JP2000202257A - Composite semipermeable membrane and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a composite semipermeable membrane having high solute removing property and high water permeability and capable of operating at high recovery. SOLUTION: The composite semipermeable membrane has a separation functional layer of a crosslinked polyamide formed on a porous supporting membrane by the polycondensation of a polyfunctional amine, a polyfunctional acid halide and a polyfunctional acid anhydride. Water permeability under 0.3 MPa operation pressure at 25 deg.C and pH 6.5 is controlled to be 0.8-4.0 m3/ m2.day and the removing rate of humic acid is controlled to >=98%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for selectively separating and removing contaminants and trace harmful substances and their precursors contained in raw water such as a water purification plant, and for permeating silica to deposit a film on a film surface. The present invention relates to a composite semipermeable membrane which can be suitably used for preventing and recovering drinking water and the like in high yield, and a method for producing the same.

[0002]

2. Description of the Related Art With respect to separation of a mixture, there are various techniques for removing substances (eg, salts) dissolved in a solvent (eg, water). In recent years, however, membrane separation has been used as a process for saving energy and resources. The law is being used. The membrane used for the membrane separation method includes a microfiltration membrane, an ultrafiltration membrane, and a reverse osmosis membrane. More recently, a membrane located between a reverse osmosis membrane and an ultrafiltration membrane (loose RO membrane or NF membrane: Nanofiltration membrane)
(rane) has also appeared and been used. This technology can be used, for example, to obtain drinking water from seawater, can water, and water containing harmful substances, and has also been used in the production of industrial ultrapure water, wastewater treatment, and recovery of valuable resources. Was.

Most of currently available composite semipermeable membranes have a porous support membrane having a gel layer and an active layer obtained by crosslinking a polymer, and a porous support membrane having an active layer obtained by polycondensation of a monomer on a porous support membrane. It has two types. Among them, a composite semipermeable membrane comprising a porous support membrane coated with a separation functional layer made of a crosslinked polyamide obtained by a polycondensation reaction between a polyfunctional amine and a polyfunctional acid halide has a permeability and a selective separation property. Widely used as high reverse osmosis membrane.

However, the demand for a practical semipermeable membrane for reverse osmosis has been increasing year by year. From the viewpoint of energy saving, a semipermeable membrane having high water permeability and capable of operating at a lower pressure while maintaining high solute removal properties has been developed. Is desired. For example, in JP-A-64-56108, 7.5 kg / cm of 4-chloroformylphthalic anhydride is added in the presence of 4-chloroformylphthalic anhydride.
^2. Description of the Related Art A composite semipermeable membrane having high desalination and high water permeability at an ultra-low pressure operation of ² (0.75 MPa) is known. But,
Even in this method, the desalting property and the water permeability at an extremely low pressure operation of about 0.3 MPa were insufficient. On the other hand, a high recovery operation is also desired, but in a membrane with a high silica removal rate, the concentration of silica on the concentrated water side rapidly increases and precipitates on the membrane surface, resulting in a decrease in membrane performance and stable operation. Water quality cannot be improved.

[0005] In recent years, in a water treatment plant using raw water such as river water and lake water, carcinogenicity is caused by chlorine disinfection treatment of soluble organic matter (trihalomethane precursor) flowing from peat lands or mountainous areas. The generation of halogen-containing organic substances (trihalomethanes) having the following has become a serious problem. The most important of the trihalomethane precursors is humic acid, a soluble organic substance having a molecular weight of thousands to tens of thousands. At present, in a treatment method using ozone or activated carbon, which is being considered for introduction into a water purification plant, the removal rate at the start of operation is high, but the removal rate decreases rapidly after long-term operation. This requires frequent replacement of the activated carbon. In addition, in biological treatment methods such as a catalytic oxidation method and a biofilm method, there is a problem that a soluble organic substance cannot be sufficiently removed because soluble organic matter is produced after metabolism of the organism. In the membrane separation method, the microfiltration membrane and the ultrafiltration membrane have a large pore size, so that humic acid cannot be sufficiently removed. Further, in the reverse osmosis membrane, the pore diameter is small and the humic acid removal rate is high, but the silica removal rate is high. Therefore, it is difficult to operate the reverse osmosis membrane at a high recovery rate using the reverse osmosis membrane.

[0006]

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides a composite semipermeable membrane having high solute removal and high water permeability and capable of operating at a high recovery rate. With the goal.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention relates to a method for forming a porous functional layer of a crosslinked polyamide by polycondensation from a polyfunctional amine, a polyfunctional acid halide and a polyfunctional acid anhydride halide. A composite semipermeable membrane formed on a porous support membrane, operating pressure 0.3 MPa, temperature 25
The amount of permeated water at 0.8 ° C. and pH 6.5 is 0.8 to 4.0 m ^3.
/ M ² · day and a humic acid removal rate of 98% or more.

Here, the humic acid removal rate is preferably 99% or more, and the thickness of the separation function layer is 1 to 300 nm.
Is also preferable.

Further, the concentration of the carboxyl group in the separation functional layer analyzed by X-ray photoelectron spectroscopy (ESCA) is 0.1%.
It is also preferable that it is 02 or more and less than 0.06.

[0010] It is also preferred that the porous support membrane contains at least one selected from the group consisting of polysulfone, polyamide, polyester and vinyl polymer.

An operating pressure of 0.3 MPa and a temperature of 25
° C., silica concentration 30 ppm, when circulated and evaluated for 3 hours in an aqueous solution of pH 6.5, the silica transmittance is 55% or more,
It is also preferable that the amount of permeated water is 0.8 m ³ / m ² · day or more.

Further, the polyfunctional amine is a mixed amine of an aliphatic polyfunctional amine and an aromatic polyfunctional amine, and the aliphatic polyfunctional amine is a piperazine-based amine represented by the following general formula and a derivative thereof; Group polyfunctional amines are metaphenylenediamine, paraphenylenediamine, 1,3
An amine selected from 5-triaminobenzene or an N-alkylated product thereof is also preferable.

[0013]

Embedded image R1 to R8: H, a _{OH, COOH, SO 3 H,} NH 2 or The aliphatic group ranging number of 1 to 4 carbon atoms, the polyfunctional acid halide is a polyfunctional acid chloride,
It is also preferred that the polyfunctional anhydride halide is a trimellitic anhydride halide represented by the following general formula and a derivative thereof.

[0014]

Embedded image X1, X2: H, OH, COOH, SO ₃ H, COF,
COCl, COBr, COI, an aliphatic group having 1 to 3 carbon atoms or a group forming an acid anhydride X3: H, OH, COOH, SO ₃ H, COF, COC
l, COBr, COI, or an aliphatic group having a carbon number in the range of 1 to 3 Y: F, Cl, Br or I Further, the surface of the separation functional layer may have a substantially spherical projection at the tip. Preferably, in 70% or more of the total number of substantially spherical projections, the ratio of the major axis / minor axis of the pointed end in a plan view is 1.0 to 1.0.
2.0 is also preferable.

[0015] It is also preferable that the porous support membrane contains at least one selected from the group consisting of polysulfone, polyamide, polyester and vinyl polymer. Further, from a polyfunctional amine and a polyfunctional acid halide, a method for producing a composite semipermeable membrane that forms a separation functional layer of a crosslinked polyamide on a porous support membrane by polycondensation,
In the polycondensation, a polyfunctional acid anhydride halide is present, and the polyfunctional amine contains an aliphatic polyfunctional amine and an aromatic polyfunctional amine, and the molar ratio thereof is 40/60.
A method for producing a composite semipermeable membrane in the range of ９５95/5 is also preferred.

The molar ratio between the polyfunctional acid halide and the polyfunctional acid anhydride halide is 75/25 to 15/85.
Is also preferably within the range.

Further, a fresh water producing method in which solid components in raw water are separated using the composite semipermeable membrane described above is also preferable. In this case, it is also preferable to supply raw water to the composite semipermeable membrane at a pressure in the range of 0.1 to 3.0 MPa.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION The polyfunctional amine of the present invention is preferably a mixed amine of an aliphatic polyfunctional amine and an aromatic polyfunctional amine, wherein the aliphatic polyfunctional amine is represented by the following general formula: Piperazine amines and derivatives thereof are preferred, and piperazine, 2,5-dimethylpiperazine,
Methylpiperazine, 2,6-dimethylpiperazine, 2,
3,5-trimethylpiperazine, 2,5-diethylpiperazine, 2,3,5-triethylpiperazine, 2-n-
Examples thereof include propylpiperazine and 2,5-di-n-butylpiperazine, and particularly preferred are piperazine and 2,5-dimethylpiperazine.

[0019]

Embedded image R1 to R8: H, OH, COOH, SO ₃ H, NH ₂ , or an aliphatic group having 1 to 4 carbon atoms, or an aromatic polyfunctional amine is a compound having two or more amino groups in one molecule. Amines having, but not limited to, metaphenylenediamine, paraphenylenediamine, 1,3,5-triaminobenzene, and N-
N, N-dimethylmetaphenylenediamine, N, N-diethylmetaphenylenediamine as an alkylated product,
Examples thereof include N, N-dimethylparaphenylenediamine and N, N-diethylparaphenylenediamine, and particularly preferred are metaphenylenediamine and 1,3,5-triaminobenzene.

The molar ratio between the aliphatic polyfunctional amine and the aromatic polyfunctional amine used in the present invention is from 40/60 to 95/5, more preferably from 70/30 to 90/10. If the amount of the aliphatic polyfunctional amine is less than 40 mol%, the amount of permeated water decreases, and if it is more than 95 mol%, good selective separation cannot be obtained.

The polyfunctional acid halide is a compound having two per molecule.
It is not particularly limited as long as it is an acid halide having two or more halogenated carbonyl groups and gives a polyamide by reaction with the above amine. Examples of the polyfunctional acid halide include 1,3,5-cyclohexanetricarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 1,3,5
-Benzenetricarboxylic acid, 1,2,4-benzenetricarboxylic acid, 1,3-benzenedicarboxylic acid, 1,4-
Acid halides of benzenedicarboxylic acid can be used. Particularly, trimesic acid chloride, which is an acid halide of 1,3,5-benzenetricarboxylic acid, is preferable from the viewpoints of economy, availability, ease of handling, and ease of reaction. Further, the above-mentioned polyfunctional acid halides can be used alone or as a mixture.

The term "polyfunctional acid anhydride halide" as used herein means one having one or more acid anhydride moieties and one or more carbonyl halide groups in one molecule. Examples thereof include benzoic anhydride and anhydride. Although carbonyl halides of phthalic acid and the like can be mentioned, trimellitic anhydride halides and derivatives thereof represented by the following general formula are particularly preferred from the viewpoint of high water permeability and an appropriate pore diameter for removing soluble organic substances. Used.

[0023]

Embedded image X1, X2: H, OH, COOH, SO ₃ H, COF,
COCl, COBr, COI, an aliphatic group having 1 to 3 carbon atoms or a group forming an acid anhydride X3: H, OH, COOH, SO ₃ H, COF, COC
l, COBr, COI, or an aliphatic group having a carbon number in the range of 1 to 3 Y: F, Cl, Br or I As a material of the ultrathin film of the composite semipermeable membrane of the present invention, a crosslinked or linear organic material is used. Polymers can be used. In order for the composite semipermeable membrane to exhibit high separation performance, the polymer is preferably polyamide, polyurethane, polyether, polyester, polyimide, cellulose ester, or vinyl polymer, and particularly preferably polyamide. Crosslinked polyamides obtained by reacting a polyfunctional amine with a polyfunctional acid halide and a polyfunctional acid anhydride halide are more preferred.

The molar ratio between the polyfunctional acid halide and the polyfunctional anhydride halide used in the present invention is important for obtaining a composite semipermeable membrane having contradictory performances such as high water permeability and selective separation. is there. The charged molar ratio of the polyfunctional acid halide and the polyfunctional acid anhydride halide is 75/25 to 15
/ 85 is preferred, and 65/35 to 35/65 is more preferred. When the molar ratio of the polyfunctional acid anhydride halide is 25 or less, the amount of permeated water decreases, and when the molar ratio is 85 or more, good selective separation cannot be obtained.

As a preferred porous support membrane, a polysulfone support membrane reinforced by a cloth can be exemplified. The porous support membrane is a layer having substantially no separation performance, and is used to impart mechanical strength to the separation function layer having the separation performance, and has uniform and fine pores or one side to the other. The surface of each side has a large fine hole gradually, and the size of the fine hole is 100
A supporting film having a structure of not more than nm is preferred. The above porous support membrane was manufactured by Millipore Co., Ltd. “Millipore Filter V”.
It can be selected from various commercially available materials such as "SWP" (trade name) and "Ultra Filter UK10" (trade name) manufactured by Toyo Roshi Kaisha, but usually, "Office of Saline Water Research & Co., Ltd."・ Development Progress Report “No. 359 (19
68). The material is usually a homopolymer or blend of polysulfone, cellulose acetate, cellulose nitrate, polyvinyl chloride, etc., but polysulfone, which is chemically, mechanically and thermally stable, is used. preferable. For example, the polysulfone dimethylformamide (DM
F) casting the solution to a certain thickness on a densely woven polyester or nonwoven fabric and wet coagulating it in an aqueous solution containing, for example, 0.5% by weight of sodium dodecyl sulfate and 2% by weight of DMF, A porous support membrane having most of the surface having fine pores having a diameter of several tens nm or less can be obtained.

The term "carboxyl group concentration" refers to the amount of carboxyl group (mol number) based on the total amount of carbon (mol number) in the separation function layer.
And is represented by the following formula.

[0027]

(Equation 1) X-ray photoelectron spectroscopy (ESCA)
Using Journal of Polymer S
science Vol. 26 559-572 (198
8) and the Journal of the Adhesion Society of Japan, Vol. 27 No. 4 (1
It can be determined by using the gas phase chemical modification method exemplified in 991).

Hereinafter, a method for measuring the carboxyl group concentration will be described. As the labeling reagent, trifluoroethanol is used for the carboxyl group. The sample was subjected to gas phase chemical modification with the labeling reagent. At the same time, the reaction rate (r) of the labeling reagent and the residual rate (m) of the reaction residue were determined from the ESCA spectrum of the polyacrylic acid standard sample subjected to gas phase chemical modification. Ask. Next, the area intensity [F1s] of the F1s peak (peak of 1s orbital of fluorine) formed by the reaction between the sample and the labeling reagent is determined. In addition, C
Area intensity of 1s peak (peak of 1s orbital of carbon) [C
1s].

The measurement conditions are shown below.

Excitation X-ray: Mg Kα 1,2 line (1253.6 eV) X-ray output: 8 kV 30 mV Photoelectron escape angle: 90 ° In data processing, the C1s peak position of neutral carbon (CHx) was adjusted to 284.6 eV. .

The area intensity [F1 obtained as described above
s] and [C1s] to Journalof Polyme
r Science Vol. 26 559-572
(1988), the carboxyl group concentration can be obtained by substituting into the following equation.

[0032]

(Equation 2) R _COOH : carboxyl group concentration [F1s]: area intensity of peak of 1s orbital of fluorine kF1s: sensitivity correction value of peak of 1s orbital of fluorine r: reaction rate of labeling reagent [C1s]: peak of 1s orbital of carbon Area strength m: Residual rate of reaction residue If the carboxyl group concentration is high, the carboxyl group end of the membrane increases and the water permeability increases, but the crosslink density decreases and the harmful substance removal performance decreases. Conversely, when the carboxyl group concentration is low, the number of unreacted terminals decreases, and the crosslink density increases, thereby lowering the water permeability. Therefore, the carboxyl group concentration is 0.02 or more and less than 0.06, preferably 0.02
The value is preferably 0.04 or less. The thickness of the separation function layer in the composite semipermeable membrane is 1 nm to 300 nm, preferably 1 nm to 300 nm.
nm to 100 nm is good. If the thickness of the separation functional layer is too small, the number of defects at the time of film formation increases, the film tends to be damaged at the time of handling, and the defects occur even when pressure is applied, thereby lowering the rejection rate. On the other hand, if the thickness of the separation function layer is too large, the transmission rate coefficient decreases, and a sufficient transmission amount cannot be obtained.

The substantially spherical projections on the surface of the separation functional layer are small projections having a height of 1 to 800 nm and a diameter of 1 to 500 nm.
It can be observed with a scanning electron micrograph or a transmission electron micrograph of the surface or cross section of the separation function layer. Further, the size and distribution of each substantially spherical protrusion can be obtained by analyzing the electron micrograph. For example, in the case of a surface photograph of a scanning electron microscope, a platinum or quaternary ruthenium, preferably ruthenium tetroxide is thinly coated on the surface of the film sample, and a high-resolution field emission scanning electron microscope (UHR) is applied at an accelerating voltage of 1 to 6 kV. -FE-SEM). As the high-resolution field emission scanning electron microscope, a Hitachi S-900 type electron microscope or the like can be used. The observation magnification is preferably 5,000 to 100,000, and 10,000 to 5 to obtain the size distribution of the substantially spherical projections.
It is preferably 0000-fold. From the obtained electron micrograph, the size of the substantially spherical projection can be directly measured on a scale or the like in consideration of the observation magnification.

The substantially spherical projections in the present invention are small projections having a substantially spherical shape and covering the separation function layer observed by an electron microscopic photograph of the surface of the composite semipermeable membrane. The minor axis ratio can be determined by the following method. A 20,000-fold film surface scanning electron micrograph obtained as an example is sectioned by a square having a side of 10 cm. Next, the major axis and the minor axis of the substantially spherical projection in this square are measured on a scale. In this way, the distribution can be obtained by measuring the major axis and minor axis of all the substantially spherical projections in the square. It should be noted that in the electron microscopic observation photograph, substantially spherical protrusions are buried by more than half, or substantially spherical protrusions that are less than the observable limit due to shading are not problematic even if cut off and calculated, and the lower limit of the major axis is particularly limited. Is not something,
Preferably it is approximately 50 nm. Further, when only the upper semicircle of the substantially spherical projection can be observed in the above observation photograph, a substantially spherical projection is drawn assuming the lower semicircle, the major axis and minor axis are measured, and the major axis / minor axis ratio is obtained. I can do it.

The ratio of the major axis to the minor axis of the substantially spherical projections and the distribution thereof can also be determined by taking an electron micrograph or a morphological diagram of the substantially spherical projections traced from the electron micrograph into a computer and performing image processing. . For example, it can be calculated by image processing software "P'-Analyzer" using "PIAS-IV" device manufactured by Pierce Co., Ltd. Further, with these methods, the distribution can be calculated from all the substantially spherical protrusions shown in the electron micrograph.

Conventionally, substantially spherical projections (also referred to as pleated structures) have been observed in composite membranes formed by the interfacial polycondensation method, and it has been reported that increasing the surface area increases the amount of permeated water (Matsuo Kawasaki). , Takeshi Sasaki, Masahiko Hirose, Membrane, 22
(5), 257-263 (1997)), but the shape was a seaweed like a kelp rather than a substantially spherical shape. As a result of various investigations, by optimizing the monomers used and the film forming conditions, the substantially spherical projections having a major axis / minor axis ratio of 1.0 to 2.0 in the separation functional layer at a low pressure can be obtained. It has been found that the composite semipermeable membrane to be used has a high separation performance and is preferable. The distribution is such that the ratio of major axis / minor axis is 1.
Substantially spherical protrusions of 0 to 2.0 represent 7 of the total number of substantially spherical protrusions.
Those having 0% or more, preferably 80% or more are preferable. If the distribution is less than 70%, the target membrane performance may not be obtained due to the non-uniformity of the separation function layer, or the dispersion of the membrane performance may increase. When the ratio of the major axis / minor axis of the substantially spherical projection exceeds 2.0, it becomes a tubular or seaweed-like seaweed rather than a substantially spherical projection,
Dirt easily accumulates in these gaps, and when used at high pressure, there may be a problem with pressure resistance.

The separation functional layer of the present invention may be coated by a method of coating a polymer, a method of further crosslinking the coated polymer, a method of polymerizing a monomer on the surface of a porous support membrane, or a method of coating a polymer on a surface of a porous support membrane. Interfacial polycondensation can be performed. In particular, the separation functional layer having a projection having a substantially spherical point on the surface according to the present invention can be obtained by a method of interfacial polycondensation on the surface of the porous support membrane. At this time, the size of the substantially spherical protrusion can be controlled by changing the concentration of each solution of the interfacial polycondensation and the additive.
The use of a hydrocarbon having 7 or more carbon atoms as a solvent immiscible with water is also effective for obtaining the separation functional layer of the present invention.

Next, a method for producing the present composite semipermeable membrane will be described.

The separation function layer having substantially separation performance in the composite semipermeable membrane contains the above-mentioned aqueous solution containing an amine and the above-mentioned polyfunctional acid halide in which the above-mentioned polyfunctional acid anhydride halide coexists. It is formed by using an organic solvent solution immiscible with water and reacting on the above-mentioned porous support membrane.

The molar ratio between the aliphatic polyfunctional amine and the aromatic polyfunctional amine used in the present invention is 40/60 to 40/60 as described above.
95/5, more preferably 70/30 to 90/10, and the concentration of the amine compound in the mixed amine aqueous solution is 0.1 to 20% by weight, preferably 0.5 to 15% by weight.
It is. Further, if the aqueous solution and the organic solvent solution do not hinder the reaction between the amine compound and the polyfunctional acid halide in the presence of the polyfunctional anhydride halide,
If necessary, compounds such as an acylation catalyst, a polar solvent, an acid scavenger, a surfactant, and an antioxidant may be contained.

The coating of the aqueous solution of the amine on the surface of the porous support membrane may be carried out as long as the aqueous solution is uniformly and continuously coated on the surface. It may be performed by a method of coating, a method of immersing the porous support membrane in the aqueous solution, or the like.

Next, the excessively applied aqueous solution of the amine is removed by a draining step. As a method of draining, for example, there is a method in which the membrane surface is held in a vertical direction and flows naturally. After draining, the membrane surface may be dried to remove all or part of the water in the aqueous solution.

Next, an organic solvent solution of the polyfunctional acid halide coexisting with the polyfunctional acid anhydride halide is applied, and a crosslinked polyamide separation functional layer is formed by a reaction. The concentration of the polyfunctional acid halide is not particularly limited, but if it is too small, the formation of an ultrathin film as an active layer may be insufficient and a defect may occur. About 0.01 to 1.0% by weight is preferable. The method of contacting the polyfunctional acid halide in the presence of the polyfunctional acid anhydride halide with the aqueous amine solution phase may be carried out in the same manner as the method of coating the aqueous amine solution on the porous support membrane. Further, the removal of the organic solvent after the reaction,
The method can be carried out by maintaining the membrane in the vertical direction and removing excess non-polar solvent by natural flow.

The organic solvent is required to be immiscible with water, to dissolve the polyfunctional acid halide and not to break the porous support membrane, and to be capable of forming a crosslinked polymer by reaction. Either may be used. Representative examples include liquid hydrocarbons and halogenated hydrocarbons such as trichlorotrifluoroethane, but they are substances that do not destroy the ozone layer, are readily available, easy to handle, and safe to handle. In consideration of the above, octane, nonane, decane, undecane, dodecane, tridecane, tetradecane, heptadecane, hexadecane, etc., and a simple substance such as cyclooctane, ethylcyclohexane, 1-octene, 1-decene or a mixture thereof are preferably used.

The membrane may be a hollow fiber or a flat membrane. The composite semipermeable membrane of the present invention can be used by incorporating it into a spiral, tubular, plate and frame module, but the present invention is not limited to these usage forms.

The harmful substances contained in the raw water and its precursors can be removed at an operating pressure of 0.1 to 3.0 MPa using the composite semipermeable membrane of the present invention. When the operating pressure is reduced, the capacity of the pump used is reduced and the power cost is reduced, but the membrane is easily clogged and the amount of permeated water is reduced. Conversely, when the operating pressure is increased, the power cost increases for the above-mentioned reason, and the amount of permeated water increases. Therefore, the operating pressure range is 0.1 to 3.0 MPa, preferably 0.1 to 3.0 MPa.
2 to 2.0 MPa, particularly preferably 0.2 to 1.0 MPa. If the amount of permeated water is high, clogging due to fouling on the membrane surface occurs, and if it is low, the cost increases, so the range of permeated water is 0.8 to 4.0 m ³ / m ² · day, preferably 0.85.
~ 2.5 m ³ / m ² · day is preferable for stably maintaining the amount of water. Further, in order to reduce the fresh water cost and efficiently collect the supply water, the recovery rate is 80% or more, preferably 85% or more,
More preferably, it is 90% or more.

The harmful substance mentioned here includes a trihalomethane precursor. Trihalomethane precursors produce carcinogenic trihalomethanes in chlorine disinfection at water purification plants. Examples of the trihalomethane precursor include humic acid and fulvic acid. Particularly, humic acid produces a large amount of trihalomethane, and its removal rate is preferably 98% or more, more preferably 99% or more.

By using the composite semipermeable membrane of the present invention, it is possible to transmit silica at a silica concentration of 30 ppm as SiO ₂ (national average value) and to prevent the formation of silica scale. In the case of a membrane having a low silica permeability, there is a problem that when a high recovery rate operation is performed, silica deposits on the membrane surface and closes the membrane surface, so that a high amount of permeated water cannot be obtained. Therefore, the silica transmittance is 55% or more, more preferably 65%.
Above is good.

By using the above-mentioned means, it has high humic acid removal property and high water permeability which cannot be achieved by conventional microfiltration membranes, ultrafiltration membranes, reverse osmosis membranes, etc., and high silica permeability. To realize a composite semipermeable membrane capable of high recovery operation.

[0050]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

In the examples, the removal rate and the transmittance were determined by the following equations.

Removal rate (%) = {1-[(solute concentration in permeate) / (solute concentration in feed)]} × 100 transmittance (%) = [(solute concentration in permeate) / (Solute concentration in the feed liquid)] × 100 The maximum possible recovery rate was determined by solving the following simultaneous equations.

1. F = B + P F × Cf = B × Cb + P × Cp 3. Removal rate = (1−Cp / Cf) × 100 Maximum possible recovery rate = P / F × 100 where, F: feed liquid flow rate, B: concentrate flow rate, P: permeate flow rate, Cf: solute concentration in feed liquid, Cb: solute concentration in concentrate (120 ppm) : PH of silica = 6.5, 25 ° C.
, Cp: the solute concentration in the permeate.

Further, the amount of fresh water is determined by the amount of permeated water per unit area (m ² ) per unit time (day) per unit area (m ² ) (m ³ / m ² ···
Day).

(Reference Example) The fiber-reinforced polysulfone support membrane (ultrafiltration membrane) used in the present invention was produced by the following method.

Taffeta made of polyester fiber having a length of 30 cm and a width of 20 cm (both the warp and the weft are 1
50 denier multifilament yarn, woven density 90
Book / inch, width 67 / inch, thickness 160 μm) was fixed on a glass plate, and a 15% by weight solution of polysulfone in dimethylformamide (DMF) was cast at a thickness of 200 μm at room temperature (20 ° C.) Immediately immersed in pure water and left for 5 minutes to produce a fiber-reinforced polysulfone support membrane (hereinafter abbreviated as FR-PS support membrane). The thus obtained FR-PS support film (thickness 2
10 to 215 μm) is produced at a pressure of 0.01 MPa,
1.7 m ³ / m ² · day measured at a temperature of 25 ° C. An ultrafiltration test was carried out under the same conditions as above using 2 ppm humic acid adjusted to pH 6.5 as raw water. As a result, the removal rate of humic acid was 60%. Further, Na ₂ Si
O ₃ · 9H ₂ 0 was used as a an aqueous solution prepared by dissolving to be 30ppm corresponds as SiO ₂ raw water, ultrafiltration test result under the same conditions as humic acid, the transmittance of the silica, 9
9.9%.

(Comparative Example 1) FR manufactured according to Reference Example
The -PS support membrane was immersed for 1 minute in an aqueous solution containing 3% by weight of the entire amine and having a molar ratio of m-phenylenediamine / piperazine = 20/80. After slowly pulling up the support membrane vertically and removing excess aqueous solution from the support membrane surface,
The surface is completely wetted with a solution obtained by adding trimellitic anhydride chloride to a decane solution containing trimesic acid chloride at 0.06% by weight and trimellitic chloride / trimellitic anhydride chloride = 30/70 molar ratio. And left for 1 minute. Next, the film is removed vertically by removing the excess solution by verticalizing the film, and then the wind speed at the film surface is 8 m / s and the temperature is 3 to evaporate the solvent remaining on the film surface.
It was dried by blowing air at 0 ° C. for 1 minute. This membrane was treated with 1% by weight of sodium carbonate and 0.3% of sodium dodecyl sulfate.
The reaction was stopped by immersion in an aqueous solution containing 5% by weight for 5 minutes, and then thoroughly washed with water. The membrane thus obtained was washed with hot water at 70 ° C. for 2 minutes, immersed in an aqueous solution having a chlorine concentration of 500 ppm and pH 7 for 2 minutes, and then stored in a 0.1% by weight aqueous solution of sodium bisulfite.

The composite semipermeable membrane thus obtained is subjected to a pH adjustment.
2 ppm humic acid adjusted to 6.5 was used as raw water.
As a result of a reverse osmosis test under the conditions of 3 MPa and 25 ° C., the amount of fresh water was 0.96 m ³ / m ² · day, and the removal rate of humic acid was 9
It was 9.81%. In _{addition, Na 2 SiO 3 · 9H 2} 0
An aqueous solution in which was dissolved so as to be equivalent to 30 ppm as SiO ₂ was used as raw water, and a reverse osmosis test was conducted under the same conditions as for humic acid. As a result, the transmittance of silica was 31.8%.
At this time, the maximum operable recovery rate is calculated.
5%.

The carboxyl group concentration determined by X-ray photoelectron spectroscopy (ESCA) was 0.018.

Comparative Example 2 In Comparative Example 1, trimesic acid chloride / trimellitic anhydride chloride was added to a decane solution containing m-phenylenediamine / piperazine = 60/40 molar ratio and trimesic acid chloride 0.06% by weight. A composite semipermeable membrane was produced in the same manner as in Comparative Example 1, except that trimellitic anhydride chloride was added so that the molar ratio became 85/15. The same evaluation as in Comparative Example 1 was performed using this composite semipermeable membrane, and the evaluation results are shown in Table 1.

Comparative Example 3 In Comparative Example 1, trimesic acid chloride / trimellitic anhydride chloride was added to a decane solution containing m-phenylenediamine / piperazine = 60/40 molar ratio and trimesic acid chloride 0.06% by weight. A composite semipermeable membrane was produced in the same manner as in Comparative Example 1 except that trimellitic anhydride chloride was added so that the molar ratio became 10/90. The same evaluation as in Comparative Example 1 was performed using this composite semipermeable membrane, and the evaluation results are shown in Table 1.

Example 1 m-phenylenediamine / piperazine = 15/85 molar ratio, trimesic acid chloride / trimellitic anhydride chloride = 50/50 in a decane solution containing trimesic acid chloride 0.06% by weight.
A composite semipermeable membrane was produced in the same manner as in Comparative Example 1 except that trimellitic anhydride chloride was added so as to have a molar ratio.

The composite semipermeable membrane obtained in this manner is adjusted to pH
2 ppm humic acid adjusted to 6.5 was used as raw water.
As a result of a reverse osmosis test under the conditions of 3 MPa and 25 ° C., the amount of fresh water was 1.46 m ³ / m ² · day, and the removal rate of humic acid was 9
It was 9.80%. In _{addition, Na 2 SiO 3 · 9H 2} 0
The aqueous solution obtained by dissolving to be 30ppm corresponds as SiO ₂ and the raw water, reverse osmosis test result under the same conditions as humic acid, the transmittance of the silica was 76.0%.
At this time, when the maximum operable recovery rate is calculated, 92.
6%.

The carboxyl group concentration determined by X-ray photoelectron spectroscopy (ESCA) was 0.022.

(Examples 2 to 5) In Example 1, m-
The molar ratio of phenylenediamine / piperazine and the molar ratio of trimesic acid chloride / trimellitic anhydride chloride were prepared with the compositions shown in Table 1 to prepare a composite semipermeable membrane. The same evaluation as in Comparative Example 1 was performed using this composite semipermeable membrane, and the evaluation results are shown in Table 1.

[0066]

[Table 1]

[0067]

According to the present invention, a composite semipermeable membrane having high water permeability can be obtained. By using this, contaminants and trace harmful substances contained in raw water can be selectively separated and removed. Recovery operation became possible.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4D006 GA05 HA41 HA61 KE05R KE07R KE12P KE13P KE15P KE16P KE30Q MA01 MA03 MA07 MA22 MA31 MA40 MB02 MB06 MB11 MB15 MB16 MC16 MC17 MC18 MC27 MC45 MC48 MC53 MC54 MC56X MC58 MC17 MC75 NA NA41 NA46 NA64 PA01 PB04 PB23 PB70 PC80

Claims (15)

[Claims] 1. A composite semipermeable membrane wherein a separation functional layer of a crosslinked polyamide is formed on a porous support membrane by polycondensation from a polyfunctional amine and a polyfunctional acid halide and a polyfunctional acid anhydride halide. , Operating pressure 0.3 MPa, temperature 25
The amount of permeated water at 0.8 ° C. and pH 6.5 is 0.8 to 4.0 m ^3.
/ M ² · day and a humic acid removal rate of 98% or more. 2. The composite semipermeable membrane according to claim 1, wherein the humic acid removal rate is 99% or more. 3. The composite semipermeable membrane according to claim 1, wherein the thickness of the separation function layer is in the range of 1 to 300 nm. 4. The composite according to claim 1, wherein the carboxyl group concentration in the separation functional layer analyzed by X-ray photoelectron spectroscopy (ESCA) is 0.02 or more and less than 0.06. Semi-permeable membrane. 5. The composite semipermeable membrane according to claim 1, wherein the porous support membrane contains at least one selected from the group consisting of polysulfone, polyamide, polyester and vinyl polymer. 6. When evaluated by circulating an aqueous solution having an operating pressure of 0.3 MPa, a temperature of 25 ° C., a silica concentration of 30 ppm and a pH of 6.5 for 3 hours, the silica transmittance is 55% or more and the amount of permeated water is 0.8 m ³ / The composite semipermeable membrane according to any one of claims 1 to 5, which has a m ² day or more. 7. The polyfunctional amine is a mixed amine of an aliphatic polyfunctional amine and an aromatic polyfunctional amine, wherein the aliphatic polyfunctional amine is a piperazine-based amine represented by the following general formula and a derivative thereof. The composite semipermeable membrane according to any one of claims 1 to 6, wherein the group III multifunctional amine is an amine selected from metaphenylenediamine, paraphenylenediamine, 1,3,5-triaminobenzene or an N-alkylated product thereof. . Embedded image R1~R8: H, OH, COOH, SO 3 H, NH 2 or an aliphatic group ranging number of 1 to 4 carbon atoms, 8. The polyfunctional acid halide is a polyfunctional acid chloride, and the polyfunctional anhydride halide is trimellitic anhydride halide represented by the following general formula and a derivative thereof. 8. The composite semipermeable membrane according to any one of items 1 to 7, Embedded image X1, X2: H, OH, COOH, SO ₃ H, COF,
COCl, COBr, COI, an aliphatic group having 1 to 3 carbon atoms or a group forming an acid anhydride X3: H, OH, COOH, SO ₃ H, COF, COC
l, COBr, COI, or an aliphatic group having 1 to 3 carbon atoms Y: F, Cl, Br or I 9. The composite semipermeable membrane according to claim 1, wherein the surface of the separation function layer has a projection having a substantially spherical point. 10. The ratio of the major axis / minor axis of the pointed end in a plan view is 1.0 to 2.0 in 70% or more of the total number of substantially spherical projections.
The composite semipermeable membrane according to claim 9, which is: 11. The porous support membrane contains at least one selected from the group consisting of polysulfone, polyamide, polyester and vinyl polymer.
The composite semipermeable membrane according to any one of the above. 12. A method for producing a composite semipermeable membrane comprising forming a separation functional layer of a crosslinked polyamide on a porous support membrane by polycondensation from a polyfunctional amine and a polyfunctional acid halide. A polyfunctional acid anhydride halide is present, and the polyfunctional amine contains an aliphatic polyfunctional amine and an aromatic polyfunctional amine, and the molar ratio thereof is 40 /
A method for producing a composite semipermeable membrane, which is in the range of 60 to 95/5. 13. The method for producing a composite semipermeable membrane according to claim 12, wherein the molar ratio between the polyfunctional acid halide and the polyfunctional anhydride halide is in the range of 75/25 to 15/85. 14. A method for producing fresh water, comprising separating a solid component in raw water using the composite semipermeable membrane according to claim 1. 15. The fresh water producing method according to claim 14, wherein the raw water is supplied to the composite semipermeable membrane at a pressure in the range of 0.1 to 3.0 MPa.