JP2010022936A - Apparatus and method for producing ultrapure water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and method for ultrapure water which efficiently, safely, and inexpensively decompose organic materials existing in water with low energy consumption. <P>SOLUTION: The apparatus for producing ultrapure water is provided with a pretreatment device, an ion exchanger, a reverse osmosis unit, an organic material decomposition device D, a deaerator, an ion adsorption device, and an ultrafilter. The organic material decomposition device D is provided with: a fluid tank 10 for making water to be treated flow in one direction; a photocatalytic cartridge 30 provided with a flat nonwoven fabric comprising a photocatalytic fiber containing titanium oxide on the surface; and an ultraviolet lamp 20 capable of emitting ultraviolet light having a peak wavelength ranging 180-190 nm and 250-260 nm. The flat nonwoven fabric is parallel with the longitudinal direction of the ultraviolet ray lamp. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an ultrapure water production apparatus and an ultrapure water production method including an apparatus for bringing a photocatalyst and water containing an organic substance into contact with each other under ultraviolet irradiation and decomposing and removing the organic substance by a photocatalytic reaction.

  In recent years, the amount of ultrapure water used for cleaning has been remarkably increased in semiconductor manufacturing plants and liquid crystal manufacturing plants. Therefore, it is required to produce ultrapure water with low energy. However, in order to produce ultrapure water, it is necessary to decompose a small amount of soluble organic substances contained in water by ultraviolet irradiation or the like, and such decomposition requires a great deal of energy.

  As an ultrapure water production apparatus, Patent Document 1 describes a method in which an ion exchange treated primary treated water is irradiated with ultraviolet rays and then subjected to a finishing treatment in a mixed bed composed of a cation exchange resin and an anion exchange resin. Has been. According to this method, a small amount of soluble organic matter remaining in the primary treated water is decomposed and ionized by ultraviolet rays, and this ionized material is removed in the mixed ion exchange resin bed, so that pure water with a low concentration of organic matter is produced. can do. Patent Document 2 describes that a trace amount of organic substances can be efficiently decomposed and removed by setting the wavelength of ultraviolet rays irradiated to water to 180 to 190 nm. However, even in these methods, high energy is required for the decomposition of organic substances, and further higher efficiency is desired.

  In Patent Document 3, hydrogen peroxide or ozone is added to water to be treated, and in the presence of an anatase type photocatalyst including anatase type or rutile type, a low-pressure ultraviolet lamp having a wavelength of 254 nm, 254 nm and 185 nm, respectively. One or more ultraviolet lamps selected from a low-pressure ultraviolet lamp having a wavelength, a low-pressure ultraviolet lamp having a wavelength of 254 nm, 194 nm, and 185 nm, and a medium-pressure ultraviolet lamp having a continuous wavelength of 400 nm or less. It describes that organic substances are decomposed by ultraviolet irradiation.

In Patent Document 4, as a method for reducing the energy required for the production of ultrapure water, ultrapure water provided with an organic substance removal device comprising an organic decomposition means and an ion adsorption means arranged in order along the flow path of the water to be treated. In the manufacturing apparatus, the organic substance decomposing means is a tube made of an ultraviolet light transmitting material that becomes a flow path of water to be treated, a photocatalyst layer that is deposited on a side of the tube that contacts the water to be treated, and a photocatalyst coating of the tube. There is described an ultrapure water production apparatus comprising a light emitting diode for irradiating ultraviolet rays disposed on the opposite side to the photocatalyst layer.
Japanese Patent Publication No.54-19227 JP-A-1-164488 JP-A-10-151450 JP 2007-136372 A

  However, in the method described in Patent Document 3, although the energy required for the production of ultrapure water is reduced, a dangerous toxic substance such as hydrogen peroxide or ozone is used, which causes a problem in safety. Moreover, the cost regarding hydrogen peroxide and ozone is needed separately, and there exists a problem also in cost. In the method described in Patent Document 4, although a long-life light emitting diode is used as an ultraviolet light source, the replacement cost and energy consumption of the ultraviolet light source can be greatly reduced. Since the intensity is significantly smaller than that of the low-pressure ultraviolet lamp or the medium-pressure ultraviolet lamp, there is a problem that the resolution of the organic matter is extremely low. In addition, the photocatalyst is simply deposited on the surface of the tube, the contact efficiency between the photocatalyst and the water to be treated is extremely poor, and it is difficult to obtain sufficient organic matter resolution even if the ultraviolet intensity is increased. Has the problem of being.

  Then, an object of this invention is to provide the ultrapure water manufacturing apparatus and the ultrapure water manufacturing method which can decompose | disassemble the organic substance which exists in water efficiently and safely with low energy consumption and cost.

  In order to achieve the above object, the present inventors have conducted extensive research, and as a result, the ultraviolet irradiation means disposed so as to be parallel to the flat nonwoven fabric made of photocatalyst fiber containing titanium oxide on the surface has a flat shape. It has been found that by irradiating a nonwoven fabric with ultraviolet light having a peak wavelength between 180 to 190 nm and 250 to 260 nm, organic substances present in water can be efficiently and safely decomposed with low energy consumption and cost. That is, the present invention provides a pretreatment device that removes at least suspended substances, an ion exchange device that removes at least one of anions and cations, a reverse osmosis device that removes at least fine particles and colloid materials, and a decomposition of soluble organic matter. An ultrapure water production apparatus comprising: an organic substance decomposing apparatus for removing; a degassing apparatus for removing dissolved gas; an ion adsorption apparatus for removing ionized substances; and an ultrafiltration apparatus for removing at least fine particles. The organic matter decomposing apparatus comprises a flow tank for flowing the water to be treated in one direction, a flat nonwoven fabric made of photocatalytic fibers containing titanium oxide on the surface, and ultraviolet rays having peak wavelengths at 180 to 190 nm and 250 to 260 nm, respectively. An ultraviolet irradiation means having a shape extending in the longitudinal direction, the surface of the flat nonwoven fabric and the length of the ultraviolet irradiation means. Ultrapure water production apparatus which is a parallel to the direction.

  The present invention also includes a first step for removing at least suspended substances, a second step for removing at least one of anions and cations by ion exchange, a third step for removing at least fine particles and colloidal substances, While flowing the treated water, a flat nonwoven fabric made of photocatalyst fiber containing titanium oxide was passed through the surface, and it had a shape extending in the longitudinal direction, and was installed so that the longitudinal direction and the flat nonwoven fabric were parallel to each other A fourth step of irradiating the flat nonwoven fabric with ultraviolet light having peak wavelengths of 180 to 190 nm and 250 to 260 nm from the ultraviolet irradiation means to decompose and remove soluble organic substances in the water to be treated, and to remove dissolved gas. A fifth step, a sixth step of removing the ionized substance ionized in the fourth step by adsorption, and at least fine particles by ultrafiltration A seventh step of removed by a method for producing ultrapure water, characterized in that it comprises a.

  As described above, according to the present invention, it is possible to provide an ultrapure water production apparatus and an ultrapure water production method capable of efficiently and safely decomposing organic substances present in water with low energy consumption and cost. .

  Next, an embodiment of the ultrapure water production apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an example of the configuration of the ultrapure water production apparatus according to the present embodiment. The ultrapure water production apparatus according to the present embodiment includes a pretreatment apparatus A capable of removing suspended substances, an ion exchange apparatus B capable of removing anions and cations, and a reverse osmosis apparatus capable of removing fine particles and colloidal substances. C, organic substance decomposing apparatus D capable of decomposing and removing soluble organic substances, degassing apparatus E capable of removing dissolved gas, ion adsorption apparatus F capable of removing ionized substances ionized by the organic substance decomposing apparatus, and fine particles Are disposed in order along the flow path of the water to be treated.

  In the ultrapure water production apparatus according to the present embodiment, the pretreatment apparatus A is a coagulation filtration apparatus, and may include an activated carbon filter for removing residual chlorine and the like in the water to be treated. The ion exchange apparatus B is a two-bed / three-column ion exchange apparatus including a cation exchange resin tower, a decarboxylation tower, and an anion exchange resin tower. The reverse osmosis device C is a device including an RO membrane module. The degassing device E is a nitrogen gas addition type vacuum degassing device. The ion adsorption device F is an anion and cation exchange resin tower. The ultrafiltration device G is a filtration device including an ultrafiltration membrane.

  In the ultrapure water production apparatus according to the present embodiment, the organic matter decomposing apparatus D causes the water to be treated to flow from the inlet 55 formed on the bottom surface to the outlet 57 formed on the upper surface, as shown in FIG. Between the photocatalyst cartridge 30 and the three photocatalyst cartridges 30 which are accommodated in the fluid tank 10 and are accommodated in the fluid tank 10 and are installed in parallel to each other so that the surface of the water to be treated intersects perpendicularly. The ultraviolet lamp 20 disposed so that the surface of the flat nonwoven fabric 31 and the longitudinal direction of the ultraviolet lamp 20 are parallel to each other, and the microbubble generator 40 that injects microbubbles into the water to be treated flowing from the inlet 51 It has.

  The cover member constituting the outer surface of the ultraviolet lamp 20 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 ultrapure water production apparatus according to the present embodiment, the ultraviolet lamp 20 irradiates ultraviolet rays having peak wavelengths at 180 to 190 nm and 250 to 260 nm by making the material of the cover member special as described above. It is configured to be possible. The ultraviolet rays irradiated from the ultraviolet irradiation lamp 20 have a peak wavelength at 180 to 190 nm, preferably 185 nm, and a peak wavelength at 250 to 260 nm, preferably 254 nm. Each ultraviolet lamp 20 is disposed between each photocatalyst cartridge 30, two in total, and a total of four are disposed between each photocatalyst cartridge 30, so that ultraviolet rays are emitted from both sides of the flat nonwoven fabric 31 provided in the photocatalyst cartridge 30. Irradiation is possible. The ultraviolet lamps 20 are arranged in parallel so that their axial directions are parallel to the photocatalyst cartridge 30. In the present embodiment, the cover member of the ultraviolet irradiation lamp 20 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 irradiation lamps 20 is determined according to the required water quality, the amount of unnecessary organic substances contained in the treated water, and the like.

  The microbubble generator 40 is a dissolved oxygen concentration increasing means for increasing the dissolved oxygen concentration in the water to be treated. The dissolved oxygen concentration increasing means is a mechanism for increasing the dissolved oxygen concentration in water by blowing air or oxygen into the water, and examples thereof include a microbubble generator and aeration (bubble generator). Is preferred. The microbubble generator 40 includes a storage tank 42 that stores the liquid to be processed that has been processed by the reverse osmosis device, and a microbubble generator 44. The storage tank 42 is provided with an inflow path 51 through which treated water can flow into the storage tank 42 and an outflow path 53 through which treated water within the storage tank 42 can flow out. The storage tank 42 and the microbubble generator 44 are connected by an inflow path 46 and an outflow path 48, and have a circulation structure in which treated water can be circulated. The microbubble generator 44 is an apparatus capable of generating microbubbles having a particle diameter of 50 μm or less, preferably 30 μm or less. Microbubbles exhibit different properties from normal bubbles, for example, the bubbles are rising at a much slower rate than normal bubbles, and the self-pressurization effect enables supersaturated dissolution of gas in water. have. Examples of microbubble generation methods include pressure dissolution type, ejector type, cavitation type, and swivel type, and the characteristics of microbubbles depend on the diameter and amount of bubbles generated, so they are relatively large and fine. The pressure dissolution type capable of generating simple bubbles is preferable. Microbubbles are generally air bubbles, but are more effective when oxygen is used.

  As shown in FIG. 3, each photocatalyst cartridge 30 includes a flat nonwoven fabric 31 and a pair of wire meshes 32, and the flat nonwoven fabric 31 is sandwiched between a pair of stainless steel wire meshes 32. Thus, by using the wire mesh 32 as a support material and making it into a cartridge shape, the flat nonwoven fabric 31 with a deteriorated photocatalytic function can be easily replaced. Desorption can be facilitated by providing a multi-stage photocatalyst cartridge with a connecting structure using a frame or the like. In the present embodiment, the number of the flat nonwoven fabrics 31 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 31 was fixed to the flow tank 10 as the photocatalyst cartridge 30, you may install by another means. Further, in the present embodiment, each photocatalyst cartridge 30 is installed such that its surface intersects perpendicularly with the flow direction of water, but it is sufficient that the flowing water passes through the flat nonwoven fabric 31 efficiently. May be installed at an angle of around 10 °, preferably around 5 °.

  The flat nonwoven fabric 31 is a silica-based composite oxide fiber composed of a composite oxide phase of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing titanium. The photocatalyst fiber in which the abundance ratio of titanium of the metal oxide constituting the second phase increases in a gradient toward the surface layer of the fiber.

  The surface of the photocatalytic fiber may be platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), gold (Au), silver (Ag), copper (Cu), iron (Fe), if necessary. One or more of nickel (Ni), zinc (Zn), gallium (Ga), germanium (Ge), indium (In), and tin (Sn) may be supported. The supporting method is not particularly limited, but light having an energy equal to or higher than the energy corresponding to the band gap of the metal oxide constituting the second phase while contacting the liquid containing the supported metal ions and the photocatalytic fiber. Can be carried by irradiation.

  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 titanium and plays an important role in developing the photocatalytic function. An example of the metal constituting the metal oxide is titanium. The metal oxide may be a simple substance, or may be a co-melting compound or a substance in which a substitutional solid solution is formed with a specific element, but is preferably titania. 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 titanium 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 composition gradient 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.

In organic decomposition apparatus, 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.

  Next, the manufacturing method of the photocatalyst fiber which has an inclination structure is demonstrated.

(Melt spinning method)
Photocatalytic fibers are mainly of the general formula

(However, R in the formula represents a hydrogen atom, a lower alkyl group or a phenyl group.) A polycarbosilane having a main chain skeleton represented by the following formula is modified with an organometallic compound. A process for obtaining a modified polycarbosilane having the above structure or a mixture of a modified polycarbosilane and an organometallic compound, a process B for melt spinning, a process C for infusible treatment, and firing in air or oxygen It can manufacture by the D process to do.

  Step A is a step of 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 method for producing the modified polycarbosilane is very similar to JP-A-56-74126, but it is necessary to carefully control the bonding state of the functional groups described therein.

  The modified polycarbosilane is mainly composed 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 ″ m (M Is a metal element, R ′ is an alkyl group having 1 to 20 carbon atoms or a phenyl group, R ″ is acetylacetonate, and m and n are integers greater than 1). Is.

  In order to produce a photocatalytic 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 bifunctional 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 function reacts and an unreacted organometallic compound remains, conversely, a decrease in melt viscosity is observed.

  In order to produce a photocatalytic 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.

  In step B, the modified polycarbosilane obtained in step A or a mixture of modified polycarbosilane and a low molecular weight organometallic compound (hereinafter sometimes referred to as a precursor) is melted to prepare a spinning dope. In some cases, this is filtered to remove substances that are harmful when spinning, such as microgel and impurities, and this is spun by a commonly used synthetic fiber spinning device. 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.

  In addition to the spinning, the modified polycarbosilane obtained in Step A, or a mixture of the modified polycarbosilane and a low molecular weight organometallic compound is used, for example, benzene, toluene, xylene or other modified polycarbosilane and other low molecular weight compounds. Synthetic fibers that are usually used after dissolving the organometallic compound in a solvent that can be melted to prepare a spinning stock solution, and in some cases filtering it to remove harmful substances such as macrogel and impurities. Spinning may be performed while controlling the winding speed by a dry spinning method with a spinning device.

  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, or organosilicon compound gas, solidification of fibers in the spinning cylinder can be controlled.

  In Step C, the spun fiber obtained in Step B is preheated in an oxidizing atmosphere under the action of tension or no tension to infusibilize the spun fiber. The C step is performed for the purpose of preventing the fibers from melting and adhering to adjacent fibers during the firing of the D step. 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 addition, it is thought that the bleed-out to the fiber surface of the low molecular weight substance contained in a raw material advances in the C process and the B process, and the base | substrate of the target gradient composition is formed.

  In Step D, the fiber infusible in Step C is baked in an oxidizing atmosphere at a temperature range of 500 to 1800 ° C. under tension or no tension, and the target is an oxidation mainly composed of a silica component. It consists of a composite oxide phase of a physical phase (first phase) and a metal oxide phase containing titanium (second phase), and the proportion of titanium in the metal oxide that constitutes the second phase toward the surface layer is inclined. The photocatalytic fiber that increases to a maximum In Step D, 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, a temperature at which no problem occurs in the target gradient composition and crystal structure and a processing time are selected.

  In addition, in order to make a photocatalyst fiber into a flat nonwoven fabric, after making the photocatalyst fiber which has a photocatalyst function obtained by the said manufacturing method into a short fiber, it can be set as a flat nonwoven fabric by performing a needle punch.

(Melt blow method)
The flat nonwoven fabric melts the precursor obtained in Step A using a melt blow method, discharges the melt from the spinning nozzle, and spouts heated nitrogen gas from the periphery of the spinning nozzle. The nonwoven fabric can be formed by collecting the spun fibers in a receiver arranged at the lower part of the spinning nozzle, and then the nonwoven fabric is infusible and then fired in an oxidizing atmosphere.

  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 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 the jet gas, but nitrogen needs to be used to spin the precursor obtained in the step A. 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 infusibilization treatment and firing (step C and step D) as in the melt spinning method, whereby a nonwoven fabric made of photocatalytic fibers is obtained. The photocatalyst fiber produced by the melt blowing method has an average fiber diameter of 1 to 20 μm, preferably 1 to 8 μm, more preferably 2 to 6 μm, and is thinner than the fiber produced by the melt spinning method. be able to. 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 are not particularly limited, but it is usually preferable that the basis weight is 50 to 500 g / m ² and the thickness is 0.5 to 20 mm. 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 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, etc. according to the shape of the flow tank into which the flat nonwoven fabric is inserted, and corrugated to increase the surface area of the flat nonwoven fabric. It can also be made into a shape.

  According to the manufacturing method of the flat nonwoven fabric 31 as described above, there is no bridging between fibers, and the photocatalyst fiber has a structure in which photocatalytic components such as titania are densely deposited on the surface of each fiber. A flat nonwoven fabric 31 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 31 made of the fibers has a structure in which each fiber is dispersed with a certain amount of voids, 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.

  Next, a method for producing ultrapure water according to the present embodiment will be described.

(First step)
First, suspended substances contained in tap water, ground water, etc., which are to-be-treated water, are removed by a coagulation filtration device. Thereby, the load of the ion exchange apparatus and reverse osmosis apparatus in a back | latter stage can be reduced. The treated water treated by the pretreatment device is supplied to the ion exchange device.

(Second step)
Most of the inorganic components contained in the water to be treated are removed from the water to be treated supplied to the ion exchange device by ion exchange. The treated water treated by the ion exchange device is supplied to the reverse osmosis device.

(Third step)
The treated water supplied to the reverse osmosis device is passed through the RO membrane module and supplied to the organic matter decomposition device. The water treated with the reverse osmosis device has a TOC (organic concentration) of about 20 ppb, and most of the organic matter is removed compared to the TOC of raw water (about 1 ppm in the case of tap water). Since the TOC of ultrapure water used in the manufacturing process is required to be 1 ppb or less, the remaining trace amount of organic matter is decomposed and removed by the following organic matter decomposing apparatus.

(4th process)
The to-be-processed water processed in the reverse osmosis apparatus is supplied to the storage tank 42 from the inflow path 51, as FIG. 2 shows. The microbubble generating unit 44 generates microbubbles, brings the water to be treated and microbubbles into contact with each other by aeration, and injects the microbubbles into the water to be treated. Since the storage tank 42 circulates between the microbubble generator 44 via the inflow path 46 and the outflow path 48, the microbubbles are injected into the water to be treated stored therein, and the dissolved oxygen concentration increases. To do. The dissolved oxygen concentration of the liquid to be treated supplied to the fluid tank 10 is preferably 80 to 150% in terms of saturation. Oxygen exceeding the saturation amount of dissolved oxygen can be dissolved by the self-pressurizing effect that is a characteristic of microbubbles.

  The treated water into which the microbubbles are injected is supplied from the inlet 55 to the fluid tank 10 through the supply path 53. In order to purify the treated water containing unnecessary organic substances, first, the treated water is poured from the inlet 55 of the fluidized tank 10. The treated water that has been poured is discharged from the outlet 57 through the fluid tank 10. Since the flat nonwoven fabric 31 has a structure in which each fiber has a certain amount of voids and is dispersed, the contact area with the photocatalyst is very large when water passes through. For this reason, radicals are efficiently generated by the flat nonwoven fabric 31 having a photocatalytic function, and unnecessary organic substances are decomposed. Radiation can be generated more efficiently by irradiating both the front and back surfaces of the flat nonwoven fabric 31 made of photocatalytic fibers with ultraviolet rays. Moreover, unnecessary organic substances are decomposed by directly irradiating water with 185 nm ultraviolet rays.

  Usually, in an organic matter decomposing apparatus using a titania 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 titania photocatalysts can be excited at wavelengths of 387 nm or less, and these lamps are easily available as products. In the organic matter decomposing apparatus D, high decomposition efficiency can be obtained by using ultraviolet rays that have not been used in the past and making the photocatalyst have a predetermined arrangement structure. That is, in the ultrapure water production apparatus according to the present invention, a flat nonwoven fabric made of photocatalytic fibers and an ultraviolet ray having peak wavelengths at 180 to 190 nm and 250 to 260 nm, which are installed in parallel with the flat nonwoven fabric. Therefore, 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 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 effect can be kept high. The efficiency of such decomposition is advantageous when the concentration of dissolved oxygen in the water to be treated is high. By the above processing by the organic matter decomposing apparatus D, the TOC can be reduced to 1 ppb or less. The treated water treated by the organic matter decomposing apparatus is supplied to the deaeration apparatus.

(5th process)
Dissolved gas such as dissolved oxygen is removed from the water to be treated supplied to the deaerator. The water to be treated treated by the deaeration device is supplied to the ion adsorption device.

(Sixth step)
From the water to be treated supplied to the ion adsorbing device, the organic matter is not completely decomposed in the organic matter decomposing device, and the ionized substance remaining in a minute amount as the ionized substance is removed. For example, isopropyl alcohol (IPA) is mostly completely decomposed into carbon dioxide and water, but a trace amount may remain in water as an incompletely decomposed product such as an organic acid (ionized substance) such as acetic acid or formic acid. is there. The ion adsorption apparatus plays a very important role in adsorbing and removing such ionized substances and further reducing the TOC. The treated water treated by the ion adsorption device is supplied to the ultrafiltration device.

(Seventh step)
The treated water supplied to the ion adsorption device is treated by the ultrafiltration device. Through the above treatment, ultrapure water having a low TOC is obtained.

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

(Production Example 1)
A 5-liter three-necked flask was charged with 2.5 liters of anhydrous toluene and 400 g of metallic sodium, 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. The precipitate was filtered, 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.

  To 100 g of polycarbosilane synthesized by the above method, 100 g of toluene and 64 g of tetrabutoxytitanium are added, preheated at 100 ° C. for 1 hour, then slowly heated to 150 ° C. to distill off the toluene and reacted for 5 hours. The mixture was further heated to 250 ° C. 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. in the air stepwise to be infusible, and then fired in air at 1200 ° C. for 1 hour to obtain a titania / silica fiber as a photocatalyst fiber.

  In the photocatalyst fiber obtained in Production Example 1, the proportion of the first phase was 80% by weight and the proportion of the second phase was 20% by weight. The abundance ratio was determined by fluorescent X-ray analysis. The titania crystal particles contained in the second phase were 8 nm. The particle diameter was determined by TEM (transmission electron microscope observation). From the surface of the photocatalyst fiber, the existing ratio of titanium metal oxide was inclined at a depth of 300 nm. The inclination depth was determined by Auger electron spectroscopy.

Example 1
The titania / silica fiber obtained in Production Example 1 was used as a flat nonwoven fabric, and a photocatalyst cartridge including the same was produced, and the organic matter decomposing apparatus shown in FIG. 4 was produced. The output of the ultraviolet lamp was 60 W, and 24 lamps were used. The wavelength of the ultraviolet lamp emits both 254 nm and 185 nm. The distance between the ultraviolet lamp and the flat nonwoven fabric was 90 mm, and the average ultraviolet intensity of the flat nonwoven fabric surface was ² mW / cm ² . Water is treated with a known coagulation filtration device, a two-bed three-column ion exchange device, and a reverse osmosis membrane device, and then treated with this organic matter decomposition device, followed by a known deaeration device, ion adsorption device, and ultrafiltration device. Ultrapure water was obtained by processing with a filtration device. The treatment speed was adjusted so that the finally obtained TOC of ultrapure water was about 0.5 ppb. In this case, the processing speed was 6.5 m ³ / h, and the energy consumption related to the organic matter decomposition apparatus was 0.32 kwh / m ³ .

(Example 2)
The organic substance decomposition apparatus was equipped with a microbubble generator, and the same treatment as in Example 1 was performed except that the dissolved oxygen concentration in the treated water was 7.5 ppm (in the case of no microbubble generator: 6.0 ppm). . The treatment speed was adjusted so that the finally obtained TOC of ultrapure water was about 0.5 ppb. In this case, the processing speed was 7.5 m ³ / h, and the energy consumption related to the organic matter decomposition apparatus was 0.27 kwh / m ³ .

(Example 3)
The organic substance decomposition apparatus was equipped with a microbubble generator, and the same treatment as in Example 1 was performed except that the dissolved oxygen concentration in the treated water was 8.7 ppm (in the case of no microbubble generator: 6.0 ppm). . The treatment speed was adjusted so that the finally obtained TOC of ultrapure water was about 0.5 ppb. The processing speed in this case was 8.7 m ³ / h, and the energy consumption related to the organic matter decomposition apparatus was 0.24 kwh / m ³ .

(Comparative Example 1)
With reference to the method described in the example of Japanese Patent Laid-Open No. 10-151450, 24 stainless steel tubes having a diameter of 250 mm and a length of 1500 mm each include 24 low-pressure ultraviolet lamps of 65 W that emit wavelengths of 254 nm, 194 nm, and 184 nm. An organic matter decomposition apparatus was produced. As the photocatalyst, anatase titania supported on a translucent alumina plate was inserted into the organic matter decomposing apparatus. The weight of the photocatalyst with respect to the internal volume of the organic substance decomposition apparatus was 80 ppm. In the same manner as in Example 1, except for the organic matter decomposing apparatus, the treated water was treated with a known coagulation filtration device, a two-bed three-column ion exchange device, a reverse osmosis membrane device, and a degassing device, and then treated with this organic matter decomposing device Subsequently, ultrapure water was obtained by treating with a known ion adsorption device and ultrafiltration device. The treatment speed was adjusted so that the finally obtained TOC of ultrapure water was about 0.5 ppb. The processing speed in this case was 4.7 m ³ / h, and the energy consumption related to the organic matter decomposition apparatus was 0.47 kwh / m ³ .

It is a figure which shows an example of a structure of a pure water manufacturing apparatus. It is a conceptual diagram of an organic matter decomposition | disassembly apparatus. It is an enlarged view of a photocatalyst cartridge. It is a conceptual diagram of the organic substance decomposition | disassembly apparatus used in the Example.

Explanation of symbols

D Organic matter decomposing apparatus 10 Fluid tank 20 Ultraviolet lamp 30 Photocatalyst cartridge 31 Flat sheet nonwoven fabric 32 Wire mesh 40 Microbubble generator 42 Storage tank 44 Microbubble generator

Claims (13)

A pretreatment device for removing at least suspended substances, an ion exchange device for removing at least one of anions and cations, a reverse osmosis device for removing at least fine particles and colloidal materials, and an organic matter decomposition device for decomposing and removing soluble organic matter And an ultrapure water production apparatus comprising a degassing device for removing dissolved gas, an ion adsorption device for removing ionized substances, and an ultrafiltration device for removing at least fine particles,
The organic matter decomposition apparatus is
A fluid tank for flowing the water to be treated in one direction;
A flat nonwoven fabric composed of photocatalytic fibers containing titanium oxide on the surface;
An ultraviolet irradiation means having a shape extending in the longitudinal direction capable of irradiating ultraviolet rays having peak wavelengths of 180 to 190 nm and 250 to 260 nm, respectively.
An apparatus for producing ultrapure water, wherein the surface of the flat nonwoven fabric is parallel to the longitudinal direction of the ultraviolet irradiation means.   The ultrapure water production apparatus according to claim 1, wherein the flat nonwoven fabric is disposed so that a surface thereof is perpendicular to a flow direction of the water to be treated.   The ultrapure water production apparatus according to claim 1 or 2, wherein the organic matter decomposition apparatus further comprises a dissolved oxygen concentration increasing means for increasing the dissolved oxygen concentration of the water to be treated.   4. The apparatus for producing ultrapure water according to claim 3, wherein the dissolved oxygen concentration increasing means is microbubble generating means.   The photocatalytic fiber is a silica-based composite oxide fiber composed of a composite oxide phase of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase containing titanium (second phase), The ultrapure water production apparatus according to any one of claims 1 to 4, wherein an abundance ratio of titanium of the metal oxide constituting the second phase increases in a slope toward the surface layer of the fiber.   The ultrapure water production apparatus according to any one of claims 1 to 5, wherein both surfaces of the flat nonwoven fabric can be irradiated with ultraviolet rays.   The ultrapure water production apparatus according to any one of claims 1 to 6, wherein the flat nonwoven fabric is detachable from the fluidized tank.   6. The apparatus for producing ultrapure water according to claim 5, wherein the existence ratio of the first phase with respect to the entire photocatalytic fiber is 98 to 40% by weight, and the existence ratio of the second phase is 2 to 60% by weight. .   The ultrapure water production apparatus according to claim 5 or 8, wherein the titanium oxide of the metal oxide constituting the second phase is inclined at a depth of 5 to 500 nm from the surface of the photocatalyst fiber.   The ultrapure water production apparatus according to claim 5, 8, or 9, wherein the metal oxide contained in the second phase is titania, and the crystal grain size of the titania is 15 nm or less. A first step of removing at least suspended matter;
A second step of removing at least one of an anion and a cation by ion exchange;
A third step of removing at least particulates and colloidal material;
While flowing the water to be treated, a flat nonwoven fabric made of photocatalyst fiber containing titanium oxide is passed through the surface, and has a shape extending in the longitudinal direction, and the longitudinal direction and the flat nonwoven fabric are installed in parallel. A fourth step of irradiating the flat nonwoven fabric with ultraviolet light having a peak wavelength at 180 to 190 nm and 250 to 260 nm from the ultraviolet irradiation means to decompose and remove soluble organic substances in the water to be treated;
A fifth step of removing dissolved gas;
A sixth step of removing the ionized substance ionized by the fourth step by adsorption;
And a seventh step of removing at least fine particles by ultrafiltration.   The method for producing ultrapure water according to claim 11, wherein in the fourth step, the water to be treated is caused to flow in a direction perpendicular to the surface of the flat nonwoven fabric. In the fourth step, the photocatalytic fiber is a silica-based composite oxidation comprising a composite oxide phase of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing titanium. The ultrapure water according to claim 11 or 12, wherein the presence ratio of titanium of the metal oxide constituting the second phase is inclined toward the surface layer of the fiber. Production method.

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