WO2016190166A1

WO2016190166A1 - Immersion-type hollow-fiber-membrane module, and forward-osmosis water treatment method in which same is used

Info

Publication number: WO2016190166A1
Application number: PCT/JP2016/064583
Authority: WO
Inventors: 崇人中尾; 綾乃檜垣; 昌男東; 北河　享
Original assignee: 東洋紡株式会社
Priority date: 2015-05-28
Filing date: 2016-05-17
Publication date: 2016-12-01
Also published as: JPWO2016190166A1; JP6477872B2

Abstract

An immersion-type hollow-fiber-membrane module provided with: hollow-fiber-membrane elements in which a plurality of linear hollow-fiber-type semipermeable membranes having hollow sections are laid parallel to each other at a prescribed spacing; a securing resin whereby the plurality of hollow-fiber-type semipermeable membranes are secured at the prescribed spacing at both ends of the hollow-fiber-membrane element; an inflow port that communicates with the hollow sections of the plurality of hollow-fiber-type semipermeable membranes at one end of the hollow-fiber-membrane element; and an outflow port that communicates with the hollow sections of the plurality of hollow-fiber-type semipermeable membranes at the other end of the hollow-fiber-membrane element. The plurality of hollow-fiber-type semipermeable membranes are exposed, and the material of the hollow-fiber-type semipermeable membranes includes a cellulose resin and/or a polysulfone resin.

Description

Immersion type hollow fiber membrane module and forward osmosis water treatment method using the same

The present invention relates to a submerged hollow fiber membrane module and a forward osmosis water treatment method using the same.

Forward osmosis (FO: forward osmosis) is a solution with high concentration (high osmotic pressure) in the low concentration (low osmotic pressure) treated water (feed solution) side through a semipermeable membrane (draw solution) It is a phenomenon that moves toward. On the other hand, in the field of water treatment, a water treatment method using reverse osmosis (RO) is conventionally known. Reverse osmosis is a phenomenon in which water moves from a high-concentration treatment target water to a low-concentration solution side through a semipermeable membrane, contrary to normal osmosis, by artificially applying high pressure to the treatment-target water. It is.

However, since reverse osmosis requires high pressure, energy consumption is extremely high and energy efficiency is low. Therefore, in recent years, a forward osmosis water treatment system using a forward osmosis phenomenon that does not need to be manually applied to increase the energy efficiency of water treatment has been proposed (for example, International Publication No. 2013/118859 ( Patent Document 1) etc.). Various draw solutions for use in the forward osmosis water treatment system are known. For example, JP-A-2014-512951 (Patent Document 2) discloses a polyglycol copolymer as a draw solution. It is disclosed to use a high viscosity solution.

International Publication No. 2013/118859 Special table 2014-512951 gazette Special table 2013-509298 gazette

When a high-viscosity draw solution is allowed to flow through an existing forward osmosis hollow fiber semipermeable membrane (inner diameter 50 to 250 μm) as described in Patent Document 1, the pressure loss is large, so the hollow fiber semipermeable membrane It is difficult to secure a flow rate necessary to maintain a sufficient effective osmotic pressure difference between the inside and outside, and the efficiency of forward osmosis water treatment tends to be reduced. For this reason, when a high-viscosity draw solution is allowed to flow through the hollow part of the hollow fiber type semipermeable membrane, the inner diameter is larger than the conventional one (for example, the inner diameter is more than 250 μm and more than 700 μm) in order to suppress a decrease in the efficiency of forward osmosis water treatment. It is considered desirable to use a hollow fiber type semipermeable membrane.

On the other hand, when a sealed hollow fiber membrane module in which a hollow fiber membrane element is accommodated in a housing is used for water to be treated containing a large amount of scale components (fouling is likely to occur), a hollow fiber type semipermeable membrane is used. However, the water recovery efficiency by the forward osmosis treatment tends to decrease. Therefore, an open-type hollow fiber membrane module (immersion-type hollow fiber membrane module) in which a hollow fiber membrane element (hollow fiber type semipermeable membrane) used in the membrane separation activated sludge method (MBR) is exposed is used as a water tank. There is a need to use a method of immersing in water to be treated in the (treatment tank). As a result, the scale component is concentrated on the surface of the hollow fiber type semipermeable membrane in a part of the housing due to stagnation in the flow of the water to be treated in a part of the housing like a sealed hollow fiber membrane module. This is because, since the adhesion is suppressed, clogging of the hollow fiber type semipermeable membrane can be suppressed with respect to the water to be treated containing a large amount of scale components.

Here, there are so-called straight type and crosswind type hollow fiber membrane modules. However, in the normal forward osmosis treatment using a sealed hollow fiber membrane module, there are many crosswind type hollow fiber membrane modules. It is used. In a sealed hollow fiber membrane module, radially outward from a core tube (a perforated pipe having a large number of holes) arranged at the radial center of a hollow fiber membrane element (bundle of hollow fiber type semipermeable membranes) When the water to be treated is flowed toward the surface, the cross-wind type hollow fiber membrane module is more likely to be uniformly diffused throughout the module than the straight type, and the treatment is performed by increasing the effective membrane area. This is because the efficiency is improved.

However, in the immersion forward osmosis method using an open-type hollow fiber membrane module, in such a cross-wind type hollow fiber membrane module, the water to be treated in the water tank is centered from the outside in the radial direction of the hollow fiber membrane element. There is a problem that the treatment efficiency is lowered due to the reduction of the effective membrane area. In particular, when using a hollow fiber type semipermeable membrane having a large inner diameter, it is necessary to increase the outer diameter of the hollow fiber membrane element in order to increase the effective membrane area and obtain a desired treatment efficiency. Such a problem becomes conspicuous because it becomes more difficult for the water to be treated to penetrate into the center side in the radial direction of the yarn membrane element.

In view of the above problems, the present invention allows a high-viscosity draw solution to flow into the hollow portion of a hollow fiber type semipermeable membrane against water to be treated containing a large amount of scale components in contact with the outside of the hollow fiber type semipermeable membrane. In the case where the forward osmosis water treatment is carried out, the immersion type hollow fiber membrane module capable of improving the efficiency of the forward osmosis water treatment while suppressing clogging of the hollow fiber type semipermeable membrane, and using the same It is an object of the present invention to provide an immersion type forward osmosis water treatment method.

[1]
A hollow fiber membrane element in which a plurality of linear hollow fiber type semipermeable membranes having a hollow portion are arranged in parallel at predetermined intervals;
A fixing resin for fixing the plurality of hollow fiber type semipermeable membranes at predetermined intervals at both ends of the hollow fiber membrane element;
An inflow port communicating with the hollow part of the plurality of hollow fiber type semipermeable membranes at one end of the hollow fiber membrane element, and the hollow part of the plurality of hollow fiber type semipermeable membranes at the other end of the hollow fiber membrane element And an outlet that communicates with
The plurality of hollow fiber type semipermeable membranes are exposed,
An immersion type hollow fiber membrane module for forward osmosis, wherein the material of the hollow fiber type semipermeable membrane is a material containing at least one of a cellulose resin and a sulfonated polysulfone resin.
[2]
The immersion type hollow fiber membrane module according to [1], wherein an inner diameter of the hollow fiber type semipermeable membrane is more than 250 μm and 700 μm or less.
[3]
The immersion type hollow fiber membrane module according to [1] or [2], wherein an outer diameter of the hollow fiber membrane element is 5 cm or more and 60 cm or less.
[4]
The end portion filling rate, which is the ratio of the total cross-sectional area of the outer diameter of the hollow fiber type semipermeable membrane to the area of the circle formed by the outer periphery of the hollow fiber membrane element, is 40% or more and 70% or less. ] The submerged hollow fiber membrane module according to any one of [3] to [3].
[5]
A forward osmosis water treatment method using the immersion type hollow fiber membrane module according to [1],
The immersion type hollow fiber membrane module is immersed in a treatment target water containing water in the treatment tank and components other than water, and the treatment target water is brought into contact with the outer peripheral surface of the hollow fiber type semipermeable membrane. In addition, by flowing a draw solution containing a draw solute into the hollow portion of the hollow fiber type semipermeable membrane, water contained in the water to be treated passes through the hollow fiber type semipermeable membrane from the outer peripheral surface side into the hollow portion. A forward osmosis water treatment method including a forward osmosis step for movement.

According to the present invention, forward osmosis water is obtained by flowing a high-viscosity draw solution into the hollow portion of the hollow fiber type semipermeable membrane with respect to the water to be treated containing a large amount of scale components in contact with the outside of the hollow fiber type semipermeable membrane. When carrying out the treatment, an immersion type hollow fiber membrane module capable of improving the efficiency of forward osmosis water treatment while suppressing clogging of the hollow fiber type semipermeable membrane, and an immersion type positive membrane using the same An immersion type hollow fiber membrane module capable of providing an osmotic water treatment method and an immersion type forward osmosis water treatment method using the same can be provided.

It is a partial permeation | transmission perspective view which shows schematically the structure of the immersion type hollow fiber membrane module in embodiment of this invention. It is a schematic diagram for demonstrating the forward osmosis processing method in embodiment of this invention.

(Hollow fiber type semipermeable membrane)
With reference to FIG. 1, the hollow fiber type semipermeable membrane 1 used for the immersion type hollow fiber membrane module 100 of this embodiment is a thread-like semipermeable membrane which has a hollow part. The hollow fiber type semipermeable membrane 1 used in the present embodiment for flowing the draw solution into the hollow part is a hollow fiber type semipermeable membrane having an opening at both ends and having openings that communicate with the hollow part at both ends. Is preferred.

The inner diameter (diameter of the cross section of the hollow portion) of the hollow fiber type semipermeable membrane 1 is preferably more than 250 μm and less than 700 μm, more preferably more than 250 μm and less than 650 μm, still more preferably more than 250 μm and less than 600 μm, most preferably more than 250 μm. 500 μm or less.

Generally, when the flow rate of the draw solution flowing in the hollow portion of the hollow fiber type semipermeable membrane 1 is reduced, the amount of water that permeates to the draw solution side while the draw solution flows in the hollow portion increases. As a result, the overall osmotic pressure of the draw solution flowing in the hollow portion is reduced, and the osmotic pressure difference between the draw solution and the water to be treated (feed solution) is reduced, so that the water recovery efficiency is lowered.

On the other hand, in the present embodiment, the pressure loss due to the hollow fiber type semipermeable membrane 1 is reduced by making the inner diameter of the hollow fiber type semipermeable membrane 1 in the range of more than 250 μm and 700 μm or less, which is larger than the conventional normal inner diameter. Therefore, the flow rate of the draw solution flowing in the hollow portion can be increased. As a result, a flow rate required to maintain a sufficient effective osmotic pressure difference between the inside and outside of the hollow fiber type semipermeable membrane 1 can be secured, and a highly viscous draw solution is allowed to flow in the hollow portion of the hollow fiber type semipermeable membrane 1. However, it can suppress that the efficiency of forward osmosis water treatment falls.

The material constituting the hollow fiber type semipermeable membrane 1 is not particularly limited, and examples thereof include cellulose resins, sulfonated polysulfone resins, polyamide resins, and the like. The hollow fiber type semipermeable membrane 1 is preferably made of a material containing at least one of a cellulose resin and a sulfonated polysulfone resin.

The cellulose resin is preferably a cellulose acetate resin. Cellulose acetate resin is resistant to chlorine, which is a bactericidal agent, and has a feature that it can suppress the growth of microorganisms. The cellulose acetate resin is preferably cellulose acetate, and more preferably cellulose triacetate from the viewpoint of durability.

The sulfonated polysulfone resin is preferably a sulfonated polyethersulfone resin.

As an example of a specific hollow fiber type semipermeable membrane, there is a membrane having a single layer structure which is entirely composed of a cellulose resin or a sulfonated polysulfone resin. However, the single-layer structure here does not need to be a uniform film as a whole, for example, as disclosed in Patent Document 1, a dense layer is provided in the vicinity of the outer peripheral surface, and this dense layer is substantially In particular, it is preferably a separation active layer that defines the pore diameter of the hollow fiber type semipermeable membrane.

Another example of a specific hollow fiber type semipermeable membrane is a membrane having a two-layer structure having a separation active layer on the outer peripheral surface of a support membrane having a pore size comparable to that of an ultrafiltration membrane. Although it does not specifically limit as a material which comprises a support membrane, Polysulfone, polyether sulfone, polyphenylene oxide, polyvinylidene fluoride, polyether ketone, polyimide, polybenzimidazole, polyester, etc. are mentioned. The material constituting the separation active layer is not particularly limited, and examples thereof include sulfonated polysulfone resin, polyamide resin, cellulose resin, and polyvinyl alcohol resin.

The thickness of the dense layer (separation active layer) is preferably 0.05 to 5 μm. It is preferable that the dense layer has a small thickness because water permeability resistance is small. For this reason, the thickness of the dense layer is more preferably 3 μm or less, and further preferably 1 μm or less. However, if the dense layer is too thin, potential defects in the membrane structure are likely to be manifested, and for example, it becomes difficult to suppress leakage of monovalent ions, or the durability of the membrane is reduced. Problems are likely to occur. For this reason, the thickness of the dense layer is more preferably 0.1 μm or more, and further preferably 0.3 μm or more.

The outer diameter of the hollow fiber type semipermeable membrane is preferably 300 to 1000 μm, more preferably 400 to 950 μm. The total thickness of the hollow fiber type semipermeable membrane is preferably 50 to 200 μm, more preferably 60 to 170 μm. The film thickness can be calculated by (outer diameter−inner diameter) / 2.

The hollow ratio [(inner diameter / outer diameter) ² × 100 (%)] of the hollow fiber type semipermeable membrane is preferably 24 to 51%. In addition, a hollow rate is a ratio of the area of the hollow part in the cross section of a hollow fiber type semipermeable membrane. When the hollow ratio is less than 24%, the water permeation resistance of the hollow fiber type semipermeable membrane is increased, which may cause a problem that desired treatment efficiency cannot be obtained. When the hollow ratio is more than 51%, the strength of the hollow fiber type semipermeable membrane may be insufficient and the hollow fiber type semipermeable membrane may be broken.

The effective length of the hollow fiber type semipermeable membrane is not particularly limited, but is preferably 0.3 to 3.0 m, more preferably 0.5 to 2.0 m. The effective length is the length of the hollow fiber type semipermeable membrane bundle having a function as a semipermeable membrane which is a portion excluding the fixed resin portion.

The diameter (pore diameter) of the plurality of fine pores of the hollow fiber type semipermeable membrane is preferably 2 nm or less. As such a hollow fiber type semipermeable membrane, for example, a reverse osmosis membrane (RO membrane: Reverse Osmosis Membrane), a forward osmosis membrane (FO membrane: Forward Osmosis Membrane), a nanofiltration membrane (NF membrane: Nanofiltration Membrane), and What is called.

Usually, the pore size of the RO membrane and the FO membrane is about 2 nm or less. The NF membrane has a relatively low blocking rate of ions and salts among the RO membrane, and the pore size of the NF membrane is usually about 1 to 2 nm.

(Hollow fiber membrane element)
The hollow fiber membrane element 10 of this embodiment is a hollow fiber membrane element called a straight type (as opposed to a crosswind type), and a plurality of linear hollow fiber type semipermeable membranes 1 having hollow portions are arranged in parallel. Are bundles of hollow fiber type semipermeable membranes 1 arranged at predetermined intervals.

In addition, the term “linear” as used herein means that a portion that is intentionally wound, bent, curved, or the like is excluded, and mathematical linearity is not required. That is, for example, the hollow fiber type semipermeable membrane 1 may be disposed in a loose state, and in that case, the hollow fiber type semipermeable membrane 1 may have a slight curvature.

Further, “with a predetermined interval” means that a plurality of hollow fiber type semipermeable membranes 1 need not be in contact with each other at least at both ends of the hollow fiber type semipermeable membrane 1. For example, when the hollow fiber type semipermeable membrane 1 is placed in a relaxed state, even if some of the hollow fiber type semipermeable membranes 1 are in contact with each other at portions other than both ends of the hollow fiber type semipermeable membrane 1. Good. Even in such a state, in the state immersed in the treatment target water in the treatment tank, the treatment target water flows between the plurality of hollow fiber type semipermeable membranes 1 due to the flow in the treatment tank or the like. Therefore, the effective membrane area of the hollow fiber type semipermeable membrane is not reduced.

In the immersion type forward osmosis water treatment method, when a cross-wind type hollow fiber membrane module is used, the water to be treated in the water tank hardly permeates from the outside in the radial direction of the hollow fiber membrane element to the center side. The processing efficiency tends to decrease due to the reduction of the effective membrane area. In particular, when using a hollow fiber type semipermeable membrane having a large inner diameter, it is necessary to increase the outer diameter of the hollow fiber membrane element in order to increase the effective membrane area and obtain a desired treatment efficiency. It becomes more difficult to penetrate the thread membrane element into the radial center.

On the other hand, in this embodiment, in the immersion type forward osmosis water treatment method, the treatment target water in the water tank is centered in the radial direction of the hollow fiber membrane element 10 by using a straight hollow fiber membrane module. Easy to reach to the side, processing efficiency is high.

The outer diameter of the hollow fiber membrane element 10 is preferably 5 cm or more and 60 cm or less. In the case of using a hollow fiber membrane element having a relatively large outer diameter in which the outer diameter of the hollow fiber membrane element 10 is in such a range, in particular, penetration of water to be treated into the radial center of the hollow fiber membrane element 10 Therefore, in order to increase the efficiency of the forward osmosis treatment, it is effective to use a straight hollow fiber membrane element as in this embodiment.

Further, the ratio of the total cross-sectional area of the outer diameter of the hollow fiber type semipermeable membrane 1 to the area of the circle formed by the outer periphery of the hollow fiber membrane element 10 (hollow fiber type semipermeable membrane bundle) (fixed resin end area) is the end. When the part filling rate is used, the end filling rate is preferably 40% or more and 70% or less. In the case of using a hollow fiber membrane element in which a plurality of hollow fiber type semipermeable membranes 1 are arranged at relatively narrow intervals, in which the end portion filling rate of the hollow fiber membrane element 10 is in such a range, in particular, the hollow fiber membrane element In order to increase the efficiency of forward osmosis treatment, it is effective to use a straight-type hollow fiber membrane element as in this embodiment. .

For the fixed resin end area, the diameter of a circle circumscribing a plurality of hollow fiber type semipermeable membranes located on the outermost periphery of the hollow fiber type semipermeable membrane bundle (hollow fiber membrane element) on the fixed resin end surface is measured using a caliper. And measure 5 points (maximum, large, medium, small, minimal). At this time, the hollow fiber type semipermeable membrane is excluded from a case where it is extremely off the circumferential portion. Using the average value of the diameters, the fixed resin end area (the area of a circle formed by the outer periphery of the hollow fiber membrane element) is calculated.

On the other hand, the cross-sectional area based on the outer diameter of each hollow fiber type semipermeable membrane is calculated. Multiply this by the number of yarns (hollow fiber type semipermeable membrane) contained in the end face of the fixed resin to obtain the area of the hollow fiber type semipermeable membrane part (see the following formula).

Hollow fiber type semipermeable membrane area = π × (outer diameter of hollow fiber type semipermeable membrane / 2) ² × number of hollow fiber type semipermeable membranes and hollow fiber type semipermeable membrane area with respect to the fixed resin end area The end filling rate (%), which is the ratio of
End filling ratio (%) = Hollow fiber type semipermeable membrane area / Fixed resin edge area × 100
Ask from.

(Immersion type hollow fiber membrane module)
Referring to FIG. 1, an immersion type hollow fiber membrane module 100 includes the straight type hollow fiber membrane element 10 (a bundle of hollow fiber type semipermeable membranes 1). Further, the immersion type hollow fiber membrane module 100 includes fixing

resins

21 and 22 for fixing the plurality of hollow fiber type semipermeable membranes 1 at predetermined intervals at both ends of the hollow fiber membrane element 10. In order to maintain the overall shape of the submerged hollow fiber membrane module 100, the two fixing

resins

21 and 22 may be connected to each other by a support (not shown).

The fixing resin 21 is connected to a distribution chamber 21 a having an internal space communicating with the hollow portions of the plurality of hollow fiber type semipermeable membranes 1 through an opening at one end of the hollow fiber type semipermeable membrane 1. The distribution chamber 21a has an inlet 21b that communicates with the internal space. Therefore, the inflow port 21 b communicates with the hollow portions of the plurality of hollow fiber type semipermeable membranes 1 at one end of the hollow fiber membrane element 10.

Further, the fixing resin 22 is connected to an assembly chamber 22 a having an internal space communicating with the hollow portions of the plurality of hollow fiber type semipermeable membranes 1 through the opening at the other end of the hollow fiber type semipermeable membrane 1. . The collecting chamber 22a has an outlet 22b communicating with the internal space. Accordingly, the outlet 22 b communicates with the hollow portions of the plurality of hollow fiber type semipermeable membranes 1 at the other end of the hollow fiber membrane element 10.

As shown in FIG. 1, in the immersion type hollow fiber membrane module 100 of the present embodiment, a plurality of hollow fiber type semipermeable membranes 1 are exposed. The plurality of hollow fiber type semipermeable membranes 1 only need to have at least a part of the outer surface exposed. In FIG. The part is covered with resin and not exposed, but the other part of the hollow fiber type semipermeable membrane 1 is exposed. In FIG. 1, the fixing resins 21 and 22, the distribution chamber 21 a, and the collecting chamber 22 a are drawn through, but it is not necessarily transparent.

Such a straight type immersion type hollow fiber membrane module can be manufactured by a conventionally known method, for example, by a method as disclosed in JP-A-10-192661.

(Normal osmosis water treatment method)
The forward osmosis water treatment method of this embodiment is a method of separating and collecting water from the treatment target water by forward osmosis using the above-described immersion type hollow fiber membrane module.

Note that the water to be treated is a liquid containing water and components other than water. Examples of the water to be treated include salt water such as sea water, river water, lake water, and industrial waste water. When the treatment target water is high-concentration salt water, the evaporation residue concentration (TDS) of the treatment target water is preferably 20% by mass or less, more preferably 15% by mass or less.

Referring to FIG. 2, in the forward osmosis water treatment method of the present embodiment, the immersion type hollow fiber membrane module 100 is immersed in the water to be treated (FS) supplied into the treatment tank 3. Thereby, water to be treated is brought into contact with the outer peripheral surfaces of the plurality of hollow fiber type semipermeable membranes 1. In this state, the pump 4 causes a draw solution (DS) containing a draw solute to flow into the hollow portion of the hollow fiber type semipermeable membrane 1, thereby allowing water contained in the water to be treated to pass through the hollow fiber type semipermeable membrane 1 to the outer periphery. Move from the surface side into the hollow part (draw solution side).

The draw solution diluted in the hollow portion of the hollow fiber type semipermeable membrane 1 by the forward osmosis step is sent to the reconcentration step by the pump 4. In the reconcentration step, a part of the water is recovered from the draw solution, and the draw solution concentrated thereby is sent to the hollow fiber type semipermeable membrane 1 and again subjected to the forward osmosis step.

In the forward osmosis treatment method of this embodiment, as shown in FIG. 2, bubbles 5 are introduced into the water to be treated by an air outlet (not shown) provided at the top of the bottom wall of the treatment tank 3. It may be generated. Accordingly, the bubbles 5 are brought into contact with the plurality of hollow fiber type semipermeable membranes 1, thereby suppressing the scale from adhering to the outer surface of the hollow fiber type semipermeable membranes 1. Clogging can be prevented.

The viscosity of the draw solution is preferably 0.10 Pa · s or more, more preferably 0.15 Pa · s or more. When such a highly viscous solution is used as the draw solution, it is effective to use the hollow fiber type semipermeable membrane of the present embodiment having an inner diameter larger than that of the conventional because the efficiency of the forward osmosis treatment is particularly likely to decrease. is there.

The osmotic pressure of the draw solution is preferably 0.5 to 20 MPa, although it depends on the molecular weight of the solute.
Examples of the draw solute include saccharides, proteins, and synthetic polymers. Stimulation-responsive polymers are preferable from the viewpoint of easy recovery and regeneration. Examples of the stimulus responsive polymer include a temperature responsive polymer, a pH responsive polymer, a photoresponsive polymer, and a magnetic responsive polymer.

The temperature-responsive polymer is a polymer having a characteristic (temperature responsiveness) in which hydrophilicity changes with a predetermined temperature as a critical point. In other words, the temperature responsiveness is a characteristic that becomes hydrophilic or hydrophobic depending on the temperature. Here, the change in hydrophilicity is preferably reversible. In this case, the temperature-responsive polymer can be dissolved in water or phase-separated from water by adjusting the temperature.

The temperature-responsive polymer is a polymer composed of a plurality of structural units derived from a monomer, and preferably has a hydrophilic group in the side chain.

There are two types of temperature-responsive polymers: the lower critical solution temperature (LCST) type and the upper critical solution temperature (UCST) type. In the LCST type, when a polymer dissolved in low-temperature water reaches a temperature higher than the temperature inherent to the polymer (LCST), it is phase-separated from water. On the other hand, in the UCST type, when the polymer dissolved in high-temperature water falls below the temperature inherent to the polymer (UCST), it is phase-separated from water (Sugihara et al., “Environment-responsive polymer tissue "Development to", SEN'I GAKKAISHI (Fiber and Industry), Vol. 62, No. 8, 2006). In the case of using a material that easily deteriorates at a high temperature, it is desirable that the semi-permeable membrane is in contact with the semi-permeable membrane by a temperature-responsive polymer dissolved in low-temperature water. The conducting polymer is preferably LCST type. In addition, in the case of using a semi-permeable membrane made of a material that does not easily deteriorate at high temperatures, a UCST type can be used in addition to the LCST type.

Examples of the hydrophilic group include a hydroxyl group, a carboxyl group, an acetyl group, an aldehyde group, an ether bond, and an ester bond. The hydrophilic group is preferably at least one selected from these.

The temperature-responsive polymer preferably has at least one hydrophilic group in at least some or all of the structural units. Moreover, the temperature-responsive polymer may have a hydrophobic group in some structural units while having a hydrophilic group. In addition, it is considered that the balance between the hydrophilic group and the hydrophobic group contained in the molecule is important for the temperature responsive polymer to have temperature responsiveness.

Specific temperature-responsive polymers include, for example, polyvinyl ether polymers, polyvinyl acetate polymers, (meth) acrylic acid polymers, and the like.

In the case of using a hollow fiber type semipermeable membrane as the forward osmosis membrane as in the forward osmosis water treatment method of the present embodiment, the hollow fiber type from the viewpoint that the pressure resistance of the hollow fiber type semipermeable membrane and the high pressure pump is not required. The pressure of the fluid flowing in the hollow portion of the mold semipermeable membrane is desirably 0.5 MPa or less. Therefore, in the forward osmosis step, the pressure for flowing the draw solution is preferably 0.5 MPa or less, more preferably 0.2 MPa or less. On the other hand, from the viewpoint of securing a flow rate necessary to maintain a sufficient effective osmotic pressure difference inside and outside the hollow fiber type semipermeable membrane, the pressure for flowing the draw solution is preferably 0.01 MPa or more, more preferably Is 0.05 MPa or more.

In the above re-concentration step, for example, when the draw solute is a temperature-responsive polymer, the draw solute contained in the draw solution can be separated from water by changing the temperature of the draw solution. In this case, the draw solute (temperature-responsive polymer) can be easily separated from the water and recovered simply by changing the temperature of the draw solution. In addition, since the draw solution concentrated by collecting water in this way is a solution having the same components as the original draw solution, the temperature is returned to the original, and the concentration is adjusted as necessary. It can be used as a draw solution in the forward osmosis process.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

1 hollow fiber type semipermeable membrane, 10 hollow fiber membrane element, 100 immersion type hollow fiber membrane module, 21, 22 fixing resin, 21a distribution chamber, 21b inlet, 22a collecting chamber, 22b outlet, 3 treatment tank, 4 pump 5, bubbles.

Claims

A hollow fiber membrane element in which a plurality of linear hollow fiber type semipermeable membranes having a hollow portion are arranged in parallel at predetermined intervals;
A fixing resin for fixing the plurality of hollow fiber type semipermeable membranes at predetermined intervals at both ends of the hollow fiber membrane element;
An inlet that communicates with the hollow portion of the plurality of hollow fiber membranes at one end of the hollow fiber membrane element, and a hollow portion of the plurality of hollow fiber membranes at the multiple ends of the hollow fiber membrane element. And an outflow port that communicates,
The plurality of hollow fiber type semipermeable membranes are exposed,
An immersion type hollow fiber membrane module for forward osmosis, wherein the material of the hollow fiber type semipermeable membrane is a material containing at least one of a cellulose resin and a sulfonated polysulfone resin.
The immersion type hollow fiber membrane module according to claim 1, wherein an inner diameter of the hollow fiber type semipermeable membrane is more than 250 µm and 700 µm or less.
The immersion type hollow fiber membrane module according to claim 1 or 2, wherein an outer diameter of the hollow fiber membrane element is 5 cm or more and 60 cm or less.
The end filling rate, which is the ratio of the total cross-sectional area of the outer diameter of the hollow fiber type semipermeable membrane to the area of a circle formed by the outer periphery of the hollow fiber membrane element, is 40% or more and 70% or less. 4. The immersion type hollow fiber membrane module according to any one of 1 to 3.
A forward osmosis water treatment method using the submerged hollow fiber membrane module according to claim 1,
The immersion type hollow fiber membrane module is immersed in a treatment target water containing water in the treatment tank and components other than water, and the treatment target water is brought into contact with the outer peripheral surface of the hollow fiber type semipermeable membrane. In addition, by flowing a draw solution containing a draw solute into the hollow portion of the hollow fiber type semipermeable membrane, water contained in the water to be treated passes through the hollow fiber type semipermeable membrane from the outer peripheral surface side into the hollow portion. A forward osmosis water treatment method including a forward osmosis step for movement.