JPWO2007132832A1 - Method for treating substance to be treated in aqueous liquid, apparatus used for the method, and photocatalyst material - Google Patents

Abstract

A method of decomposing a substance to be treated dissolved or dispersed in an aqueous liquid, wherein a photocatalyst material is immersed in the aqueous liquid, and the aqueous liquid is irradiated with light and ultrasonic waves simultaneously, so that the photocatalyst material is subjected to light energy and Including a step of exposing to ultrasonic energy, and the photocatalyst material is composed of a titanium metal substrate and a titanium dioxide photocatalyst layer integrally formed on the surface thereof, and the thickness of the layer is greater than 1 μm. And a photocatalytic material suitable for carrying out the method.

Description

  The present invention relates to a method for treating a substance to be treated in an aqueous liquid using a titanium dioxide photocatalyst, an apparatus used for the method, and a photocatalyst material. More specifically, the present invention relates to a method for decomposing harmful substances in an aqueous liquid by simultaneously irradiating a titanium dioxide photocatalyst in an aqueous liquid with light and ultrasonic waves.

  It is widely known that photocatalysts have the ability to decompose harmful substances such as bacteria and nitrogen oxides, and application of photocatalysis is being studied in various fields.

  The photocatalyst is usually activated by irradiation with ultraviolet rays and exerts its action. Therefore, it is necessary to provide a light source so that the photocatalyst is exposed to light energy. However, when the substance to be treated in the aqueous solution is decomposed by the photocatalyst, it is difficult for light to reach the photocatalyst in water. There is a problem that a reaction space formed between the two is narrowed, and a processing amount is limited.

  On the other hand, Patent Document 1 discloses a method for producing a hydroxy radical, characterized in that titanium dioxide catalyst particles and water are brought into contact with each other in a fluid under irradiation of ultrasonic waves. According to this method, since the photocatalyst can be activated without irradiating light, the conventional problem that the amount of processing is small can be solved.

  Further, in Patent Document 2, in the method for treating an aqueous liquid containing a halogenated organic compound, (a) the aqueous liquid is contacted with a photocatalyst, (b) the aqueous liquid is irradiated with light, and ( c) A method of treating an aqueous liquid is disclosed, characterized in that the aqueous liquid is exposed to sonic energy at the same time. According to this method, the reaction rate and efficiency can be further improved by combining light irradiation and ultrasonic irradiation. In Patent Document 2, a small granular photocatalyst is considered preferable, and actually titanium oxide photocatalyst particles are used.

  Patent Documents 1 and 2 disclose the use of a granular titanium dioxide photocatalyst. However, the photocatalytic titanium oxide powder is usually a fine powder having a particle size of nanometer order. There is a problem that it is difficult to separate and recover the titanium oxide powder from the inside. In order to remedy this problem, it is conceivable to granulate the above powder into a powder having a particle size of the order of millimeters. However, since it is necessary to calcinate at a high temperature, anatase-type titanium dioxide tends to be mutated to a rutile type, and photocatalyst There is a problem that the action is reduced.

  On the other hand, photocatalytic titanium oxide powder can be kneaded with binders, dispersants, and stabilizers and coated on a suitable substrate. However, ultrasonic irradiation was performed using a coating photocatalyst. In this case, there is a problem that the coating film cannot withstand the load caused by the ultrasonic wave and peels off before the photocatalytic function is exerted and cannot be used. Further, since organic components such as a binder are mixed, not all coating surfaces have a photocatalytic function (only interspersed with photocatalytic reactants), and there is a problem that performance as a photocatalyst is lowered.

Furthermore, it is very difficult to develop a photocatalytic action in an aqueous liquid, and even when ultrasonic waves and light irradiation are used together, it is difficult to obtain a sufficient effect, and there is a photocatalyst suitable for use in an aqueous liquid. There was no problem.
JP 2003-26406 A Japanese National Patent Publication No. 5-503252

  Therefore, the present invention can exhibit a high photocatalytic action even in an aqueous liquid, has durability against ultrasonic waves, has enhanced photocatalytic activity by irradiating both light and ultrasonic waves, and is capable of separation and recovery. It is an object of the present invention to provide a method and an apparatus for efficiently decomposing a material to be treated in an aqueous liquid using a photocatalyst material that is easy to handle. Another object of the present invention is to provide a photocatalyst material suitable for use in an aqueous liquid.

  As a result of various studies to solve the above problems, the inventor of the present application uses a photocatalyst material in which a titanium dioxide photocatalyst layer is deposited on the surface of a base material by oxidizing the base material made of titanium metal. Attention has been paid to the fact that this photocatalyst material has durability against ultrasonic waves, and it has been found that photocatalytic activity is enhanced by simultaneous irradiation with light and ultrasonic waves. We have succeeded in developing a photocatalyst material that exhibits photocatalytic activity and solved the above problems.

  That is, the present invention is a method for decomposing a substance to be treated dissolved or dispersed in an aqueous liquid, wherein a photocatalyst material is immersed in the aqueous liquid, and the aqueous liquid is irradiated with light and ultrasonic waves at the same time. A step of exposing the material to light energy and ultrasonic energy, wherein the photocatalyst material comprises a titanium metal substrate and a titanium dioxide photocatalyst layer integrally formed on the surface thereof, and the thickness of the layer is greater than 1 μm. It is the processing method of the to-be-processed substance characterized by the above-mentioned.

  By using a photocatalyst material having a titanium dioxide photocatalyst layer integrally formed on the surface of a metal titanium substrate, the photocatalyst layer does not peel off even when irradiated with ultrasonic waves, and the photocatalytic function can be maintained. In addition, since the photocatalyst layer is deposited on the surface of the base material, it is easy to handle without the problem that separation and recovery are difficult as in the case where the photocatalyst powder itself having a particle size of nanometer is used. Further, by using light irradiation and ultrasonic waves in combination, the photocatalytic action is synergistically enhanced as compared with the case where each is applied alone. Furthermore, by making the thickness of the photocatalyst layer larger than 1 μm, a sufficient effect can be obtained even when used in water.

  The thickness of the photocatalyst layer is more preferably 1.5 μm or more, and particularly preferably 2.0 μm to 3.0 μm.

  Further, the present invention is an apparatus for performing the above-described treatment method, a water treatment tank that contains an aqueous liquid, a photocatalyst material that is disposed in the treatment tank and immersed in the aqueous liquid, and is disposed in the treatment tank. An ultrasonic device that irradiates the photocatalyst material with ultrasonic waves, and a light irradiation device that is disposed in the treatment tank and irradiates the photocatalyst material with light. The present invention relates to a processing apparatus comprising an integrally formed titanium dioxide photocatalyst layer, wherein the thickness of the layer is greater than 1 μm.

  Further, the present invention is an apparatus for performing the treatment method, wherein a water treatment tank containing an aqueous liquid, wherein at least a part of the wall surface is made of a light transmissive material, and disposed in the treatment tank to be converted into an aqueous liquid. The photocatalyst material to be immersed, the ultrasonic device that is arranged in the treatment tank and irradiates the photocatalyst material with ultrasonic waves, and is arranged outside the treatment tank so as to face the wall surface made of the light transmissive material, A photoirradiation device for irradiating light to the photocatalyst material, the photocatalyst material comprising a titanium metal substrate and a titanium dioxide photocatalyst layer integrally formed on the surface thereof, and the thickness of the layer is greater than 1 μm. The present invention relates to a processing apparatus.

As the photocatalyst material, if a photocatalyst plate having a photocatalyst layer formed on the entire surface of a plate-like metal titanium substrate having a large number of through holes penetrating the plate surface is used, both ultrasonic waves and light are applied to the photocatalyst. The photocatalyst can be activated efficiently. Further, since the aqueous liquid passes through the through holes, the surface area of the photocatalyst that comes into contact with the aqueous liquid is increased, and the processing efficiency can be increased. In particular, it is suitable for carrying out the treatment continuously while circulating an aqueous liquid. Moreover, since it is plate-shaped, replacement and recovery are easy.
If an ultrasonic irradiation device is disposed on one side of the photocatalyst plate and a light irradiation device is disposed on the other surface side, both the ultrasonic wave and light can be efficiently irradiated onto the photocatalyst of a large area, which is preferable.

  The water treatment tank is cylindrical or prismatic, and is provided with an aqueous liquid inlet at one end in the longitudinal direction and an aqueous liquid outlet at the other end. A light irradiation device is installed along the direction, an ultrasonic irradiation device is installed along the longitudinal direction on the opposite side surface, and a plurality of the photocatalyst plates are arranged in a row in the longitudinal direction between the two irradiation devices. By using a processing device that is arranged side by side and that is arranged so that the plate surface of each photocatalyst plate is inclined with respect to each irradiation device, both ultrasonic waves and light are efficiently irradiated to the photocatalyst of a large area. At the same time, since the aqueous liquid flowing from the inlet to the outlet flows through the through holes of the plurality of perforated plates, the aqueous liquid contacts the photocatalyst multiple times, and the aqueous liquid is processed very efficiently without generating a processing residue. can do.

  The present invention is also a photocatalyst material particularly suitable for use in a liquid, comprising a titanium metal substrate and a titanium dioxide photocatalyst layer integrally formed on the surface thereof, and the photocatalyst layer has a thickness of 2 μm or more. In addition, the present invention relates to a photocatalyst material characterized in that pores having a maximum diameter of 0.5 μm or more are scattered on the surface of the photocatalyst layer.

  According to the processing method, the processing apparatus, and the photocatalyst material according to the present invention, the photocatalyst layer is not peeled off and the photocatalytic function is not impaired even when irradiated with ultrasonic waves. Can be synergistically enhanced. Moreover, since a high photocatalytic action is exhibited even in an aqueous solution, the substance to be treated can be decomposed very efficiently. Furthermore, handling such as separation and recovery of the photocatalyst is easy.

FIG. 1 is an SEM photograph showing a cross section of the photocatalyst material according to the present invention. FIG. 2 is a perspective view of one embodiment of the apparatus according to the present invention. FIG. 3 is a longitudinal sectional view of another embodiment of the apparatus according to the present invention. FIG. 4 is a graph showing the results of a decomposition test of methylene blue colored water when the photocatalyst material according to the present invention is irradiated with ultraviolet rays and ultrasonic waves alone or in combination. FIG. 5 is a graph showing the relationship between the thickness of the photocatalyst layer and the ability to decompose methylene blue. FIG. 6 is an SEM photograph showing the surface state of the photocatalyst material B (layer thickness: 0.5 to 0.8 μm). FIG. 7 is an SEM photograph showing the surface state of the photocatalyst material D (layer thickness: 2 μm).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Water treatment tank 2 Photocatalyst material 3 Ultrasonic irradiation apparatus 4 Light irradiation apparatus 5 Inlet 6 Outlet 7 Fixing tool of photocatalyst plate

  In the present invention, the photocatalyst material comprises a metal titanium base material and a titanium dioxide photocatalyst layer integrally formed on the surface thereof. The titanium dioxide photocatalyst layer integrally formed on the surface of the metal titanium substrate refers to a titanium dioxide photocatalyst layer deposited by oxidizing the surface of the metal titanium substrate, and does not include a layer formed by coating. As the oxidation treatment, it is preferable to combine anodic oxidation and atmospheric oxidation, and more preferably, pretreatment of immersing the substrate in an aqueous solution containing a peroxide is performed before the anodic oxidation. Since the photocatalyst layer obtained by oxidizing the surface of the metal titanium base material is continuously formed on the metal titanium base material, there is no fear of peeling. Moreover, since a binder, a dispersing agent, etc. are not mixed, the photocatalytic function does not deteriorate.

  As the peroxide used in the pretreatment, hydrogen peroxide is preferable. A suitable pretreatment liquid is an aqueous solution containing 3 to 10% by weight of hydrogen peroxide. The immersion time of the substrate in the pretreatment liquid is preferably 5 to 48 hours.

In the anodic oxidation step, an electrolytic solution containing an organic acid or a salt thereof is used. Suitable organic acids and organic acid salts include sodium salts of tartaric acid, citric acid, malic acid, succinic acid, gluconic acid and fumaric acid. The concentration of the organic acid or organic acid salt in the electrolytic solution is preferably 0.5 to 5% by weight. Further, the electrolytic solution may further contain a pH adjusting agent for promoting ionic conduction during anodic oxidation in addition to the above organic acid and organic acid salt. Suitable pH adjusters include sulfuric acid, hydrochloric acid and sodium hydroxide. Such a pH adjuster is preferably contained in the electrolytic solution in an amount of 0.5 to 5% by weight. The electrolytic solution preferably contains 0.1 to 5% by weight of hydrogen peroxide.
An anode (substrate) and a cathode are placed in the above electrolytic solution, a voltage is applied between these electrodes, and the removal of this applied voltage is considered as one anodic oxidation step. The voltage profile in anodization is preferably increased stepwise or continuously at a rate of 0.1 to 0.3 V / second, and is maintained for 100 seconds or more at a peak voltage of 50 to 250 V. Thereafter, the applied voltage is removed instantaneously or gradiently. It is preferable that the anodized base material is sufficiently washed with water and then transferred to the next processing step.

  In the atmospheric oxidation step, the atmospheric oxidation temperature is preferably 500 to 600 ° C., and the atmospheric oxidation time is preferably 0.5 to 2 hours.

  By performing a combination of the anodizing step and the atmospheric oxidation step, it is possible to reliably form an anatase-type titanium oxide film having photocatalytic activity on the surface of the substrate. Note that either or both of the anodizing step and the atmospheric oxidizing step may be repeated twice or three times or more.

  In the present invention, the metal titanium substrate refers to a substrate made of pure titanium or a titanium alloy. Particularly preferred is a pure titanium substrate. Examples of the metal constituting the titanium alloy include platinum, gold, tin, palladium, ruthenium, nickel, cobalt, chromium, molybdenum, aluminum, vanadium, and zirconium. Suitable titanium alloys include titanium-aluminum-tin alloys (eg, Ti-5Al-2.5Sn), titanium-aluminum-vanadium alloys (eg, Ti-6Al-4V), and titanium-molybdenum-zirconium alloys (eg, Ti--). 15Mo-5Zr) and the like.

In the present invention, the light applied to the photocatalyst material is not particularly limited as long as it has a wavelength that can activate (excite) the photocatalyst to be used. In general, many photocatalysts are activated by ultraviolet light, and in this case, ultraviolet light having a wavelength of 400 nm or less, more preferably ultraviolet light having a wavelength region near 360 nm may be irradiated. In addition, when light having a wavelength region of 300 nm or less is irradiated, ozone is generated, so that a combination of photocatalysis and ozone can be expected. Therefore, you may irradiate the ultraviolet-ray with a wavelength of 180-260 nm, for example. When a visible light responsive photocatalyst is used, visible light may be irradiated. Examples of highly practical wavelengths include ultraviolet rays around 185 nm, 254 nm, and 360 nm. Particularly preferred is 254 nm ultraviolet light.
Moreover, it is preferable to perform light irradiation at 0.1-15 mW / cm < ² > with respect to the surface area of a photocatalyst. When the photocatalyst is used in a gas, a sufficient effect can be expected at 1 to 3 mW / cm ^2. However, in the present invention, the photocatalyst material is used in an aqueous liquid, and therefore, in order to obtain a sufficient effect, more intense light is irradiated. It is preferable to do. More preferably 3~12mW / cm ^2, particularly preferably 5~10mW / cm ^2.

  Moreover, it is preferable that more photocatalyst layers are exposed to light energy, for example, when using the metal titanium plate which has a photocatalyst layer on both surfaces, it is preferable to irradiate light from both sides of a plate. The light source may be provided in a container for containing an aqueous liquid, or may be provided outside the container, and the irradiated surface of the container may be made of a light transmissive material. Naturally, the light-transmitting material is a material that transmits light having a wavelength that can activate the photocatalyst to be used. For example, when using an ultraviolet-responsive photocatalyst, glass that can transmit ultraviolet light having a wavelength range of 400 nm or less. Alternatively, a transparent synthetic resin or the like can be used.

  The wavelength range of the ultrasonic wave irradiated to the photocatalyst is preferably 1 kHz to 1 MHz, more preferably 30 to 500 kHz, and particularly preferably 35 to 70 kHz. The output may be set within a preferable range depending on the size of the apparatus, but is generally preferably 200 W to 1500 W, more preferably 400 W to 1500 W, and particularly preferably 1000 W or more. As a preferred embodiment, an apparatus of 35 to 45 kHz: 1100 to 1300 W can be mentioned, but it may be about 400 W depending on the application. For example, if it is a small portable device, a 40 kHz: 400 W device may be used.

  Moreover, it is preferable that more photocatalyst layers are exposed to ultrasonic energy. For example, when using a metal titanium plate having photocatalyst layers on both sides, ultrasonic waves may be irradiated from both sides of the plate.

  In the present invention, the thickness of the photocatalyst layer can be confirmed by cross-sectional observation with a light scanning electron microscope (SEM). Since the photocatalyst layer of the present invention is formed continuously with the metal titanium substrate, unlike the coating film, there is no clear boundary between the photocatalyst layer and the substrate. However, by observing the cross section with an optical scanning electron microscope (SEM), it is possible to distinguish between titanium metal and titanium dioxide photocatalysts, so that the approximate layer thickness can be determined (see FIG. 1 sandwiched between the up and down arrows). The measured thickness is the layer thickness [2000 times one scale: 1.5 μm]). The thickness of the layer formed on the surface of the titanium base material is substantially constant, but the thickness varies slightly depending on the location. Therefore, the thickness of the photocatalyst layer in the present invention is the average value of the layer thickness at the location where the photocatalyst layer is formed. Point to.

  The shape of the photocatalyst material is not particularly limited, and may be any shape such as a plate shape, a rod shape, a net shape, a fiber shape, and a granular shape. In the present invention, since the photocatalyst material is preferably fixed, for example, when a granular photocatalyst material is used, it is used by filling a transparent resin column (transmitting light in a wavelength range that activates the photocatalyst). Is preferred. If a porous granular photocatalyst is used, the surface area is large and the efficiency is good. From the viewpoint of cost, a thin plate shape is preferable, and if a perforated plate shape having a large number of holes penetrating the plate surface (for example, a lath net-like or punching metal perforated plate) is used, light and ultrasonic waves can be transmitted from one side. Even when only irradiation is performed, the photocatalyst layer on the other surface can be activated, which is preferable. The plate having a large number of through holes is preferably a plate in which through holes are formed over almost the entire plate surface. Moreover, if it has a certain level of mechanical strength, fixation in an aqueous liquid is easy. For example, in the case of a thin plate shape made of pure titanium, it is preferable to have a thickness of about 0.5 mm.

  The photocatalyst layer is preferably formed on the entire surface of the metal titanium substrate or the entire surface of the metal titanium substrate that is immersed in the aqueous liquid, but when light and ultrasonic irradiation are performed only from one direction, The photocatalyst layer should just be formed in the surface of the part which receives at least irradiation.

The amount of the photocatalyst with respect to the aqueous liquid is preferably 0.5 m ² or more of the surface area of the photocatalyst with respect to 1 m ^{3 of} the aqueous liquid, although it depends on the type of the substance to be treated, the hardness of the water quality, and the irradiation conditions of light or ultrasonic waves. Moreover, when considering the upper limit of cost and processing efficiency, 10 m ² or less is preferable with respect to 1 m ^{3 of} the aqueous liquid. More preferably, it is 1.5 m ² or more, particularly preferably 2 m ² or more with respect to 1 m ³ of the aqueous liquid. The said surface area points out the total surface area of the photocatalyst of the part immersed in the aqueous liquid. The photocatalytic material need not be completely immersed in the aqueous liquid.
For example, as a photocatalyst material, when a lath net-like perforated plate having a photocatalyst layer deposited on the entire surface ("3-6 material" having rhombus-shaped inner diameters of 3 mm and 6 mm) is used by being completely immersed in an aqueous liquid, It is preferable to use 1 to 30 porous plates having a size of 500 mm × 500 mm × 1 mm per 1 m ³ , more preferably 3 to 20 plates, and particularly preferably 5 or more plates.

  The method and apparatus of the present invention can be used for purification of domestic wastewater and industrial wastewater, and can be applied to, for example, hot springs, public baths, pools, water tanks on the roof of apartments, factory wastewater, and the like. Therefore, examples of the substance to be treated according to the present invention include organic substances that can be contained in the aqueous liquid, pathogenic bacteria such as viruses and bacteria, and environmentally hazardous substances such as halogenated organic compounds.

FIG. 2 shows an embodiment of the processing apparatus of the present invention. 1 is a water treatment tank for storing an aqueous liquid, and 2 is a photocatalyst material. In the present example, 4 lath-like photocatalyst materials (0.5 m × 0.5 m × 1 mm thickness “3-6 material”) having a photocatalyst layer deposited on the entire surface in a water treatment tank capable of accommodating 1 m ³ of water. Is installed. 3 is an ultrasonic irradiation device, and 4 is an ultraviolet irradiation device. In this embodiment, the light irradiation device and the ultrasonic device are installed on the side walls inside the processing tank, and the photocatalyst material is fixed on the bottom surface. 5 is an inlet for the aqueous liquid, and 6 is an outlet.
In addition, the installation location in particular of an ultrasonic irradiation apparatus and a light irradiation apparatus is not restricted, You may install two or more. Further, the light irradiation device may be provided outside the processing tank, and the wall surface of the processing tank facing the light irradiation device may be made of a light transmissive material.

Further, as a preferred embodiment of the apparatus according to the present invention, an ultrasonic irradiation device and a light irradiation device are installed inside the water treatment tank, and the entire surface of the plate-shaped pure titanium base material having a large number of through holes on the plate surface A device in which a plurality of photocatalyst materials each having a photocatalyst layer formed thereon are installed so that the plate surfaces face an inclined surface with respect to both irradiation devices. For example, as shown in FIG. 3, it is a device having a cylindrical or prismatic water treatment tank, wherein an aqueous liquid inlet is provided on the side surface near one end in the longitudinal direction, and an outlet port is provided on the side surface near the other end. A light irradiation device is installed along the longitudinal direction on one side surface inside the device, and an ultrasonic irradiation device is installed along the longitudinal direction on the opposite surface, and there are a plurality of sheets between the two irradiation devices. A continuous water treatment device in which perforated plate-shaped photocatalyst materials are arranged side by side in the longitudinal direction and the plate surface of each photocatalyst material is inclined with respect to each irradiation device can be mentioned.
With such a configuration, both the ultrasonic wave and the light are efficiently irradiated to the photocatalyst having a large area, and the aqueous liquid flowing from the inlet to the outlet passes through the through holes of the plurality of perforated plates. Therefore, the aqueous liquid can be treated very efficiently without leaving any treatment residue. Since it is preferable that the charged aqueous liquid is discharged after reliably contacting the photocatalyst, the plate surface of the photocatalyst plate has a size and shape that substantially closes the cavity in the water treatment tank that becomes the flow path of the aqueous liquid. It is preferable to have. Specifically, it is preferable to use a photocatalyst plate having a shape and size that occupy 70% or more of the space area on the same plane as the plate surface of the photocatalyst plate in the water treatment tank. It is particularly preferable to use a photocatalyst plate that occupies 80% or more, more preferably 90% or more of the space area. With the above configuration, even a small apparatus can exhibit very high processing efficiency. For example, in a water treatment tank having a bottom area of 500 to 700 cm ² × height of about 50 to 80 cm, the photocatalyst layer is formed on the entire surface with a thickness and a size of 0.5 to 3 mm so as to substantially block the flow path of the aqueous liquid. If 10 to 20 lath net-like photocatalyst plates are formed, a water treatment apparatus having a very high treatment efficiency can be configured while being portable.

  From the viewpoint of efficiently performing the activity of the photocatalyst, the photocatalyst plate is preferably installed with an inclination so that an acute angle θ (see FIG. 3) formed by the irradiation device and the plate surface is 40 to 75 degrees, It is more preferable to install with an inclination of 45 to 70 degrees.

  The size and shape of the treatment tank of the present invention are not particularly limited, and can be appropriately changed according to the installation location, the amount of treated water, and the like.

The titanium dioxide photocatalyst layer of the present invention is preferably one having a layer thickness of 2 μm or more and dotted with holes having a maximum diameter of 0.5 μm or more on the surface. It is preferable that 10 or more holes having a maximum diameter of 0.5 μm or more are present per surface area of 1000 μm ^{2 of the} layer, more preferably 20 or more, still more preferably 50 or more, and particularly preferably 100 or more.

  Hereinafter, the present invention will be described more specifically with reference to examples.

[Manufacture of photocatalyst materials]
A plate-like substrate made of pure titanium having a thickness of 15 mm × 50 mm and a thickness of 1 mm was prepared. This substrate was previously pickled with 10 wt% hydrogen fluoride water and with 3 wt% hydrogen fluoride water and 10 wt% hydrogen peroxide. The substrate was pretreated by immersing it in a 5% by weight aqueous hydrogen peroxide solution at room temperature for 24 hours. Subsequent to the pretreatment, the substrate was anodized in an electrolyte solution consisting of 1 wt% sodium tartrate, 1 wt% sulfuric acid and 2 wt% hydrogen peroxide. As anodizing conditions, the voltage was increased stepwise by 0.24 V every 1.5 seconds, and when 120 V was reached, the voltage was maintained for 100 seconds, and anodizing consisting of a voltage program for turning off the switch was performed. Subsequently, the substrate was washed with water, dried, and then subjected to atmospheric oxidation at 500 ° C. for 60 minutes. The substrate was again anodized in an electrolyte solution consisting of 1 wt% sodium tartrate, 1 wt% sulfuric acid and 2 wt% hydrogen peroxide. As anodizing conditions, the voltage was increased stepwise by 0.24 V every 1.5 seconds, and when 120 V was reached, the voltage was maintained for 100 seconds, and anodizing consisting of a voltage program for turning off the switch was performed. The substrate was washed with water and dried, and then again subjected to atmospheric oxidation at 500 ° C. for 60 minutes to obtain a sample.
The photocatalyst material obtained by the above method had a titanium dioxide photocatalyst layer deposited on the entire surface of pure titanium serving as a base material.

  FIG. 1 shows a photograph of a cross-sectional view of the photocatalyst material. The photograph is from an optical scanning electron microscope (SEM). As shown in FIG. 1, when the cross section is observed with a light scanning electron microscope (SEM), the titanium dioxide photocatalyst layer is observed as a whitish layer, so that it is possible to distinguish between the titanium dioxide photocatalyst and pure titanium. As can be seen from FIG. 1, the photocatalyst layer of the photocatalyst material produced in Example 1 is formed integrally with the surface of the pure titanium base material, and has a configuration in which the titanium dioxide photocatalyst is continuous with the pure titanium.

[Comparative Example 1]
(Ultrasonic single irradiation)
Using the photocatalyst material produced in Example 1, a decomposition test of methylene blue colored water was performed by irradiating only ultrasonic waves.

Decomposition test of methylene blue colored water
Two sample cases were prepared in which 100 ml of an aqueous methylene blue solution adjusted to a concentration of 10 ppm was placed in a glass bottle with a cap. The photocatalyst material prepared above was pre-irradiated for 30 minutes in advance to clean the surface, and then put into a glass bottle, and nothing was put into the other glass bottle to make a blank. Next, prepare an ultrasonic cleaner (300mm x 240mm, depth 150mm), put 4L of tap water into this ultrasonic cleaner tank, and put it on the ultrasonic vibration plate at the center of the bottom of the cleaner tank that will be the ultrasonic transmission base. After fixing the glass bottle so that each glass bottle is located in the center, irradiate ultrasonic waves set so that the high frequency output is 39 kHz / 200 W, collect methylene blue aqueous solution at regular time intervals, and absorb the absorbance ratio with a spectrophotometer Was measured.

  The methylene blue concentration in the glass bottle containing the photocatalyst material is gradually decomposed thinly by irradiating with ultrasonic waves, but the blank concentration is hardly changed. Thus, it was found that the photocatalyst material can be decomposed without irradiating with ultraviolet rays by applying ultrasonic waves.

[Comparative Example 2]
(UV irradiation alone)
Using the photocatalyst material produced in Example 1, a decomposition test of methylene blue colored water was performed by irradiating only ultraviolet rays.

Decomposition test of methylene blue colored water
Two sample cases were prepared in which 100 ml of an aqueous methylene blue solution adjusted to a concentration of 10 ppm was placed in a glass bottle with a cap. The photocatalyst material prepared above was pre-irradiated for 30 minutes in advance to clean the surface, and then put into a glass bottle, and nothing was put into the other glass bottle to make a blank. Next, prepare an ultrasonic cleaner (300mm x 240mm, depth 150mm), put 4L of tap water into this ultrasonic cleaner tank, and put it on the ultrasonic vibration plate at the center of the bottom of the cleaner tank that will be the ultrasonic transmission base. After fixing the glass bottle so that each glass bottle is located in the center, without irradiating with ultrasonic waves, UV light of 1 mW / cm ² from above on the glass bottle fixed with 20 W × 2 black lights in the ultrasonic cleaner tank Ultraviolet rays were irradiated so as to obtain an intensity, and a methylene blue aqueous solution was collected at regular intervals, and the absorbance ratio was measured with a spectrophotometer.

  The methylene blue solution in the glass bottle containing the photocatalyst material is gradually decomposed thinly by irradiation with ultraviolet rays, but the concentration of the blank hardly changes. From this experiment, it was found that the photocatalytic oxidative decomposition reaction that appears only by the original ultraviolet irradiation was confirmed, and there was almost no difference between the ultraviolet irradiation alone and the ultrasonic irradiation alone, and the methylene blue concentration was reduced.

[Simultaneous irradiation of ultraviolet rays and ultrasonic waves]
Using the photocatalyst material produced in Example 1, a decomposition test of methylene blue colored water was performed by simultaneously irradiating ultraviolet rays and ultrasonic waves.

Decomposition test of methylene blue colored water
Two sample cases were prepared in which 100 ml of an aqueous methylene blue solution adjusted to a concentration of 10 ppm was placed in a glass bottle with a cap. The photocatalyst material prepared above was pre-irradiated for 30 minutes in advance to clean the surface, and then put into a glass bottle, and nothing was put into the other glass bottle to make a blank. Next, prepare an ultrasonic cleaner (300mm x 240mm, depth 150mm), put 4L of tap water into this ultrasonic cleaner tank, and put it on the ultrasonic vibration plate at the center of the bottom of the cleaner tank that will be the ultrasonic transmission base. The glass bottles were fixed so that each glass bottle was located in the center. Irradiate the ultrasonic wave set so that the high frequency output is 39kHz / 200W, and at the same time, from the top to the glass bottle with 20W × 2 black lights fixed in the ultrasonic cleaner tank, 1mW / cm ² Ultraviolet rays were irradiated so as to obtain an ultraviolet intensity, and a methylene blue aqueous solution was collected at regular intervals, and the absorbance ratio was measured with a spectrophotometer. In this example, the photocatalyst sample and the blank were irradiated with ultraviolet rays and ultrasonic waves simultaneously.

  The results of Comparative Examples 1 and 2 and Example 2 are shown in Table 1 and FIG. The numerical values in the table are absorbance ratios. As shown in Table 1 and FIG. 4, it is confirmed that the methylene blue concentration is greatly reduced when ultrasonic and ultraviolet rays are simultaneously irradiated as compared with single irradiation of ultrasonic and ultraviolet rays (Comparative Example 1 and Comparative Example 2). It was done. In addition, about the blank of Example 2, density reduction was hardly seen. As a result, it became clear that the ability to oxidatively decompose the substance to be treated was greatly improved by simultaneously irradiating the photocatalyst material with ultraviolet rays and ultrasonic waves.

[Performance comparison with and without photocatalyst layer]
A plate-like substrate made of pure titanium having a thickness of 15 mm × 50 mm and a thickness of 1 mm was prepared. This substrate was previously pickled with 10 wt% hydrogen fluoride water and with 3 wt% hydrogen fluoride water and 10 wt% hydrogen peroxide. The substrate was pretreated by immersing it in a 5% by weight aqueous hydrogen peroxide solution at room temperature for 24 hours. Subsequent to the pretreatment, the substrate was anodized in an electrolyte solution consisting of 1 wt% sodium tartrate, 1 wt% sulfuric acid and 2 wt% hydrogen peroxide. As anodizing conditions, the voltage was increased stepwise by 0.24 V every 1.5 seconds, and when 120 V was reached, the voltage was maintained for 100 seconds, and anodizing consisting of a voltage program for turning off the switch was performed. Subsequently, the substrate was washed with water, dried, and then subjected to atmospheric oxidation at 500 ° C. for 60 minutes.
The substrate was again anodized in an electrolyte consisting of 1 wt% sodium tartrate, 1 wt% sulfuric acid and 2 wt% hydrogen peroxide. As anodizing conditions, the voltage was increased stepwise by 0.24 V every 1.5 seconds, and when 120 V was reached, the voltage was maintained for 100 seconds, and anodizing consisting of a voltage program for turning off the switch was performed. The substrate was washed with water and dried, and then again subjected to atmospheric oxidation at 500 ° C. for 60 minutes to obtain a photocatalyst material sample. The thickness of the photocatalyst layer of the obtained photocatalyst material was about 0.8 to 1 μm.
On the other hand, an untreated pure titanium plate material in which pure titanium as a base material was only pickled and not subjected to photocatalytic treatment was used as an untreated sample.

Decomposition test of methylene blue colored water
Two sample cases were prepared in which 100 ml of an aqueous methylene blue solution adjusted to a concentration of 10 ppm was placed in a glass bottle with a cap. The prepared photocatalyst material was pre-irradiated for 30 minutes in advance to clean the surface, and then put into a glass bottle. An untreated pure titanium plate was placed in the other glass bottle to prepare an untreated sample. Next, prepare an ultrasonic cleaner (300mm x 240mm, depth 150mm), put 4L of tap water into this ultrasonic cleaner tank, and put it on the ultrasonic vibration plate at the center of the bottom of the cleaner tank that will be the ultrasonic transmission base. The glass bottles were fixed so that each glass bottle was located in the center. Irradiate the ultrasonic wave set so that the high frequency output is 39kHz / 200W, and at the same time, from the top to the glass bottle with 20W × 2 black lights fixed in the ultrasonic cleaner tank, 1mW / cm ² Ultraviolet rays were irradiated so as to obtain an ultraviolet intensity, and a methylene blue aqueous solution was collected at regular intervals, and the absorbance ratio was measured with a spectrophotometer.

The results are shown in Table 2. Similar to Example 2, with treatment (with photocatalyst layer), the concentration of methylene blue was significantly reduced by ultraviolet and ultrasonic irradiation, but without treatment (without photocatalyst layer), it was found that almost no decrease in concentration was observed. It was.
The cavitation energy generated by ultrasonic irradiation was thought to be an obstacle to the untreated pure titanium plate material, although it did not have a photocatalytic function. From this, it became clear that the substantial decomposition of methylene blue by ultraviolet and ultrasonic irradiation is almost entirely based on photocatalysis.

[Examination of photocatalyst layer thickness]
Manufacture of photocatalyst material Plate-like pure titanium of 15mm x 50mm x 1mm thickness was used as the titanium base, and the above base was pickled (etched [etched with 10wt% hydrogen fluoride water after primary etching, 3wt. Then, a photo-washing step of secondary etching with a mixed aqueous solution of% hydrogen fluoride and 10% by weight of hydrogen peroxide is performed]), and the following treatment is performed to obtain photocatalyst materials A to C having different photocatalyst layer thicknesses.
Photocatalyst material A (photocatalyst layer thickness: 0.3 to 0.5 μm)... Pretreatment for immersion in hydrogen peroxide solution (hereinafter, pretreatment), anodizing treatment (hereinafter, positive), atmospheric oxidation treatment (hereinafter, large).
Photocatalyst material B (photocatalyst layer thickness 0.5-0.8 μm): pretreatment, positive, positive, large.
Photocatalyst material C (photocatalyst layer thickness 0.8-1 μm): pretreatment, positive, large, positive, large.

Decomposition test of methylene blue colored water In the same manner as in Example 2, the performance of the photocatalyst materials A to C was compared under the condition of simultaneously irradiating the photocatalyst material with ultraviolet rays and ultrasonic waves. The results are shown in Table 3. As shown in Table 3, it was confirmed that the decomposition ability of methylene blue was improved as the thickness of the photocatalyst layer was increased.

[Production of photocatalyst material having a larger photocatalyst layer thickness]
In view of the results of Example 4, in order to confirm whether or not the decomposition speed of the substance to be treated in the aqueous liquid is further improved by making the photocatalyst layer thicker, production of a photocatalyst material having a photocatalyst layer thicker than 1 μm is performed. Tried. As a result of repeated improvements, a photocatalyst material having a photocatalyst layer thickness of 2 μm or more was successfully produced. Using the photocatalyst material D produced by the following treatment, a decomposition test of methylene blue colored water was performed in the same procedure as in Example 4.
Photocatalyst material D (photocatalyst layer thickness 2 μm): pretreatment, positive, positive, large, positive, positive, large.

  The results are shown in Table 4. Moreover, the graph which put together the result of Example 4 and Example 5 is shown in FIG. As shown in FIG. 5, it was found that the photocatalyst material D having a photocatalyst layer thickness of 2 μm has a very excellent decomposition speed.

[Observation of surface state of photocatalyst layer]
Even with a coating photocatalyst, it is possible to increase the thickness of the layer by repeating coating and drying, but even if the thickness is increased, the performance of the photocatalyst does not improve, or organic substances such as binders are used as impurity factors. Since it remains in the film, the performance is considered to deteriorate.
In the present invention, in order to investigate the cause of the improvement in the performance of the photocatalyst by increasing the thickness of the photocatalyst layer, the photocatalyst material B (photocatalyst layer thickness 0.5 to 0.8 μm) and photocatalyst material D (photocatalyst layer thickness 2 μm) The surface was observed with SEM. 6 and 7 show photographs of the photocatalyst layer surfaces of the photocatalyst materials B and D (6000 ×, 1 scale: 0.5 μm).

  As shown in the figure, there was a clear difference between the surfaces of the photocatalyst material B and the photocatalyst material D. The surface of the photocatalyst material B had innumerable small irregularities on the surface, and small pores having a diameter of about 0.1 μm existed, but the surface of the photocatalyst material D seemed to have multiple layers of porous layers. A large number of holes with a maximum diameter of 0.2 μm or more, many non-circular irregularly shaped holes with a maximum diameter of about 0.5 to 1.0 μm, and holes with a maximum diameter of 1.0 μm or more Was also observed.

  From this, it is considered that the relationship between the thickness of the photocatalyst layer and the photocatalytic performance in the present invention is caused by an increase in the surface area of the photocatalyst due to the surface state of the porous laminate. Such a surface shape is formed when the amorphous film is changed to crystalline titanium oxide by atmospheric oxidation treatment, and is loaded as much as possible by pretreatment hydrogen peroxide chemical treatment or anodization treatment. Since the film growth is forcibly performed, it is considered that the surface becomes rough and a porous state is formed.

[Antimicrobial effect against pathogenic bacteria]
Photocatalytic material D was immersed in an aqueous solution containing Legionella and an aqueous solution containing Escherichia coli, and the antibacterial effect was examined by simultaneously irradiating ultraviolet rays and ultrasonic waves. As a result, the photocatalyst material D significantly reduced Legionella and E. coli in a short time. This proves that the present invention is also effective against pathogenic bacteria.

[Device of the present invention]
A continuous water treatment apparatus according to the present invention was manufactured. FIG. 3 is a longitudinal sectional view of the schematic diagram. Specifically, a prismatic water treatment tank 1 having a size of 20 cm × 30 cm × height 60 cm is configured, an aqueous liquid inlet 5 is formed on the bottom side, and an aqueous liquid outlet 6 is formed on the top side. . Moreover, the light irradiation apparatus 4 long in the vertical direction was installed on one side surface in the treatment tank, and the ultrasonic irradiation apparatus 3 long in the vertical direction was installed on the opposite side surface. Then, between the two irradiation devices, each of the irradiation devices has 15 lath-like (3-6) photocatalyst plates 2 manufactured in the same manner as the photocatalyst material D, and an inclination angle θ of 70 degrees. And arranged in a row. The photocatalyst plate was fixed by a fixture 7 provided on one side of the water treatment tank. As the light irradiation device, a device that irradiates 254 nm ultraviolet light at 5 to 10 mW / cm ² was used, and as the ultrasonic irradiation device, a 38 kHz / 400 W device was used. The photocatalyst plate had a thickness of 1 mm, and a photocatalyst plate having a size and a shape that substantially closed the same inclined surface of the hollow portion in the treatment tank in an inclined state.

  A methylene blue aqueous solution prepared to a concentration of 10 ppm using the above apparatus was continuously flowed at a flow rate of 100 L / min, and was irradiated with ultrasonic waves and ultraviolet rays simultaneously. The absorbance of the methylene blue aqueous solution introduced and the methylene blue aqueous solution discharged from the outlet was measured with a spectrophotometer, and the decomposition rate of methylene blue was examined from the absorbance ratio. It has become clear that it has a high processing capacity.

From the results of Examples, it has been clarified that the photocatalytic activity is greatly improved by simultaneously irradiating the photocatalyst material of the present invention with ultraviolet rays and ultrasonic waves. In addition, a photocatalyst layer formed only by surface oxidation treatment using titanium metal as a base material can withstand a very heavy load environment such as ultrasonic irradiation, exhibits high photocatalytic activity, and the thickness of the photocatalyst layer is larger than 1 μm. Thus, it was found that the substance to be treated can be decomposed very efficiently even in a situation where it is difficult to exhibit the photocatalytic function in an aqueous liquid.
Therefore, in the past, photocatalysts were hardly effective in aqueous liquids due to conditions such as water flow, water quality, water pressure, material diffusion rate, etc. and coating photocatalyst peeling, and it was difficult to develop water purification. However, it has been clarified that the present invention can be sufficiently effective in water purification applications.

Claims (9)

A method for decomposing a substance to be treated dissolved or dispersed in an aqueous liquid,
Immerse the photocatalyst material in the aqueous liquid,
Irradiating the aqueous liquid with light and ultrasonic waves simultaneously to expose the photocatalytic material to light energy and ultrasonic energy,
The said photocatalyst material consists of a metal titanium base material and the titanium dioxide photocatalyst layer integrally formed in the surface, The thickness of the said layer is larger than 1 micrometer, The processing method of the to-be-processed substance characterized by the above-mentioned. The method according to claim 1, wherein the thickness of the layer is 1.5 μm or more. The method according to claim 1, wherein the thickness of the layer is 2 μm to 3 μm. An apparatus for treating an aqueous liquid containing a substance to be treated in a dissolved or dispersed state,
A water treatment tank containing the aqueous liquid;
A photocatalytic material disposed in the treatment tank and immersed in the aqueous liquid;
An ultrasonic irradiation device that is disposed in the treatment tank and irradiates the photocatalyst material with ultrasonic waves;
A light irradiation device disposed in the treatment tank and irradiating light to the photocatalyst material;
The said photocatalyst material consists of a titanium metal base material and the titanium dioxide photocatalyst layer integrally formed in the surface, The thickness of the said layer is larger than 1 micrometer, The processing apparatus characterized by the above-mentioned. An apparatus for treating an aqueous liquid containing a substance to be treated in a dissolved or dispersed state,
A water treatment tank containing the aqueous liquid, wherein at least a part of the wall surface is made of a light-transmitting material;
A photocatalytic material disposed in the treatment tank and immersed in the aqueous liquid;
An ultrasonic irradiation device that is disposed in the treatment tank and irradiates the photocatalyst material with ultrasonic waves;
A light irradiation device that is disposed outside the treatment tank so as to face the wall surface made of the light transmissive material, and irradiates light to the photocatalyst material;
The said photocatalyst material consists of a titanium metal base material and the titanium dioxide photocatalyst layer integrally formed in the surface, The thickness of the said layer is larger than 1 micrometer, The processing apparatus characterized by the above-mentioned. 6. The processing apparatus according to claim 4, wherein the photocatalyst material is a photocatalyst plate in which a photocatalyst layer is formed on the entire surface of a plate-like metal titanium base material having a large number of through holes. The processing apparatus according to claim 6, wherein the ultrasonic irradiation device is disposed on one surface side of the photocatalyst plate, and the light irradiation device is disposed on the other surface side. The water treatment tank is cylindrical or prismatic, and is provided with an inlet for an aqueous liquid at one end in the longitudinal direction and an outlet for an aqueous liquid at the other end. The ultrasonic irradiation device is installed along the longitudinal direction on the opposite side surface, and a plurality of the photocatalyst plates are arranged in a row in the longitudinal direction between the two irradiation devices. The processing apparatus according to claim 7, wherein the processing apparatus is arranged so that a plate surface of each photocatalyst plate is inclined with respect to each irradiation apparatus. It consists of a titanium metal substrate and a titanium dioxide photocatalyst layer integrally formed on the surface thereof. The photocatalyst layer has a thickness of 2 μm or more, and the surface of the photocatalyst layer is dotted with holes having a maximum diameter of 0.5 μm or more. A photocatalytic material characterized by