JP2009233635A - Method and apparatus for water purification - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and apparatus for water purification capable of easily and effectively decomposing an organic substance in water using simply structured installations without utilizing expensive oxygen gas. <P>SOLUTION: The method for water purification is characterized in that air micro-bubbles are injected to water to be treated that contains organic substances, and then the water to be treated is brought into contact with a photocatalyst having titanium oxide on its surface while irradiating the water with ultraviolet rays. The photocatalyst is preferably a nonwoven fabric of a photocatalyst fiber having titanium oxide on its surface. The ultraviolet ray exposed to the photocatalyst preferably has its peak wavelengths at 180 to 190 nm and 250 to 260 nm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a water purification device and a water purification method capable of purifying water by effectively decomposing unnecessary organic substances existing in water using a photocatalyst.

  In recent years, recycling of wastewater has been promoted, and organic substances contained in wastewater by biological treatment have been decomposed for recycling. However, the wastewater treatment by the above-mentioned organisms cannot deny the enlargement of the treatment facility and the long treatment time. Therefore, there is a need for a water treatment apparatus that can effectively decompose and purify organic substances contained in water. As an apparatus for purifying unnecessary organic substances contained in water, for example, in Patent Document 1, a structure in which OH radicals are efficiently generated using a titanium oxide photocatalyst and the OH radicals and organic substances in water are in good contact with each other. It is disclosed that high decomposition efficiency can be obtained.

As a method for decomposing organic substances in water, Patent Document 2 discloses a method of bubbling oxygen gas into treated water.
Japanese Patent No. 3436267 JP 2002-113474 A

  However, in the method described in Patent Document 2, since oxygen gas with high oxygen purity is used, it is necessary to be careful in handling oxygen gas, is expensive, requires special equipment, and is not practical. Moreover, although the water treatment apparatus of patent document 1 is an excellent water treatment apparatus, it has the problem that sufficient decomposition efficiency for satisfying modern high water quality standards cannot be obtained, and further higher decomposition efficiency. It has been demanded. An object of the present invention is to provide a water purification method and a water purification apparatus capable of effectively decomposing organic substances present in water with an easy and simple configuration without using expensive oxygen gas. .

  In order to achieve the above object, the present inventors have conducted intensive research, and as a result, treated water, in which microbubbles of air are injected into treated water containing organic matter, is treated with a photocatalyst to efficiently purify water. The present invention has been found.

That is, the present invention provides a water purification method comprising injecting air microbubbles into treated water containing an organic substance, and then contacting the treated water with a photocatalyst having titanium oxide on the surface while irradiating ultraviolet rays. About. The photocatalyst is preferably a non-woven fabric of photocatalyst fibers having titanium oxide on the surface. Moreover, it is preferable that the said ultraviolet-ray irradiated to a photocatalyst has a peak wavelength in 180-190 nm and 250-260 nm.
The present invention also provides water comprising a microbubble injection tank that injects microbubbles of air into treated water containing organic matter, and a photocatalytic decomposition tank that decomposes organic matter in the treated water that has flowed out of the microbubble injection tank using a photocatalyst. The present invention relates to a purification device. As one embodiment of the photocatalyst decomposition tank, it is preferable that a flat nonwoven fabric of photocatalyst fibers having titanium oxide on the surface and an ultraviolet lamp are installed substantially perpendicular to the flow direction of the treated water.

  In one embodiment of the present invention, the photocatalytic fiber is a composite oxidation of an oxide phase (first phase) mainly composed of a silica component having a photocatalytic function and a metal oxide phase (second phase) containing Ti. It is related with the said water purification apparatus which is a silica group composite oxide fiber which consists of a product fiber, and the ratio of Ti of the metal oxide which comprises a 2nd phase is increasing toward the surface layer of a fiber.

  Furthermore, in one embodiment of the present invention, platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), gold (Au), silver (Ag), copper (Cu) is formed on the surface of the photocatalytic fiber. ), Iron (Fe), nickel (Ni), zinc (Zn), gallium (Ga), germanium (Ge), indium (In) and tin (Sn) on which at least one metal is supported The present invention relates to a water purification apparatus.

  As described above, according to the present invention, there is provided a water purification method capable of effectively decomposing organic matter by a photocatalyst by making unnecessary air present in water into microbubbles in the air without using expensive oxygen gas. A water purification apparatus can be provided.

  Next, embodiments of a water purification method and a water purification apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual cross-sectional view of a water purification apparatus according to this embodiment. The water purification method of the present invention is characterized by injecting air microbubbles into treated water containing an organic substance, and then contacting the treated water with a photocatalyst having titanium oxide on the surface while irradiating ultraviolet rays.

  The water purification apparatus 10 according to the present embodiment includes a microbubble injection tank 20 that injects microbubbles of air, and a photocatalytic decomposition tank 30 that decomposes organic matter in the treated water flowing out of the microbubble injection tank 20 with a photocatalyst. ing. The treated water containing organic matter flows from the treated water inlet 11 and becomes treated water containing microbubbles in the microbubble injection tank 20. When the treated water containing the microbubbles flows into the photocatalytic decomposition tank 30 through the water supply line 12 and passes through the photocatalytic decomposition tank 30, the organic matter is decomposed by the photocatalyst, and the treated water is discharged from the treatment outlet 13. leak.

  FIG. 2 is a conceptual cross-sectional view of the microbubble injection tank 20 according to the present embodiment. In the microbubble injection tank 20, microbubbles are injected into the treated water. The microbubble injection tank 20 is provided with a treated water inlet 11, a water supply line 12 for introducing the treated water to the next photocatalyst decomposition tank, and a microbubble generator 23. The treated water stored in the microbubble injection tank 20 flows into the microbubble generator 23 from the inlet 21 of the microbubble generator, and the treated water containing air microbubbles of 50 μm or less generated in the microbubble generator 23 generates microbubbles. It has a circulation system structure that flows out from the apparatus outlet 22 and is accommodated in the microbubble injection tank 20. In general, a micro bubble refers to a bubble having a bubble size of 50 μm or less, and exhibits characteristics different from those of a normal bubble. For example, air bubbles due to a self-pressurizing effect in which the rising speed of a bubble is much slower than a normal bubble. It has properties such as supersaturation dissolution in water.

  In general, a method for generating microbubbles includes a pressure dissolution method, an ejector method, a cavitation method, and a swivel method. Since the characteristics of microbubbles depend on the diameter and amount of bubbles generated, a pressure-melting generation method that can generate relatively large amounts of fine bubbles is preferable. Further, the diameter of the generated microbubbles is preferably 30 μm or less.

  The amount of dissolved oxygen in the treated water in the microbubble injection tank 20 after microbubble injection is preferably 80 to 150% in terms of saturation. Also from the characteristics of the above-described microbubbles, oxygen exceeding the saturation amount of dissolved oxygen can be dissolved by the self-pressurizing effect of the microbubbles.

  As the photocatalyst, titanium oxide is generally used, and preferably anatase type titanium oxide is used. The shape of the photocatalyst body can take the form of powder, fiber, thin film, and thick film. In the fiber form, there are roughly three types of photocatalytic fibers. There are fibers composed of titanium oxide, fibers such as glass fibers whose surfaces are coated with titanium oxide, fibers having a gradient structure of titanium oxide on the surface and high-strength silica inside. When composed of titanium oxide, the strength of the fiber itself is low and breakage due to flowing water pressure tends to occur. In the case of coating, there is a problem that the coating phase is peeled off by flowing water. As already shown in Japanese Patent No. 3465699, the present inventors have prepared a photocatalytic fiber having a structure in which no bridging occurs between fibers and a photocatalytic component such as titanium oxide is densely deposited on the surface of each fiber. We are developing. Since this photocatalyst fiber is not based on the conventional coating method, the problem that the photocatalyst component on the fiber surface falls off is also solved. This non-woven fabric molding has a structure in which each fiber is dispersed with a certain amount of voids, so that the processing fluid passes through the gap between each fiber. The contact area is very large.

  FIG. 3 is a conceptual cross-sectional view of the photocatalytic decomposition tank 30 according to the present embodiment. A flow tank 31 for flowing water to be purified from a water supply line 12 formed on the bottom surface to a treated water outlet 13 formed on the top surface, and a flow direction of the water to be purified within the flow tank 31 to be purified. Three flat photocatalyst nonwoven fabric cartridges 32 arranged in parallel to each other so as to intersect perpendicularly, and an ultraviolet lamp 33 disposed between these flat photocatalyst nonwoven fabric cartridges 32 are provided.

  The treated water containing air microbubbles in the microbubble injection tank passes through the water supply line 12 and flows into the photocatalyst decomposition tank 30. The treated water poured in is discharged from the treated water outlet 13 through the fluidized tank 31. Since the flat nonwoven fabric 41 has a structure in which each of the fibers is dispersed with a certain amount of voids, the contact area with the photocatalyst is very large when water passes. For this reason, radicals are efficiently generated by the flat nonwoven fabric 41 having a photocatalytic function, and unnecessary organic substances are decomposed. Moreover, unnecessary organic substances are decomposed by directly irradiating water with 185 nm ultraviolet rays. Unnecessary organic substances that have not been completely decomposed are decomposed into organic acids, which are decomposition intermediate products, by OH radicals or the like. Therefore, even if the treated water discharged from the treated water outlet 13 is removed by ion exchange or the like. Good.

  Usually, in a water purification apparatus using a titanium oxide photocatalyst, a ultraviolet light lamp is a black light fluorescent lamp having a wavelength of 351 nm or a sterilizing lamp having a wavelength of 254 nm. This is because the titanium oxide photocatalyst can be excited at a wavelength of 387 nm or less, and these lamps are easily available as products. In the water purifying apparatus according to the present invention, high decomposition efficiency can be obtained by using ultraviolet rays that have not been used conventionally and making the photocatalyst have a predetermined arrangement structure. That is, in the water purification apparatus according to the present invention, the flat nonwoven fabric 41 on which the photocatalyst is supported is installed so as to be parallel to the flat nonwoven fabric 41, and peak wavelengths are set to 180 to 190 nm and 250 to 260 nm. Since it has the ultraviolet irradiation means for irradiating the ultraviolet rays it has, the ultraviolet light of 180 to 190 nm is not blocked by the photocatalyst while maintaining the light irradiation efficiency to the photocatalyst and the contact efficiency with the processing fluid. For this reason, it is possible to excite the photocatalyst by irradiating the flat nonwoven fabric 41 with ultraviolet rays of 250 to 260 nm, decompose organic substances with generated OH radicals, and directly decompose organic substances in water with ultraviolet rays of 180 to 190 nm, The decomposition effect can be kept high.

  The ultraviolet lamp 33 in the water purification apparatus according to the present invention is provided with a cover member for preventing contact between water and the ultraviolet light emitting member for use in water. That is, the ultraviolet light emitting member is inserted into the cover member. The cover member constituting the outer surface of the ultraviolet lamp 33 is formed in a cylindrical shape and is made of a material that transmits not only 250 to 260 nm but also a peak wavelength of 180 to 190 nm. An example of the material of the cover member is synthetic quartz. A general low-pressure mercury lamp originally has two wavelengths of 185 nm and 254 nm. However, since glass, which is a material of a normal cover member, does not transmit short-wave ultraviolet light, it irradiates only a wavelength of 254 nm. In the water purification apparatus according to the present embodiment, the ultraviolet lamp 33 can irradiate ultraviolet rays having peak wavelengths of 180 to 190 nm and 250 to 260 nm by making the material of the cover member special as described above. It is configured. The ultraviolet rays irradiated from the ultraviolet irradiation lamp 35 have a peak wavelength at 180 to 190 nm, preferably 185 nm, and a peak wavelength at 250 to 260 nm, preferably 254 nm. For example, two ultraviolet lamps 33 are arranged between each of the flat photocatalyst nonwoven fabric cartridges 32, for a total of four, so that the axial directions thereof are parallel to the flat photocatalytic nonwoven fabric cartridge 32, respectively. Is arranged. In the present embodiment, the cover member of the ultraviolet irradiation lamp 33 is formed in a cylindrical shape, but is not limited thereto, and may be any shape that extends in the longitudinal direction. The number of ultraviolet lamps 33 is determined according to the required water quality, the amount of unnecessary organic substances contained in the treated water, and the like.

  As shown in FIG. 4, each flat photocatalyst nonwoven fabric cartridge 32 includes a photocatalytic fiber flat nonwoven fabric 41 and a pair of wire meshes 42, and the flat nonwoven fabric 41 is sandwiched between a pair of stainless steel wire meshes. Thus, by using a wire mesh as a support material and making it into a cartridge shape, the flat nonwoven fabric 41 having a deteriorated photocatalytic function can be easily replaced. Desorption can be facilitated by providing a multi-stage flat photocatalyst nonwoven fabric cartridge with a connecting structure using a frame or the like. In the present embodiment, the number of the flat nonwoven fabric 41 is three, but the number can be arbitrarily determined according to the required water quality and the like, for example, 1 to 50. Moreover, in this Embodiment, although the flat nonwoven fabric was fixed to the flow tank 31 as the flat photocatalyst nonwoven fabric cartridge 32, you may install by the other means. In the present embodiment, each flat photocatalyst nonwoven fabric cartridge 32 is installed so that its surface intersects substantially perpendicularly to the direction of water flow. It is a range that passes through the nonwoven fabric cartridge 32, and may be installed, for example, tilted around 10 °, preferably around 5 ° with respect to the flow direction.

In the water purification apparatus of the present embodiment, the average UV intensity on flat nonwoven is preferably is preferably 1~10mW / cm ^2, a further range of 2~8mW / cm ^2. When the ultraviolet intensity on the surface of the flat nonwoven fabric is 1 to 10 mW / cm ² , water treatment with two ultraviolet components can be performed with high efficiency. In order to make such a range, the distance between the ultraviolet irradiation means and the flat nonwoven fabric may be set to an appropriate range. Here, the average ultraviolet intensity can be obtained by measuring the ultraviolet intensity at a plurality of locations from the center to the end of the nonwoven fabric surface and averaging the values to obtain the average ultraviolet intensity.

  A preferred form of the flat nonwoven fabric 41 is a composite oxide of an oxide phase mainly composed of a silica component (hereinafter referred to as a first phase) and a metal oxide phase containing Ti (hereinafter referred to as a second phase). It consists of a certain silica-based composite oxide fiber.

  The first phase is an oxide phase mainly composed of a silica component, and may be amorphous or crystalline, and may be a metal element or metal oxide capable of forming a solid solution or a eutectic compound with silica. It may contain. Examples of the metal element (A) that can form a solid solution with silica include titanium. Examples of the metal element (B) of the metal oxide that can form a solid solution with silica include aluminum, zirconium, yttrium, lithium, sodium, barium, calcium, boron, zinc, nickel, manganese, magnesium, and iron. It is done.

  The first phase forms the internal phase of the silica-based composite oxide fiber and plays an important role in bearing the mechanical properties. The ratio of the first phase to the entire silica-based composite oxide fiber is preferably 40 to 98% by weight, and the desired function of the second phase is sufficiently expressed, and high mechanical properties are also expressed. For this purpose, it is more preferable to control the ratio of the first phase within the range of 50 to 95% by weight.

  On the other hand, the second phase is a metal oxide phase containing Ti and plays an important role in developing the photocatalytic function. Ti is mentioned as a metal which comprises a metal oxide. The metal oxide may be a simple substance, or may be a compound in which a substitutional solid solution is formed with the eutectic compound or a specific element. The second phase forms the surface layer phase of the silica-based composite oxide fiber, and the proportion of the second phase of the silica-based composite oxide fiber varies depending on the type of metal oxide, but is 2 to 60% by weight. Preferably, it is more preferably controlled within a range of 5 to 50% by weight in order to sufficiently exhibit its function and to simultaneously exhibit high strength. The crystal grain size of the metal oxide containing Ti of the second phase is preferably 15 nm or less, particularly preferably 10 nm or less.

  The proportion of Ti contained in the metal oxide contained in the second phase increases in a gradient toward the surface of the silica-based composite oxide fiber, and the thickness of the region where the gradient of the composition is clearly recognized is the surface layer. From 5 to 500 nm, but may be about 1/3 of the fiber diameter. The “existence ratio” of the first phase and the second phase refers to the first phase with respect to the metal oxide constituting the first phase and the entire metal oxide constituting the second phase, that is, the entire silica-based composite oxide fiber. % By weight and the second phase metal oxide.

  The flat nonwoven fabric 41 made of silica-based composite oxide fiber can be obtained by the following production method.

  The silica-based composite oxide fiber is a modified polycarbosilane having a structure in which a polycarbosilane having a main chain skeleton represented by the following chemical formula 1 having a number average molecular weight of 200 to 10,000 is modified with an organometallic compound or a modified polycarbosilane A silica-based composite oxide fiber can be produced by melt spinning a mixture of polycarbosilane and an organometallic compound, followed by infusibilization and firing in air or oxygen. Hereinafter, these will be described in detail by dividing them into a first step to a fourth step.

(However, R in the formula represents a hydrogen atom, a lower alkyl group or a phenyl group.)
(First step)
This is a process for producing a modified polycarbosilane having a number average molecular weight of 1,000 to 50,000 used as a starting material for producing a silica-based composite oxide fiber. The basic production method of the modified polycarbosilane is very similar to JP-A-56-74126, but it is necessary to carefully control the bonding state of the functional group described therein. This is outlined below.

  The modified polycarbosilane as the starting material is composed mainly of a polycarbosilane having a main chain skeleton represented by the above chemical formula 1 having a number average molecular weight of 200 to 10,000, and a general formula of M (OR ′) n or MR ″. an organometallic compound having a basic structure of m (M is a metal element, R ′ is an alkyl group or phenyl group having 1 to 20 carbon atoms, R ″ is acetylacetonate, and m and n are integers greater than 1) Is derived from

  In order to produce a silica-based composite oxide fiber having an inclined structure, it is necessary to select a slow reaction condition in which only a part of the organometallic compound forms a bond with polycarbosilane. For this purpose, it is necessary to react in an inert gas at a temperature of 280 ° C. or lower, preferably 250 ° C. or lower. Under these reaction conditions, even if the organometallic compound reacts with polycarbosilane, it is bonded as a monofunctional polymer (that is, bonded in a pendant form), and no significant increase in molecular weight occurs. The modified polycarbosilane partially bonded with the organometallic compound plays an important role in improving the compatibility between the polycarbosilane and the organometallic compound.

  In addition, when many functional groups more than two functional groups couple | bond together, the bridge | crosslinking structure of polycarbosilane is formed and the remarkable increase in molecular weight is recognized. In this case, a sudden exotherm and a rise in melt viscosity occur during the reaction. On the other hand, when only one functional group reacts and an unreacted organometallic compound remains, conversely, a decrease in melt viscosity is observed.

  In order to produce a silica-based composite oxide fiber having an inclined structure, it is desirable to select conditions that intentionally leave an unreacted organometallic compound. Mainly, the modified polycarbosilane and the unreacted organometallic compound or the organic metal compound of about 2 to 3 mer are used as starting materials. However, the modified polycarbosilane alone has a very low molecular weight modified polycarbosilane. If a silane component is included, it can be used as a starting material as well.

(Second step)
A spinning dope is prepared by melting the modified polycarbosilane obtained in the first step or a mixture of the modified polycarbosilane and a low molecular weight organometallic compound (hereinafter sometimes referred to as a precursor). Is filtered to remove substances that are harmful when spinning, such as microgels and impurities, and this is spun by a commonly used apparatus for spinning synthetic fibers. The temperature of the spinning dope during spinning varies depending on the softening temperature of the raw material modified polycarbosilane, but a temperature range of 50 to 200 ° C. is advantageous. In the above spinning apparatus, a humidification heating cylinder may be provided below the nozzle as necessary. The fiber diameter is adjusted by changing the discharge amount from the nozzle and the winding speed of a high-speed winding device installed at the lower part of the spinning machine. Alternatively, the fiber discharged from the nozzle may be directly molded into a felt shape by a melt blow method or a spun bond method.

  In addition to the melt spinning, the modified polycarbosilane obtained in the first step, or a mixture of the modified polycarbosilane and a low molecular weight organometallic compound, for example, benzene, toluene, xylene or other modified polycarbosilane and a low molecular weight Synthetic fibers that are usually used after dissolving an organometallic compound in a solvent that can be melted to form a spinning dope, and in some cases filtering this to remove harmful substances such as macrogel and impurities Spinning can be performed by a dry spinning method using a spinning device, and the winding speed can be controlled to obtain a target fiber.

  In these spinning processes, if necessary, a spinning cylinder is attached to the spinning device, and the atmosphere in the cylinder is mixed with at least one gas of the solvent, or air, inert gas, hot air, By setting the atmosphere of heat inert gas, steam, ammonia gas, hydrocarbon gas, and organosilicon compound gas, solidification of the fibers in the spinning cylinder can be controlled.

(Third step)
The spun fiber obtained in the second step is preheated in an oxidizing atmosphere under the action of tension or no tension to infusibilize the spun fiber. This step is performed for the purpose of preventing the fibers from melting and adhering to the adjacent fibers during the subsequent baking. The treatment temperature and treatment time vary depending on the composition and are not particularly limited, but generally, a treatment condition of several hours to 30 hours is selected within a range of 50 to 400 ° C. The oxidizing atmosphere may contain moisture, nitrogen oxides, ozone, or the like that increases the oxidizing power of the spun fiber, and the oxygen partial pressure may be changed intentionally.

  By the way, depending on the ratio of the low molecular weight substance contained in the raw material, the softening temperature of the spun fiber may be lower than 50 ° C. In this case, the fiber surface oxidation is promoted at a temperature lower than the treatment temperature in advance. In some cases, processing is performed. In the second step and the third step, it is considered that the low molecular weight compound contained in the raw material progresses to the fiber surface, and the base of the target gradient composition is formed. .

(4th process)
The fiber insolubilized in the third step is fired in an oxidizing atmosphere at a temperature range of 500 to 1800 ° C. under tension or no tension, and the target oxide phase mainly composed of silica component (first phase) ) And a metal oxide phase (second phase) containing Ti, a silica-based composite in which the Ti content of the metal oxide constituting the second phase increases in a gradient toward the surface layer. An oxide fiber is obtained. In this step, the organic component contained in the infusible fiber is basically oxidized, but depending on the conditions selected, it may remain in the fiber as carbon or carbide. Even in such a state, when the target function is not hindered, it is used as it is. However, when the target function is hindered, further oxidation treatment is performed. At that time, the temperature and processing time must be selected so as not to cause problems in the intended gradient composition and crystal structure.

  After the silica-based composite oxide fiber having a photocatalytic function obtained in the fourth step is made into a short fiber, needle punching or the like is performed to obtain the flat nonwoven fabric 41.

  As another production method, a flat nonwoven fabric made of silica-based composite oxide fibers is melt-blown using a melt-blowing method, and the melt is discharged from a spinning nozzle and from around the spinning nozzle. Spinning by blowing heated nitrogen gas, forming a nonwoven fabric by collecting the spun fibers in a receiver placed at the bottom of the spinning nozzle, and then firing the nonwoven fabric in an oxidizing atmosphere after infusibility treatment Can be manufactured.

  The diameter of the spinning nozzle is usually about 100 to 500 μm. Nitrogen gas ejection speed is about 30 to 300 m / s, and the higher the speed, the thinner the fiber. The heating temperature of the nitrogen gas is not particularly limited as long as a desired spun fiber can be obtained, but nitrogen gas heated to about 500 ° C. is usually ejected. Conventionally, in a general melt-blowing method, air is used as a jet gas, but it is necessary to use nitrogen in order to spin the precursor. Spinning can be performed stably by using nitrogen as the jet gas.

  When collecting the spun fiber in a receiver disposed at the lower part of the spinning nozzle, it is preferable to perform spinning while sucking from the lower side of the receiver using a suckable receiver. By sucking, the fibers are effectively entangled and a high-strength nonwoven fabric is obtained. The suction speed is preferably in the range of about 2 to 10 m / s.

  The obtained nonwoven fabric is subjected to the same infusibility treatment and firing as in the case of the melt spinning, whereby a flat nonwoven fabric 34 of silica-based composite oxide fibers can be obtained. The silica-based composite oxide fiber produced by the melt blow method has an average fiber diameter of 1 to 20 μm, preferably 1 to 8 μm, more preferably 2 to 6 μm, as compared with fibers produced by melt spinning. It can be thin. Thereby, the surface area of a fiber can also be enlarged and catalyst activity increases. Moreover, the flat nonwoven fabric manufactured by a melt blow method has a long fiber compared with the short fiber manufactured by the melt spinning method about 40-50 mm in length made into the nonwoven fabric by the needle punch method. As a result, the nonwoven fabric has high strength (tensile strength of 2N or more) and has sufficient pleatability when processed into a filter or the like.

The basis weight and thickness of the flat nonwoven fabric 41 are not particularly limited, but those having a basis weight of 50 to 500 g / m ² and a thickness of preferably 0.5 to 20 mm are used. The thickness can be adjusted by laminating a nonwoven fabric as necessary. If the thickness is less than 0.5 mm, the amount of photocatalyst itself is too small to obtain a sufficient water purification effect. When it is thicker than 20 mm, the flat nonwoven fabric 41 becomes resistance, pressure loss increases, and water treatment becomes difficult. The shape of the flat nonwoven fabric is not particularly limited, but can be round, square or the like according to the shape of the fluid tank into which the flat nonwoven fabric 41 is inserted. It can also be corrugated.

  According to the manufacturing method of the flat nonwoven fabric 41 as described above, there is no bridging between fibers, and the photocatalyst fiber having a structure in which photocatalyst components such as titanium oxide are densely precipitated on the surface of each fiber. A flat nonwoven fabric 41 is obtained. Moreover, since this photocatalyst fiber does not depend on the conventional technique of coating, there is no problem that the photocatalyst component on the fiber surface falls off. Furthermore, since the flat nonwoven fabric 41 made of fibers has a structure in which each fiber has a certain amount of gaps and dispersed therein, the contact area between the processing fluid and the photocatalyst becomes very large. Generally, in order to fully exploit the function of the photocatalyst, it is necessary to increase the light irradiation efficiency to the photocatalyst and the contact efficiency with the processing fluid.

  The surface of the photocatalyst fiber is platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), gold (Au), silver (Ag), copper (Cu), iron (Fe), nickel (Ni ), Zinc (Zn), gallium (Ga), germanium (Ge), indium (In), and tin (Sn) are preferably supported by at least one metal.

  The method for supporting the metal is not particularly limited, and corresponds to the band gap of the metal oxide constituting the second phase while contacting the liquid containing metal ions of the metal and the silica-based composite oxide fiber. By irradiating light having energy higher than energy, the reduced metal particles can be supported on the reduction site (non-irradiated surface) of the metal oxide. For example, when the second phase is anatase-type titanium oxide, its band gap is 3.2 eV, and therefore, by irradiating light having a corresponding energy, that is, a wavelength of 387 nm or less, the surface of the titanium oxide particles. Metal particles can be supported on the substrate.

Hereinafter, examples of the water purification apparatus according to the present invention will be described.

(Production Example 1)
First, titanium oxide / silica fibers were produced as flat nonwoven fabrics used in the examples. That is, 2.5 liters of anhydrous toluene and 400 g of metallic sodium were placed in a 5-liter three-necked flask and heated to the boiling point of toluene under a nitrogen gas stream, and 1 liter of dimethyldichlorosilane was added dropwise over 1 hour. After completion of the dropwise addition, the mixture was heated to reflux for 10 hours to form a precipitate. This precipitate was filtered, first washed with methanol and then with water to obtain 420 g of white powder of polydimethylsilane. Polydimethylsilane (250 g) was charged into a three-necked flask equipped with a water-cooled reflux condenser, and heated and reacted at 420 ° C. for 30 hours under a nitrogen stream to obtain polycarbosilane having a number average molecular weight of 1200.

  After adding 100 g of toluene and 64 g of tetrabutoxytitanium to 16 g of polycarbosilane, preheated at 100 ° C. for 1 hour, slowly raised to 150 ° C., distilled off toluene, allowed to react for 5 hours, and further up to 250 ° C. The temperature was raised and reacted for 5 hours to synthesize modified polycarbosilane. In order to intentionally allow the low molecular weight organometallic compound to coexist with the modified polycarbosilane, 5 g of tetrabutoxytitanium was added to obtain a mixture of the modified polycarbosilane and the low molecular weight organometallic compound.

  After the mixture of the modified polycarbosilane and the low molecular weight organometallic compound was dissolved in toluene, the mixture was charged into a glass spinning apparatus, the interior was sufficiently purged with nitrogen, and the temperature was raised to distill off the toluene. Melt spinning was carried out at 0 ° C. The spun fiber was heated to 150 ° C. stepwise in air and infusibilized, and then fired in air at 1200 ° C. for 1 hour to obtain a nonwoven fabric composed of titanium oxide / silica fibers.

(Production Example 2)
The titanium oxide / silica fiber non-woven fabric obtained in Production Example 1 was immersed in a palladium plating solution (Paradex: manufactured by Takanaka Tanaka Co., Ltd.) having a palladium concentration of 2.5 ppm, and ultraviolet light having a wavelength of 351 nm was an intensity of 4 mW / cm 2. For 4 hours. After irradiation, the fiber was taken out, washed with water, and further dried to obtain a palladium-supported titanium oxide / silica fiber nonwoven fabric according to Example 2. From the results of the weight measurement, the amount of palladium supported was 0.05% by weight.

Example 1
A photocatalyst cartridge including the flat nonwoven fabric shown in FIG. 4 is prepared using the nonwoven fabric made of titanium oxide / silica fibers obtained in Production Example 1, and contains an organic substance using the water purification device shown in FIG. Treated water was treated. The ultraviolet lamp used is GL16KZF (output: 16W) manufactured by Sankyo Electric, and the cover member is made of synthetic quartz. The output was 16 W, and four ultraviolet lamps were used. The wavelength of the ultraviolet lamp emits both 254 nm and 185 nm. The distance between the ultraviolet lamp and the photocatalyst cartridge was 50 mm, and the average ultraviolet intensity of the flat nonwoven fabric surface was 4 mW / cm ² . The ultraviolet intensity was measured using a UVR-2 ultraviolet illuminometer manufactured by TOPCON, and nine locations were measured from the center to the end of the flat nonwoven fabric surface, and this average value was defined as the average ultraviolet intensity.

The treated water was prepared by dissolving oxalic acid with ion-exchanged water to obtain a 250 ppm oxalic acid aqueous solution. In the microbubble injection tank, microbubbles were generated in the 250 ppm oxalic acid treatment solution at 20-23 L / min. The average dissolved oxygen saturation in the treatment solution was 110%. The dissolved oxygen amount was measured using a HORIBA D-50 dissolved oxygen meter, and the saturated dissolved oxygen amount was calculated from the temperature and the dissolved oxygen amount in water.
The oxalic acid treatment solution 60L was circulated at 5 L / min using the water purification device. As a result of studying under these conditions, 98% of oxalic acid could be decomposed with an energy consumption of 8 Wh / L.

(Example 2)
Using the nonwoven fabric made of palladium-supported titanium oxide / silica fibers obtained by the method described in Production Example 2, the same conditions as in Example 1 were used for examination. A treatment solution 60 L containing 250 ppm of oxalic acid was circulated at 5 L / min. As a result, 90% of oxalic acid could be decomposed at an energy consumption of 8 Wh / L.

(Comparative Example 1)
A non-woven fabric made of titanium oxide / silica fiber obtained by the method described in Production Example 1 was used, and examination was performed under the same conditions as in Example 1 except that the microbubble injection tank was not passed. A treatment solution 60 L containing 250 ppm of oxalic acid was circulated at 5 L / min. As a result, the energy consumption was 8 Wh / L and only 50% oxalic acid could be decomposed, and the purification ability was extremely low.

(Comparative Example 2)
A non-woven fabric made of palladium-supported titanium oxide / silica fibers obtained by the method described in Production Example 2 was used, and examination was performed under the same conditions as in Example 2 except that the microbubble injection tank was not passed. A treatment solution 60 L containing 250 ppm of oxalic acid was circulated at 5 L / min. As a result, energy consumption was 8 Wh / L, and only 70% oxalic acid could be decomposed, and the purification ability was extremely low. The following table summarizes the results.

本発明のマイクロバブルを用いた水浄化装置は、極めて優れた蓚酸の分解性能を示すことがわかる。

It can be seen that the water purification apparatus using the microbubbles of the present invention exhibits extremely excellent oxalic acid decomposition performance.

It is a conceptual diagram of the water purification apparatus of this invention. It is a conceptual diagram of the microbubble injection | pouring tank which concerns on this invention. It is a conceptual diagram of the photocatalyst decomposition tank which concerns on this invention. It is a conceptual diagram of the photocatalyst cartridge which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Water purification apparatus 11 Treated water inlet 12 Water supply line 13 Treated water outlet 20 Microbubble injection tank 21 Microbubble generator inlet 22 Microbubble generator outlet 23 Microbubble generator 30 Photocatalytic decomposition tank 31 Flow tank 32 Flat photocatalyst nonwoven fabric cartridge 33 UV lamp 41 Flat nonwoven fabric 42 Wire mesh

Claims (7)

  A water purification method comprising injecting air microbubbles into treated water containing an organic substance, and then contacting the treated water with a photocatalyst having titanium oxide on the surface while irradiating ultraviolet rays.   The water purification method according to claim 1, wherein the photocatalyst is a non-woven fabric of photocatalyst fibers having titanium oxide on the surface.   The water purification method according to claim 1, wherein the ultraviolet rays irradiated to the photocatalyst have peak wavelengths at 180 to 190 nm and 250 to 260 nm.   A water purification apparatus comprising: a microbubble injection tank for injecting air microbubbles into treated water containing organic matter; and a photocatalytic decomposition tank for decomposing organic matter in the treated water flowing out of the microbubble injection tank with a photocatalyst.   5. The water according to claim 4, wherein the photocatalytic decomposition tank has a flat non-woven fabric of photocatalyst fibers having titanium oxide on the surface and an ultraviolet lamp arranged substantially perpendicularly to the flow direction of the treated water. Purification equipment.   The photocatalyst fiber is composed of a composite oxide fiber of an oxide phase (first phase) mainly composed of a silica component having a photocatalytic function and a metal oxide phase (second phase) containing Ti. 6. The water purification apparatus according to claim 5, wherein the metal oxide is a silica-based composite oxide fiber in which the Ti content of the metal oxide is increasing in a slanting manner toward the surface layer of the fiber.   On the surface of the photocatalytic fiber, platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), gold (Au), silver (Ag), copper (Cu), iron (Fe), nickel (Ni ), Zinc (Zn), gallium (Ga), germanium (Ge), indium (In), and tin (Sn), at least one metal is supported. apparatus.

Images