JPWO2016167267A1 - Hollow fiber type semipermeable membrane, hollow fiber membrane module, and forward osmosis water treatment method - Google Patents

Abstract

A hollow fiber type semipermeable membrane characterized by having an inner diameter of more than 250 μm and not more than 700 μm. Even when a high-viscosity draw solution is allowed to flow in the hollow portion of the hollow fiber type semipermeable membrane, it is possible to suppress a decrease in the efficiency of the forward osmosis water treatment.

Description

  The present invention relates to a hollow fiber type semipermeable membrane, a hollow fiber membrane module including the hollow fiber type semipermeable membrane, and a forward osmosis water treatment method using the hollow fiber type semipermeable membrane.

  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 a reverse osmosis (RO) process is conventionally known. The reverse osmosis step is a step of moving water from a high concentration treatment target water to a low concentration solution side by applying artificially strong pressure, contrary to normal osmosis.

  However, since the reverse osmosis process requires a strong pressure, the energy consumption is extremely high and the energy efficiency is low. Therefore, in recent years, in order to increase the energy efficiency of water treatment, a forward osmosis water treatment system using a forward osmosis phenomenon that does not require artificial pressure has been proposed. For example, International Publication No. 2013/118859 (Patent Document 1) discloses a forward osmosis water treatment system using a hollow fiber type semipermeable membrane.

  Various draw solutions used 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

  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 Literature 1, the hollow fiber type semipermeable membrane has a large pressure loss. There was a problem that the flow rate required to maintain a sufficient effective osmotic pressure difference between inside and outside could not be ensured, and the efficiency of forward osmosis water treatment was reduced.

  In view of the above problems, the present invention provides a hollow fiber type semipermeable membrane capable of suppressing a decrease in the efficiency of forward osmosis water treatment even when a high-viscosity draw solution is allowed to flow through the hollow portion of the hollow fiber type semipermeable membrane. An object of the present invention is to provide a hollow fiber membrane module and a forward osmosis water treatment method.

[1] A hollow fiber type semipermeable membrane characterized by having an inner diameter of more than 250 μm and not more than 700 μm.
[2] The hollow fiber type semipermeable membrane according to [1], which is made of a material containing at least one of a cellulose resin, a polysulfone resin, and a polyamide resin.
[3] The hollow fiber type semipermeable membrane according to [2], wherein the cellulose resin is a cellulose acetate resin.
[4] The hollow fiber type semipermeable membrane according to [2] or [3], which is made of a material made of a cellulose resin.
[5] A hollow fiber membrane module comprising the hollow fiber type semipermeable membrane according to any one of [1] to [4].
[6] A forward osmosis water treatment method using the hollow fiber type semipermeable membrane according to [1],
By bringing water to be treated and water to be treated containing components other than water into contact with the outer peripheral surface of the hollow fiber type semipermeable membrane, and flowing a draw solution containing a draw solute in the hollow part of the hollow fiber type semipermeable membrane, A forward osmosis water treatment method comprising a permeation step of moving water contained in the water to be treated from the outer peripheral surface side into the hollow portion through the hollow fiber type semipermeable membrane.
[7] The forward osmosis water treatment method according to [6], wherein the draw solution has a viscosity of 0.15 Pa · s or more.
[8] The forward osmosis water treatment method according to [6] or [7], wherein in the infiltration step, a pressure at which the draw solution is flowed is 0.2 MPa or less.
[9] The forward osmosis water treatment method according to any one of [6] to [8], further including a separation step of separating the draw solute contained in the draw solution from water after the infiltration step.

  ADVANTAGE OF THE INVENTION According to this invention, even when flowing a highly viscous draw solution in the hollow part of a hollow fiber type semipermeable membrane, the hollow fiber type semipermeable membrane and hollow fiber membrane module which can suppress that the efficiency of forward osmosis water treatment falls. And a forward osmosis water treatment method can be provided.

6 is a graph showing the relationship between the amount of water produced and the inner diameter of a hollow fiber type semipermeable membrane when the viscosity η of the draw solution is 0.3 Pa · s (corresponding to Table 5). When the viscosity η of the draw solution is 0.126, 0.239, 0.330, 0.600 Pa · s (corresponding to Tables 3, 4, 6, 7), the amount of water produced and the inner diameter of the hollow fiber type semipermeable membrane It is a graph which shows the relationship. 6 is a graph showing the relationship between the amount of water produced and the inner diameter of a hollow fiber type semipermeable membrane when the viscosity η of the draw solution is 0.600 Pa · s (corresponding to Table 7). It is a graph which shows the relationship between the amount of water production and the internal diameter of a hollow fiber type semipermeable membrane about the case where a draw solution is salt water. It is a schematic diagram which shows an example of the hollow fiber membrane module of this invention.

(Hollow fiber type semipermeable membrane)
The hollow fiber type semipermeable membrane of the present invention has an inner diameter of more than 250 μm and 700 μm or less. The inner diameter is preferably more than 250 μm and not more than 650 μm, more preferably more than 250 μm and not more than 600 μm, still more preferably not more than 500 μm.

  In general, when the flow rate of the draw solution flowing through the hollow portion of the hollow fiber type semipermeable membrane decreases, the amount of water that permeates to the draw solution side while the draw solution flows through 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.

  However, according to the present invention, since the pressure loss due to the hollow fiber type semipermeable membrane is reduced by setting the inner diameter of the hollow fiber type semipermeable membrane to be in the range of more than 250 μm to 700 μm or less, the flow rate of the draw solution flowing in the hollow portion Can be more. Thereby, it is possible to secure a flow rate necessary to maintain a sufficient effective osmotic pressure difference inside and outside the hollow fiber type semipermeable membrane, and even when flowing a high viscosity draw solution into the hollow part of the hollow fiber type semipermeable membrane, It can suppress that the efficiency of forward osmosis water treatment falls.

  Although it does not specifically limit as a material which comprises a hollow fiber type semipermeable membrane, For example, a cellulose resin, a polysulfone resin, a polyamide resin etc. are mentioned. The hollow fiber type semipermeable membrane is preferably composed of a material containing at least one of a cellulose resin and a 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 polysulfone resin is preferably a polyethersulfone resin. The polyethersulfone resin is preferably a sulfonated polyethersulfone.

  As an example of a specific hollow fiber type semipermeable membrane, a membrane having a single layer structure, which is entirely composed of a cellulosic resin, can be mentioned. 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.

  As another example of a specific hollow fiber type semipermeable membrane, 2 having a dense layer made of a polyphenylene resin (for example, sulfonated polyethersulfone) on the outer peripheral surface of a support layer (for example, a layer made of polyphenylene oxide) A film having a layer structure may be mentioned. Another example includes a two-layered film having a dense layer made of a polyamide resin on the outer peripheral surface of a support layer (for example, a layer made of polysulfone or polyethersulfone).

  The thickness of the dense layer (separation active layer) is preferably 0.1 to 7 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 6 μm or less, and further preferably 5 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 0.5 μm or more, and further preferably 1 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. Moreover, the thickness of the whole membrane of a hollow fiber type semipermeable membrane becomes like this. Preferably it is 50-200 micrometers, More preferably, it is 60-170 micrometers. The film thickness can be calculated by (outer diameter−inner diameter) / 2. Further, the hollow ratio [(inner diameter / outer diameter) ² × 100 (%)] of the hollow fiber type semipermeable membrane is preferably 30 to 60%, more preferably 35 to 55%. 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.

  Although the length of a hollow fiber type semipermeable membrane is not specifically limited, Preferably it is 15-400 cm, More preferably, it is 20-350 cm.

  The hollow fiber type semipermeable membrane preferably has a pore diameter of 100 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), a limit What is called an outer filtration membrane (UF membrane: Ultrafiltration Membrane) is mentioned.

  Usually, the pore size of the RO membrane and the FO membrane is about 2 nm or less, and the pore size of the UF membrane is about 2 to 100 nm. The NF membrane has a relatively low rejection 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 module)
Moreover, this invention relates also to the hollow fiber membrane module provided with said hollow fiber type semipermeable membrane. As a method for incorporating the hollow fiber type semipermeable membrane into the hollow fiber type semipermeable membrane module, there are conventionally known methods. For example, in Japanese Patent No. 441486, Japanese Patent No. 4277147, Japanese Patent No. 3591618, Japanese Patent No. 3008886, etc. Have been described. Specifically, for example, 45 to 90 hollow fiber type semipermeable membranes are collected to form one hollow fiber type semipermeable membrane assembly, and a plurality of the hollow fiber type semipermeable membrane assemblies are arranged side by side to form a flat hollow shape. As a thread-type semipermeable membrane bundle, it is wound while traversing a core tube having a large number of holes. The winding angle at this time is 5 to 60 degrees, and the winding body is wound up so that the crossing portion is formed on the peripheral surface at a specific position. Next, after bonding both ends of the wound body, only one side or both sides are cut to form a hollow fiber opening to form a hollow fiber type separation membrane element. The obtained hollow fiber type separation membrane element 1 is inserted into the pressure vessel 2 to assemble the hollow fiber type semipermeable membrane module 3 (FIG. 5).

(Normal osmosis water treatment method)
The present invention also relates to a forward osmosis water treatment method using the hollow fiber type semipermeable membrane. The forward osmosis water treatment method of the present invention is a method of separating and collecting water from the water to be treated by forward osmosis using the hollow fiber type semipermeable membrane.

  The water to be treated is a liquid containing water and components other than water. Examples of water to be treated include seawater, river water, lake water, and industrial wastewater. In addition, when processing target water is a solution with high salt concentration, such as seawater, the evaporation residue density | concentration (TDS) of processing target water becomes like this. Preferably it is 0.7-14 mass%, More preferably, 1.5- It is 10 mass%, More preferably, it is 3-8 mass%.

  In the forward osmosis water treatment method of the present invention, the water to be treated (liquid containing water and a component other than water) is brought into contact with the outer peripheral surface of the hollow fiber type semipermeable membrane, and the hollow fiber type semipermeable membrane is placed in the hollow portion. By flowing a draw solution (DS) containing a draw solute, a permeation (forward osmosis) step of moving (permeating, permeating) the water contained in the water to be treated from the outer peripheral surface side into the hollow portion through the hollow fiber type semipermeable membrane. Including.

  In addition, said hollow fiber type semipermeable membrane module can be used suitably for the forward osmosis water processing method of this invention. Here, for example, the treatment target water can be brought into contact with the outer peripheral surface of the hollow fiber type semipermeable membrane by flowing the treatment target water outside the hollow fiber type semipermeable membrane in the hollow fiber membrane module as described above. it can.

  The viscosity of the draw solution is preferably 0.15 Pa · s or more, more preferably 0.20 Pa · s or more. When such a highly viscous solution is used as the draw solution, the hollow fiber type semipermeable membrane of the present invention is useful because the efficiency of the forward osmosis treatment is particularly likely to decrease.

  The osmotic pressure of the draw solution is preferably 0.5 to 10 MPa, more preferably 1 to 7 MPa, and further preferably 2 to 6 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.

  The temperature-responsive polymer includes a lower critical solution temperature (LCST) type and an 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 a high temperature, 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 examples of the temperature-responsive polymer include a polyvinyl ether polymer, a polyvinyl acetate polymer, and a (meth) acrylic acid polymer.

  When the hollow fiber type semipermeable membrane is used as the forward osmosis membrane as in the forward osmosis water treatment method of the present invention, the hollow fiber type from the viewpoint that the pressure resistance of the hollow fiber type semipermeable membrane or the high pressure pump is not required. The pressure of the fluid flowing in the hollow part of the semipermeable membrane is desirably 0.2 MPa or less. Therefore, in the infiltration step, the pressure for flowing the draw solution is preferably 0.2 MPa or less, more preferably 0.15 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.

  The forward osmosis water treatment method of the present invention preferably further includes a separation step of separating the draw solute contained in the draw solution from the water after the osmosis step.

  For example, when the draw solute is a temperature-responsive polymer, the draw solution is contained in the draw solution by flowing into the chamber separate from the hollow fiber membrane module and changing the temperature of the draw solution in the chamber. The draw solute can be separated from the water. 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. Moreover, the draw solute after collection can be easily reused (re-dissolved in a draw solution or the like).

  The forward osmosis water treatment method of the present invention preferably further includes a recovery step of recovering the draw solute separated from the water. The draw solute can be collected using, for example, a membrane separator, a centrifugal separator, a sedimentation separator, or the like. By recovering the water remaining after the draw solute recovery step, water that is the target of the water treatment method can be obtained. The drawing process for drawing solutes may be repeated in multiple stages so that pure water is obtained. After the drawing process for drawing solutes, a process for further improving the quality of the obtained water may be performed.

  The forward osmosis water treatment method of the present invention may further include a reuse step of re-dissolving the draw solute recovered in the recovery step in the draw solution.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to these examples.

(Production Example 1 of Hollow Fiber Type Semipermeable Membrane: -FO Membrane-)
Cellulose triacetate (CTA, Daicel Chemical Industries, LT35) 41% by mass, N-methyl-2-pyrrolidone (NMP, Mitsubishi Chemical) 49.9% by mass, ethylene glycol (EG, Mitsubishi Chemical) 8.8% by mass % And benzoic acid (Nacalai Tesque) 0.3% by mass were uniformly dissolved at 180 ° C. to obtain a film-forming stock solution. The obtained film-forming stock solution was degassed under reduced pressure, and then discharged from an arc-type (three-division) nozzle into a space cut off from the outside air at 163 ° C. After passing through a space time of 0.3 seconds, NMP / EG / It was immersed in a 12 ° C. coagulation bath consisting of water = 4.25 / 0.75 / 95. Subsequently, the hollow fiber type semipermeable membrane was washed and shaken off in a wet state. The obtained hollow fiber type semipermeable membrane was immersed in water at 75 ° C. and annealed for 40 minutes. Then, the immersion process for 5 minutes was implemented at 35,000 mg / L saline at about 25 degreeC.

(Production Example 2 of Hollow Fiber Type Semipermeable Membrane -RO Membrane-)
After purifying the copolyamide obtained by low temperature solution polymerization method from terephthalic acid dichloride, 70 mol% 4,4'-diaminodiphenylsulfone and 30 mol% piperazine, 36 parts by weight of this was added 4 parts by weight of CaCl ₂ (into the polymer). And a dimethylacetamide solution containing 3.6 parts by weight of diglycerin (relative to the polymer) at 80 ° C. to obtain a film-forming solution. After defoaming this solution, it was discharged from a three-split nozzle, immersed in a coagulation liquid cooled to 4-6 ° C. through an aerial traveling part, and a hollow fiber type semipermeable membrane was obtained. Next, the obtained hollow fiber type semipermeable membrane was washed with water and then heat-treated at 75 to 85 ° C. for 30 minutes.

(Production Example 3 of Hollow Fiber Semipermeable Membrane -NF Membrane-)
(Preparation of porous support membrane)
As a polymer for the porous support membrane, polyphenylene ether PX100L (hereinafter abbreviated as PPE) manufactured by Mitsubishi Engineering Plastics Co., Ltd. was prepared. N-methyl-2-pyrrolidone (hereinafter abbreviated as NMP) was added and dissolved at 140 ° C. so that the PPE would be 30% by mass to obtain a uniform film forming stock solution. Subsequently, while keeping the film forming stock solution at a temperature of 75 ° C., a 70% by mass NMP aqueous solution is extruded and molded as an inner liquid simultaneously from a double cylindrical tube nozzle while being extruded in a hollow shape. After performing the drying treatment, the substrate was immersed in a coagulation bath at 40 ° C. filled with a 35 mass% NMP aqueous solution to produce a PPE porous support membrane, and then washed with water. The porous support membrane that had been subjected to the water washing treatment was immersed in a 50% by mass glycerin aqueous solution, dried at 40 ° C., and wound around a winder.

(Production of composite film)
3,3'-disulfo-4,4'-dichlorodiphenylsulfone disodium salt 15.00 g, 2,6-dichlorobenzonitrile 29.76 g, 4,4'-biphenol 37.91 g, potassium carbonate 30.95 g Weighed into a 1000 mL four-necked flask equipped with a cooling reflux tube and flushed with nitrogen at 0.5 L / min. 263 mL of NMP was added, put into an oil bath, stirred at 150 ° C. for 30 minutes, then heated to 210 ° C. and reacted for 12 hours. After standing to cool, the polymerization reaction solution was precipitated in water into strands. The obtained polymer was washed 6 times with normal temperature water and vacuum dried at 110 ° C. to obtain a sulfonated polyarylene ether (hereinafter abbreviated as SPAE). As a result of measuring the degree of sulfonation of this SPAE, the degree of sulfonation was 15.0%. Dimethyl sulfoxide solvent was added to the obtained SPAE and dissolved while stirring at room temperature to obtain a coating solution having a concentration of 3% by mass. After passing the PPE porous support membrane through the coating solution, it was dried at 115 ° C. and wound around a winder.

(Examples 1 to 4 and Comparative Examples 1 and 2)
As Examples 1 to 4 and Comparative Examples 1 and 2, six types of hollow fiber membrane modules (virtual modules) with different inner diameters filled with the hollow fiber type semipermeable membrane described in Production Example 1 were assumed. The hollow fiber type semipermeable membrane is classified as a FO membrane having a dense layer thickness of about 2 μm, a pressure differential water permeability of 150 (L / m ² / day), and a pressure differential salt removal rate of 99.6%. used.

  The pressure differential water permeability and the pressure differential salt removal rate are, for example, parameters of a hollow fiber type semipermeable membrane measured as follows.

(Pressure difference permeability)
After hollow fiber type semipermeable membranes were bundled and inserted into a plastic sleeve, a thermosetting resin was injected into the sleeve, cured and sealed. By cutting the end of a hollow fiber type semipermeable membrane cured with a thermosetting resin, an opening surface of the hollow fiber type semipermeable membrane is obtained, and the membrane area on the basis of the outer diameter is about 0.1 m ² A module was produced. This evaluation module was connected to a membrane performance testing device consisting of a feed water tank and a pump, and the performance was evaluated. Specifically, a supply aqueous solution having a sodium chloride concentration of 1500 mg / L is filtered from the outside to the inside of the hollow fiber type semipermeable membrane at 25 ° C. and a pressure of 1.5 MPa, and is operated for 1 hour. Thereafter, the membrane permeated water was collected from the opening surface of the hollow fiber type semipermeable membrane, and the weight of the permeated water was measured with an electronic balance (Shimadzu Corporation LIBROR EB-3200D). The pressure differential permeability (FR) is expressed by the following formula:
FR [L / m ² / day] = weight of permeate [L] / outer diameter reference membrane area [m ² ] / collection time [min] × (60 [min] × 24 [hour])
It is calculated from.

(Pressure difference salt removal rate)
The sodium chloride concentration is measured using a conductivity meter (Toa DKK Corporation CM-25R) with respect to the membrane permeated water collected in the water permeability measurement and the sodium chloride concentration 1500 mg / L aqueous solution used in the same water permeability measurement. . Pressure differential salt removal rate is the following formula:
Pressure difference salt removal rate [%] = (1-membrane permeated water salt concentration [mg / L] / feed aqueous solution salt concentration [mg / L]) × 100
It is calculated from.

  The inner diameter, outer diameter, hollow ratio, membrane area and membrane volume of the hollow fiber type semipermeable membrane were as shown in Table 1. Each parameter was set so that the hollow rate and membrane volume of the hollow fiber type semipermeable membrane were substantially constant.

  The effective length of the hollow fiber type semipermeable membrane filled in the virtual module was 56 cm, the adhesion length was 7 cm, and the inner diameter of the virtual module was 75 mm. Further, the number (filling number) of hollow fiber type semipermeable membranes filled in the virtual module was set as shown in Table 1 so that the filling rate of the virtual module was 50%.

In the above, the hollow ratio is (inner diameter / outer diameter) ² × 100. The membrane area (outer diameter reference) is outer diameter × π × (effective length) × number of fillings. The membrane volume is π (outer diameter / 2) ² × (effective length) × number of fillings−π (inner diameter / 2) ² × (effective length) × number of fillings. The filling rate is [π (outer diameter / 2) ² × (number of fillings)] / [π (module inner diameter / 2) ² ].

(Draw solution viscosity measurement)
0, 20, 40, 60, and 80 wt% aqueous solution of Pluronic (Pluronic 25R2: manufactured by ADEKA) was stabilized at 25 ° C. in a thermostatic bath. Thereafter, the viscosity of each aqueous solution was measured using a B-type viscometer (product name: TVB-10 viscometer, manufactured by Toki Sangyo, used rotor: H1, measurement rotation speed: 100 rpm). The measured value after 1 minute from the start of operation of the viscometer was read.

(Simulation calculation of water permeability etc.)
About the virtual module of the said Example and comparative example, characteristic values, such as a water permeability, were calculated | required by calculation. In addition, about the assumption module of the said Example and comparative example, RO water (tap water was pre-processed and reverse osmosis-treated as feed solution (process target water) at the temperature of 25 degreeC outside the hollow fiber type semipermeable membrane of a module. The simulation calculation was performed on the assumption that a steady state was reached by flowing a draw solution (DS) at a pressure of 0.1 MPa into the hollow part of the hollow fiber type semipermeable membrane.

  Tables 3 to 7 show the calculation results when the concentration of the draw solute of the draw solution (assuming Pluronic 25R2 (made by ADEKA) is 61, 77, 83, 85 or 100 (solute only) mass%. The viscosity of each draw solution is 126, 239, 300, 330, 600 cP (centipoise) [0.126, 0.239, 0.300, 0.330, 0.600 Pa · s] in the same order as described above. Met.

  Thereafter, for DS, the concentration at the inlet of the hollow portion of the hollow fiber type semipermeable membrane (DS inlet concentration) and the concentration at the outlet (DS outlet concentration), the virtual module (inlet of the hollow portion of the hollow fiber type semipermeable membrane) The total flow rate of the draw solution flowing into the side) (DS inlet flow rate) and the total flow rate of the draw solution flowing out of the virtual module (the outlet side of the hollow part of the hollow fiber type semipermeable membrane) (DS outlet flow rate) are as follows: The calculation method was used. In each table, the ratio of the DS inlet flow rate based on the value of Comparative Example 2 is also shown.

[Method of calculation]
Assuming the above parameters (pressure of draw solution: 0.1 MPa, pressure of feed solution: 0 Pa, temperature: 25 ° C., and parameters shown in Table 1), DS inlet flow rate, DS outlet flow rate are input. The calculation shown in Tables 3 to 7 was carried out using a calculation program for calculating the DS outlet concentration and the total amount of water permeated through the hollow fiber type semipermeable membrane (ΔV). In these calculations, the virtual module (hollow fiber type semipermeable membrane) was divided into equal minute sections in the flow direction, and the material balance in each section was calculated.

Specifically, using the DS inlet concentration and the DS inlet flow rate, the amount of water permeating through the hollow fiber type semipermeable membrane in the first section of the virtual module (the section on the most inlet side) is expressed as A ′ value (cm ³ / Cm ² / s / (kgf / cm ² )) (assuming constant value) × membrane area (cm ² ) × 60 × [effective pressure (hydrostatic pressure) −effective osmotic pressure] (kgf / cm ² ) Calculate the outlet concentration and outlet flow rate of DS in the first interval. By repeating the same calculation sequentially from the inlet side to the outlet side of the virtual module as the outlet side concentration and outlet side flow rate of the first section as the DS inlet side concentration and inlet side flow rate of the next section, the final calculation is performed. The DS outlet concentration and DS outlet flow rate of a typical virtual module (hollow fiber type semipermeable membrane) are calculated. The total amount of water that permeated through the hollow fiber type semipermeable membrane in each section is the total amount of water (ΔV) that permeated through the hollow fiber type semipermeable membrane in the virtual module, and [DS outlet flow rate−DS inlet flow rate] ].

Further, the A ′ value (water permeability performance) was calculated from the following formula using the film evaluation results (Table 2) using the draw solutions having the viscosities and concentrations shown in Table 2. However, in the calculations shown in Tables 3 to 7, among the three A ′ values shown in Table 2, the A ′ values in which the viscosities shown in Table 2 are close to those in Tables 3 to 7 were substituted. However, when the viscosity was 0.300 or more, 2.6 × 10 ⁻⁷ was substituted.

A ′ value (cm ³ / cm ² / s / (kgf / cm ² )) = amount of water permeating the membrane: ΔV (cm ³ ) / membrane area (cm ² ) / time (s) / [effective pressure (hydrostatic pressure ) -Effective osmotic pressure] (kgf / cm < ² >)

  In addition, in each table | surface, ratio based on the value of the comparative example 2 is shown collectively about the water permeation amount ((DELTA) V). Moreover, the graph which made this ratio the vertical axis | shaft and made the internal axis of each Example and the comparative example the horizontal axis | shaft is shown in FIGS. 1 shows a case where the viscosity η of the draw solution is 0.3 Pa · s (corresponding to Table 5), and FIG. 2 shows a case where the viscosity η of the draw solution is 0.126, 0.239, 0.330, 0.600 Pa · s. In the case of s (corresponding to Tables 3, 4, 6 and 7), FIG. 3 shows the case where the viscosity η of the draw solution is 0.600 Pa · s (corresponding to Table 7). For comparison, FIG. 4 shows the calculation results when the draw solution was 7 mass% salt water (viscosity: about 0.1 Pa · s). In FIGS. 1 and 3, in order to refer to the increase in the flow rate of the draw solution, a graph of the ratio of the DS inlet flow rate based on Comparative Example 2 (right side of the vertical axis) is indicated by a dotted line.

  From the results shown in Tables 3 to 7 and FIGS. 1 to 3, even when a high-viscosity draw solution is allowed to flow through the hollow portion of the hollow fiber type semipermeable membrane, the inner diameter of the hollow fiber type semipermeable membrane is more than 250 μm and 700 μm or less. It is thought that it is possible to improve the efficiency (water permeability) of forward osmosis water treatment by making it into this range.

  However, in particular, the results of Table 3 (η = 0.126 Pa · s in FIG. 2) in which the viscosity of the draw solution is less than 0.150 Pa · s indicate that the viscosity of the draw solution is 0.150 Pa · s or more. Unlike the results, it shows the same tendency as the results when the draw solution shown in FIG. 3 is low-viscosity salt water. That is, when the viscosity of the draw solution is less than 0.150 Pa · s, the efficiency of the normal osmotic water treatment (water permeability) is improved by setting the inner diameter of the hollow fiber type semipermeable membrane to be in the range of more than 250 μm to 700 μm or less. It is presumed that it is difficult to obtain the effect. Therefore, it is considered that the hollow fiber type semipermeable membrane of the present invention is particularly useful when a solution having a high viscosity of 0.150 Pa · s or more is used as the draw solution.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. 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 separation membrane element, 2 pressure vessel, 3 hollow fiber type semipermeable membrane module.

Claims (9)

  A hollow fiber type semipermeable membrane characterized by having an inner diameter of more than 250 μm and not more than 700 μm.   The hollow fiber type semipermeable membrane according to claim 1, comprising a material containing at least one of a cellulose resin, a polysulfone resin and a polyamide resin.   The hollow fiber type semipermeable membrane according to claim 2, wherein the cellulose resin is a cellulose acetate resin.   The hollow fiber type semipermeable membrane according to claim 2 or 3, comprising a material comprising a cellulose resin.   A hollow fiber membrane module comprising the hollow fiber type semipermeable membrane according to any one of claims 1 to 4. A forward osmosis water treatment method using the hollow fiber type semipermeable membrane according to claim 1,
By bringing water to be treated and water to be treated containing components other than water into contact with the outer peripheral surface of the hollow fiber type semipermeable membrane, and flowing a draw solution containing a draw solute in the hollow part of the hollow fiber type semipermeable membrane, A forward osmosis water treatment method comprising a permeation step of moving water contained in the water to be treated from the outer peripheral surface side into the hollow portion through the hollow fiber type semipermeable membrane.   The forward osmosis water treatment method according to claim 6, wherein the draw solution has a viscosity of 0.15 Pa · s or more.   The forward osmosis water treatment method according to claim 6 or 7, wherein, in the infiltration step, a pressure at which the draw solution flows is 0.2 MPa or less.   The forward osmosis water treatment method according to any one of claims 6 to 8, further comprising a separation step of separating the draw solute contained in the draw solution from water after the infiltration step.

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