JP6694326B2 - Composite membrane - Google Patents

Description

  The present invention relates to composite membranes.

  In recent years, a membrane separation technique using a semipermeable membrane has been attracting attention from the viewpoint of energy saving, resource saving, and environmental protection. The semipermeable membrane is used as a nanofiltration membrane, a reverse osmosis membrane, or a forward osmosis membrane, and can be applied to separation, purification, manufacturing processes, etc. of various liquids including water.

In the forward osmosis treatment, the solutions with different solute concentrations are brought into contact with each other through the semipermeable membrane, and the osmotic pressure difference caused by the difference in solute concentration is used as the driving force, so that the dilute solution with low solute concentration changes to the concentrated solution with high solute concentration. Is a process for transmitting.
The forward osmosis treatment can concentrate the dilute solution or dilute the concentrated solution. The generator can also be driven by the positive osmotic energy as the fluid permeates from the dilute solution to the concentrated solution.
The forward osmosis treatment is similar to the reverse osmosis treatment in that water is preferentially permeated over the solute by using a semipermeable membrane. However, in the forward osmosis treatment, water is permeated from the dilute solution side to the concentrated solution side by utilizing the osmotic pressure difference, and at this point, the concentrated solution side is pressurized against the osmotic pressure difference to concentrate the water. It is different from the reverse osmosis treatment in which the solution side is permeated to the dilute solution side. Therefore, even if the semipermeable membrane used in the reverse osmosis treatment is directly applied to the forward osmosis treatment, it is not always suitable for the forward osmosis treatment.

  In reverse osmosis treatment, a concentrated solution is placed on one side of the membrane and a diluted solution is placed on the other side, and the concentrated solution side is pressurized against the osmotic pressure difference between the two solutions to concentrate water. Permeate from the solution side to the dilute solution side. Therefore, the reverse osmosis membrane is required to have strength enough to withstand the pressure on the concentrated solution side. Therefore, it is necessary for the reverse osmosis membrane to secure the strength without significantly increasing the porosity of the support layer. As a result, the space in which the solute can freely diffuse within the support layer is limited. However, in the reverse osmosis membrane, since the direction of water permeation and the direction of salt leakage are the same, internal polarization does not occur in the support layer, so the influence of the structure of the support layer on the water permeability (membrane permeation flow velocity) of the membrane is It is not definitive. Therefore, as the pressure applied to the concentrated solution side increases, the water permeability of the membrane can also increase.

  On the other hand, in a normal osmosis membrane, the internal concentration polarization of the support layer has a great influence on the water permeability of the membrane. In forward osmosis treatment, a concentrated solution is placed on one side of the membrane and a dilute solution is placed on the other side, and the osmotic pressure difference between the two solutions is used as the driving force to permeate water from the dilute solution side to the concentrated solution side. Let At this time, in order to increase the amount of water permeation of the normal osmosis membrane, it is important to reduce the internal concentration polarization of the support layer as much as possible and increase the effective osmotic pressure difference of the skin layer. If the space in which the solute freely diffuses is limited in the support layer, concentration polarization of the solute in the support layer easily occurs, and it becomes difficult to secure a sufficient water permeation amount. Therefore, in the normal osmosis membrane, the support layer is made of a material having a high porosity so as not to limit the diffusion of the solute in the interior as much as possible, and capable of ensuring a predetermined strength even when formed in such a manner. Constitution is important in providing the desired membrane performance.

Until now, various semipermeable membranes have been investigated as a membrane for normal osmosis treatment (normal osmosis membrane). For example, Patent Document 1 discloses a forward osmosis membrane in which a polyamide skin layer is laminated on a support layer made of polyacrylonitrile, polyacrylonitrile-vinyl acetate copolymer, polysulfone, or the like;
Patent Document 2 discloses a forward osmosis membrane in which a polyamide skin layer is laminated on a support layer made of an epoxy resin;
Patent Document 3 discloses a forward osmosis membrane in which a polyamide skin layer is laminated on a supporting layer made of polyethylene terephthalate (PET) or polypropylene;
Each is disclosed.
As described above, various forward osmosis membranes including the polymer forward osmosis membranes disclosed in Patent Documents 1 to 3 have been conventionally studied. However, there are still few normal osmosis membranes having high water permeability, and a high-performance normal osmosis membrane is desired.

The conventional polymer forward osmosis membrane has problems in durability against acid, organic solvent, etc. and heat resistance, and its application range is limited.
On the other hand, Patent Document 4 proposes a forward osmosis membrane flow system using a forward osmosis membrane containing zeolite, which is an inorganic material, and having excellent durability. However, the water permeability of the semipermeable membrane of Patent Document 4 is extremely low, and both durability and water permeability cannot be achieved at the same time, so there is a problem in practicality as a forward osmosis membrane flow system. In particular, there is a problem in practicability in applications requiring high pressure resistance such as osmotic pressure power generation.

  Patent Document 5 proposes a nanofiltration membrane having a support layer of polyolefin ketone, which has excellent organic solvent resistance. However, the membrane disclosed in Patent Document 5 has a small pore size and has a problem in liquid permeability.

Special table 2012-519593 gazette JP, 2013-013888, A Japanese Patent Publication No. 2013-502323 JP, 2014-039915, A Korean Published Patent No. 2015-0084503

  The present invention has been made in view of the conventional circumstances as described above, and the purpose thereof is to exhibit stable performance even in use under high pressure and have sufficient durability against various liquids, It is to provide a semipermeable membrane having excellent liquid permeability.

The present inventors have made extensive studies in order to solve the above problems. As a result, a porous membrane having a large film thickness, a high porosity and few cavities is used as a semipermeable membrane supporting layer, and a semipermeable membrane skin layer is laminated on one of the front and back surfaces or the inner and outer surfaces. It was found that the internal polarization of the support layer was effectively reduced. And a system with such a configuration
When used as a forward osmosis treatment system, it has high pressure resistance and can maintain high water permeability, or
The inventors have found that high liquid permeability can be maintained even when a liquid containing an organic compound is filtered under high pressure, and have completed the present invention.
The present invention also reveals an advantageous application method of the forward osmosis treatment system.
That is, the present invention is as follows.

[1] A composite membrane comprising a porous support layer and a layer having a semipermeable membrane performance on the porous support layer,
The porous support layer has the following conditions (1) and (2):
(1) The proportion of holes having an equivalent circle diameter of 1 μm or more is less than 30%, and (2) the film thickness is 100 μm or more,
The composite membrane as defined above.

[2] At least the layer having a semipermeable property is selected from a cellulose acetate film, a polyamide film, a polyvinyl alcohol / polypiperazine amide composite film, a sulfonated polyether sulfone film, a polypiperazine amide film, and a polyimide film. The composite film according to [1], which is a thin film layer containing one kind.

[3] The composite membrane according to [1] or [2], wherein the support layer has a flat plate shape.
[4] The composite membrane according to [1] or [2], wherein the support layer is a hollow fiber having an inner diameter / outer diameter ratio of 0.4 or less.

[5] The composite membrane according to any one of [1] to [4], wherein the porous support layer is a polyketone porous membrane.
[6] A forward osmosis treatment system comprising the composite membrane according to any one of [1] to [5].
[7] A reverse osmosis treatment system comprising the composite membrane according to any one of [1] to [5].

[8] A filtration system comprising the composite membrane according to any one of [1] to [5].
[9] A method for producing water, which comprises using the system according to any one of [6] to [8].
[10] A method for purifying an organic compound, which comprises using the system according to any one of [6] to [8].

[11] A method for concentrating a water-containing material, which comprises using the system according to any one of [6] to [8].
[12] A power generation method using the forward osmosis treatment system according to [6].

  The composite membrane of the present invention was able to improve both pressure resistance and water permeability by using a porous membrane having a high porosity and few cavities as a semipermeable membrane supporting layer. According to a preferred embodiment of the present invention, by using a polyketone porous membrane as the support layer of the semipermeable membrane, it is possible to suppress polarization of the internal concentration of the support layer and effectively increase the amount of water permeation, and also to include an organic compound. Since the durability against low osmotic pressure fluid can be improved, it can be used as a forward osmosis treatment system with stable performance even during long-term operation.

Therefore, the forward osmosis treatment system using the composite membrane of the present invention can be applied to, for example, desalination of seawater, desalination of brackish water, wastewater treatment, concentration of various valuables, treatment of associated water in oil / gas drilling, osmotic pressure. It can also be suitably used for power generation using two different liquids, sugars, fertilizers, dilution of refrigerants, and the like.
Furthermore, it has sufficient durability for organic compounds and high liquid permeability, and has high removal performance for foreign particles of fine particles or molecular size, so it is also suitable for purification and production of liquids containing organic solvents. It can be preferably used.

  Hereinafter, an example of the embodiment of the present invention will be described in detail. The following description relates to examples of the present invention, and the present invention is not limited thereto.

The composite membrane of the present invention has a porous support layer and a layer having a semipermeable membrane performance on the porous support layer, and the porous support layer has the following conditions (1) and (2):
(1) The proportion of holes having an equivalent circle diameter of 1 μm or more is less than 30%, and (2) the film thickness is 100 μm or more,
To be satisfied.

<Porous support layer>
The circle equivalent radius of the pores of the porous support layer in the composite membrane of the present invention is the diameter of the pores in the cross section in the thickness direction of the porous support layer. The shape of the hole is not particularly limited, and may be a circle, an ellipse, a polygon (triangle, quadrangle, etc.), or an irregular shape.
From the viewpoint of maintaining the strength of the membrane, the proportion of pores having an equivalent circle diameter of 1 μm or more is preferably less than 30%, more preferably less than 20%, even more preferably less than 5%, and most preferably 1%. Is less than. Here, the ratio of pores is a value represented by (cross-sectional area of pores having an equivalent circle diameter of 1 μm or more) / (cross-sectional area of the entire film) × 100 [%].

  The thickness of the support layer is preferably 100 μm or more. When the film thickness is less than 100 μm, the water permeability is high, but the strength of the film is low, so the pressure resistance is poor and the operating pressure is restricted when using the composite semipermeable membrane. From the viewpoint of strength, it is preferable that the film thickness is large, but the film thickness of the support layer is preferably less than 900 μm, and more preferably, because it is advantageous for downsizing of the film volume, downsizing of the device, and maintenance of water permeability. It is less than 490 μm, more preferably less than 190 μm.

  In the composite membrane of the present invention, the above-mentioned porous support layer is used, and a semipermeable membrane skin layer (layer having semipermeable membrane performance) is provided on one of the front and back surfaces or one of the inner and outer surfaces. With such a structure, when the composite membrane is used as, for example, a normal osmosis membrane, internal polarization of the support layer is effectively reduced, water permeability can be increased, and the number of cavities is reduced. By using a designed material and setting the film thickness to a large value of 100 μm or more, the pressure resistance becomes high, and even when used under high pressure, it is possible to stably maintain a high water permeability. This characteristic can increase power generation efficiency and can be used for a long period of time in applications requiring pressure resistance of 1.5 MPa or more, such as osmotic pressure power generation using seawater and fresh water. Will give you an advantage.

  The support layer has a porous structure and allows solute and water to pass through the through-holes inside. In order to effectively suppress the internal concentration polarization in the support layer, it is preferable that pores having a larger pore size be formed in the support layer. From such a viewpoint, it is preferable that the support layer has pores having a maximum pore diameter of 50 nm or more.

  The maximum pore size is measured by the bubble point method (based on ASTM F316-86 or JIS K3832). When a porous membrane having a maximum pore size of 50 nm or more is used as the support layer of the forward osmosis membrane, it is possible to reduce internal concentration polarization in the support layer, so that the performance of the forward osmosis membrane can be improved. Since the internal concentration polarization is reduced as the maximum pore size is increased, the maximum pore size of the support layer is preferably 50 nm or more, more preferably 80 nm or more, further preferably 100 nm or more, and most preferably 130 nm or more. When the maximum pore size is larger than 50 nm, the molecular weight cutoff is larger than 100,000.

  On the other hand, as the maximum pore size is increased, it becomes difficult to support the semipermeable membrane skin layer, and the pressure resistance may deteriorate. From such a viewpoint, the maximum pore size of the support layer is preferably 2 μm or less, more preferably 1.5 μm or less, further preferably 1 μm or less, and most preferably 0.6 μm or less.

The porosity of the support layer is not particularly limited, but the higher the porosity, the easier the diffusion of the solute in the support layer, and the suppression of the internal concentration polarization of the support layer to increase the water permeability of the forward osmosis membrane. Become. From this, the porosity of the support layer is preferably 60% to 95%, more preferably 70% to 95%, further preferably 80% to 95%. The porosity of the polyketone support layer (porous film) is calculated by the following mathematical formula (1).
Porosity (%) = (1-G / ρ / V) × 100 (1)
[In the formula (1), G is the mass (g) of the support layer, ρ is the mass average density (g / cm ³ ) of the support layer, and V is the volume (cm ³ ) of the support layer. ]

In the above formula (1), when the support layer is composed of two kinds of resins having different densities, the mass average density ρ is the sum of the values obtained by multiplying the density of each resin by the constituent mass ratio. .. For example, in the case where each of the fibers composed of the resin A having the density ρA, the resin B having the density ρB, and the resin P having the density ρp is a support layer composed of a mass ratio of GA, GB, and GP, the mass average density is ρ is represented by the following equation (2).
Mass average density ρ = (ρA ・ GA + ρB ・ GB + ρP ・ GP) / (GA + GB + GP) (2)

  The material (raw material) forming the porous support layer is not particularly limited. However, it is preferable to use a material that is highly resistant to various liquids. From the viewpoint of high durability against various liquids and good affinity, the porous support layer in the present invention is more preferably a polyketone support layer.

The polyketone polymer (hereinafter referred to as polyketone) constituting the polyketone support layer is composed of a copolymer of carbon monoxide and olefin. By forming the support layer from polyketone, it becomes possible to form a support layer having a high porosity while ensuring strength.
Conventionally, a reverse osmosis membrane may require a supporting substrate such as a nonwoven fabric. However, since the polyketone support layer has high self-supporting property, such a support base material is also unnecessary. This makes it possible to reduce the thickness of the obtained composite film. Furthermore, the polyketone can be easily formed into any shape such as a flat plate shape (flat membrane shape) or a hollow fiber shape, and thus can be easily applied to a conventionally known membrane module.

  From the viewpoint of ensuring strength and increasing the porosity, the polyketone supporting layer contains polyketone, which is a copolymer of carbon monoxide and one or more kinds of olefins, in a proportion of 10% by mass or more and 100% by mass or less. Preferably. The higher the content of polyketone in the polyketone support layer, the more preferable. The polyketone content in the polyketone support layer is preferably 70% by mass or more, more preferably 80% by mass or more, and further preferably 90% by mass or more. The content of the polyketone in the polyketone supporting layer is determined by, for example, a method of dissolving and removing the polyketone with a solvent that dissolves only the polyketone among the components that form the supporting layer, a method of dissolving and removing the other than the polyketone with a solvent that dissolves only the polyketone, and the like. Can be confirmed by.

  In the synthesis of polyketone, as the olefin to be copolymerized with carbon monoxide, any kind of compound can be selected according to the purpose. Examples of the olefin include chain olefins such as ethylene, propylene, butene, hexene, octene and decene; alkenyl aromatic compounds such as styrene and α-methylstyrene; cyclopentene, norbornene, 5-methylnorbornene, tetracyclododecene, Examples thereof include cyclic olefins such as tricyclodecene, pentacyclopentadecene, and pentacyclohexadecene; halogenated alkenes such as vinyl chloride and vinyl fluoride; acrylic acid esters such as ethyl acrylate and methyl methacrylate; and vinyl acetate. From the viewpoint of ensuring the strength of the polyketone support layer, the type of olefin to be copolymerized is preferably 1 to 3 types, more preferably 1 to 2 types, and further preferably 1 type.

The polyketone preferably has a repeating unit represented by the following formula (1).
-RC (= O)-(1)
[In Formula (1), R represents a C2-C20 hydrocarbon group which may have a substituent. ]
Examples of the substituent for the hydrocarbon group for R in the above formula (1) include a halogen atom, a hydroxyl group, an ether group, a primary amino group, a secondary amino group, a tertiary amino group, a quaternary ammonium group, and a sulfonic acid. Group, a sulfonic acid ester group, a carboxylic acid group, a carboxylic acid ester group, a phosphoric acid group, a phosphoric acid ester group, a thiol group, a sulfide group, an alkoxysilyl group, and one or more functional groups selected from the group consisting of silanol groups. Can be raised. The ketone unit represented by the above formula (1) may be composed of only one type, or may be a combination of two or more types.

2-8 are more preferable, as for carbon number of the hydrocarbon group R of the said Formula (1), 2 or 3 are further more preferable, and 2 is the most preferable. The repeating unit constituting the polyketone particularly preferably contains a large amount of 1-oxotrimethylene repeating unit represented by the following formula (2).
_{-CH 2 -CH 2 -C (= O} ) - (2)

From the viewpoint of ensuring the strength of the polyketone support layer, the proportion of 1-oxotrimethylene repeating units in the repeating units constituting the polyketone is preferably at 7 0 mol% or more, more that 90 mol% or more It is preferably 95 mol% or more, and further preferably. The proportion of 1-oxotrimethylene repeating units may be 100 mol%. Here, 100 mol% means that repeating units other than 1-oxotrimethylene are not observed except for polymer end groups in known elemental analysis, NMR (nuclear magnetic resonance), gas chromatography and the like. .. Typically, the structure of the repeating units that make up the polyketone and the amount of each structure is confirmed by NMR.

  The polyketone can be obtained by polymerizing carbon monoxide and an olefin using, for example, palladium or nickel as a catalyst. For the production of the polyketone support layer, for example, the methods described in JP-A-2002-348401 and JP-A-2-4431 can be referred to.

The porous support layer in the present invention may be a symmetric membrane or an asymmetric membrane. When the porous support layer is an asymmetric membrane, the semipermeable membrane skin layer described below is preferably provided on the dense surface of the support layer.
The porous support layer may have any shape. For example, it may have a flat plate shape (flat membrane shape), a hollow fiber shape, or the like. From the viewpoint that the porosity of the membrane is not reduced more than necessary, it is preferable that the supporting layer does not contain a reinforcing fiber such as a nonwoven fabric or a filler.
When the support layer is in the form of hollow fiber, it is preferable that the wall of the hollow fiber is thick from the viewpoint of suppressing collapse of the hollow fiber due to external pressure and peeling of the skin layer. From this viewpoint, the ratio of the inner diameter to the outer diameter (= inner diameter / outer diameter) of the hollow fiber is preferably less than 0.4. On the other hand, if the wall thickness is too thick with respect to the cross-sectional area of the hollow portion of the hollow fiber, the pressure loss will be too large. Therefore, the ratio of inner diameter / outer diameter of the hollow fiber is preferably 0.1 or more, more preferably 0.2 or more.
Such a porous support layer can be manufactured by a known method. When the porous support layer is a polyketone support layer, it is convenient to use the following method, for example.

  A polyketone dope is prepared by dissolving a polyketone in a solution containing a metal halide salt (eg, a zinc halide salt, an alkali metal halide salt, etc.), and the dope is passed through a film die, a double-tube orifice, etc. in a coagulation bath. It is then discharged into a flat plate shape or hollow fiber shape. Further, by washing and drying this molded body, a polyketone support layer is obtained. In this case, for example, the porosity and the pore diameter of the polyketone support layer can be appropriately adjusted by adjusting the polymer concentration in the dope and the temperature of the coagulation bath.

  Alternatively, the polyketone is dissolved in a good solvent (for example, an aqueous solution containing resorcinol, hexafluoroisopropanol, m-cresol, o-chlorophenol, a zinc halide salt, an alkali metal halide salt, etc.). From the viewpoint of increasing the surface openness and the porosity, an aqueous solution containing resorcinol is preferably used. The polyketone support layer can also be obtained by casting the obtained solution on a substrate, immersing it in a non-solvent (for example, methanol, isopropanol, acetone, water, etc.), and further washing and drying. In this case, for example, the porosity and the pore diameter of the polyketone porous membrane can be appropriately adjusted by adjusting the mixing ratio of the polyketone and the good solvent, the kind of the non-solvent, and the like.

<Semi-permeable membrane skin layer>
A semipermeable membrane skin layer is formed on the porous support layer in the composite membrane of the present invention.
The semipermeable membrane skin layer is a layer having a semipermeable membrane performance, and known materials used for conventional forward osmosis membranes, reverse osmosis membranes, nanofilters and the like may be applied as they are. For example, a cellulose acetate film, a polyamide film, a polyvinyl alcohol / polypiperazine amide composite film, a sulfonated polyether sulfone film, a polypiperazine amide film, a polyimide film and the like can be exemplified, and at least one selected from these is included. A thin film layer is preferably used. The material of the semipermeable membrane skin layer may be selected in consideration of the low osmotic pressure solution, the high osmotic pressure solution, the durability against the organic solvent used, the liquid permeability, and the like.
In the present invention, a semipermeable membrane skin layer made of a polyamide membrane is particularly preferable in terms of easiness of forming a thin film on the porous support layer.

The thickness of the semipermeable membrane skin layer is not particularly limited, but is preferably 0.05 μm to 2 μm, more preferably 0.05 μm to 1 μm.
The thickness of the semipermeable membrane skin layer can be measured by observing the cross section of the composite membrane with an SEM.

<Other layers>
The composite membrane of the present invention may be laminated on one side or both sides with a fabric such as a woven fabric or a non-woven fabric, or another layer such as a membrane, for the purpose of suppressing performance deterioration due to adsorption of contaminants. However, it is preferable not to include other layers from the viewpoint of increasing the effective area through which the liquid permeates and from the viewpoint of being advantageous in downsizing of the device.

<Normal Osmosis Treatment System>
The composite membrane of the present invention can be used as a semipermeable membrane in a forward osmosis treatment system utilizing the forward osmosis phenomenon. In this forward osmosis treatment system, a low osmotic pressure solution is arranged on one surface side of the composite membrane of the present invention, and a high osmotic pressure solution having a higher osmotic pressure than the low osmotic pressure solution is supplied to the other surface side. Then, fluid movement occurs from the low osmotic pressure solution side to the high osmotic pressure solution side, thereby increasing the flow rate on the high osmotic pressure solution side.
In this case, which of the low osmotic pressure solution side and the high osmotic pressure solution side the semipermeable membrane skin layer side of the composite membrane of the present invention is to be arranged depends on the water permeability of the liquid to be treated and the fouling resistance. It can be appropriately determined by those skilled in the art in consideration of the above.

Here, when an aqueous solution of an organic compound is used as the low osmotic pressure solution, the concentration of the organic compound in the aqueous solution of the organic compound can be increased by the forward osmosis treatment using the forward osmosis treatment system described above, and the purification of the organic compound can be performed. It is suitable as a part of the process.
Similarly, when an aqueous solution (hydrate) containing a predetermined target substance is used as the low osmotic pressure solution, the hydrate can be concentrated by the forward osmosis treatment.
In addition, depending on the combination of the low osmotic pressure solution and the high osmotic pressure solution, the organic solvent can be fluid-transferred from the low osmotic pressure solution to the high osmotic pressure solution.

<Reverse osmosis treatment system>
The composite membrane of the present invention can be used as a semipermeable membrane in a reverse osmosis treatment system utilizing the reverse osmosis phenomenon. In this reverse osmosis treatment system, a low osmotic pressure solution is arranged on one surface side of the composite membrane of the present invention, and a high osmotic pressure solution having a higher osmotic pressure than the low osmotic pressure solution is supplied to the other surface side to obtain high osmosis. When pressure is applied to the pressure solution side, fluid is moved from the high osmotic pressure solution side to the low osmotic pressure solution side, thereby increasing the flow rate on the low osmotic pressure solution side.
In this case, it is preferable to arrange the semipermeable membrane skin layer side of the composite membrane of the present invention on the high osmotic pressure solution side.
In particular, when the porous support layer is a polyketone support layer, it has high durability against an organic solvent and other organic compounds, and a liquid containing an organic solvent or an organic compound in at least one of a low osmotic pressure solution and a high osmotic pressure solution. Even in the treatment, stable performance can be exhibited for a long time.

Here, when an aqueous solution of an organic compound is used as the high osmotic pressure solution, the concentration of the organic compound in the aqueous solution of the organic compound can be increased by the reverse osmosis treatment using the above reverse osmosis treatment system, and the purification of the organic compound can be performed. It is suitable as a part of the process.
Similarly, when an aqueous solution (hydrous substance) containing a predetermined target substance is used as the high osmotic pressure solution, the hydrous substance can be concentrated by the reverse osmosis treatment.

<Power generation method>
The power generation method of the present invention uses the forward osmosis treatment system of the present invention.
In the power generation method of the present invention, the composite membrane of the present invention is used as a normal osmosis membrane, a low osmotic pressure solution is brought into contact with the semipermeable membrane skin layer side, and a high osmotic pressure solution is brought into contact with the opposite side thereof. Alternatively, the high osmotic pressure solution may be brought into contact with the semipermeable membrane skin layer side, and the low osmotic pressure solution may be brought into contact with the opposite side. Then, by permeating water from the low osmotic pressure solution to the high osmotic pressure solution through the composite membrane of the present invention, the flow rate of the high osmotic pressure solution is increased, and the water flow generator is driven at the increased flow rate to generate electricity. To do.

Hereinafter, the present invention will be described in more detail with reference to Examples. In the following description, specific compounds, numerical values and the like will be described, but the scope of the present invention is not limited to these.
The measuring method of each measured value in the following examples is as follows.

(1) Maximum pore size and average pore size:
The maximum pore size was measured using a PMI palm porometer (model: CFP-1200AEX), using PMI's Gullwick (surface tension = 15.6 dynes / cm) as the immersion liquid, and using JIS K3832 (bubble point method). The measurement was performed according to the standards. The average pore diameter was measured by the half dry method according to ASTM E1294-8.

(2) Average Thickness of Porous Support Layer and Semipermeable Membrane Skin Layer The composite membrane in which the semipermeable membrane skin layer was laminated was frozen and cut to prepare a cross-sectional sample of the membrane, which was used as a sample. This was observed using a scanning electron microscope (manufactured by Hitachi Ltd., model S-4800) under the conditions of an acceleration voltage of 1.0 kV, a WD of 5 mm standard ± 0.7 mm, and an emission current setting of 10 ± 1 μA. The average thickness of each of the porous support layer and the semipermeable membrane skin layer was measured from the obtained SEM photograph.

(3) Ratio of pores with equivalent circle diameter of 1 μm or more A porous layer (without a semipermeable skin layer) is enclosed in a gelatin capsule together with ethanol, immersed in liquid nitrogen and cooled to freeze ethanol. The sample was cut in the state where it was left to prepare a cross-section section sample.
The obtained section sample was photographed with an electron microscope at a magnification of 500 to 50,000 times. The photographed negative image was analyzed by the following method using an image analyzer (IP1000-PC: manufactured by Asahi Kasei Corp.).

The captured image was binarized by particle analysis. The parameters set at this time are
(1) Lightness (dark) of particles,
(2) Threshold (automatic),
(3) Shading correction processing (none),
(4) Shrinkage separation processing (straight line separation: number of shrinkage times 10, non-separation radius 1, separation contact degree 10),
(5) Outer frame correction (Yes), and (6) Hole filling processing (Yes)
Met.
From the binarized image obtained above, a hole in contact with the measurement area line (outer frame of the measured rectangular range), a part of the hole outside the measurement range, a resin part other than polyketone, and the resin After removing the holes, particle analysis was performed to determine the equivalent circle diameter of the target holes.
The above analysis was carried out for 5 fields of view taken from the front surface to the back surface of the film while shifting in the thickness direction of the film, and then the arithmetic mean value was calculated for the measured circle equivalent diameters of all the holes. Then, the total area of the holes having the equivalent circle diameter of 1 μm or more was calculated, and the ratio P of the holes having the equivalent circle diameter of 1 μm or more was calculated by the following equation (3).
Ratio P = (total area of holes having equivalent circle diameter of 1 μm or more) / (cross-sectional area of the entire film) × 100 [%] (3)

(4) Evaluation of Membrane Performance Both the pressure-driven reverse osmosis treatment test and the forward osmosis-driven forward osmosis treatment test were performed to obtain the value of the structural parameter S representing the index of the degree of internal concentration polarization of the support layer. , Each forward osmosis membrane was evaluated. At the same time, a water permeation coefficient A and a salt permeation coefficient B representing the permeation performance of the semipermeable membrane skin layer were determined.

(4-1) Reverse Osmosis Treatment Test In the reverse osmosis treatment test, reverse osmosis treatment is performed by pressurizing ultrapure water or a 0.1 M NaCl aqueous solution in the range of 0 MPa to 2 MPa, and the water permeability J _w ^{water RO} or J _w ^{Determine NaCl RO} (unit: L · m ⁻² · h ⁻¹ ) and salt inhibition rate R (unit:%) (= 1− (NaCI concentration of feed solution / NaCl concentration of permeate)) Then, the water permeability coefficient A and the salt permeability coefficient B of the semipermeable membrane skin layer were calculated. In calculating both coefficients, Sidney Loeb et al. , J. Membr. Sci., 129 1 (1997) 243-249, and K.S. L. Lee et al. , J. Membr. Sci. , 8 (1981) 141-171.
A = J _w ^{water RO} / ΔP
B = J _w ^{NaCl RO} ((1-R) / R) exp (−J _w ^{NaCl RO} / k _f ).
P: Applied pressure
R: rejection rate (= 1- _Cp / _Cb )
C _p : Permeate concentration
C _b : bulk solution concentration of the feed solution
k _f : mass transfer coefficient (= J _w ^{NaCl RO} / ln [ΔP (1-J _w ^{NaCl RO} / J _w ^{water RO} ) / (π _b −π _p )]
π _p : Osmotic pressure of permeate
π _b : Osmotic pressure of bulk solution

(Pressure resistance)
In the above reverse osmotic pressure test, the maximum pressure at which the osmotic membrane did not break when the applied pressure by the ultrapure water or the NaCl aqueous solution was changed was taken as the value of the pressure resistance of the osmotic membrane.

(4-2) Forward Osmosis Test In the forward osmosis treatment test, a 0.3 M to 1.2 M NaCl aqueous solution is used as a concentrated solution (Draw solution), and ultrapure water is used as a dilute solution (Feed Solution). I went. At this time, the semipermeable membrane skin layer was subjected to forward osmosis treatment toward the dilute solution side, the water permeability J _w ^FO (unit: L · m ⁻² · h ⁻¹ ) was measured, and the water permeability coefficient obtained above was calculated. The structural parameter S of the porous support layer was calculated by substituting A and the salt permeation coefficient B into the following formula. In calculating the structural parameter S, A. Tiraferri et al., J. Reference was made to Membr. Sci., 367, (2011) 340-352.
J _w ^FO = (D / S) ln [(B + Aπ _DS ) / (Aπ _FS + B + J _w ^FO )]
D: Diffusion coefficient of solute
π _DS : Bulk osmotic pressure of concentrated solution
π _FS : Bulk osmotic pressure of dilute solution

  Composite films were prepared according to Examples 1 to 3 and Comparative Examples 1 to 5 below, and evaluated by the above methods.

<Example 1>
A polyketone having an intrinsic viscosity of 3.0 dl / g in which ethylene and carbon monoxide are completely alternating-polymerized is used as a polymer solution composed of 10% by mass of polyketone, 58.5% by weight of resorcinol, and 31.5% by weight of water. It was cast on a glass substrate with a coating thickness of 400 μm using an applicator. Then, it was immersed in a coagulation bath consisting of a water / methanol mixed solvent (70/30 (w / w)) to form a polyketone porous membrane (asymmetric membrane). The obtained polyketone porous film was peeled from the glass plate, fixed on a metal frame, washed successively with water, acetone, and hexane, and air-dried to obtain a 137 μm-thick polyketone support layer. The ratio of pores having a circle-equivalent diameter of 1 μm or more measured in the obtained support layer was 0%, and the maximum pore diameter was 157 nm. On the other hand, the porosity was 81.2%.

On the polyketone support layer (the side which was not in contact with the glass plate when cast on the glass plate), 1,3-phenylenediamine 2% by mass, camphorsulfonic acid 2.3% by mass, triethylamine 1.1% by mass. %, Sodium dodecylsulfate 0.15% by mass, and hexamethylphosphoric triamide 3.0% by mass were applied, and the mixture was left standing for 300 seconds. Then, in order to remove the excess amine aqueous solution, the membrane was left vertical and allowed to stand for 60 seconds.
Then, a hexane solution of 1,3,5-trimesoyl chloride (trimesinic acid trichloride 0.15% by mass) was applied from the above and left standing for 120 seconds. The membrane was left vertical for 60 seconds to remove excess chloride solution.
The laminate thus obtained was subjected to an annealing treatment at 90 ° C. for 600 seconds and then sufficiently washed with water to obtain a composite membrane 1 having a polyamide skin layer formed on a polyketone support layer.
The composite film 1 had a J _w ^FO of 24.8 L · m ⁻² · h ⁻¹ (NaCL = 0.6 M) and a withstand voltage of 1.9 MPa, which showed high withstand pressure.
As described above, even when the maximum pore diameter of the support layer is as large as 157 nm, a high water permeability can be obtained by reducing the proportion of pores having an equivalent circle diameter of 1 μm or more and setting the thickness of the support layer to 100 μm or more. It was verified that a composite film having both performance and pressure resistance could be obtained. In this case, since the support has a high porosity and a uniform structure, the internal concentration polarization can be suppressed more than expected even if the film thickness is increased, and high water permeability can be maintained.

<Example 2>
A composite membrane 2 was obtained in the same manner as in Example 1 except that the composition of the water / methanol mixed solvent in the coagulation bath was changed to water / methanol = 65/35 (w / w). .. The thickness of the polyketone support layer in the composite film 2 was 150 μm. The ratio of pores having an equivalent circle diameter of 1 μm or more measured in the support layer was 0%, and the maximum pore diameter was 182 nm. On the other hand, the porosity was 83.0%.
The composite membrane 2 had a J _w ^FO of 25.1 L · m ⁻² · h ⁻¹ (NaCL = 0.6 M) and a withstand pressure of 1.8 MPa, which showed high withstand pressure.
As described above, even when the maximum pore diameter of the support layer is as large as 182 nm, a high water permeability can be obtained by reducing the proportion of pores having an equivalent circle diameter of 1 μm or more and setting the thickness of the support layer to 100 μm or more. It was verified that a composite film having both performance and pressure resistance could be obtained.

<Example 3>
A composite membrane 3 was obtained in the same manner as in Example 1 except that the composition of the water / methanol mixed solvent in the coagulation bath was changed to water / methanol = 55/45 (w / w). .. The thickness of the polyketone support layer in the composite film 3 was 167 μm. The ratio of pores having an equivalent circle diameter of 1 μm or more measured in the support layer was 0%, and the maximum pore diameter was 234 nm. On the other hand, the porosity was 85.1%.
The composite film 3 had a J _w ^FO of 25.1 L · m ⁻² · h ⁻¹ (NaCL = 0.6 M) and a withstand pressure of 1.5 MPa, which showed high withstand pressure.
As described above, even when the maximum pore diameter of the support layer is as large as 234 nm, a high water permeability can be obtained by reducing the proportion of pores having an equivalent circle diameter of 1 μm or more and setting the thickness of the support layer to 100 μm or more. It was verified that a composite film having both performance and pressure resistance could be obtained.

<Comparative Example 1>
A composite membrane 4 was obtained in the same manner as in Example 1 except that the composition of the water / methanol mixed solvent in the coagulation bath was changed to water / methanol = 75/25 (w / w). .. The thickness of the polyketone support layer in the composite film 4 was 145 μm. The ratio of pores having an equivalent circle diameter of 1 μm or more measured in the support layer was 30%, and the maximum pore diameter was 94 nm. On the other hand, the porosity was 81.9%.
The J _w ^FO of the composite film 4 was 19.2 L · m ⁻² · h ⁻¹ and the pressure resistance was 0.8 MPa. The water permeation rate was less than 20.0 L · m ⁻² · h ⁻¹ , and the pressure resistance was also reduced.
As described above, in the case of using a support layer having a hole equivalent ratio of 1 μm or more and a ratio of pores of 30%, the water resistance of the obtained composite membrane is high even if the support layer thickness is set to 100 μm or more. It was insufficient. In the composite membrane of this comparative example, the maximum pore diameter of the support layer used was relatively large at 94 nm, but the water permeation amount when the support layer thickness was 145 μm was less than 20.0 L · m ⁻² · h ^−1. Met.

<Comparative example 2>
A composite film 5 was obtained in the same manner as in Comparative Example 1 except that the coating was performed with a coating thickness of 200 μm in Comparative Example 1. The thickness of the polyketone support layer in the composite film 5 was 69 μm. The ratio of pores having an equivalent circle diameter of 1 μm or more measured in the support layer was 26%, and the maximum pore diameter was 115 nm. On the other hand, the porosity was 80.6%.
The J _w ^FO of the composite film 5 was 22.3 L · m ⁻² · h ⁻¹ and the pressure resistance was 0.6 MPa, and the pressure resistance was low.
As described above, when the ratio of the holes having the equivalent circle diameter of 1 μm or more is 26% and the supporting layer having the film thickness of 69 μm is used, the pressure resistance of the obtained composite film may be insufficient. confirmed.

<Comparative example 3>
A composite film 6 was obtained in the same manner as in Example 1 except that the coating was performed with the coating thickness being 200 μm. The thickness of the polyketone support layer in the composite film 6 was 77 μm. The proportion of pores having a circle-equivalent diameter of 1 μm or more measured on the obtained support layer was 0%, and the maximum pore diameter was 123 nm. On the other hand, the porosity was 83.8%.
The J _w ^FO of the composite film 6 was 27.9 L · m ⁻² · h ⁻¹ and the pressure resistance was 0.6 MPa. Although the water permeability was high, the pressure resistance was low.
As described above, when the proportion of the holes having the equivalent circle diameter of 1 μm or more is 0% and the support layer having the film thickness of 77 μm is used, the pressure resistance of the obtained composite film may be insufficient. confirmed.

<Comparative example 4>
A composite film 7 was obtained in the same manner as in Example 2 except that the coating was performed with a coating thickness of 200 μm. The thickness of the polyketone support layer in the composite film 7 was 83 μm. The proportion of pores having a circle-equivalent diameter of 1 μm or more measured in the support layer was 0%, and the maximum pore diameter was 155 nm. On the other hand, the porosity was 84.5%.
The composite membrane 7 had a J _w ^FO of 30.8 L · m ⁻² · h ⁻¹ and a pressure resistance of 0.4 MPa, and although the water permeability was high, the pressure resistance was low.
As described above, when the proportion of the holes having the equivalent circle diameter of 1 μm or more is 0% and the supporting layer having the film thickness of 83 μm is used, the pressure resistance of the obtained composite film may be insufficient. confirmed.

<Comparative Example 5>
A composite film 8 was obtained in the same manner as in Example 3 except that the coating was performed with the coating thickness being 200 μm. The thickness of the polyketone support layer in the composite film 8 was 97 μm. The ratio of the holes having an equivalent circle diameter of 1 μm or more measured in the support layer was 0%, and the maximum hole diameter was 290 nm. On the other hand, the porosity was 87.1%.
The composite membrane 8 had a J _w ^FO of 32.7 L · m ⁻² · h ⁻¹ and a withstand pressure of 0.2 MPa, and although the water permeability was high, the withstand pressure was extremely low.
As described above, when the proportion of the holes having the equivalent circle diameter of 1 μm or more is 0% and the support layer having the film thickness of 97 μm is used, the pressure resistance of the obtained composite film may be insufficient. confirmed.

  All the above results are shown in Table 1 together with the water permeability coefficient A and the salt permeability coefficient B.

  In Table 1 above, the water permeability Jw is a value when the NaCl pressure is 0.6 MPa.

Example 4 thus create a forward osmosis hollow fiber membrane below papermaking, by the method described above, maximum pore size, the ratio of the average pore diameter of a circle equivalent diameter 1μm or more holes, water permeability Jw, and the breakdown voltage, each of the above methods In addition to the evaluation, the inner diameter and outer diameter of the obtained hollow fiber membrane and their ratio (inner diameter / outer diameter) were evaluated by the following methods.

(5) inside diameter, outside diameter, and an inner diameter / outer diameter ratio Example hollow fiber membrane obtained in 4 (polyketone hollow fiber membrane hollow fiber membrane polyamide thin layer is laminated on the outer surface of) frozen, longitudinal A cross-section sample was prepared by cutting the sample in a direction perpendicular to. For this cross-section sample, using a scanning electron microscope (manufactured by Hitachi Ltd., model S-4800), observation was made under the conditions of an acceleration voltage of 1.0 kV, a WD of 5 mm standard ± 0.7 mm, and an emission current setting of 10 ± 1 μA, An SEM image was obtained. With respect to the obtained SEM image, the inner diameter and the outer diameter at arbitrary two points were measured. The same measurement was performed using n as 5 points, and the average inner diameter and the average outer diameter of the hollow fiber obtained as a number average value of 10 points were adopted as the inner diameter and the outer diameter, respectively. The inner diameter / outer diameter ratio was calculated from these values of inner diameter and outer diameter.

<Example 4>
A polyketone having an intrinsic viscosity of 2.2 dl / g obtained by completely copolymerizing ethylene and carbon monoxide was added to a 65 mass% resorcinol aqueous solution so that the polyketone concentration would be 15 mass%, and dissolved by stirring at 80 ° C. for 2 hours. Thus, defoaming was performed to obtain a uniform and transparent dope.
The dope (dope viscosity: 100 poise) adjusted to a temperature of 50 ° C. using a double-tube orifice spinner (D1: 0.6 mm, D2: 0.33 mm, D3: 0.22 mm) is an outer annular orifice. From the above, a 25 mass% aqueous methanol solution was simultaneously discharged from the inner circular orifice into a coagulation bath consisting of a 40 mass% aqueous methanol solution to obtain a coagulated product. The obtained coagulated product was pulled up and wound while washing with water to obtain a polyketone hollow fiber membrane. The obtained hollow fiber membrane was cut into a length of 70 cm, bundled and washed with water. The hollow fiber membrane bundle after washing with water was subjected to solvent substitution with acetone and then with hexane, and then dried at 50 ° C. The polyketone hollow fiber membrane thus obtained had a porosity of 81% and a maximum pore size of 150 nm.
Both ends of 5 mm of the above polyketone hollow fiber membrane (length: 21 cm) were sealed with an adhesive, and 2.0% by mass of m-phenylenediamine, 4.0% by mass of camphorsulfonic acid, 2.0% by mass of triethylamine, and It was immersed in an aqueous solution (first monomer solution) containing 0.25% by mass of sodium dodecyl sulfate, allowed to stand at room temperature for 300 seconds, then taken out of the aqueous solution, and the adhering liquid on the outside was wiped off with absorbent cotton to remove it. Then, it was immersed for 120 seconds in a 0.15 mass% concentration trimesic acid chloride hexane solution (second monomer solution) to carry out interfacial polymerization. Then, the hollow fiber membrane of Example 4 in which the polyamide thin film layer was laminated on the outer surface of the polyketone hollow fiber membrane was produced by drying at 90 ° C. for 600 seconds in a nitrogen atmosphere.
In the hollow fiber membrane of Example 4, the one end sealing portion (each 5 mm) was cut, both the inner cylinder side and the outer cylinder side were washed with pure water, and then the outer side of the polyketone hollow fiber membrane. Various tests were carried out as a forward osmosis hollow fiber membrane having a polyamide thin film layer laminated on the surface.
The normal osmosis hollow fiber membrane had an inner diameter of 198 μm, an outer diameter of 504 μm, and a polyamide thin film layer had a thickness of 0.3 μm.
When this forward osmosis hollow fiber membrane was evaluated by the above-mentioned method, J _w ^FO was 23.2 L · m ⁻² · h ⁻¹ (NaCL = 0.6 M), and the pressure resistance was 1.6 MPa, which was high pressure resistance. showed that.

The results of Example 4 above are summarized in Table 2 below.

  In Table 2 above, the water permeability Jw is a value when the NaCl pressure is 0.6 MPa.

[Permeability evaluation for various organic solvents]
<Examples X1 to X10>
Through the composite membrane 1 obtained in the same manner as in Example 1, each stock solution (water and organic solvent) shown in Table 3 was used for pressure filtration under the conditions of 0.5 MPa, and 2 hours after pressurization. The liquid permeation amount in 3 hours was measured. Then, the permeation coefficient A (L · m ⁻² · h ⁻¹ ) was calculated by dividing the liquid permeation amount by the area of the portion through which the liquid permeates. The results are shown in Table 3.

According to Table 3 above, aprotic polar organic solvents such as DMF, DMSO, and NMP have better liquid permeability than protic polar organic solvents such as alcohol. In the case of an aprotic polar organic solvent such as DMF, DMSO, NMP, it was observed that the semipermeable membrane skin layer after liquid permeation was slightly swollen.
When the support layer after filtration was observed with the naked eye, neither contraction nor swelling occurred, and no deterioration was observed. This is a result showing that the composite membrane of the present invention having a polyketone porous membrane as a support layer is suitable as a membrane for filtering various organic solvents.
From the results of Table 3, further, when the composite membrane of the present invention is used, one organic solvent is selectively selected from a solution in which two or more kinds of solvents are mixed by utilizing the difference in permeability between water and the organic solvent. It is understood that it is also possible to extract.

[Evaluation of rejection rate in various organic solvents]
<Examples Y1 to Y5>
Through the composite semipermeable membrane 1 obtained in the same manner as in Example 1, various stock solutions shown in Table 4 (water containing methyl orange (Mw = 327) and an organic solvent) were filtered under pressure of 0.5 MPa. Then, 10 mL of the permeated liquid was collected 3 hours or more after the pressurization. The concentration of methyl orange in the undiluted solution before filtration and the permeated solution after filtration was compared with an ultraviolet-visible absorptiometer to determine the inhibition rate.
The results are shown in Table 4.

  As shown in Table 4, a high rejection rate was obtained when DMF, DMSO, and alcohol were used. From this, it was suggested that the liquid containing the organic solvent can be purified by the reverse osmosis method using the composite membrane of the present invention.

<Example Z1>
Through the composite membrane 1 obtained in the same manner as in Example 1, a DMF solution mixed with 10 nm colloidal silica (1 ppm) was subjected to pressure filtration under the condition of 0.5 MPa, and permeation after 3 hours or more from the pressurization. 100 mL of the liquid was collected.
The concentration of colloidal silica in the undiluted solution before filtration and the permeated solution after filtration was measured by ICP-MS and compared to determine the inhibition rate of colloidal silica. The rejection rate of colloidal silica was 99% or more.

  The embodiments of the present invention have been described above. However, the present invention is not limited to these, and can be appropriately modified without departing from the spirit of the invention.

INDUSTRIAL APPLICABILITY The composite membrane of the present invention has high pressure resistance and excellent water permeability. For example, desalination of seawater, desalination of brine, wastewater treatment, concentration of various valuables, treatment of associated water in oil / gas drilling. It can be preferably used for power generation using two liquids having different osmotic pressures, dilution of sugars, fertilizers, refrigerants, and the like. The composite film of the present invention exhibits sufficient durability to an organic compound and high liquid permeability, and also has high removal performance from foreign particles having a particle size or a molecular size, and therefore, for example, a liquid containing an organic solvent. Can also be suitably used for the purification, production and the like.
INDUSTRIAL APPLICABILITY The composite film of the present invention is, for example, water, a liquid medicine, a resist used in a field (for example, a liquid crystal, a semiconductor manufacturing process, a pharmaceutical process, etc.) in which removal of fine particles of 10 nm or less, viruses, molecular size foreign substances, etc. It can also be suitably used for the purification of liquids such as solutions, other chemicals and solvents.

Claims (12)

A composite membrane having a porous support layer and a layer having a semipermeable membrane performance on the porous support layer,
The porous support layer is a flat polyketone porous membrane, and the following conditions (1) and (2):
(1) The proportion of holes having an equivalent circle diameter of 1 μm or more is less than 30%, and (2) the film thickness is 100 μm or more,
The composite membrane as defined above.   The layer having the performance of a semipermeable membrane is at least one selected from a cellulose acetate membrane, a polyamide membrane, a polyvinyl alcohol / polypiperazine amide composite membrane, a sulfonated polyether sulfone membrane, a polypiperazine amide membrane, and a polyimide membrane. The composite membrane of claim 1, which is a thin film layer comprising.   The composite membrane according to claim 1, wherein the maximum pore diameter of the polyketone porous membrane is 50 nm or more and 2 μm or less.   The polyketone porous membrane,
    Carbon monoxide,
    An olefin selected from chain olefins, alkenyl aromatic compounds, cyclic olefins, halogenated alkenes, acrylic esters, and vinyl acetate
Including a polyketone that is a copolymer of
The composite membrane according to any one of claims 1 to 3.   The polyketone has the following formula (2):
    -CH _Two -CH _Two -C (= O)-(2)
The composite membrane according to claim 4, comprising a 1-oxotrimethylene repeating unit represented by:   A forward osmosis treatment system comprising the composite membrane according to any one of claims 1 to 5.   A reverse osmosis treatment system comprising the composite membrane according to any one of claims 1 to 5.   A filtration system comprising the composite membrane according to any one of claims 1 to 5.   A method for producing water, characterized by using the system according to any one of claims 6 to 8.   A method for purifying an organic compound, which comprises using the system according to any one of claims 6 to 8.   A method for concentrating a water-containing substance, which comprises using the system according to any one of claims 6 to 8.   A power generation method using the forward osmosis treatment system according to claim 6.