KR102185603B1 - Transition metal compound-loaded titanium oxide suspension - Google Patents

Abstract

An object of the present invention is to provide a transition metal compound-supported titanium oxide suspension that includes a transition metal compound-supported titanium oxide crystal, has a very low content of ionic impurities, has excellent responsiveness to visible light, and exhibits excellent photocatalytic performance. Is to do.
The transition metal compound-supported titanium oxide suspension of the present invention is a suspension of transition metal compound-supported titanium oxide having an average aspect ratio (long/short axis) of 1.5 or more, obtained by supporting a transition metal compound on crystalline titanium oxide, wherein the transition metal compound is supported. When titanium oxide is contained in an amount of 4% by weight or more, the electrical conductivity of the supernatant of the suspension is not more than 300 μS/cm. As the crystalline titanium oxide, a rutile type titanium oxide having a crystal face 110 and a crystal face 111 and/or a rutile type titanium oxide having a crystal face 110, a crystal face 111 and a crystal face (001) is preferable.

Description

Titanium oxide suspension supported by a transition metal compound {TRANSITION METAL COMPOUND-LOADED TITANIUM OXIDE SUSPENSION}

The present invention relates to a suspension containing a transition metal compound-supported titanium oxide. The transition metal compound-supported titanium oxide suspension has excellent response to visible light and can exhibit excellent photocatalytic performance.

Transition metal compound-supported titanium oxide has a photocatalytic ability, and by irradiating light such as visible light, it exhibits strong oxidizing power, and it is possible to decompose harmful chemical substances into water or carbon dioxide, and apply a transition metal compound-supported titanium oxide suspension or By mixing, antibacterial, fungicidal, deodorizing, air purification, water purification, antifouling effects, and the like can be imparted to the object to be coated or the mixture to be coated. Further, it is known that responsiveness to ultraviolet rays and visible light decreases when ionic impurities such as halogen ions are contained in the transition metal compound-supported titanium oxide suspension.

As a method for removing ionic impurities, a method of removing ionic impurities by solid-liquid separation by adding a titanium oxide suspension to a treatment such as pressurized or reduced pressure filtration or centrifugation using a total filtration method is known (Patent Documents 1 and 2). Etc.). However, in the above method, it has been difficult to sufficiently reduce the content of ionic impurities. In addition, when solid-liquid separation by adding the transition metal compound-supported titanium oxide to the above treatment such as centrifugation, the transition metal compound-supported titanium oxide is condensed and the exposure amount of the highly active surface is reduced, so that sufficient photocatalytic performance cannot be obtained. Was. Further, even if the titanium oxide carrying the transition metal compound once condensed was then subjected to a pulverization treatment or the like and redispersed, a satisfactory photocatalytic activity could not be obtained.

Japanese Patent Application Publication No. Hei 10-158015 Japanese Patent Application Publication No. 62-235215

Accordingly, an object of the present invention is a transition metal compound-supported titanium oxide suspension that includes a transition metal compound-supported titanium oxide crystal, has a very low content of ionic impurities, has excellent responsiveness to visible light, and exhibits excellent photocatalytic performance. To provide.

Another object of the present invention is to provide a transition metal compound-supported titanium oxide obtained by drying the transition metal compound-supported titanium oxide suspension.

In order to solve the above problems, the present inventors intensively studied and found that the transition metal compound-supported titanium oxide crystal having an average aspect ratio of 1.5 or more (hereinafter, sometimes referred to as ``rod phase'') has excellent photocatalytic activity, but centrifugation, etc. Once consolidated by being added to the solid-liquid separation treatment of, the rod-like crystal structure is cut even if it is re-dispersed by pulverization after that, and the photocatalytic activity in the visible light region is remarkably decreased due to the following reasons 1 and 2. Worked.

1. Since the average aspect ratio of the transition metal compound-supported titanium oxide becomes smaller and becomes a shape closer to the spherical shape, the separability between the oxidation reaction field and the reduction reaction field decreases, and the progress of the reverse reaction or side reaction cannot be avoided.

2. When the rod-shaped crystal structure is cut, titanium oxide fragments not carrying a transition metal compound are generated, and the titanium oxide fragments cannot exhibit visible light responsiveness.

And, by adopting a membrane filtration treatment using a cross-flow filtration method instead of a solid-liquid separation treatment such as centrifugal separation as a method for removing ionic impurities, the transition metal compound-carrying titanium oxide crystal is not condensed and the rod-like crystal structure is maintained. It was found that ionic impurities can be efficiently removed in one state, the content of ionic impurities is very low, and a suspension containing a rod-shaped transition metal compound-supported titanium oxide crystal can be obtained. And the suspension thus obtained was excellent in responsiveness to visible light, and it was found that it can exhibit excellent photocatalytic performance. The present invention was completed based on these findings.

That is, the present invention is a suspension of a transition metal compound-supported titanium oxide having an average aspect ratio (long/short axis) of 1.5 or more, obtained by supporting a transition metal compound on crystalline titanium oxide, and contains 4% by weight of the transition metal compound-supported titanium oxide. When contained above, the electrical conductivity of the supernatant of the suspension is 300 μS/cm or less, to provide a transition metal compound-supported titanium oxide suspension.

As the crystalline titanium oxide, a rutile type titanium oxide having a crystal face 110 and a crystal face 111 and/or a rutile type titanium oxide having a crystal face 110, a crystal face 111 and a crystal face (001) is preferable.

The transition metal compound-supported titanium oxide preferably has a specific surface area of 10 m ² /g or more.

In the transition metal compound-supported titanium oxide suspension of the present invention, it is preferable that the pH of the supernatant is 3 or more.

The transition metal compound-supported titanium oxide suspension of the present invention preferably has a viscosity (at 22.5°C) of 5 to 25 mPa·s when the transition metal compound-supported titanium oxide concentration is adjusted to 10% by weight.

It is preferable that the transition metal compound-supported titanium oxide has an average particle diameter of 20 μm or less.

The present invention also provides a transition metal compound-supported titanium oxide obtained by drying the transition metal compound-supported titanium oxide suspension.

The transition metal compound-supported titanium oxide suspension of the present invention contains a transition metal compound-supported titanium oxide crystal having an average aspect ratio of 1.5 or more, and has an extremely low content of ionic impurities. Therefore, it has excellent responsiveness to visible light, absorbs sunlight, light in a normal living space such as incandescent lamps, fluorescent lamps, and LED lights, and decomposes harmful chemical substances into water or carbon dioxide. That is, the transition metal compound-supported titanium oxide suspension of the present invention can be suitably used as a photocatalyst for under LED lighting. In addition, it can be used for various purposes such as antibacterial, fungicidal, deodorization, air purification, water purification, and antifouling. In addition to indoor wallpaper and furniture, environmental purification in public facilities such as homes, hospitals, schools, etc. It can be applied to a wide range such as high functionality.

1 is a schematic diagram showing an example of membrane filtration by a cross flow method.
Fig. 2 is a schematic diagram showing an example of backwashing in membrane filtration by a cross-flow method.
3 is a perspective view of a rod-shaped rutile type titanium oxide having crystal faces 110 and 111, and a rod-shaped rutile type titanium oxide having crystal faces 110, 111, and 001.

[Transition metal compound supported titanium oxide suspension]

The transition metal compound-supported titanium oxide suspension of the present invention is a suspension of transition metal compound-supported titanium oxide having an average aspect ratio (long/short axis) of 1.5 or more, obtained by supporting a transition metal compound on crystalline titanium oxide, wherein the transition metal compound is supported. When titanium oxide is contained in an amount of 4% by weight or more, the electrical conductivity of the supernatant of the suspension is not more than 300 μS/cm.

As a solvent for suspending the transition metal compound-supported titanium oxide, for example, water, alcohol (eg, methanol, ethanol, isopropyl alcohol, etc.), ketones (eg, acetone, methyl ethyl ketone, etc.), and these Hydrophilic solvents, such as a mixture, are mentioned. In the present invention, it is preferable to use water, especially from the viewpoint of excellent safety and ease of handling.

In addition, the average aspect ratio (long/short axis) of the transition metal compound-supported titanium oxide is 1.5 or more, preferably 1.5 to 100, more preferably 1.5 to 50, particularly preferably 1.5 to 20, most preferably 2 to 15. If the average aspect ratio is less than the above range, the separability between the oxidation reaction field and the reduction reaction field is lowered, the reverse reaction or side reaction cannot be avoided, and the photocatalytic performance is lowered, which is not preferable.

In the present invention, the average aspect ratio is a field emission scanning electron microscope (trade name "FE-SEM JSM-6700F", manufactured by Nihon Denshi Co., Ltd., acceleration voltage: 15 kV, WD: about 3 mm, for samples prepared by the following method. , Magnification: 200,000 times) to randomly observe the crystal particles and extract three representative locations, and out of the entire extracted SEM images, they are not extremely large or small in appearance, and have a clear outline around the average sized particles. 30 particles are extracted, an OHP sheet is taken, and the long diameter (maximum long diameter) and short diameter (orthogonal to the maximum short diameter) using image analysis software (trade name ``WinROOF Version 5.6'', manufactured by Mitani Shoji Co., Ltd.) Width) and averaged their ratios.

<Sample manufacturing method>

1. 20 g of a transition metal compound-supported titanium oxide suspension was dried at 105°C for 1 hour under normal pressure to obtain a transition metal compound-supported titanium oxide (powder).

2. Put a small amount of the obtained powder (about half of the amount with a wooden scaffold size spatula) into a 9 mL glass sample bottle, add 7 mL of ethanol, apply ultrasonic waves with an ultrasonic cleaner for 5 minutes, and disperse the powder in ethanol. The resulting ethanol dispersion is obtained.

3. Take 1 drop of the obtained ethanol dispersion with a glass dropper, drop it on a sample stand for SEM, dry naturally, and then perform platinum evaporation for 30 seconds.

As the crystalline titanium oxide, for example, a rutile type, an anatase type, a brookite type titanium oxide, and the like can be suggested. In the present invention, among others, rutile-type or anatase-type titanium oxide (from the viewpoint of exhibiting a more excellent photocatalytic ability, a rutile-type titanium oxide is more preferred, and particularly preferably, a crystal plane (110)) because a stable crystal plane is exposed. ) And a rutile type titanium oxide having a crystal face 111 and/or a rutile type titanium oxide having a crystal face 110, a crystal face 111 and a crystal face (001) are preferred.

The transition metal compound is supported in the state of, for example, a transition metal ion, a transition metal simple substance, a transition metal salt, a transition metal oxide, a transition metal hydroxide, or a transition metal complex. The supported amount of the transition metal compound is, for example, 50 ppm or more, preferably 100 ppm or more, more preferably 200 ppm or more, particularly preferably 300 ppm or more, and most preferably 500 ppm or more. The upper limit of the supported amount of the transition metal compound is, for example, about 5000 ppm, preferably 3000 ppm, and particularly preferably 2000 ppm. When the amount of the transition metal compound supported is less than the above range, the visible light responsiveness tends to decrease. On the other hand, when the supported amount of the transition metal compound exceeds the above range, the excitation electrons do not act effectively due to reverse electron transfer of the injected electrons or the like, and the photocatalytic performance tends to decrease.

When the transition metal compound is surface-selectively supported on the surface of crystalline titanium oxide, the separation of the reaction field between the oxidation and reduction reactions can be further improved, thereby inhibiting the recombination of the excitation electrons and the holes, thereby preventing the progress of the reverse reaction. It is preferable in that it can be suppressed and the photocatalytic activity can be dramatically improved, and in particular, it is preferable that a transition metal compound is selectively supported on the oxidation reaction surface.

In the present invention, "surface selectively" supported by the transition metal compound means that the amount of the transition metal compound exceeding 50% (preferably 70% or more, particularly preferably 80% or more) is 2 of the crystalline titanium oxide. Among the crystal faces of more than one face, it is not all faces but is supported on a specific face (for example, a specific face or two faces). In addition, the upper limit of the cotton selectivity is 100%. Surface selectivity can be determined by confirming a signal derived from a transition metal compound on each crystal surface using a transmission electron microscope (TEM) or an energy dispersive fluorescence X-ray analyzer (EDX).

As the transition metal compound, any compound having an absorption spectrum in the visible region and capable of injecting electrons into the conduction band in an excited state is preferable. In the present invention, element compounds of groups 3 to 11 of the periodic table are preferable, and among them Elemental compounds of groups 8 to 11, particularly preferably an iron compound or a platinum compound, and most preferably a trivalent iron compound (Fe ³⁺ ). Since the trivalent iron compound (Fe ^{3 +} ) is easily adsorbed on titanium oxide, and the divalent iron compound (Fe ^{2 +} ) has a property that is difficult to be adsorbed, it can be easily supported selectively by using the property. to be.

The specific surface area of the transition metal compound-supported titanium oxide is, for example, 10 m ² /g or more. The lower limit of the specific surface area is preferably 30 m ² /g, more preferably 50 m ² /g, particularly preferably 60 m ² /g, most preferably 70 m ² /g. The upper limit of the specific surface area is, for example, 200 m ² /g, preferably 150 m ² /g, particularly preferably 100 m ² /g.

The specific surface area of the transition metal compound-supported titanium oxide is, for example, 10 to 200 m ² /g, preferably 10 to 150 m ² /g, more preferably 30 to 150 m ² /g, even more preferably 50 to 100 m ² /g, particularly preferably 60 to 100 m ² /g, most preferably 70 to 100 m ² /g. The transition metal compound-supported titanium oxide having a specific surface area in the above range increases the exposure amount of the highly active surface, and thus can exhibit excellent photocatalytic performance.

The specific surface area was obtained by drying 20 g of a transition metal compound-supported titanium oxide suspension under normal pressure at 105° C. for 1 hour to obtain a transition metal compound-supporting titanium oxide (powder), and placing the obtained powder in a measurement cell, and at 100° C. (under vacuum). ) For the sample obtained by degassing for 60 minutes, using a high-speed specific surface area/pore diameter distribution measuring device (trade name “NOVA-1200”, manufactured by Quantachtome.Co), changing the sample under the following conditions and measuring the obtained value twice. to be.

<Specific surface area measurement conditions>

Measuring principle: static method (blank correction type)

Detection method: Relative pressure (ratio of the adsorption equilibrium pressure (P) and saturated vapor pressure (P ₀ ) in the sample cell by a pressure converter) and the amount of adsorbed gas (from the pressure detection by the pressure converter and the detection of the manifold temperature by the thermistor) Calculate the amount of gas injected)

Adsorption gas: nitrogen gas

Cell Size: Small pellet cell (Cell capacity: 1.8cm ³ , Stem outer diameter: 9mm)

Measurement items: 3 points on the adsorption side of P/P ₀ =0.1, 0.2, 0.3

Analysis item: specific surface area by BET multipoint method

Further, the transition metal compound-supported titanium oxide suspension of the present invention contains highly dispersed transition metal compound-supported titanium oxide. The average particle diameter of the transition metal compound-supported titanium oxide is preferably, for example, about 20 μm or less (for example, 1 to 20000 nm), more preferably 20 to 20000 nm, particularly preferably 50 to 5000 nm, and most preferably Is from 100 to 1500 nm. The transition metal compound-supported titanium oxide having an average particle diameter in the above range increases the amount of exposure on the highly active surface, and thus can exhibit excellent photocatalytic performance.

The average particle diameter is a value obtained using a laser diffraction particle size distribution measuring apparatus (trade name "SALD-2000J", manufactured by Shimadzu Corporation) for a sample adjusted by the following method. In addition, the average particle diameter in the present invention is not an average value of the size of the smallest particles (primary particle diameter) present, but is an average value of the size of all particles including secondary particles generated by aggregation or association.

<Sample Manufacturing Method>

1. The transition metal compound-supported titanium oxide suspension is treated with a high-speed centrifugal separator (trade name "HP-301", manufactured by Beckman Coulter) (400,000 G for 1 hour) to collect a supernatant, which is used for dilution of the sample.

2. A transition metal compound-supported titanium oxide suspension is diluted with the supernatant to a concentration in the range of 0.05 to 0.08 absorbance, and put in a measuring cell to measure the particle size distribution. The relative refractive index is set to 2.750 rutile type titanium oxide.

In addition, for the dilution in the above 2, instead of the supernatant liquid described in the above 1, a permeate (electric conductivity of 300 μm or less) obtained by membrane filtration by a cross flow method may be used.

In addition, when the transition metal compound-supported titanium oxide suspension of the present invention is adjusted to contain 4% by weight or more of the transition metal compound-supported titanium oxide, the electrical conductivity of the supernatant liquid is 300 μS/cm or less (for example, 0.5 to 300 μS/ cm, preferably 0.5 to 250 μS/cm, particularly preferably 1 to 200 μS/cm).

The transition metal compound-supported titanium oxide suspension of the present invention has a very low content of ionic impurities since the supernatant has an electrical conductivity in the above range (the content of ionic impurities is, for example, about 0.01 to 5000 ppm, preferably 1 to 3000 ppm). , Has excellent light response.

In addition, the pH of the supernatant of the transition metal compound-supported titanium oxide suspension of the present invention is preferably 3 or more, more preferably 3 to 7, particularly preferably 3 to 6, and most preferably 3 to 5.5. When the pH of the supernatant is less than the above range, the supported transition metal compound is liable to elute, and the visible light responsiveness tends to decrease. The pH of the supernatant can be adjusted, for example, by neutralization with ammonia or the like, or by adjusting the degree of washing of the membrane filtration by a cross flow method.

In the present invention, the supernatant of the transition metal compound-supported titanium oxide suspension is a supernatant obtained by separating the transition metal compound-supported titanium oxide suspension by a high-speed centrifugal separator (centrifugal effect: 40,000 G for 60 minutes).

In addition, since the transition metal compound-supported titanium oxide suspension of the present invention contains the transition metal compound-supported titanium oxide having the above average particle diameter, the viscosity is high. For example, the transition metal compound-supported titanium oxide concentration is 10% by weight. When adjusted, its viscosity (at 22.5°C) is, for example, 5 to 25 mPa·s, preferably 5 to 15 mPa·s, particularly preferably 5 to 10 mPa·s, most preferably 6 to 10 mPa·s. to be. Adjustment of the concentration of the transition metal compound-supported titanium oxide suspension is accomplished by dilution or concentration with a solvent [a method of distilling off the solvent under reduced pressure, a method of concentrating a membrane (for example, an ultrafiltration method using a hollow fiber type filtration membrane or a tubular membrane)]. Can be done.

In addition, the viscosity of the transition metal compound-supported titanium oxide suspension of the present invention was adjusted to 22.5°C in a 110 mL glass sample bottle using a rotational viscometer (B type viscometer, TOKIMEC BM type, manufactured by Tokyo Keiki Co., Ltd.) 100 mL (liquid height: 90 mm) was added, and the value was measured with rotor No. 1 (60 rpm).

The transition metal compound-supported titanium oxide suspension of the present invention contains the transition metal compound-supported titanium oxide having the above average particle diameter and has the above viscosity, so it has very excellent dispersion stability, and is allowed to stand for one week after adjustment (25 Even under conditions of C and 60% RH), high dispersibility can be maintained without sedimentation.

Since the transition metal compound-supported titanium oxide suspension of the present invention has the above characteristics, it can exhibit very excellent light responsiveness. That is, it has responsiveness to light in a wide wavelength range from the ultraviolet region to the visible region. Therefore, it absorbs sunlight, incandescent lamps, fluorescent lamps, and light in ordinary living spaces such as LEDs, exhibits high catalytic activity, and can decompose harmful chemicals into water or carbon dioxide, and is antibacterial (bacteria, actinomycetes, Sterilization and algae such as fungi and seaweed), fungicide, deodorization (e.g., deodorization of sulfur-containing substances such as ammonia, amines, methylmercaptan, hydrogen sulfide, odor gases such as acetic acid, aldehydes, and ethylene), air purification It can exert various effects such as water purification and antifouling. In addition, the transition metal compound-supported titanium oxide suspension of the present invention is applied or mixed in a mixed state of a binder, a solvent, a dispersant, a thickener, a surfactant, etc., as necessary, to impart the above effect to the object to be coated or the mixture to be coated. I can.

Examples of the object to be coated and the mixture of the transition metal compound-supported titanium oxide suspension of the present invention include, for example, building materials, building exteriors, building interiors, building paints, walls, wallpaper, floors, window frames, window glass, crystallized glass, glass, Insect screens, rain gutters, solar radiation sheets, mailbox boxes, structural members, packaging materials, display boards, traffic signs, road sign reflectors, display panels, display filters, road marking materials, road veneers, fences, gates, tunnels Road lighting devices, sound insulation walls, guard rails, tunnel interiors, road mirrors, vinyl house ceilings, bridges, bridges, fall prevention fences, automobiles, trains, ships, interior and exterior coatings, vehicle wheels, rolling stock spheres, vehicles Exterior/dustproof cover/painting of parts, machinery and articles, various display devices, advertisement towers, insulators, solar panels, solar cell covers, solar water heater heat collection covers, fuel cells, optical fibers, covers for vehicle lighting, fishing nets, ropes, Hose, ship bottom material, insulation, shoes, bags, blinds, curtains, water curtains, screens, sliding doors, plastic sliding doors, inserts, synthetic leather, tablecloths, clothes, raincoats, stationery, books, notebooks, paper, cardboard, vehicles and appliances Various plastic bodies such as, toys, sports equipment, musical instruments, fishing tools, in-vehicle accessories, plastic containers, cards, tents, timber, pillars, ceiling boards, and other building materials, furniture, printed plywood, interior boards, artificial flowers, Houseplants, artificial plants, swimming pools, baths, rivers, seas, factory drains, living drains, groundwater, ponds, artificial rivers, fillers for water treatment, mirrors, wash bowls, tiles, tile joints, bathtubs, bathroom members, Floor finishing materials for toilets, hospital interior materials for preventing infection in the hospital, multifunctional materials for ceramic industry, glazing, interior and exterior walls of refrigerators, bases, kitchen panels, dishwashers, ranges, heated cooking containers, ventilation devices, air conditioning, heat exchangers, various filters, toilets, Fiber, nonwoven fabric, mask, clothing, bedding, hat, helmet, doormat, carpet, medical equipment, food, fork, knife, spoon, tableware, packaging material, food wrap, food preservation container, dish washing device, water purifier, daily use Legging equipment, melamine veneer, carpet, lighting equipment, lighting equipment, lighting lamps, lighting umbrellas, black lights, antifouling paints, filters, various films and sheets such as agricultural vinyl films, super-hydrophilic films, grass sheets, electronic parts, electrical products , Electric equipment, corona charger, plasma generator, ozone generator, exposure device, humidifier, hand dryer, scalp care device, electric vacuum cleaner, telephone, portable terminal, portable device, touch panel display, organic EL device and display panel, Inkjet recording device, air cleaner, refrigeration device, dust collector, ornaments, mechanical parts, magnetic disk, showcase, instrument cover glass, camera, eyeglasses, camera lens, eyeglass lens, contact lens, whitening agent, dental/oral material , Tooth bleaching material, implants, oral instruments, cosmetics, and shampoos.

(Method for producing a transition metal compound-supported titanium oxide suspension)

The transition metal compound-supported titanium oxide suspension of the present invention can be prepared, for example, by adding a coarse transition metal compound-supported titanium oxide suspension obtained by impregnating a transition metal compound into a crystalline titanium oxide suspension to membrane filtration by a cross flow method. I can. After addition to the cross-flow membrane filtration, treatments such as dilution and concentration may be performed.

(Membrane filtration by cross flow method)

The cross-flow membrane filtration is a method in which water to be treated is flowed parallel to the surface of the filtration membrane, and a part of the water to be treated is filtered from the side of the flow of the water to be treated while preventing contamination of the filtration membrane due to the deposition of filtration residue. to be. By adding the coarse transition metal compound-supported titanium oxide suspension to the membrane filtration by a cross-flow method, ionic impurities can be efficiently removed without forming compacted filtration residue on the surface of the filtration membrane, and the transition metal compound-supported titanium oxide While maintaining the crystal structure of, the content of ionic impurities can be reduced to a very low level.

The concentration of the coarse transition metal compound-supported titanium oxide suspension added to the cross-flow membrane filtration is, for example, about 0.1 to 40% by weight (preferably 0.1 to 30% by weight). When the concentration of the coarse transition metal compound-supported titanium oxide suspension is outside the above range, the removal efficiency of ionic impurities tends to decrease. In addition, when the concentration of the coarse transition metal compound-supported titanium oxide suspension exceeds the above range, the viscosity becomes too high and fouling (clogging) is liable.

When a coarse transition metal compound-supported titanium oxide suspension is added to the membrane filtration by a cross-flow method, ionic impurities are separated and removed together with the permeate, and a concentrated transition metal compound-supported titanium oxide suspension is obtained.

The concentration ratio is preferably adjusted to about 1 to 400 times (in particular, 1 to 20 times, particularly 1 to 10 times). When the concentration ratio exceeds the above range, it becomes difficult to suppress the deposition of substances adhered to the film surface, and thus it tends to become difficult to prevent consolidation of the transition metal compound-supported titanium oxide. In addition, fouling (clogging) occurs in the filtration membrane due to deposition of adherent substances on the membrane surface, so that the membrane life is liable to decrease, and it is necessary to frequently perform backwashing, or filtration treatment may become impossible to operate. There is also a tendency that the filtration rate is liable to decrease, for example. On the other hand, when the concentration ratio is less than the above range, the separation efficiency of ionic impurities decreases, and the amount of washing water used tends to increase.

The concentration ratio can be adjusted, for example, by controlling the filtration pressure, the film surface linear velocity (cross flow velocity) of the coarse transition metal compound-supported titanium oxide suspension, and the like. The filtration pressure is, for example, about 0.001 to 5.0 MPa, preferably 0.005 to 3 MPa, particularly preferably 0.01 to 2.0 MPa.

In addition, as the film surface linear velocity of the feed liquid containing the coarse transition metal compound-supported titanium oxide suspension increases, deposition of adherent substances to the film surface is suppressed, and a high filtration flow rate (flux) is obtained. The film surface linear velocity (cross flow velocity) is, for example, 0.02 m/s or more and less than 3 m/s, and preferably 0.05 m/s or more and less than 1.5 m/s.

The transition metal compound-supported titanium oxide suspension concentrated through membrane filtration by a cross-flow method is diluted with water so that the concentration of the transition metal compound-supported titanium oxide suspension is within the above range, and then membrane filtered by a cross-flow method. It is desirable to repeat the operation. Thereby, the load on the filtration membrane due to fouling (clogging) or the like can be reduced, and the content of ionic impurities can be very low while improving the life of the filtration membrane.

1 is a schematic diagram showing an example of membrane filtration by a cross-flow method (circulating membrane filtration method) of a coarse transition metal compound-supported titanium oxide suspension. The feed solution containing the coarse transition metal compound-supported titanium oxide suspension introduced into the input tank is membrane-filtered by a cross-flow filtration method to obtain a concentrated transition metal compound-supported titanium oxide suspension (concentrate). The concentrated transition metal compound-supported titanium oxide suspension is circulated to the input tank again, diluted with water for dilution (water for dilution), and filtered through a cross flow filtration method.

As a filtration membrane used for membrane filtration by a cross-flow method, an ultrafiltration membrane, a microfiltration membrane, a nano filter, a reverse osmosis membrane, etc. are mentioned, for example. In the present invention, it is preferable to use an ultrafiltration membrane from the viewpoint of excellent separation performance, among others.

As an ultrafiltration membrane, substances having an average pore diameter of about 1 to 20 nm (preferably 1 to 10 nm), a molecular weight of about 1000 to 300000 (preferably 1000 to 50000), and an average particle diameter of about 1 to 10 nm can be separated. It is desirable to use what is available.

As the membrane shape of the ultrafiltration membrane, for example, any of a hollow fiber type filtration membrane, a tubular membrane, a spiral membrane, a flat membrane, etc. may be used, but since backwashing can be performed relatively easily, a hollow fiber type filtration membrane or a tubular membrane is used. It is desirable to do.

The inner diameter of the hollow fiber membrane in the hollow fiber type filtration membrane is about 0.1 to 2.0 mm (preferably 0.5 to 1.5 mm) from the viewpoint of preventing clogging of contaminants and improving the filling rate of the hollow fiber to the membrane module.

As the material of the filtration membrane, for example, cellulose acetate, polyacrylonitrile, polysulfone, polyethersulfone (PES), polyacrylonitrile, aromatic polyamide, polyvinylidene fluoride, polyvinyl chloride, polyethylene, polypropylene, General materials, such as polyimide and ceramic, are mentioned. In the present invention, cellulose acetate, polysulfone, polyethersulfone (PES), polyacrylonitrile, and aromatic polyamide are particularly preferred.

In the case of using a hollow fiber type filtration membrane, as a method of flowing a coarse transition metal compound-supported titanium oxide suspension (filtration method), a supply liquid containing a rough transition metal compound-supported titanium oxide suspension is flowed into the inner side (the inner side of the hollow fiber membrane), and the outer side (the hollow fiber The permeated water flows toward the outside of the desert) (internal pressure filtration method), and vice versa, a supply solution containing a coarse transition metal compound-supported titanium oxide suspension flows to the outside and the permeated water flows toward the inside (external pressure filtration method). I can. In the present invention, among others, an internal pressure filtration method is preferred from the viewpoint of being able to rapidly maintain the flow velocity on the membrane surface.

In membrane filtration by the cross flow method, intermittent backwashing with washing water is performed on the filtration membrane in order to reduce the burden on the filtration membrane by preventing deposition of adherent substances on the surface of the filtration membrane, and to perform a long-term membrane filtration operation. It is desirable to carry out. It is preferable to perform backwashing at a predetermined cycle while controlling the pressure and flow rate.

The backwashing pressure is, for example, about 0.01 to 3.0 MPa, preferably 0.01 to 2.0 MPa, particularly preferably 0.01 to 1.0 MPa, most preferably 0.01 to 0.5 MPa, and more preferably 0.05 to 0.5 MPa. Further, as defined backwash flow rate, for example from 0.01 to 10kg / mim, preferably from 0.05 to 5kg / mim, in particular preferably from 0.1 to 5kg / mim [or, for example, a 1 × 10 ^-7 to 2 × 10 ^{- It is about 4} m/sec, preferably 8×10 ^-7 to 9×10 ^-5 m/sec, particularly preferably 1×10 ^-6 to 9×10 ^-5 m/sec]. The frequency of backwashing is preferably performed about once every 0.5 to 3 hours, for example. The time for backwashing is preferably about 0.5 to 10 minutes.

In addition, it is preferable to use water (eg, purified water, distilled water, pure water, ion-exchanged water, etc.) as the washing water used for backwashing. In addition, it is preferable to reuse the washing water that has just passed through backwashing as water for dilution of the concentrated transition metal compound-supported titanium oxide suspension (see FIG. 2).

In the membrane filtration by the cross-flow method, the electrical conductivity of the permeate will be 300 μS/cm or less (e.g. 0.5 to 300 μS/cm, preferably 0.5 to 250 μS/cm, particularly preferably 1 to 200 μS/cm). It is preferable to perform repeatedly until. When membrane filtration by the cross flow method is terminated before the electrical conductivity of the permeate reaches the above range, removal of ionic impurities (especially iron ions and chlorine ions) may become insufficient.

(Method for producing a tough transition metal compound-supported titanium oxide suspension)

Here, the coarse transition metal compound-supported titanium oxide suspension added to the cross-flow membrane filtration is obtained, for example, by adding and impregnating a solution containing the transition metal compound to the crystalline titanium oxide suspension.

The crystalline titanium oxide suspension is not particularly limited and can be prepared by a known and common method. For example, the rod-shaped rutile type titanium oxide suspension is prepared by using a titanium compound in an aqueous medium (for example, water or water and a water-soluble organic solvent. (A mixed solution of)) by hydrothermal treatment [for example, 100 to 220°C, 2 to 48 hours (preferably 2 to 15 hours, particularly preferably 5 to 15 hours)]. In addition, adding and/or stirring a halide during hydrothermal treatment (eg, stirring required power (Pv value): about 0.1 to 1500 W/m ³ ) is preferable because the size and surface area of the obtained particles can be adjusted.

Examples of the titanium compound include a trivalent titanium compound and a tetravalent titanium compound. Examples of the trivalent titanium compound include titanium trihalide such as titanium trichloride and titanium tribromide. As the trivalent titanium compound in the present invention, titanium trichloride (TiCl ₃ ) is preferable from the viewpoint of being inexpensive and easy to obtain.

In addition, the tetravalent titanium compound in the present invention includes, for example, a compound represented by the following formula (1).

Ti(OR) _t X _{4 - t} (1)

(In the formula, R represents a hydrocarbon group, X represents a halogen atom. t represents an integer of 0 to 3)

Examples of the hydrocarbon group in R in formula (1) include C _1-4 aliphatic hydrocarbon groups such as methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, and tert-butyl. .

Examples of the halogen atom in X in formula (1) include chlorine, bromine, and iodine.

Examples of such a tetravalent titanium compound include tetrahalogenated titanium such as TiCl ₄ , TiBr ₄ , and TiI ₄ ; Tree of Ti(OCH ₃ )Cl ₃ , Ti(OC ₂ H ₅ )Cl ₃ , Ti(OC ₄ H ₉ )Cl ₃ , Ti(OC ₂ H ₅ )Br ₃ , Ti(OC ₄ H ₉ )Br ₃ Halogenated alkoxy titanium; Dihalogenated dialkoxy titanium, such as Ti(OCH ₃ ) ₂ Cl ₂ , Ti(OC ₂ H ₅ ) ₂ Cl ₂ , Ti(OC ₄ H ₉ ) ₂ Cl ₂ , Ti(OC ₂ H ₅ ) ₂ Br ₂ ; Monohalogenated trialkoxy titanium, such as Ti(OCH ₃ ) ₃ Cl, Ti(OC ₂ H ₅ ) ₃ Cl, Ti(OC ₄ H ₉ ) ₃ Cl, and Ti(OC ₂ H ₅ ) ₃ Br, etc. are mentioned. As the tetravalent titanium compound in the present invention, since it is inexpensive and easy to obtain, titanium tetrahalide is preferable, and titanium tetrachloride (TiCl ₄ ) is particularly preferable.

The rod-like rutile type titanium oxide obtained by hydrothermal treatment can be purified by well-known and common methods, such as filtration, concentration, distillation, extraction, crystallization, recrystallization, column chromatography, or a combination of these. In the present invention, inter alia, cross-flow membrane filtration can reduce the content of ionic impurities while maintaining the crystal structure of titanium oxide, and there is no need to perform pulverization treatment, so that the transition metal compound is supported as it is. It is preferable because it can provide for a process and can obtain titanium oxide which can support a transition metal compound highly.

The membrane filtration by the cross flow method can be performed in the same manner as the membrane filtration by the cross flow method of the coarse transition metal compound-supported titanium oxide suspension, and the permeate has a pH of 1 or more (preferably 1 to 7, Particularly preferably 2 to 6, most preferably 2 to 5.5). If membrane filtration by the cross flow method is terminated before the pH of the permeate reaches the above range, removal of ionic impurities (especially, hydrogen ions, chlorine ions, and titanium ions) becomes insufficient, making it difficult to support transition metal compounds. There is a case of loss.

By impregnating the transition metal compound into the crystalline titanium oxide suspension obtained by the above method, a rough transition metal compound-supported titanium oxide suspension can be obtained. For example, a coarse transition metal compound-supported titanium oxide suspension carrying a trivalent iron compound (Fe ^{3 +} ) as a transition metal compound is prepared in a crystalline titanium oxide suspension with iron (III) nitrate, iron (III) sulfate, and iron chloride ( III) It is obtained by adding and impregnating a solution containing the like.

The concentration of the solution containing the transition metal compound is, for example, about 0.1 to 40% by weight, preferably 1 to 40% by weight. In addition, the impregnation time is, for example, about 1 minute to 24 hours, preferably 5 minutes to 10 hours.

And, in the present invention, irradiation of excitation light when impregnating the transition metal compound does not require large-scale facilities, etc., is easily and efficiently, and selectively supports the transition metal compound on a specific surface of crystalline titanium oxide. It is preferable in that it can be done. When excitation light is irradiated, electrons in the valence band of crystalline titanium oxide are excited in the conduction band, holes in the valence band, and excitation electrons in the conduction band are generated, and these are diffused on the surface of the particle, and excitation electrons and holes according to the characteristics of each crystal plane This is separated to form an oxidation reaction surface and a reduction reaction surface. In this state, as a transition metal compound, for example, when impregnating with a trivalent iron compound, the trivalent iron compound (Fe ^{3 +} ) is adsorbed on the oxidation reaction surface, but in the reduction reaction surface, the trivalent iron compound (Fe ^{3 +} ) Silver is reduced to a divalent iron compound (Fe ^{2 +} ), and the divalent iron compound (Fe ^{2 +} ) has a property that is difficult to be adsorbed, so it is eluted in the solution, and as a result, an iron compound (Fe ^{3 +} ) It is possible to obtain a supported iron compound-supported titanium oxide.

The excitation light is light having an energy equal to or greater than the band gap energy (for example, ultraviolet rays). As the excitation light irradiation means, for example, a medium-high pressure mercury lamp, a UV laser, a UV-LED, an ultraviolet exposure apparatus having a light source that efficiently generates ultraviolet rays, such as a black light, can be used. The irradiation amount of excitation light is, for example, about 0.1 to 300 mW/cm ² , and preferably 0.5 to 100 mW/cm ² .

Moreover, in this invention, it is preferable to add a sacrificial agent at the time of impregnation. By adding a sacrificial agent, a transition metal compound can be supported on a specific crystal plane of crystalline titanium oxide with a high selectivity. As the sacrificial agent, it is preferable to use an organic compound that itself easily emits electrons, and examples thereof include alcohols such as methanol and ethanol; Carboxylic acids such as acetic acid; And amines such as ethylenediamine tetraacetic acid (EDTA) and triethanolamine (TEA).

The addition amount of the sacrificial agent can be appropriately adjusted, and is, for example, about 0.5 to 20.0% by weight, preferably about 1.0 to 5.0% by weight, of the suspension of crystalline titanium oxide. The sacrificial agent may be used in excess.

[Transition metal compound supported titanium oxide]

As for the transition metal compound-supported titanium oxide of the present invention, the transition metal compound-supported titanium oxide suspension is dried [for example, F.V. It is obtained under (1.3kPa [A] or less) about 15 hours at 60°C, or about 1 hour at 105°C under normal pressure (atmospheric pressure).

The transition metal compound-supported titanium oxide of the present invention has excellent visible light responsiveness, and exhibits excellent photocatalytic activity by light irradiation to decompose harmful chemicals into water or carbon dioxide, thereby antibacterial, fungicidal, deodorizing, air purification, water quality. It can exert various effects such as purification and antifouling.

For example, the amount of CO ₂ generated when toluene is oxidized using the transition metal compound-supported titanium oxide (200 mg) is, for example, 300 ppm or more. Further, the amount of CO ₂ generated when methanol is oxidized is, for example, 500 ppm or more, preferably 600 ppm or more, more preferably 700 ppm or more, and particularly preferably 750 ppm or more.

In addition, a method of measuring the amount of CO ₂ generated when the toluene is oxidized is as follows.

200 mg of titanium oxide carrying a transition metal compound was spread out on a glass plate and placed in a reaction vessel (Tedrabag, material: vinyl fluoride resin), and 125 mL of 100 ppm of toluene gas was blown into the reaction vessel. After the adsorption of toluene gas to the transition metal compound-supported titanium oxide reached equilibrium, light irradiation (LED, light intensity: 2.5 W/cm ² , light wavelength: 455 nm) was performed at room temperature (25° C.), and from the start of light irradiation The amount of CO ₂ produced after 24 hours is measured.

In addition, the method of measuring the amount of CO ₂ generated when methanol is oxidized is as follows.

200 mg of titanium oxide supported by a transition metal compound was spread on a glass plate and placed in a reaction vessel (Tedrabag, material: vinyl fluoride resin), and 125 mL of 800 ppm methanol gas was blown into the reaction vessel. After the adsorption of methanol gas to the transition metal compound-supported titanium oxide reached equilibrium, light irradiation (LED, light intensity: 2.5 W/m ² , light wavelength: 455 nm) was performed at room temperature (25°C), and from the start of light irradiation The amount of CO ₂ produced after 24 hours is measured.

Example

Hereinafter, the present invention will be described in more detail by examples, but the present invention is not limited by these examples.

Example 1

(Preparation of coarse titanium oxide suspension)

At room temperature (25°C), a titanium tetrachloride aqueous solution (Ti concentration: 16.5% by weight±0.5% by weight, chlorine ion concentration: 31% by weight±2% by weight, manufactured by Doho Titanium Co., Ltd.) is added so that the Ti concentration becomes 5.6% by weight. It was diluted with pure water. 5650 g of the diluted titanium tetrachloride aqueous solution was placed in a 10 L tantalum lined autoclave and sealed. Using the heat medium, the temperature in the autoclave was raised to 140°C over 2 hours. Thereafter, stirring at a required power (Pv value) of 1360 W/m ³ , temperature: 140°C, pressure: maintained for 5 hours under the condition of vapor pressure at that temperature, and then cooled the heat medium to keep the autoclave up to 40°C. Cooled. Thereafter, the autoclave was cooled by cooling the heat medium after holding again for 5 hours under conditions of temperature: 140°C, pressure: vapor pressure at that temperature. It was confirmed that the temperature in the autoclave became 40°C or less, and 5650 g of the coarse titanium oxide suspension (1) was taken out.

(Membrane filtration treatment by cross flow method (1))

The obtained coarse titanium oxide suspension (1) was diluted 3 times with pure water, and a hollow fiber type ultrafiltration membrane (brand name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, manufactured by Daisen Membrane Systems Co., Ltd. ), at room temperature (25° C.) and a filtration pressure of 0.02 MPa, while adding pure water in an amount equal to the amount of permeated liquid, a cross-flow method was performed. The concentrate obtained through the filtration treatment was circulated again to the input tank, and was repeatedly added to the filtration treatment until the pH of the permeate reached 4.0. In addition, pH was measured using a pH test paper. In the meantime, backwashing was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank. Thereafter, the addition of pure water was stopped and the titanium oxide concentration was concentrated to obtain a titanium oxide suspension (1-1). The titanium oxide suspension (1-1) was dried for 1 hour at 105°C under normal pressure, and rod-shaped rutile titanium oxide having a crystal plane (110) and a crystal plane (111), and a crystal plane (110), a crystal plane (111) and a crystal plane 525 g of titanium oxide (1), which is a mixture of rod-shaped rutile type titanium oxide having (001), was obtained (see Fig. 3). The photocatalytic ability of the obtained titanium oxide (1) evaluated by the toluene oxidation method using the following ultraviolet rays was 625 ppm (decomposition rate: 94%).

(Iron compound supporting treatment)

To the titanium oxide suspension (1-1) obtained above, 7.5 g of an aqueous iron chloride solution (35% by weight) was added, followed by stirring at room temperature (25°C) for 30 minutes. Thereafter, 95 g of methanol (1.7% by weight of the titanium oxide suspension) was added, and ultraviolet (UV) was irradiated for 3 hours using a 100W high-pressure mercury lamp (UV irradiation amount: 5mW/cm ² ), and coarse iron compound supported oxidation A titanium suspension (1) was obtained.

(Membrane filtration treatment by cross flow method (2))

A coarse iron compound-supported titanium oxide suspension (1) was diluted three times with pure water, and a hollow fiber type ultrafiltration membrane (brand name ``FS03-FC-FUS03C1'', material: PES, nominal molecular weight: 30,000, Daisen Membrane Systems Co., Ltd. ) Agent), at room temperature (25°C) and a filtration pressure of 0.02 MPa, while adding pure water in an amount equal to the amount of permeated liquid, filtration was performed by a cross flow method. The concentrate obtained through the filtration treatment was circulated again in the input tank, and repeatedly added to the filtration treatment until the electrical conductivity of the permeated liquid became 200 µS/cm. In the meantime, backwashing was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank. Thereafter, the addition of pure water was stopped, the iron compound-supported titanium oxide concentration was concentrated, and the iron compound-supported titanium oxide suspension (1-1) (average particle diameter: 1000 nm, iron compound-supported titanium oxide concentration: 15% by weight, supernatant Electrical conductivity of: 200 μS/cm, pH of the supernatant: 4.9) was obtained. In the meantime, backwashing was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank.

Then, it dried at 105 degreeC for 1 hour under normal pressure, and obtained the iron compound-supported titanium oxide (1) (specific surface area: 77 m ² /g, average aspect ratio: 6). The content of the iron compound in the obtained iron compound-supported titanium oxide (1) was 800 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 734 ppm. In addition, the obtained iron compound-supported titanium oxide (1) has a crystal plane (110) and a crystal plane (111), and a rod-shaped rutile type titanium oxide in which an iron compound is supported only on the crystal plane (111), a crystal plane (110), and a crystal plane It was a mixture of rod-like rutile type titanium oxide having (111) and crystal plane (001), and carrying an iron compound on the crystal plane (001) and crystal plane (111).

Example 2

(Preparation of coarse titanium oxide suspension)

At room temperature (25°C), a titanium tetrachloride aqueous solution (Ti concentration: 16.5% by weight±0.5% by weight, chlorine ion concentration: 31% by weight±2% by weight, manufactured by Doho Titanium Co., Ltd.) is added so that the Ti concentration becomes 5.6% by weight. It was diluted with pure water. 5650 g of the diluted titanium tetrachloride aqueous solution was placed in a 10 L tantalum lined autoclave and sealed. Using the heat medium, the temperature in the autoclave was raised to 140°C over 2 hours. Then, the autoclave was cooled by cooling the heat medium after holding for 10 hours under conditions of temperature: 140°C and pressure: vapor pressure at that temperature while stirring at 220 W/m ³ of power required for stirring (Pv value). It was confirmed that the temperature in the autoclave became 40°C or less, and 5650 g of the coarse titanium oxide suspension (2) was taken out.

(Membrane filtration treatment by cross flow method (1))

The obtained coarse titanium oxide suspension (2) was diluted 3 times with pure water, and a hollow fiber type ultrafiltration membrane (brand name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, manufactured by Daisen Membrane Systems Co., Ltd. ), at room temperature (25° C.) and a filtration pressure of 0.02 MPa, while adding pure water in an amount equal to the amount of permeated liquid, a cross-flow method was performed. The concentrate obtained through the filtration treatment was circulated again in the input tank, and was repeatedly added to the filtration treatment until the pH of the permeate reached 4.0. In the meantime, backwashing was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank. After that, the addition of pure water was stopped and the titanium oxide concentration was concentrated to obtain a titanium oxide suspension (2-1). A titanium oxide suspension (2-1) was dried for 1 hour at 105°C under normal pressure, and rod-shaped rutile titanium oxide having a crystal face (110) and a crystal face (111), and a crystal face (110), a crystal face (111) and a crystal face 533 g of titanium oxide (2), which is a mixture of rod-like rutile type titanium oxide having (001), was obtained. The photocatalytic ability of the obtained titanium oxide (2) evaluated by the toluene oxidation method by the following ultraviolet rays was 647 ppm (decomposition rate: 95%).

(Iron compound supporting treatment)

7.5 g of an aqueous iron chloride solution (35% by weight) was added to the titanium oxide suspension (2-1) obtained above, followed by stirring at room temperature (25°C) for 30 minutes. Thereafter, 95 g of methanol (1.7% by weight of the titanium oxide suspension) was added, and ultraviolet (UV) was irradiated for 3 hours using a 100W high-pressure mercury lamp (UV irradiation amount: 5mW/cm ² ), and coarse iron compound supported oxidation A titanium suspension (2) was obtained.

(Membrane filtration treatment by cross flow method (2))

A coarse iron compound-supported titanium oxide suspension (2) was diluted twice with pure water, and a hollow fiber type ultrafiltration membrane (brand name ``FS03-FC-FUS03C1'', material: PES, nominal molecular weight: 30,000, Daisen Membrane Systems Co., Ltd. ) Agent), at room temperature (25°C) and a filtration pressure of 0.02 MPa, while adding pure water in an amount equal to the amount of permeated liquid, filtration was performed by a cross flow method. The concentrate obtained through the filtration treatment was circulated again in the input tank, and repeatedly added to the filtration treatment until the electrical conductivity of the permeated liquid became 200 µS/cm. In the meantime, backwashing was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank. Thereafter, the addition of pure water was stopped, the iron compound-supported titanium oxide concentration was concentrated, and the iron compound-supported titanium oxide suspension (2-1) (average particle diameter: 880 nm, the iron compound-supported titanium oxide concentration: 10% by weight, the supernatant Electrical conductivity: 200 μS/cm, pH of the supernatant liquid: 4.9, viscosity (at 22.5° C.): 7 mpa·s) were obtained. In the meantime, backwashing was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank.

Then, it dried at 105 degreeC for 1 hour under normal pressure, and obtained 530 g of crystalline iron compound-supported titanium oxide (2) (specific surface area: 78 m ² /g, average aspect ratio: 3). The content of the iron compound in the obtained iron compound-supported titanium oxide (2) was 830 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 775 ppm.

Example 3

In the same manner as in Example 2, except that in the above (filtration treatment (2) by the cross-flow method), the permeate was repeated until the electrical conductivity of the permeate became 150 μS/cm, the iron compound-supported titanium oxide suspension (3- 1) (average particle diameter: 550 nm, iron compound supported titanium oxide concentration: 10% by weight, electrical conductivity of the supernatant: 150 μS/cm, pH of the supernatant: 4.9, viscosity (at 22.5°C): 6.9 mPa·s) to obtain , 530 g of crystalline iron compound-supported titanium oxide (3) (specific surface area: 78.5 m ² /g, average aspect ratio: 3). The content of the iron compound in the obtained iron compound-supported titanium oxide (3) was 890 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 795 ppm.

Example 4

In the same manner as in Example 2, except that in the above (filtration treatment (2) by the cross-flow method), the permeate was repeated until the electrical conductivity of the permeate reached 100 μS/cm, the iron compound-supported titanium oxide suspension (4- 1) (Average particle diameter: 400 nm, iron compound supported titanium oxide concentration: 10% by weight, electrical conductivity of the supernatant: 100 μS/cm, pH of the supernatant: 5.2, viscosity (at 22.5°C): 6.8 mPa·s) to obtain , 530 g of crystalline iron compound-supported titanium oxide (4) (specific surface area: 79 m ² /g, average aspect ratio: 3). The content of the iron compound in the obtained iron compound-supported titanium oxide (4) was 950 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 800 ppm.

Example 5

In the same manner as in Example 2, except that in the above (filtration treatment (2) by the cross-flow method), the electrical conductivity of the permeate was repeated until 50 μS/cm, the iron compound-supported titanium oxide suspension (5- 1) (average particle diameter: 300 nm, iron compound supported titanium oxide concentration: 10% by weight, electrical conductivity of the supernatant: 50 μS/cm, pH of the supernatant: 5.2, viscosity (at 22.5°C): 6.6 mPa·s) to obtain , 530 g of crystalline iron compound-supported titanium oxide (5) (specific surface area: 80 m ² /g, average aspect ratio: 3). The content of the iron compound in the obtained iron compound-supported titanium oxide (5) was 1200 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 800 ppm.

Example 6

In the above (iron compound supporting treatment), a rough iron compound-supporting titanium oxide suspension (6) was obtained in the same manner as in Example 2 except that the amount of iron chloride aqueous solution (35% by weight) was changed from 7.5 g to 6.5 g. , Iron compound supported titanium oxide suspension (6-1) (average particle diameter: 840 nm, iron compound supported titanium oxide concentration: 10% by weight, electrical conductivity of the supernatant: 200 μS/cm, pH of the supernatant: 4.9) was obtained, Iron compound supported titanium oxide (6) (specific surface area: 76 m ² /g, average aspect ratio: 3) 530 g was obtained. The content of the iron compound in the obtained iron compound-supported titanium oxide (6) was 700 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 780 ppm.

Example 7

In the above (iron compound supporting treatment), a rough iron compound-supporting titanium oxide suspension (7) was obtained in the same manner as in Example 2 except that the amount of iron chloride aqueous solution (35% by weight) was changed from 7.5 g to 15.0 g. , Iron compound supported titanium oxide suspension (7-1) (average particle diameter: 940 nm, iron compound supported titanium oxide concentration: 10% by weight, electrical conductivity of the supernatant: 200 μS/cm, pH of the supernatant: 4.9, viscosity (at 22.5°C) ): 7.4 mPa·s) was obtained, and 530 g of crystalline iron compound-supported titanium oxide (7) (specific surface area: 80 m ² /g, average aspect ratio: 3) was obtained. The content of the iron compound in the obtained iron compound-supported titanium oxide (7) was 2000 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 753 ppm.

Example 8

In the above (preparation of coarse titanium oxide suspension), a coarse titanium oxide suspension (8) was obtained, except that the reaction temperature (temperature in the autoclave) was changed from 140° C. to 120° C. The coarse titanium oxide suspension (8) was subjected to the above (membrane filtration treatment (1) by the cross-flow method) in the same manner as in Example 2 to obtain a titanium oxide suspension (8-1), and a crystal plane (110) and a crystal plane 530 g of titanium oxide (8), which is a mixture of rod-shaped rutile type titanium oxide having (111), and rod-shaped rutile type titanium oxide having crystal plane (110), crystal plane (111), and crystal plane (001), were obtained. The photocatalytic ability of the obtained titanium oxide (8) evaluated by the toluene oxidation method by the following ultraviolet rays was 600 ppm (CO ₂ generation rate: 90%).

Thereafter, in the same manner as in Example 2, (iron compound-supporting treatment) and (membrane filtration treatment (2) by cross-flow method) were performed to obtain a coarse iron compound-supported titanium oxide suspension (8), and an iron compound-supported titanium oxide A suspension (8-1) (average particle diameter: 800 nm, iron compound-supported titanium oxide concentration: 10% by weight, supernatant electrical conductivity: 200 μS/cm, supernatant pH: 5.2) was obtained, and crystalline iron compound-supported titanium oxide ( 8) (specific surface area: 85 m ² /g, average aspect ratio: 2) was obtained. The content of the iron compound in the obtained iron compound-supported titanium oxide (8) was 780 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 691 ppm.

Example 9

In the above (preparation of coarse titanium oxide suspension), a coarse titanium oxide suspension (9) was obtained, except that the reaction temperature (temperature in the autoclave) was changed from 140° C. to 160° C. The coarse titanium oxide suspension (9) was subjected to the above (membrane filtration treatment (1) by the cross flow method) in the same manner as in Example 2 to obtain a titanium oxide suspension (9-1), and a crystal plane (110) and a crystal plane 530 g of titanium oxide (9), which is a mixture of rod-shaped rutile type titanium oxide having (111), and rod-shaped rutile type titanium oxide having crystal plane (110), crystal plane (111), and crystal plane (001), were obtained. The photocatalytic ability of the obtained titanium oxide (9) evaluated by the toluene oxidation method by the following ultraviolet rays was 645 ppm (decomposition rate: 95%).

Thereafter, in the same manner as in Example 2, (iron compound-supporting treatment) and (membrane filtration treatment (2) by a cross-flow method) were performed to obtain a coarse iron compound-supported titanium oxide suspension (9), and an iron compound-supported titanium oxide A suspension (9-1) (average particle diameter: 1000 nm, iron compound supported titanium oxide concentration: 10% by weight, supernatant electrical conductivity: 200 μS/cm, supernatant pH: 5.2) was obtained, and crystalline iron compound supported titanium oxide ( 9) (specific surface area: 55 m ² /g, average aspect ratio: 12) was obtained. The content of the iron compound in the obtained iron compound-supported titanium oxide (9) was 820 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 727 ppm.

Example 10

(Preparation of coarse titanium oxide suspension)

At room temperature (25°C), a titanium tetrachloride aqueous solution (Ti concentration: 16.5% by weight±0.5% by weight, chlorine ion concentration: 31% by weight±2% by weight, manufactured by Doho Titanium Co., Ltd.) is added so that the Ti concentration becomes 5.6% by weight. It was diluted with pure water. 5650 g of the diluted titanium tetrachloride aqueous solution was placed in a 10 L tantalum lined autoclave and sealed. Using the heat medium, the temperature in the autoclave was raised to 140°C over 2 hours. Then, the autoclave was cooled by cooling the heat medium after holding for 10 hours under the conditions of temperature: 140°C and pressure: vapor pressure at that temperature while stirring at ¹³ W/m ³ of stirring required power (Pv value). It was confirmed that the temperature in the autoclave became 40°C or less, and 5650 g of the coarse titanium oxide suspension (10) was taken out.

(Membrane filtration treatment by cross flow method (1))

Without diluting the obtained coarse titanium oxide suspension (10) with pure water, a hollow fiber type ultrafiltration membrane (brand name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, manufactured by Daisen Membrane Systems Co., Ltd.) Using, at room temperature (25°C) and a filtration pressure of 0.02 MPa, filtration treatment by a cross-flow method was performed while adding pure water in an amount equal to the amount of permeate. The concentrate obtained through the filtration treatment was circulated again in the input tank, and was repeatedly added to the filtration treatment until the pH of the permeate reached 4.0. In the meantime, backwashing was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank. Thereby, 5650 g of a titanium oxide suspension (10-1) was obtained. A titanium oxide suspension (10-1) was dried at 105°C for 1 hour under normal pressure, and rod-shaped rutile titanium oxide having a crystal face (110) and a crystal face (111), and a crystal face (110), a crystal face (111) and a crystal face Titanium oxide (10), which is a mixture of rod-shaped rutile type titanium oxide having (001), was obtained. The photocatalytic ability of the obtained titanium oxide (10) evaluated by the toluene oxidation method by the following ultraviolet rays was 647 ppm (decomposition rate: 95%).

(Iron compound supporting treatment)

To the titanium oxide suspension (10-1) obtained above, 7.5 g of an aqueous iron chloride solution (35% by weight) was added, and the mixture was stirred at room temperature (25°C) for 30 minutes. Thereafter, 95 g of methanol (1.7% by weight of the titanium oxide suspension) was added, and ultraviolet (UV) was irradiated for 3 hours using a 100W high-pressure mercury lamp (UV irradiation amount: 5mW/cm ² ), and coarse iron compound supported oxidation A titanium suspension (10) was obtained.

(Membrane filtration treatment by cross flow method (2))

Hollow fiber type ultrafiltration membrane (brand name ``FS03-FC-FUS03C1'', material: PES, nominal molecular weight: 30,000, Daisen Membrane Systems Co., Ltd.) without diluting the coarse iron compound-supported titanium oxide suspension (10) with pure water Agent), at room temperature (25°C) and a filtration pressure of 0.02 MPa, filtration treatment by a cross-flow method was performed while adding pure water in an amount equal to the amount of permeate. The concentrate obtained through the filtration treatment was circulated again in the input tank, and repeatedly added to the filtration treatment until the electrical conductivity of the permeated liquid became 200 µS/cm. In the meantime, backwashing was performed for 1 minute at a pressure of 0.1 MPa and a flow rate of 2 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank. Thereby, an iron compound-supported titanium oxide suspension (10-1) (average particle diameter: 920 nm, iron compound-supported titanium oxide concentration: 10% by weight, electrical conductivity of the supernatant: 200 μS/cm, and pH of the supernatant: 4.9) was obtained.

Then, it dried at 105 degreeC for 1 hour under normal pressure, and obtained 530 g of crystalline iron compound-supported titanium oxide (10) (specific surface area: 76 m ² /g, average aspect ratio: 5). The content of the iron compound in the obtained iron compound-supported titanium oxide (10) was 820 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 778 ppm.

Example 11

(Preparation of coarse titanium oxide suspension)

At room temperature (25°C), a titanium tetrachloride aqueous solution (Ti concentration: 16.5% by weight±0.5% by weight, chlorine ion concentration: 31% by weight±2% by weight, manufactured by Doho Titanium Co., Ltd.) is added so that the Ti concentration becomes 5.6% by weight. It was diluted with pure water. 560 g of the diluted titanium tetrachloride aqueous solution was put in a 1 L tantalum lined autoclave and sealed. Using the heat medium, the temperature in the autoclave was raised to 140°C over 2 hours. Then, the autoclave was cooled by cooling the heat medium after holding for 10 hours under the conditions of temperature: 140°C and pressure: vapor pressure at that temperature while stirring at ¹³ W/m ³ of stirring required power (Pv value). It was confirmed that the temperature in the autoclave became 40°C or less, and 560 g of the coarse titanium oxide suspension (11) was taken out.

(Membrane filtration treatment by cross flow method (1))

The obtained coarse titanium oxide suspension (11) was diluted 10 times with pure water, and a hollow fiber type ultrafiltration membrane (brand name "FS03-FC-FUS03C1", material: PES, nominal molecular weight: 30,000, manufactured by Daisen Membrane Systems Co., Ltd. ), at room temperature (25° C.) and a filtration pressure of 0.05 MPa, while adding pure water in an amount equal to the amount of the permeated liquid, was subjected to filtration by a cross flow method. The concentrate obtained through the filtration treatment was circulated again in the input tank, and was repeatedly added to the filtration treatment until the permeate had a pH of 2.9. After that, the addition of pure water was stopped and the titanium oxide concentration was concentrated to obtain a titanium oxide suspension (11-1). In the meantime, backwashing was performed for 1 minute at a pressure of 0.15 MPa and a flow rate of 0.1 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank. The titanium oxide suspension (11-1) was dried for 15 hours at 60°C under reduced pressure, and rod-shaped rutile titanium oxide having a crystal face (110) and a crystal face (111), and a crystal face (110), a crystal face (111) and a crystal face Titanium oxide (11), which is a mixture of rod-like rutile type titanium oxide having (001), was obtained. The photocatalytic ability of the obtained titanium oxide (11) evaluated by the toluene oxidation method by the following ultraviolet rays was 617 ppm (CO ₂ generation rate: 93%).

(Iron compound supporting treatment)

To the titanium oxide suspension (11-1) obtained above, 0.3 g of an aqueous iron chloride solution (35% by weight) was added, followed by stirring at room temperature (25°C) for 30 minutes. Then, methanol 9.6g (1.7% by weight of the titanium oxide suspension) was added, and ultraviolet (UV) was irradiated for 3 hours using a 100W high-pressure mercury lamp (UV irradiation amount: 0.9 mW/cm ² ), and a rough iron compound A supported titanium oxide suspension (11) was obtained.

(Membrane filtration treatment by cross flow method (2))

A coarse iron compound-supported titanium oxide suspension (11) was diluted 10-fold with pure water, and a hollow fiber type ultrafiltration membrane (brand name ``FS03-FC-FUS03C1'', material: PES, nominal molecular weight: 30,000, Daisen Membrane Systems Co., Ltd. ) Agent), at room temperature (25° C.) and a filtration pressure of 0.05 MPa, while adding pure water in an amount equal to the amount of permeated liquid, was subjected to filtration by a cross flow method. The concentrate obtained through the filtration treatment was circulated again in the input tank, and was repeatedly added to the filtration treatment until the electrical conductivity of the permeated liquid became 21 µS/cm. Thereafter, the addition of pure water was stopped, the iron compound-supported titanium oxide concentration was concentrated, and the iron compound-supported titanium oxide suspension (11-1) (average particle diameter: 800 nm, the iron compound-supported titanium oxide concentration: 5% by weight, the supernatant Electrical conductivity: 21 μS/cm, pH of the supernatant: 5.2) was obtained. In the meantime, backwashing was performed for 1 minute at a pressure of 0.15 MPa and a flow rate of 0.1 kg/min at a rate of once per hour. The washing water that had just passed by this backwash was circulated in the input tank.

Then, it dried at 60 degreeC for 15 hours under reduced pressure, and obtained the crystalline iron compound-supported titanium oxide (11) (specific surface area: 71 m ² /g, average aspect ratio: 9) 40 g. The content of the iron compound in the obtained iron compound-supported titanium oxide (11) was 420 ppm. In addition, the photocatalytic ability evaluated by the following visible light toluene oxidation method was 416 ppm, and the photocatalytic ability evaluated by the following visible light methanol oxidation method was 716 ppm.

Comparative Example 1

The coarse titanium oxide suspension (11) obtained in Example 11 was subjected to high-speed centrifugation (20000 G × 60 minutes), followed by high-speed centrifugation until the pH of the supernatant was 2.9, followed by extraction of the supernatant, addition of pure water, and water dispersion. Water washing treatment was performed to obtain a filter residue (12-1). The obtained filtration residue was suspended in water and pulverized until the average particle diameter became 800 nm, thereby obtaining a titanium oxide suspension (12-1) (titanium oxide concentration: 5% by weight).

(Iron compound supporting treatment)

To the titanium oxide suspension (12-1) obtained above, 0.3 g of an aqueous iron chloride solution (35% by weight) was added, followed by stirring at room temperature (25°C) for 30 minutes. Then, methanol 9.6g (1.1% by weight of the titanium oxide suspension) was added, and ultraviolet (UV) was irradiated for 3 hours using a 100W high-pressure mercury lamp (UV irradiation amount: 0.9 mW/cm ² ), and a rough iron compound A supported titanium oxide suspension (12) was obtained.

The obtained coarse iron compound-supported titanium oxide suspension (12) was again centrifuged at high speed in the same manner as above, and then centrifuged at high speed until the electrical conductivity of the supernatant was 21 μS/cm, followed by extraction of the supernatant, addition of pure water, and repetition of water dispersion. Washing with water was performed to obtain a filter residue (12-2). The obtained filtrate was suspended in water and pulverized until the average particle diameter became 800 nm, and the iron compound supported titanium oxide suspension (12-1) (average particle diameter: 800 nm, iron compound supported titanium oxide concentration: 5% by weight, supernatant Electrical conductivity of: 21 μS/cm, pH of the supernatant: 5.2) was obtained.

Then, it dried at 60 degreeC for 15 hours under reduced pressure, and obtained the crystalline iron compound-supported titanium oxide (12) (specific surface area: 220 m ² /g, average aspect ratio: 1.3) 40 g. The content of the iron compound in the obtained iron compound-supported titanium oxide (12) was 88 ppm. In addition, the photocatalytic ability evaluated by the following visible light toluene oxidation method was 459 ppm, and the photocatalytic ability evaluated by the following visible light methanol oxidation method was 491 ppm.

Comparative Example 2

In the same manner as in Example 2, except that in the above (filtration treatment (2) by the cross-flow method), the electrical conductivity of the permeate was 700 μS/cm, the iron compound-supported titanium oxide suspension (13- 1) (average particle diameter: 80000 nm, iron compound-supported titanium oxide concentration: 10% by weight, supernatant electrical conductivity: 700 μS/cm, supernatant pH: 2.9) was obtained, and crystalline iron compound-supported titanium oxide (13) (ratio Surface area: 78 m ² /g, average aspect ratio: 1.2) 530 g was obtained. The content of the iron compound in the obtained iron compound-supported titanium oxide (13) was 20 ppm. In addition, the photocatalytic ability evaluated by the methanol oxidation method using the following visible light was 300 ppm.

<Evaluation method of photocatalytic ability>

(Toluene oxidation method by visible light)

Using the iron compound-supported titanium oxide obtained in Examples and Comparative Examples as a photocatalyst, toluene was oxidized in a gas phase, and the photocatalytic activity was evaluated by measuring the amount of CO ₂ produced.

200 mg of iron compound-supported titanium oxide was spread on a glass plate and placed in a reaction vessel (Tedrabag, material: vinyl fluoride resin), and 125 mL of 100 ppm of toluene gas was blown into the reaction vessel. After the adsorption of toluene gas to the iron compound-supported titanium oxide reached equilibrium, light irradiation (LED, light intensity: 2.5 mW/cm ² , light wavelength: 455 nm) was performed at room temperature (25°C). The amount of CO ₂ produced 24 hours after the start of light irradiation (CO ₂ concentration in the reaction vessel) was measured by a gas chromatograph with a hydrogen salt ionization detector attached to the methanizer (brand name ``MT221'', manufactured by GL Science) (brand name ``GC -14B", manufactured by Shimadzu Corporation) was used for measurement.

(Methanol oxidation method by visible light)

Using the iron compound-supported titanium oxide obtained in Examples and Comparative Examples as a photocatalyst, methanol was oxidized in a gas phase, and the photocatalytic performance was evaluated by measuring the amount of CO ₂ produced.

200 mg of titanium oxide supported by an iron compound was spread out on a glass dish and placed in a reaction vessel (Tedrabag, material: vinyl fluoride resin), and 125 mL of 800 ppm methanol gas was blown into the reaction vessel. After the adsorption of methanol gas to the iron compound-supported titanium oxide reached equilibrium, light irradiation (LED, light intensity: 2.5 W/m ² , light wavelength: 455 nm) was performed at room temperature (25° C.). The amount of CO ₂ produced 24 hours after the start of light irradiation (CO ₂ concentration in the reaction vessel) was measured by a gas chromatograph with a hydrogen salt ionization detector attached to the methanizer (brand name ``MT221'', manufactured by GL Science) (brand name ``GC -14B", manufactured by Shimadzu Corporation) was used for measurement.

(Toluene oxidation method by ultraviolet rays)

Using the titanium oxide obtained in the examples as a photocatalyst, toluene was oxidized in a gas phase, and the photocatalytic activity was evaluated by measuring the amount of CO ₂ produced.

200 mg of titanium oxide was spread on a glass dish and placed in a reaction vessel (Tedrabag, material: vinyl fluoride resin), and 125 mL of 100 ppm of toluene gas was blown into the reaction vessel. After the adsorption of toluene gas to titanium oxide reached equilibrium, light irradiation (LED, light intensity: 0.1 mW/cm ² , light wavelength: 365 nm) at room temperature (25° C.) was performed. The amount of CO ₂ produced 24 hours after the start of light irradiation (CO ₂ concentration in the reaction vessel) was measured by a gas chromatograph with a hydrogen salt ionization detector attached to the methanizer (brand name ``MT221'', manufactured by GL Science) (brand name ``GC -14B", manufactured by Shimadzu Corporation) was used for measurement.

The transition metal compound-supported titanium oxide suspension of the present invention contains a transition metal compound-supported titanium oxide crystal having an average aspect ratio of 1.5 or more, and has an extremely low content of ionic impurities. Therefore, it has excellent responsiveness to visible light, absorbs sunlight, light in an ordinary living space such as incandescent lamps, fluorescent lamps, and LED lights, and can decompose harmful chemical substances into water or carbon dioxide. That is, the transition metal compound-supported titanium oxide suspension of the present invention can be suitably used also as a photocatalyst under LED lighting. In addition, it can be used for various purposes such as antibacterial, fungicidal, deodorization, air purification, water purification, and antifouling. In addition to indoor wallpaper and furniture, environmental purification in public facilities such as homes, hospitals, schools, etc. It can be applied to a wide range such as high functionality.

Claims (7)

A step of obtaining a mixture containing a transition metal compound-supported titanium oxide by adding and impregnating a solution containing a transition metal compound to the crystalline titanium oxide suspension, and a step of adding the obtained mixture to membrane filtration by a cross flow method for purification. A method for producing a transition metal compound-supported titanium oxide suspension through which a transition metal compound-supported titanium oxide suspension having the following characteristics is prepared.
[The transition metal compound-supported titanium oxide suspension,
It contains titanium oxide supported by a transition metal compound having an average aspect ratio (long/short axis) of 1.5 or more,
When containing 4% by weight or more of transition metal compound-supported titanium oxide, the electrical conductivity of the supernatant is 300 μS/cm or less.] 2. A method for producing a transition metal compound-supported titanium oxide suspension. The method for producing a transition metal compound-supported titanium oxide suspension according to claim 1 or 2, wherein the transition metal compound-supported titanium oxide has a specific surface area of 10 m ² /g or more. The method for producing a transition metal compound-supported titanium oxide suspension according to claim 1 or 2, wherein the supernatant has a pH of 3 or more. The preparation of a transition metal compound-supported titanium oxide suspension according to claim 1 or 2, wherein when the transition metal compound-supported titanium oxide concentration is adjusted to 10% by weight, its viscosity (at 22.5° C.) is 5 to 25 mPa·s. Way. The method for producing a transition metal compound-supported titanium oxide suspension according to claim 1 or 2, wherein the transition metal compound-supported titanium oxide has an average particle diameter of 20 µm or less. A step of obtaining a mixture containing a transition metal compound-supported titanium oxide by adding and impregnating a solution containing a transition metal compound to the crystalline titanium oxide suspension, and adding the obtained mixture to membrane filtration by a cross flow method to have the following characteristics: A method for producing a transition metal compound-supported titanium oxide, in which a transition metal compound-supported titanium oxide is produced through a step of obtaining a transition metal compound-supported titanium oxide suspension and a step of drying the obtained transition metal compound-supported titanium oxide suspension.
[The transition metal compound-supported titanium oxide suspension,
It contains titanium oxide supported by a transition metal compound having an average aspect ratio (long/short axis) of 1.5 or more,
When containing 4% by weight or more of transition metal compound-supported titanium oxide, the electrical conductivity of the supernatant is 300 μS/cm or less.]

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