JP2008142660A - Photocatalyst unit and its use - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photocatalyst unit for use in absorption-type polluted water purification, which uses a flat plate-shaped photocatalyst supported porous body, can effectively purify various types of polluted water and efficiently utilize sunlight to recover purification performance and thus to allow the photocatalyst unit to be usable repeatedly. <P>SOLUTION: In this photocatalyst unit, the angle of the flat plate-shaped photocatalyst supported porous body to the ground surface can be freely varied at least in an angle range of 40 to 90 degrees. A liquid to be purified is supplied to the upper end in the flat plate-shaped photocatalyst supported porous body which stands at an angle in the above-defined angle range to allow the liquid to be purified to flow into the flat plate-shaped photocatalyst supported porous body to adsorb the contaminants. Sunlight is then applied to the coating film to decompose the adsorbed contaminants. The above procedure is then repeated. In order to determine the time of switching from the decomposition treatment to the adsorption treatment, an indicator using a coloring matter, which causes color fading upon exposure to ultraviolet light, is mounted on a support of the flat plate-shaped photocatalyst supported porous body. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a photocatalytic unit and a method for using the same. More specifically, the present invention is a photocatalyst unit used for purification of adsorption-type sewage, and uses a plate-like photocatalyst-supporting porous body to effectively purify various sewage, for example, pesticide waste liquid and waste liquid in hydroponic cultivation. The present invention relates to a photocatalyst unit that can be used repeatedly by efficiently using sunlight and recovering its purification performance, and a method of using the same.

When a photocatalytic material (hereinafter sometimes simply referred to as a photocatalyst) is irradiated with light having energy higher than its band gap, it is excited to generate electrons in the conduction band and holes in the valence band. The generated electrons reduce surface oxygen to generate superoxide anions (• O ²⁻ ), and holes oxidize surface hydroxyl groups to generate hydroxyl radicals (• OH). It is known that active oxygen species exert a strong oxidative decomposition function and decompose organic substances adhering to the surface of the photocatalyst with high efficiency.

  By applying such photocatalytic functions, for example, deodorization, antifouling, antibacterial, sterilization, and decomposition / removal of various substances that cause environmental pollution in wastewater and waste gas are being studied. Yes.

  As one of the uses of the photocatalyst, as described above, it has been attempted to decompose and remove various substances that are a problem of environmental pollution in wastewater, and is made of, for example, a heat-resistant fiber having light permeability. There has been proposed a technique for treating harmful substances in a liquid using a photocatalyst formed by forming a titanium oxide film on a heat-resistant fiber itself of a woven fabric (see, for example, Patent Document 1). Moreover, using a titanium oxide photocatalyst and utilizing sunlight, a technique for treating the waste liquid after paddy rice seed disinfection (see, for example, Patent Document 2), and a waste liquid in culture medium circulation type hydroponic cultivation using an organic medium Processing techniques (see, for example, Patent Documents 2 and 3) have been proposed.

  However, it is generally difficult to efficiently decompose organic substances remaining in an aqueous solution using such a photocatalytic reaction. The decomposition reaction occurs when the wastewater to be treated is brought into contact with the photocatalyst and irradiated with ultraviolet light. In this case, the factor that determines the decomposition reaction is not the photocatalytic reaction, but the transport of the substance to be decomposed to the photocatalyst. Often in the process and adsorption process.

  Therefore, various attempts have been made to utilize the adsorption phenomenon as a method for purifying sewage that can be quickly purified, and there are technologies that have achieved an effect that can sufficiently satisfy the purification rate, but in this technology, In principle, the purification unit is disposable, and there are problems in terms of economy and disposal.

  In order to solve such a problem, the present inventors have developed a purification unit having a planar photocatalyst-supporting porous body containing an adsorbent so that sunlight is inclined at an angle of 10 ° or more with respect to the ground. An adsorption type sewage purification method was proposed in which the wastewater to be treated is supplied to the upper end portion, passed through the photocatalyst-supporting porous body at a specific flow rate, and then recovered from the lower end face (for example, patents) Reference 4).

The purification unit can be repeatedly used by such a photocatalytic reaction using sunlight. In order to repeatedly use this purification unit, it has been found that it is necessary to irradiate with an integrated light quantity of 70 mW / cm ² or more according to the study by the present inventors.

However, when trying to obtain an integrated light quantity of 70 mW / cm ² using sunlight, two problems are raised. One is low energy density in sunlight, and the other is instability of solar energy. The angle at which the amount of light is most easily obtained is generally 45 ° to 60 ° with respect to the ground, whereas the relationship between the angle θ of the unit with the ground and the purification rate is expressed by the following equation 1, and the angle θ is 90 °. In this case, the fastest processing speed can be achieved. In the conventional apparatus, the inclination of the unit is set at about 80 °, which is the middle of the unit, and both the ultraviolet light quantity and the reproduction speed are achieved. As a result, the energy in sunlight could not be used efficiently.

Maximum processing speed V = V ₉₀ (1-cos θ) (1)
(V ₉₀ : Maximum processing speed when the unit is set at 90 °)

In addition, the amount of ultraviolet light in sunlight fluctuates due to the influence of the area, weather, and location conditions. For example, in the western part of Kanagawa Prefecture, the average of the cumulative ultraviolet light intensity obtained in any five days from April 20, 2005 to May 23, 2005 was 102 mW / cm ² · hr. The average time was 44 mW / cm ² . In such a case, it is difficult to know whether the unit is able to obtain sufficient amount of ultraviolet light necessary for regeneration. It may cause discharge into the environment.

  On the other hand, a method for using a photocatalyst carrier comprising: an adsorption step for adsorbing a substance to be decomposed on a photocatalyst carrier carrying a photocatalyst; and a decomposition step for decomposing the adsorbed substance to be decomposed by light irradiation, A method of using a photocatalyst carrier that performs switching or balance adjustment between the adsorption step and the decomposition step according to the coloration is disclosed (for example, see Patent Document 5).

  However, in this technique, a change in the color tone of the photocatalyst carrier itself is detected. Since the change in the color tone is not clear, an optical sensor must be used and a change in the color tone is caused. It is necessary to select a transparent or white resin or ceramic as the material of the support base material so that many particles are exposed on the surface of the sheet, and there is a disadvantage that the material of the support base material is unavoidable. .

JP-A-7-96202 JP 2004-82095 A Japanese Patent Laid-Open No. 9-327246 JP 2006-136875 A JP 2002-282653 A

  Under such circumstances, the present invention is a photocatalyst unit used for adsorption-type sewage purification, using a plate-like photocatalyst-supported porous body having a coating film containing a photocatalyst material and an adsorbent, and various sewage effects. It is an object of the present invention to provide a photocatalyst unit that can be used repeatedly and recover its purification performance by efficiently using sunlight and a method of using the same.

  As a result of intensive studies to achieve the above object, the present inventors have freely adjusted the flat photocatalyst-supporting porous body constituting the photocatalyst unit so as to have an angle within a specific range with respect to the ground. In order to determine when to switch from the decomposition treatment of the photocatalyst material in the plate-like photocatalyst-supporting porous material and the adsorbed filth with sunlight to the adsorption treatment, a photocatalyst unit equipped with a specific indicator is used. Further, the present inventors have found that the purpose can be achieved by switching from the decomposition process to the adsorption process when the indicator fades to a predetermined color tone. The present invention has been completed based on such findings.

That is, the present invention
(1) A flat photocatalyst-supporting porous body having a coating film containing a photocatalyst material and an adsorbent is provided on the surface that is exposed to sunlight, and the flat photocatalyst-supporting porous body is at least 40 to the ground. The degree of inclination can be adjusted freely so that the angle is in the range of 90 degrees, and the liquid to be purified is provided in the width direction at the upper end of the flat plate-like photocatalyst-supporting porous body standing at an angle within the range. Supplied from the plurality of dripping ports and flowed into the plate-like photocatalyst-supported porous body to adsorb the filth, and then irradiate the coating with sunlight to decompose the adsorbed filth with the photocatalyst material. In order to determine the switching time from the decomposition treatment to the adsorption treatment, an indicator that uses a dye that fades due to ultraviolet rays in sunlight is used for the repetitive photocatalytic unit, and the flat plate-like shape is formed at the start of the decomposition treatment. Catalyst-carrying porous body or a photocatalyst unit, characterized in that attached to the support cradle,
(2) The photocatalytic unit according to (1) above, wherein the indicator is a water-resistant paper carrying a dye that fades with ultraviolet light, and is sandwiched between weather-resistant substrates.
(3) The photocatalytic unit according to (1) or (2) above, wherein the dye that fades with ultraviolet light is 1- (2-pyridylazo) -2-naphthol and / or 1- (phenylazo) -2-naphthol.
(4) The photocatalyst unit according to any one of (1) to (3), wherein a color sample is attached together with the indicator.
(5) At the upper end of the flat photocatalyst-carrying porous body, the liquid to be purified is supplied from a plurality of dripping ports and flows into the flat photocatalyst-carrying porous body to adsorb the filth, and at least 80 degrees with respect to the ground The photocatalyst unit according to any one of (1) to (4), which is adjusted to have an angle of
(6) When the coating film is irradiated with sunlight and the adsorbed filth is decomposed with the photocatalytic material, the coating is directed toward the south and adjusted to have an angle of 45 to 60 degrees with respect to the ground. ) To (5), the photocatalyst unit according to any one of items
(7) The photocatalyst unit according to any one of (1) to (6) above, wherein a plurality of dripping ports for supplying the liquid to be purified are provided at intervals of 2 to 10 cm.
(8) The photocatalyst unit according to any one of (1) to (7) above, wherein the support in the flat photocatalyst-supported porous body is made of an inorganic porous body.
(9) The photocatalytic unit according to the above (8), wherein the inorganic porous material is a nonwoven fabric made of glass fiber,
(10) The photocatalytic unit according to any one of (1) to (9) above, wherein the coating film contains an inorganic adhesive component,
(11) The photocatalyst unit according to any one of (1) to (10) above, wherein the adsorbent is activated carbon, and (12) any one of (1) to (11) above. A method of using the photocatalyst unit, wherein when the indicator fades to a predetermined color tone, the photocatalyst unit is switched from the decomposition process to the adsorption process.
Is to provide.

  According to the present invention, it is a photocatalyst unit used for purification of adsorption-type sewage, and using a plate-like photocatalyst-supporting porous body having a coating film containing a photocatalyst material and an adsorbent, various sewage can be effectively purified. The photocatalytic unit that can be used repeatedly and a method for using the same can be provided by efficiently recovering the purification performance of sunlight.

  In the photocatalyst unit of the present invention, a flat photocatalyst-supporting porous body having a coating film containing a photocatalyst material and an adsorbent is provided on the surface that is exposed to sunlight, and the flat photocatalyst-supporting porous body is in contact with the ground. The inclination can be freely adjusted so that the angle is in the range of at least 40 to 90 degrees, and the liquid to be purified is placed on the upper end of the flat photocatalyst-supporting porous body set up at an angle within the range. Is supplied from a plurality of dripping ports provided in the width direction to flow into the flat plate-like photocatalyst-supporting porous body to adsorb the filth, and then the coating film is irradiated with sunlight to adsorb the adsorbed filth with the photocatalyst material. The operation of disassembling is repeated.

  First, a plate-like photocatalyst-supporting porous body (hereinafter sometimes simply referred to as a plate-like photocatalyst) that constitutes the photocatalyst unit of the present invention will be described.

[Plate-shaped photocatalyst-supported porous body]
In the flat photocatalyst-supporting porous body, an inorganic porous body is preferably used as the support. The inorganic porous material preferably has voids such that the water retention rate of distilled water is 500 to 3000% by mass. If this water retention rate is in the above range, the surface area in contact with the sewage is sufficiently large, the liquid to be purified tends to pass through the inside of the inorganic porous body, and the ultraviolet light reaches the inside of the inorganic porous body sufficiently. A more preferable water retention rate is 500-1500 mass%.

  Moreover, it is preferable that the suction height (capillary force) of distilled water is 12 mm or more. If the suction height is 12 mm or more, the liquid to be purified penetrates easily into the photocatalyst body. The suction height is more preferably 50 mm or more. Although there is no restriction | limiting in particular in the upper limit of this wicking height, Usually, it is about 200 mm.

  As a material constituting such an inorganic porous body, it can be appropriately selected from porous ceramics having a three-dimensional network structure, woven fabrics and nonwoven fabrics made of inorganic fibers, from an economic viewpoint, A woven fabric or a nonwoven fabric made of glass fiber is suitable. Examples of the woven fabric and nonwoven fabric made of glass fiber include silica glass long fiber woven fabric woven by a general method, silica glass short fiber entangled nonwoven fabric produced by a needle punch method, and the like.

  In addition, the water retention of the silica glass nonwoven fabric is the amount of increase in mass relative to the original mass of the silica glass nonwoven fabric when the silica glass nonwoven fabric is immersed in distilled water for 10 minutes and then gently lifted and left standing for 10 minutes. It is calculated | required by calculating the ratio. The suction height is the height of the water surface sucked up by the silica glass nonwoven fabric when 2 cm below the silica glass nonwoven fabric cut into a strip of 3 cm width is immersed in distilled water and held for 10 minutes. Say it.

  In the said flat photocatalyst body, the coating film (photocatalyst layer) containing a photocatalyst material, an adsorbent, and the inorganic adhesive component depending on the case is provided in the surface of the said inorganic porous body. The volume fraction of the photocatalytic material in the coating film varies depending on the adsorption characteristics of the adsorbent, but is generally preferably in the range of 10 to 50%. If this volume fraction is in the above range, it has good photocatalytic activity, and the substance to be treated in the liquid to be purified is easily trapped by the adsorbent present in the vicinity of the photocatalytic material. The volume fraction is more preferably in the range of 10 to 30%.

In addition, the amount of the photocatalytic material supported is preferably in the range of 8 to ²⁰ g / m ² , and more preferably in the range of 10 to 15 g / m ² , regardless of the amount of adsorbent, from the viewpoint of the balance of photocatalytic activity and economy. preferable.

In addition, the adsorbent loading is preferably 50 to 90% in terms of volume fraction in the coating film from the viewpoint of the balance between sewage component capture performance and economic efficiency, but 10 g × specific gravity of the adsorbent. /4.0 to 135 g × specific gravity of the adsorbent / 4.0. For example, in the case of a silica adsorbent with a specific gravity of 1.8, it may be in the range of 4.5 to 61 g / m ² , and in the case of an alumina adsorbent with a specific gravity of 3.7, 9.2 to 125 g / m. if the ^second range well can be estimated to be sufficient if the range of 2.0~27.0g / ^{m 2} if the activated carbon adsorbent having a specific gravity of 0.8.

  Furthermore, the surface wettability of the flat photocatalyst is preferably 60 ° or less in terms of the water contact angle of the coating film provided on a smooth surface such as a slide glass. If the water contact angle is 60 ° or less, the sewage easily penetrates into the flat photocatalyst.

  The thickness of the flat photocatalyst is preferably less than 12 mm. If this thickness is less than 12 mm, the ultraviolet light easily reaches the deep part of the photocatalyst. The minimum thickness may be a thickness with which the transmittance of light at 365 nm is 20% or less, although it depends on the structure of the inorganic porous material.

  As a photocatalyst material constituting the coating film (photocatalyst layer) in the photocatalyst body, for example, anatase type titanium oxide and / or brookite type titanium oxide can be used, and an anatase type having an average particle size of 1.0 to 100 nm. Titanium oxide fine particles are preferable, and those having an average particle diameter of 1.0 to 50 nm are particularly preferable. The average particle diameter can be measured by a scattering method using laser light.

  Further, at least one selected from the group consisting of V, Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Pt and Au as a second component inside and / or on the surface of the titanium oxide particles. It is preferable to include a seed metal and / or metal compound because it has a higher photocatalytic function. Examples of the metal compound include metal oxides, hydroxides, oxyhydroxides, sulfates, halides, nitrates, and metal ions. The content of the second component is appropriately selected according to the type of the substance.

  The anatase-type titanium oxide particles can be produced by a conventionally known method, but it is advantageous to use the titanium oxide sol in the form of a titanium oxide sol in order to uniformly disperse it in the coating liquid. In order to produce the titanium oxide sol, for example, powdered anatase-type titanium oxide may be dissolved in the presence of acid or alkali, or the particle diameter may be controlled by pulverization. In addition, the hydrous or neutralized decomposition of titanium sulfate or titanium chloride may be used to control the crystallite size and particle size by physical and chemical methods. Furthermore, a dispersion stabilizer can be used to impart dispersion stability in the sol solution.

  Moreover, as an adsorbent which comprises the coating film (photocatalyst layer) in the said photocatalyst body, colloidal silica, an alumina, a zirconia, an amorphous titania, magnesium hydroxide, activated carbon etc. can be used, for example. These may be used individually by 1 type and may be used in combination of 2 or more type.

Furthermore, as a desired inorganic adhesive component constituting the coating film (photocatalyst layer) in the photocatalyst, for example, a silica binder, an alumina binder, an amorphous titania binder, or the like can be used. These may be used alone or in combination of two or more. Among them, an amorphous titania binder is preferable because of its excellent water resistance.
This amorphous titania binder can be produced by hydrolysis and condensation of titanium alkoxide.

  As the titanium alkoxide, titanium tetraalkoxide having 1 to 4 carbon atoms in the alkoxyl group is preferably used. In this titanium tetraalkoxide, the four alkoxyl groups may be the same or different, but the same one is preferably used from the viewpoint of availability. Examples of the titanium tetraalkoxide include titanium tetramethoxide, titanium tetraethoxide, titanium tetra-n-propoxide, titanium tetraisopropoxide, titanium tetra-n-butoxide, titanium tetraisobutoxide, titanium tetra-sec- Examples include butoxide and titanium tetra-tert-butoxide. These may be used individually by 1 type and may be used in combination of 2 or more type.

The titanium alkoxide is hydrolyzed / condensed to form an amorphous type titania binder. This hydrolysis / condensation reaction is preferably 0.5 to 4 times that of titanium tetraalkoxide in an appropriate organic solvent. The reaction can be carried out at a temperature of usually 0 to 70 ° C., preferably 20 to 50 ° C. in the presence of an inorganic acid such as hydrochloric acid, sulfuric acid, nitric acid, etc.
In this way, an amorphous titania binder having excellent water resistance is obtained.

  In the present invention, in order to produce a flat photocatalyst-supporting porous body, first, a photocatalyst coating solution is prepared. The photocatalyst coating solution can be prepared by dispersing the photocatalyst material, an adsorbent, and optionally an inorganic adhesive component in an appropriate solvent.

The photocatalyst coating liquid thus obtained is applied to at least the surface of the inorganic porous body that is exposed to sunlight, and a coating film (photocatalyst layer) is provided, whereby a flat photocatalyst having a thickness of less than 12 mm is provided. A supported porous body (photocatalyst body) can be produced.
Although there is no restriction | limiting in particular about the coating method of a photocatalyst coating liquid, For example, the immersion method etc. can be used.

In the present invention, the flat photocatalyst-supported porous body having a thickness of less than 12 mm is a woven fabric having a strength of 98 N / cm or more made of inorganic fibers or organic fibers on the opposite side of the photocatalyst-supported porous body from the side on which sunlight strikes. Can be used as a two-layer structure. By adopting the two-layer structure in this way, the strength of the photocatalyst-supporting porous body can be dramatically improved while maintaining the purification efficiency of sewage.
In the present invention, a plurality of droplets to be purified are provided in the width direction at the upper end of the plate-like photocatalyst-supporting porous body obtained in this way.

  About the size of the plate-like photocatalyst-supported porous body obtained in this way, although it depends on the amount of the liquid to be purified, it is usually about 30 to 200 cm in length and about 5 to 120 cm in width, preferably 30 to 120 cm in length, The width is 20 to 90 cm. When a larger size is required, a plurality of plate-like photocatalyst-supporting porous bodies having a size that can be accommodated within the above-described size may be used.

[Adsorption treatment of filth in the liquid to be purified]
In the present invention, it is preferable to adjust the flat photocatalyst-supported porous body so as to have an angle of 80 degrees or more with respect to the ground. If the angle of the flat photocatalyst body with respect to the ground is 80 degrees or more, a sufficient purification rate can be ensured. Then, a predetermined amount of the liquid to be purified is dropped at a predetermined flow rate from a plurality of dropping ports provided at the upper end of the photocatalyst body, and the photocatalyst body is soaked. The soaked sewage passes through the inside of the photocatalyst by its own weight, and the purified sewage is drained from the lower end face of the photocatalyst.

  In the present invention, by providing a plurality of droplets to be purified in the width direction at the upper end of the flat photocatalyst body, the liquid to be purified can be uniformly infiltrated into the flat photocatalyst body.

  The dropping speed of the liquid to be purified is controlled by, for example, a method of adjusting the flow rate with a valve provided upstream of the dropping port, a method of controlling the flow rate from the water supply source to the perforated water pipe, and controlling the pressure and flow rate. Thus, it is possible to control the liquid to be purified from a porous tube having countless micropores, and the liquid to be purified can be controlled in the width direction of the upper end of the photocatalyst-supporting porous body by such a method. It becomes possible to supply at a constant flow rate throughout. When using a method of adjusting the flow rate with a valve provided upstream of the dripping port or a method of feeding water by controlling the flow rate from the water supply source to a perforated water pipe, the interval between the dripping ports is 2 to 10 cm. It is preferable that the thickness is 2 to 5 cm in consideration of the capillary force spreading in the lateral direction of the sewage and the overflow of the sewage.

  In the photocatalyst unit of the present invention, acidic sewage components are selectively removed by using solid adsorbent having an isoelectric point of 9 or more as an adsorbent and / or an inorganic adhesive component. And hydrophobic sewage components emulsified with a surfactant can be selectively removed.

  Moreover, a basic sewage component can be selectively removed by using an adsorbent and / or an inorganic adhesive component having solid acidity with an isoelectric point of pH 3 or less.

  Examples of the solid basic adsorbent include alumina and magnesium hydroxide, and examples of the solid basic inorganic adhesive component include an alumina binder. On the other hand, examples of the solid acidic adsorbent include colloidal silica, and examples of the solid acidic inorganic adhesive component include a silica binder.

  When using alumina as the solid basic adsorbent, it is preferable to use a boehmite-like crystal having an average particle size of 100 nm or less, and the volume fraction of the adsorbent in the coating film provided on the surface of the inorganic porous body. Is preferably 25 to 45%.

  Since active radicals move about several microns in water, it is desirable to disperse the photocatalyst material and the adsorbent uniformly within a range of several microns or less. However, in the case of alumina, there is a concern about secondary aggregation. In order to reduce the size of the aggregate to several microns or less, the average primary particle size should be 100 nm or less. The lower limit of the average particle diameter is not particularly limited, but 10 nm or less is technically and economically difficult. The average particle diameter of alumina is more preferably 30 to 90 nm.

  For example, when purifying the concentration of diethyl phthalate, which is said to be one of the environmental hormones, to 0.1 ppm or less, the volume fraction of the adsorbent in the coating film provided on the surface of the inorganic porous material is If it is less than 25%, the amount of alumina that adsorbs the removal component diethyl phthalate is small, so the concentration of diethyl phthalate in the sample cannot be reduced below the required concentration. Further, if the volume fraction of the adsorbent in the coating film provided on the surface of the inorganic porous body exceeds 45%, a phenomenon that the adsorbent falls off the coating film is not preferable. The volume fraction of the adsorbent in the coating film provided on the surface of the inorganic porous body is more preferably 35 to 43%.

  Furthermore, a hydrophobic sewage component is selected by using a flat photocatalyst having a water contact angle of 40 to 60 ° when the coating film is provided on a smooth surface such as a slide glass. Can be decomposed and removed.

  When purifying sewage containing a hydrophobic sewage component, activated carbon can be used as an adsorbent. Conventionally, activated carbon having a pore size as small as possible and a large surface area has been used. However, in the present invention, contrary to the conventional method, the pore size is large and precipitates in the coating liquid. Those having an average particle size that does not cause the occurrence of the problem are preferably used. As described above, since active radicals move several microns in water, it is desirable to uniformly disperse the photocatalytic material and the adsorbent in the coating solution within a range of several microns or less. In the case of activated carbon, the size is already a few microns, so the activated carbon in the coating solution must be almost monodispersed, but the particle wettability is strictly controlled to ensure monodispersity. It is important to do so, and the size of the pore diameter is greatly limited. As the activated carbon, the ratio of the sum of the volumes of pores having a pore diameter of 10 nm or more is 19% or more of the total pore volume, ((sum of volumes of pores having a pore diameter of 10 nm or more / total fineness). Pore volume) × 100 is 19% or more), and the average particle size is 10 μm or less. By using the activated carbon, the wettability of the waste water containing hydrophobic sewage components to the pores is greatly improved, and the dispersibility of the activated carbon in the photocatalyst coating liquid is also improved. Since the dispersibility of the activated carbon is greatly improved, it is difficult to inhibit the photocatalytic activity in the photocatalyst-supporting porous material, and when the volume fraction of the activated carbon in the coating film (photocatalyst layer) is up to 75%, the sewage components are completely decomposed by the photocatalyst. Sex can be maintained. The ratio of the sum of the volumes of pores having a pore diameter of 10 nm or more is more preferably 19% or more, and further preferably 25% or more of the total pore volume. In the activated carbon, the upper limit of the ratio of the total volume of pores having a pore diameter of 10 nm or more to the total pore volume is preferably 50%. This is because, when the ratio of the large pore diameter increases, it contributes to wettability in water, but the surface area decreases and the activated carbon loses its original adsorption ability. Further, although there is no particular lower limit to the average particle diameter, it is difficult technically and economically if it is 1 μm or less.

Moreover, it is preferable that the volume fraction of the activated carbon in the coating film provided on the surface of the inorganic porous body is 40 to 75%. By setting the content ratio of the active pair within the above range, for example, using an apparatus having a minimum purification capacity of 25 L / m ² , the pesticide waste liquid containing ipconazole, which is one of the hydrophobic sewage components, is purified. In this case, it is possible to purify ipconazole to a concentration of 1.0 ppm or less. If the volume fraction of the activated carbon is less than 40%, the amount of activated carbon that adsorbs the removal component may be less than the required concentration of decomposition target, and if it exceeds 75%, the absolute amount of activated carbon increases and the UV shielding effect. In some cases, the decomposition due to the photocatalytic activity does not proceed completely and the reuse becomes impossible.

  The contact angle of the coating film varies depending on the type of adsorbent and inorganic adhesive component used. Therefore, in order to control the water contact angle of the coating film provided on the smooth surface to 40 to 60 °, hydrophobic colloidal silica is used as an adsorbent and titania binder is used as an inorganic adhesive component when preparing the coating liquid. It is good to use. Since the mixing ratio varies depending on the type of the adsorbent and the adhesive component, the water contact angle may be confirmed by forming a film on, for example, a slide glass using the prepared coating liquid.

  In the present invention, the photocatalyst unit that has adsorbed the filth in the liquid to be purified in this way irradiates the coating film (photocatalyst layer) on the plate-like photocatalyst-supporting porous body with sunlight, and the adsorbed filth is photocatalyzed. Decomposes by material.

[Decomposition of adsorbed waste by photocatalytic material]
In the photocatalyst unit of the present invention, first, the filth in the liquid to be purified is adsorbed with an adsorbent, and then the adsorbed filth is decomposed with sunlight and a photocatalytic material. Therefore, it is not necessary to consider the material transport / adsorption rate, and the decomposition rate simply depends on the amount of ultraviolet light.

Therefore, as a result of examining the dependency of the decomposition of the contaminants on the amount of light, the present inventors found that the decomposition rate was R = 3.86 × 10 ⁻⁴ × I ^{0.851 in} the case of the photocatalytic unit of the present invention (where R : Reaction rate constant, I: ultraviolet light quantity), and was found to be proportional to the 0.85th power of the light quantity.

  On the other hand, the amount of ultraviolet light contained in sunlight varies greatly depending on the time zone, direction, and angle with respect to the ground, and it was also found that an angle range of 45 to 60 degrees can obtain the strongest ultraviolet light.

As for the direction, the south direction is most susceptible to the amount of ultraviolet rays, and the direction dependency of the amount of ultraviolet rays is generally as follows.
North: East: South: West = 25: 70: 100: 70

  For this reason, in order to efficiently use the ultraviolet rays contained in sunlight, it is preferable to avoid the installation in the north direction as much as possible, and the angle with respect to the ground should be 45 to 60 degrees. Actually, as a result of investigating the regeneration behavior of the contaminated unit under the condition of 45 degrees or 80 degrees installed in the south direction, a difference of 1.4 times occurred in the decomposition speed. This is in good agreement with the above considerations.

  FIG. 1 is a graph showing the angle dependence of the amount of ultraviolet light in fine weather (November 4, 2005, Gifu City, facing south), and FIG. 2 is a graph showing the difference in decomposition speed depending on the angle. In FIG. 2, the actual number of exposure days is the number of days in which a unit that has adsorbed filth is installed facing south.

  In addition, the angle dependence of the ultraviolet light quantity of FIG. 1 is the ultraviolet illuminance meter “UVR-2” (( Using Topcon Co., Ltd.), the light receiving part was tilted at an arbitrary angle, and the illuminance at that time was read and measured.

Further, the difference in decomposition speed depending on the angle of FIG. 2 was measured as follows.
The stand containing the unit that treated the seed disinfecting waste liquid installed in a place where there is no light blocking around the outdoors was set at an angle of 45 degrees and installed on the sunny south surface.

  For another unit that was processed in the same manner, the angle of the gantry containing the unit was set at 80 degrees, and the unit was similarly installed on the south facing surface.

  After 0, 1, or 2 days after installation, the mat in each unit is cut out to a 5 × 5 cm size, and the pesticide contained therein is extracted with methanol, and subjected to high performance liquid chromatography. Quantified.

  Calculate the remaining amount of pesticide remaining in the mat from the determined concentration of pesticide and the amount of methanol used for extraction, determine the difference from the outdoor installation day 0 as the decomposition amount, and the number of outdoor installation days on the horizontal axis Taking the amount of decomposition on the vertical axis, each plot was linearly approximated, and the difference in decomposition speed was determined from the slope.

  In the present invention, it is preferable to use an angle-adjustable unit storage stand that can adjust the unit to an angle suitable for each step in the purification step and the disassembly step.

  The structure of the gantry is not particularly limited as long as it is a unit storage gantry capable of adjusting the angle, but for example, a structure having a rotating shaft at a high position near the center of the unit can be cited as one of the preferable structures. As a result, space saving of the apparatus and labor saving of angle adjustment can be achieved.

  The feature of the present invention is that an indicator for knowing whether the photocatalytic unit whose angle has been adjusted in this way can sufficiently obtain the amount of ultraviolet light necessary to decompose and regenerate the adsorbed waste, That is, an indicator for determining the timing for switching from the decomposition process to the adsorption process is attached to the flat plate-like photocatalyst-supporting porous body or its support frame.

[indicator]
For the indicator used in the photocatalytic unit of the present invention, a dye that fades due to ultraviolet rays in sunlight is used. This indicator is preferably one that does not cause fading due to heat, water, moisture, or the like.
The inventors of the present invention have the following formula, which is said to be relatively fast for fading due to sunlight.

The following four types of azo dyes, Oil Orange R, Oil Red B, Oil Red, and PAN, were expressed as follows.

  That is, each dye dissolved in acetone is impregnated into water-resistant paper, exposed to ultraviolet light from a BLB (black light blue) lamp or visible light from a fluorescent lamp, and the color fading speed of the dye-carrying paper due to the decomposition of the dye is determined for each dye. The change in absorbance at λmax of the dye was followed. Next, while calculating the light intensity ratio between visible light and ultraviolet light contained in sunlight, the number of days required for fading under average sunlight was predicted based on these basic data. Since the photocatalytic unit of the present invention requires at least three days or more to obtain the ultraviolet light amount necessary for regeneration, it was found that Oil Red and Oil Red B are too fading and are not suitable as indicators. . On the other hand, it was found that Oil Orange R, 1- (2-pyridylazo) -2-naphthol (PAN) has a good balance between the expected reproduction period and the fading speed and is suitable for the desired indicator.

  FIG. 3 is a graph showing the difference in the number of days required for fading with a pigment. The initial abs on the horizontal axis is the absorbance at λmax of the dye-carrying paper before fading, and the number of days required for fading on the vertical axis is the absorbance (abs) at λmax of the dye-carrying paper is 0.1 or less. It is the number of days required to become.

  FIG. 3 shows the results of studies on four types of azo dyes, Oil Orange R, Oil Red B, Oil Red, and PAN.

  That is, each dye dissolved in acetone is impregnated into water-resistant paper, exposed to ultraviolet light from a BLB (black light blue) lamp or visible light from a fluorescent lamp, and the color fading speed of the dye-carrying paper due to the decomposition of the dye is determined for each dye. The change in absorbance at λmax of the dye was followed. Next, while calculating the light intensity ratio between visible light and ultraviolet light contained in sunlight, the number of days required for fading under average sunlight was predicted based on these basic data.

  Absorbance was measured by using a UV-visible spectrophotometer “UV-2100” (Shimadzu Corporation) and measuring the reflection spectrum using an integrating sphere.

  Oil Orange R [1- (phenylazo) -2-naphthol] and / or PAN is suitable as the indicator pigment, but the indicator used in the present invention does not cause fading due to heat, water, moisture, etc. In particular, it was determined whether or not the oil orange R and PAN satisfy this condition. It was found that both the oil orange R and the orange orange R were discolored by heat.

  Therefore, the indicator form is particularly preferably one in which water-resistant paper carrying PAN is sandwiched between weather-resistant substrates to prevent it from getting wet in the rain.

In order to obtain high visibility when the amount of light of 70 mW / cm ² is obtained by fading of PAN-supported paper by sunlight, it is necessary to increase the degree of fading. Therefore, the amount of fading at an arbitrary time was examined by changing the initial PAN loading. As a result, it can be seen that the amount of light received by the indicator and the degree of fading correlate with the amount of PAN carried, and the relationship is expressed by the following equation 2.

D = 0.0019V + 0.5051 (2)
(However, D: Initial ABS (absorbance) with maximum fading, V: Integrated ultraviolet light (mW / cm
² ))

  For the indicator used in the present invention, it is desirable to use a dark base material among the base materials sandwiching the dye-carrying paper so that the color change becomes clearer, and the indicator using PAN is orange. Therefore, blue, green, blue-violet, black and the like are preferable. Further, the base material to be the cover is preferably a highly transparent one, and examples thereof include an acrylic resin plate, a polypropylene plate, a polyethylene terephthalate plate, and a polycarbonate plate.

  The indicator thus produced gradually faded in color as the integrated light quantity increased, and the change could be easily discerned visually. Moreover, the fading shows the integrated ultraviolet light quantity with good reproducibility with almost no influence of the weather.

  FIG. 4 is a graph showing the relationship between the accumulated ultraviolet light amount and ABS (absorbance) in each period, and it can be seen from this figure that fading shows the accumulated ultraviolet light amount with good reproducibility with almost no influence of the weather. .

The indicator was produced as follows.
20 ml of PAN prepared to 700 ppm with acetone was poured into a petri dish, and a separation filter paper “No. 2S 55φ” (ADVANTEC) having a diameter of 55 mm was put therein, sealed, and allowed to stand for 12 hours. After 12 hours, this was pulled up and dried at 40 ° C. in an oven.

  This is cut into 2 cm x 1.5 cm, and pasted on a black acrylic plate "Acrylite" (Mitsubishi Rayon Co., Ltd.) with a thickness of 5 cm x 2.5 cm and a thickness of 2 mm. A transparent acrylic board “Acrylite” (Mitsubishi Rayon Co., Ltd.) was placed as an indicator.

The measurement of ABS (absorbance) was performed by reflection spectrum measurement using an integrating sphere using an ultraviolet-visible spectrophotometer “V670” (JASCO Corporation).
The measurement of the integrated ultraviolet light amount was obtained by integrating the ultraviolet light amount in sunlight measured every hour.

  The way the color of the indicator looks depends on the time zone, the difference in the light environment where the indicator is placed, and the sensitivity of the observer, so it is easy for anyone to reach the target fading level under any conditions It is desirable to be able to judge. Therefore, in the photocatalytic unit of the present invention, it is preferable to attach a color sample that reproduces the faded state of the indicator together with the indicator.

In an indicator using PAN as a dye and an acrylic resin plate as a cover, a color sample showing the degree of fading when the integrated light quantity is 70 mW / cm ² is X = 66.0 in terms of spectroscopically X, Y, and Z. To 73.0, Y = 67.0 to 75.0, Z = 61.0 to 70.0 are preferable, X = 68.6 to 68.8, Y = 69.0 to 69. 1, Z is more preferably in the range of 63.4 to 64.6.

This color swatch is preferably a gradation showing the change from the color before fading to the color after fading. For example, the color swatch when the accumulated light quantity is 70 mW / cm ² is X = 58.0 to 61.0. , Y = 54.0-55.0, Z = 23.0-28.0 to the above-mentioned X = 66.0-73.0, Y = 67.0-75.0, Z = 61.0 A color sample that changes to a range of ˜70.0 may be used.

  It is possible to easily determine that reproduction has been completed when the color sample in the faded state is aligned with the indicator, the color of the indicator is compared with the color sample, and the color of the color sample is reached.

  FIG. 5 is a plan view showing a different example in the case where an indicator and a color sample are arranged together. Reference numeral 1 denotes an indicator and 2 denotes a color sample.

The present invention also provides a method of using the photocatalytic unit.
In the method of using the photocatalyst unit of the present invention, in the photocatalyst unit of the present invention described above, when the indicator fades to a predetermined color tone, the operation of switching from the decomposition process to the adsorption process is performed, and the purification process of the liquid to be purified is repeated. Do.

EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.
Example 1
(1) Production of flat photocatalyst-supported porous body Photocatalytic titanium oxide (anatase-type titanium oxide, average particle size 20 nm) slurry [manufactured by Titanium Industry Co., Ltd., “PC-203”, solid content 20 mass%] 11.6 g, Amorphous titania binder (solid component 7.1 mass%) 12.3 g, which is an inorganic adhesive component, activated carbon (manufactured by Phutamura Chemical Co., Ltd., “Dazai activated carbon SA-1000”, with a pore volume having a pore diameter of 10 nm or more 1.1 g of a sum ratio of 20% of the total pore volume and an average particle size of 10 μm or less) is a mixed solvent of ethyl cellosolve, 1-propanol and water (ethyl cellosolve / 1-propanol / water = 45/45 / 10, mass ratio) to prepare a coating liquid having a solid component concentration of 1.1 mass%.
The water contact angle when this coating solution was applied to the surface of the slide glass was 58 °.
Next, the inorganic porous material is coated on the surface of a silica glass nonwoven fabric having a water retention rate of 1000% by mass, a suction height of 100 mm, a thickness of 6 mm, and a basis weight of 700 g / m ² (fiber diameter: 7 μm). by applying a liquid, a titanium oxide photocatalyst 15 g / ^{m 2} and activated carbon 7.1 g / ^{m 2} carries a volume fraction of 26% of the titanium oxide photocatalyst in the coating film, the volume fraction of 62% activated carbon photocatalyst carrying A porous body was produced.

(2) Production of integrated light quantity indicator 0.49 g of PAN was dissolved in 699.51 g of acetone to produce a PAN solution having a concentration of 700 ppm. 20 g of this solution was poured into a glass petri dish, where ADVANTEC made separation filter paper No. One piece of 2S 55φ was immersed, sealed from light, and allowed to stand for 12 hours. After 12 hours, the filter paper was pulled up and dried in an oven at 40 ° C. to obtain an integrated light quantity indicator. This is cut into 0.5 cm x 4 cm and pasted on a black acrylic plate with a thickness of 2 mm together with a color sample of X = 68.7, Y = 69.1, Z = 64.0, and a transparent acrylic plate with a thickness of 2 mm The integrated light quantity indicator was produced.

(3) Purification of sewage The plate-like photocatalyst-supported porous body produced in (1) above is cut into a flat plate having a size of 53.3 cm in length and 30.5 cm in width, and is mounted on an angle-adjustable gantry, and the angle with respect to the ground The photocatalyst unit adjusted to 80 degrees was previously washed with 2.4 L of water.
Seed disinfection waste solution 4 containing ipconazole 3.4 ppm and total organic carbon concentration 609 mg / L obtained by soaking rice sterilized with paddy rice seed disinfectant [Kumiai Chemical Co., Ltd., “Techlead C Flowable”] Purification was performed by dropping 0.5 L onto the disinfected photocatalyst unit at a pressure of 0.1 MPa gauge and a flow rate of 200 ml / min from a dripping port provided at 2.5 cm intervals on the upper end of the unit. After completion of purification, 2.4 L of water was dropped from the same dripping port at a pressure of 0.1 MPa gauge pressure and a flow rate of 200 ml / min to wash the unit.

(4) Repeated regeneration The integrated light quantity indicator prepared in (2) above is attached to the gantry containing the unit treated with the seed disinfecting waste liquid in (3), the gantry angle is set to 45 degrees, and the south direction is sunny. Installed on the surface. Compare the fade of the integrated light quantity indicator with the color sample and visually confirm that the color has become lighter than or equal to that of the color sample. The seed disinfection waste liquid was treated by the method described above. This was repeated, and the waste liquid treatment was performed a total of 5 times. The concentration of ipconazole in the collected cleaning liquid and cleaning liquid was below the emission standard value.
Table 1 shows the relationship between the treatment amount and the ipconazole concentration at each number of repetitions.

  FIG. 6 is a plot diagram showing the relationship between the treatment amount and the ipconazole (IPC) concentration at each number of repetitions.

  The concentration of ipconazole was analyzed by reversed layer liquid chromatography, and the concentration in the sample solution was calculated from the corresponding peak area based on a calibration curve indicating the relationship between the concentration and peak area prepared in advance. Asked.

  The photocatalyst unit of the present invention is a photocatalyst unit used for purification of adsorption-type sewage, and can effectively purify various sewage using a flat photocatalyst-supported porous body having a coating film containing a photocatalyst material and an adsorbent. At the same time, it can be used repeatedly by efficiently utilizing sunlight and recovering its purification performance, and is suitably used for purification treatment of various sewage, for example, agricultural waste liquid and waste liquid in hydroponic cultivation.

It is a graph which shows the angle dependence of the ultraviolet light quantity at the time of fine weather. It is a graph which shows the difference of the decomposition speed by an angle. It is a graph which shows the difference in the number of days required for fading with a pigment | dye. It is a graph which shows the relationship between the integrated ultraviolet light quantity in each period, and ABS. It is a top view which shows a different example at the time of arrange | positioning both an indicator and a color sample. It is a plot figure which shows the relationship between the processing amount in each repetition frequency, and an ipconazole (IPC) density | concentration.

Explanation of symbols

1 Indicator 2 Color sample

Claims (12)

  A flat photocatalyst-supporting porous body having a coating film containing a photocatalyst material and an adsorbent is provided at least on the surface that is exposed to sunlight, and the flat photocatalyst-supporting porous body is at least 40 to 90 degrees with respect to the ground. The degree of inclination can be freely adjusted so that the angle falls within the range, and the liquid to be purified is provided in the width direction at the upper end portion of the flat plate-like photocatalyst-supporting porous body that is raised at an angle within the range. Supplying from a plurality of dripping ports and flowing into the flat photocatalyst-supporting porous body to adsorb filth, and then irradiating the coating with sunlight, and repeatedly decomposing the adsorbed filth with a photocatalytic material In order to determine the switching timing from the decomposition treatment to the adsorption treatment, an indicator using a dye that fades due to ultraviolet rays in sunlight is provided at the start of the decomposition treatment. Jo photocatalyst carrying porous or photocatalytic unit, characterized in that attached to the support cradle.   The photocatalyst unit according to claim 1, wherein the indicator is a paper in which water-resistant paper carrying a dye fading with ultraviolet rays is sandwiched between weather-resistant substrates.   The photocatalytic unit according to claim 1 or 2, wherein the dye fading with ultraviolet rays is 1- (2-pyridylazo) -2-naphthol and / or 1- (phenylazo) -2-naphthol.   The photocatalyst unit according to any one of claims 1 to 3, wherein a color sample is attached together with the indicator.   At the upper end of the flat photocatalyst-carrying porous body, the liquid to be purified is supplied from a plurality of dripping ports to flow into the flat photocatalyst-carrying porous body and adsorb the filth at an angle of 80 degrees or more with respect to the ground. The photocatalyst unit according to any one of claims 1 to 4, wherein the photocatalyst unit is adjusted to be.   The coating film is irradiated with sunlight, and when the adsorbed filth is decomposed by the photocatalyst material, the film is directed toward the south and adjusted to have an angle of 45 to 60 degrees with respect to the ground. The photocatalytic unit according to any one of the above.   The photocatalyst unit according to any one of claims 1 to 6, wherein a plurality of dripping ports for supplying the liquid to be purified are provided at intervals of 2 to 10 cm.   The photocatalyst unit according to any one of claims 1 to 7, wherein the support in the flat photocatalyst support porous body is made of an inorganic porous body.   The photocatalyst unit according to claim 8, wherein the inorganic porous body is a nonwoven fabric made of glass fiber.   The photocatalyst unit according to any one of claims 1 to 9, wherein the coating film contains an inorganic adhesive component.   The photocatalytic unit according to any one of claims 1 to 10, wherein the adsorbent is activated carbon.   The method of using a photocatalyst unit according to any one of claims 1 to 11, wherein the photocatalyst unit is switched from a decomposition process to an adsorption process when the indicator fades to a predetermined color tone. .

Images