    • B01D71/02—Inorganic material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B9/00—Layered products comprising a layer of a particular substance not covered by groups B32B11/00 - B32B29/00
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y40/00—Manufacture or treatment of nanostructures
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/158—Carbon nanotubes
    • C01B32/168—After-treatment
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B32/00—Carbon; Compounds thereof
    • C01B32/15—Nano-sized carbon materials
    • C01B32/182—Graphene
    • C01B32/198—Graphene oxide

Definitions

  • the present invention relates to a nanocarbon separation membrane, a nanocarbon composite separation membrane, and a method for producing a nanocarbon separation membrane.
  • Separation membranes used for water treatment include UF membranes (Ultrafiltration Membrane), NF membranes (Nanofiltration Membrane), RO membranes (Reverse Osmosis Membrane), and There are FO membranes (Forward Osmosis Membrane). Separation membranes are not limited to water treatment, and are widely used for gas separation and the like.
  • Non-Patent Document 1 describes a separation membrane produced by subjecting a dispersion in which graphene oxide pieces are dispersed under reduced pressure.
  • Non-Patent Document 2 describes a separation membrane in which graphene oxide pieces are cross-linked with 1,3,5-benzenetricarbonyl trichloride (TMC).
  • TMC 1,3,5-benzenetricarbonyl trichloride
  • Non-Patent Document 3 describes a method of producing an NF film by filtering a dispersion in which graphene oxide pieces and multi-wall carbon nanotubes (hereinafter referred to as MWCNT) are dispersed under reduced pressure on a porous substrate. ing.
  • MWCNT multi-wall carbon nanotubes
  • the separation membranes described in Non-Patent Document 1 and Non-Patent Document 3 also have a problem that the graphene oxide pieces peel off during use. This is because the graphene oxide pieces are easily dispersed in water or the like.
  • the separation membrane described in Non-Patent Document 2 graphene oxide pieces are cross-linked. Therefore, it is difficult for the graphene oxide pieces to be separated from each other. However, since it is crosslinked by organic molecules, the robustness of the separation membrane cannot be sufficiently increased.
  • the present invention has been made in view of the above circumstances, and an object thereof is to provide a nanocarbon separation membrane excellent in both water permeability and separation performance.
  • the present inventors have found that a nanocarbon separation membrane having excellent separation performance can be obtained by crosslinking a plurality of graphene oxide pieces with divalent cations and inserting double wall carbon nanotubes between the layers. It was. That is, this invention provides the following means in order to solve the said subject.
  • the first aspect of the present invention is a nanocarbon separation membrane described in the following (1).
  • the nanocarbon separation membrane according to the first aspect of the present invention includes a plurality of graphene oxide pieces that are present so as to overlap each other when viewed in the thickness direction and are cross-linked with each other by a divalent cation, and the plurality of graphene oxide pieces Double wall carbon nanotubes inserted between the layers, wherein the mass ratio of the graphene oxide pieces to the total mass of the graphene oxide pieces and the double wall carbon nanotubes is greater than 0% by mass and less than 70% by mass, The mass ratio is 30% by mass or more and less than 100% by mass.
  • the mass ratio of the graphene oxide pieces to the total mass of the graphene oxide pieces and the double wall carbon nanotubes is 30% by mass to 70% by mass, and the double wall carbon 30 mass% or more and 70 mass% or less may be sufficient as the mass ratio of a nanotube.
  • the divalent cation may be a calcium ion.
  • the second aspect of the present invention is the following nanocarbon composite separation membrane described in (4).
  • a nanocarbon composite separation membrane according to the second aspect of the present invention is disposed on the one surface side of the nanocarbon separation membrane according to any one of (1) to (3) above. And a porous membrane that supports the nanocarbon separation membrane.
  • the nanocarbon separation membrane and the porous membrane may be bonded.
  • the nanocarbon separation membrane and the porous membrane may be bonded together by a polyvinyl alcohol membrane.
  • a third aspect of the present invention is a method for producing a nanocarbon separation membrane described in the following (7).
  • a method for producing a nanocarbon separation membrane according to a third aspect of the present invention includes a step of applying a dispersion in which graphene oxide pieces and double-walled carbon nanotubes are dispersed and drying to form a carbon membrane. Immersing the carbon film in a solution in which divalent cations are dissolved.
  • the nanocarbon separation membrane according to the first aspect of the present invention is excellent in separation performance.
  • FIG. 1 It is a perspective schematic diagram which shows the preferable example of the nanocarbon composite separation membrane which concerns on the 1st aspect of this invention. It is a cross-sectional schematic diagram which shows the preferable example of the nanocarbon composite separation membrane which concerns on the 1st aspect of this invention. It is a scanning electron microscope (SEM) image of a graphene oxide piece simple substance. It is a transmission electron microscope (TEM) image of a graphene oxide piece simple substance. It is a transmission electron microscope (TEM) image of a nanocarbon separation membrane. It is a transmission electron microscope (TEM) image of a nanocarbon separation membrane. It is the figure which showed typically the manufacturing method of the nanocarbon composite separation membrane concerning this embodiment.
  • SEM scanning electron microscope
  • TEM transmission electron microscope
  • TEM transmission electron microscope
  • TEM transmission electron microscope
  • TEM transmission electron microscope
  • TEM transmission electron microscope
  • the results of FTIR measurement of Reference Comparative Examples 2, 2-1, and 2-2 are shown.
  • the results of Raman spectroscopic measurements of Reference Comparative Examples 2, 2-1, and 2-2 are shown.
  • required by the XPS measurement of the reference comparative example 2-1 is shown.
  • required by the XPS measurement of the reference comparative example 2-2 is shown.
  • required by the XPS measurement of the reference comparative example 2 is shown.
  • required by the XPS measurement of the reference comparative example 2 is shown.
  • required by the XPS measurement of the reference comparative example 2 is shown.
  • Example 4 is a photograph of the surface of a carbon nanocomposite separation membrane after the treatment of Example 4.
  • 2 is a photograph of the surface of the carbon nanocomposite separation membrane after the treatment of Example 1. The result of having performed FTIR measurement before the heating of a polyvinyl alcohol film and after a heating is shown.
  • FIG. 1 is a schematic perspective view of a nanocarbon composite separation membrane according to the first embodiment of the present invention.
  • FIG. 2 is a schematic cross-sectional view of the nanocarbon composite separation membrane according to the first embodiment of the present invention. In FIG. 1, each component is illustrated separately for easy understanding.
  • the nanocarbon separation membrane 10 is a functional membrane having a high filtration function.
  • the porous membrane 30 is a support membrane that supports the nanocarbon separation membrane 10 and increases the mechanical strength of the nanocarbon composite separation membrane 100 as a whole.
  • the nanocarbon composite separation membrane 100 can be used for both gas phase separation and liquid phase separation depending on the application. Hereinafter, the description will focus on liquid phase separation.
  • the nanocarbon separation membrane 10 includes a graphene oxide (GO (abbreviation of graphene oxide)) piece 1 and a double wall carbon nanotube (hereinafter referred to as “DWCNT” (abbreviation of double wall carbon nanotube)) 2.
  • DWCNT2 is a carbon nanotube having a two-layer structure. DWCNT may have a structure in which at least two carbon nanotubes having different inner diameters overlap each other. Existence of graphene oxide so as to overlap each other when viewed from the thickness direction may mean that at least a part thereof overlaps each other when viewed from the thickness direction.
  • FIG. 3 is a scanning electron microscope (SEM) image of the graphene oxide piece 1 in a single state.
  • FIG. 4 is a transmission electron microscope (TEM) image of the graphene oxide piece 1 in a single state.
  • the graphene oxide piece 1 is a piece of graphene oxide.
  • Graphene oxide is a material in which an oxygen-containing functional group selected from an epoxy group, a carboxyl group, a carbonyl group, a hydroxyl group, and the like is bonded to a monolayer of graphene.
  • Graphene oxide is also known as a material that becomes graphite when reduced.
  • the thickness of the graphene oxide piece 1 is one carbon atom and is about 1 to 1.5 nm.
  • the size of the graphene oxide piece 1 in the in-plane direction can be designed as appropriate.
  • the average diameter in the in-plane direction of the graphene oxide piece 1 shown in FIG. 3 is 12 ⁇ m.
  • the average diameter was determined as follows. First, the dispersion liquid in which the graphene oxide pieces 1 are dispersed is dropped on the Si substrate and dried. Next, the Si substrate is observed with an SEM, and a circumscribed ellipse of the graphene oxide piece 1 is drawn. At this time, the graphene oxide pieces 1 that do not aggregate and cannot draw a circumscribed ellipse are not selected. Then, the major axis of the circumscribed ellipse obtained is measured. The same operation was performed on 90 graphene oxide pieces 1 and the average value was calculated to obtain the average diameter.
  • the graphene oxide piece 1 is partially perforated (see the dotted area in FIG. 4). In other words, one or more holes (openings) may be provided on the surface of the graphene oxide piece 1. This hole functions as a flow path for fluid passing through the nanocarbon separation membrane 10.
  • the diameter and the amount of the holes formed in the graphene oxide piece 1 can be arbitrarily selected, and can be controlled by changing the degree of oxidation of the graphene oxide piece 1.
  • the average diameter of the holes formed in the graphene oxide piece 1 is preferably 0.5 nm or more and 5 nm or less, and more preferably 1 nm or more and 3 nm or less.
  • the area of the pores is preferably 0.5% or more and 5% or less in the area of graphene oxide (GO).
  • FIG. 5 is a transmission electron microscope (TEM) image of a nanocarbon separation membrane, which is a preferred example of the present invention.
  • TEM transmission electron microscope
  • FIG. 6 is a transmission electron microscope (TEM) image of the nanocarbon separation membrane, and is an enlarged view of a part of FIG.
  • TEM transmission electron microscope
  • a part of DWCNT 2 can be confirmed through a hole (see the dotted line region in FIG. 6), and the other part can be confirmed through a carbon atom constituting graphene oxide piece 1. That is, the DWCNT 2 is present behind the graphene oxide piece 1.
  • the hole portion there is a portion where a dot of carbon atoms is confirmed inside the hole. That is, the graphene oxide piece 1 is present behind the DWCNT 2 in the drawing. That is, the DWCNT 2 is sandwiched between the graphene oxide pieces 1 that are present so as to overlap each other when viewed from the thickness direction.
  • DWCNT 2 has a diameter of about several nanometers to several tens of nanometers and is thicker than the thickness of the graphene oxide piece 1. Therefore, when at least one DWCNT 2 is sandwiched between the plurality of graphene oxide pieces 1, the interval between the stacked graphene oxide pieces 1 increases.
  • the diameter of DWCNT2, the innermost inner diameter of DWCNT2, and the length of DWCNT2 may be arbitrarily selected.
  • the average inter-plane distance of the graphene oxide piece is 7.7 mm.
  • the average inter-surface distance becomes 7.7 mm or more.
  • the average inter-surface distance is obtained from a peak value obtained by X-ray diffraction. Note that the average inter-plane distance of the graphene oxide pieces in the nanocarbon separation membrane of the present invention can be arbitrarily changed by changing conditions and the like.
  • the flow path of the fluid passing through the nanocarbon separation membrane 10 increases. That is, in the case of liquid phase separation, water permeability increases.
  • the spread of the average inter-surface distance is in units of ridges and is slight. Therefore, it is possible to avoid the deterioration of the separation characteristics of the separation object.
  • the mass ratio of the graphene oxide piece 1 to the total mass of the graphene oxide pieces and the double wall carbon nanotubes is 70% by mass or less and greater than 0% by mass. Moreover, the mass ratio of DWCNT2 with respect to the total mass of a graphene oxide piece and a double wall carbon nanotube is 30 to 100 mass%. When the ratio of the graphene oxide piece 1 and the DWCNT 2 is within this range, it is possible to avoid that the performance of one of the water permeability or the separation characteristic of the separation object is significantly deteriorated.
  • the mass ratio of the graphene oxide piece 1 to the total mass of the graphene oxide pieces and the double wall carbon nanotubes is preferably 30% by mass or more and 70% by mass or less, and more preferably 40% by mass or more and 70% by mass or less. More preferably, the content is 50% by mass or more and 70% by mass or less.
  • the mass ratio of DWCNT2 to the total mass of graphene oxide pieces and double-walled carbon nanotubes is preferably 30% by mass to 70% by mass, more preferably 30% by mass to 60% by mass, and more preferably 30% by mass. More preferably, the content is from 50% to 50% by weight.
  • the sum total of the mass ratio of the graphene oxide piece 1 and DWCNT2 will be 100 mass%.
  • the plurality of graphene oxide pieces 1 are cross-linked with each other by a divalent cation.
  • the graphene oxide piece 1 has at least one oxygen-containing functional group selected from an epoxy group, a carboxyl group, a carbonyl group, a hydroxyl group, and the like.
  • the divalent cation is coordinated in the vicinity of the oxygen-containing functional group of the graphene oxide pieces 1 and bridges adjacent graphene oxide pieces 1.
  • the graphene oxide piece 1 is highly dispersible in water. Therefore, if the graphene oxide pieces 1 are simply laminated, the graphene oxide pieces 1 may be separated from the nanocarbon separation film 10 when water is passed through. In particular, in the case of cross flow in which water flows in a direction parallel to the membrane surface of the nanocarbon separation membrane 10, the graphene oxide piece 1 is easily peeled off.
  • the divalent cation is not particularly limited as long as it can contribute to crosslinking. From the viewpoint of availability, at least one of calcium ions and magnesium ions is preferable.
  • the nanocarbon separation membrane 10 according to this embodiment is excellent in both water permeability and separation characteristics of the separation object as a separation membrane.
  • the graphene oxide pieces 1 are cross-linked with a divalent cation. For this reason, peeling of the graphene oxide piece 1 is suppressed during use. Therefore, the solution can be supplied to the nanocarbon separation membrane 10 by crossflow.
  • the thickness of the nanocarbon separation membrane may be arbitrarily selected.
  • the porous membrane 30 is disposed on one side of the nanocarbon separation membrane 10.
  • the porous membrane 30 supports the nanocarbon separation membrane 10 and increases the mechanical strength of the nanocarbon composite separation membrane 100 as a whole.
  • the porous film 30 has a hole 31 therein.
  • the hole 31 By having the hole 31 inside, it has water permeability in the thickness direction.
  • the hole part 31 does not need to be a hole part extended in the thickness direction as shown to a figure.
  • a connecting hole in which a plurality of minute holes are connected may be used.
  • porous membrane 30 a known porous substrate can be selected and used as long as it has water permeability and mechanical strength.
  • a resin film made of polyimide, polysulfone, polyethersulfone, or the like and having communication holes, porous alumina, or the like can be used as the porous film 30.
  • the adhesive layer 20 described later is formed by crosslinking with heat or light, it is particularly preferable to use polysulfone having high heat resistance.
  • the thickness of the porous membrane may be arbitrarily selected.
  • the adhesive layer 20 adheres the nanocarbon separation membrane 10 and the porous membrane 30.
  • a material capable of adhering the nanocarbon separation membrane 10 and the porous membrane 30 without significantly inhibiting water permeability can be used.
  • the adhesive layer material can be selected arbitrarily.
  • polyvinyl alcohol or the like can be used. Uncrosslinked polyvinyl alcohol is provided between the nanocarbon separation membrane 10 and the porous membrane 30, and these can be bonded by crosslinking the polyvinyl alcohol.
  • the nanocarbon separation membrane 10 When performing a dead-end flow in which liquid is passed from a direction perpendicular to the in-plane direction of the nanocarbon composite separation membrane 100, the nanocarbon separation membrane 10 hardly peels from the porous membrane 30. On the other hand, when performing the cross flow which lets a liquid flow from a parallel direction with respect to the in-plane direction of the nanocarbon composite separation membrane 100, the nanocarbon separation membrane 10 becomes easy to peel from the porous membrane 30. Therefore, in the case where liquid is passed through the nanocarbon composite separation membrane 100 by crossflow, it is particularly preferable to provide the adhesive layer 20.
  • the thickness of the adhesive layer may be arbitrarily selected.
  • the nanocarbon composite separation membrane 100 includes the nanocarbon separation membrane 10 having excellent water permeability and separation characteristics of the separation object. For this reason, it has excellent separation characteristics.
  • the mechanical strength of the nanocarbon composite separation membrane 100 can be increased by supporting one surface of the nanocarbon separation membrane 10 with the porous membrane 30. Furthermore, by bonding the nanocarbon separation membrane 10 and the porous membrane 30 with the adhesive layer 20, it is possible to prevent the nanocarbon separation membrane 10 from being peeled off during use.
  • FIG. 7 is a view schematically showing a method for producing a nanocarbon composite separation membrane according to the present embodiment.
  • the nanocarbon composite separation membrane 100 includes a step of forming the adhesive layer 20 on one surface of the porous membrane 30, and an adhesive layer 20. Forming a nanocarbon separation membrane 10 on the surface on which is formed.
  • the nanocarbon separation membrane 10 includes a step of applying a dispersion liquid in which graphene oxide pieces 1 and DWCNT2 are dispersed to the surface of the porous membrane 30 on which the adhesive layer 20 is formed, and drying to form a carbon membrane; Dipping the membrane in a solution in which divalent cations are dissolved.
  • the thickness of the graphene oxide piece 1 used for production can be arbitrarily selected, but is preferably about 1 to 1.5 nm. You may select arbitrarily the average diameter (outer diameter) of DWCNT2 used for manufacture. Further, the innermost inner diameter of the DWCNT 2 may be arbitrarily selected. The length of DWCNT2 may be arbitrarily selected.
  • the mass ratio of the graphene oxide piece 1 to the total mass of the graphene oxide piece 1 and the DWCNT 2 can be arbitrarily selected, but is preferably 30% by mass or more and 70% by mass or less, for example, 40% by mass or more and 70% More preferably, it is 50 mass% or less, and it is especially preferable that it is 50 to 70 mass%.
  • the mass ratio of DWCNT2 to the total mass of graphene oxide pieces and double-walled carbon nanotubes can be arbitrarily selected, but is preferably 30% by mass to 70% by mass, and more preferably 30% by mass to 60% by mass. Is more preferable, and 30% by mass or more and 50% by mass or less is particularly preferable.
  • a porous film 30 is prepared.
  • the porous membrane 30 is selected from the above-described ones.
  • the adhesive layer 20 is formed on one surface of the porous film 30.
  • the adhesive layer 20 can be formed by means such as coating.
  • the adhesive layer 20 can be formed on one surface of the porous film 30 by immersing the porous film 30 in an aqueous polyvinyl alcohol solution, or applying the aqueous solution to the film and drying it.
  • the dispersion 11 in which the graphene oxide pieces 1 and the DWCNTs 2 are dispersed is applied to the surface on which the adhesive layer 20 is formed.
  • the application method is not particularly limited. You may use it arbitrarily selecting from well-known methods. For example, when spray coating is performed from the nozzle, a shearing force is applied to the dispersion 11 at the nozzle tip, and the dispersibility of the graphene oxide pieces 1 and the DWCNT 2 is increased.
  • the dispersion 11 is obtained, for example, by mixing a first dispersion in which the graphene oxide pieces 1 are dispersed and a second dispersion in which DWCNT2 is dispersed.
  • the first dispersion is obtained by the following procedure, for example.
  • the graphene oxide piece 1 is obtained by a known method (for example, a method described in Patent Document 1 or Non-Patent Document 4) using graphite as a raw material.
  • the graphene oxide piece 1 is highly dispersible in water. For this reason, a 1st dispersion liquid is obtained only by adding to water.
  • DWCNT2 is produced.
  • DWCNT2 can be produced by a general synthesis method.
  • CVD methods include a substrate method and a gas phase flow method.
  • the substrate method includes a method of synthesizing carbon nanotubes on a substrate on which a metal layer having a thickness of several nanometers to several ⁇ m is deposited, and a method of synthesizing carbon nanotubes by supporting transition metal part particles on a simple substance such as zeolite or ceramic. .
  • the gas phase flow method is a method of synthesizing carbon nanotubes by reacting catalyst fine particles and a raw material gas in a high temperature zone in a reaction tube.
  • the catalyst fine particles are obtained by spraying the precursor compound onto the reaction tube and thermally decomposing the precursor compound at the reaction tube inlet.
  • the catalyst fine particles and the raw material gas are sent into the reaction tube by the carrier gas.
  • a method for producing DWCNT described in Patent Document 2, Patent Document 3, and the like is given as an example.
  • the DWCNT 2 thus produced is added to an aqueous solution selected as necessary to obtain a second dispersion.
  • aqueous solution for example, a sodium polystyrene sulfonate (PSS) aqueous solution, a sodium dodecyl sulfate aqueous solution, a sodium deoxycholate aqueous solution, or the like can be used.
  • PSS sodium polystyrene sulfonate
  • a sodium dodecyl sulfate aqueous solution a sodium deoxycholate aqueous solution, or the like
  • the first dispersion and the second dispersion are mixed and diluted if necessary to obtain the dispersion 11.
  • the coated dispersion 11 is dried, for example, naturally dried to obtain a carbon film.
  • the carbon film is preferably heated together with the porous film 30.
  • the adhesive layer is cross-linked by heat
  • polyvinyl alcohol when used as the adhesive layer, the polyvinyl alcohol of the adhesive layer 20 is cross-linked by heating, and the adhesion between the carbon film and the porous film 30 is increased. Also exhibits water resistance. Also, excess water can be removed.
  • the carbon film formed by applying the dispersion 11 is immersed in a solution in which divalent cations are dissolved.
  • divalent cations for example, when calcium ions are used as divalent cations, they are immersed in a solution in which calcium chloride is dissolved.
  • the solvent of the solution may be arbitrarily selected.
  • the divalent cation can be arbitrarily selected, and examples thereof include calcium ions and magnesium ions.
  • a predetermined nanocarbon separation membrane can be easily obtained.
  • a nanocarbon composite separation membrane can be easily obtained by using this method for producing a nanocarbon separation membrane.
  • the fluid of the nanocarbon separation membrane can be obtained simply by mixing the first dispersion in which the graphene oxide pieces 1 are dispersed and the second dispersion in which the DWCNT2 is dispersed. It is possible to control the flow path through which the gas flows. That is, the water permeability and separation performance of the nanocarbon separation membrane can be easily controlled.
  • the nanocarbon separation membrane can be produced by applying a dispersion liquid. Therefore, it is easy to increase the area of the nanocarbon separation membrane.
  • the nanocarbon separation membrane, the nanocarbon composite separation membrane, and the method for producing the nanocarbon separation membrane have been described above.
  • the present invention may be variously modified without changing the gist of the invention.
  • Example 1 As Example 1, a nanocarbon composite separation membrane having a nanocarbon separation membrane composed of 30% by mass of graphene oxide pieces and 70% by mass of DWCNT was prepared. Specifically, the nanocarbon composite separation membrane of Example 1 was produced by the following procedure.
  • a first dispersion in which graphene oxide pieces having an average diameter of 12 ⁇ m were dispersed was prepared using graphite (product number 332461 manufactured by Sigma-Aldrich) as a raw material.
  • the first dispersion was prepared as follows.
  • the liquid that was allowed to stand was separated into a supernatant and a precipitate.
  • the supernatant was removed by decantation to obtain a precipitate.
  • the obtained precipitate was added to a 5% by mass H 2 SO 4 aqueous solution (1 L) and dispersed.
  • the operation of adding the dispersion into pure water, centrifuging, and then dispersing in pure water was repeated 5 times to clean the dispersion medium.
  • the precipitate after centrifugation becomes two layers.
  • the lower layer was graphite that was not exfoliated from each other, and the upper layer was that the exfoliated graphene oxide pieces absorbed water.
  • a first dispersion having a solid content concentration of 0.9% by mass was obtained.
  • the obtained first dispersion was diluted with water and dropped onto the Si substrate and dried, the sample was observed by SEM. As a result, the average diameter of the graphene oxide pieces was 12 ⁇ m.
  • DWCNT outer diameter 1.8 nm, inner diameter 1.2 nm by TEM observation
  • the diameter of DWCNT in the second dispersion was about several nm.
  • the obtained first dispersion and second dispersion were mixed and diluted to obtain a dispersion.
  • nanocarbon composed of graphene oxide pieces and DWCNT is dispersed.
  • the composition ratio of the nanocarbon in the dispersion was 30% by mass for graphene oxide pieces and 70% by mass for DWCNT.
  • the concentration of nanocarbon relative to the solvent was 0.8 mg / mL.
  • a commercially available polysulfone membrane (Alfa Label: GR40PP, size 50 mm ⁇ 50 mm) was prepared as a porous membrane. Then, the polysulfone film was immersed in a 1% by mass aqueous polyvinyl alcohol solution (manufactured by Sigma-Aldrich: molecular weight 31,000-50,000, 98-99% saponified product) for 1 hour. The polysulfone membrane after immersion was air-dried in an upright state. As a result, polyvinyl alcohol was coated on the surface of the polysulfone film.
  • the dispersion was sprayed onto the porous film coated with polyvinyl alcohol using an air brush (manufactured by Anest Iwata: HP-BCS). Thereafter, the porous film was dried in an air atmosphere at 100 ° C. for 1 hour. At this time, the polyvinyl alcohol was cross-linked, and the porous film and the carbon film formed by drying the dispersion were adhered.
  • the obtained laminated film was immersed in a calcium chloride solution for 1 hour.
  • the calcium chloride solution had a calcium chloride concentration of 5% by mass, and the solvent of the calcium chloride solution was a mixture of ethanol and water in a volume ratio of 1: 3.
  • the laminated film after immersion was dried. The drying was performed by air-drying, then immersed in ethanol for 1 hour and then air-dried again.
  • Example 2 nanocarbon composite separation membranes were prepared in the same procedure as in Example 1 except that the mixing ratio of the first dispersion and the second dispersion was changed.
  • the composition ratio of the obtained nanocarbon separation membrane is as follows.
  • Example 2 Graphene oxide pieces (50 mass%), DWCNT (50 mass%)
  • Example 3 Graphene oxide pieces (70 mass%), DWCNT (30 mass%)
  • Comparative Example 1 a nanocarbon composite separation membrane was prepared in the same procedure as in Example 1 except that the mixing ratio of the first dispersion and the second dispersion was changed.
  • the composition ratio of the nanocarbon separation membrane of Comparative Example 1 was 90% by mass of graphene oxide pieces and 10% by mass of DWCNT.
  • Comparative Example 2 In Comparative Example 2, a nanocarbon composite separation membrane was prepared in the same procedure as in Example 1 except that only the first dispersion was used and the second dispersion was not used. That is, the composition ratio of the nanocarbon separation membrane of Comparative Example 2 was 100% by mass of graphene oxide pieces.
  • Comparative Example 3 a nanocarbon composite separation membrane was prepared in the same procedure as in Example 1 except that only the second dispersion liquid was used and the first dispersion liquid was not used. That is, the composition ratio of the nanocarbon separation membrane of Comparative Example 3 was set to 100% by mass of DWCNT.
  • the water permeability was calculated from the results of water permeability measurement at a pressure of 5.0 MPa.
  • the NaCl removal rate was obtained by cutting out the membrane into a circle having a diameter of 25 mm and using a cross flow filter (manufactured by Tosk Corporation).
  • NaCl removal rate [%] ⁇ 1-NaCl concentration of permeated water [mass%] / NaCl concentration of raw water [mass%] ⁇ ⁇ 100
  • Table 1 shows the measurement results.
  • GO indicates graphene oxide pieces
  • DWCNT indicates double wall carbon nanotubes
  • PVA indicates polyvinyl alcohol.
  • the nanocarbon composite separation membranes of Examples 1 to 3 in which the ratio of the graphene oxide pieces to DWCNT is in a predetermined range are more permeable than the nanocarbon composite separation membranes of Comparative Examples 1 and 2.
  • the amount was greatly improved.
  • the NaCl removal rate slightly decreased, depending on the application, about 40% was sufficient, and a sufficient NaCl removal rate was exhibited.
  • Applications include, for example, nanofiltration membranes for divalent ion removal and organic matter separation. In Comparative Example 3 consisting only of DWCNT, water freely flowed and no desalting performance was confirmed.
  • Reference Comparative Example 2-1 The sample of Reference Comparative Example 2 was immersed before being immersed in the calcium chloride solution, and the sample was heated at 100 ° C. (hereinafter referred to as Reference Comparative Example 2-2: No immersion in the calcium chloride solution) ) And three samples.
  • Reference Comparative Example 2 the dispersion used in Comparative Example 2 was applied on a Si substrate instead of the porous film, and the same procedure including immersion in a calcium chloride solution was performed. A separation membrane was formed.
  • a reference comparative example what was formed on the Si substrate will be referred to as a reference comparative example.
  • Reference Comparative Example 2 corresponds to one produced under the same conditions as Comparative Example 2, and the other reference examples and reference comparative examples also have the same correspondence.
  • FIG. 8 shows the results of FTIR measurement of Reference Comparative Examples 2, 2-1, and 2-2.
  • FTIR was performed by the total reflection measurement (ATR) method.
  • the comparative example 2 in which the CaCl 2 treatment was performed has the intensity of the C—O and C ⁇ O peaks compared to the reference comparative example 2-1 before the treatment. It's down. This is because the relative intensity of C—O and C ⁇ O peak with respect to the C ⁇ C peak is reduced by coordination of Ca 2+ ions with oxygen ions.
  • FIG. 9 shows the results of Raman spectroscopic measurement in Reference Comparative Examples 2, 2-1, and 2-2.
  • the D (1350 cm ⁇ 1 ) / G (1600 cm ⁇ 1 ) ratio in the result of Raman spectroscopic measurement was 0.92 in Reference Comparative Example 2-1, 0.84 in Reference Comparative Example 2-2, and 0 in Reference Comparative Example 2. .87.
  • Reference Comparative Example 2-2 is obtained by heating Reference Comparative Example 2-1 at 100 ° C., and it is considered that a part of the graphene oxide was reduced by heating and approached the graphite structure.
  • the D / G ratio of the reference comparative example 2 is large. It is considered that the disorder of the crystal arrangement was caused by the coordination of calcium ions.
  • 10A to 10C show analysis results of C1s spectra obtained by XPS measurement in Reference Comparative Examples 2, 2-1, and 2-2.
  • 10A shows the analysis result of Reference Comparative Example 2-1
  • FIG. 10B shows the analysis result of Reference Comparative Example 2-2
  • FIG. 10C shows the analysis result of Reference Comparative Example 2.
  • FIG. 11A and 11B show the analysis results of the Cl2p spectrum and Ca2p spectrum obtained by XPS measurement in Reference Comparative Example 2.
  • FIG. 11A shows the analysis result of the Cl2p spectrum
  • FIG. 11B shows the analysis result of the Ca2p spectrum.
  • Example 4 differs from Example 1 in that the polysulfone film is not immersed in an aqueous polyvinyl alcohol solution in the production process of Example 1.
  • a 0.2% concentration sodium chloride aqueous solution was fed to the carbon nanocomposite separation membranes of Example 1 and Example 4 at a flow rate of 300 ml / min at a pressure of 2 to 5 MPa by cross flow.
  • FIG. 12A and 12B are photographs of the surface of the carbon nanocomposite separation membrane after the treatment in Example 1 and Example 4.
  • FIG. 12A is a photograph of the surface of the carbon nanocomposite separation membrane of Example 4 23 hours after the start of supplying the sodium chloride aqueous solution.
  • FIG. 12B is a surface photograph of the carbon nanocomposite separation membrane of Example 1 after 70 hours from the start of supply of the sodium chloride aqueous solution.
  • the carbon nanoseparation membrane is peeled off by the flow of the supplied liquid (portion shown by the arrow in FIG. 12A).
  • the carbon nanocomposite separation membrane of Example 1 did not peel off.
  • the adhesive layer it is possible to suppress the separation of the carbon nanoseparation membrane from the carbon nanocomposite separation membrane.
  • the liquid is supplied to the carbon nanocomposite separation membrane by crossflow, it is preferable to provide an adhesive layer.
  • a liquid or gas is supplied in a dead end flow, it can be used without an adhesive layer.
  • FIG. 13 shows the results of FTIR measurement before and after heating polyvinyl alcohol. As shown in FIG. 13, when normalized by the 854 cm ⁇ 1 peak, the peak at 1141 cm ⁇ 1 increased. This indicates the curing of the polyvinyl alcohol film by heat. That is, the polyvinyl alcohol film is sufficiently crosslinked when it is dried for 1 hour in an atmosphere of 100 degrees.
  • An object of the present invention is to provide a nanocarbon separation membrane excellent in both water permeability and separation performance.
  • Nanocarbon separation membrane 1 Graphene oxide pieces, 2 Double wall carbon nanotube (DWCNT), 10 Nanocarbon separation membrane, 11 Dispersion 20 Adhesive layer, 30 porous membrane, 31 holes, 100 Nanocarbon composite separation membrane

Abstract

This nanocarbon separation membrane is provided with a plurality of graphene oxide pieces that are provided in a mutually overlapping manner when viewed from the thickness direction and that are cross-linked together by divalent cations, and double-walled carbon nanotubes that are inserted between the layers of the plurality of graphene oxide pieces. Relative to the total mass of the graphene oxide pieces and the double-walled carbon nanotubes, the mass ratio of the graphene oxide pieces is more than 0 mass% to 70 mass%, and the mass ratio of the double-walled carbon nanotubes is 30 mass% to less than 100 mass%.

Description

ナノカーボン分離膜、ナノカーボン複合分離膜及びナノカーボン分離膜の製造方法Nanocarbon separation membrane, nanocarbon composite separation membrane, and method for producing nanocarbon separation membrane
　本発明は、ナノカーボン分離膜、ナノカーボン複合分離膜及びナノカーボン分離膜の製造方法に関する。
　本願は、２０１６年１０月２６日に、日本に出願された特願２０１６－２０９８４１号に基づき優先権を主張し、その内容をここに援用する。 The present invention relates to a nanocarbon separation membrane, a nanocarbon composite separation membrane, and a method for producing a nanocarbon separation membrane.
This application claims priority based on Japanese Patent Application No. 2016-209841 filed in Japan on October 26, 2016, the contents of which are incorporated herein by reference.
　水処理に用いられる分離膜（水処理膜）には、ＵＦ膜（Ｕｌｔｒａｆｉｌｔｒａｔｉｏｎ　Ｍｅｍｂｒａｎｅ：限外ろ過膜）、ＮＦ膜（Ｎａｎｏｆｉｌｔｒａｔｉｏｎ　Ｍｅｍｂｒａｎｅ：ナノろ過膜）、ＲＯ膜（ＲｅｖｅｒｓｅＯｓｍｏｓｉｓ　Ｍｅｍｂｒａｎｅ：逆浸透膜）、及びＦＯ膜（Ｆｏｒｗａｒｄ　Ｏｓｍｏｓｉｓ　Ｍｅｍｂｒａｎｅ：正浸透膜）などがある。また分離膜は水処理に限られず、ガスの分離等にも広く用いられている。 Separation membranes (water treatment membranes) used for water treatment include UF membranes (Ultrafiltration Membrane), NF membranes (Nanofiltration Membrane), RO membranes (Reverse Osmosis Membrane), and There are FO membranes (Forward Osmosis Membrane). Separation membranes are not limited to water treatment, and are widely used for gas separation and the like.
　近年、耐薬品性、耐熱性、及び耐久性等のロバスト性（robustness）を高めるために、分離膜にナノカーボン材料を用いる検討が進められている。 In recent years, in order to improve robustness such as chemical resistance, heat resistance, and durability, studies using nanocarbon materials for separation membranes are in progress.
　例えば、非特許文献１には、酸化グラフェン片が分散した分散液を減圧濾過して作製した分離膜が記載されている。また例えば、非特許文献２には、酸化グラフェン片を１，３，５－ベンゼントリカルボニルトリクロライド（ＴＭＣ）で架橋した分離膜が記載されている。また例えば、非特許文献３には、酸化グラフェン片とマルチウォールカーボンナノチューブ（以下、ＭＷＣＮＴという）とが分散した分散液を多孔質基材上で減圧濾過し、ＮＦ膜を作製する方法が記載されている。
　なお酸化グラフェン片の製造方法としては、グラファイトを原料とした方法が知られている（例えば、特許文献１や非特許文献４に記載の方法参照）。 For example, Non-Patent Document 1 describes a separation membrane produced by subjecting a dispersion in which graphene oxide pieces are dispersed under reduced pressure. For example, Non-Patent Document 2 describes a separation membrane in which graphene oxide pieces are cross-linked with 1,3,5-benzenetricarbonyl trichloride (TMC). Further, for example, Non-Patent Document 3 describes a method of producing an NF film by filtering a dispersion in which graphene oxide pieces and multi-wall carbon nanotubes (hereinafter referred to as MWCNT) are dispersed under reduced pressure on a porous substrate. ing.
In addition, as a manufacturing method of a graphene oxide piece, the method using graphite as a raw material is known (for example, refer to the method described in Patent Literature 1 and Non-Patent Literature 4).
特開２０１４－２０１４９２号公報JP 2014-201492 A 特開２０１３－１８６７３号公報JP 2013-18673 A 特開２００５－３４３７２６号公報JP 2005-343726 A
　しかしながら、いずれの分離膜もその特性が充分とは言えなかった。分離膜に求められる性能や特性の一つとして、透水性能と、分離対象物の分離性能がある。これらは、いずれか一方を高めようとすると、他方が低下する相関関係を有し、透水性能と分離対象物の分離性能の両方を充分満たす分離膜は得られていなかった。 However, none of the separation membranes has sufficient characteristics. As one of the performance and characteristics required for the separation membrane, there are water permeability performance and separation performance of the separation object. These have a correlation in which when one of them is increased, the other decreases, and a separation membrane that sufficiently satisfies both the water permeation performance and the separation performance of the separation object has not been obtained.
　また非特許文献１及び非特許文献３に記載の分離膜は、酸化グラフェン片が使用途中に剥離するという問題も有する。酸化グラフェン片は、水等に分散しやすいためである。一方、非特許文献２に記載の分離膜は、酸化グラフェン片同士が架橋されている。そのため、酸化グラフェン片同士が剥離することは生じにくい。しかしながら、有機分子により架橋しているため、分離膜のロバスト性を充分高めることができない。 Further, the separation membranes described in Non-Patent Document 1 and Non-Patent Document 3 also have a problem that the graphene oxide pieces peel off during use. This is because the graphene oxide pieces are easily dispersed in water or the like. On the other hand, in the separation membrane described in Non-Patent Document 2, graphene oxide pieces are cross-linked. Therefore, it is difficult for the graphene oxide pieces to be separated from each other. However, since it is crosslinked by organic molecules, the robustness of the separation membrane cannot be sufficiently increased.
　本発明は、上記事情に鑑みてなされたものであり、透水性と分離性能とが共に優れたナノカーボン分離膜を提供することを目的とする。 The present invention has been made in view of the above circumstances, and an object thereof is to provide a nanocarbon separation membrane excellent in both water permeability and separation performance.
　本発明者らは、二価のカチオンにより複数の酸化グラフェン片を架橋し、その層間にダブルウォールカーボンナノチューブが挿入されていることで、分離性能に優れたナノカーボン分離膜が得られることを見出した。すなわち、本発明は、上記課題を解決するため、以下の手段を提供する。 The present inventors have found that a nanocarbon separation membrane having excellent separation performance can be obtained by crosslinking a plurality of graphene oxide pieces with divalent cations and inserting double wall carbon nanotubes between the layers. It was. That is, this invention provides the following means in order to solve the said subject.
　本発明の第一の態様は、以下の（１）に述べるナノカーボン分離膜である。
（１）本発明の第一の態様のナノカーボン分離膜は、厚み方向からみて互いに重なり合うように存在し、二価のカチオンによって互いに架橋された複数の酸化グラフェン片と、前記複数の酸化グラフェン片の層間に挿入されたダブルウォールカーボンナノチューブと、を備え、酸化グラフェン片及びダブルウォールカーボンナノチューブの合計質量に対する酸化グラフェン片の質量比が０質量％より大きく７０質量％以下であり、ダブルウォールカーボンナノチューブの質量比が３０質量％以上１００質量％未満である。 The first aspect of the present invention is a nanocarbon separation membrane described in the following (1).
(1) The nanocarbon separation membrane according to the first aspect of the present invention includes a plurality of graphene oxide pieces that are present so as to overlap each other when viewed in the thickness direction and are cross-linked with each other by a divalent cation, and the plurality of graphene oxide pieces Double wall carbon nanotubes inserted between the layers, wherein the mass ratio of the graphene oxide pieces to the total mass of the graphene oxide pieces and the double wall carbon nanotubes is greater than 0% by mass and less than 70% by mass, The mass ratio is 30% by mass or more and less than 100% by mass.
（２）上記（１）に記載のナノカーボン分離膜において、酸化グラフェン片及びダブルウォールカーボンナノチューブとの合計質量に対する酸化グラフェン片の質量比が３０質量％以上７０質量％以下であり、ダブルウォールカーボンナノチューブの質量比が３０質量％以上７０質量％以下であってもよい。 (2) In the nanocarbon separation membrane according to (1), the mass ratio of the graphene oxide pieces to the total mass of the graphene oxide pieces and the double wall carbon nanotubes is 30% by mass to 70% by mass, and the double wall carbon 30 mass% or more and 70 mass% or less may be sufficient as the mass ratio of a nanotube.
（３）上記（１）または（２）のいずれかに記載のナノカーボン分離膜において、前記二価のカチオンが、カルシウムイオンであってもよい。 (3) In the nanocarbon separation membrane according to (1) or (2) above, the divalent cation may be a calcium ion.
本発明の第二の態様は、（４）に述べる以下のナノカーボン複合分離膜である。
（４）本発明の第二の態様のナノカーボン複合分離膜は、上記（１）～（３）のいずれか一つに記載のナノカーボン分離膜と、前記ナノカーボン分離膜の一面側に配設され、前記ナノカーボン分離膜を支持する多孔質膜と、を有する。 The second aspect of the present invention is the following nanocarbon composite separation membrane described in (4).
(4) A nanocarbon composite separation membrane according to the second aspect of the present invention is disposed on the one surface side of the nanocarbon separation membrane according to any one of (1) to (3) above. And a porous membrane that supports the nanocarbon separation membrane.
（５）上記（４）に記載のナノカーボン複合分離膜において、前記ナノカーボン分離膜と前記多孔質膜とが、接着されていてもよい。 (5) In the nanocarbon composite separation membrane according to (4) above, the nanocarbon separation membrane and the porous membrane may be bonded.
（６）上記（５）に記載のナノカーボン複合分離膜において、前記ナノカーボン分離膜と前記多孔質膜とが、ポリビニルアルコール膜によって接着されていてもよい。 (6) In the nanocarbon composite separation membrane according to (5) above, the nanocarbon separation membrane and the porous membrane may be bonded together by a polyvinyl alcohol membrane.
本発明の第三の態様は、以下の（７）に述べるナノカーボン分離膜の製造方法である。
（７）本発明の第三の態様のナノカーボン分離膜の製造方法は、酸化グラフェン片と、ダブルウォールカーボンナノチューブと、が分散した分散液を塗付、乾燥し、カーボン膜を形成する工程と、前記カーボン膜を二価のカチオンが溶解した溶液に浸漬する工程と、を有する。 A third aspect of the present invention is a method for producing a nanocarbon separation membrane described in the following (7).
(7) A method for producing a nanocarbon separation membrane according to a third aspect of the present invention includes a step of applying a dispersion in which graphene oxide pieces and double-walled carbon nanotubes are dispersed and drying to form a carbon membrane. Immersing the carbon film in a solution in which divalent cations are dissolved.
　本発明の第一の態様に係るナノカーボン分離膜は、分離性能に優れる。 The nanocarbon separation membrane according to the first aspect of the present invention is excellent in separation performance.
本発明の第一の態様に係るナノカーボン複合分離膜の好ましい例を示す斜視模式図である。It is a perspective schematic diagram which shows the preferable example of the nanocarbon composite separation membrane which concerns on the 1st aspect of this invention. 本発明の第一の態様に係るナノカーボン複合分離膜の好ましい例を示す断面模式図である。It is a cross-sectional schematic diagram which shows the preferable example of the nanocarbon composite separation membrane which concerns on the 1st aspect of this invention. 酸化グラフェン片単体の走査型電子顕微鏡（ＳＥＭ）画像である。It is a scanning electron microscope (SEM) image of a graphene oxide piece simple substance. 酸化グラフェン片単体の透過型電子顕微鏡（ＴＥＭ）画像である。It is a transmission electron microscope (TEM) image of a graphene oxide piece simple substance. ナノカーボン分離膜の透過型電子顕微鏡（ＴＥＭ）画像である。It is a transmission electron microscope (TEM) image of a nanocarbon separation membrane. ナノカーボン分離膜の透過型電子顕微鏡（ＴＥＭ）画像である。It is a transmission electron microscope (TEM) image of a nanocarbon separation membrane. 本実施形態にかかるナノカーボン複合分離膜の製造方法を模式的に示した図である。It is the figure which showed typically the manufacturing method of the nanocarbon composite separation membrane concerning this embodiment. 参考比較例２、２－１，２－２のＦＴＩＲ測定の結果を示す。The results of FTIR measurement of Reference Comparative Examples 2, 2-1, and 2-2 are shown. 参考比較例２、２－１，２－２のラマン分光測定の結果を示す。The results of Raman spectroscopic measurements of Reference Comparative Examples 2, 2-1, and 2-2 are shown. 参考比較例２－１のＸＰＳ測定により求められたＣ１ｓスペクトルの分析結果を示す。The analysis result of the C1s spectrum calculated | required by the XPS measurement of the reference comparative example 2-1 is shown. 参考比較例２－２のＸＰＳ測定により求められたＣ１ｓスペクトルの分析結果を示す。The analysis result of the C1s spectrum calculated | required by the XPS measurement of the reference comparative example 2-2 is shown. 参考比較例２のＸＰＳ測定により求められたＣ１ｓスペクトルの分析結果を示す。The analysis result of the C1s spectrum calculated | required by the XPS measurement of the reference comparative example 2 is shown. 参考比較例２のＸＰＳ測定により求められたＣｌ２ｐスペクトルの分析結果を示す。The analysis result of the Cl2p spectrum calculated | required by the XPS measurement of the reference comparative example 2 is shown. 参考比較例２のＸＰＳ測定により求められたＣａ２ｐスペクトルの分析結果を示す。The analysis result of the Ca2p spectrum calculated | required by the XPS measurement of the reference comparative example 2 is shown. 実施例４の処理後のカーボンナノ複合分離膜の表面の写真である。4 is a photograph of the surface of a carbon nanocomposite separation membrane after the treatment of Example 4. 実施例１の処理後のカーボンナノ複合分離膜の表面の写真である。2 is a photograph of the surface of the carbon nanocomposite separation membrane after the treatment of Example 1. ポリビニルアルコール膜の加熱前及び加熱後にＦＴＩＲ測定を行った結果を示す。The result of having performed FTIR measurement before the heating of a polyvinyl alcohol film and after a heating is shown.
　以下に本願発明の好ましい例や好ましい実施形態について説明する。なお本発明はこれら例や実施形態のみに限定されるものではない。本発明の範囲内において、必要に応じて好ましく変更及び／又は追加することも可能である。特に制限の無い限り、数、量、材料、形状、位置、種類などを必要に応じて変更、追加、省略してもよい。なお、以下の説明で用いる図面は、特徴をわかりやすくするために、便宜上、部分や構成を拡大や縮小や変形や省略をして示している場合がある。
＜ナノカーボン複合分離膜＞
　図１は、本発明の第一の態様に係るナノカーボン複合分離膜の斜視模式図である。図２は、本発明の第一の態様に係るナノカーボン複合分離膜の断面模式図である。図１では、理解を容易にするために、各構成要素を離して図示している。 Preferred examples and preferred embodiments of the present invention will be described below. In addition, this invention is not limited only to these examples and embodiment. Within the scope of the present invention, modifications and / or additions can be made as necessary. As long as there is no restriction | limiting in particular, you may change, add, and abbreviate | omit number, quantity, material, a shape, a position, a kind, etc. as needed. Note that in the drawings used in the following description, in order to make the features easy to understand, for the sake of convenience, portions and configurations may be shown enlarged, reduced, modified, or omitted.
<Nanocarbon composite separation membrane>
FIG. 1 is a schematic perspective view of a nanocarbon composite separation membrane according to the first embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the nanocarbon composite separation membrane according to the first embodiment of the present invention. In FIG. 1, each component is illustrated separately for easy understanding.
　図１及び図２に示すナノカーボン複合分離膜１００は、ナノカーボン分離膜１０と、接着層２０と、多孔質膜３０とを有する。ナノカーボン分離膜１０は、高いろ過機能を有する機能膜である。多孔質膜３０はナノカーボン分離膜１０を支持し、ナノカーボン複合分離膜１００全体としての機械的強度を高める支持膜である。ナノカーボン複合分離膜１００は、気相分離、液相分離のいずれにも用途に応じて用いることができる。以下、液相分離を中心に説明する。 1 and 2 includes a nanocarbon separation membrane 10, an adhesive layer 20, and a porous membrane 30. The nanocarbon separation membrane 10 is a functional membrane having a high filtration function. The porous membrane 30 is a support membrane that supports the nanocarbon separation membrane 10 and increases the mechanical strength of the nanocarbon composite separation membrane 100 as a whole. The nanocarbon composite separation membrane 100 can be used for both gas phase separation and liquid phase separation depending on the application. Hereinafter, the description will focus on liquid phase separation.
（ナノカーボン分離膜）
　ナノカーボン分離膜１０は、酸化グラフェン（ＧＯ（Graphene oxideの略））片１と、ダブルウォールカーボンナノチューブ（以下、「ＤＷＣＮＴ」という。（Double Wall Carbon Nanotubeの略））２と、を備える。ＤＷＣＮＴ２は、２層構造のカーボンナノチューブである。ＤＷＣＮＴは少なくとも内径の異なる２つのカーボンナノチューブが重なった構造を有しても良い。酸化グラフェンが厚み方向からみて互いに重なり合うように存在するとは、厚み方向からみて互いに少なくとも一部が重なることを意味しても良い。 (Nanocarbon separation membrane)
The nanocarbon separation membrane 10 includes a graphene oxide (GO (abbreviation of graphene oxide)) piece 1 and a double wall carbon nanotube (hereinafter referred to as “DWCNT” (abbreviation of double wall carbon nanotube)) 2. DWCNT2 is a carbon nanotube having a two-layer structure. DWCNT may have a structure in which at least two carbon nanotubes having different inner diameters overlap each other. Existence of graphene oxide so as to overlap each other when viewed from the thickness direction may mean that at least a part thereof overlaps each other when viewed from the thickness direction.
　図３は、酸化グラフェン片１の単体の状態にある走査型電子顕微鏡（ＳＥＭ）画像である。また図４は、酸化グラフェン片１の単体の状態にある透過型電子顕微鏡（ＴＥＭ）画像である。 FIG. 3 is a scanning electron microscope (SEM) image of the graphene oxide piece 1 in a single state. FIG. 4 is a transmission electron microscope (TEM) image of the graphene oxide piece 1 in a single state.
　酸化グラフェン片１は、酸化グラフェンの一片である。酸化グラフェンは、グラフェンの単分子層にエポキシ基、カルボキシル基、カルボニル基、及び水酸基などから選択される酸素含有官能基が結合した材料である。酸化グラフェンは、還元するとグラファイトになる材料としても知られている。 The graphene oxide piece 1 is a piece of graphene oxide. Graphene oxide is a material in which an oxygen-containing functional group selected from an epoxy group, a carboxyl group, a carbonyl group, a hydroxyl group, and the like is bonded to a monolayer of graphene. Graphene oxide is also known as a material that becomes graphite when reduced.
　酸化グラフェン片１の厚みは、炭素原子一層分であり、１～１．５ｎｍ程度である。酸化グラフェン片１の面内方向の大きさは、適宜設計することができる。　図３に示す酸化グラフェン片１の面内方向の平均径は、１２μｍである。 The thickness of the graphene oxide piece 1 is one carbon atom and is about 1 to 1.5 nm. The size of the graphene oxide piece 1 in the in-plane direction can be designed as appropriate. The average diameter in the in-plane direction of the graphene oxide piece 1 shown in FIG. 3 is 12 μm.
　ここで平均径は、以下のようにして求めた。まず、酸化グラフェン片１が分散した分散液をＳｉ基板上に滴下し、乾燥する。次いで、Ｓｉ基板をＳＥＭで観察し、酸化グラフェン片１の外接楕円を描く。この際、酸化グラフェン片１は、凝集して外接楕円を描けないものは選択しない。そして、得られた外接楕円の長径を測定する。同様の作業を９０個の酸化グラフェン片１に対して行い、平均値を算出することで平均径を求めた。 Here, the average diameter was determined as follows. First, the dispersion liquid in which the graphene oxide pieces 1 are dispersed is dropped on the Si substrate and dried. Next, the Si substrate is observed with an SEM, and a circumscribed ellipse of the graphene oxide piece 1 is drawn. At this time, the graphene oxide pieces 1 that do not aggregate and cannot draw a circumscribed ellipse are not selected. Then, the major axis of the circumscribed ellipse obtained is measured. The same operation was performed on 90 graphene oxide pieces 1 and the average value was calculated to obtain the average diameter.
　酸化グラフェン片１は、一部に孔が開いている（図４の点線の領域参照）。言い換えると、酸化グラフェン片１の表面には1つ以上の穴（開口部）が設けられていて良い。この孔は、ナノカーボン分離膜１０を通過する流体の流路として機能する。 The graphene oxide piece 1 is partially perforated (see the dotted area in FIG. 4). In other words, one or more holes (openings) may be provided on the surface of the graphene oxide piece 1. This hole functions as a flow path for fluid passing through the nanocarbon separation membrane 10.
　酸化グラフェン片１に形成された孔の径及び孔の量は任意に選択でき、酸化グラフェン片１の酸化度を変えることで制御できる。酸化グラフェン片１に形成された孔の平均径は、０．５ｎｍ以上５ｎｍ以下であることが好ましく、１ｎｍ以上３ｎｍ以下であることがより好ましい。
孔の面積は、酸化グラフェン（ＧＯ）の面積の中の０．５％以上５％以下であることが好ましい。 The diameter and the amount of the holes formed in the graphene oxide piece 1 can be arbitrarily selected, and can be controlled by changing the degree of oxidation of the graphene oxide piece 1. The average diameter of the holes formed in the graphene oxide piece 1 is preferably 0.5 nm or more and 5 nm or less, and more preferably 1 nm or more and 3 nm or less.
The area of the pores is preferably 0.5% or more and 5% or less in the area of graphene oxide (GO).
　図５は、本発明の好ましい例である、ナノカーボン分離膜の透過型電子顕微鏡（ＴＥＭ）画像である。
　図５に示すように、ナノカーボン分離膜中の、ＤＷＣＮＴ２は長さが５００ｎｍ以上であり、隣接するＤＷＣＮＴ２の間の距離は、最大で１００ｎｍ程度である。 FIG. 5 is a transmission electron microscope (TEM) image of a nanocarbon separation membrane, which is a preferred example of the present invention.
As shown in FIG. 5, DWCNT2 in the nanocarbon separation membrane has a length of 500 nm or more, and the distance between adjacent DWCNT2 is about 100 nm at the maximum.
　図６は、ナノカーボン分離膜の透過型電子顕微鏡（ＴＥＭ）画像であり、図５の一部を拡大した図である。 FIG. 6 is a transmission electron microscope (TEM) image of the nanocarbon separation membrane, and is an enlarged view of a part of FIG.
　図６に示すように、ＴＥＭ画像では、酸化グラフェン片１の孔（図６の点線の領域参照）の見え方に違いがある。これは、紙面手前側の酸化グラフェン片１の孔と、紙面奥側の酸化グラフェン片１の孔と、のいずれを見ているかが、異なるためである。換言すると、酸化グラフェン片１が厚み方向から見て、互いに重なるように存在していることをこの画像は示している。なお、互いに重なるように存在するとは、酸化グラフェン片の少なくとも一部が重なりあっていることを意味する。 As shown in FIG. 6, in the TEM image, there is a difference in how the holes of the graphene oxide pieces 1 (see the dotted line area in FIG. 6) are seen. This is because which one of the holes of the graphene oxide piece 1 on the front side of the paper and the hole of the graphene oxide piece 1 on the back side of the paper is viewed is different. In other words, this image shows that the graphene oxide pieces 1 are present so as to overlap each other when viewed from the thickness direction. Note that the presence so as to overlap with each other means that at least a part of the graphene oxide pieces overlap each other.
　また図６では、ＤＷＣＮＴ２の一部が、孔（図６の点線の領域参照）を介して確認でき、その他の部分は、酸化グラフェン片１を構成する炭素原子を介して確認できる。すなわち、ＤＷＣＮＴ２は、酸化グラフェン片１より、紙面奥に存在している。また孔の部分に着目すると、孔の内部にも炭素原子のドットが確認される部分がある。すなわち、ＤＷＣＮＴ２より紙面奥側に酸化グラフェン片１は存在している。つまり、ＤＷＣＮＴ２は、厚み方向から見て互いに重なるように存在する酸化グラフェン片１の間に挟まれている。 In FIG. 6, a part of DWCNT 2 can be confirmed through a hole (see the dotted line region in FIG. 6), and the other part can be confirmed through a carbon atom constituting graphene oxide piece 1. That is, the DWCNT 2 is present behind the graphene oxide piece 1. When attention is paid to the hole portion, there is a portion where a dot of carbon atoms is confirmed inside the hole. That is, the graphene oxide piece 1 is present behind the DWCNT 2 in the drawing. That is, the DWCNT 2 is sandwiched between the graphene oxide pieces 1 that are present so as to overlap each other when viewed from the thickness direction.
　ＤＷＣＮＴ２は、直径が数ｎｍ～数十ｎｍ程度であり、酸化グラフェン片１の厚みより厚い。そのため、複数の酸化グラフェン片１の間に少なくとも一つのＤＷＣＮＴ２が挟まれると、積層される酸化グラフェン片１の間隔が広がる。なおＤＷＣＮＴ２の直径、ＤＷＣＮＴ２の最も内側の内径、及びＤＷＣＮＴ２の長さは任意に選択してよい。 DWCNT 2 has a diameter of about several nanometers to several tens of nanometers and is thicker than the thickness of the graphene oxide piece 1. Therefore, when at least one DWCNT 2 is sandwiched between the plurality of graphene oxide pieces 1, the interval between the stacked graphene oxide pieces 1 increases. The diameter of DWCNT2, the innermost inner diameter of DWCNT2, and the length of DWCNT2 may be arbitrarily selected.
　酸化グラフェン片１のみからなる場合の酸化グラフェン片の平均面間距離は７．７Åである。ＤＷＣＮＴ２が挟まることで、平均面間距離は７．７Å以上となる。平均面間距離は、Ｘ線回折によって得られるピーク値から求められる。なお本発明のナノカーボン分離膜における酸化グラフェン片の平均面間距離は、条件等を変更することによって、任意に変更できる。 When the graphene oxide piece 1 alone is used, the average inter-plane distance of the graphene oxide piece is 7.7 mm. By sandwiching DWCNT2, the average inter-surface distance becomes 7.7 mm or more. The average inter-surface distance is obtained from a peak value obtained by X-ray diffraction. Note that the average inter-plane distance of the graphene oxide pieces in the nanocarbon separation membrane of the present invention can be arbitrarily changed by changing conditions and the like.
　酸化グラフェン片１の平均面間距離が広がることで、ナノカーボン分離膜１０を通過する流体の流路が広がる。すなわち、液相分離の場合は透水性が高まる。一方で、平均面間距離の広がりは、Å単位であり僅かである。そのため、分離対象物の分離特性が大きく劣化することが避けられる。 As the average inter-surface distance of the graphene oxide piece 1 increases, the flow path of the fluid passing through the nanocarbon separation membrane 10 increases. That is, in the case of liquid phase separation, water permeability increases. On the other hand, the spread of the average inter-surface distance is in units of ridges and is slight. Therefore, it is possible to avoid the deterioration of the separation characteristics of the separation object.
　酸化グラフェン片及びダブルウォールカーボンナノチューブの合計質量に対する酸化グラフェン片１の質量比は７０質量％以下０質量％より大きい。また酸化グラフェン片及びダブルウォールカーボンナノチューブの合計質量に対するＤＷＣＮＴ２の質量比は３０質量％以上１００質量％未満である。酸化グラフェン片１とＤＷＣＮＴ２の比率がこの範囲内であると、透水性又は分離対象物の分離特性の一方の性能が著しく低下することを避けられる。 The mass ratio of the graphene oxide piece 1 to the total mass of the graphene oxide pieces and the double wall carbon nanotubes is 70% by mass or less and greater than 0% by mass. Moreover, the mass ratio of DWCNT2 with respect to the total mass of a graphene oxide piece and a double wall carbon nanotube is 30 to 100 mass%. When the ratio of the graphene oxide piece 1 and the DWCNT 2 is within this range, it is possible to avoid that the performance of one of the water permeability or the separation characteristic of the separation object is significantly deteriorated.
　また酸化グラフェン片及びダブルウォールカーボンナノチューブの合計質量に対する酸化グラフェン片１の質量比は、３０質量％以上７０質量％以下であることが好ましく、４０質量％以上７０質量％以下であることがより好ましく、５０質量％以上７０質量％以下であることがさらに好ましい。また酸化グラフェン片及びダブルウォールカーボンナノチューブの合計質量に対するＤＷＣＮＴ２の質量比は、３０質量％以上７０質量％以下であることが好ましく、３０質量％以上６０質量％以下であることがより好ましく、３０質量％以上５０質量％以下であることがさらに好ましい。なお、酸化グラフェン片１とＤＷＣＮＴ２の質量比の合計は１００質量％となる。 Further, the mass ratio of the graphene oxide piece 1 to the total mass of the graphene oxide pieces and the double wall carbon nanotubes is preferably 30% by mass or more and 70% by mass or less, and more preferably 40% by mass or more and 70% by mass or less. More preferably, the content is 50% by mass or more and 70% by mass or less. The mass ratio of DWCNT2 to the total mass of graphene oxide pieces and double-walled carbon nanotubes is preferably 30% by mass to 70% by mass, more preferably 30% by mass to 60% by mass, and more preferably 30% by mass. More preferably, the content is from 50% to 50% by weight. In addition, the sum total of the mass ratio of the graphene oxide piece 1 and DWCNT2 will be 100 mass%.
　また複数の酸化グラフェン片１同士は、二価のカチオンにより互いに架橋されている。酸化グラフェン片１は、エポキシ基、カルボキシル基、カルボニル基、及び水酸基などから選択される少なくとも１種の酸素含有官能基を有している。
二価のカチオンは、酸化グラフェン片１の酸素含有官能基の近傍に配位し、隣接する酸化グラフェン片１どうしを架橋する。複数の酸化グラフェン片１が架橋されると、ナノカーボン分離膜１０が強固になる。 The plurality of graphene oxide pieces 1 are cross-linked with each other by a divalent cation. The graphene oxide piece 1 has at least one oxygen-containing functional group selected from an epoxy group, a carboxyl group, a carbonyl group, a hydroxyl group, and the like.
The divalent cation is coordinated in the vicinity of the oxygen-containing functional group of the graphene oxide pieces 1 and bridges adjacent graphene oxide pieces 1. When the plurality of graphene oxide pieces 1 are cross-linked, the nanocarbon separation membrane 10 becomes strong.
　一般に酸化グラフェン片１は、水に対する分散性が高い。そのため、単純に酸化グラフェン片１を積層しただけでは、通水した際にナノカーボン分離膜１０から酸化グラフェン片１が剥離することがある。特に、ナノカーボン分離膜１０の膜面に対して平行な方向に通水するクロスフローの場合において、酸化グラフェン片１は剥離しやすくなる。 Generally, the graphene oxide piece 1 is highly dispersible in water. Therefore, if the graphene oxide pieces 1 are simply laminated, the graphene oxide pieces 1 may be separated from the nanocarbon separation film 10 when water is passed through. In particular, in the case of cross flow in which water flows in a direction parallel to the membrane surface of the nanocarbon separation membrane 10, the graphene oxide piece 1 is easily peeled off.
　酸化グラフェン片１同士を架橋することで、酸化グラフェン片１の剥離を抑制できる。
また酸化グラフェン片１間に挟まれるＤＷＣＮＴ２も、層間から脱離し難くなる。 By cross-linking the graphene oxide pieces 1, peeling of the graphene oxide pieces 1 can be suppressed.
Further, the DWCNT 2 sandwiched between the graphene oxide pieces 1 is also difficult to be detached from the layers.
　二価のカチオンは、架橋に寄与できるものであれば、そのイオン種は問わない。入手の容易性等の観点からは、カルシウムイオン、及びマグネシウムイオンの少なくとも１種が好ましい。 The divalent cation is not particularly limited as long as it can contribute to crosslinking. From the viewpoint of availability, at least one of calcium ions and magnesium ions is preferable.
　上述のように、本実施形態にかかるナノカーボン分離膜１０は、ＤＷＣＮＴ２によって酸化グラフェン片１の層間が適切に広げられている。そのため、本実施形態にかかるナノカーボン分離膜１０は、分離膜として、透水性及び分離対象物の分離特性のいずれも優れる。 As described above, in the nanocarbon separation membrane 10 according to this embodiment, the interlayer of the graphene oxide pieces 1 is appropriately expanded by the DWCNT 2. Therefore, the nanocarbon separation membrane 10 according to the present embodiment is excellent in both water permeability and separation characteristics of the separation object as a separation membrane.
　また酸化グラフェン片１同士は二価のカチオンにより架橋されている。このため、使用途中で酸化グラフェン片１の剥離が抑制されている。そのため、溶液をナノカーボン分離膜１０に対してクロスフローで供給することができる。
　なおナノカーボン分離膜の厚さは任意に選択してよい。 Further, the graphene oxide pieces 1 are cross-linked with a divalent cation. For this reason, peeling of the graphene oxide piece 1 is suppressed during use. Therefore, the solution can be supplied to the nanocarbon separation membrane 10 by crossflow.
The thickness of the nanocarbon separation membrane may be arbitrarily selected.
(多孔質膜)
　多孔質膜３０は、ナノカーボン分離膜１０の一面側に配設される。多孔質膜３０は、ナノカーボン分離膜１０を支持し、ナノカーボン複合分離膜１００全体としての機械的強度を高める。 (Porous membrane)
The porous membrane 30 is disposed on one side of the nanocarbon separation membrane 10. The porous membrane 30 supports the nanocarbon separation membrane 10 and increases the mechanical strength of the nanocarbon composite separation membrane 100 as a whole.
　多孔質膜３０は、図１及び図２に示すように、内部に孔部３１を有する。内部に孔部３１を有することで、厚み方向に透水性を有する。なお、孔部３１は、図に示すような厚み方向に延在する孔部である必要はない。実際には微小な孔が複数連結した連結孔であってもよい。 As shown in FIGS. 1 and 2, the porous film 30 has a hole 31 therein. By having the hole 31 inside, it has water permeability in the thickness direction. In addition, the hole part 31 does not need to be a hole part extended in the thickness direction as shown to a figure. Actually, a connecting hole in which a plurality of minute holes are connected may be used.
　多孔質膜３０は、透水性と機械的強度を有すれば、公知の多孔質基材を選択し用いることができる。例えば、ポリイミド、ポリサルフォン、又はポリエーテルサルフォン等からなり連通孔を有する樹脂の膜や、ポーラスアルミナ等を、多孔質膜３０として用いることができる。後述する接着層２０を、熱や光等による架橋により形成する場合は、耐熱性の高いポリサルフォンの使用が特に好ましい。多孔質膜の厚さは任意に選択してよい。 As the porous membrane 30, a known porous substrate can be selected and used as long as it has water permeability and mechanical strength. For example, a resin film made of polyimide, polysulfone, polyethersulfone, or the like and having communication holes, porous alumina, or the like can be used as the porous film 30. When the adhesive layer 20 described later is formed by crosslinking with heat or light, it is particularly preferable to use polysulfone having high heat resistance. The thickness of the porous membrane may be arbitrarily selected.
（接着層）
　接着層２０は、ナノカーボン分離膜１０と多孔質膜３０とを接着する。接着層２０は、透水性を大きく阻害せず、ナノカーボン分離膜１０と多孔質膜３０とを接着できるものを用いることができる。 (Adhesive layer)
The adhesive layer 20 adheres the nanocarbon separation membrane 10 and the porous membrane 30. As the adhesive layer 20, a material capable of adhering the nanocarbon separation membrane 10 and the porous membrane 30 without significantly inhibiting water permeability can be used.
　接着層の材料は任意に選択できる。例えば、ポリビニルアルコール等を用いることができる。未架橋のポリビニルアルコールをナノカーボン分離膜１０と多孔質膜３０との間に設け、ポリビニルアルコールを架橋させることで、これらを接着できる。 ) The adhesive layer material can be selected arbitrarily. For example, polyvinyl alcohol or the like can be used. Uncrosslinked polyvinyl alcohol is provided between the nanocarbon separation membrane 10 and the porous membrane 30, and these can be bonded by crosslinking the polyvinyl alcohol.
　ナノカーボン複合分離膜１００の面内方向に対して、垂直な方向から通液するデッドエンドフローを行う場合は、ナノカーボン分離膜１０が多孔質膜３０から剥離することはほとんどない。これに対し、ナノカーボン複合分離膜１００の面内方向に対して、平行な方向から通液するクロスフローを行う場合は、ナノカーボン分離膜１０が多孔質膜３０から剥離しやすくなる。そのため、ナノカーボン複合分離膜１００に対してクロスフローで通液する場合は、特に接着層２０を設けることが好ましい。接着層の厚さは任意に選択してよい。 When performing a dead-end flow in which liquid is passed from a direction perpendicular to the in-plane direction of the nanocarbon composite separation membrane 100, the nanocarbon separation membrane 10 hardly peels from the porous membrane 30. On the other hand, when performing the cross flow which lets a liquid flow from a parallel direction with respect to the in-plane direction of the nanocarbon composite separation membrane 100, the nanocarbon separation membrane 10 becomes easy to peel from the porous membrane 30. Therefore, in the case where liquid is passed through the nanocarbon composite separation membrane 100 by crossflow, it is particularly preferable to provide the adhesive layer 20. The thickness of the adhesive layer may be arbitrarily selected.
　上述のように、本実施形態にかかるナノカーボン複合分離膜１００は、透水性及び分離対象物の分離特性の優れたナノカーボン分離膜１０を備える。このため、分離特性に優れる。 As described above, the nanocarbon composite separation membrane 100 according to the present embodiment includes the nanocarbon separation membrane 10 having excellent water permeability and separation characteristics of the separation object. For this reason, it has excellent separation characteristics.
　またナノカーボン分離膜１０の一面が多孔質膜３０で支持されることにより、ナノカーボン複合分離膜１００の機械強度を高めることができる。さらに、接着層２０でナノカーボン分離膜１０と多孔質膜３０とを接着することで、使用途中においてナノカーボン分離膜１０が剥離することが抑制される。 Further, the mechanical strength of the nanocarbon composite separation membrane 100 can be increased by supporting one surface of the nanocarbon separation membrane 10 with the porous membrane 30. Furthermore, by bonding the nanocarbon separation membrane 10 and the porous membrane 30 with the adhesive layer 20, it is possible to prevent the nanocarbon separation membrane 10 from being peeled off during use.
＜ナノカーボン複合分離膜＞
　図７は、本実施形態にかかるナノカーボン複合分離膜の製造方法を、模式的に示した図である。 <Nanocarbon composite separation membrane>
FIG. 7 is a view schematically showing a method for producing a nanocarbon composite separation membrane according to the present embodiment.
　図７の（ａ）～（ｄ）にこの順で示すように、本実施形態にかかるナノカーボン複合分離膜１００は、多孔質膜３０の一面に接着層２０を形成する工程と、接着層２０が形成された面にナノカーボン分離膜１０を形成する工程とを有する。 As shown in FIGS. 7A to 7D in this order, the nanocarbon composite separation membrane 100 according to this embodiment includes a step of forming the adhesive layer 20 on one surface of the porous membrane 30, and an adhesive layer 20. Forming a nanocarbon separation membrane 10 on the surface on which is formed.
　ナノカーボン分離膜１０は、酸化グラフェン片１とＤＷＣＮＴ２とが分散した分散液を、多孔質膜３０の接着層２０が形成された面に塗付、乾燥し、カーボン膜を形成する工程と、カーボン膜を二価のカチオンが溶解した溶液に浸漬する工程と、によって形成される。
　製造に使用される、前記酸化グラフェン片１の厚みは、任意に選択できるが、１～１．５ｎｍ程度であることが好ましい。
　製造に使用される、ＤＷＣＮＴ２の平均直径（外径）は、任意に選択してよい。またＤＷＣＮＴ２の最も内側の内径も任意に選択してよい。ＤＷＣＮＴ２の長さも任意に選択してよい。
　分散液において、酸化グラフェン片１及びＤＷＣＮＴ２の合計質量に対する、酸化グラフェン片１の質量比は任意に選択できるが、例えば、３０質量％以上７０質量％以下であることが好ましく、４０質量％以上７０質量％以下であることがより好ましく、５０質量％以上７０質量％以下であることが特に好ましい。また酸化グラフェン片及びダブルウォールカーボンナノチューブの合計質量に対するＤＷＣＮＴ２の質量比は、任意に選択できるが、３０質量％以上７０質量％以下であることが好ましく、３０質量％以上６０質量％以下であることがより好ましく、３０質量％以上５０質量％以下であることが特に好ましい。
　以下、図７を基に具体的に説明する。 The nanocarbon separation membrane 10 includes a step of applying a dispersion liquid in which graphene oxide pieces 1 and DWCNT2 are dispersed to the surface of the porous membrane 30 on which the adhesive layer 20 is formed, and drying to form a carbon membrane; Dipping the membrane in a solution in which divalent cations are dissolved.
The thickness of the graphene oxide piece 1 used for production can be arbitrarily selected, but is preferably about 1 to 1.5 nm.
You may select arbitrarily the average diameter (outer diameter) of DWCNT2 used for manufacture. Further, the innermost inner diameter of the DWCNT 2 may be arbitrarily selected. The length of DWCNT2 may be arbitrarily selected.
In the dispersion, the mass ratio of the graphene oxide piece 1 to the total mass of the graphene oxide piece 1 and the DWCNT 2 can be arbitrarily selected, but is preferably 30% by mass or more and 70% by mass or less, for example, 40% by mass or more and 70% More preferably, it is 50 mass% or less, and it is especially preferable that it is 50 to 70 mass%. The mass ratio of DWCNT2 to the total mass of graphene oxide pieces and double-walled carbon nanotubes can be arbitrarily selected, but is preferably 30% by mass to 70% by mass, and more preferably 30% by mass to 60% by mass. Is more preferable, and 30% by mass or more and 50% by mass or less is particularly preferable.
Hereinafter, a specific description will be given based on FIG.
　まず図７の（ａ）に示すように、多孔質膜３０を準備する。多孔質膜３０は、上述のものから選択して用いられる。 First, as shown in FIG. 7A, a porous film 30 is prepared. The porous membrane 30 is selected from the above-described ones.
　次いで、図７の（ｂ）に示すように、多孔質膜３０の一面に接着層２０を形成する。接着層２０は、塗布等の手段によって形成できる。例えばポリビニルアルコール水溶液に、多孔質膜３０を浸漬し、又は前記水溶液を前記膜に塗布し、乾燥させることで、多孔質膜３０の一面に接着層２０を形成できる。 Next, as shown in FIG. 7B, the adhesive layer 20 is formed on one surface of the porous film 30. The adhesive layer 20 can be formed by means such as coating. For example, the adhesive layer 20 can be formed on one surface of the porous film 30 by immersing the porous film 30 in an aqueous polyvinyl alcohol solution, or applying the aqueous solution to the film and drying it.
　次いで、図７の（ｃ）に示すように、接着層２０が形成された面に、酸化グラフェン片１とＤＷＣＮＴ２とが分散した分散液１１を塗布する。塗布の方法は特に問わない。公知の方法の中から任意に選択して使用してもよい。例えば、ノズルからスプレーコートをすると、ノズル先端で分散液１１にせん断力が加わり、酸化グラフェン片１及びＤＷＣＮＴ２の分散性が高まる。 Next, as shown in FIG. 7C, the dispersion 11 in which the graphene oxide pieces 1 and the DWCNTs 2 are dispersed is applied to the surface on which the adhesive layer 20 is formed. The application method is not particularly limited. You may use it arbitrarily selecting from well-known methods. For example, when spray coating is performed from the nozzle, a shearing force is applied to the dispersion 11 at the nozzle tip, and the dispersibility of the graphene oxide pieces 1 and the DWCNT 2 is increased.
　分散液１１は、例えば、酸化グラフェン片１が分散した第１分散液と、ＤＷＣＮＴ２が分散した第２分散液とを、混合して得られる。 The dispersion 11 is obtained, for example, by mixing a first dispersion in which the graphene oxide pieces 1 are dispersed and a second dispersion in which DWCNT2 is dispersed.
　第１分散液は、例えば、以下の手順で得られる。まず酸化グラフェン片１を準備する。酸化グラフェン片１は、グラファイトを原料として公知の方法（例えば、特許文献１や非特許文献４に記載の方法など）で得られる。酸化グラフェン片１は水への分散性が高い。このため、水に添加しただけで第１分散液が得られる。 The first dispersion is obtained by the following procedure, for example. First, the graphene oxide piece 1 is prepared. The graphene oxide piece 1 is obtained by a known method (for example, a method described in Patent Document 1 or Non-Patent Document 4) using graphite as a raw material. The graphene oxide piece 1 is highly dispersible in water. For this reason, a 1st dispersion liquid is obtained only by adding to water.
　次いで、第２分散液は、例えば、以下の手順で得られる。まずＤＷＣＮＴ２を作製する。ＤＷＣＮＴ２は、一般的な合成法により作製できる。例えば、アーク放電法、レーザー・アブレーション法、およびＣＶＤ（化学気相成長法）等の方法がある。ＣＶＤ法には、基板法と気相流動法がある。基板法は、厚さ数ｎｍから数μｍの金属層を蒸着した基板にカーボンナノチューブを合成する方法と、ゼオライトやセラミックなどの単体に遷移金属部粒子を担持させてカーボンナノチューブを合成する方法がある。気相流動法は、触媒微粒子と原料ガスとを反応管内の高温区域で反応させ、カーボンナノチューブを合成する方法である。触媒微粒子は、前駆体化合物を反応管に噴霧し、反応管入口で前駆体化合物を熱分解することにより得られる。触媒微粒子と原料ガスとは、キャリアガスによって反応管内に送り込まれる。具体的には、特許文献２や特許文献３などに記載の、ＤＷＣＮＴの製造方法が、例として挙げられる。 Next, the second dispersion is obtained by the following procedure, for example. First, DWCNT2 is produced. DWCNT2 can be produced by a general synthesis method. For example, there are methods such as arc discharge, laser ablation, and CVD (chemical vapor deposition). CVD methods include a substrate method and a gas phase flow method. The substrate method includes a method of synthesizing carbon nanotubes on a substrate on which a metal layer having a thickness of several nanometers to several μm is deposited, and a method of synthesizing carbon nanotubes by supporting transition metal part particles on a simple substance such as zeolite or ceramic. . The gas phase flow method is a method of synthesizing carbon nanotubes by reacting catalyst fine particles and a raw material gas in a high temperature zone in a reaction tube. The catalyst fine particles are obtained by spraying the precursor compound onto the reaction tube and thermally decomposing the precursor compound at the reaction tube inlet. The catalyst fine particles and the raw material gas are sent into the reaction tube by the carrier gas. Specifically, a method for producing DWCNT described in Patent Document 2, Patent Document 3, and the like is given as an example.
　こうして作製されたＤＷＣＮＴ２を、必要に応じて選択される水溶液中に添加して第２分散液を得る。水溶液は、例えば、ポリスチレンスルホン酸ナトリウム（ＰＳＳ）水溶液、ドデシル硫酸ナトリウム水溶液、及びデオキシコール酸ナトリウム水溶液等を用いることができる。
　次に、第１分散液と第２分散液とを混合し、必要であれば希釈し、分散液１１を得る。 The DWCNT 2 thus produced is added to an aqueous solution selected as necessary to obtain a second dispersion. As the aqueous solution, for example, a sodium polystyrene sulfonate (PSS) aqueous solution, a sodium dodecyl sulfate aqueous solution, a sodium deoxycholate aqueous solution, or the like can be used.
Next, the first dispersion and the second dispersion are mixed and diluted if necessary to obtain the dispersion 11.
　塗布後の分散液１１を、乾燥して、例えば自然乾燥して、カーボン膜が得られる。カーボン膜は、多孔質膜３０と共に加熱することが好ましい。接着層が熱により架橋するものである場合、接着層としてポリビニルアルコールを用いた場合には、加熱により、接着層２０のポリビニルアルコールが架橋し、カーボン膜と多孔質膜３０の接着性が高まり、耐水性も発現する。また余計な水分等も除去できる。 The coated dispersion 11 is dried, for example, naturally dried to obtain a carbon film. The carbon film is preferably heated together with the porous film 30. When the adhesive layer is cross-linked by heat, when polyvinyl alcohol is used as the adhesive layer, the polyvinyl alcohol of the adhesive layer 20 is cross-linked by heating, and the adhesion between the carbon film and the porous film 30 is increased. Also exhibits water resistance. Also, excess water can be removed.
　最後に、分散液１１の塗布により形成されたカーボン膜を、二価のカチオンが溶解した溶液に浸漬する。例えば、二価のカチオンとしてカルシウムイオンを用いる場合は、塩化カルシウムが溶解した溶液に浸漬する。カチオンが溶解した溶液に浸漬することで、酸化グラフェン片１同士がカチオンを介して架橋する。溶液の溶媒は任意に選択してよい。二価のカチオンは任意に選択できるが、カルシウムイオン、マグネシウムイオンなどが挙げられる。 Finally, the carbon film formed by applying the dispersion 11 is immersed in a solution in which divalent cations are dissolved. For example, when calcium ions are used as divalent cations, they are immersed in a solution in which calcium chloride is dissolved. By immersing in the solution in which the cation is dissolved, the graphene oxide pieces 1 are cross-linked via the cation. The solvent of the solution may be arbitrarily selected. The divalent cation can be arbitrarily selected, and examples thereof include calcium ions and magnesium ions.
　上述のように、本実施形態にかかるナノカーボン分離膜の製造方法によれば、容易に所定のナノカーボン分離膜が得られる。またこのナノカーボン分離膜の製造方法を利用することで、容易にナノカーボン複合分離膜が得られる。 As described above, according to the method for producing a nanocarbon separation membrane according to this embodiment, a predetermined nanocarbon separation membrane can be easily obtained. Moreover, a nanocarbon composite separation membrane can be easily obtained by using this method for producing a nanocarbon separation membrane.
　また本実施形態にかかるナノカーボン分離膜の製造方法によれば、酸化グラフェン片１が分散した第１分散液と、ＤＷＣＮＴ２が分散した第２分散液を混合するだけで、ナノカーボン分離膜の流体が流れる流路を制御できる。すなわち、ナノカーボン分離膜の透水性及び分離性能を容易に制御できる。 In addition, according to the method for producing a nanocarbon separation membrane according to the present embodiment, the fluid of the nanocarbon separation membrane can be obtained simply by mixing the first dispersion in which the graphene oxide pieces 1 are dispersed and the second dispersion in which the DWCNT2 is dispersed. It is possible to control the flow path through which the gas flows. That is, the water permeability and separation performance of the nanocarbon separation membrane can be easily controlled.
　また本実施形態にかかるナノカーボン分離膜の製造方法によれば、ナノカーボン分離膜を分散液の塗布により作製することができる。そのため、ナノカーボン分離膜の大面積化が容易になる。 Moreover, according to the method for producing a nanocarbon separation membrane according to the present embodiment, the nanocarbon separation membrane can be produced by applying a dispersion liquid. Therefore, it is easy to increase the area of the nanocarbon separation membrane.
　以上、ナノカーボン分離膜、ナノカーボン複合分離膜及びナノカーボン分離膜の製造方法について説明した。本発明は、発明の要旨を変えない範囲で種々の変更をしてもよい。 The nanocarbon separation membrane, the nanocarbon composite separation membrane, and the method for producing the nanocarbon separation membrane have been described above. The present invention may be variously modified without changing the gist of the invention.
　以下、本発明を実施例によりさらに詳細に説明するが、本発明はこれら実施例により何ら制限されるものではない。 Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples.
（実施例１）
　実施例１として、３０質量％の酸化グラフェン片と７０質量％のＤＷＣＮＴとからなるナノカーボン分離膜を有するナノカーボン複合分離膜を作製した。具体的には、以下の手順で実施例１のナノカーボン複合分離膜を作製した。 Example 1
As Example 1, a nanocarbon composite separation membrane having a nanocarbon separation membrane composed of 30% by mass of graphene oxide pieces and 70% by mass of DWCNT was prepared. Specifically, the nanocarbon composite separation membrane of Example 1 was produced by the following procedure.
　まずグラファイト（Ｓｉｇｍａ－Ａｌｄｒｉｃｈ社製　製品番号３３２４６１）を原料として、平均径１２μｍの酸化グラフェン片が分散した第１分散液を作製した。第１分散液は、以下のようにして作製した。 First, a first dispersion in which graphene oxide pieces having an average diameter of 12 μm were dispersed was prepared using graphite (product number 332461 manufactured by Sigma-Aldrich) as a raw material. The first dispersion was prepared as follows.
　まず９５質量％のＨ２ＳＯ４水溶液２００ｍＬと、８５質量％のＨ３ＰＯ４水溶液４０ｍＬと、を混合し、さらに５ｇのグラファイトを添加し、マグネチックスターラで混合した。次いで、混合液にＫＭｎＯ４を２５ｇゆっくり添加した。この際、液の色は黒から緑に変化した。そしてこの液を５分かけて４０℃に昇温し、４０℃で１時間保持した。１時間後には、グラファイトが剥離して、液がペースト状になった。得られたペーストを、テフロン（登録商標）棒を用いて４０℃で２．５時間さらに混合した。その後、混合後のペーストを常温まで降温した。 First, 200 mL of 95% by mass H 2 SO 4 aqueous solution and 40 mL of 85% by mass H 3 PO 4 aqueous solution were mixed, and further 5 g of graphite was added and mixed with a magnetic stirrer. Next, 25 g of KMnO 4 was slowly added to the mixture. At this time, the color of the liquid changed from black to green. And this liquid was heated up to 40 degreeC over 5 minutes, and was hold | maintained at 40 degreeC for 1 hour. After 1 hour, the graphite peeled off and the liquid became a paste. The resulting paste was further mixed for 2.5 hours at 40 ° C. using a Teflon rod. Thereafter, the paste after mixing was cooled to room temperature.
　次いで、このペーストに、３５％のＨ２Ｏ２水溶液４０ｍＬと５℃以下の冷水６００ｍＬとの混合液を、ゆっくり注いだ。混合液を注ぐと、ペーストは発熱し、泡が発生した。
そして、得られた混合液を１晩以上静置した。 Next, a mixed solution of 40 mL of 35% aqueous H 2 O 2 solution and 600 mL of cold water at 5 ° C. or lower was slowly poured into this paste. When the mixture was poured, the paste generated heat and foam was generated.
And the obtained liquid mixture was left still for 1 night or more.
　静置した液は、上澄み液と沈殿物に分離した。上澄み液をデカンテーションにより除去し、沈殿物を得た。得られた沈殿物は、５質量％のＨ２ＳＯ４水溶液（１Ｌ）に添加し、分散させた。 The liquid that was allowed to stand was separated into a supernatant and a precipitate. The supernatant was removed by decantation to obtain a precipitate. The obtained precipitate was added to a 5% by mass H 2 SO 4 aqueous solution (1 L) and dispersed.
　そして、分散液を純水中に添加し、遠心分離し、その後純水へ分散する操作を５回繰り返し、分散媒の清浄を行った。この過程で、遠心分離後の沈殿物は２層になる。下の層は互いに剥離していないグラファイトであり、上の層は剥離した酸化グラフェン片が水を吸ったものであった。下の層を除去することで、固形分濃度が０．９質量％の第１分散液を得た。得られた第１分散液を水で希釈し、Ｓｉ基板上に滴下、乾燥した試料をＳＥＭ観察したところ、酸化グラフェン片の平均径は１２μｍだった。 Then, the operation of adding the dispersion into pure water, centrifuging, and then dispersing in pure water was repeated 5 times to clean the dispersion medium. In this process, the precipitate after centrifugation becomes two layers. The lower layer was graphite that was not exfoliated from each other, and the upper layer was that the exfoliated graphene oxide pieces absorbed water. By removing the lower layer, a first dispersion having a solid content concentration of 0.9% by mass was obtained. When the obtained first dispersion was diluted with water and dropped onto the Si substrate and dried, the sample was observed by SEM. As a result, the average diameter of the graphene oxide pieces was 12 μm.
　次いで、第２分散液を用意した。０．５質量％のデオキシコール酸ナトリウム水溶液にＤＷＣＮＴ（ＴＥＭ観察で、外径１．８ｎｍ、内径１．２ｎｍ）を分散し、第２分散液を作製した。第２分散液中におけるＤＷＣＮＴの直径は、数ｎｍ程度であった。 Next, a second dispersion was prepared. DWCNT (outer diameter 1.8 nm, inner diameter 1.2 nm by TEM observation) was dispersed in a 0.5 mass% sodium deoxycholate aqueous solution to prepare a second dispersion. The diameter of DWCNT in the second dispersion was about several nm.
　そして得られた第１分散液と第２分散液を混合、希釈して、分散液を得た。分散液中には、酸化グラフェン片とＤＷＣＮＴとからなるナノカーボンが分散している。分散液中のナノカーボンの構成比率は、酸化グラフェン片が３０質量％で、ＤＷＣＮＴが７０質量％であった。溶媒に対するナノカーボンの濃度は、０．８ｍｇ／ｍＬとした。 Then, the obtained first dispersion and second dispersion were mixed and diluted to obtain a dispersion. In the dispersion, nanocarbon composed of graphene oxide pieces and DWCNT is dispersed. The composition ratio of the nanocarbon in the dispersion was 30% by mass for graphene oxide pieces and 70% by mass for DWCNT. The concentration of nanocarbon relative to the solvent was 0.8 mg / mL.
　また多孔質膜として、市販のポリサルフォン膜（Ａｌｆａ　Ｌａｖｅｌ社製：ＧＲ４０ＰＰ、大きさ５０ｍｍ×５０ｍｍ）を準備した。そして、ポリサルフォン膜を１質量％のポリビニルアルコール水溶液（Ｓｉｇｍａ－Ａｌｄｒｉｃｈ社製：分子量３１，０００－５０，０００、９８～９９％ケン化品）に１時間浸漬した。浸漬後のポリサルフォン膜を、起立させた状態で風乾させた。その結果、ポリサルフォン膜の表面にポリビニルアルコールが被覆された。 Also, a commercially available polysulfone membrane (Alfa Label: GR40PP, size 50 mm × 50 mm) was prepared as a porous membrane. Then, the polysulfone film was immersed in a 1% by mass aqueous polyvinyl alcohol solution (manufactured by Sigma-Aldrich: molecular weight 31,000-50,000, 98-99% saponified product) for 1 hour. The polysulfone membrane after immersion was air-dried in an upright state. As a result, polyvinyl alcohol was coated on the surface of the polysulfone film.
　次いで、ポリビニルアルコールで被覆された多孔質膜に対して、エアーブラシ（アネストイワタ製：ＨＰ－ＢＣＳ）を用いて、前記分散液をスプレーした。その後、前記多孔質膜を１００℃の大気雰囲気下で１時間乾燥させた。この際、ポリビニルアルコールは架橋し、多孔質膜と、分散液が乾燥してなるカーボン膜と、が接着した。 Next, the dispersion was sprayed onto the porous film coated with polyvinyl alcohol using an air brush (manufactured by Anest Iwata: HP-BCS). Thereafter, the porous film was dried in an air atmosphere at 100 ° C. for 1 hour. At this time, the polyvinyl alcohol was cross-linked, and the porous film and the carbon film formed by drying the dispersion were adhered.
　最後に、得られた積層膜を、塩化カルシウム溶液に１時間浸漬した。塩化カルシウム溶液は、塩化カルシウムの濃度が５質量％であり、塩化カルシウム溶液の溶媒は、容積比で１：３の比率でエタノールと水が混合したものとした。そして、浸漬後の積層膜を乾燥させた。乾燥は、まず風乾した後、一度エタノールに一時間浸漬し、再度風乾した。 Finally, the obtained laminated film was immersed in a calcium chloride solution for 1 hour. The calcium chloride solution had a calcium chloride concentration of 5% by mass, and the solvent of the calcium chloride solution was a mixture of ethanol and water in a volume ratio of 1: 3. And the laminated film after immersion was dried. The drying was performed by air-drying, then immersed in ethanol for 1 hour and then air-dried again.
（実施例２及び３）
　実施例２及び３は、第１分散液と第２分散液の混合比率を変更した点以外は、実施例１と同様の手順でナノカーボン複合分離膜を作製した。
　得られたナノカーボン分離膜の構成比率は以下である。
　実施例２：酸化グラフェン片（５０質量％）、ＤＷＣＮＴ（５０質量％）
　実施例３：酸化グラフェン片（７０質量％）、ＤＷＣＮＴ（３０質量％） (Examples 2 and 3)
In Examples 2 and 3, nanocarbon composite separation membranes were prepared in the same procedure as in Example 1 except that the mixing ratio of the first dispersion and the second dispersion was changed.
The composition ratio of the obtained nanocarbon separation membrane is as follows.
Example 2: Graphene oxide pieces (50 mass%), DWCNT (50 mass%)
Example 3: Graphene oxide pieces (70 mass%), DWCNT (30 mass%)
（比較例１）
　比較例１は、第１分散液と第２分散液の混合比率を変更した点以外は、実施例１と同様の手順でナノカーボン複合分離膜を作製した。
　比較例１のナノカーボン分離膜の構成比率は、酸化グラフェン片を９０質量％、ＤＷＣＮＴを１０質量％とした。 (Comparative Example 1)
In Comparative Example 1, a nanocarbon composite separation membrane was prepared in the same procedure as in Example 1 except that the mixing ratio of the first dispersion and the second dispersion was changed.
The composition ratio of the nanocarbon separation membrane of Comparative Example 1 was 90% by mass of graphene oxide pieces and 10% by mass of DWCNT.
（比較例２）
　比較例２は、分散液を第１分散液のみとして、第２分散液を用いなかった点以外は、実施例１と同様の手順でナノカーボン複合分離膜を作製した。
　すなわち、比較例２のナノカーボン分離膜の構成比率は、酸化グラフェン片を１００質量％とした。 (Comparative Example 2)
In Comparative Example 2, a nanocarbon composite separation membrane was prepared in the same procedure as in Example 1 except that only the first dispersion was used and the second dispersion was not used.
That is, the composition ratio of the nanocarbon separation membrane of Comparative Example 2 was 100% by mass of graphene oxide pieces.
（比較例３）
　比較例３は、分散液を第２分散液のみとして、第１分散液を用いなかった点以外は、実施例１と同様の手順でナノカーボン複合分離膜を作製した。
　すなわち、比較例３のナノカーボン分離膜の構成比率は、ＤＷＣＮＴを１００質量％とした。 (Comparative Example 3)
In Comparative Example 3, a nanocarbon composite separation membrane was prepared in the same procedure as in Example 1 except that only the second dispersion liquid was used and the first dispersion liquid was not used.
That is, the composition ratio of the nanocarbon separation membrane of Comparative Example 3 was set to 100% by mass of DWCNT.
＜ナノカーボン複合分離膜の評価＞
　実施例１～３及び比較例１～３のナノカーボン複合分離膜の透水量及びＮａＣｌ除去率を測定した。具体的には、前記膜に、クロスフローで、０．２％濃度の塩化ナトリウム水溶液を３００ｍＬ／分で送液し、ナノカーボン複合分離膜の透水量及びＮａＣｌ除去率を測定した。 <Evaluation of nanocarbon composite separation membrane>
The water permeability and NaCl removal rate of the nanocarbon composite separation membranes of Examples 1 to 3 and Comparative Examples 1 to 3 were measured. Specifically, a 0.2% concentration sodium chloride aqueous solution was fed to the membrane at 300 mL / min by crossflow, and the water permeability and NaCl removal rate of the nanocarbon composite separation membrane were measured.
　透水量は、圧力５．０ＭＰａでの透水性測定の結果から算出した。
　ＮａＣｌ除去率は、膜を直径２５ｍｍの円形に切り抜いて、クロスフロー濾過器（トスク社製）を用いて求めた。
　ＮａＣｌ除去率［％］＝｛１－透過水のＮａＣｌ濃度［質量％］／原水のＮａＣｌ濃度［質量％］｝×１００ The water permeability was calculated from the results of water permeability measurement at a pressure of 5.0 MPa.
The NaCl removal rate was obtained by cutting out the membrane into a circle having a diameter of 25 mm and using a cross flow filter (manufactured by Tosk Corporation).
NaCl removal rate [%] = {1-NaCl concentration of permeated water [mass%] / NaCl concentration of raw water [mass%]} × 100
　測定結果を表１に示す。表１において、ＧＯは酸化グラフェン片を示し、ＤＷＣＮＴはダブルウォールカーボンナノチューブを示し、ＰＶＡはポリビニルアルコールを示す。 Table 1 shows the measurement results. In Table 1, GO indicates graphene oxide pieces, DWCNT indicates double wall carbon nanotubes, and PVA indicates polyvinyl alcohol.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　上述のように、酸化グラフェン片とＤＷＣＮＴの比率が所定の範囲にある実施例１～３のナノカーボン複合分離膜は、比較例１及び比較例２のナノカーボン複合分離膜と比較して、透水量が大きく向上した。またＮａＣｌ除去率は多少低下したが、用途によっては、４０％程度あれば十分であり、充分なＮａＣｌ除去率を示した。用途としては、例えば、２価イオン除去用、有機物分離用のナノフィルトレーション膜等がある。なお、ＤＷＣＮＴのみからなる比較例３は、水が自由に流れ、脱塩性能は確認されなかった。 As described above, the nanocarbon composite separation membranes of Examples 1 to 3 in which the ratio of the graphene oxide pieces to DWCNT is in a predetermined range are more permeable than the nanocarbon composite separation membranes of Comparative Examples 1 and 2. The amount was greatly improved. Further, although the NaCl removal rate slightly decreased, depending on the application, about 40% was sufficient, and a sufficient NaCl removal rate was exhibited. Applications include, for example, nanofiltration membranes for divalent ion removal and organic matter separation. In Comparative Example 3 consisting only of DWCNT, water freely flowed and no desalting performance was confirmed.
＜酸化グラフェン同士の架橋＞
　酸化グラフェン同士が二価のカチオンによって架橋していることを確認する検討を行った。
　検討は、フーリエ変換赤外分光（ＦＴＩＲ）測定、ラマン分光測定、Ｘ線光電子分光（ＸＰＳ）測定によって行った。 <Bridge between graphene oxides>
A study was conducted to confirm that graphene oxide was crosslinked by divalent cations.
The examination was performed by Fourier transform infrared spectroscopy (FTIR) measurement, Raman spectroscopy measurement, and X-ray photoelectron spectroscopy (XPS) measurement.
　測定は、酸化グラフェン片のみからなる参考比較例２と、参考比較例２の試料を塩化カルシウム溶液に浸漬する前でとめた試料（以下、参考比較例２－１と言う：塩化カルシウム溶液への浸漬なし）と、参考比較例２の試料を塩化カルシウム溶液に浸漬する前にとめてこの試料を１００℃で加熱した試料（以下、参考比較例２－２と言う：塩化カルシウム溶液への浸漬なし）と、の３つの試料に対して行った。 The measurement was performed by immersing the sample of Reference Comparative Example 2 consisting only of graphene oxide pieces and the sample of Reference Comparative Example 2 in the calcium chloride solution (hereinafter referred to as Reference Comparative Example 2-1: The sample of Reference Comparative Example 2 was immersed before being immersed in the calcium chloride solution, and the sample was heated at 100 ° C. (hereinafter referred to as Reference Comparative Example 2-2: No immersion in the calcium chloride solution) ) And three samples.
　なお、参考比較例２では、比較例２で用いた分散液を多孔質膜の代わりにＳｉ基板上に塗布し、塩化カルシウム溶液への浸漬も含む同様の手順を行い、Ｓｉ基板上にナノカーボン分離膜を形成した。以下、Ｓｉ基板上に形成したものを参考比較例等と表記する。参考比較例２は、比較例２と同様の条件で作製されたものに対応し、その他の参考実施例及び参考比較例も同様の対応関係を意味する。 In Reference Comparative Example 2, the dispersion used in Comparative Example 2 was applied on a Si substrate instead of the porous film, and the same procedure including immersion in a calcium chloride solution was performed. A separation membrane was formed. Hereinafter, what was formed on the Si substrate will be referred to as a reference comparative example. Reference Comparative Example 2 corresponds to one produced under the same conditions as Comparative Example 2, and the other reference examples and reference comparative examples also have the same correspondence.
　図８は、参考比較例２、２－１，２－２のＦＴＩＲ測定の結果を示す。ＦＴＩＲは、全反射測定（ＡＴＲ）法により行った。ＦＴＩＲ測定の観測ピークは、C-O (alkoxy/alkoxide,1042cm-1)、C-O(carboxy,1410cm-1)、C=C (aromatic,1620cm-1)、C=O (carboxy/carbonyl,1716cm-1)、OH(3300cm-1)に帰属される。 FIG. 8 shows the results of FTIR measurement of Reference Comparative Examples 2, 2-1, and 2-2. FTIR was performed by the total reflection measurement (ATR) method. The observed peaks of FTIR measurement are: CO (alkoxy / alkoxide, 1042 cm -1 ), CO (carboxy, 1410 cm -1 ), C = C (aromatic, 1620 cm -1 ), C = O (carboxy / carbonyl, 1716 cm -1 ) , OH (3300 cm −1 ).
　Ｃ＝Ｃピークを基準として相対比較すると、ＣａＣｌ２処理を行った参考比較例２は、処理を行う前の参考比較例２－１と比較して、Ｃ－ＯとＣ＝Ｏピークの強度が下がっている。これはＣａ２＋イオンが酸素イオンに対して配位することで、Ｃ＝Ｃピークを基準とするＣ－ＯとＣ＝Ｏピークの相対強度が低下したためである。 When the relative comparison is made with the C = C peak as a reference, the comparative example 2 in which the CaCl 2 treatment was performed has the intensity of the C—O and C═O peaks compared to the reference comparative example 2-1 before the treatment. It's down. This is because the relative intensity of C—O and C═O peak with respect to the C═C peak is reduced by coordination of Ca 2+ ions with oxygen ions.
　図９は、参考比較例２、２－１，２－２のラマン分光測定の結果を示す。
　ラマン分光測定の結果におけるＤ（１３５０ｃｍ－１）／Ｇ（１６００ｃｍ－１）比は、参考比較例２－１が０．９２、参考比較例２－２が０．８４、参考比較例２が０．８７であった。 FIG. 9 shows the results of Raman spectroscopic measurement in Reference Comparative Examples 2, 2-1, and 2-2.
The D (1350 cm −1 ) / G (1600 cm −1 ) ratio in the result of Raman spectroscopic measurement was 0.92 in Reference Comparative Example 2-1, 0.84 in Reference Comparative Example 2-2, and 0 in Reference Comparative Example 2. .87.
　参考比較例２－１と参考比較例２－２とを比較すると、参考比較例２－２のＤ／Ｇ比が小さくなっている。
Ｇバンドはグラファイト構造に由来のピークであり、Ｄバンドは欠陥由来のピークである。そのため、Ｄ／Ｇ比が小さくなったことは、結晶性が高まったことを意味する。参考比較例２－２は、参考比較例２－１を１００℃で加熱したものであり、加熱により酸化グラフェンの一部が還元され、グラファイト構造に近づいたためと考えられる。 When the reference comparative example 2-1 and the reference comparative example 2-2 are compared, the D / G ratio of the reference comparative example 2-2 is small.
The G band is a peak derived from the graphite structure, and the D band is a defect derived peak. Therefore, a decrease in the D / G ratio means an increase in crystallinity. Reference Comparative Example 2-2 is obtained by heating Reference Comparative Example 2-1 at 100 ° C., and it is considered that a part of the graphene oxide was reduced by heating and approached the graphite structure.
　一方で、参考比較例２－２と参考比較例２とを比較すると、参考比較例２のＤ／Ｇ比が大きくなっている。カルシウムイオンが配位することで、結晶配列に乱れが生じたためと考えられる。 On the other hand, when the reference comparative example 2-2 is compared with the reference comparative example 2, the D / G ratio of the reference comparative example 2 is large. It is considered that the disorder of the crystal arrangement was caused by the coordination of calcium ions.
　図１０Ａ～１０Ｃは、参考比較例２、２－１，及び２－２のＸＰＳ測定により求められたＣ１ｓスペクトルのそれぞれの分析結果を示す。図１０Ａは参考比較例２－１の分析結果であり、図１０Ｂは参考比較例２－２の分析結果であり、図１０Ｃは参考比較例２の分析結果である。 10A to 10C show analysis results of C1s spectra obtained by XPS measurement in Reference Comparative Examples 2, 2-1, and 2-2. 10A shows the analysis result of Reference Comparative Example 2-1, FIG. 10B shows the analysis result of Reference Comparative Example 2-2, and FIG. 10C shows the analysis result of Reference Comparative Example 2.
　図１０Ａと図１０Ｂを比較すると、Ｃ＝Ｃピークを基準としてＣ－Ｏ及びＣＯＯのピーク比が小さくなっている。加熱により酸化グラフェンの一部が還元され、酸素元素が抜けたためと考えられる。 When comparing FIG. 10A and FIG. 10B, the peak ratio of CO and COO is small with the C = C peak as a reference. This is probably because part of the graphene oxide was reduced by heating, and oxygen element was released.
　また図１０Ｂと図１０Ｃを比較すると、Ｃ＝Ｃピークを基準としてＣ－Ｏ及びＣＯＯのピーク比が小さくなっている。これは、酸素元素に対してカルシウムイオンが配位することで、Ｃ－Ｏ及びＣＯＯピークの検出量が低下したためと考えられる。 Also, comparing FIG. 10B and FIG. 10C, the peak ratio of CO and COO is smaller with the C = C peak as a reference. This is presumably because the detected amount of CO and COO peaks decreased due to the coordination of calcium ions to the oxygen element.
　また図１１Ａと図１１Ｂは、参考比較例２のＸＰＳ測定により求められたＣｌ２ｐスペクトル及びＣａ２ｐスペクトルの分析結果を示す。図１１ＡはＣｌ２ｐスペクトルの分析結果であり、図１１ＢはＣａ２ｐスペクトルの分析結果である。 11A and 11B show the analysis results of the Cl2p spectrum and Ca2p spectrum obtained by XPS measurement in Reference Comparative Example 2. FIG. 11A shows the analysis result of the Cl2p spectrum, and FIG. 11B shows the analysis result of the Ca2p spectrum.
　図１１Ａに示すように、参考比較例２はＣａのピークは検出されたが、Ｃｌのピークは検出されなかった。すなわち、参考比較例２には、ＣａＣｌ２が残存しているのではなく、Ｃａとして取り込まれていることが分かる。 As shown in FIG. 11A, in Reference Comparative Example 2, a Ca peak was detected, but a Cl peak was not detected. That is, it can be seen that in Reference Comparative Example 2, CaCl 2 is not remaining, but is taken in as Ca.
　上記の実験結果から、カルシウムイオンは酸素に配位し、酸化グラフェン同士を架橋していると言える。 From the above experimental results, it can be said that calcium ions are coordinated to oxygen and cross-linked graphene oxides.
＜接着層の有無の検討＞
　実施例１のナノカーボン複合分離膜と、実施例１から接着層を除いたナノカーボン複合分離膜（以下、実施例４という）とを準備した。実施例４は、実施例１の作製工程において、ポリサルフォン膜をポリビニルアルコール水溶液に浸漬していない点が異なる。 <Examination of presence or absence of adhesive layer>
A nanocarbon composite separation membrane of Example 1 and a nanocarbon composite separation membrane obtained by removing the adhesive layer from Example 1 (hereinafter referred to as Example 4) were prepared. Example 4 differs from Example 1 in that the polysulfone film is not immersed in an aqueous polyvinyl alcohol solution in the production process of Example 1.
　実施例１と実施例４のカーボンナノ複合分離膜に対して、クロスフローで２～５ＭＰａの圧力で０．２％濃度の塩化ナトリウム水溶液を流速３００ｍｌ／分で送液した。 A 0.2% concentration sodium chloride aqueous solution was fed to the carbon nanocomposite separation membranes of Example 1 and Example 4 at a flow rate of 300 ml / min at a pressure of 2 to 5 MPa by cross flow.
　図１２Ａと図１２Ｂは、実施例１及び実施例４の処理後のカーボンナノ複合分離膜の表面の写真である。図１２Ａは、塩化ナトリウム水溶液を供給開始してから２３時間後の、実施例４のカーボンナノ複合分離膜の表面写真である。図１２Ｂは、塩化ナトリウム水溶液を供給開始してから７０時間後の、実施例１のカーボンナノ複合分離膜の表面写真である。 12A and 12B are photographs of the surface of the carbon nanocomposite separation membrane after the treatment in Example 1 and Example 4. FIG. FIG. 12A is a photograph of the surface of the carbon nanocomposite separation membrane of Example 4 23 hours after the start of supplying the sodium chloride aqueous solution. FIG. 12B is a surface photograph of the carbon nanocomposite separation membrane of Example 1 after 70 hours from the start of supply of the sodium chloride aqueous solution.
　実施例４のカーボンナノ複合分離膜は、供給する液の流れによりカーボンナノ分離膜が剥がれている（図１２Ａの矢印で図示している部分）。これに対して、図１２Ｂに示すように、実施例１のカーボンナノ複合分離膜は、剥がれ等が生じなかった。 In the carbon nanocomposite separation membrane of Example 4, the carbon nanoseparation membrane is peeled off by the flow of the supplied liquid (portion shown by the arrow in FIG. 12A). In contrast, as shown in FIG. 12B, the carbon nanocomposite separation membrane of Example 1 did not peel off.
　すなわち、接着層を設けることで、カーボンナノ分離膜がカーボンナノ複合分離膜から剥離することを抑制できる。特に、カーボンナノ複合分離膜に対して、クロスフローで液を供給する場合は、接着層を設けることが好ましい。これに対し、デッドエンドフローで液や気体を供給する場合は、接着層が無くても使用することはできる。 That is, by providing the adhesive layer, it is possible to suppress the separation of the carbon nanoseparation membrane from the carbon nanocomposite separation membrane. In particular, when the liquid is supplied to the carbon nanocomposite separation membrane by crossflow, it is preferable to provide an adhesive layer. On the other hand, when a liquid or gas is supplied in a dead end flow, it can be used without an adhesive layer.
＜接着層の硬化の確認＞
　図１３は、ポリビニルアルコールの加熱前後のＦＴＩＲ測定を行った結果を示す。
　図１３に示すように、８５４ｃｍ－１ピークで規格化したときに、１１４１ｃｍ－１のピークが大きくなった。これは、ポリビニルアルコール膜の熱による硬化を示す。
　すなわち、ポリビニルアルコール膜は、１００度雰囲気下で１時間乾燥させれば充分架橋する。 <Confirmation of curing of adhesive layer>
FIG. 13 shows the results of FTIR measurement before and after heating polyvinyl alcohol.
As shown in FIG. 13, when normalized by the 854 cm −1 peak, the peak at 1141 cm −1 increased. This indicates the curing of the polyvinyl alcohol film by heat.
That is, the polyvinyl alcohol film is sufficiently crosslinked when it is dried for 1 hour in an atmosphere of 100 degrees.
　透水性と分離性能とが共に優れたナノカーボン分離膜を提供することを目的とする。 An object of the present invention is to provide a nanocarbon separation membrane excellent in both water permeability and separation performance.
１　酸化グラフェン片、
２　ダブルウォールカーボンナノチューブ（ＤＷＣＮＴ）、
１０　ナノカーボン分離膜、
１１　分散液
２０　接着層、
３０　多孔質膜、
３１　孔部、
１００　ナノカーボン複合分離膜 1 Graphene oxide pieces,
2 Double wall carbon nanotube (DWCNT),
10 Nanocarbon separation membrane,
11 Dispersion 20 Adhesive layer,
30 porous membrane,
31 holes,
100 Nanocarbon composite separation membrane

Claims (7)

  1. 　厚み方向からみて互いに重なり合うように存在し、二価のカチオンによって互いに架橋された複数の酸化グラフェン片と、
    　前記複数の酸化グラフェン片の層間に挿入されたダブルウォールカーボンナノチューブと、を備え、
    　酸化グラフェン片及びダブルウォールカーボンナノチューブの合計質量に対する、酸化グラフェン片の質量比が０質量％より大きく７０質量％以下であり、ダブルウォールカーボンナノチューブの質量比が３０質量％以上１００質量％未満である、ナノカーボン分離膜。     A plurality of graphene oxide pieces that exist so as to overlap each other when viewed from the thickness direction and are cross-linked with each other by a divalent cation;
    A double wall carbon nanotube inserted between layers of the plurality of graphene oxide pieces,
    The mass ratio of the graphene oxide piece to the total mass of the graphene oxide piece and the double wall carbon nanotube is greater than 0% by mass and 70% by mass or less, and the mass ratio of the double wall carbon nanotube is 30% by mass or more and less than 100% by mass. Nanocarbon separation membrane.
  2. 　酸化グラフェン片及びダブルウォールカーボンナノチューブとの合計質量に対する酸化グラフェン片の質量比が３０質量％以上７０質量％以下であり、ダブルウォールカーボンナノチューブの質量比が３０質量％以上７０質量％以下である請求項１に記載のナノカーボン分離膜。 The mass ratio of the graphene oxide piece to the total mass of the graphene oxide piece and the double wall carbon nanotube is 30% by mass to 70% by mass, and the mass ratio of the double wall carbon nanotube is 30% by mass to 70% by mass. Item 2. The nanocarbon separation membrane according to Item 1.
  3. 　前記二価のカチオンが、カルシウムイオンである請求項１または２のいずれかに記載のナノカーボン分離膜。 The nanocarbon separation membrane according to claim 1 or 2, wherein the divalent cation is calcium ion.
  4. 　請求項１～３のいずれか一項に記載のナノカーボン分離膜と、
    　前記ナノカーボン分離膜の一面側に配設され、前記ナノカーボン分離膜を支持する多孔質膜と、を有するナノカーボン複合分離膜。     The nanocarbon separation membrane according to any one of claims 1 to 3,
    A nanocarbon composite separation membrane having a porous membrane disposed on one side of the nanocarbon separation membrane and supporting the nanocarbon separation membrane.
  5. 　前記ナノカーボン分離膜と前記多孔質膜とが、接着されている請求項４に記載のナノカーボン複合分離膜。 The nanocarbon composite separation membrane according to claim 4, wherein the nanocarbon separation membrane and the porous membrane are adhered to each other.
  6. 　前記ナノカーボン分離膜と前記多孔質膜とが、ポリビニルアルコールによって接着されている請求項５に記載のナノカーボン複合分離膜。 The nanocarbon composite separation membrane according to claim 5, wherein the nanocarbon separation membrane and the porous membrane are bonded together with polyvinyl alcohol.
  7. 　酸化グラフェン片と、ダブルウォールカーボンナノチューブと、が分散した分散液を塗付、及び乾燥し、カーボン膜を形成する工程と、
    　前記カーボン膜を二価のカチオンが溶解した溶液に浸漬する工程と、を有するナノカーボン分離膜の製造方法。     Applying a dispersion of dispersed graphene oxide pieces and double-walled carbon nanotubes and drying to form a carbon film;
    A step of immersing the carbon membrane in a solution in which a divalent cation is dissolved.
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