JP2002066278A - Titanium dioxide porous film, and method and apparatus for treating water using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method and apparatus using a titanium dioxide porous film, which requires no regular irradiation with ultraviolet rays, has durability and can decompose organic matter at a high level, capable of continuously removing organic matter by simple apparatus constitution and capable of simply regulating a permeation flux without washing the film. SOLUTION: Water treatment is performed using a titanium dioxide porous film which is a filter film wherein a film based on titanium dioxide is uniformly supported on the outer surface and/or inner surface of a filter base material and has a pore size of <4 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a porous titanium dioxide membrane, a water treatment method and a water treatment apparatus using the same. More specifically, the invention of this application provides a titanium dioxide porous membrane capable of decomposing organic substances to a high level, and a simple apparatus configuration and continuous removal of organic substances using the same without the need to constantly irradiate ultraviolet rays. Possible,
Further, the present invention provides a water treatment method and a water treatment apparatus without cleaning the membrane.

[0002]

2. Description of the Related Art Pollution of rivers by substances that may harm health, such as pesticides, trihalomethanes, and trichloroethylene, has often been taken up as a familiar topic. Therefore, in order to remove these harmful organic substances, techniques for detoxifying harmful organic substances using titanium dioxide having photocatalytic activity have been studied.

As a water detoxification treatment technique using titanium dioxide, for example, a water treatment technique using a titanium oxide porous thin film catalyst disclosed in Japanese Patent No. 4263615 is known. This water treatment technique has a thickness of 0.3-0.
A titanium dioxide film having a pore size of 8 to 10 nm and a pore diameter of 10 to 1200 nm is formed on the surface of a quartz glass plate, immersed in water to be treated, and irradiated with ultraviolet light to decompose trimethylamine, tetrachloroethylene, trichloroethylene, acetic acid, etc. in the aqueous solution. It is made possible. According to this water treatment technique, titanium dioxide exhibiting photocatalytic activity is not suspended as particles in the water to be treated, so that there is an advantage that it is not necessary to collect the particles from the treated water. However, this water treatment technology does not filter the water to be treated with a titanium dioxide film, but performs the treatment by contacting the titanium dioxide film, which is a photocatalyst, with the water to be treated. There is a problem that it cannot be separated, is not suitable for a continuous processing process, and has a low processing efficiency.

On the other hand, a water treatment technique using titanium dioxide and utilizing a filtration action has been proposed (for example, Japanese Patent Application Laid-Open No. 9-8 / 1997).
No. 5058).

[0005] In this water treatment technique, a hydrophilic material and a photocatalyst (such as titanium dioxide) are simultaneously supported and exposed on a filtration substrate made of a porous membrane, and the water to be treated is filtered while irradiating with ultraviolet rays. This technology decomposes harmful organic substances. However, in this water treatment technology, since the organic polymer compound is used as the hydrophilic material and the photocatalyst is used as an adhesive, the photocatalyst oxidizes the hydrophilic material and deteriorates the filter material. There is a problem. In addition, in order to decompose harmful organic substances, there are problems that a long-time circulation filtration is required, that it is necessary to constantly irradiate ultraviolet rays, that a large amount of operating power is required for a water treatment apparatus, and the like. .

[0006] In the water treatment method using a filtration membrane having micropores, clogging has been conventionally pointed out. If the pores of the filtration membrane are micropores, a clogging substance adheres to the membrane surface or the pores, hinders the permeation of the solvent, and reduces the permeation flux. Therefore, in order to recover the permeation flux, conventionally, washing of the membrane with an acid or alkali, washing with an enzyme detergent, or the like, or applying a reverse pressure from the permeation side to remove deposits in the pores and on the surface. A membrane washing step such as back washing is indispensable. That is, filtration using a filtration membrane having fine pores requires labor and time for washing the membrane.

Therefore, the invention of this application has been made in view of the circumstances described above, and solves the problems of the prior art, which eliminates the need to constantly irradiate ultraviolet rays, has durability, and has an organic material. Titanium dioxide porous membrane capable of decomposing to a high level, and using it, a simple equipment configuration and continuous removal of organic substances are possible.Furthermore, it is possible to easily adjust the permeation flux without washing the membrane. It is an object to provide a possible water treatment method and a water treatment device.

[0008]

Means for Solving the Problems The invention of this application provides the following inventions to solve the above problems.

That is, first, a filtration membrane having titanium dioxide as a main component is uniformly supported on the outer surface and / or inner surface of the filtration substrate, and the pore diameter of the membrane is 4 nm.
And providing a titanium dioxide porous membrane, characterized in that:

Secondly, the invention of the present application provides a titanium dioxide porous membrane according to the first invention, wherein the pore diameter of the membrane is 1.1 nm or less. Provided is a porous titanium dioxide membrane, wherein the pore diameter of the membrane is 0.8 nm or less.

Fourthly, the invention of this application is directed to a filtrate from which organic substances have been removed by passing water to be treated through the titanium dioxide porous membrane according to any one of the first to third aspects. And a water treatment method characterized by obtaining

Fifthly, the invention of this application is directed to a water treatment method according to the fourth invention, wherein water is passed while irradiating the titanium dioxide porous membrane with ultraviolet rays. A water treatment method characterized by changing the membrane permeation flux of the water to be treated by irradiating the titanium dioxide porous membrane with ultraviolet rays. Seventh, the irradiation of ultraviolet rays is performed as necessary. A water treatment method is provided.

On the other hand, eighthly, the invention of this application is an apparatus for performing the water treatment method according to any one of the fourth to seventh aspects, wherein the apparatus comprises a water tank for storing water to be treated. A titanium dioxide porous membrane provided in a water tank to be treated, a stirring means for stirring the water to be treated, a collecting chamber connected to the titanium dioxide porous membrane, and an ultraviolet ray applied to the titanium dioxide porous membrane. A filtrate having an ultraviolet irradiation means for irradiating, and a liquid sending means for sending the water to be treated, wherein the organic substance is removed by passing the water to be treated through the titanium dioxide porous membrane by the liquid sending means while controlling the irradiation of ultraviolet rays The water treatment apparatus is characterized in that the water is collected in a collecting room.

Ninth, the present invention provides a water treatment apparatus according to the eighth aspect, wherein the liquid sending means is a suction pump for generating a suction pressure in the collecting chamber. Tenthly, the present invention also provides a water treatment apparatus, wherein the stirring means is a diffuser for diffusing gas into the water to be treated.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION The invention of this application has the features as described above, and the embodiments will be described in detail below.

First, the titanium dioxide porous membrane of the first invention of this application is a filtration membrane containing titanium dioxide as a main component, which is used by being uniformly supported on the outer surface and / or inner surface of a filtration substrate. , Characterized in that the pore diameter of the membrane is less than 4 nm.

The titanium dioxide porous membrane of the present invention has a pore diameter of less than 4 nm and exhibits high photocatalytic activity because a quantum size effect can be obtained.
It has the characteristic that the smaller the pore size is, the more efficiently it is exhibited. Titanium dioxide porous membrane is made of titanium dioxide (Ti
It may have a single composition of only O ₂ ), or may contain a trace element for enhancing photocatalytic activity. Also, the titanium dioxide porous membrane of the invention of the present application surprisingly has the ability to inhibit organic substances at the same level or higher than the decomposition of organic substances by a conventionally known photocatalyst without irradiation with ultraviolet rays. Have. In the conventionally known decomposition and removal of low-molecular-weight organic substances by titanium dioxide, irradiation with ultraviolet rays is indispensable, and the titanium dioxide porous membrane of the invention of the present application has a fine, previously unknown microscopic structure. It is intended to provide a new use of a porous titanium dioxide membrane having pores.

The titanium dioxide porous membrane of the invention of this application is, of course,
Organic substances passing through the pores of the filtration membrane can also be decomposed. In this case, the organic substances can decompose not only low-molecular-weight organic substances that have been conventionally targeted for decomposition removal but also high-molecular-weight organic substances. Furthermore, organic substances (fouling substances) that have clogged the pores by filtration can also be decomposed. This makes it possible to decompose fouling substances and recover the permeation flux of the filtration membrane without the need for a washing step such as washing or backwashing of the filtration membrane, which is indispensable in the prior art. Is what you do.

As described above, the titanium dioxide porous membrane of the invention of the present application has been known in the prior art, for example, for inhibiting organic substances, decomposing organic substances at a high level during filtration, and recovering permeation flux by photocatalytic activity. A specific phenomenon that has not been realized is realized. It is thought that these phenomena are not independent actions, but are different degrees of the phenomena inherent in the provision of microscopic pores at the molecular level in a filtration membrane having photocatalytic activity. Can be Therefore, in this application, the upper limit of the pore diameter of the titanium dioxide porous membrane was set to 4 nm, which is the upper limit of the average pore diameter of the titanium dioxide porous membrane in which the above phenomenon was actually confirmed.

The pore size of the titanium dioxide porous membrane of the invention of this application can be appropriately adjusted according to the molecular weight of the substance to be inhibited or decomposed.

For example, when filtering a solution containing trichloroethylene (TCE), which is a low molecular organic substance, the average pore diameter of the titanium dioxide porous membrane is preferably 0.8 nm or less. In addition, when filtering high molecular organic substances, clogging is likely to occur. Therefore, for example, when decomposing polyethyleneimine (PEI) having a molecular weight of about 1800, it is preferable that the titanium dioxide porous membrane has an average pore diameter of 1.1 nm or less and is filtered while being irradiated with ultraviolet rays. Further, the lower limit of the pore diameter may be within a range that allows a solvent such as water to pass through.

Regarding the pore size distribution, it is preferable that the dispersion of the pore size is small and the pore size is as uniform as possible in order to maximize the various properties of the titanium dioxide porous membrane. Then, a plurality of titanium dioxide porous films having different average pore sizes may be used in combination, or a multilayer film of titanium dioxide porous films having different average pore sizes may be used.

The titanium dioxide porous membrane of the invention of the present application as described above is provided on the outer surface and / or inner surface of a filtration substrate.
The titanium dioxide porous membrane having a pore diameter of less than 4 nm is uniformly supported.

The shape of the filtration substrate is not particularly limited as long as it is a porous material having a mean pore diameter of about 1 μm, which is made of a material generally used as a filtering device. For example, it is shown as a preferable example to use an inorganic material such as α-alumina or mullite having a transmission hole having an average pore diameter of about 1 μm. Above all, it is preferable to use α-alumina from the viewpoint that the strength is high and the base treatment can be easily performed. The shape can be any shape such as a tubular shape (outer diameter of about 1 cm or more), a capillary shape (outer diameter of about 1 to 10 mm), a monolithic shape (multi-hole integrated type), a flat plate shape, and the like.

The titanium dioxide porous membrane is preferably applied directly to the above-mentioned filtration substrate by a sol-gel method or a CVD method. Since the titanium dioxide porous membrane of the invention of this application preferably makes the pore diameter as uniform as possible, it is shown as a more preferable example to produce a filtration membrane using a sol-gel method in which the pore diameter is easily controlled. . In the sol-gel method, the pore diameter of the titanium dioxide porous membrane can be controlled by adjusting the particle size of the colloid sol. The particle size of the colloid sol can be controlled by the condensation polymerization reaction temperature when adjusting the colloid solution.

The titanium dioxide porous membrane varies depending on the shape of the filtration substrate, but can be formed on the outer surface, the inner surface, or both the inner and outer surfaces of the filtration substrate. Furthermore, the separation of organic substances and the decomposition of polymer deposits may be handled by one porous membrane, or a plurality of membranes formed by different methods on different surfaces of a filtration substrate or another substrate. May be used.

As a result, an organic substance can be separated, and a titanium dioxide porous membrane capable of decomposing the organic substance to a high level by irradiating ultraviolet rays can be obtained. Also,
The titanium dioxide porous membrane of the invention of this application is entirely composed of an inorganic material, and can have higher durability than an organic polymer membrane.

According to the water treatment method of the fourth invention of this application, the organic matter is removed by passing the water to be treated through the titanium dioxide porous membrane of any of the first to third inventions. To obtain the filtrate.

As described above, the titanium dioxide porous membrane of the invention of the present application can obtain a filtrate from which organic substances have been removed to a high level by a single filtration.

Further, since the water treatment method of the present invention is a water treatment method by filtration, it is not necessary to recover the photocatalytically active substance, and the water before treatment and the water after treatment are separated, and continuous water treatment is performed. Can be used for processing processes.

As a result, the organic matter contained in the water to be treated can be removed only by filtration, and a continuous treatment process can be performed, thereby realizing an efficient water treatment method.

The water treatment method according to the fifth aspect of the present invention is characterized in that, in the fourth aspect, water is passed while irradiating the titanium dioxide porous membrane with ultraviolet rays.

[0033] In the water treatment method of the fourth invention,
As the water treatment progresses, it is conceivable that filtered low-molecular-weight organic matter accumulates in the pores. If the water to be treated contains a large amount of high-molecular-weight organic matter, the titanium dioxide porous membrane is targeted by the high-molecular-weight organic matter. It is possible to cause clogging. In such a case, the membrane permeation flux of the water to be treated is reduced, so that efficient water treatment cannot be performed.

Therefore, by passing water through the titanium dioxide porous membrane while irradiating it with ultraviolet rays, it is possible to decompose organic substances passing through the pores, and to obtain a filtrate from which permeated organic substances are decomposed and removed. Can be. In addition, it becomes possible to decompose organic substances clogging the surface of the titanium dioxide porous membrane by irradiation with ultraviolet rays.

Thus, a water treatment method capable of not only inhibiting organic substances but also decomposing and removing the organic substances and maintaining a high membrane permeation flux is realized.

The water treatment method according to a sixth aspect of the present invention is the water treatment method according to the fifth aspect, wherein the titanium dioxide porous membrane is irradiated with ultraviolet rays so as to change the membrane permeation flux of the water to be treated. I have.

By irradiating the titanium dioxide porous membrane with ultraviolet rays, not only can low-molecular organic substances accumulated in the pores and clogged high-molecular organic substances be decomposed,
It is also possible to control the membrane flux of the water to be treated. The membrane permeation flux of the water to be treated can be controlled to a desired value by the irradiation amount of the ultraviolet rays to the titanium dioxide porous membrane.

As a result, it is possible to realize an efficient water treatment method in which the membrane permeation flow rate is controlled without requiring a filtration membrane washing step which has been indispensable in the past.

A water treatment method according to a seventh aspect of the present invention provides the water treatment method according to any one of the fourth to sixth aspects, wherein irradiation of ultraviolet rays is performed as needed. .

In the water treatment method of the present invention,
Organic substances can be removed without irradiation with ultraviolet rays. Therefore, there is no need to constantly irradiate ultraviolet light,
Irradiation can be performed as needed. For example, when the membrane permeation flux becomes extremely low due to the clogging of organic substances, the titanium dioxide porous membrane can be irradiated with ultraviolet rays to completely decompose and remove the clogged organic substances, By controlling / OFF frequently, a constant permeation flow rate can be maintained. That is, the membrane permeation flux of the water to be treated can be freely controlled by ON / OFF of the ultraviolet irradiation.

This realizes a low-cost water treatment method that does not always require irradiation with ultraviolet rays.

The water treatment apparatus according to an eighth aspect of the present invention is an apparatus for performing the water treatment method according to any one of the fourth to seventh aspects, wherein a water tank for storing the water to be treated, A titanium dioxide nanofiltration membrane provided in the water tank,
Stirring means for stirring the water to be treated, a collecting chamber connected to the titanium dioxide nanofiltration membrane, ultraviolet irradiation means for irradiating ultraviolet rays to the titanium dioxide nanofiltration membrane, and a liquid sending means for sending the water to be treated The method is characterized in that the water to be treated is passed through the titanium dioxide nanofiltration membrane by the liquid sending means while controlling the irradiation of ultraviolet rays, and the filtrate from which organic substances have been removed is collected in the collecting chamber. Such a water treatment apparatus of the invention of this application is realized, for example, as an immersion filtration apparatus illustrated in FIG.

In FIG. 1, 1 is a water tank to be treated, 2 is water to be treated, 3 is a filtration material made of titanium dioxide multi-hard film,
Is a collecting chamber for collecting filtered water, 5 is a suction pump as liquid sending means, 6 is an ultraviolet lamp as ultraviolet irradiation means, 7 is an air diffuser as stirring means, and 8 is an air feed pump for sending gas to the air diffuser. , 9 are holders.

For example, two filter media (3) are fixed at one end to the holder (9), and the other end is connected to the collecting chamber (4) and installed on the bottom surface of the water tank (1). Have been.
An ultraviolet lamp (6) is also provided in parallel with the filter medium (3). The to-be-treated water tank (1) is filled with the to-be-treated water (2), and the to-be-treated water (2) is constantly stirred by the bubbles discharged from the air diffuser (7).

When a suction pressure is generated in the collecting chamber (4) by the suction pump (5), the difference between the head pressure of the water to be treated (2) and the suction pressure becomes the transmembrane pressure of the filtration material (3). Thus, the water to be treated (2) passes through the filter medium (3) and is sent to the collecting chamber (4) as a filtrate from which organic substances have been removed, and can be collected. At this time, the organic matter in the water to be treated (2) is blocked on the surface of the filter medium (3). As a result, a filtrate from which organic substances have been removed to a high level can be obtained.

According to this method, the water to be treated (2)
And the filtrate are separated, so if it is necessary to further reduce the concentration of the organic matter in the filtrate sent to the collecting chamber (4), it is again passed through a similar filtration device (not shown) arranged in series. Filtration can also be performed. Thus, the water to be treated can be treated continuously, and the treatment process is simplified.

Further, the surface of the filter medium (3) is irradiated with ultraviolet rays by an ultraviolet lamp (6) to enhance the photocatalytic activity of the filter medium (3), so that the low molecular weight organic substances passing through the filter medium (3). Can also be decomposed. Furthermore, high molecular organic substances on the surface of the filter medium (3) can be decomposed.
Thereby, a permeation flux can be controlled, and a water treatment method that does not require membrane cleaning is realized.

As an ultraviolet irradiation means, a black light as an ultraviolet lamp (6) is often used, but a mercury lamp, a xenon lamp or the like can also be used. Further, the ultraviolet irradiation means may be installed outside the water tank to be treated (1) instead of in the tank to be treated. For example, it is possible to irradiate the surface of the filtering material (3) with ultraviolet light guided through an optical fiber or the like. is there. Irradiation of ultraviolet rays to the filter medium (3) may be performed at all times, but control such as irradiation may be performed as necessary. Thereby, low-cost water treatment is realized.

In FIG. 1, the to-be-treated water tank (1) is an open system, but may be a closed system. Alternatively, the collecting chamber (4) may be provided outside the to-be-treated water tank (1). May be provided. The shape and number of the filter medium (3) are also optional.

Of course, the liquid feeding device is not limited to the suction pump (5), but various types such as a pressurized type can be used, and the stirring device is also provided with the air diffuser (7) and the air feeding pump (8). Without limitation, various types such as a stirring type may be used.

Hereinafter, embodiments will be described with reference to the accompanying drawings, and embodiments of the present invention will be described in more detail.

[0052]

EXAMPLES (Example 1) A filter medium using the titanium dioxide porous membrane of the present invention was prepared. The filtering material has a cylindrical shape, and is composed of a filtering portion and connecting portions at both ends thereof. A glass tube for piping was used for the connection part. The filtration unit uses an α-alumina porous tube having an outer diameter of 10 mm, a wall thickness of 1 mm, a length of 9 cm and an average pore diameter of 1 μm as a filtration base material, and a titanium dioxide porous membrane on the outer surface of which is a sol-gel. It was produced as follows by the method.

Titanium isopropoxide (TTIP), isopropyl alcohol (IPA), hydrochloric acid (HCl) and water (H ₂ O) were prepared as raw materials of the titanium dioxide porous membrane, and their molar ratio was TTIP / IPA. / HCl
/ H ₂ O = 1/140 / 0.4 / 4. The solution is left at 5 ° C. for 1 hour to hydrolyze,
Further, the mixture was stirred at a predetermined aging temperature for 10 hours to cause a condensation polymerization reaction to obtain a titanium dioxide colloid sol.

This titanium dioxide colloidal sol is coated on an α-alumina porous tube as a filtration substrate, dried, and then baked at a predetermined calcination temperature for 15 minutes or more to form a porous titanium dioxide porous membrane 1. To 3 were completed to complete the filter material.

The average pore diameter and the molecular weight cut-off of the obtained titanium dioxide porous membranes 1 to 3 were measured, and the results are shown in Table 1 together with the preparation conditions.

[0056]

[Table 1]

Here, the average pore diameter was determined from a humid air permeation experiment using the Kelvin capillary condensation method. The molecular weight cutoff is an index used to evaluate the performance of a filtration membrane, and is the molecular weight of a solute in a solution having an apparent rejection of 0.9 when filtration is performed using the membrane. expressed. The molecular weight cutoff was determined by filtering a solution using sugars having different molecular weights as solutes through the titanium dioxide porous membranes 1 to 3.

From Table 1, it was confirmed that a titanium dioxide porous membrane having a pore diameter of 4 nm or less was produced. In addition, it was shown that the average pore diameter can be controlled by the preparation conditions of the titanium dioxide porous membrane, and can be selected according to the organic substance to be filtered. (Example 2) A filtration device A equipped with a filtration material having the titanium dioxide porous membrane 1 produced in Example 1 was produced, and treated water containing four kinds of low molecular organic substances of trichloroethylene, benzene, toluene and xylene was prepared. Was filtered. FIG. 2 schematically shows the filtering device A.

The filtration device A is a batch type filtration device,
In a constant temperature water bath (10) set at 35 ° C., two transparent closed cylindrical containers, a reservoir tank (15) and a permeation experiment cell (16), are installed in series. The reservoir tank (15) is filled with nitrogen gas for pressurization in an N ₂ cylinder (1).
1), the nitrogen gas pressure in the reservoir tank (15) can be controlled by a pressure regulating valve (12), a pressure gauge (13), and a leak valve (14). The permeation experiment cell (16) is filled with the water to be treated, and a filter medium (17) having the titanium dioxide porous membrane 1 is arranged in the center thereof. The water to be treated in the permeation experiment cell (16) permeates the filter medium (17) by the transmembrane pressure difference set between the pressurization with nitrogen and the permeate pressure, and the permeate filtrate (1).
Collected as 9). The cell for permeation experiments (16)
In order to eliminate the influence of concentration polarization, a 35 mm stirrer was rotated at 900 rpm to mix sufficiently to the surface of the filter.

In the apparatus having such a configuration, trichloroethylene, benzene, toluene,
The four kinds of low molecular organic substances of xylene were adjusted to about 500 ppm, and the respective water to be treated was filtered. The concentration (Cb) of the water to be treated to be supplied to the filter medium and the concentration (C
p) and the permeation flow velocity of the water to be treated were measured. The measurement of the concentration of the low molecular weight organic substance was performed by gas chromatography. Also, 1-Cp / Cb values were obtained as the rejection ratio R, and the results are shown in Table 2.

[0061]

[Table 2]

From Table 2, it can be seen that the titanium dioxide porous membrane 1 of the invention of the present application shows that the titanium dioxide porous membrane 1 of trichloroethylene, benzene, toluene and xylene can be used even without irradiation of ultraviolet rays.
It was confirmed that various kinds of low molecular organic substances can be separated with a rejection of about 20 to 30%. (Example 3) A filtration device B using a filtration material having the titanium dioxide porous membrane 3 produced in Example 1 was produced, and a trichlorethylene solution was filtered as water to be treated. FIG. 3 schematically shows the filtering device B.

The filtration device B is a flow-type filtration device.
The water to be treated (2) stored in the supply liquid tank (20) is
The liquid is supplied to the transparent test cell housing (22) provided with the filter medium (17) by the gear pump (21), and only the liquid that has passed through the filter medium (17) is collected as the membrane-permeable filtrate (19). Further, a black light (4 W × 2 lines) (23) having a main wavelength of 350 nm is provided outside the test cell housing (22) so that the filter medium (17) can be irradiated with ultraviolet rays when necessary. Gear pump (2
The flow rate of the water to be treated (2) supplied from 1) is a float type flow meter, and the pressure (P1) on the upstream side and the pressure (P2) on the downstream side of the filter are measured by a pressure gauge (13).
The pressure of the water to be treated (2) is controlled by the flow rate and the pressure regulating valve (12), the transmembrane thickness is 0.1 kgf / cm ² , and the permeation flux is 1.5 × 10 ⁻⁶ m ³ / m ^2.・ It is set to be s. The temperature of the water to be treated (2) was 25 ° C.

In the device B having such a configuration, first,
Filtration treatment of the water to be treated without irradiating ultraviolet rays, and then irradiating with ultraviolet rays and performing filtration treatment were repeated twice, and the change in the concentration of trichlorethylene before and after each treatment was measured. The results are shown in Table 3 together with the rejection R. In addition, the reason why the concentration of trichlorethylene (Cb) on the supply side is reduced in each filtration process is considered to be that trichlorethylene has volatilized during each filtration process, but trichlorethylene volatilization during the filtration process is scarce. Make sure that.

[0065]

[Table 3]

When no ultraviolet ray was irradiated, the concentration of trichlorethylene did not change before and after filtration. This is because the molecular weight cut off of the titanium dioxide porous membrane 3 used as the filter material is 3
This is because it was too large compared to the molecular weight 131 of trichlorethylene, and the filtration effect was not measured. That is, it was confirmed that the titanium dioxide porous membrane 3 was not suitable for removing trichloroethylene by filtration.

On the other hand, when ultraviolet light was irradiated, it was found that the concentration of trichlorethylene was reduced by 5 to 10 ppm each time the titanium dioxide porous membrane 3 was passed.

From this, it was found that trichloroethylene was decomposed while passing through the porous titanium dioxide membrane 3. The thickness of the titanium dioxide porous membrane 3 used here is about 1 μm, and the permeation flux is 1.5 × 10 ⁻⁶ m ³ /
Calculated from m ² · s, it was found that about 20% of trichlorethylene was decomposed in about 1 second after passing through the titanium dioxide porous membrane.

In the conventional trichlorethylene decomposition technology using titanium, it takes 15 minutes to 10 days to reduce the initial concentration of 500 ppm of trichlorethylene to 5 ppm, and the water treatment method of the invention of the present application efficiently and at a high level. It has been shown that trichlorethylene can be decomposed. (Example 4) Water to be treated containing a high-molecular-weight organic material that is likely to cause clogging was treated. Water treatment was performed using polyethyleneimine (PEI) having a molecular weight of 1800 as a high molecular weight organic material and using a PEI solution adjusted to 100 ppm. For filtration, a batch type filtration device (filtration device A) or a flow type filtration device (filtration device B) provided with the titanium dioxide porous membrane 1 or 2 prepared in Example 1 was used.
With the transmembrane pressure kept constant at 0.2 or 10 kgf / cm ² , ultraviolet light was turned on and off and the change in the permeation flux was measured.

The measurement of the permeation flow rate was first performed on pure water filtered without irradiating ultraviolet rays, then on the PEI solution, and then on the PEI solution filtered while irradiating ultraviolet rays. For comparison, a change in the permeation flow rate was examined in the same manner even when a Si-Zr film, which does not exhibit photocatalytic activity, was used. Table 4 shows the measurement results.

[0071]

[Table 4]

In the case where the titanium dioxide porous membrane 1 or 2 is used, when the PEI solution is passed, the permeation flux is extremely reduced as compared with the case where pure water is passed. Therefore, the permeation flow rate is about 1 when pure water is passed through.
It was confirmed to recover to about / 2. Although not shown in the table, when the irradiation of the ultraviolet rays was stopped again, P
It was also confirmed that the permeation flux of the EI solution was reduced.

The Si-Zr film having no photocatalytic function showed no recovery of the transmitted flux even when irradiated with ultraviolet rays.

From the above, it was confirmed that the water treatment method of the invention of the present application can decompose and remove high molecular organic matter in the water to be treated. It was also confirmed that the permeation flux of the water to be treated can be controlled. According to this water treatment method, high-molecular organic matter can be decomposed by irradiating ultraviolet rays only when necessary, and it has been shown that energy-saving water treatment can be realized.

Of course, the present invention is not limited to the above-described example, and it goes without saying that various embodiments are possible in detail.

[0076]

As described in detail above, according to the present invention, there is no need to constantly irradiate ultraviolet rays, and a titanium dioxide porous membrane capable of decomposing organic substances to a high level without impairing durability, and using the same, Provided are a water treatment method and a water treatment method which have a simple apparatus configuration, can continuously remove organic substances, and can easily adjust a permeation flux without washing a membrane.

[Brief description of the drawings]

FIG. 1 is a schematic view illustrating a immersion-type filtration device to which a water treatment method of the present invention is applied.

FIG. 2 is a schematic view illustrating a batch type filtration device used in Examples.

FIG. 3 is a schematic view illustrating a flow-type filtration device used in Examples.

[Explanation of symbols]

1 treated water tank 2 water to be treated 3 filtering material 4 collecting chamber 5 the suction pump 6 ultraviolet lamp 7 aeration tube 8 air pump 9 holding member 10 constant temperature water bath 11 N ₂ gas cylinder 12 pressure regulating valve 13 pressure gauge 14 leak valve 15 reservoir Tank 16 Cell for permeation experiment 17 Filtration material 18 Stirrer 19 Membrane permeate filtrate 20 Water tank 21 Gear pump 22 Test cell housing 23 Black light

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C02F 1/32 ZAB C02F 1/32 ZAB 1/58 1/58 A (72) Inventor Terutaka Toyada Hiroshima Prefecture 7247-1, Saijomachiji, Higashihiroshima-shi Haru Haren D Bldg. No. 202 F-term (reference) 4D006 GA06 HA01 HA21 HA41 JA31A JA53A KA31 KA43 KB04 KC22 KD30 KE03Q KE03R KE12Q KE12R KE13Q KE13R KE16Q KE16R MA03 MA22 MA03 NA03 MC03 NA03 AA11 AB02 AB14 BA18 BB04 BB05 CA03 4D038 AA08 AB07 AB14 BB07 BB09 4G069 AA03 AA08 BA01A BA01B BA04A BA04B BA13A BA48A CA05 CA19 EA08 EB14Y EC11X EC12X EC12Y EC13X EC13Y FA03 FB23 FB30

Claims (10)

[Claims] 1. A filtration membrane in which a membrane containing titanium dioxide as a main component is uniformly supported on an outer surface and / or an inner surface of a filtration substrate, wherein the pore diameter of the membrane is less than 4 nm. Titanium dioxide porous membrane. 2. The titanium dioxide porous membrane according to claim 1, wherein the pore diameter of the membrane is 1.1 nm or less. 3. The titanium dioxide porous membrane according to claim 1, wherein the pore diameter of the membrane is 0.8 nm or less. 4. A water treatment method comprising passing a water to be treated through the titanium dioxide porous membrane according to claim 1 to obtain a filtrate from which organic substances have been removed. 5. The water treatment method according to claim 4, wherein water is passed while irradiating the titanium dioxide porous membrane with ultraviolet rays. 6. The water treatment method according to claim 5, wherein the membrane permeation flux of the water to be treated is changed by irradiating the titanium dioxide porous membrane with ultraviolet rays. 7. The water treatment method according to claim 5, wherein the ultraviolet irradiation is performed as needed. 8. An apparatus for performing the water treatment method according to claim 4, wherein a water tank to be filled with water to be treated and a titanium dioxide porous membrane provided in the water tank to be treated. A stirring means for stirring the water to be treated; a collecting chamber connected to the titanium dioxide porous membrane; an ultraviolet irradiation means for irradiating the titanium dioxide porous membrane with ultraviolet light; A water treatment apparatus, comprising: a liquid means, and a filtrate from which organic substances are removed by passing water to be treated through a titanium dioxide porous membrane by a liquid sending means while controlling the irradiation of ultraviolet rays. 9. The water treatment apparatus according to claim 8, wherein the liquid sending means is a suction pump for generating a suction pressure in the collection chamber. 10. The agitation means is an air diffuser for diffusing gas into the water to be treated.
A water treatment apparatus as described in the above.