JP7261328B2 - Tubular Separation Membrane and Tubular Separation Membrane Module - Google Patents

Description

The present disclosure relates to a tubular separation membrane, a tubular separation membrane module including the same, and a method for producing a tubular separation membrane.

Waste water discharged from factories in various fields may contain mineral oil, miscellaneous oil, wax, surfactant, suspended matter, and the like. As a method for treating such wastewater, a method using a tubular separation membrane is known.

Japanese Patent Application Laid-Open No. 2016-179420 describes an invention of a membrane separation method for oil-containing water in which an anionic surfactant is added to oil-containing water and then membrane separation is performed at a membrane surface linear velocity of 1 m / sec or more. Examples of filtration membranes include microfiltration (MF) membranes and ultrafiltration (UF) membranes, and it is described that internal pressure tubular membranes and spiral membranes are suitable.

Japanese Patent Application Laid-Open No. 2019-107645 discloses a wastewater treatment method in which water is recovered in wastewater treatment and only the finally dried solids are discarded or reused, and a treatment process using a tubular reverse osmosis (RO) membrane. (Claims). It is described that the material of the RO membrane is one or more selected from cellulose acetate, aromatic polyamide, and sulfonated polyethersulfone.

Japanese Unexamined Patent Application Publication No. 2019-107575 discloses an invention of a filtration apparatus including a water tank to be treated, a plurality of reverse osmosis membrane modules, and a filtered water tank (claims). As the reverse osmosis membrane module, a plurality of tubular membrane elements 60 of reverse osmosis membranes are accommodated in a tubular outer casing 50 (FIGS. 3 and 4).

JP 2016-179420 A JP 2019-107645 A JP 2019-107575 A

An object of the present disclosure is to provide a tubular separation membrane suitable for treating oil-containing wastewater, a tubular separation membrane module using the same, and a method for producing a tubular separation membrane.

In one embodiment of the present disclosure, a tubular separation membrane made of cellulose acetate and having a thickness of 0.05 to 0.4 mm,
Provided is a tubular separation membrane that satisfies the relationship between salt rejection and permeation flux expressed by the following formulas 1 and 2.
Formula 1: Y=AX1+B
(In formula 1, Y is the permeation flux [L/m ² · h], X1 is the sodium chloride [monovalent ion] blocking rate [%], and A is in the range of -1.4 < A < -1.0. constant, and B is a constant in the range of 100<B<150.)
Formula 2: Y=CX2+D
(In formula 2, Y is the permeation flux [L / m ² · h], X2 is the rejection rate [%] of magnesium sulfate [divalent ion], and C is in the range of -6.0 < C < -4.0 constant, and D indicates a constant in the range of 300<D<800.)

The present disclosure also provides a tubular separation membrane made of cellulose acetate and having a thickness of 0.05 to 0.4 mm,
When the blocking rate [%] of sodium chloride [monovalent ion] varies within the range of 15% to less than 100%,
The permeation flux varies within the range of 120 L/m ² · h to 15 L / m ² · h,
Further, it provides a tubular separation membrane in which the magnesium sulfate [divalent ion] rejection [%] varies within the range of 80% to less than 100%.

In another embodiment, the present disclosure provides a tubular separation membrane module using the tubular separation membrane as described above. In one example, the tubular separation membrane module may include a case housing and an assembly of tubular separation membranes housed in the case housing and formed by connecting a plurality of tubular separation membranes.

In still another embodiment, the present disclosure provides a method for producing a tubular separation membrane, which includes a membrane-forming solution preparation step, a coating step, a phase-separation membrane-forming step, and a post-treatment step. In one example, by changing the heat treatment temperature in the post-treatment process within the range of 30 ° C. to 98 ° C., the rejection rate [%] of sodium chloride [monovalent ion] and the rejection rate of magnesium sulfate [divalent ion] and the permeation flux [L/m ² ·h] are adjusted.

The tubular separation membrane of the present disclosure and the tubular separation membrane module using it have a sodium chloride (monovalent ion) rejection rate [%], a magnesium sulfate [divalent ion] rejection rate [%] and Flux (L/m ² ·h) can be exhibited in a well-balanced manner.

Further, in the tubular separation membrane of the present disclosure and the tubular separation membrane module using the same, the permeation flux (L/m ² ·h) increases as the blocking rate [%] of sodium chloride (monovalent ions) decreases. However, even in this case, it is possible to suppress the change in the rejection rate [%] of magnesium sulfate [divalent ions].

1 is a perspective view showing an embodiment of a tubular separation membrane; FIG. FIG. 2 is a plan view showing an assembly in which a plurality of tubular separation membranes (filtration membrane elements) shown in FIG. 1 are combined; 2 is a perspective view showing a membrane filtration module in which a plurality of tubular separation membranes (membrane membrane elements) shown in FIG. 1 are placed in a cylindrical case housing. FIG. However, it is displayed so that the inside which is not actually visible can be seen.

(Tubular separation membrane of the first embodiment)
For example, as shown in FIG. 1, the tubular separation membrane 10 of the first embodiment includes a porous support tube 11 for supporting a cellulose acetate separation membrane and a separation membrane (separation membrane) formed inside the tubular support. membrane layer) 12. A large number of holes 13 are distributed in the porous support tube 11 and penetrated in the thickness direction.

The separation membrane (separation membrane layer) 12 is formed by laminating a material on the inner surface of the tubular support, for example. The separation membrane (separation membrane layer) 12 may be arranged inside the porous support tube 11, thereby protecting the separation membrane (separation membrane layer) 12 from excessive expansion due to the pressure during liquid feeding.

As shown in FIG. 2, the tubular separation membrane of the first embodiment is an assembly 20 of tubular separation membranes in which a plurality of tubular separation membranes 10 are connected via connecting pipes (U-shaped pipes) 21. can be in the form of

As the porous support tube 11, one made of metal such as stainless steel or resin such as fiber-reinforced resin can be preferably used.

Although the material of the tubular support that supports the separation membrane layer is not particularly limited, it may be tubular nonwoven fabric made of synthetic polymers such as polyester, PVDF (polyvinylidene difluoride), PES (polyethersulfone), or the like. , paper, etc. can be used because they are permeable to water well, have high adhesion to the cellulose acetate membrane, and retain the rigidity of the tubular membrane. The thickness of the tubular support may be any thickness that can support the separation membrane 12, and can be, for example, 0.1 to 0.5 mm.

Separation membrane 12 is made of cellulose acetate and may be used, for example, as a reverse osmosis membrane or a nanofiltration membrane. Cellulose acetate can be produced with various properties such as the degree of acetyl group substitution, the degree of polymerization distribution of the glucose skeleton, and the purity of the glucose skeleton, depending on the type of cellulose material used as the raw material and the selected production conditions. Filtration performance (permeation flux, salt rejection, etc.) can vary depending on the cellulose.

In one embodiment, the cellulose acetate preferably has a degree of substitution within the range of 1.0 to 3.0, more preferably within the range of 1.3 to 2.7. good.

When the liquid to be treated (undiluted solution) is oil-containing wastewater generated by water-soluble cutting oil processing companies, aluminum die-casting processing companies, petroleum refining companies, etc., cellulose acetate has a low affinity for oil in the wastewater. By using cellulose acetate, filtration performance (permeation flux, salt rejection rate, etc.) can be enhanced.

The thickness of the separation membrane 12 (not including the thickness of the tubular support) may be 0.05 to 0.4 mm, preferably 0.1 to 0.3 mm, more preferably 0.15. It may be ~0.25 mm. If the thickness of the separation membrane 12 is less than 0.05 mm, for example, it may be difficult to stabilize the salt rejection value. In the form of a tubular separation membrane aggregate 20 in which a plurality of tubular separation membranes 10 are connected via connecting pipes (U-shaped pipes) 21 as shown in FIG. There is a problem that the initial tubular separation membrane 10 may be particularly susceptible to membrane damage. If the film thickness of the separation membrane 12 is too large, for example, greater than 0.4 mm, the permeation flux performance may significantly deteriorate.

The tubular separation membrane of the first embodiment may satisfy the relationship between the salt rejection rate and the permeation flux shown by the following formulas 1 and 2.
Formula 1: Y=AX1+B
(In formula 1, Y is the permeation flux [L/m ² · h], X1 is the sodium chloride [monovalent ion] blocking rate [%], and A is in the range of -1.4 < A < -1.0. and B indicates a constant within the range of 100<B<150.)
Formula 2: Y=CX2+D
(In formula 2, Y is the permeation flux [L / m ² · h], X2 is the rejection rate [%] of magnesium sulfate [divalent ion], and C is in the range of -6.0 < C < -4.0 and D indicates a constant within the range of 300<D<800.)

The tubular separation membrane of the first embodiment satisfies the relationship between the salt rejection and the permeation flux shown in Formulas 1 and 2, so that the rejection [%] of sodium chloride [monovalent ion] is When it becomes higher and the permeation flux [L/m ² · h] decreases, or the rejection rate [%] of sodium chloride [monovalent ion] decreases and the permeation flux [L / m ² · h] increases Even when the temperature is low, the change in the rejection rate [%] of magnesium sulfate [divalent ions] can be suppressed.

For example, even when the rejection [%] of sodium chloride [monovalent ion] changes within the range of 20% to 95%, and the permeation flux [L / m ² · h] changes accordingly, this In a preferred embodiment of the disclosure, the change in the rejection rate [%] of magnesium sulfate [divalent ions] can be suppressed within the range of 5% to 15%. In another preferred aspect of the present disclosure, in a similar case, the change in the rejection rate [%] of magnesium sulfate [divalent ions] can be suppressed within the range of 8% to 12%.

(Tubular separation membrane of the second embodiment)
The tubular separation membrane of the second embodiment includes a tubular support for supporting the same separation membrane as the tubular separation membrane 12 of the first embodiment, and a tubular separation membrane similar to the tubular separation membrane of the first embodiment. 1 or 2 in combination with a support tube similar to the porous support tube 11. can be shaped.

In the tubular separation membrane of the second embodiment, the sodium chloride [monovalent ion] rejection rate [%], the magnesium sulfate [divalent ion] rejection rate [%], and the permeation flux [L/m ² · h] may be related to each other.

In the tubular separation membrane of the second embodiment, the permeation flux is 120 L/m ² when the sodium chloride [monovalent ion] rejection [%] varies within the range of 15% to less than 100%. · h to 15 L/m ² ·h, and the rejection rate [%] of magnesium sulfate [divalent ions] may vary within a range of less than 100% to 80%. As described above, in the tubular separation membrane of the second embodiment, the rejection [%] of sodium chloride [monovalent ions] and the permeation flux vary within a wide range. The change in rejection [%] is small and suppressed.

As the tubular separation membrane of the second embodiment, for example, separation membranes having different filtration performances selected from the following modes can be used.

A first form having a sodium chloride (monovalent ion) rejection rate of more than 90%, a magnesium sulfate (divalent ion) rejection rate of more than 95%, and a lower limit of pure water permeation flux of 18 L/m ² h Tubular separation membrane.

A second form having a sodium chloride (monovalent ion) rejection rate of more than 80%, a magnesium sulfate (divalent ion) rejection rate of more than 93%, and a lower limit of pure water permeation flux of 33 L/m ² h Tubular separation membrane.

A third form having a sodium chloride (monovalent ion) rejection rate of more than 70%, a magnesium sulfate (divalent ion) rejection rate of more than 92%, and a lower limit of pure water permeation flux of 43 L/m ² h Tubular separation membrane.

A fourth form having a sodium chloride (monovalent ion) rejection rate of more than 50%, a magnesium sulfate (divalent ion) rejection rate of more than 90%, and a lower limit of pure water permeation flux of 55 L/m ² h Tubular separation membrane.

A fifth form having a sodium chloride (monovalent ion) rejection rate of 20 to 40%, a magnesium sulfate (divalent ion) rejection rate of more than 85%, and a pure water permeation flux of 75 to 120 L/m ² h. Tubular separation membrane.

(Tubular separation membrane module)
The tubular separation membrane module may be configured by housing the tubular separation membrane of the first embodiment or the tubular separation membrane of the second embodiment described above in a case housing. A tubular separation membrane module may therefore include a case housing and one or more tubular separation membranes housed therein.

For example, as shown in FIG. 3, an assembly 20 of tubular separation membranes, which is a plurality of tubular separation membranes connected via connecting pipes (U-shaped pipes) 21, is housed in a case housing, which is a cylindrical casing 31, and as a whole A single tubular RO membrane module 30 can be used. The tubular RO membrane module 30 is housed in a cylindrical casing 31 in which both end surfaces (first end surface 35 and second end surface 36) are closed and the assembly 20 is wound into the cylindrical casing 31 to form a cylindrical shape. there is

A raw water inlet 33 and a concentrated water outlet 34 of the assembly 20 protrude from a first end face 35 of the tubular casing 31 . A filtered water outlet 38 protrudes from a side surface 37 of the cylindrical casing 31, and a ventilation hole (not shown) may be formed.

(Method for producing tubular separation membrane)
The tubular separation membrane of the present disclosure, for example, the method for producing the tubular separation membrane of the first embodiment and the second embodiment includes a membrane-forming solution adjustment step, a coating step, a phase-separation membrane formation step, and a post-treatment step. may contain.

In the film-forming solution adjustment step, a predetermined amount of cellulose acetate is dissolved (dispersed) in a predetermined amount of a solvent, optionally by adding a predetermined amount of additives and/or nanomaterials, and if necessary, insoluble matter is removed. Filter off. When cellulose acetate is dissolved in a solvent, it can be carried out at a temperature of 20° C. to 90° C. depending on the type of solvent.

In addition, since the solubility of cellulose acetate in a solvent changes depending on the degree of substitution of acetyl groups, the film-forming solution adjustment step can be carried out in consideration of the degree of substitution of acetyl groups.

According to some embodiments, the solvent that can be used in the film-forming solution preparation step is capable of dissolving the cellulose acetate to be used, and is soluble in the solvent used as the coagulating liquid in the subsequent phase-separation film-forming step. and is generally soluble in water. Examples of such solvents include acetone, dimethylsulfoxide (DMSO), dimethylformamide (DMF), N-methylpyrrolidone (NMP), and the like.

The solvent may be a mixed composition solvent for the purpose of adjusting the performance of the separation membrane to be produced. As the solvent of the mixed composition, a solvent that cannot dissolve cellulose acetate but can dissolve cellulose acetate by being mixed with another solvent may be used. Solvents that can be used for the mixed solvent include water, alcohol, dioxane, and the like.

According to some embodiments, additives that can be used in the membrane-forming solution preparation step are substances that are soluble in the solvent used as the coagulation liquid in the subsequent phase-separation membrane-forming step, typically water soluble. It is a substance that Such additives can include lithium chloride, lithium bromide, lactic acid, formamide, polyethylene glycol (polyethylene oxide), and the like.

The additive can be localized at the interface between the cellulose acetate structure film and the coagulating liquid during film formation in the subsequent phase-separation film-forming step. As a result, the structure of the cellulose acetate membrane becomes rougher on the surface side and denser on the inner side of the membrane. From this point of view, the additive can be used in an appropriate amount depending on the filtration performance.

Examples of nanomaterials include CNF (carbon nanofiber), CNT (carbon nanotube), CNF (cellulose nanofiber), titanium oxide, and silica. An appropriate amount of the nanomaterial can be used for the purpose of improving the permeation flux and membrane strength of the tubular separation membrane.

The coating step is a step of coating the inside of the tubular support with the membrane-forming solution prepared in the membrane-forming solution preparation step. According to some embodiments, a jig for introducing the membrane-forming solution prepared in the membrane-forming solution preparation step is installed at one end of the tubular support, and a coating bob is set. The coating bob may be a stainless steel structure with a pointed spherical surface and a cylindrical back.

By moving the coating bob inside the tubular support, it is possible to coat the inside of the tubular support with a uniform thickness of the film-forming solution put into the tip side of the coating bob. In order to move the coating bob, a method of pushing out the bottom of the coating bob with compressed air, a method of winding the thread attached to the tip of the coating bob at a constant speed, and a state in which the coating bob is fixed , a method of moving the tubular support at a constant speed can be selected.

The coating speed may be appropriately adjusted depending on properties such as the structural viscosity of the film-forming solution to be used, the type of the tubular support, etc. In one example, it may be adjusted within the range of 0.5 to 5 m/min. . If the coating speed is too high, the coating resistance of the film-forming solution increases and excessive penetration into the tubular support may occur, resulting in an outer diameter defect called strike-through. On the other hand, if the coating speed is too slow, the productivity of the tubular film may decrease.

The phase separation film-forming step may be a film-forming step by a dry-wet phase conversion method, and the tubular support coated with the film-forming solution may be put into a coagulation tank charged with a coagulation liquid. As a result, the solvent and additives in the membrane-forming solution are dissolved in the coagulation liquid, forming a cellulose acetate membrane inside the tubular support.

The coagulating liquid is a solvent that dissolves the solvent and additives but does not dissolve cellulose acetate, and may generally be water. The filtration performance (permeation flux, salt blocking rate, etc.) of the separation membrane may change depending on the composition of the coagulating liquid, the temperature of the coagulating liquid, and the temperature and humidity of the room when the coagulating liquid is introduced.

The post-treatment step is a step for fixing the performance of the tubular membrane by applying predetermined heat and pressure to the cellulose acetate membrane by a predetermined method for a predetermined time. Predetermined heat and pressure can be applied via a fluid such as water or compressed air. The fluid may be stagnated inside the tubular separation membrane, or may be circulated and flowed inside the tubular separation membrane. Furthermore, after assembling the aggregate as shown in FIG. 2, a predetermined heat or pressure may be applied using a fluid.

By increasing or decreasing the heat treatment temperature in the post-treatment process within the range of 30 ° C. to 98 ° C., the sodium chloride [monovalent ion] rejection rate [%], magnesium sulfate (divalent ion) rejection rate and permeation flux (L /m ^2.h ) can be adjusted.

The heat treatment temperature in the post-treatment step is changed within the range of 30 ° C. to 98 ° C., so that the sodium chloride [monovalent ion] rejection rate [%], magnesium sulfate (divalent ion) rejection rate and permeation flux (L /m ^2.h ) can be adjusted. The heat treatment time in the post-treatment step can be 10 minutes or more and less than 120 minutes.

According to some embodiments, the tubular separation membrane obtained by the production method of the present disclosure has a sodium chloride [monovalent ion] rejection [%] within the range of 15% to less than 100%. When changing, the permeation flux changes within the range from 120 L/m ² · h to 15 L / m ² · h, and the rejection [%] of magnesium sulfate [divalent ions] is less than 100% to 80 It is adjusted to vary within a range of up to %. Thus, in the tubular separation membrane obtained by the production method of the present disclosure, the rejection [%] of sodium chloride [monovalent ion] and the permeation flux vary within a wide range, but magnesium sulfate [2 valence ion] is reduced and suppressed.

According to some embodiments, the tubular separation membranes of the present disclosure are used to reduce the volume of oil-laden wastewater generated by water-soluble cutting oil processing companies, aluminum die-casting processing companies, petroleum refining companies, etc. be able to. When used to reduce the volume of wastewater containing oil, the permeation flux with high concentration efficiency is 30 L/m ² ·Hr. In view of the above, there is a need for a tubular membrane that exhibits a salt rejection rate of around 90% for a salt as large as magnesium sulfate.

The tubular separation membrane of the present disclosure can be preferably used to reduce the volume of wastewater containing nano-sized impurities that cannot be completely blocked by ultrafiltration membranes, even in wastewater that does not contain oil. It can also be used as a tubular RO membrane in the publication.

Each aspect disclosed in this specification may be combined with any other feature disclosed in this specification. Each configuration and combination thereof in each embodiment is an example, and addition, omission, replacement, and other modifications of the configuration are possible as appropriate without departing from the gist of the present disclosure. This disclosure is not limited by the embodiments, but only by the claims.
Example

(1) Method for measuring the rejection rate [%] of sodium chloride [monovalent ions] and magnesium sulfate [divalent ions] A tubular separation membrane having the structure shown in Fig. 1 is used as described below. A tubular membrane element (TR-70C3-P18A manufactured by Daicen Membrane Systems) with a length of 2500 mm, in which a cellulose acetate reverse osmosis membrane with a thickness of 0.2 mm is laminated on the inner surface of a tubular support made of polyester nonwoven fabric with an inner diameter of 11.5 mm. (The porous support pipe 11 is made of fiber-reinforced resin) and 18 pipes connected in series (see FIG. 2) were used.

Under the operating conditions of average pressure of 2.5 MPa, circulating flow rate of 10 L/min, and linear velocity of membrane surface of 1.5 m/sec, circulating filtration operation of a mixed aqueous solution of sodium chloride and magnesium sulfate of 2000 mg/L each at a liquid temperature of 25 ° C. was performed for 15 times. minutes, and the salt rejection of sodium chloride and magnesium sulfate of the tubular membrane element was measured. Table 1 shows the measurement results.

(2) Method for measuring permeation flux [L/m ² ·h] A tubular separation membrane having the configuration shown in Fig. 1, wherein a thickness 18 tubular membrane elements (TR-70C3-P18A manufactured by Daisen Membrane Systems) with a length of 2500 mm laminated with cellulose acetate reverse osmosis membranes with a thickness of 0.2 mm (the porous support tube 11 is made of fiber reinforced resin) are arranged in series. A connected one (see FIG. 2) was used.

Under the operating conditions of an average pressure of 2.5 MPa, a circulation flow rate of 10 L/min, and a membrane surface linear velocity of 1.5 m/sec, a pure water circulation filtration operation was performed at a liquid temperature of 25°C for 15 minutes. was measured. Table 1 shows the measurement results.

Example 1
(Film-forming solution adjustment step)
A film-forming solution was prepared by dissolving 3.6 kg of cellulose acetate (acetyl substitution degree: 2.5) manufactured by Daicel Corporation and 6.4 kg of lactic acid as an additive in 10 kg of acetone as a solvent at room temperature.

(Coating process)
A jig for pouring a membrane-forming solution was placed at one end of a polyester nonwoven tubular support having a length of 2700 mm and an inner diameter of 11.5 mm, and about 70 g of the membrane-forming solution was put into the jig. Thereafter, a stainless steel coating bob with an inner diameter of 11.0 mm was used, and the thread attached to the tip of the coating bob was wound up at 2 m/min to coat the inside of the tubular support with the film-forming solution. .

(Phase separation film formation process)
After coating, it was quickly put into a coagulation tank filled with cold water of 1 to 3° C. using a belt conveyor, immersed for 1 hour, and then washed with water. The length of the tubular membrane was adjusted by cutting both ends so that the tubular membrane had a length of 2500 mm.

(Post-treatment process)
In a state in which water can be circulated inside the tubular separation membrane, hot water at 87°C is continuously flowed for 35 minutes under a pressure that allows the water to flow slightly. After heat treatment, the temperature of the tubular membrane reaches room temperature. After that, the pressure treatment was continued for 30 minutes so that the internal pressure of the tubular separation membrane quickly reached 2.5 MPa.

The produced tubular separation membrane had a thickness of 0.2 mm and a membrane area of 1.6 m ² . A plurality of the same tubular membranes were manufactured by the same manufacturing method, and using a tubular membrane element (see FIG. 2) in which 18 of these membranes were connected in series, the permeation flux of the tubular membrane element and the sodium chloride and magnesium sulfate were measured. Table 1 shows the measurement results.

Examples 2-5
A tubular separation membrane was produced in the same manner as in Example 1. However, the heat treatment temperature and hot water flow time in the post-treatment process were changed as shown in Table 1. Measurements similar to those in Example 1 were performed. Table 1 shows the measurement results.

As is clear from Table 1, when the rejection rate [%] of sodium chloride (monovalent ion) changes from 20% to 90% or more, the lower limit of the permeation flux [L/m ² h] is 75 to 18. However, the change in the rejection rate [%] of magnesium sulfate (divalent ions) was small and suppressed within the range of 10%.
Industrial applicability

The tubular separation membrane of the present disclosure can be used to reduce the volume of oil-containing wastewater generated by water-soluble cutting oil processing companies, aluminum die-casting processing companies, petroleum refining companies, and the like.
Code explanation

10 Tubular separation membrane (filtration membrane element)
11 Porous Support Tube 12 Separation Membrane 20 Tubular Separation Membrane Assembly 30 Tubular Separation Membrane Module

Claims (2)

A tubular separation membrane, which is a reverse osmosis membrane or a nanofiltration membrane, comprising a cellulose acetate reverse osmosis membrane in which a cellulose acetate reverse osmosis membrane is laminated on the inner surface of a tube of a tubular support,
The tubular separation membrane is used to reduce the volume of oil-containing wastewater generated in water-soluble cutting oil processing, aluminum die-casting processing, or oil refining,
The thickness of the cellulose acetate reverse osmosis membrane of the tubular separation membrane is in the range of 0.05 to 0.4 mm, and the sodium chloride (monovalent ion) rejection, magnesium sulfate (divalent Ion) rejection rate, pure water permeation flux, when the rejection rate [%] of sodium chloride [monovalent ion] changes in the range from 15% to less than 100%, the permeation flux is 120 L/m ² h to 15 L/m ² · h, and the rejection rate [%] of magnesium sulfate (divalent ions) is adjusted to change within the range of less than 100% to 80%. can be,
A first form having a sodium chloride (monovalent ion) rejection rate of 90% or more , a magnesium sulfate (divalent ion) rejection rate of 95% or more, and a lower limit of pure water permeation flux of 18 L/m ² ·h. ,
A second filter with a sodium chloride (monovalent ion) rejection rate of 80% or more , a magnesium sulfate (divalent ion) rejection rate of 93% or more, and a lower limit of pure water permeation flux of 34 L/m ² h. form,
A third form having a sodium chloride (monovalent ion) rejection rate of 70% or more , a magnesium sulfate (divalent ion) rejection rate of 92% or more, and a lower limit of pure water permeation flux of 43 L/m ² ·h. ,
A fourth form having a sodium chloride (monovalent ion) rejection rate of 50% or more , a magnesium sulfate (divalent ion) rejection rate of 90% or more, and a lower limit of pure water permeation flux of 55 L/m ² ·h. , and Sodium chloride (monovalent ion) blocking rate is 20 to 40%, magnesium sulfate (divalent ion) blocking rate is 85% or more, and the lower limit of pure water permeation flux is 75 L/m ² h. A tubular separation membrane which is any one selected from the fifth mode.
(1) Rejection of sodium chloride [monovalent ion] and magnesium sulfate (divalent ion) [%]
A tubular separation membrane was prepared by connecting 18 tubular membrane elements in series with a length of 2,500 mm, which consisted of a tubular polyester nonwoven support with an inner diameter of 11.5 mm and a cellulose acetate reverse osmosis membrane with a thickness of 0.2 mm laminated on the inner surface of the tube. used.
Under the operating conditions of an average pressure of 2.5 MPa, a circulating flow rate of 10 L / min, and a membrane surface linear velocity of 1.5 m / sec, a liquid temperature of 25 ° C. and a sodium chloride aqueous solution of 2000 mg / L each were subjected to circulating filtration for 15 minutes. The salt rejection rate of sodium chloride and magnesium sulfate of Lar type separation membrane was measured.
(2) Permeation flux [L/m ²・h]
A tubular separation membrane was prepared by connecting 18 tubular membrane elements in series with a length of 2,500 mm, which consisted of a tubular polyester nonwoven support with an inner diameter of 11.5 mm and a cellulose acetate reverse osmosis membrane with a thickness of 0.2 mm laminated on the inner surface of the tube. used.
Under the operating conditions of an average pressure of 2.5 MPa, a circulation flow rate of 10 L/min, and a membrane surface linear velocity of 1.5 m/sec, a liquid temperature of 25°C and a pure water circulation filtration operation were performed for 15 minutes. Flux was measured. A tubular separation membrane module comprising a case housing in which a plurality of tubular separation membranes according to claim 1 are connected.

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