rexresearch.com
Panasonic Corp.
Photocatalytic Water Purification
Photocatalytic Water Purification
http://revolution-green.com/photocatalytic-water-purification-technology/
Panasonic Develops ‘Photocatalytic
Water Purification Technology’ – Creating Drinkable Water
with Sunlight and Photocatalysts
Demonstration machine of Photocatalytic Water Purification Technology
Demonstration machine of Photocatalytic Water Purification Technology
In India, approximately 70 per cent of the population uses water not from taps but primarily that from under the ground. Leaching into it are harmful substances such as agrochemical residues, the arsenic of Himalayan ore veins, and hexavalent chromium produced from leather tanneries. This contamination has come to be seen as a societal problem, having caused health problems for as many as 50 million people.
Many other countries throughout Africa, Asia and South America rely on underground water often contaminated. Even developed countries like the USA have ground water supplies being compromised by fracking activities
To solve such drinking-water issues worldwide, Panasonic has developed its own photocatalytic water purification technology. This technology uses photocatalysts and the UV rays from sunlight to detoxify polluted water* at high speeds, creating safe and drinkable water. This breakthrough caught much attention when Panasonic unveiled it in Tokyo at Eco-Products 2014.
With two core technological developments, Panasonic’s Photocatalytic Water Purification Technology processes water more efficiently
1. Achieving a High Capacity to Decompose Toxic Substances with Synthesis Technology of Photocatalysts
When photocatalysts are exposed to ultraviolet light, formed reactive oxygen purifies the toxic substances. However, TiO2, a kind of photocatalyst, comes in extremely fine particles and is troublesome to collect once dispersed in water. Methods of binding TiO2 to larger matter have hence been used, but they in turn suffered a loss of surface active site. Panasonic developed a way of binding TiO2 to another particle, zeolite, which enables photocatalysts to maintain their inherent surface active site. Moreover, since the two particles are bound together by electrostatic force, there is no need for binder chemicals.
2. Achieving High Processing Speeds with Water Purification Technology that Disperses Photocatalytic Materials
When these novel photocatalytic particles are agitated, TiO2 is released from the zeolite and dispersed throughout the water. As a result, reaction speed is markedly elevated compared to conventional methods of fixing TiO2 on a surface of substrates, enabling a large volume of water to be processed in a short amount of time. Leaving the water still will cause TiO2 to bind to zeolite again, making it easy to separate and recover the photocatalysts from the water – allowing them to be reused at a later time.
Establishing an infrastructure for supplying safe drinking water
Along with being driven by light, another key feature of photocatalysts is that they remove any necessity of pharmaceuticals. As such, they offer a low-cost and environmentally friendly way of treating water.
Panasonic aims to provide this water to small rural communities, for example, using trucks equipped with photocatalytic water purification systems. Beyond this, the company is looking at linking up with local water supply operators to establish water purification facilities, and is also considering the licensing of this technology to businesses. Panasonic is working to lower costs and maintenance requirements with the water purification systems – its aim being to make this technology available right across India and other emerging nations.
http://news.panasonic.com/global/topics/2014/30409.html
Dec 11, 2014
Panasonic Proposals for "A
Better Life" at Eco-Products 2014
Photocatalytic water purification technology
Panasonic is introducing for the first time the evolution of its "photocatalytic water purification technology," which uses the power of UV rays in sunlight to detoxify water that may contain harmful substances like arsenic and hexavalent chromium. The demonstration explains in a straightforward manner how this technology works.
PURE WATER PRODUCTION METHOD
JP2012096166
JP2012096166
PROBLEM TO BE SOLVED: To provide a pure water production method for generating an active oxygen species in a solution by using a photocatalytic reaction, and removing deposited fine particles;
SOLUTION: Titanium oxide (IV) obtained by a chemical bond of an oxo acid, that is a photocatalyst 1, and a halogen is provided in water. The titanium oxide (IV) is irradiated with an ultraviolet by a light source 2 while a gas that contains oxygen in water is mixed into water by an air diffusion means 3, so that the active oxygen species such as a hydrogen peroxide is generated in a reaction liquid, which reacts with the fine particles such as an organic matter floating on a liquid or adhering to a solid surface to express the removal effect.
[0001]
The present invention relates to bacteria and fungi, or viruses such as antimicrobial, to generate antimicrobial component, such as reactive oxygen species and the halogen oxide having the ability to inhibit in the liquid, to produce pure water by removing the organic matter from the raw water decomposing organic substance attached to the membrane or the suction device used for removal, or by inhibiting the growth of microorganisms, a method for producing pure water which can improve the long term performance of the membrane or the adsorber.
[0002]
Conventionally, the water purification process of this type, generated ozone, or what the chemical solution of hydrogen peroxide is added directly to the system for cleaning such films are known.
For example, as a device for conventional to conduct the pure water manufacturing method of this kind, as shown in Figure 3, ultra-pure water production system is known (for example, see Patent Document 1).
[0003]
This ultrapure water production apparatus 101, and the ozone generator 102, the ozone gas dissolution apparatus 103, ozone is provided with a basic medicine adding device 104 to autolysis, intended to clean the inside of the pipe up to the point of use 105 is there.
The residence by long-term use in ultrapure water production apparatus 101, in order to remove particulates, such as accumulated microorganisms dead, sterilized by supplying ozone, after decomposition, and decomposing and removing the ozone remaining continuously With, without stopping the apparatus, and are capable of performing the cleaning of the system.
[0004]
Patent Publication No. 2008-221144
[0005]
Conventional ultrapure water production system described in Patent Document 1, since it is possible to perform the supply of the ozone in the apparatus, the decomposition continuously has the advantage that the operation is simple, in order to decompose ozone it is necessary to provide the basic chemicals of the appropriate concentration, when the concentration of the basic drug is insufficient ozone results in the residual, and the problem of concentration deteriorates the pipe by excessive become the basic component there were.
Moreover, for supplying the drug solution, there is a problem that must manage the chemical.
Therefore, the addition of liquid medicine is demanded unnecessary cleaning system.
[0006]
The present invention is intended to solve such conventional problems, capturing organic substances, such as dead microorganisms present in the system by the photocatalyst, it can be decomposed further oxo acids such as phosphate compound photocatalyst and compounds, by containing a halogen such as fluorine, the photocatalytic surface, and the hydrogen peroxide to generate active oxygen species such as hydroxyl radicals, superoxide radicals, and can be released from the photocatalyst surface in the system.
It is readily decomposed in water, to disappear in a short period of time is required to remove by chemical solution.
And an object thereof is to provide a method for producing a purified water that does not degrade the pipe by a chemical solution.
[0007]
Water purifying method of the present invention, in order to achieve the above object, in the pure water production system, the titanium oxide is a photocatalyst containing oxo acid and a halogen, an ultraviolet lamp as a light source for exciting titanium oxide When, and a, to generate active oxygen species by the photocatalytic effects are those to be used for the decomposition of organic matter, it is intended thereby achieve the intended purpose.
[0008]
In accordance with the present invention, in the the system of the pure water production system, and the photocatalyst disposed on the upstream side of the pure water production unit, a light source for exciting the photocatalyst due to the configuration provided with, a liquid It generates reactive oxygen species by the photocatalytic reaction in the medium, in order to decompose and remove the particulates are captured on the photocatalyst, a high removing effect can be obtained.
By further containing oxo acid and a halide in the photocatalyst, it is possible to generate active oxygen species such as hydrogen peroxide may be present in relatively short stable in liquid and diffuse to the remote location in the pipe it is possible to decompose the particulates are, the conventional water purification methods, the effect is obtained of increasing cleanliness.
Moreover, such reactive oxygen species, to self-decompose in a short time as compared with ozone, is unnecessary degradation treatment with drugs, active substances such as ozone does not leak out of the system and degrade the pipe difficult therefore, the effect is obtained that a long period of time can maintain the performance.
[0009]
It shows a conventional ultrapure water production system graph showing the measurement results of the hydrogen peroxide in the first embodiment of Fig invention showing the pure water manufacturing method flow of the first embodiment of the present invention
[0010]
Invention described in claim 1 of the present invention, there is provided in the system of the pure water production device, a photocatalyst-containing oxo acid and a halogen disposed on the upstream side of the pure water generating means, for exciting the photocatalytic comprising a light source, which was characterized by decomposing the organic substances existing in the inner wall surface and the piping of the water and the pure water production device in the system of the pure water production device by the generated active oxygen species from the photocatalytic It is.
Thus, active oxygen species having the decomposition of the organic matter by the strong oxidizing power by the photocatalytic reaction, is generated in the liquid, it is diffused and can be performed cleaning of the system.
[0011]
In addition, the invention of claim 2, wherein the photocatalyst is a titanium oxide (IV), the light source is one that has been characterized by a UV lamp.
Thus, a high oxidation energy of titanium oxide, can be used in combination with high oxidative energy by ultraviolet rays, the decomposition of organic matter, it is possible to enhance the effect of suppressing microorganisms.
[0012]
In addition, the invention of claim 3, wherein is obtained by characterized in that it comprises a diffuser means for dissolving a gas containing oxygen in the water.
By increasing the concentration of oxygen dissolved in the water, increasing the amount of active oxygen species generated by the photocatalyst, it is possible to enhance the degradation effect.
[0013]
In addition, the invention of claim 4, wherein is one in which an oxo acid was characterized by a phosphate compound.
Thus, among the reactive oxygen species, it is possible to produce what is long relative life, such as hydrogen peroxide, it can be expanded to a range capable of obtaining acts to extensively spread.
[0014]
In addition, the invention of claim 5, wherein the halogen is a fluorine, the fluorine is at least a portion the photocatalyst is one that has been characterized by chemically bonded.
By allowing fluorine chemically bonded to the photocatalyst, it is possible to significantly increase the generation quantity of active oxygen species.
Furthermore, because of the chemical bonds, which can be generated stably.
[0015]
(Embodiment)
[Pure water production method]
The flow of the pure water manufacturing method of the present invention is shown in FIG.
In order to produce pure water, filtering raw water such as city water or underground water, adsorption, be done by removing the impurities co-exist by processes such as deionization process it is generally.
[0016]
In the filtration step, it is used eye slightly coarse filter for removing 10μm or more coarse particles from 5.
For example, resin, natural fibers, or in compacted fibers such as metal and those in non-woven fabrics, and those woven into meshes, it is processed into a plate, or roll, is used by passing through the water.
[0017]
The adsorption removal step, a column packed with an adsorbent, such as organic materials and inorganic materials dissolved is passed through the water is removed in the adsorption tower.
When used as an adsorbent, for example activated carbon, but use a granular, because the particle size of the resistance increases small, it is preferable to consider the shape of the activated carbon in accordance with the operating flow rate.
Moreover, so that the activated carbon is not released into the water, it is preferably covered with such a mesh.
[0018]
The deionization process, by contacting the water to the ion exchange resin to remove the ionic substances such as metal ions dissolved in the water.
For example, it may be used as the column filled with those processing the ion exchange resin beads.
Again activated carbon is also ion-exchange resin or be covered with such a mesh that does not enter the water, it is preferred to adjust the particle size.
[0019]
In order to further increase the cleanliness of pure water, heat treatment and microbial treatment in the preceding stage, heating distillation, using such electroosmotic and reverse osmosis membrane or a hollow fiber membrane are referred to as the RO membrane in the subsequent stage, placing the UV lamp I can.
By combining these processes, it is possible to produce pure water.
[0020]
In the present invention, the pure water is very low impurities, such as organic materials and inorganic materials dissolved or suspended, refers to the high-purity water.
As an index, electrical conductivity, the number of airborne particles, TOC concentration, and the like viable cell count, and sets the value depending on the intended use.
For example, grades of water, referred to as ultra-pure water for industrial use, 18M Ohms or greater in electrical conductivity, TOC is stipulated to as 0.05mg / L or less.
[0021]
[Production of reactive oxygen species by the halogen-containing titanium oxide]
In the system for producing pure water, contact with a liquid, or providing a photocatalyst one to impregnate, to provide a light source 2 for emitting light for exciting the vicinity.
The interior of the system for producing pure water, to produce pure water from raw water refers to piping or inside the apparatus until the point of use for use in the space is sealed so that no contamination from outside the system is there.
The bottom of the photocatalyst 1, is provided with a diffusing unit 3 for mixing with refined in the liquid by introducing pressurized gas into the pipe.
It provides fine particles of organic matter in the raw water adsorption, in front of the pure water generating means 4 for generating the pure water by filtration and the like.
By providing a photocatalyst one in front of the pure water generator 4, organic substances in the raw water, for example, particulate organic carbon known as TOC, also captures and dissolved organic carbon, called DOC, addition to decompose by adsorption, in water and bacteria that are present, Cryptosporidium, were kill microorganisms such as protozoa, such as green algae, it is possible to remove impurities in the water by decomposing the cell debris.
In the present invention, the photocatalyst 1, and is for containing oxo acid and a halogen, in the water by irradiation with excitation light in the life such as hydrogen peroxide to generate a long reactive oxygen species, organic matter is suspended in water was decomposed organic matter deposited on the surface of the pure water production unit 4 decomposition, it can be removed.
By this arrangement, it is possible to reduce the load on the pure water production unit 4, it is possible to allow the preparation of long-term stable pure water.
Note that the generated active oxygen species, because they are completely removed by the pure water production unit 4, in a subsequent stage of the point of use, water that can be used is obtained as a pure water.
[0022]
Furthermore, in order to increase the concentration of active oxygen species generated gradually, it is preferable because the effect is enhanced to remove organic materials deposited and controls the operation such as stopping for a predetermined time passing water.
Piping, not altered by oxidative power of the generated reactive oxygen species, and the light emitted by the light source 2, use one that does not altered for example by ultraviolet light.
For example by a metal or an inorganic material, or those coated with these surfaces it can be used.
If metal, stainless steel, aluminum, copper and the like, as long as it is an inorganic compound, such as ceramic or glass may be used.
Stainless steel is preferred from the viewpoint of the light source 2 is reflected to increase the photocatalytic reaction efficiency.
[0023]
The pipe, in order it is installing the photocatalyst 1 and the light source 2, to be used reactions as the distance between the photocatalyst 1 and the light source 2 is short in order to increase the efficiency and the light emitted from the light source 2 efficiently, As to surround the light source 2, it is preferably a structure of arranging a photocatalyst 1.
Since the lamp is a light source 2 is the life, for easy replacement in advance, from the outside of the pipe may be disposed through a material that transmits ultraviolet rays such as quartz glass.
[0024]
The photocatalyst 1 of the present invention, titanium oxide, tungsten oxide, strontium titanate, niobium oxide, tantalum oxide, etc. may be mentioned.
Among these, in view of the strength of activity, titanium oxide is preferred.
[0025]
As the titanium oxide (IV), for example, anatase type titanium oxide, rutile titanium oxide, include brookite-type titanium oxide because the high photocatalytic activity can be obtained, anatase-type titanium oxide is preferable.
The "anatase type titanium oxide" in the present invention, in the powder X-ray diffraction spectrum measurement (using electrodes: copper electrode), and refers to a titanium oxide diffraction peak appears in the vicinity of a diffraction angle 2θ = 25.5 °.
[0026]
The titanium oxide addition to titanium dioxide, cited hydrous titanium oxide, hydrated titanium oxide, metatitanic acid, orthotitanic acid, titanium hydroxide, oxygen deficiency type titanium oxide, nitrogen substituted titanium oxide and sulfur substituted titanium oxide It is.
No particular limitation is imposed on the crystal form as long as it has a photocatalytic activity, amorphous, anatase, rutile, may be any of brookite type.
A combination of rutile and anatase titanium oxide, there is no problem even when combining different crystalline forms component.
[0027]
Is often titanium oxide is a powder form, by oxidizing the metal surface, such as a titanium plate, it is possible to form a titanium oxide thin film.
Also, by coating a titanium alkoxide may be formed titanium film by heat treatment.
The titanium powder was sprayed on a metal surface, it is possible to form a titanium oxide film.
[0028]
In addition, not intended to be limiting in any way be used Pt on the surface of the titanium oxide, Pd, Rh, Ru, Au, Ag, Cu, Fe, a metal such as Ni is covered.
In addition, it not intended to be limiting in any way be used a photocatalyst to contain a dopant metal such as Cr or V is enlarged an absorption wavelength of light on the surface.
[0029]
Titanium oxide is preferably in the range of the specific surface area of 200~350m2 / g, more preferably in the range of 250~350m2 / g.
Here, the specific surface area in the present invention was measured by the BET method (adsorption-desorption method of nitrogen), and a surface area value per powdered 1g of titanium oxide.
If the specific surface area is more than 200m2 / g, it can increase the contact area between the decomposed object.
[0030]
Light source 2, when using the titanium oxide (IV), is used one which generates light containing a wavelength range of the wavelength 350nm of 450nm which can activate.
The more are those having a strong emission peak, it is possible to perform excitation of efficiently titanium oxide with respect to input power.
For example, using a fluorescent lamp type black light straight pipe type, comprising a number of wavelengths around 380nm, since it is possible to irradiate efficiently wide range of the strong light, it can be suitably used when the area of the substrate is large.
Further, a halogen lamp, a xenon lamp, a light source such as a mercury lamp, it can be implemented by arranging such that large areas, such as by absorption is small mirrors and lenses of the ultraviolet can be irradiated.
[0031]
Further, as a light source with a strong emission peak in the wavelength, there are those using semiconductor devices.
For example, light emitting diodes, and semiconductor lasers may be used.
These irradiation area is small, because the size of the light source portion is small is suitable for the irradiation locally into smaller parts.
[0032]
The photocatalytic reaction, since oxygen is needed, in order to perform efficient reaction, it is insufficient in the amount contained in the liquid.
Therefore, a gas containing oxygen, such as enriched oxygen gas or air is mixed in the reaction solution, it is desirable to increase the amount of dissolved oxygen.
The diffusing means 3 for mixing a gas into the reaction liquid, and those of mixing a gas which has been compressed from a nozzle and blown into the liquid, is composed of a nozzle and the rotary body, which is provided with such suction effect gas into the liquid vigorously stirred Te, there is such as to mix the gas phase components in the liquid phase.
When it is sprayed from the nozzle, the shape of the nozzle, the bubble miniaturization that can be sprayed into a liquid, it may be mixed with more oxygen for a long time stabilized in the solution.
When you install the aeration tube of the porous body to the nozzle tip, the bubbles that are released into the liquid is miniaturization, dissolved amount of the water is increased.
Furthermore, it collides with the rotary body bubbles, and is miniaturized, it is possible to further long-term stability.
[0033]
Bubbles dispersed in liquid, it emerged over time, eventually returning to the gas phase.
In order to improve the efficiency of air bubbles in contact with the surface of the photocatalyst 1, in view of the fact that bubbles floats, by disposing the photocatalyst one on top of the diffuser means 3, the bubbles contact the surface of the photocatalyst 1 it becomes easier to the reaction increases, it is possible to increase the production amount.
Furthermore, the cell is arranged longer photocatalyst 1 in the vertical direction, the gas floats is possible to take a longer time in contact with the surface of the photocatalyst 1, it is possible to improve the reaction efficiency.
[0034]
The reactive oxygen species produced by the water purification process of the present invention refers to those having or hydroxyl radicals, superoxide radicals, singlet oxygen, hydrogen peroxide, ozone, etc. The oxidizing action, such as reactive oxygen species.
They oxidize organic compounds, decompose other, bacteria and fungi, protozoa, and targeted microorganisms such as viruses, these growth activities bacteriostatic and act to suppress the decomposition of the constituents are modified to work it is possible to obtain a bactericidal action to stop.
[0035]
The term "antimicrobial" as used herein, refers to be sterilized and / or degrading bacteria in the liquid phase, preferably it refers to inhibiting the proliferation of reducing and / or bacteria in the bacterial concentration in the liquid phase.
Specifically, it means that the antimicrobial component and fungi in the case of contact over 24 hours, the bacterial concentration in contact can be reduced two orders of magnitude more than the initial concentration.
In the present invention, the subject of antimicrobial activity is not particularly limited, for example, bacteria, fungi, include viruses such as, from the viewpoint of antibacterial activity, the bacteria are preferred.
As the bacteria, for example, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, MRSA, Bacillus cereus, include Klebsiella pneumoniae.
[0036]
Reactive oxygen species, for oxidizing power is strong, C-C bond is the basic skeleton of the organic matter (about binding energy 347kJ / mol) and, C-H bonds (binding energy about 415kJ / mol), or, C = C bond the binding of such π bond (bond energy of about 285kJ / mol) has been known to be cleaved by oxidation.
To disconnect the coupling, higher dissociation energy than the binding energy is required.
For example, strong oxidizing potential of the hydroxyl radicals are reactive oxygen species it is about 2.8V, because the dissociation energy of about 504kJ / mol, it is possible to oxidative decompose by cleaving the C-C bonds.
Such oxidizing agents are, because energy is large, contrary, there is a property that is very short unstable life (approximately 1 millisecond).
[0037]
Hydrogen peroxide is one of the reactive oxygen species, the oxidation potential is 1.77V, the dissociation energy is 319kJ / mol.
In this case, it can not be cut is lower than the energy that cleaves C-C bonds, it is possible to disconnect the π bonds of C = C double bonds.
In the case of large organic relatively molecular weight such as proteins and enzymes, but in order to fulfill the original function is an important three-dimensional conformation, active substances such as hydrogen peroxide which by the strong oxidizing power conformation of the denatured, it is possible to extinguish the original functions, it is possible to obtain a disinfection effect and antiviral effect.
The hydrogen peroxide minute oxidation potential is low, the stability is increased as compared with the hydroxyl radical there is a property that the life is long (about one hour or more).
It is possible to provide an antibacterial effect to the remote location in the liquid phase.
[0038]
These antimicrobial components are bacteria, it is reacted with the cells of microorganisms such as fungi or protozoa, all of these, or by oxidizing a part express antimicrobial activity.
[0039]
In the present invention, the oxo acid compound to be contained in the titanium oxide, the hydroxyl groups (OH) and is a compound having an oxo group (C = O), are present in an ion state in a liquid, generated in the photocatalytic surface It has the effect of converting the active oxygen species in a relatively stable state.
It is not clear is the mechanism that substances of the radical state is converted into stable compounds with oxo acids, but the structure containing much oxygen as the oxo acid, is coordinated to the radical, conversion to a more stable active substance It is considered to be intended to be.
The oxo acids include, but are not limited to, a general-oxo acid compounds can be used.
For example, when the oxo acid is a phosphoric acid compound, zinc phosphate, aluminum phosphate, potassium phosphate, calcium phosphate, silver phosphate (I), chromic phosphate (III), cobalt phosphate, ferric phosphate, titanium phosphate, iron phosphate (III), copper phosphate (II), lead phosphate (II), magnesium phosphate, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, sodium monohydrogen phosphate, dihydrogen phosphate sodium, lithium dihydrogen phosphate, tricalcium phosphate ammonium, potassium phosphate tribasic, calcium phosphate, sodium phosphate, phosphoric three lithium, sodium ammonium hydrogen phosphate, calcium hydrogen phosphate, magnesium hydrogen phosphate, diammonium hydrogen phosphate, dipotassium hydrogen phosphate, disodium hydrogen phosphate, polyphosphate, ammonium polyphosphate, potassium polyphosphate, sodium polyphosphate, metaphosphate, aluminum metaphosphate, potassium metaphosphate, sodium metaphosphate, hexametaphosphate sodium, adenosine triphosphate, adenosine diphosphate, the nucleic acid compounds, and the like.
[0040]
Also, when the oxo acid is a carbonate compound, ammonium carbonate, potassium carbonate, calcium carbonate, sodium carbonate, lead carbonate, barium carbonate, manganese carbonate, lithium carbonate, magnesium carbonate, ammonium hydrogen carbonate, potassium hydrogen carbonate, calcium hydrogen carbonate, strontium carbonate, cesium carbonate, cerium carbonate, iron carbonate, copper carbonate, etc. can be mentioned.
[0041]
Also, when the oxo acid is sulfuric acid compounds, sulfuric acid, zinc sulfate, aluminum sulfate, ammonium sulfate, potassium sulfate, calcium sulfate, ammonium bisulfate, potassium bisulfate, sodium bisulfate, tin sulfate (II), strontium sulfate, cesium sulfate , ferrous sulfate, manganous sulfate chromic acid, ferric sulfate, titanium sulfate, copper sulfate (II), sodium sulfate, magnesium sulfate, manganese sulfate, and the like lithium sulfate.
[0042]
Also, when the oxo acid is nitric acid compound, nitric acid, zinc nitrate, ammonium nitrate, potassium nitrate, chromium nitrate (III), cobalt nitrate (II), cesium nitrate, iron nitrate (II), copper nitrate (II), nickel nitrate, barium nitrate, magnesium nitrate, manganese nitrate, such as lithium nitrate and the like.
On the other hand, it is preferably one that is not oxidized and decomposed by the photocatalyst, phosphoric acid, sulfuric acid, carbonic acid, nitric acid, boric acid.
[0043]
As oxo acids, for example when using a phosphoric acid, a phosphate, with a hydrogen phosphate salt, it can be used as an aqueous solution of suitable concentration.
Furthermore, phosphoric acid compounds, such as polyphosphoric acid or metaphosphoric acid it can be used as well.
Both have a plurality of oxo group in its structure.
[0044]
In the present invention, the active oxygen species of the type that occur can selectively be generated by the type and amount of oxo acids and halogen-containing.
For example, when using phosphate as the oxo acid compounds, it has been confirmed that to generate hydrogen peroxide as the active substance.
The content state and the ratio of halogen, may be controlled by the target substance to be generated.
Note that it does not contain an oxo acid, to obtain the same effect by the halogen oxo acid generated from the halogen is not preferable because the generation amount of the halogen oxoacid is small.
[0045]
The "at least a portion of the halogen is chemically bound to the titanium oxide (IV)" in the present invention, it says that at least a portion of the halogen to titanium (IV) oxide are bonded chemically.
Preferably it refers to a state in which the titanium oxide and the halogen rather than carrying and mixing is tied at the atomic level, and, more preferably refers to the titanium oxide and the halogen are ionically bonded.
The term "chemically bonded to are halogen" in the present invention, for example, of the halogen contained in the halogen-containing titanium oxide means a dissolution difficult halogen in water.
In the case of containing two or more of halogen, if a state where more than one of them is bound chemically effect can be obtained.
[0046]
In the present invention, the halogen is chemically bound to the titanium oxide (IV), fluorine, iodine, bromine and chlorine.
For example, halogen, when using the fluorine content of the fluorine, the amount of active substance and in terms of enhanced antimicrobial performance during light irradiation to be 1.25 wt% to 4.0 wt% preferable.
The content of fluorine in the fluorine-containing titanium oxide (IV) can be determined by absorption spectrophotometry (JIS K 0102).
[0047]
The amount of the halogen to the titanium oxide (IV) are chemically bonded to, and dispersing the titanium oxide photocatalyst in water, pH adjusting agents (eg, hydrochloric acid, ammonia water) maintained at pH = 3 or less or pH = 10 Thus, the The amount of elution of halogen into the water is measured by the ratio Iroshizuku Jo-to can be calculated by subtracting the elution amount from the total amount of the halogen in the halogen-containing titanium oxide.
[0048]
Chemical bond is preferably a ionic bond.
If the chemical bond is an ionic bond, a halogen and titanium oxide is firmly bonded, for example, it is possible to improve the promoting effect of the antimicrobial activity and photocatalytic reaction, ionic bonding between the titanium oxide and the halogen is analyzed by photoelectron spectrometer it can.
For example, if the halogen is fluorine, when analyzing the halogen-containing titanium oxide with a photoelectron spectroscopic analyzer, a peak top of fluorine 1s orbital (F1s) is refers to the case shown a spectrum in the range of 683eV~686eV.
This fluorine and the values of the peak top of the titanium fluoride which is ionically bonded to titanium are derived from it is within the above range.
[0049]
[Method of manufacturing a halogen-containing titanium oxide]
Halogen-containing titanium oxide of the present invention, for example, the adsorption amount of n- butylamine were mixed with the aqueous dispersion and the halogen compounds of titanium is less 8μmol / g, furthermore, when the pH of the mixed solution is more than 3 by adjusting the pH to 3 or less using acid, by washing the step of reacting with the halogen compound and the titanium oxide in the mixed solution, the reaction product obtained is allowed to said reaction, halogen- At least a part of it can be produced by a production method including a step of obtaining a halogen-containing titanium oxide are chemically bonded and titanium oxide.
The anatase type titanium oxide adsorbed amount of n- butylamine is less 8μmol / g, for example, can be used such as by Sakai Chemical Industry Co., Ltd. SSP-25, as the aqueous dispersion, for example, Sakai Chemical Industry Co., Ltd. Ltd. CSB-M or the like can be used.
[0050]
The halogen compound is not particularly limited, a typical halogen compounds can be used.
Halogen compounds, in the case of fluorine compounds, such as ammonium fluoride, potassium fluoride, sodium fluoride, hydrofluoric acid. Among these, ammonium fluoride, potassium fluoride, and hydrofluoric acid are preferred .
When the halogen compound is an iodine compound, hydrogen iodide, periodic acid, ammonium iodide, or the like.
When the halogen compound is a bromine compound, hydrobromic acid, ammonium bromide and the like.
When the halogen compound is a chlorine compound, hydrochloric acid, sodium chloride, hypochlorite.
[0051]
Method of measuring the amount of adsorption of n- butylamine per titanium oxide 1g are as follows.
In other words, the sample 1g of titanium oxide were dried 2 hours at 130 ℃, is precisely weighed in stoppered Erlenmeyer flask of 50mL, this is added 30mL of n- butylamine solution of 0.003 specified concentration diluted with methanol.
Then, after this is one hour ultrasonic dispersion, and allowed to stand 10 hours, the supernatant liquid is 10mL collected.
Then, the collected supernatant was titrated potentiometrically with a perchloric acid solution of 0.003 specified concentration diluted with methanol, it is possible to determine the amount of adsorption of the titration n- butylamine in the neutralization point of the time .
[0052]
Further, titanium oxide (IV) is, by bearing on the substrate, radiation and light, shatterproof photocatalyst can be effectively performed.
The substrate is not particularly limited, and can use a common filter substrate, metals, plastics, synthetic resin fibers, natural fibers, wood, paper, glass, and the like ceramics, such as metal or ceramics or glass, Are suitable.
When using a plastic or paper as the base material, a silicone or fluorine resin on the substrate surface, silica or the like is coated may be supported titanium oxide.
[0053]
The shape of the substrate is not particularly limited, plate, net, honeycomb, fiber, bead, slit-like, etc. foam shape, when the filter shape be made contact irradiation and air light efficiently it can.
If the plate-like filter, punching shape drilled in a plate, knitted shape woven fibers, such as a nonwoven fabric shape and bonding the fibers, are preferred those having an opening.
If the plate-like, and may reduce the pressure loss by increasing the surface area of the filter is folded plate-pleated.
[0054]
With glass fiber fabric substrate, resistance to light and radiation is strong, it is preferable less susceptible to chemical attack by organic synthetic fiber and acid binder than paper.
The glass fibers because it has a light transmission and light scattering properties, when it is irradiated with light in the halogen-containing titanium oxide, can be irradiated efficiently light.
The material of the glass fibers, quartz glass, E glass, C glass, S glass, A glass.
Although the fiber shape is not particularly limited, than single fibers, it is preferably formed by a fiber bundle by bundling a plurality of short fibers of glass with a diameter of 4~9μm.
Fiber bundles may be used by bundling any number of the order of this fifty ～6400.
When carrying the titanium oxide in the fiber bundle is a bundle of several short fiberglass and secured titanium oxide particles are crowded or adhered enters between the fibers.
As compared with the case of carrying the titanium oxide on the surface of the thick single fiber, it is possible to hold the titanium oxide between the fibers, it is possible to increase the supported amount.
Also, titanium oxide particles that has entered between the fibers as well are firmly immobilized by caught in the fibers, to obtain the effect of hard to fall off because the impact is transmitted through the fiber even if an impact is applied from the outside it can.
[0055]
If you are using a binder, Na2O, alkali silicate consisting of silicic acid salts such as K2O, LiO2, silica sol, alumina sol, inorganic colloids, such as zirconia sol, silica, silicon, and its hydrolyzate alkoxides such as titanium and the like .
Incidentally, alkali components such as Na lowers the crystallinity of the titanium oxide (IV), since it may degrade performance, as the binder, it is preferable main component is SiO2, silica sol or silica alkoxide such as the kind of hydrolyzate is preferred.
[0056]
The alkoxides of silicon, methoxy polysiloxane is tetraethoxysilane and its polymers, ethoxy polysiloxane, butoxy polysiloxanes, and lithium silicate. Examples of the alkoxides of titanium, tetra propoxy titanium and its polymers such as is it like.
These metal alkoxides can be hydrolyzed by water and an acid, it can be used as a binder.
If the titanium alkoxide, by heating treatment, it can have a photocatalytic activity in itself.
[0057]
The binder is preferably acidic, silicon, etc. the hydrolyzed material and the acidic silica sol with an acid titanium, alumina sol and the like.
Silicon, in the case of hydrolyzing the titanium in acid, hydrochloric acid, it is preferable to adjust the pH to 1-5 by using a sulfuric acid.
When using a silica sol, pH2~4, it is preferably of about the particle size 10~50nm.
When the pH is used a neutral or alkaline silica sol to cause gelation upon the addition of titanium oxide containing a halogen, it is often difficult to be uniformly supported on a substrate.
[0058]
Na, the cationic component, such as K, NH4 is contained in the binder, by adsorption to the progression and titanium (IV) oxide surface of the reaction with the halogen, there is a decrease in the antibacterial performance occurs, it said positive ion component is better as low as possible.
For example, if it contains Na in the binder solution is preferably Na concentration is less more than 0wt% 0.05wt% as Na2O.
[0059]
It is preferably a 10~900g / m2 as the basis weight of the glass fiber fabric, in order to facilitate the manufacture it is preferable to select one of 100~400g / m2.
Also, weaving the fabric, plain weave, twill, satin, leno, etc. Moshao, but may be of any weave, Moshao is preferable from the viewpoint of shape stability.
Fiber bundle of vertical and horizontal as the density of the yarn is 20 to 40 present / 25mm, thickness is 0.1~2mm, more tensile strength of 100N / 25mm are preferred.
[0060]
As a method for carrying the halogen-containing titanium oxide to the substrate, a dip coating, a spray and the like, halogen-containing titanium oxide can be any means as long immobilized on a substrate.
If the supported amount is sufficient in one process may be repeated a plurality of processing steps.
Furthermore, after carrying, dryer may be firmly immobilized on the substrate and thereby shrink the binder by heating about 0.01-5 hours at a temperature of about 50~700 ℃, at 90~150 ℃ 0. 1 hour of heating is more preferable.
When performing such a heat drying treatment, it is preferable to constitute the principal component of the base glass, ceramics.
[0061]
The particle diameter of the halogen-containing titanium oxide, the smaller than the diameter of the fibers are preferred.
Since the halogen-containing titanium oxide is less than the diameter of the fibers, the halogen-containing titanium oxide is easily enter the stitches and the overlapping portion between the fibers, it is possible to obtain an effect of being firmly fixed.
As a result, it is possible to increase the supported amount of the halogen-containing titanium oxide.
The particle diameter of the halogen-containing titanium oxide, but in fact often is in the secondary particles of about 0.1~100μm primary particles by aggregation of about 6~100nm as primary particle size.
The particle diameter of the halogen-containing titanium oxide referred to herein indicates a state of the secondary particles, it is necessary that a halogen-containing titanium oxide is easily enters the stitches and the overlapping portions of the fibers when dispersed in knitting.
[0062]
To halogen-containing titanium oxide was prepared, followed by impregnating the oxo acids.
Oxo acid, is used for impregnation by mixing a soluble concentration in an appropriate solvent.
For example, it is used, for example purified water and dissolved to a concentration of about 10 wt% 0.01 wt%.
In addition, the solution was mixed with different kinds of halogen compounds and halogen is chemically bonded, and can be simultaneously affixed.
Halogen in this case, for example, in a chlorine compound, sodium chloride, potassium chloride, and a chloride such as magnesium chloride.
In addition, in the iodine compounds, and the like, such as potassium iodide.
In the bromine compound, potassium bromide, calcium bromide, ammonium bromide, and a bromide such as sodium bromide.
These also are mixed the amount that can be dissolved in a solution of an oxo acid, it is used by dissolving.
For example, it can be dissolved to a concentration of about 10 wt% 0.01 wt%, are used.
[0063]
As a method for impregnating the oxo acid in the photocatalyst 1, dip coating, a spray and the like, and may be any means as long adhered to the photocatalyst 1.
After a photocatalyst 1 was brought into contact with the oxo acid solution, if the powder centrifugation or filtration, and, if a state of being immobilized on a substrate, after pulling, the residual liquid was dried at a low temperature of 100 ℃ me eliminated.
In this way, it affixed to the oxo acids and halogen In, instead of a chemical bond with titanium oxide, and the pores of the titanium oxide, it is presumed to be in a state where it is adsorbed at random on the surface.
[0064]
In this way it is manufactured, the oxo acids and halogen-containing titanium oxide immobilized on the substrate is irradiated with ultraviolet rays using an ultraviolet light source, it is possible to generate active oxygen species in the liquid by a photocatalytic reaction, when The purpose may be to reach the year.
[0065]
Hereinafter, the detailed description of the present invention in embodiments, the present invention is not intended to be construed in any way limited to the following description.
[0066]
(Example 1)
Preparation of halogen-containing titanium oxide
Titanium oxide (trade name: SSP-25, manufactured by Sakai Chemical Industry Co., Ltd., anatase type, particle size: 5~10nm, specific surface area: 270m2 / g or more) pure titanium oxide such that the concentration of the 150g / L It was added and stirred it to prepare a titanium oxide dispersion.
The titanium oxide dispersion liquid, hydrofluoric acid (manufactured by Wako Pure Chemical Industries, Ltd., special grade) corresponding to 3% by weight in terms of fluorine (element) with respect to the titanium oxide was added, and 25 ℃ while maintaining to pH3 in it was allowed to react for 60 minutes.
The resulting reaction was it was washed with water.
Washing with water, the electric conductivity of the filtrate is recovered by reaction with filtration was carried out until the following 1mS / cm.
Then, this was prepared fluorine-containing titanium oxide was dried 5 hours at 130 ℃ in air.
[0067]
<2>.Preparation of the filter carrying the halogen-containing titanium oxide
The resulting halogen-containing titanium oxide and silica binder (Na component 0.05wt% or less as Na2O concentration, pH = 3, SiO2 concentration 20wt% silica sol) were mixed with purified water for 24 hours and dispersed and mixed by a ball mill We have created a slurry Te.
to the resulting slurry was dipped the aperture ratio of 15% glass fiber fabric as a base material impregnated with a halogen-containing titanium oxide, after eliminating the excess solution by air blow, and dried 30 minutes at the 120 ℃ dryer, halogen We have created a filter that includes the content of titanium oxide.
And repeating the same dipping operation, the supporting amount of the combined halogen-containing titanium oxide and a binder were to 500g / m2.
Glass fiber fabric that becomes the base material of the filter, Moshao of basis weight of 354g / m2, yarn density 11 × 3 present / 25mm (vertically and horizontally same), the thickness was used of 0.42mm.
The aperture ratio of the filter that was created was about 15%.
[0068]
<3>.Production of oxo acid and a halogen-containing titanium oxide filter
The resulting halogen-containing titanium oxide filter, and after impregnated with 50mM phosphate buffered saline is a source of oxo acids and halogens, and pulled up and dried by standing for 2 hours in a drying oven at 50 ℃, oxo It was with an acid and a halogen-containing titanium oxide filter.
[0069]
<4>.Measurement of the amount of the production of the hydrogen peroxide
The photocatalytic filter thus prepared, length 5cm, was cut into a strip having a width 2cm, it was inserted into a glass test tube having a diameter of 3cm depth 10cm.
At 3mm diameter Teflon in vitro in order to air the air in distilled water (R) Chupu is provided an air pipe.
The tip of the pipe was installed diffuser tubes of the ceramic porous body to be able to emit fine bubbles.
Note that the tip of the pipe was arranged to be under the photocatalytic filter.
The air in the diaphragm pump from the piping in this state it was air in the liquid at a flow rate of 0.1ml / min.
[0070]
On the outside of the test tube and was irradiated with black light to be 5mW / cm2 so as to sandwich the tube and allowed to flow for 12 hours air to collect the hydrogen peroxide generated in the liquid from the filter.
After 12 hours, the recovered reaction liquid in the test tube, followed by quantification of hydrogen peroxide in the liquid.
Measurement of hydrogen peroxide, hydrogen peroxide quantified for a chromogenic substrate (trade name: H2O2 DetectionKit Colorimetric, manufactured AssayDesigns Ltd.) was used, to measure the color of 582nm in the ultraviolet-visible absorption spectrometer.
As a result it is shown in Figure 2.
[0071]
(Comparative Example 1)
As Comparative Example 1, in place of the halogen-containing titanium oxide, anatase type titanium oxide having a photocatalytic activity and free of halogen (trade name: SSP-25, manufactured by Sakai Chemical Industry Co., Ltd.) except that created the filter by using the , it was measured for the generation amount of active substance in the same manner as in Example 1.
As a result it is shown in Figure 2.
[0072]
(Comparative Example 2)
As Comparative Example 2, in place of the halogen-oxo-acid-containing titanium oxide, except for using a filter using a halogen-containing titanium oxide which does not contain an oxo acid, a measurement of the amount of generated hydrogen peroxide in the same manner as in Example 1 went.
As a result it is shown in Figure 2.
[0073]
(Comparative Example 3)
As Comparative Example 3, in the same manner as in Example 1, it was measured for the generation amount of hydrogen peroxide in the dark without UV irradiation.
As a result it is shown in Figure 2.
[0074]
As shown in Figure 2, the filter of Example 1, the hydrogen peroxide of about 153nmol / m3 were detected after 24 hours.
On the other hand, the filter of Comparative Example 1, 0.14nmol / m3, filter of Comparative Example 2 (less than 0.1nmol / m3) lower detection limit or less, filter of Comparative Example 3, the detection limit or less (less than 0.1nmol / m3) met.
And it contains the oxo acids, by light irradiation, that hydrogen peroxide is the active agent is released from the filter was observed.
Further, by using a halogen-containing titanium oxide, a generation amount was confirmed to be increased to more than 1000 times.
[0075]
The photocatalytic reaction photocatalyst in a liquid it is possible to provide a method of generating active oxygen species in water, it can be applied to applications such as decontamination of sterilization and drainage of the water distribution equipment.
[0076]
1 photocatalyst
2 light source
3 air diffuser means
4 pure water generating means
101 ultra-pure water production system
102 ozone gas generator
103 ozone gas dissolution apparatus
104 basic chemical addition device
105 point-of-use
106 pH meter
107 dissolved ozone monitor
108 ultra-pure water supply pipe
109 storage tank
US8367050
PHOTOCATALYTIC MATERIAL AND PHOTOCATALYTIC MEMBER AND PURIFICATION DEVICE USING THE PHOTOCATALYTIC MATERIAL
PHOTOCATALYTIC MATERIAL AND PHOTOCATALYTIC MEMBER AND PURIFICATION DEVICE USING THE PHOTOCATALYTIC MATERIAL
Inventor(s): TANIGUCHI NOBORU, et al
Applicant(s): PANASONIC CORP
Provided are a photocatalytic material that improves a decomposition performance and a decomposition rate, as well as a photocatalytic member and a purification device in which the photocatalytic material is used. The photocatalytic member is a photocatalytic member (1) that includes a substrate (10) and a photocatalyst layer (11) formed on a surface of the substrate (10), wherein the photocatalyst layer (11) contains a titanium oxide photocatalyst and zeolite, the titanium oxide photocatalyst containing at least an anatase-type titanium oxide and fluorine, in which a content of the fluorine in the titanium oxide photocatalyst is 2.5 wt % to 3.5 wt %, and 90 wt % or more of the fluorine is chemically bonded to the anatase-type titanium oxide.
TECHNICAL FIELD
[0001] The present invention relates to a photocatalytic material containing titanium oxide, as well as a photocatalytic member and a purification device using the photocatalytic material.
BACKGROUND ART
[0002] Recently, titanium oxide photocatalysts have been put into practical use in various situations, for the purposes of sterilization, antifouling, and the like. The use of the same now is not limited to outdoor use, but is spreading to indoor use for the purposes of sterilization, deodorization, and the like. Because of this, a titanium oxide has been demanded that can be excited efficiently even by an energy in a visible region in a titanium oxide excitation system that conventionally has required an energy in an ultraviolet region. Such demand often is met by a titanium oxide supporting a foreign element or forming a solid solution with a foreign element. A wavelength for exciting the titanium oxide can be controlled depending on the type of a foreign element to be added.
[0003] However, in many cases, such a treatment that causes titanium oxide to support a foreign element or causes titanium oxide to form a solid solution with a foreign element significantly reduces an efficiency of excitation inherent to the titanium oxide. In return for the excitability with respect to visible light, an effect to be achieved originally by ultraviolet rays is reduced, which results in a decrease in activity in many cases.
[0004] Conventionally, it is known that the photocatalytic activity of titanium oxide is enhanced by elimination of lattice defects in titanium oxide using a mineral acid or the like (Non-Patent Document 1). Especially, it is known that a hydroxyl group on a surface of titanium oxide can be replaced easily with fluorine. Therefore, there have been proposals to treat titanium oxide with a fluorine compound such as hydrofluoric acid so as to enhance the photocatalytic performance in the titanium oxide excitation system using ultraviolet rays (Non-Patent Document 2, Patent Documents 1 and 2). However, some types of titanium oxide treated as above did not fully exhibit the effect.
[0005] On the other hand, regarding deodorization and purification of air, a technology that is capable of promptly deodorizing and decomposing four major odorous components—acetaldehyde, acetic acid, ammonia and sulfur compound gas (e.g. hydrogen sulfide and methyl mercaptan)—has been demanded. Exemplary methods of the above technology are as follows: a method of concentrating and storing odor using an adsorbent such as activated carbon or zeolite; and a method of directly decomposing odor by thermal decomposition, thermal catalytic decomposition, ozone decomposition, plasma discharge decomposition, photocatalyst decomposition, or the like.
[Patent Document 1] JP 07-303835 A
[Patent Document 2] JP 2004-292225 A
[Non-Patent Document 1] Proceedings Electrochemical Society 1988, vol. 88, no. 14, pp. 23-33
[Non-Patent Document 2] The Journal of Physical Chemistry, 1990, vol. 94, pp. 4276-4280
DISCLOSURE OF INVENTION
Problem to be Solved by the Invention
[0006] However, the method using an adsorbent only provides poor adsorbability with respect to acetaldehyde, which is highly contained in mainstream smoke and secondary smoke of tobacco products, and therefore has a problem that odor once adsorbed is again released. Moreover, the direct decomposition method using thermal decomposition or catalytic decomposition has problems in heat generation and power consumption; ozone decomposition and plasma discharge decomposition have a problem in safety because of ozone generation; and photocatalyst decomposition has a problem in the decomposition rate. Especially, in photocatalyst decomposition, as compared with the other methods, a superior ability of eliminating acetaldehyde is exhibited owing to the gas adsorbability originally possessed by titanium oxide used as a photocatalyst material, but the decomposition rate is insufficient for practical use.
[0007] Therefore, the present invention provides a photocatalytic material containing titanium oxide that is capable of improving a decomposition performance and a decomposition rate, as well as a photocatalytic member and a purification device using the photocatalytic material.
Means for Solving Problem
[0008] A photocatalytic material of the present invention includes a titanium oxide photocatalyst and zeolite, the titanium oxide photocatalyst containing at least an anatase-type titanium oxide and fluorine,
[0009] wherein a content of the fluorine in the titanium oxide photocatalyst is 2.5 wt % to 3.5 wt %, and
[0010] 90 wt % or more of the fluorine is chemically bonded to the anatase-type titanium oxide.
[0011] A photocatalytic member of the present invention is a photocatalytic member comprising a substrate, and a photocatalyst layer formed on a surface of the substrate,
[0012] wherein the photocatalyst layer contains the above-described photocatalytic material of the present invention.
[0013] A purification device of the present invention comprises the above-described photocatalytic member of the present invention, and a light source that irradiates the photocatalytic member with light having a wavelength of 400 nm or less.
EFFECTS OF THE INVENTION
[0014] The photocatalytic material, the photocatalytic member, and the purification device of the present invention include a titanium oxide photocatalyst having high photocatalytic activity and zeolite. Therefore, it is possible to improve, for example, an odorous component decomposition performance, and an odorous component decomposition rate.
BRIEF DESCRIPTION OF DRAWINGS
[0015] FIG. 1 is a cross-sectional view of a photocatalytic member according to Embodiment 1 of the present invention.
[0016] FIGS. 2A and 2B are perspective views of typical gas-permeation filters of the present invention.
[0017] FIG. 3 is a perspective view of a photocatalytic member according to Embodiment 2 of the present invention.
[0018] FIG. 4 is a perspective view of a purification device according to Embodiment 3 of the present invention.
[0019] FIG. 5 is a perspective view of a purification device according to Embodiment 4 of the present invention.
[0020] FIG. 6A is a perspective view of an air purification device according to Embodiment 5 of the present invention, and FIG. 6B is a cross-sectional view of the device shown in FIG. 6A, taken along a line I-I.
[0021] FIG. 7 is a cross-sectional view of an air purification device according to Embodiment 6 of the present invention.
[0022] FIG. 8 is a cross-sectional view of an air purification device according to Embodiment 7 of the present invention.
[0023] FIG. 9 is a cross-sectional view of a liquid purification device according to Embodiment 8 of the present invention.
[0024] FIG. 10 is a perspective view of a liquid purification device used in the evaluation of photocatalytic activity.
[0025] FIG. 11 is a graph showing the relationship between the UV irradiation time and the concentration of methylene blue in each of Reference Examples 1 and 2 and Comparative Examples 1 and 7.
EXPLANATION OF REFERENCE CODES
[0000]
1, 21, 31, 41, 51, 61, 71, 101 photocatalytic member
2 co-flow air purification device
201 cross-flow air purification device
3 to 5 air purification device
6, 8 liquid purification device
10, 20, 21a, 31a, 41a, 51a, 61a substrate
11, 21b, 31b, 4113, 51b, 61b, 71b photocatalyst layer
20, 25, 30, 40, 50, 60, 70 container
22, 32 light source
23, 52 blowing means
25a parting plate
33 reflection plate
42 oil mist
52 blowing means
53 prefilter
62a liquid-feeding valve
62b liquid-discharging valve
63 contaminated water
71a glass substrate
72 black light
80 Petri dish
81 stand
DESCRIPTION OF PREFERRED EMBODIMENTS
[0048] A photocatalytic material of the present invention is a photocatalytic material containing a titanium oxide photocatalyst and zeolite, the titanium oxide photocatalyst containing at least an anatase-type titanium oxide (hereinafter also referred to as “titanium oxide” simply) and fluorine, wherein a content of the fluorine in the titanium oxide photocatalyst is 2.5 wt % to 3.5 wt %, and 90 wt % or more of the fluorine is chemically bonded to the above anatase-type titanium oxide. With the photocatalytic material of the present invention, the performance of decomposing organic molecules (e.g. odorous components) can be improved, with an adsorbing function of zeolite. Further, since it contains the titanium oxide photocatalyst, the photocatalytic activity can be improved. Therefore, an odorous component decomposition rate, for example, can be improved.
[0049] In the photocatalytic material of the present invention, for example, from the viewpoint of maintaining the photocatalytic activity and the deodorizing power, zeolite mentioned above preferably contains at least one of a mordenite-form zeolite and a ZSM-5-form zeolite.
[0050] In the photocatalytic material of the present invention, for example, from the viewpoint of maintaining the photocatalytic activity and the deodorizing power, zeolite mentioned above preferably contains silica and alumina, and a molar component ratio between silica and alumina (silica/alumina) in the zeolite preferably is 240 or more.
[0051] In the present invention, a photocatalyst refers to a substance that shows catalytic activity when irradiated with light such as ultraviolet rays, and preferably, to a substance that, when irradiated with light, can decompose and eliminate various organic and inorganic compounds and perform sterilization. The titanium oxide photocatalyst of the present invention preferably can be used for, for example, decomposing and eliminating odorous components such as acetaldehyde and methyl mercaptans; sterilizing and eliminating fungi and algae; oxidatively decomposing and eliminating nitrogen oxides; and imparting an anti-fouling function by causing glass to have ultra-hydrophilic properties.
[0052] In the present invention, examples tithe photocatalytic activity include a function of decomposing organic compounds oxidatively when the titanium oxide photocatalyst is irradiated with ultraviolet rays. The photocatalytic activity of the present invention can be evaluated by, for example, a carbon dioxide generation rate that indicate a rate at which carbon dioxide is generated along with the oxidation of organic compounds when the organic compounds in a gaseous or liquid state and the titanium oxide photocatalyst coexist and are irradiated with ultraviolet rays of 400 nm or less. Preferably, the photocatalytic activity can be evaluated by, for example, a carbon dioxide generation rate at which carbon dioxide is generated by the oxidative decomposition of acetaldehyde. The reaction is expressed by a reaction formula (I) shown below
[0000]
CH3CHO+0.5O2→CH3COOH+2O2→2CO2+2H2O Reaction formula (1)
[0053] The titanium oxide photocatalyst used in the present invention contains fluorine in the range of 2.5 wt % to 3.5 wt % in element content; more preferably, in the range of 2.7 wt % to 3.3 wt %; and further preferably, in the range of 2.9 wt % to 3.1 wt %. Setting the content of fluorine to 2.5 wt % or more makes it possible to improve the photocatalytic activity while setting the content of fluorine to 3.5 wt % or less makes it possible to suppress a decline in the photocatalytic activity.
[0054] The reason why the above-titanium oxide photocatalyst improves the photocatalytic activity is uncertain, but it is assumed as follows: by the setting of the content of fluorine at 2.5 wt % or more, the fluorine, which has a large electronegativity, comes to stay on a surface of the titanium oxide. Owing to the electron-withdrawing function of the fluorine located on the surface of the titanium oxide, for example, a hydroxyl group located adjacent thereto is activated, whereby a hydroxyl radical tends to be generated. As a result, the photocatalytic reaction can be accelerated. Although the photocatalytic reaction can develop even when the content of fluorine is 2.5 wt % or less, the effect of accelerating the photocatalytic reaction can be enhanced greatly when the content of fluorine is 2.5 wt % or more.
[0055] Further, the reason why the above-titanium oxide photocatalyst can suppress a decline in the photocatalytic activity is uncertain, but it is assumed as follows: by setting the content of fluorine at 3.5 wt % or less, for example, the amount of fluorine covering the surface of the titanium oxide can be kept in an adequate range, whereby the number of hydroxyl groups required for the photocatalytic reaction can be ensured.
[0056] Furthermore, in the titanium oxide photocatalyst used in the present invention, 90 wt % or more of fluorine is chemically bonded to the titanium oxide. This allows the fluorine to exhibit its own electron-withdrawing function effectively, whereby the photocatalytic reaction accelerating effect can be enhanced. Specifically, the above chemical bond preferably is anionic bond because in such a case fluorine and titanium oxide are bonded to each other firmly and the photocatalytic reaction accelerating effect is enhanced further. It should be noted that the ionic bond of fluorine and titanium oxide can be determined in a measurement using a photoelectron spectroscopic analyzer, which is described later.
[0057] In the above-described titanium oxide photocatalyst, from the viewpoint of accelerating the photocatalytic reaction, a proportion of fluorine chemically bonded to the titanium oxide is 90 wt % or more of the entirety of the fluorine in the titanium oxide photocatalyst preferably 95 wt % or more; and more preferably 100 wt %, that is, the entirety of the fluorine contained in the titanium oxide photocatalyst is chemically bonded to the titanium oxide. In the titanium oxide photocatalyst of the present invention, the content of fluorine chemically bonded to titanium oxide is, for example, 2.35 wt % to 3.5 wt %; preferably 2.5 wt % to 3.5 wt %; and more preferably 2.5 wt % to 3.3 wt %.
[0058] In the present invention, a chemical bond between titanium oxide and fluorine refers to a state in which titanium oxide and fluorine are chemically bonded to each other, and preferably, to a state in which titanium oxide and fluorine are, not supported or mixed, but bonded to each other at the atomic level. In the present invention, chemically-bonded fluorine refers to, tithe fluorine contained in the titanium oxide photocatalyst, the fluorine that is not eluted into water, for example. The amount of such fluorine chemically bonded to the titanium oxide can be measured by the following method: first, a titanium oxide photocatalyst is dispersed into water; then the dispersion solution is kept at pH=3 or less, or pH=10 or more with a pH adjuster (e.g. hydrochloric add, ammonia water); the amount of fluorine ion eluted into water is measured by a colorimetric titration, or the like; and the above eluted amount is subtracted from the total amount of the fluorine contained in the titanium oxide photocatalyst. Thus, the amount of the fluorine chemically bonded to the titanium oxide can be determined. The amount of fluorine ion eluted into water can be measured as in Examples described later.
[0059] In the above-described titanium oxide photocatalyst, it is preferable that at least a part of the fluorine chemically bonded to the titanium oxide is located on surfaces of titanium oxide. Because the photocatalytic reaction mainly occurs on surfaces of titanium oxide, if the fluorine is located on surfaces of titanium oxide, the photocatalytic reaction accelerating effect is enhanced further. It should be noted that the amount of fluorine chemically bonded to the titanium oxide on surfaces of the titanium oxide can be determined in a measurement using a photoelectron spectroscopic analyzer, as in Examples described later.
[0060] In the present specification, “titanium oxide and fluorine are bonded ionically” refers to a case in which, when the titanium oxide photocatalyst is analyzed by a photoelectron spectroscopic analyzer, the catalyst shows a spectrum such that a peak-top of 1s orbital of fluorine (F1s) appears in a range from 683 eV to 686 eV. This is ascribed to titanium fluoride, which results from ionic bonding of fluorine and titanium, having a peak-top value falling in the above range.
[0061] In the case where the above-described titanium oxide photocatalyst includes sodium, and where a content of sodium in the entirety of the titanium oxide photocatalyst is assumed to be A wt % and a content of fluorine in the entirety of the titanium oxide photocatalyst is assumed to be B wt %, a ratio A/B is preferably 0.01 or less; more preferably 0.005 or less; and further preferably 0.001 or less. If the ratio A/B is 0.01 or less, a decline in the photocatalytic activity can be suppressed. The reason is uncertain, yet it is assumed that, for example, a decrease in the amount of sodium with respect to fluorine causes the decline in the photocatalytic activity due to the reaction between sodium and fluorine to be suppressed. It should be noted that it is most preferable that the content of sodium is 0, that is, it is most preferable that the ratio A/B is 0. Regarding impurities other than sodium also, it is preferable that there are less impurities; and it is most preferable that there are no impurities. Examples of an element that can be impurities include potassium, aluminum, and transition metals.
[0062] Regarding the titanium oxide photocatalyst used in the present invention, a specific surface area thereof is preferably in a range of 200 m<2>/g to 350 m<2>/g; and more preferably, in a range of 250 m<2>/g to 350 m<2>/g. Here, in the present invention, the specific surface area refers to a value of a surface area per 1 g of the titanium oxide photocatalyst in powder form measured by a BET method (nitrogen adsorption-desorption method). When the specific surface area is 200 m<2>/g or more, the area in contact with an object to be decomposed can be large. Further, in the case where an anatase-type titanium oxide is used, and if the specific surface area thereof is 350 m<2>/g or less, a photocatalytic reaction with higher efficiency can be achieved compared to the case where an amorphous titanium oxide is used. Here, the anatase-type titanium oxide refers to a titanium oxide showing a diffraction peak at a diffraction angle 2θ=25.5 degrees in a measurement with a powder X-ray diffractometer using copper electrodes as working electrodes.
[0063] The titanium oxide photocatalyst used in the present invention can be produced through, for example, the following producing method. First, a pH of an aqueous dispersion solution of titanium oxide is adjusted with an alkaline solution until the pH thereof becomes in a range of 7.5 to 9.5, and thereafter the solution is filtered. Subsequently, the filtration residue obtained by the filtration is re-dispersed into water. Then, a fluorine compound is added to the re-dispersion solution obtained by the re-dispersion so that a suspension is obtained, and thereafter, a pH of the suspension is adjusted with an acid until the pH thereof becomes 3 or less, whereby the titanium oxide and the fluorine compound are caused to react with each other. Then, the reaction product obtained by the reaction is washed. With the present method, the above-described titanium oxide photocatalyst can be produced easily. In this method, if the amount of added fluorine compound is increased, the titanium oxide dissolves itself. Therefore, the content of fluorine in the titanium oxide photocatalyst can be controlled easily to 3.5 wt % or lower. Further, in the case where the reaction product is washed with water, the water washing preferably is carried out until an electric conductivity of water used in the washing becomes 1 mS/cm or less, as an index for washing. The water used for washing in the present invention refers to, for example, water that is used for washing a reaction product and thereafter is collected. The electric conductivity can be measured in a manner as in Examples to be described later.
[0064] In the present method, the aforementioned re-dispersion solution contains an anatase-type titanium oxide having such a surface acidity that an amount of adsorbed n-butylamine per 1 gram of the titanium oxide is, for example, 8 μmol or less. Thus, using as a starting material the anatase-type titanium oxide having a surface that is almost basic, a titanium oxide photocatalyst can be prepared that contains fluorine in a range of 2.5 wt % to 3.5 wt % as an element. Therefore, in the foregoing producing method, the steps of “adjusting a pH of an aqueous dispersion solution of a titanium oxide with an alkaline solution until the pH thereof becomes in a range of 7.5 to 9.5, and thereafter filtering the solution” and “re-dispersing the filtration residue obtained by the filtration into water” may not be used, but instead, an aqueous dispersion solution of an anatase-type titanium oxide that adsorbs n-butylamine in an amount of 8 μmol/g or less may be used.
[0065] Therefore, the titanium oxide photocatalyst containing fluorine can be produced through the following steps: mixing a fluorine compound and an aqueous dispersion solution of an anatase-type titanium oxide that adsorbs n-butylamine in an amount of 8 μmol/g or less whereby a mixed solution containing titanium oxide and fluorine and having a pH of 3 or less is prepared, so that the titanium oxide and the fluorine compound are caused to react with each other; and washing the reaction product obtained.
[0066] As the anatase-type titanium oxide that adsorbs n-butylamine in an amount of 8 μmol/g or less, for example, SSP-25 manufactured by SAKAI Chemical Industry Co., Ltd. can be used. As the aqueous dispersion solution of the same, for example, CSB-M manufactured by SAKAI Chemical Industry Co., Ltd. can be used.
[0067] Here, the method for measuring the amount of adsorbed n-butylamine per 1 grain of titanium oxide is as follows. One gram of a titanium oxide sample dried at 130° C. for 2 hours is weighed in a 50-mL stoppered Erlenmeyer flask, and 30 mL of a n-butylamine solution diluted with methanol to have a normality of 0.003 N is added to the foregoing titanium oxide sample. Then, this is subjected to ultrasonic dispersion for 1 hour, and is left to stand for 10 hours. 10 mL of the supernatant fluid of the same is sampled. The sampled supernatant fluid is subjected to potentiometric titration using a perchloric acid solution diluted with methanol to have a normality of 0.003 N, and from the titrated amount of at the point of neutralization, the amount of adsorbed n-butylamine can be determined.
[0068] In the present method, the anatase-type titanium oxide having such a surface acidity that an amount of adsorbed n-butylamine per 1 gram of titanium oxide is 8 μmol or less preferably contains sodium as impurities in an amount of 1000 ppm by weight (wt ppm) or less. If the content of sodium as impurities is 1000 wt ppm or less, the deterioration of photocatalytic activity can be suppressed. The reason for this is uncertain, but it is assumed that, for example, sodium reacts with fluorine, whereby the inhibition of the reaction between fluorine and titanium oxide can be prevented.
[0069] Further, as an alkaline solution used at the stage of preparation of the starting material, and as additives to be added as required after the reaction with fluorine, those which substantially do not contain sodium are desirable. Examples of the alkaline solution include ammonia water, an aqueous ammonium carbonate solution, and an aqueous hydrazine solution.
[0070] In the present method, in the step of re-dispersing the filtration residue obtained by the filtration into water, the filtration residue preferably is in a state of not being dried when being re-dispersed into water. This is because the dispersibility of the filtration residue in the re-dispersion solution can be improved.
[0071] In the present invention, a specific method for obtaining the re-dispersion solution is not limited particularly. The re-dispersion solution may be prepared by, for example, any one of the methods shown below, or may be prepared by, for example, dispersing a powder-form titanium oxide available from the market (e.g., SSP-25 manufactured by SAKAI Chemical Industry Co., Ltd.) into pure water.
[0072] Method 1
[0073] An aqueous titanyl sulfate solution is heated to a temperature in a range of 80° C. to 100° C. so as to be hydrolyzed, and a slurry aqueous solution of white precipitate thus obtained is cooled. The pH of the obtained white precipitate slurry (aqueous dispersion solution of titanium oxide) is adjusted with ammonia water added to the slurry, until the pH becomes in a range of 7.5 to 9.5. Then, the slurry is filtered. The filtration residue thus obtained is washed with water thoroughly so that salts as impurities are removed. A cake made of this filtration residue thus obtained is re-dispersed in pure water, whereby a re-dispersion solution of an anatase-type titanium oxide can be obtained.
[0074] Method 2
[0075] After ammonia water is added to an aqueous titanyl sulfate solution, a pH of the obtained aqueous dispersion solution of titanium oxide is adjusted with ammonia water added to the dispersion solution until the pH becomes in a range of 7.5 to 9.5. Then, the slum is filtered. The filtration residue thus obtained is washed with water thoroughly so that salts as impurities are removed. A cake made of this filtration residue thus obtained is heated at 100° C., aged, and re-dispersed in pure water, whereby a re-dispersion solution of an anatase-type titanium oxide can be obtained.
[0076] Method 3
[0077] An aqueous titanium tetrachloride solution is heated so as to be hydrolyzed, and the pH of the obtained white precipitate slurry (aqueous dispersion solution of titanium oxide) is adjusted with ammonia water added to the slurry until the pH becomes in a range of 7.5 to 9.5. Then, the slurry is filtered The filtration residue thus obtained is washed with water thoroughly so that salts as impurities are removed. A cake made of this filtration residue thus obtained is heated to a temperature in a range of 80° C. to 100° C., aged, and re-dispersed in pure water, whereby a re-dispersion solution of an anatase-type titanium oxide can be obtained.
[0078] Method 4
[0079] Titanium tetraalkoxide is hydrolyzed in a solvent, and a pH of a suspension of the precipitate obtained (aqueous dispersion solution of titanium oxide) is adjusted by adding ammonia water to the suspension, until the pH becomes in a range of 7.5 to 93. Then, the suspension is filtered. The filtration residue thus obtained is washed with water thoroughly so that salts as impurities are removed. A cake made of this filtration residue thus obtained is heated to a temperature in a range of 80° C. to 100° C., aged, and re-dispersed in pure water whereby a re-dispersion solution of an anatase-type titanium oxide can be obtained.
[0080] The crystallinity of the anatase-type titanium oxide in the re-dispersion solution thus obtained preferably is such that a diffraction peak appears at a diffraction angle 2θ=25.5°, when it is measured by drying the re-dispersion solution at 50° C. under a reduced pressure so that dry powder is obtained, and measuring the crystallinity of the powder with a powder X-ray diffractometer using copper electrodes as working electrodes. This is because titanium oxide having such a characteristic is a crystallized anatase titanium oxide, and if this is used as a starting material, the photocatalytic activity can be improved.
[0081] In the present method, the fluorine compound to be added to the re-dispersion solution is not particularly limited, but examples of the same include ammonium fluoride, potassium fluoride, sodium fluoride, and hydrofluoric acid. Among these, ammonium fluoride, potassium fluoride, and hydrofluoric acid are preferred. When a fluorine compound is added to a re-dispersion solution, it is necessary to add a fluorine compound at least so that an amount of fluorine as an element becomes 2.5 wt % or more with respect to the titanium oxide photocatalyst obtained.
[0082] Examples of the method for adding the fluorine compound include a method of adding the above-described fluorine compound in a solid state to the re-dispersion solution, a method of adding an aqueous solution of the above-described fluorine compound to the re-dispersion solution, and a method of bubbling fluorine gas or hydrofluoric acid gas in the re-dispersion solution. Among these, from the viewpoint of cost efficiency and handleability, the method of adding the solid fluorine compound to the re-dispersion solution, and the method of adding an aqueous solution of the fluorine compound to the re-dispersion solution are preferable. Further, from the viewpoint of the efficiency of reaction between titanium oxide and fluorine, it is preferable that the re-dispersion solution obtained and the fluorine compound are mixed, without a hydrothermal treatment being carried out under such conditions that a specific surface area would not decrease. The time for the treatment for the fluorine compound is not limited particularly, but is preferably in a range of 5 minutes to 90 minutes. The time more preferably is in a range of 30 minutes to 60 minutes. In the case where the time is set at 5 minutes or more, the fluorine compound added is dispersed sufficiently. In the case where the time is set at 90 minutes or less, titanium oxide having high activity can be obtained. Further, the temperature for the treatment of the fluorine compound preferably is 40° C. or lower. In the case where the temperature is set at 40° C. or lower, a decrease in the specific surface area of titanium oxide can be prevented. The temperature for the treatment of a fluorine compound normally is 10° C. or higher.
[0083] In the present invention, examples of acid used for the adjustment of a pH include hydrochloric acid, nitric acid, sulfuric acid, and hydrofluoric acid. An upper limit of the pH of a suspension obtained by adding a fluorine compound to a re-dispersion solution of titanium oxide and a mixed solution containing the anatase-type titanium oxide and a fluorine compound is 3 or less. A lower limit of the pH of the suspension and the mixed solution is not limited particularly, but from the viewpoint of cost efficiency and handleability, the pH preferably is 1 or more.
[0084] In the present invention, a reaction product obtained through the reaction step is washed with, for example, water. This makes it possible to remove fluorine that has not reacted with titanium oxide in the reaction step, unnecessary salts, dissolved impurities, and the like. Therefore, the photocatalytic activity can be improved.
[0085] In the case where the washing is carried out with water (water washing), the washing preferably is carried out until an electric conductivity of water used in the washing becomes 1 mS/cm or less, as an index for washing. In the case where the washing is carried out until an electric conductivity of water used in the washing becomes 1 mS/cm or less, unnecessary salts, dissolved impurities, etc. can be removed adequately. Here, immediately after the treatment with a fluorine compound, the washing preferably is carried out with the treatment liquid with the same liquid composition, without the pH thereof being adjusted. This is because the washing with the treatment liquid with the same liquid composition makes it possible to remove impurities dissolved in the liquid easily, and hence, improves the photocatalytic activity. It should be noted that as the washing method, a method using a centrifuge, filtration equipment of any one of various types, a rotary washing machine or the like can be used, for example.
[0086] In the present method, the titanium oxide photocatalyst obtained as described above may be subjected to a finishing treatment as required, depending on the use of the photocatalyst. For example, in the case where the photocatalyst is finished into a powder form through a drying step, it may be subjected to any conventionally known treatment for avoiding the aggregation caused by the drying, and any means for loosening aggregated powder may be used. In order to loosen powder aggregated due to the drying, any common grinder may be used, but the grinding has to be carried out under such conditions that the photocatalytic activity would not deteriorate. For example, in order to prevent titanium oxide crystals from being destroyed, the grinding power has to be decreased.
[0087] Further, the titanium oxide photocatalyst having been washed through the above-described washing step may be dispersed in a solvent again so as to be used as an aqueous, oily, or emulsified dispersion solution. Here, a wet-type grinder may be used in order to loosen caking, but a type of equipment and conditions that would not deteriorate the photocatalytic activity have to be chosen, as described above. For example, in the case of a dispersing device using a grinding medium, the concentration of titanium oxide preferably is increased in order to prevent the mixing of impurities caused by the abrasion of the medium. A diameter of the medium preferably is decreased in order to avoid the destruction of crystals of titanium oxide caused by the impact of the medium.
[0088] Additionally, a surface treatment may be performed as required, depending on the use of the photocatalyst. In this case, examples of a commonly known method for this include a method of causing titanium oxide to support, on its surfaces, an adsorption component or an adsorbent such as silica, apatite, or zeolite, or contrarily, a method of causing titanium oxide to be supported by an adsorbent. In the case where a surface treatment is applied in this manner, materials used in the treatment have to be selected so that no deterioration of the photocatalytic activity should be caused or the deterioration ratio should fall in a tolerable range.
[0089] Zeolite used in the present invention is, for example, a zeolite in which silica and alumina are bonded with each other via oxygen, and typical crystalline forms thereof are the A form, the X form, the beta form, the ferrite form, the mordenite form, the L form, and the Y form. Various types of zeolite having different pore diameters and different shapes can be synthesized by varying the molar component ratio between silica and alumina (hereinafter this ratio also is referred to as “silica/alumina ratio”) and the calcining temperature. It should be noted that a normal zeolite has a particle diameter of 1 to 20 μm and a pore diameter of 0.1 nm to 1 nm.
[0090] In view of the photocatalytic activity and the filter recycling to be described later, the mordenite-form zeolite or the ZSM-5-form zeolite is used preferably as the zeolite. The mordenite-form zeolite (structure code: MOR) generally refers to an orthorhombic-system zeolite that has a unit cell composition of Na8[Al8Si40O96].24H2O and 12-membered-ring two-dimensional pores (effective diameter: 0.6 nm). The ZSM-5-form zeolite (structure code: MFI) generally refers to an orthorhombic-system zeolite that has a unit cell composition of Nan[AlnSi96-nO191].xH2O (n<27) and 10-membered-ring two-dimensional pores (effective diameter: 0.6 nm).
[0091] In the present invention, the function of zeolite is to cause odorous components to get closer to titanium oxide having photocatalytic activity so as to concentrate the odorous components. Therefore, zeolite that exhibits higher performance of adsorbing odorous components is used preferably. Particularly, zeolite capable of adsorbing acetaldehyde is desirable. This is because, among odorous components, acetaldehyde is a component that cannot be adsorbed fully by conventional active carbon and is contained in various types of offensively odorous components. For example, a high-silica/alumina-ratio zeolite is preferable, which exhibits high ability of adsorbing acetaldehyde, and the mordenite-form zeolite having a crystal structure with a pore diameter of about 0.5 nm is more preferable. Further, in order to enhance the odorous component adsorbing property, the silica/alumina ratio of zeolite is, for example, 150 or more, and from the viewpoint of further enhancing the photocatalytic activity, it preferably is 200 or more, more preferably 240 or more, further preferably 1500 or more, and still further preferably 1890 or more. The upper limit of the silica/alumina ratio is, for example, 10000 or less. The pore diameter of zeolite is, for example, 7 Å or less, and from the viewpoint of enhancing the performance of adsorbing organic molecules, it preferably is 4 to 6 Å. The pore diameter of zeolite can be measured by, for example, image observation with a transmission electron microscope (TEM).
[0092] As zeolite, commercially available zeolite may be used Examples of the commercially available zeolite include HSZ-690HOA (manufactured by Tosoh Corporation, mordenite form, silica/alumina ratio: 240, average particle diameter: 13 μm, cation type: H, specific surface area (BET); 450 m<2>/g); HSZ-890HOA (manufactured by Tosoh Corporation, ZSM-5 form, silica/alumina ratio: 1500 to 2000 (average: 1890), average particle diameter: 8 to 14 pun, cation type: H, specific surface area (BET): 280 to 330 m<2>/g); ABSCENTS (TM)-1000 (manufactured by Union Showa K.K., average particle diameter: 3 to 5 μm, cation type: Na); ABSCENTS (TM)-2000 (manufactured by Union Showa K.K., average particle diameter; 3 to 5 am, cation type: Na); Smellrite (TM) (manufactured by Union Showa K.K., average particle diameter: 3 to 5 μm, cation type; Na); and HiSiv (TM)-3000 (manufactured by Union Showa K.K., average particle diameter: 12.7 μm, cation type: Na, pore diameter: 6 Å or less, specific surface area (BET): 400 m<2>/g or more). Each of ABSCENTS (TM)-1000, ABSCENTS (TM)-2000, and Smellrite (TM) contains a plurality of zeolites including a mordenite-form zeolite, and the ratio of the mordenite-form zeolite therein is 90% or more. It should be noted that the average particle diameter of zeolite in the present invention refers to a particle diameter at a cumulative volume percentage of 50%, which can be determined by, for example, a laser diffraction/diffusion method.
[0093] With the photocatalytic material of the present invention, it is possible to decompose odorous components to a concentration lower than that achieved by a conventional composite photocatalyst containing an adsorbent and a photocatalyst (e.g. JP 1(1989)-118635 A, JP 2002-136811 A, and JP 11(1999)-319570 A), so as to achieve deodorization, and preferably, it is possible to decompose acetaldehyde, which is contained much in smoke of tobacco products. Further, the photocatalytic material of the present invention is capable of recovering its ability of adsorbing and/or decomposing odorous components when irradiated with light. Therefore, with the photocatalytic material of the present invention, for example, a filter can be realized whose ability of adsorbing and/or decomposing odorous components can be recovered by irradiation of light for about 2 hours per one day, and preferably, a maintenance-free air purification device can be realized that does not need maintenance of a filter. Light to be irradiated may be any light as long as it contains light having an energy higher than the band gap of the titanium oxide photocatalyst, and it may be ultraviolet rays, preferably light having a wavelength of 380 nm or less, and more preferably black light having a center wavelength in the vicinity of 352 tun.
[0094] The content of zeolite in the photocatalytic material of the present invention (zeolite/(zeolite+titanium oxide photocatalyst)) is, for example, 10 wt % or more; preferably 10 to 90 wt %; more preferably 20 to 80 wt % from the viewpoint of enhancing the photocatalytic activity; and further preferably 20 to 50 wt %.
[0095] The photocatalytic material of the present invention is obtained by mixing the above-described titanium oxide photocatalyst and zeolite by, for example, dry mixing, ball-mill mixing, or wet mixing. Here, in order to enhance the ability of adsorbing odorous components, the mixing is carried out preferably so that the content of zeolite in the photocatalytic material is 10 wt % or more, and more preferably 30 wt % or more. Besides, in order to enhance the photocatalytic activity, the mixing is carried out preferably so that the content of zeolite in the photocatalytic material is 90 wt % or less, and more preferably 40 wt % or less.
[0096] The average particle diameter of the photocatalytic material of the present invention is, for example, 5 μm or less, and from the viewpoint of enhancing the deodorization rate, preferably 1.8 μm or less, more preferably 1.5 μm or less, and further preferably 1 μm or less. In the present invention, the average particle diameter of the photocatalytic material refers to a particle diameter at a cumulative volume percentage of 50%, which can be determined by, for example, a laser diffraction/diffusion method.
[0097] Next, a photocatalytic member of the present invention is described below. The photocatalytic member of the present invention includes a substrate and a photocatalyst layer formed on a surface of the substrate, wherein the photocatalyst layer contains the above-described photocatalytic material of the present invention. With this, for example, the performance of decomposing odorous components and the rate of decomposing the same can be enhanced, for the same reason as described above.
[0098] The photocatalytic member of the present invention is obtained by applying a photocatalytic material over a substrate made of glass or ceramics, the photocatalytic material being obtained by mixing the above-described titanium oxide photocatalyst and zeolite. The application may be carried out in the following manner: a photocatalytic material is dispersed in a solvent such as water or ethyl alcohol, and is applied over a substrate; or a mixture of a photocatalytic material and an inorganic hinder is applied over a substrate. The use of an inorganic binder is preferable since it enhances adhesion of a photocatalytic material to a substrate. It should be noted that examples of the inorganic hinder include tetraethoxysilane (TEOS) and colloidal silica. Examples of the application method include slurry application, spin coating, spraying, and casting coating.
[0099] In the photocatalytic member of the present invention, the content of the photocatalytic material in the photocatalyst layer preferably is in a range of 50 to 100 wt % in order to enhance the photocatalytic activity. The photocatalyst layer may contain other components than the above-described photocatalytic material, such as an inorganic binder, WO3, H2Ti4O2, TiOS, TiON, and SiO2. The content of these other components in the photocatalyst layer is in a range of, for example, 0 to 50 wt %. It should be noted that the thickness of the photocatalyst layer is not limited particularly, but it desirably is about 100 to 500 μm, through which light can penetrate. Further, the thickness of the substrate is not limited particularly, but is about 0.1 to 2 mm, for example.
[0100] If an air permeable substrate is used as the substrate in the photocatalytic member of the present invention, the photocatalytic member of the present invention can be used as a gas permeable filter for the purpose of deodorization. Examples of the substrate having air permeability include nonwoven fabrics, glass fibers, foamed metals, porous ceramics, and foamed resins.
[0101] Next, a purification device of the present invention is described below. The purification device of the present invention is a purification device that includes the above-described photocatalytic member of the present invention, and a light source that irradiates the photocatalytic member with light having a wavelength of 400 nm or less. With this, for example, the performance of decomposing odorous components and the rate of decomposing the same can be enhanced, for the same reason as described above. Preferable examples of the foregoing light source will be described later.
[0102] The purification device of the present invention may be provided further with blowing means that introduces a gas containing organic substances into the photocatalytic member. This is because this configuration makes it possible to use the purification device of the present invention as an air purification device capable of decomposing organic substances in air at a high rate. It should be noted that the blowing means is not limited particularly, and a blower such as a sirocco fan may be used, for example.
[0103] The purification device of the present invention further may include liquid feeding means that introduces a liquid containing organic substances into the photocatalytic member. This is because this configuration makes it possible to use the purification device of the present invention as a liquid purification device capable of decomposing organic substances in the liquid at a high rate. Preferable examples of the foregoing liquid feeding means will be described later.
[0104] Hereinafter, embodiments of the present invention will be described below, with reference to the drawings. It should be noted that the same constituent elements are designated with the same reference numerals, and descriptions of the same are omitted in some cases.
Embodiment 1
[0105] FIG. 1 is a cross-sectional view of a photocatalytic member according to Embodiment 1 of the present invention. As shown in FIG. 1, the photocatalytic member 1 includes a substrate 10, and a photocatalyst layer 11 formed on one of principal faces of the substrate 10. The photocatalyst layer 11 contains the above-described photocatalytic material of the present invention. If the substrate 10 is made of a material that transmits ultraviolet rays, such as glass, quartz, or a fluorocarbon resin, a light source (not shown) can be disposed on a side of the other principal face so as to be isolated from a substance to be treated, whereby the light source can be prevented from being contaminated. It should be noted that the substrate 10 used in the present embodiment might be any material other than a material that transmits ultraviolet rays, as long as it is not degraded by ultraviolet rays. Examples of the material that is not degraded by ultraviolet rays include ceramics such as silica, inorganic materials such as metals, and organic materials such as acrylic resins and urethane resins. The shape of the photocatalytic member 1 also is not limited, and the photocatalytic member 1 may be in a particulate form in which particles have a spherical shape, a polygonal shape, or different shapes in combination; in a sheet form of nonwoven or woven fabric; or in a porous form, a three-dimensional foamed form, a honeycomb form, or a pleated form. Further, as in Embodiment 2 described later, the photocatalyst layers 11 may be provided on both of the principal faces of the substrate 10. The photocatalytic member 1 shown in FIG. 1 may be used in, for example, a co-flow air purification device.
[0106] Further, if the substrate having air permeability is used as the substrate 10 in the photocatalytic member 1, the photocatalytic member 1 can be used as a gas-permeable filter for the purpose of deodorization. Examples of the substrate having air permeability include nonwoven fabrics, glass fibers, foamed metals, porous ceramics, and foamed resins. FIGS. 2A and 2B show perspective views of typical gas-permeable filters of the present invention.
Embodiment 2
[0107] FIG. 3 is a cross-sectional view of a photocatalytic member according to Embodiment 2 of the present invention. As shown in FIG. 3, the photocatalytic member 101 includes a substrate 10, and photocatalyst layers 11, 11 formed on both of principal faces of the substrate 10. The photocatalyst layers 11 has a titanium oxide photocatalyst and zeolite, the titanium oxide photocatalyst containing at least an anatase-type titanium oxide and fluorine, wherein the content of the fluorine in the titanium oxide photocatalyst is 2.5 wt % to 3.5 wt %, and 90 wt % or more of the fluorine is bonded chemically with the anatase-type titanium oxide. With this, the photocatalytic activity is enhanced, and the rate of decomposition of odorous components, for example, can be enhanced. It should be noted that the photocatalyst layer in every embodiment described hereinafter has the same constitutional elements as those of the above-described photocatalyst layer 11.
[0108] The substrate 10 may be made of, for example, a mesh filter sheet composed of warp and weft made of twisted strings of glass fibers. The photocatalyst layer 11 contains, for example, an inorganic binding agent such as silica sol, and the like, other than the above-described titanium oxide photocatalyst.
Embodiment 3
[0109] FIG. 4 is a perspective view of a purification device according to Embodiment 3 of the present invention. As shown in FIG. 4, a co-flow air purification device 2 includes a container 20, a photocatalytic member 21 provided on a bottom face of the container 20, light sources 22 that are disposed in the container 20 so as to face the photocatalytic member 21, and blowing means 23 that blows odorous components in the container 20 toward the photocatalytic member 21. The photocatalytic member 21 includes a substrate 21a, and a photocatalyst layer 21b formed on the substrate 21a. The photocatalyst layer 21b contains the above-described photocatalytic material of the present invention. The container 20 is made of for example, a metal, a resin, or the like. As the light sources 22, black lights having a wavelength of 352 nm at the maximum irradiation intensity, or cold-cathode tubes, can be used. The light intensity of the light sources 22 is, for example, 1 mW/cm<2 >or more, and it is possible to increase the activity degree of the photocatalyst by increasing the light intensity. On the other hand, from the viewpoints of the uniformity of light, the power consumption, and the lifetime, the light intensity preferably is about 0.5 mW/cm<2 >to 5 mW/cm<2>. It should be noted that the distance between the light sources 22 and the photocatalyst layer 21b may be about 1 to 20 cm.
[0110] The co-flow air purification device 2 may be used in the following manner. First, a gaseous substance is introduced toward the photocatalytic member 21 with the blowing means 23, so that the photocatalyst layer 21b adsorbs the gaseous substance. The light sources 22 irradiate the photocatalyst layer 21b with ultraviolet rays, so that the gaseous substance is decomposed oxidatively. Here, the irradiation of the photocatalyst layer 21b with ultraviolet rays may be carried out after the gaseous substance is adsorbed by the photocatalyst layer 21b, or the adsorption of the gaseous substance and the irradiation of ultraviolet rays may be carried out concurrently. It should be noted that an amount of air blown by the blowing means 23 may be set in a range of, for example, 0.5 to 2 m/s.
Embodiment 4
[0111] FIG. 5 is a perspective view of a purification device according to Embodiment 4 of the present invention. As shown in FIG. 5, a cross-flow air purification device 201 includes a container 25, a photocatalytic member 21 disposed on a parting plate 25a provided in the container 25, light sources 22 that are disposed in the container 25 so as to face the photocatalytic member 21, and blowing means 23 that is provided at a lowermost part of the container 25 and introduces odorous components toward the photocatalytic member 21. Outer walls of the container 25 are formed with, for example, a metal or a resin. The parting plate 25a is formed with a substrate having air permeability, such as a punched metal plate. As a substrate 21a of the photocatalytic member 21, a substrate having air permeability can be used, such as a substrate made of a nonwoven fabric, a glass fiber, a foamed metal, a porous ceramics, a foamed resin, or the like. It should be noted that the method of using the cross-flow air purification device 201 is the same as that of the co-flow air purification device 2 described above.
Embodiment 5
[0112] FIG. 6A is a perspective view of an air purification device according to Embodiment 5 of the present invention, and FIG. 6B is a cross-sectional view of the same taken along a line I-I shown in FIG. 6A. As shown in FIGS. 6A and 6B, the air purification device 3 includes a container 30, a photocatalytic member 31 provided at a bottom of the container 30, and light sources 32 that irradiate the photocatalytic member 31 with light having a wavelength of 400 nm or less. Between a ceiling face of the container 30 and the light sources 32, semi-cylindrical reflection plates 33 are provided so that light from the light sources 32 is projected uniformly over the photocatalytic member 31. It should be noted that the reflection plates 33 are made of, for example, stainless steel, aluminum, or the like. Further, the container 30 is made of, for example, a metal, a resin, or the like.
[0113] As shown in FIG. 6B, the photocatalytic member 31 includes a substrate 31a made of ceramics or the like, and a photocatalyst layer 31b formed on a light-source-32-side principal face of the substrate 31a. Further, as shown in FIG. 6A, the photocatalytic member 31 is in a pleated form so that an area where the photocatalytic reaction occurs is expanded. It should be noted that the photocatalyst layer 31b is formed on the substrate 31a by spreading, slurry coating, or another means. Further, the photocatalyst layer 31b may contain, for example, several percents by weight of an inorganic binder or the like so that the adhesion thereof to the substrate 31a is enhanced.
[0114] As the light sources 32, black lights having a wavelength of 352 nm at the maximum irradiation intensity or cold cathode tubes, for example, may be used. The light intensity is, for example, 1 mW/cm<2 >or more, and the activity of the photocatalyst can be increased by increasing the light intensity. However, from the viewpoints of the uniformity of light, the power consumption, and the lifetime, the light intensity preferably is about 0.5 mW/cm<2 >to 5 mW/cm<2>. It should be noted that the distance between the light sources 32 and the photocatalyst layer 31b may be about 1 to 20 cm.
[0115] The air purification device 3 can be used in a relative narrow space or in an air circulation path. For example, the device can be used suitably in a cold air circulation path of a refrigerator, a dust box of a vacuum cleaner, etc. In this case, when the photocatalyst layer 31b of the photocatalytic member 31 is irradiated with ultraviolet rays from the light sources 32, the photocatalyst layer 31b is activated. In this state, when a gas containing organic substances such as odors of the inside of the refrigerator or the vacuum cleaner, for example, is fed via an inlet 30a of the container 30 and comes into contact with the photocatalyst layer 31b, the organic substances are decomposed oxidatively, whereby the gas becomes a less odorous gas and goes out via an outlet 30b of the container 30. This is carried out repetitively, whereby air around the air purification device 3 is purified.
Embodiment 6
[0116] FIG. 7 is a cross-sectional view of an air purification device according to Embodiment 6 of the present invention. As shown in FIG. 7, the air purification device 4 includes a container 40 having an opening 40a, a photocatalytic member 41 disposed so as to cover the opening 40a, and light sources 32 that are disposed at a bottom of the container 40 and irradiate the photocatalytic member 41 with light having a wavelength of 400 nm or less. Further, between the bottom face of the container 40 and the light sources 32, semi-cylindrical reflection plates 33 are provided so that light from the light sources 32 is projected uniformly over the photocatalytic member 41.
[0117] The photocatalytic member 41 includes a substrate 41a made of a material that permeates ultraviolet rays (e.g. glass), and a photocatalyst layer 41b provided on a principal face of the substrate 41a on a side opposite to the light sources 32. Thus, the air purification device 4 of the above-described embodiment is configured so that the light sources 32 are surrounded by the container 40 and the photocatalytic member 41, whereby the light sources 32 are prevented from being contaminated. For example, a maintenance-free cooker hood can be provided if the air purification device 4 is disposed in an airflow path of the cooker hood, in which oil mist flows. In this case, the photocatalyst layer 41b of the photocatalytic member 41 is activated when irradiated with ultraviolet rays from the light sources 32. In this state, when oil mist 42, for example, comes into contact with the photocatalyst layer 41b, the oil mist 42 is decomposed oxidatively, whereby the surface of the photocatalytic member 41 is returned into an original clean state.
Embodiment 7
[0118] FIG. 8 is a cross-sectional view of an air purification device according to Embodiment 7 of the present invention. As shown in FIG. 8, the air purification device 5 includes a container 50, a photocatalytic member 51 that divides the inside of the container 50 into a compartment 50a and a compartment 50b, light sources 32 that are disposed in the compartment 50a and irradiate the photocatalytic member 51 with light having a wavelength of 400 nm or less, and blowing means 52 that is disposed in the compartment 50b and introduces a gas containing organic substances toward the photocatalytic member 51. A wall part of the compartment 50a on a side opposite to the photocatalytic member 51 is made of a prefilter 53, and semi-cylindrical reflect on plates 33 are disposed between the prefilter 53 and the light sources 32 so that the light from the light sources 32 is projected uniformly over the photocatalytic member 51.
[0119] The photocatalytic member 51 includes an air-permeable substrate 51a, and a photocatalyst layer 51b provided on a principal surface of the substrate 51a on the light-source-32 side. As the blowing means 52, a sirocco fan or the like can be used.
[0120] The air purification device 5 of Embodiment 7 can be used as an air vivification device, a deodorizing machine, a purification device for a semiconductor dean room, or an industrial VOC (volatile organic compound) purification device for use in a printing plant or a paint plant. In this case, when the photocatalyst layer 51b of the photocatalytic member 51 is irradiated with ultraviolet rays from the light sources 32, the photocatalyst layer 51b is activated. In this state, the blowing means 52 is driven, and a gas containing organic substances such as odors in the room, VOC, fungus, etc. comes in through the prefilter 53. When the gas comes into contact with the photocatalyst layer 51b, the organic substances in the gas are decomposed oxidatively, and the gas becomes purified, then going out via an outlet 50c provided in a wall of the compartment 50b. This is carried out repetitively, whereby air around the air purification device 5 is purified.
Embodiment 8
[0121] FIG. 9 is a cross-sectional view of a liquid purification device according to Embodiment 8 of the present invention. As shown in FIG. 9, the liquid purification device 6 includes a container 60, a photocatalytic member 61 that divides the inside of the container 60 into a compartment 60a and a compartment 60b, a liquid-feeding valve 62a and a liquid-discharging valve 62b provided in walls of the compartment 60a, and light sources 32 that are disposed in the compartment 60b and irradiate the photocatalytic member 61 with light having a wavelength of 400 nm or less. Further, between the light sources 32 and a wall face of the compartment 60b on a side opposite to the photocatalytic member 61, semi-cylindrical reflection plates 33 are provided so that light from the light sources 32 is projected uniformly over the photocatalytic member 61.
[0122] The photocatalytic member 61 includes a substrate 61a made of a material that transmits ultraviolet rays (e.g. glass), and a photocatalyst layer 61b provided on a principal face of the substrate 61a on a side thereof opposite to the light-source-32 side. The photocatalytic member 61 is in a pleated form so that an area where the photocatalytic reaction occurs is expanded.
[0123] The liquid purification device 6 according to Embodiment 8 is a batch-type purification device that purifies, by natural retention, contaminated water 63 introduced in the compartment 60a. For example, this is suitable for, for example, a domestic purification pot, and is effective for decomposing and removing frowzy odor, trihalomethane, etc. In this case, when water is fed into the compartment 60a and the photocatalyst layer 61b of the photocatalytic member 61 is irradiated with ultraviolet rays from the light source 32, the photocatalyst layer 61b is activated. In this state, when organic substances such as the frowzy odor, trihalomethane, etc. in, water that is being purified come into contact with the photocatalyst layer 61b, the organic substances are decomposed oxidatively, whereby the water is cleaned. It should be noted that if liquid-feeding means (not shown) such as a pump for feeding contaminated water from the liquid-feeding valve 62a to the compartment 60a is disposed, for example, outside the container 60, organic substances in the contaminated water can be decomposed at a high rate.
EXAMPLES
[0124] Hereinafter, Examples of the present invention will be described together with Reference Examples and Comparative Examples. It should be noted that the present invention is not limited to the following Examples.
Reference Example 1
[0125] A solution of titanyl sulfate (manufactured by SAKAI Chemical Industry Co., Ltd.) in which the concentration as to titanium oxide was 100 g/L and the concentration as to sulfuric acid was 250 g/L was kept at 100° C. for 3 hours to be hydrolyzed thermally. The pH of the obtained slurry aqueous solution was adjusted with ammonia water until the pH became 8.0, and was filtered. Then, the substance obtained by filtration was washed thoroughly with water to remove salts as impurities. Here, the water washing was performed until the electric conductivity of the washing liquid became 200 μS/cm. Pure water was added to the cake thus obtained so that the concentration of the titanium oxide therein would become 150 g/L, and was stirred, whereby a re-dispersion solution of the titanium oxide was prepared. After that, hydrofluoric acid (manufactured by Wako Pure Chemical Industries, Ltd., guaranteed reagent) equivalent to 5.0 wt % in terms of fluorine (element) with respect to titanium oxide was added to this re-dispersion solution so as to cause a reaction at 25° C. for 60 minutes while the pH thereof was kept at 3. The obtained reaction product was washed thoroughly with water to remove salts as impurities. Here, the water washing was performed until the electric conductivity of the washing liquid became 1 mS/cm or less. Then, this was dried in air at 130° C. for 5 hours so as to be powdered, whereby a titanium oxide photocatalyst of Reference Example 1 was obtained. The titanium oxide photocatalyst of Reference Example 1 had a specific surface area of 259 m<2>/g (determined by the BET method). Further, regarding the obtained titanium oxide photocatalyst, the amount of eluted fluorine was measured by a measuring method to be described later, and was found to be 5 wt %. That is, 95 wt % of fluorine in the titanium oxide photocatalyst was bonded chemically to the anatase-type titanium oxide. It should be noted that a part of the above re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered, and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 2 μmol/g.
Reference Example 2
[0126] A titanium oxide photocatalyst of Reference Example 2 was obtained in the same manner as in Reference Example 1 described above, except that a hydrofluoric acid (manufactured by Wako Pure Chemical Industries, Ltd., guaranteed reagent) equivalent to 7.5 wt % in terms of fluorine (element) was used as a hydrofluoric acid to be added to the re-dispersion solution. The titanium oxide photocatalyst of Reference Example 2 had a specific surface area of 251 m<2>/g (determined by the BET method), and the amount of eluted F thereof was 5 wt %. That is, 95 wt % of fluorine in the titanium oxide photocatalyst was bonded chemically to the anatase-type titanium oxide. It should be noted that in the preparation of the titanium oxide photocatalyst of Reference Example 2, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 3 μmol/g.
Reference Example 3
[0127] A titanium oxide photocatalyst of Reference Example 3 was obtained in the same manner as in Reference Example 1 described above, except that hydrofluoric acid (manufactured by Wako Pure Chemical Industries, Ltd., guaranteed reagent) equivalent to 10 wt % in terms of fluorine (element) was used as a hydrofluoric acid to be added to the re-dispersion solution. The titanium oxide photocatalyst of Reference Example 3 had a specific surface area of 260 m<2>/g (determined by the BET method), and the amount of eluted F thereof was 5 wt %. That is, 95 wt % of fluorine in the titanium oxide photocatalyst was chemically bonded to the anatase-type titanium oxide. It should be noted that in the preparation of the titanium oxide photocatalyst of Reference Example 3, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 1 μmol/g.
Reference Example 4
[0128] A titanium oxide photocatalyst of Reference Example 4 was obtained in the same manner as in Reference Example 1 described above, except that the temperature for the thermal hydrolysis of titanyl sulfate was set at 85° C. The titanium oxide photocatalyst of Reference Example 4 had a specific surface area of 340 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Reference Example 4, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 7 μmol/g.
Reference Example 5
[0129] A titanium oxide photocatalyst of Reference Example 5 was obtained in the same manner as in Reference Example 1 described above, except that the re-dispersion solution prepared was held in an autoclave at 100° C. for 5 hours and thereafter hydrofluoric acid was added to the re-dispersion solution. The titanium oxide photocatalyst of Reference Example 5 had a specific surface area of 205 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Reference Example 5, a part of the re-dispersion solution after it was held at 100° C. for 5 hours was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 8 μmol/g.
Reference Example 6
[0130] A titanium oxide photocatalyst of Reference Example 6 was obtained in the same manner as in Reference Example 1 described above, except that ammonium fluoride (manufactured by Wako Pure Chemical Industries, Ltd., guaranteed reagent) equivalent to 5.0 wt % in terms of fluorine (element) was added in place of hydrofluoric acid and that, after the addition of ammonium fluoride, a reaction was allowed to occur with the pH being maintained at 1 using hydrochloric acid. The titanium oxide photocatalyst of Reference Example 6 had a specific surface area of 270 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Reference Example 6, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 4 μmol/g.
Reference Example 7
[0131] A titanium oxide photocatalyst of Reference Example 7 was obtained in the same manner as in Reference Example 1 described above, except that sodium fluoride (manufactured by Wako Pure Chemical Industries, Ltd., guaranteed reagent) equivalent to 5.0 wt % in terms of fluorine (element) was added in place of hydrofluoric acid and that, after the addition of sodium fluoride, a reaction was allowed to occur with the pH being maintained at 1 using hydrochloric acid. The titanium oxide photocatalyst of Reference Example 7 had a specific surface area of 268 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Reference Example 7, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 5 μmol/g.
Reference Example 8
[0132] A titanium oxide photocatalyst of Reference Example 8 was obtained in the same manner as in Reference Example 1 described above, except that sodium fluoride (manufactured by Wako Pure Chemical Industries, Ltd., guaranteed reagent) equivalent to 5.0 wt % in terms of fluorine (element) was added in place of hydrofluoric acid and that, after the addition of sodium fluoride, a reaction was allowed to occur with the pH being maintained at 3 using hydrochloric add. The titanium oxide photocatalyst of Reference Example 8 had a specific surface area of 272 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Reference Example 8, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 5 μmol/g.
Comparative Example 1
[0133] A titanium oxide photocatalyst of Comparative Example 1 was obtained in the same manner as in Reference Example 1 described above, except that a hydrofluoric acid (manufactured by Wako Pure Chemical Industries, Ltd., guaranteed reagent) equivalent to 4 wt % in terms of fluorine (element) was used as hydrofluoric acid to be added to the re-dispersion solution. The titanium oxide photocatalyst of Comparative Example 1 had a specific surface area of 268 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Comparative Example 1, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 6 μmol/g.
Comparative Example 2
[0134] A titanium oxide photocatalyst of Comparative Example 2 was obtained in the same manner as in Reference Example 1 described above, except that when the substance obtained by filtration was washed with water and a cake was obtained, the water washing was performed until the electric conductivity of the washing liquid became 1 mS/cm. The titanium oxide photocatalyst of Comparative Example 2 had a specific surface area of 276 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Comparative Example 2, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 6 μmol/g.
Comparative Example 3
[0135] A titanium oxide photocatalyst of Comparative Example 3 was obtained in the same manner as in Reference Example 1 described above, except that when the pH of the obtained shiny aqueous solution was adjusted, the adjustment was carried out icing sodium hydroxide, and that when the obtained reaction product was washed with water, the water washing was performed until the electric conductivity of the washing liquid became 400 μS/cm. The titanium oxide photocatalyst of Comparative Example 3 had a specific surface area of 255 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Comparative Example 3, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 30 μmol/g.
Comparative Example 4
[0136] A titanium oxide photocatalyst of Comparative Example 4 was obtained in the same manner as in Reference Example 1 described above, except that when the pH of the obtained slurry aqueous solution was adjusted, the adjustment was carried out using ammonia water until the pH became 7.0. The titanium oxide photocatalyst of Comparative Example 4 had a specific surface area of 271 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Comparative Example 4, a part of the redispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 13 μmol/g.
Comparative Example 5
[0137] After the re-dispersion solution was prepared in the same manner as in Reference Example 1 described above, sodium fluoride (manufactured by Wako Pure Chemical Industries, Ltd., guaranteed reagent) equivalent to 5.0 wt % in terms of fluorine (element) with respect to titanium oxide was added to this re-dispersion solution, and a reaction was allowed to occur at 25° C. for 60 minutes with the pH thereof being maintained at 1. Thereafter, without the obtained reaction product being washed with water, the total amount of the dispersion solution was dried and solidified by evaporation in air at 130° C. for 10 hours so as to be powdered, whereby a titanium oxide photocatalyst of Comparative Example 5 was obtained. The titanium oxide photocatalyst of Comparative Example 5 had a specific surface area of 269 m<2>/g (determined by the BET method), and the amount of eluted F thereof was 50 wt %. That is, the proportion of fluorine chemically bonded to the anatase-type titanium oxide was 50 wt %. It should be noted that in the preparation of the titanium oxide photocatalyst of Comparative Example 5, a part of the re-dispersion solution was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 4 μmol/g.
Comparative Example 6
[0138] A titanium oxide photocatalyst of Comparative Example 6 was obtained in the same manner as in Reference Example 1 described above, except that the re-dispersion solution prepared was held in an autoclave at 130° C. for 1 hour so that a hydrothermal reaction occurred, and thereafter hydrofluoric acid was added thereto. The titanium oxide photocatalyst of Comparative Example 6 had a specific surface area of 185 m<2>/g (determined by the BET method). It should be noted that in the preparation of the titanium oxide photocatalyst of Comparative Example 6, a part of the re-dispersion solution after it was held at 130° C. for 1 hour was dried at 50° C. under a reduced pressure so as to be powdered and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 5 μmol/g.
Comparative Example 7
[0139] A solution of titanyl sulfate (manufactured by SAKAI Chemical Industry Co., Ltd.) in which the concentration as to titanium oxide was 100 g/L and the concentration as to sulfuric add was 250 g/L was kept at 100° C. for 3 hours to be hydrolyzed thermally. The pH of the obtained slurry aqueous solution was adjusted with ammonia water until the pH became 8.0, and was filtered. Then, the substance obtained by filtration was washed thoroughly with water to remove salts as impurities. Here, the water washing was performed until the electric conductivity of the washing liquid became 200 μS/cm. The cake obtained was dried in air at 130° C. for 5 hours so as to be powdered, whereby a titanium oxide photocatalyst of Comparative Example 7 was obtained. The titanium oxide photocatalyst of Comparative Example 7 had a specific surface area of 274 m<2>/g (determined by the BET method), and the amount of eluted F was found to be 0 wt %. It should be noted that in the preparation of the titanium oxide photocatalyst of Comparative Example 7, a part of the cake obtained was dried at 50° C. under a reduced pressure so as to be powdered, and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 2 μmol/g.
Comparative Example 8
[0140] To 20 g of titanium hydroxide (principal component: β-titanium acid, manufactured by SAKAI Chemical Industry Co., Ltd.), 50 g of a 0.15 wt % aqueous ammonium fluoride solution was added and dried, whereby a mixture was obtained. 3.2 g of the obtained mixture was fed into an electric furnace (energy-saving temperature-rising electric furnace manufactured by MOTOYAMA, trade name: RH-2025D), and the temperature was increased from room temperature to 350° C. in air for 105 minutes. After it was maintained in this state for 1 hour so as to be calcined, it was cooled gradually, whereby 2.9 g of titanium oxide was obtained as a titanium oxide photocatalyst of Comparative Example 8. The titanium oxide photocatalyst of Comparative Example 8 had a specific surface area of 44 m<2>/g (determined by the BET method), and the amount of eluted F thereof was 25 wt %. It should be noted that in the preparation of the titanium oxide photocatalyst of Comparative Example 8, a part of the cake obtained was dried at 50° C. under a reduced pressure so as to be powdered, and the amount of n-butylamine adsorbed by the obtained powder was measured by the aforementioned measuring method. The amount was found to be 8 μmol/g.
[0141] Analysis of Physical Properties
[0142] As to each of the titanium oxide photocatalysts of Reference Examples 1 to 8 and Comparative Examples 1 to 8, the content of fluorine and the content of sodium were determined. The content of fluorine was analyzed by absorptiometry (JIS K0102), and the content of fluorine in the photocatalyst was determined by percentage by weight. Further, the content of sodium was analyzed by inductively coupled high-frequency plasma spectrometry (ICP spectrometry), and the content of sodium in the photocatalyst was determined as ppm by weight. Further, in the preparation of each titanium oxide photocatalyst, a part of the re-dispersion solution obtained (a part of the cake in the case of Comparative Example 7) was dried at 50° C. under a reduced pressure so as to be powdered. The content of sodium in the powder was analyzed by ICP spectrometry, and the content of sodium in the starting material was determined as ppm by weight. Further, as to each of the titanium oxide photocatalysts of Reference Examples 1 and 2 and Comparative Examples 1, 2, 4, and 7, the ratio by weight of fluorine on surfaces of the photocatalyst with respect to titanium on the surfaces of the photocatalyst (hereinafter this ratio is referred to as “surface F ratio”) was determined by a method described below. The results of the same are shown in Table 1. It should be noted that, as shown in Table 1, the contents of sodium of Reference Examples 1 to 3, 6 to 8 and Comparative Examples 1 and 5 were different even though the re-dispersion solutions thereof were prepared in the same way. As to the reason for this, it is considered that the difference was caused by variations in lots of titanyl sulfate as a raw material, and analytical errors. Further, the titanium oxide photocatalysts in Reference Examples 1 to 8 were analyzed by a photoelectron spectroscopic analyzer, and every photocatalyst showed a spectrum in which a peak top of F1s appeared in a range of 683 eV to 686 eV.
[0143] Monument of Electric Conductivity
[0144] The electric conductivity of water (25° C.) collected after washing was measured with a pH/cond meter (manufactured by HORIBA, Ltd, D-54 (trade name)).
[0145] Determination of Anatase Type
[0146] Each of the titanium oxide photocatalysts obtained in Reference Examples 1 to 8 was analyzed with a powder X-ray diffractometer (working electrode: copper electrode), and a diffraction peak appeared at a diffraction angle 2θ=25.5°. This means that every titanium oxide photocatalyst obtained in Reference Examples 1 to 8 was determined to be an anatase type.
[0147] Measurement of Amount of Eluted Fluorine
[0148] 0.1 g of titanium oxide obtained in Reference Example or Comparative Example was suspended in 100 ml of pure water, and after irradiated with ultrasonic waves for 15 minutes, it was centrifuged. The supernatant fluid obtained was subjected to colorimetric analysis using PACKTEST (registered trade name) manufactured by Kyoritsu Chemical Check Lab, Corp., and an amount of eluted fluorine ions was determined. Based on this amount of eluted fluorine, the amount of fluorine chemically bonded to titanium oxide can be determined.
[0149] Method for Measurement of Surface F Ratio
[0150] As to each of the titanium oxide photocatalyst powders, 1 g of the same was weighed, placed in a 10-mm-diameter molding die, and was pressed by stamping in a manner such that a load of 1 t/cm<2 >was applied to each piece, so as to be formed into a 10-mm-diameter pellet. Then, this molded pellet was broken so that a small fraction having a flat surface was produced, and this fraction was fixed on a sample stage with a double-faced tape, as a sample to be subjected to photoelectron spectroscopy. This sample was left in vacuum for one day, and thereafter photoelectron spectra emitted from the 2p orbital of titanium (Ti), the is orbital of fluorine (F), and the is orbital of carbon (C) were measured with a photoelectron spectroscope (ESCA-850 model manufactured by Shimadzu Corporation, source of X-rays: MgKα) under the conditions of 8 kV and 30 mA. Then, with a value of the same emitted from the is orbital of C thus determined being compensated to be 284.8 eV, energies of the spectra determined by the measurement at the 2p orbital of Ti and the is orbital of F were compensated accordingly. With bonding energies of the spectrum being set to the corrected values, respectively, a value determined by the following calculation formula is assumed to be the surface F ratio:
[0000]
Surface F ratio=NF×19.0/(NTi×47.9)
[0000] where NF represents the number of atoms of F determined from a spectral area of the 1s orbital of F, NTi represents the number of atoms of Ti determined from a spectral area of the 2p orbital of Ti.
[0151] Evaluation of Photocatalytic Activity
[0152] Using the respective titanium oxide photocatalysts of Reference Examples 1 to 8 and Comparative Examples 1 to 8, air purification devices as shown in FIG. 4 were assembled, and the photocatalytic activities were evaluated. Acetaldehyde was used as an odorous component. The configuration of the photocatalytic member and the evaluation method are described below.
[0153] Configuration of Photocatalytic Member
[0154] As the photocatalytic member 21, a photocatalytic member was prepared that included a 12 cm×10 cm substrate 21a made of glass and a photocatalyst layer 21b that was formed on the substrate 21a so as to have a size of 12 cm×6.4 cm (thickness: 3 μm). It should be noted that the photocatalyst layer 21b was formed in the following manner: 5 g of each of the powders made of the titanium oxide photocatalysts of Reference Examples 1 to 8 and Comparative Examples 1 to 8 was dispersed in ethanol so as to become a paste, and the paste was applied over the substrate 21a, and was left at room temperature for one hour so that most of ethanol evaporated.
[0155] Evaluation Method Using Air Purification Device
[0156] Before the photocatalytic member 21 was placed in the container 20, the photocatalyst layer 21b was irradiated with ultraviolet rays having an intensity of 5 mW/cm<2 >using the light sources 22 (center wavelength: 352 nm, UV lamps manufactured by Toshiba Lighting & Technology Corporation) for 240 minutes, whereby organic substances adhering to the surface of the photocatalyst layer 21a were decomposed completely. This photocatalytic member 21 was then left to stand in the container 20 (capacity: 16 L). The container 20 was filled with acetaldehyde so that the concentration of the acetaldehyde gas in the container became 500 mol ppm, and was sealed. After this was left to stand for 60 minutes without ultraviolet rays irradiation over the photocatalyst layer 21b and an adsorption equilibrium was reached, a change in the concentration of the acetaldehyde in the container 20 and an amount of generated carbon dioxide were analyzed by gas chromatography while the photocatalyst layer 21b was irradiated with ultraviolet rays having an intensity of 21 mW/cm<2 >using the light sources 22. The superiorities and inferiorities of the respective titanium oxide photocatalysts were evaluated based on the carbon dioxide generation rates thus determined. The results are shown in Table 1.
[0000]
TABLE 1
Physical property of
starting material Physical property of titanium oxide photocatalyst
n-butylamine Proportion of
adsorption chemically bonded Carbon dioxide
amount Na content F content Na content Na content/ fluorine generation rate
(μmol/g) (wt ppm) (wt %) (wt ppm) F content Surface F ratio (wt %) (mol ppm/hour)
Ref Ex. 1 2 802 2.9 229 0.0079 0.1 95 745
Ref. Ex. 2 3 634 3.1 120 0.0039 0.13 95 772
Ref. Ex. 3 1 440 3.4 5 0.0002 — 95 818
Ref Ex. 4 7 824 3 290 0.0097 — — 650
Ref Ex. 5 8 770 2.7 201 0.0074 — — 670
Ref. Ex. 6 4 806 2.5 230 00092 — — 693
Ref Ex. 7 5 802 2.8 270 0.0096 — — 689
Ref. Ex. 8 5 815 2.5 293 0.0117 — — 606
Comp. Ex 1 6 812 2.3 200 0.0087 0.07 — 540
Comp. Ex. 2 6 1150 2.3 300 0.013 0.07 — 509
Comp. Ex 3 30 4760 1.6 980 0.0613 — — 520
Comp. Ex 4 13 957 2.2 250 0.0114 0.07 — 571
Comp. Ex. 5 4 813 5 60000 1.2 — 50 300
Comp Ex 6 5 816 2.1 199 0.0095 — — 387
Comp. Ex. 7 2 827 0 810 — 0 0 321
Comp Ex 8 8 77 1.5 9 0.0006 — 75 275
[0157] Table 1 shows that all the titanium oxide photocatalysts of Reference Examples 1 to 8, in which the content of fluorine was 2.5 wt % to 3.5 wt %, exhibited faster carbon dioxide generation rates (acetaldehyde decomposition rates) and superior photocatalytic activity compared to those of Comparative Examples 1 to 8, in which the content of fluorine was out of the foregoing range. Besides, as shown in Table 1, the n-butylamine adsorption amounts of the titanium oxide photocatalysts of Reference Examples 3 to 3, 6 to 8 and Comparative Examples 1 and 5 were different even though the re-dispersion solutions thereof were prepared in the same way. It is considered that the difference was caused by variations in lots of titanyl sulfate as a raw material, and analytical errors.
[0158] Evaluation of Photocatalytic Activity 2
[0159] Using the titanium oxide photocatalysts of Reference Examples 1 and 2 and Comparative Examples 1 and 7, photocatalytic members were produced, and using these photocatalytic members, liquid purification devices shown in FIG. 10 were assembled. Using each of these liquid purification devices, photocatalytic activity thereof was evaluated. Methylene blue, which is a pigment, was used as the liquid-form organic substance, and a degree of discoloration of methylene blue with time was measured. The configuration of the liquid purification device and the evaluation method are described below.
[0160] Configuration of Liquid Purification Device
[0161] FIG. 10 is a perspective view of a liquid purification device used in the evaluation of photocatalytic activity. As shown in FIG. 10, the liquid purification device 8 includes a Petri dish 80, a photocatalytic member 71 disposed in the Petri dish 80, a black light 72 that was disposed so as to face the photocatalytic member 71, and a stand 81 for fixing the black light 72. The photocatalytic member 71 was produced in the same manner as the method of producing the photocatalytic member used in the above-described evaluation method using the air purification device.
[0162] Evaluation Method Using Liquid Purification Device
[0163] After a solution obtained by adding 1 mg of methylene blue into 200 mL of pure water was fed into the Petri dish 80, the photocatalyst layer 71b was irradiated with ultraviolet rays having an intensity of 1 mW/cm<2 >using the black light 72 (center wavelength: 352 nm, UV lamp manufactured by Toshiba Lighting & Technology Corporation), without light entering from the outside. Then, from the start of the irradiation until 4 hours later, 5 mL of the foregoing solution was sampled every one hour. Each sample was centrifuged using a centrifuge at 3000 rpm for 15 minutes, and a supernatant fluid was sampled. Then, the supernatant fluid thus sampled was placed in a quartz cell, and an absorbance thereof was measured using a spectrophotometer (manufactured by JASCO Corporation, V-570 model). It should be noted that since a phenomenon in which the wavelength of absorbed light shifted as the decomposition of methylene blue proceeded was observed, the absorbance at the top point (peak position) of the curve was assumed to be the absorbance of the sample. Then, an absorbance of an aqueous methylene blue solution prepared at a different concentration preliminarily (standard fluid) was measured so that a calibration curve was produced, and a concentration (mg/L) of the methylene blue renal fling in the solution was determined based on the foregoing calibration curve and the absorbance of the supernatant fluid measured by the aforementioned method. The results are shown in FIG. 11.
[0164] As is clear from FIG. 11, in the cases of the titanium oxide photocatalysts of Reference Examples 1 and 2, significantly higher rates of discoloration (decomposition of methylene blue) were observed, as compared with the cases of Comparative Examples 1 and 7, which means that the titanium oxide photocatalysts of Reference Examples 1 and 2 exhibited excellent photocatalytic activity.
Examples 1 to 10
[0165] As Examples 1 to 10, photocatalytic materials were prepared by physically mixing the titanium oxide photocatalyst of Reference Example 3 described above and zeolite for about 5 minutes using a mortar. Zeolite used for Examples 1 to 9 was HSZ-890HOA, ZSM-5 form (silica/alumina ratio=1890) manufactured by Mach Corporation, and zeolite used for Example 10 was HSZ-690HOA, mordenite form (silica/alumina ratio=240) manufactured by Tosoh Corporation. It should be noted that the content of zeolite in each photocatalytic material was as shown in Table 2. As the titanium oxide photocatalyst of Comparative Example 9, SSP-25 manufactured by SAKAI Chemical Industry Co., Ltd. was prepared.
[0166] Evaluation of Photocatalytic Activity 3
[0167] Photocatalytic materials were produced from materials obtained in Examples 1 to 10, Reference Example 3, and Comparative Example 9, air purification devices shown in FIG. 4 were assembled using these, and photocatalytic activity was evaluated in the same manner as described above. The results are shown in Table 2. It should be noted that Table 2 shows ratios of carbon dioxide generation rates of Examples 1 to 10 and Reference Example 3 with respect to the carbon dioxide generation rate of Comparative Example 9, which is assumed to be 1.0.
[0000]
TABLE 2
Evaluation of photocatalytic activity
Titanium Ratio of
oxide carbon
Fluorine Zeolite dioxide Generation
content Content generation rate
(wt %) (wt %) Trade name rate (mol ppm/hr)
Ex. 1 3.4 10 HSZ-890HOA 3.8 1151
Ex. 2 3.4 20 HSZ-890HOA 5.5 1666
Ex. 3 3.4 30 HSZ-890HOA 6.2 1878
Ex. 4 3.4 40 HSZ-890HOA 6.0 1818
Ex. 5 3.4 50 HSZ-890HOA 5.5 1666
Ex. 6 3.4 60 HSZ-890HOA 4.6 1394
Ex. 7 3.4 70 HSZ-890HOA 4.0 1212
Ex. 8 3.4 80 HSZ-890HOA 3.8 1151
Ex. 9 3.4 90 HSZ-890HOA 3.6 1091
Ex. 10 3.4 30 HSZ-690HOA 5.9 1787
Ref. 3.4 0 — 2.7 818
Ex. 3
Comp. 0 0 — 1.0 303
Ex. 9
[0168] As is clear from Table 2, each of the photocatalytic members of Example 1 to 10 exhibited a faster carbon dioxide generation rate (acetaldehyde decomposition rate) as compared with Reference Example 3 and Comparative Example 9, i.e., superior photocatalytic activity. It should be noted that in Examples 1 to 10, HSZ-890HOA or HSZ-690HOA manufactured by Tosoh Corporation was used as zeolite, but the present invention is not limited to this configuration. The same effect can be achieved in the case where, for example, ABSCENTS (TM)-1000 manufactured by Union Showa K.K., ABSCENTS (TM)-2000 manufactured by Union Showa K.K., Smellrite elm manufactured by Union Showa K.K., or the like is used.
Examples 11 to 18
[0169] Each of photocatalytic materials of Examples 11 to 18 shown in Table 3 below was prepared by physically mixing the titanium oxide photocatalyst of Reference Example 3 or 6 and zeolite for about 5 minutes using a mortar. Using the photocatalytic materials of Examples 11 to 18, photocatalytic members were produced in the same manner as in Examples 1 to 10, and photocatalytic activity thereof was evaluated. The results are shown in Table 3 below, together with the trade names of zeolite used, and the contents of zeolite in the photocatalytic materials. Ratios of carbon dioxide generation rates shown in Table 3 are ratios of the rates with respect to the carbon dioxide generation rate of Comparative Example 9, which is assumed to be 1.0.
[0000]
TABLE 3
Titanium oxide Evaluation of photocatalytic activity
Fluorine Zeolite Ratio of
content Content carbon dioxide Generation rate
(wt %) (wt %) Trade name generation rate (mol ppm/hr)
Ex. 11 2.5 30 HSZ-890HOA 4.5 1368
Ex. 12 2.5 60 HSZ-890HOA 3.8 1151
Ex. 13 2.5 90 HSZ-890HOA 3.5 1060
Ex. 14 3.4 30 ABSCENTS-1000 5.8 1757
Ex. 15 3.4 30 ABSCENTS-2000 6.0 1818
Ex. 16 3.4 30 Smellrite 6.0 1818
Ex. 17 3.4 30 HiSiv-3000 5.9 1789
Ex. 18 3.4 30 HiSiv-3000 (50 wt %) 6.1 1836
HSZ-890HOA (50 wt %)
[0170] As is clear from Table 3, each Example exhibited a carbon dioxide generation rate (acetaldehyde decomposition rate) of more than 1000 mol ppm/hour, which means each Example exhibited superior photocatalytic activity.
Example 19
[0171] A punched aluminum plate whose surfaces had been anodized (aperture ratio: 35.4%, 20 cm×10 cm, thickness: 1 mm) was prepared as a substrate. The photocatalytic material of Example 3 (5 g) was dispersed in 10 ml of ethanol so that a paste was obtained. This paste-form photocatalytic material was applied over the substrate (18 cm×8 cm) and was left to stand at room temperature for one hour. Thereafter, it was dried at 80° C. for 6 hours in a drier, whereby a photocatalyst layer (thickness: about 70 μm) was formed. In the obtained photocatalyst layer, about 1 g of the photocatalytic material was fixed. The obtained photocatalyst layer was irradiated with ultraviolet rays having an intensity of 5 mW/cm<2 >(center wavelength: 352 nm, black-light-blue lamp under the brand name of “National”) for 2 hours so that organic substances adhering to a surface of the photocatalyst layer were decomposed. Thus, a photocatalytic member in a filter form was produced.
Example 20
[0172] A photocatalytic member was produced in the same manner as in Example 19 except that the photocatalytic material of Example 9 was used as the photocatalytic material.
Example 21
[0173] A photocatalytic member was produced in the same manner as in Example 19 except that the photocatalytic material of Example 1 was used as the photocatalytic material.
Example 22
[0174] A photocatalytic member was produced in the same manner as in Example 19 except that the photocatalytic material of Example 16 was used as the photocatalytic material.
Comparative Example 10
[0175] Active carbon (GA crushed carbon, manufactured by Cataler Corporation) was dispersed in 10 ml of ethanol so that a paste was obtained. This paste-form photocatalytic material was applied over the same substrate as that in Example 19 (18 cm×8 cm) and was left to stand at room temperature for one hour. Thereafter, it was dried at 80° C. for 6 hours in a drier, whereby a filter was produced. The obtained filter was in such a state that granular active carbon was deposited on the substrate, and a thickness of the active carbon layer could not be determined. The active carbon contained in the active carbon layer was about 1 g (weight in a dried state).
Comparative Example 11
[0176] Titanium oxide (trade name: P25, Nippon Aerosil Co., Ltd., anatase-type titanium oxide: 80%, rutile-type titanium oxide: 20%) not containing fluorine and zeolite (HSZ-890HOA, manufactured by Tosoh Corporation) were mixed physically for about 5 minutes with a mortar, so that a photocatalytic material was prepared. A photocatalytic member was produced in the same manner as in Example 19 except that the foregoing photocatalytic material was used as the photocatalytic material.
Comparative Example 12
[0177] The titanium oxide photocatalyst of Reference Example 3 and zeolite (HSZ-390HUA, manufactured by Tosoh Corporation, Y-form zeolite, silica/alumina ratio (molar component ratio: 400)) were mixed physically for about 5 minutes with a mortar, so that a photocatalytic material was prepared. A photocatalytic member was produced in the same manner as in Example 19 except that the foregoing photocatalytic material was used as the photocatalytic material.
[0178] Evaluation of Filter Recycling
[0179] Each of the photocatalytic members of Examples 19 to 22 and Comparative Examples 11 and 12 and the filter of Comparative Example 10 were disposed on the parting plate 25a of the cross-flow air purification device (capacity: 100 L) shown in FIG. 5. The device 201 was filled with acetaldehyde so that the concentration of acetaldehyde in the device 201 became 10 mol ppm, and was sealed. After this, it was left to stand for 60 minutes without ultraviolet rays irradiation over the photocatalyst layer 21b. After it was checked and seen that an adsorption equilibrium was reached, the photocatalyst layer 21b was irradiated with ultraviolet rays having an intensity of 1 mW/cm<2 >with the light source 22 (center wavelength: 352 nm, black-light-blue lamp under the brand name of “National”) for 2 hours, whereby aldehyde adhering to the titanium oxide photocatalyst and zeolite was decomposed and removed. The concentration of acetaldehyde after the decomposition and removal was analyzed with a gas chromatograph. The device 201 again was filled with acetaldehyde so that the concentration of acetaldehyde became 10 mol ppm. Then, 5 cycles of the leaving of the same to stand for 60 minutes, the irradiation with ultraviolet rays, the analysis, and the refilling were carried out. The ratio of deodorization (deodorization ratio) and the ratio of decrease in adsorbability (adsorbability decrease ratio) were calculated using the determined concentrations of acetaldehyde. The determined ratios of decrease in adsorbability are shown in Table 4 below.
[0000] [mathematical formula]
Adsorbability decrease ratio (deodorization ratio after 1 cycle)−(deodorization ratio after 5 cycles)
[0000]
TABLE 4
Titanium oxide
Fluorine Zeolite
content Content Adsorption
(wt %) (wt %) Trade name decrease ratio
Ex. 19 3.4 30 HSZ-890HOA None
Ex. 20 3.4 90 HSZ-890HOA None
Ex. 21 3.4 10 HSZ-890HOA 1% or less
Ex. 22 3.4 30 Smellrite 1% or less
Comp. Ex. 10 3.4 0 Active carbon 78%
Comp. Ex. 11 0 30 — 10%
Comp. Ex. 12 3.4 30 HSZ-390HUA 8%
[0180] All of the photocatalytic members of Examples 19 to 22 maintained high adsorbability, with substantially no decrease in adsorbability even after 5 cycles of adsorption and decomposition. Besides, it was proved that when the photocatalytic members of Examples 19 to 22 were irradiated with ultraviolet rays of 1 mW/cm<2 >for 2 hours, their ability of adsorbing and decomposing acetaldehyde could be recovered (the photocatalytic members could be recycled).
INDUSTRIAL APPLICABILITY
[0181] The present invention is useful for a purification device used for the purpose of, for example, deodorization, odor elimination, air purification, and liquid purification.