JP2012071301A - Filtration filter and method for manufacturing the same, and filtration device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: a filtration filter with a small diameter of a micropore to a degree usable as a seawater filtration filter and with high chemical and heat resistance; a method for manufacturing the filtration filter; and a filtration device using the filtration filter.SOLUTION: The filtration filter includes: a porous body having a plurality of micropores; a surface to which the micropores of the porous body are open; and an oxide film formed along the surface shape of a microscopic area of the porous body so as to cover at least one part of an inner wall of the micropores.

Description

  The present invention relates to a filtration filter, a method for producing the filtration filter, and a filtration device, and more particularly, to a filtration filter that can be used as a seawater filtration filter, a method for producing the filtration filter, and a filtration device using the filtration filter.

  Conventionally, a columnar filtration membrane (also referred to as a reverse osmosis membrane or an RO membrane) made of an organic substance is known as a seawater filtration filter for desalinating seawater. The filtration membrane has many irregular fine pores having a diameter of, for example, 1 nm or less, and desalinates seawater by separating water molecules from sodium ions and the like contained in the seawater. There are various types of filtration membranes, and they are properly used depending on the application. Examples of the filter membrane that can be used as a seawater filter include those described in Non-Patent Document 1.

  In FIG. 8, the schematic diagram of the filtration apparatus using a column-shaped filtration membrane is shown. The cylindrical filtration membrane includes a tube-type cylindrical filtration membrane 1A (see FIG. 1A) having a single hollow space penetrating in the axial direction, and a monolithic type having a plurality of hollow spaces penetrating in the axial direction. There is a cylindrical filtration membrane 1B (see FIG. 1B). As shown in FIG. 8 (A), in the filtration device 2A using the tube-type cylindrical filtration membrane 1A, the stock solution (seawater) is sent around the outer peripheral wall of the cylindrical filtration membrane 1A, Collect the exuded filtrate (fresh water). On the other hand, as shown in FIG. 8B, in the filtration device 2B using the monolithic cylindrical filtration membrane 1B, the stock solution is sent into each hollow space of the cylindrical filtration membrane 1B, and the outer periphery of the cylindrical filtration membrane 1B. Collect the filtrate that exudes from the wall.

  However, although the filter using the filter membrane made of organic matter has been improved in recent years, it cannot be said that it still has sufficient chemical resistance and heat resistance, and it is compared for reasons such as clogging. Therefore, there is a problem that a sufficient amount of filtrate cannot be recovered unless it is frequently changed.

  By the way, as a filter, what used the filter membrane which consists of said organic substances, the filter membrane which consists of inorganic substances, such as ceramic and aluminum oxide, and the mesoporous substrate which has porous structures, such as porous alumina, are also known. (For example, refer to Patent Document 1). These are characterized by higher chemical resistance, salt resistance and heat resistance than the above-mentioned filtration membranes made of organic matter. In addition, filtration membranes made of inorganic substances are classified into ultrafiltration membranes (UF membranes), nanofilter membranes (NF membranes), and microfilter membranes (MF membranes) according to the diameter of the micropores.

  However, filter membranes and mesoporous substrates made of inorganic substances are very difficult to reduce the diameter of the micropores to 1 nm or less, so that they cannot be used as a seawater filter at present.

  In addition, as for the filter membrane made of an inorganic material, in Patent Document 2, a deposited layer of titania ultrafine particles is formed on the surface of an alumina porous tube, and this deposited layer is further baked at a high temperature of 1200 ° C. for 2 hours. What is formed by forming a sintered layer (titania layer) of about 70 μm is disclosed. However, since this filtration membrane is very difficult to control the diameter of the micropores in the titania layer, the diameter is too small and the water permeation pressure (pressure to be applied to the stock solution when the stock solution is fed) becomes large. In some cases, the diameter is too large to provide sufficient filtration performance, and it is difficult to use as a seawater filtration filter. In addition, this filtration membrane has a problem that the production cost is high because it is necessary to form a titania layer by baking at a high temperature exceeding 1000 ° C. for a long time.

“Toyobo's water-related business: Holocep HB series, HJ”, [online], search on September 2, 2011, Internet <URL: http://www.toyobo.co.jp/seihin/h2/mb/HB -series.htm>

JP-A-2005-272886 JP-A-5-85855

  The present invention has been made in view of the above circumstances, and the problem is that the diameter of the micropores is small enough to be used as a seawater filtration filter, and the control of the micropore diameter is easy. An object of the present invention is to provide a filtration filter, a method for producing the filtration filter, and a filtration apparatus using the filtration filter, which have high chemical properties and heat resistance and are inexpensive.

  In order to solve the above problems, a filtration filter according to the present invention covers a porous body having a plurality of micropores, a surface where the micropores of the porous body are open, and at least a part of an inner wall of the micropores. Thus, an oxide film formed along the surface shape of the fine region of the porous body is provided.

  In the filtration filter, it is preferable that the maximum diameter of the micropores after the oxide film is formed is smaller than the diameter of sodium hydrate contained in seawater. Such a filtration filter can be used as a seawater filtration filter.

  Examples of the oxide film include single-composition oxide films of titanium, gallium, iron, chromium, aluminum, magnesium, zirconium, indium, tin, vanadium, or silicon, or mixed crystal oxide films thereof.

  The oxide film can be formed by, for example, a mist CVD method. According to the mist CVD method, an oxide film having a uniform thickness along the surface shape of the fine region of the porous body can be manufactured at low cost.

  As the porous body, for example, a cylindrical filtration membrane having at least one hollow space penetrating in the axial direction can be used. In this case, an oxide film may be formed on at least one of the outer peripheral wall and the inner peripheral wall of the cylindrical filtration membrane.

  As the porous body, a mesoporous substrate in which fine holes penetrating in the thickness direction are arranged in a plane can also be used. In this case, an oxide film may be formed on at least one surface of the mesoporous substrate.

  In order to solve the above problems, a method for manufacturing a filtration filter according to the present invention includes a temperature raising step for raising a temperature of a film forming chamber in which a porous body having a plurality of micropores is disposed, and a solution is vibrated. A mist generating step for generating mist, and introducing the mist into the film forming chamber after the temperature rise, causing a CVD reaction on the surface of the porous body where the micropores are opened, and the above-mentioned surface and the inner wall of the micropore And a film forming step of forming an oxide film along the surface shape of the fine region of the porous body so that at least a part of the film is covered.

  Examples of the oxide film include single-composition oxide films of titanium, gallium, iron, chromium, aluminum, magnesium, zirconium, indium, tin, vanadium, or silicon, or mixed crystal oxide films thereof.

  As the porous body, for example, a cylindrical film having at least one hollow space penetrating in the axial direction can be used. In this case, it is preferable that mist is introduced into the hollow space in the film forming step.

  In addition, as a configuration for guiding the mist into the hollow space in the film forming process, for example, a configuration in which the mist is discharged from a nozzle inserted in the hollow space is conceivable.

  In order to solve the above-described problem, a filtration apparatus according to the present invention includes any one of the above-described filtration filters and a light irradiation unit that irradiates light onto at least a surface of the filtration filter on which an oxide film is formed. It is characterized by having.

  According to the present invention, it is possible to reduce the diameter of fine pores of inorganic membranes and mesoporous substrates to such an extent that seawater can be desalinated, so various advantages that cannot be obtained with organic membranes. Can be enjoyed.

  That is, according to the present invention, it is possible to provide a filtration filter having high chemical resistance, salt resistance, and heat resistance. Moreover, since the filtration filter using an inorganic filter membrane and a mesoporous substrate has higher mechanical strength than that using an organic filter membrane, the film thickness can be reduced. Therefore, according to the present invention, the hydraulic pressure can be lowered as compared with the case where a filtration membrane made of an organic substance is used, so that a high-output pressure pump can be dispensed with and the running cost of the pressure pump can be reduced. Thus, the running cost of the filtration device can be reduced.

  In addition, according to the present invention, an oxide film having a uniform thickness can be formed along the surface shape of the fine region of the porous body that is the base, so by controlling the film thickness of the oxide film, The diameter of the fine hole can be controlled with high accuracy.

  Moreover, according to this invention, the manufacturing method which can manufacture the said filter with a comparatively simple apparatus and cheaply can be provided.

  Moreover, according to the present invention, it is possible to provide a filtration device that is less likely to be clogged and that can reduce maintenance costs and labor.

It is a perspective view of the porous body used by this invention, Comprising: (A) is a tube-type cylindrical filtration membrane, (B) is a monolith type columnar filtration membrane, (C) is a mesoporous substrate. In the manufacturing method which concerns on this invention, it is a schematic diagram of the film-forming apparatus used when forming an oxide film in a tube-shaped cylindrical filtration membrane. In the manufacturing method which concerns on this invention, it is a schematic diagram of the film-forming apparatus used when forming an oxide film in a monolith type cylindrical filtration membrane. In the manufacturing method which concerns on this invention, it is a schematic diagram of the film-forming apparatus used when forming an oxide film in a mesoporous substrate. It is a schematic diagram of a filtration device according to the present invention using a filtration filter comprising a tube-type columnar filtration membrane. It is a SEM image of a mesoporous substrate, (A) is an SEM image before forming an oxide film, (B) is an SEM image after forming an oxide film. It is a distribution diagram for demonstrating the change of the diameter of the micropore before and behind oxide film formation. It is the schematic diagram of the filtration apparatus using a cylindrical filtration membrane, (A) is a filtration apparatus using a tube-type cylindrical filtration membrane, (B) is a filtration apparatus using a monolithic cylindrical filtration membrane. is there.

  Hereinafter, preferred embodiments of a filtration filter and a method for manufacturing the same according to the present invention will be described with reference to the accompanying drawings. In addition, the component which attached | subjected the same code | symbol in each figure shall be the same. Moreover, although the seawater filtration filter for desalinating seawater is demonstrated below, this is only an example and this invention is applicable also to various filtration filters other than a seawater filtration filter.

[Configuration of porous body]
In FIG. 1, the porous body used when manufacturing the filtration filter which concerns on this invention is shown. As will be described in detail later, the filtration filter according to the present invention is manufactured by forming an oxide film on any one of the porous bodies shown in FIGS.

  FIG. 1A is a perspective view of a tube-type columnar filtration membrane 1A having one hollow space penetrating in the axial direction. The cylindrical filtration membrane 1A is mainly made of aluminum oxide, and a large number of micropores are present irregularly on the outer peripheral wall and the inner peripheral wall of the hollow space. The fine holes in the outer peripheral wall continue to the fine holes in the inner peripheral wall through complex internal passages stretched around like a mesh.

The cylindrical filtration membrane 1A has an outer diameter φ _1a of 10 mm, a hollow space diameter φ _2a of 7 mm, and a diameter of a fine hole (not shown) opened in the outer peripheral wall of 100 nm. Moreover, the diameter of the internal passage of the columnar filtration 1A tends to increase as the distance from the outer peripheral wall increases. Therefore, according to the cylindrical filtration membrane 1A before the oxide film is formed, only particles having an outer dimension of less than 100 nm can be transmitted and collected (see FIG. 8A).

  FIG. 1B is a perspective view of a monolithic cylindrical filtration membrane 1B having a plurality of hollow spaces penetrating in the axial direction. Similar to the columnar filtration membrane 1A, the columnar filtration membrane 1B is mainly made of aluminum oxide, and a large number of micropores are present irregularly on the outer peripheral wall and the inner peripheral wall of each hollow space. The fine holes in the inner peripheral wall continue to the fine holes in the outer peripheral wall through complicated internal passages stretched around like a mesh.

The columnar filtration membrane 1B has an outer diameter φ _1b of 30 mm, a diameter φ _2b of each hollow space of 3 mm, and a diameter of a fine hole (not shown) opened in the inner peripheral wall of 4 nm. Moreover, the diameter of the internal passage of the cylindrical filtration membrane 1B tends to increase as the distance from the inner peripheral wall of each hollow space increases. Therefore, according to the cylindrical filtration membrane 1B before the oxide film is formed, only particles having an outer dimension of less than 4 nm can be transmitted and collected (see FIG. 8B).

  FIG. 1C is a perspective view of a mesoporous substrate 1C in which a plurality of fine holes penetrating in the thickness direction are arranged in a plane. The mesoporous substrate 1C can be produced, for example, by anodizing an aluminum substrate that is scratched at a position where a fine hole is to be formed.

The mesoporous substrate 1C has a fine hole diameter φ _3c of 30 nm. Further, the fine holes of the mesoporous substrate 1C extend straight from one surface to the other surface while maintaining the diameter φ _3c . Therefore, according to the mesoporous substrate 1C before the oxide film is formed, only particles having an outer dimension of less than 30 nm can be transmitted and collected.

[Filtration filter manufacturing method, oxide film forming apparatus]
Subsequently, referring to FIG. 2, when the tube-shaped cylindrical filtration membrane 1A shown in FIG. 1 (A) is used as the porous body, the manufacturing method of the filtration filter and the oxide film according to the present invention are formed. A film forming apparatus 10A used for the above will be described.

  A film forming apparatus 10A shown in FIG. 2 is a mist CVD apparatus and has the following configuration. That is, the film forming apparatus 10A includes an air source 11, a flow rate adjusting valve 12 for adjusting the flow rate of air sent from the air source 11, a mist generating source 13 in which a solution 13a is placed, and water 14a. A container 14, an ultrasonic transducer 15 attached to the bottom surface of the container 14, a film forming chamber 16 made of a quartz tube, and a heater 17 made of a heating wire wound around the film forming chamber 16. Yes.

  In forming an oxide film using the film forming apparatus 10 </ b> A, first, the cylindrical filtration film 1 </ b> A is placed in the film forming chamber 16. In the present invention, the arrangement of the cylindrical filtration membrane 1A is not particularly limited, but the position or orientation of the cylindrical filtration membrane 1A can be changed during film formation from the viewpoint of forming an oxide film having a uniform thickness. Preferably there is. When the arrangement of the cylindrical filtration membrane 1A is completed, the film forming chamber 16 is heated to a predetermined temperature (for example, 300 to 500 ° C.) by the heater 17. In the mist CVD method, it is not necessary to depressurize the film forming chamber 16 or fill the film forming chamber 16 with an inert gas. Therefore, according to the mist CVD method, an oxide film can be formed with a relatively simple apparatus and at a low cost.

  When the temperature increase in the film forming chamber 16 is completed, the vibration of the ultrasonic vibrator 15 is started. When the ultrasonic vibrator 15 vibrates at a predetermined frequency (for example, 2.4 MHz), the vibration propagates to the solution 13a through the water 14a, and mist is generated from the solution 13a. The generated mist is pushed out into the air sent from the air source 11 and introduced into the film forming chamber 16 after the temperature rise.

The mist introduced into the film forming chamber 16 reaches the surface (surface of the outer peripheral wall) of the columnar filtration membrane 1A on which an oxide film is to be formed while being decomposed by high temperature. Then, a CVD reaction occurs on the surface of the outer peripheral wall of the cylindrical filtration membrane 1A, and an oxide film is formed along the surface shape of the fine region of the porous body. As a result, the surface on which the mist has reached and at least a part of the inner wall of the fine hole are covered with the oxide film. For example, when the solution 13a is composed of titanium acetylacetonate as a solute and methanol and ultrapure water as a solvent, a titanium oxide film is formed. In addition, in the film forming apparatus 10A, an oxide film shown in the table below or a silicon oxide film can be formed.

  The oxide film may be a single composition film or a mixed crystal film. In the case of a mixed crystal film, mist may be generated from the solution 13a in which two or more kinds of solutes are mixed, or two or more kinds of mist generated separately may be introduced into the film forming chamber 16 at the same time.

  The oxide film may have a multilayer structure in which a plurality of thin single composition films or mixed crystal films are stacked. With a multilayer structure, the adhesion of the oxide film to the porous body can be improved. Moreover, if it is set as a multilayer structure, the crystallinity and flatness of an outermost surface layer, and the affinity with water will improve, and the water permeation pressure of stock solution can also be reduced.

  When the formation of the oxide film is completed, the columnar filtration membrane 1A (filtration filter) with the oxide film is taken out from the film formation chamber 16. Thus, the production of the filtration filter according to the present invention is completed.

  As described above, the manufacturing method according to the present invention does not require a baking process at a high temperature for a long time. Therefore, according to the present invention, a filtration filter can be produced in a shorter time and at a lower cost than the method described in Patent Document 2.

Table 2 shows the relationship between the film formation time (film thickness) of the titanium oxide film and the hydraulic pressure.
As shown in the above table, the water permeation pressure before forming the titanium oxide film was 5 to 6 atmospheres, but the water permeation pressure after forming the titanium oxide film for 10 minutes was 6 to 7 atmospheres higher than that. The water permeation pressure after forming the titanium oxide film for 20 minutes was 11-12 atm. That is, the water permeation pressure increased as the deposition time of the titanium oxide film was increased. This is because the titanium oxide film having a thickness corresponding to the deposition time was formed, the diameter of the micropores was reduced, and the pressure loss when water molecules passed through the micropores and the internal passages increased. .

  Next, referring to FIG. 3 and FIG. 4, film forming apparatuses 10B and 10B ′ used for forming an oxide film on the monolithic cylindrical filtration membrane 1B shown in FIG. A film forming apparatus 10C used for forming an oxide film on the mesoporous substrate 1C shown in FIG.

  As shown in FIG. 3A, the film forming apparatus 10B includes a mist introducing mechanism 18 for introducing mist into each hollow space of the cylindrical filtration membrane 1B. The mist introduction mechanism 18 has a plurality of hollow rod-like protruding nozzles 18a provided with through holes for discharging mist to the surroundings, and each protruding nozzle 18a is inserted into the hollow space of the columnar filtration membrane 1B. . Thereby, mist is guide | induced into each hollow space of the cylindrical filtration membrane 1B, and an oxide film can be formed into the inner peripheral wall of each hollow space.

  In the film forming apparatus 10B, it is preferable that the mist introduction mechanism 18 can reciprocate along the protruding direction of the protruding nozzle 18a, or the cylindrical filtration membrane 1B can move back and forth along the axial direction. . Thus, film formation can be performed while changing the insertion depth of the protruding nozzle 18a, and an oxide film having a uniform thickness can be formed.

  As shown in FIG. 3B, the film forming apparatus 10B ′ includes an exhaust mechanism 19 provided so as to cover the far end portion (end portion far from the inlet of the quartz tube) of the cylindrical filtration membrane 1B. ing. In the film forming apparatus 10 </ b> B ′, the mist is guided into the hollow space on the air flow generated by operating the exhaust mechanism 19. Thereby, an oxide film can be formed on the inner peripheral wall of each hollow space.

  As shown in FIG. 4, the film forming apparatus 10C used when forming the oxide film on the mesoporous substrate 1C is not different from the film forming apparatus 10A shown in FIG. The mesoporous substrate 1C is disposed at a position where the mist efficiently reaches one surface.

  According to the film forming apparatuses 10B, 10B ', and 10C, various oxide films (including single composition films, mixed crystal films, and multilayer structures) can be formed as in the film forming apparatus 10A.

[Filtering equipment]
FIG. 5 shows a filtration device 4 using a filtration filter 3 formed by forming an oxide film on a tube-shaped cylindrical filtration membrane 1A. The filtration device 4 according to the present invention is different from the conventional filtration device 2A in that the light irradiation means 5 is provided (see FIG. 8A). The light irradiation means 5 consists of a light emitting diode which can irradiate light of an ultraviolet wavelength, for example. The light irradiation means 5 is directed toward the filter 3 and irradiates at least the surface on which the oxide film is formed with ultraviolet light.

  According to the filtration device 4 according to the present invention, the superhydrophilicity and photodegradation action of the oxide film having a photocatalytic effect can be expressed, so that clogging is unlikely to occur, and the labor and cost for maintenance can be reduced. it can. A typical example of an oxide film having a photocatalytic effect is a titanium oxide film.

[Experimental result]
FIG. 6 is an SEM image showing a result of forming a gallium oxide film on one surface of the mesoporous substrate 1C by the mist CVD method using the film forming apparatus 10C. As shown in FIG. 6A, the diameter of the micropores before forming the gallium oxide film was about 200 nm. However, after forming the gallium oxide film, as shown in FIG. In addition, the diameter of the fine holes was uniformly small. That is, by forming an oxide film using a film formation technique such as the mist CVD method, as shown in FIG. 7, the diameter is reduced while maintaining the opening shape and in-plane distribution of the fine holes before the film formation. It was confirmed that the size was reduced uniformly.

  In addition, the inventor of the present application has succeeded in reducing the diameter of the micropores to 1 nm or less by forming a titanium oxide film on the cylindrical filtration membranes 1A and 1B made of ceramic.

  As described above, since the filtration filter according to the present invention uses an inorganic porous material (filtration membrane or mesoporous substrate), it has chemical resistance and salt resistance compared to a filtration filter using an organic porous material. And heat resistance can be improved. Further, the filtration filter according to the present invention is used as a seawater filtration filter by controlling the film thickness of the oxide film so that the maximum diameter of the micropores is smaller than, for example, the diameter of sodium hydrate contained in seawater. can do. Note that the thickness of the oxide film can be arbitrarily controlled by changing the deposition time, the temperature of the deposition chamber, and the concentration of the metal contained in the solution.

  Moreover, since the manufacturing method of the filtration filter which concerns on this invention forms an oxide film in a porous body by mist CVD method, the process of decompressing a film-forming chamber or filling a film-forming chamber with an inert gas is carried out. Can be omitted. That is, according to the method for manufacturing a filter according to the present invention, it is possible to manufacture the filter with a relatively simple device and at a low cost.

  In addition, since the filtration device according to the present invention can express the superhydrophilicity and photodegradation action of an oxide film having a photocatalytic effect, clogging is unlikely to occur, and labor and cost for maintenance can be reduced. .

  In addition, this invention is not limited to the said embodiment, A various modified example can be considered. For example, in the present invention, in addition to a cylindrical filtration membrane and a mesoporous substrate, other porous bodies having high chemical resistance and heat resistance can also be used. However, it should be noted that if the diameter of the micropores is too large, the film formation time of the oxide film becomes long.

  In the above embodiment, an oxide film is formed on the outer peripheral wall of the tube-type cylindrical filtration membrane, the inner peripheral wall of the monolith-type cylindrical filtration membrane, and one surface of the mesoporous substrate. An oxide film may be formed on the inner peripheral wall of the cylindrical filtration membrane.

  In the above embodiment, the oxide film is formed by the mist CVD method, but may be formed by other methods. Other techniques that can form an oxide film include vacuum deposition, resistance heating deposition, electron beam heating deposition, molecular beam epitaxy, laser ablation, and sputtering deposition.

  In the present invention, the oxide film may be doped with a suitable element (for example, arsenic, molybdenum, nitrogen). Thereby, the photocatalytic effect can be enhanced, and the chemical resistance and salt resistance can be further improved.

  Furthermore, the method for producing a filtration filter according to the present invention can also be used when an oxide film is formed on a powder such as zeolite. A powder such as zeolite can capture a substance having a size suitable for the adsorption hole by the adsorption hole. However, according to the present invention, the size of the adsorption hole can be freely changed. Can be captured.

1A, 1B Cylindrical filtration membrane (porous body)
1C Mesoporous substrate (porous material)
2A, 2B Filtration device 3 Filtration filter 4 Filtration device 5 Light irradiation means 10A, 10B, 10C Film formation device 11 Air source 12 Flow rate control valve 13 Mist generation source 14 Container 15 Ultrasonic vibrator 16 Film formation chamber 17 Heater 18 Mist introduction Mechanism 19 Exhaust mechanism

Claims (11)

A porous body having a plurality of micropores;
An oxide film formed along the surface shape of the fine region of the porous body so as to cover the surface of the porous body where the micropores are open and at least a part of the inner wall of the micropore;
A filtration filter comprising:   The filtration filter according to claim 1, wherein the maximum diameter of the micropores after the oxide film is formed is smaller than the diameter of sodium hydrate contained in seawater.   2. The oxide film according to claim 1, wherein the oxide film is a single composition oxide film of titanium, gallium, iron, chromium, aluminum, magnesium, zirconium, indium, tin, vanadium, or silicon, or a mixed crystal oxide film thereof. 2. The filtration filter according to 2.   The filtration filter according to claim 1, wherein the oxide film is formed by a mist CVD method.   The porous body is a cylindrical filter having at least one hollow space penetrating in the axial direction, and the oxide film is formed on at least one of an outer peripheral wall and an inner peripheral wall of the cylindrical filter. The filtration filter according to any one of claims 1 to 4.   The porous body is a mesoporous substrate in which the micropores penetrating in the thickness direction are arranged in a plane, and the oxide film is formed on at least one surface of the mesoporous substrate. The filtration filter in any one of Claims 1-4. A temperature raising step for raising the temperature of a film forming chamber in which a porous body having a plurality of micropores is disposed;
A mist generating step of generating mist by vibrating the solution;
The mist is introduced into the film formation chamber after the temperature is raised, and a CVD reaction is caused on the surface of the porous body where the micropores are opened, so that at least a part of the surface and the inner walls of the micropores are covered. A film forming step of forming an oxide film along the fine region surface shape of the porous body,
The manufacturing method of the filtration filter characterized by including.   8. The oxide film according to claim 7, wherein the oxide film is a single composition oxide film of titanium, gallium, iron, chromium, aluminum, magnesium, zirconium, indium, tin, vanadium or silicon, or a mixed crystal oxide film thereof. The manufacturing method as described. The porous body is a cylindrical filter having at least one hollow space penetrating in the axial direction;
The manufacturing method according to claim 7 or 8, wherein, in the film forming step, the mist is guided into the hollow space.   The manufacturing method according to claim 9, wherein in the film forming step, the mist is discharged from a nozzle inserted into the hollow space. The filtration filter according to any one of claims 1 to 6,
A light irradiating means for irradiating at least a surface of the filtration filter on which the oxide film is formed;
A filtration apparatus comprising: