JP2008018352A - Recycle system and treatment device for plating washing water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recycle system and device for plating washing water which eliminate a decrease in a product yield due to bacteria in washing water used in plating processes, and outflow of noble metals in the washing water. <P>SOLUTION: In the recycle system and treatment device for plating washing water in an apparatus for purifying the washing water used in plating processes, molded material of nonwoven fabric made of silica-group composite oxide fiber with a photocatalytic function, consisting of an oxide phase (a first phase) mainly comprising a silica component and a metal oxide phase (a second phase) containing Ti so that the ratio of Ti present in a metal oxide gradually increases toward the surface of fabric is arranged in a plurality of stages in a reaction vessel, and brought into contact with the washing water under irradiation with active rays. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to bacteria in spent washing water by photocatalytic reaction by contacting the photocatalyst with washing water used in the plating step under ultraviolet irradiation or visible light irradiation from an actinic ray irradiator, for example, an ultraviolet irradiation lamp. The present invention relates to a plating cleaning water reuse system and a processing apparatus that can easily decompose precious metals and recover precious metals.

  Conventionally, in the purification of harmful substances using a photocatalyst, powdered titanium oxide has been mainly used as a photocatalyst. However, these powdery photocatalysts are difficult to handle, and in purification of water, titanium oxide is mixed with water, so it is necessary to separate titanium oxide from treated water.

  In order to solve this problem, a photocatalyst powder is supported on a base material. For example, as shown in Patent Document 1, a filter obtained by coating titanium oxide on a glass filter has been proposed. For example, as shown in Patent Document 2, a photocatalyst cartridge composed of a photocatalyst carrier in which a photocatalyst is carried on an aperture cross is proposed. This photocatalyst carrier has a stacked structure of hollow cone-shaped constant aperture cloths.

  However, in general, when the photocatalyst powder is supported by coating, the photocatalyst powder is likely to fall off due to contact with the object to be processed, so that the photocatalyst powder is mixed into the object to be processed. Further, as in Patent Document 2, in the method of supporting a catalyst on a cloth, bridging of fibers constituting the cloth is inevitable. As a result, it is difficult for the processing fluid to pass between the fibers, and the pressure loss increases. In order to avoid this pressure loss, a measure is taken to define a certain opening or more, or to intentionally make a hole in the catalyst carrier. In the structure of the purification device in which the vessel wall is simply coated with the photocatalyst, the contact between the photocatalyst and the object to be treated is very poor and efficient purification cannot be expected. In the purification of harmful substances by photocatalysis, it is important to improve the contact between the photocatalyst and the treatment fluid. In order to solve these problems, the present inventors have proposed an apparatus described in Patent Document 3.

  In recent years, the speed of technological innovation in the field of electronic industry is fast, and electronic circuits are becoming increasingly finer. If bacteria are contained in the washing water used in the plating process, the bacteria adhere to the product, causing a short circuit or the like, thereby deteriorating the yield of the product. For this reason, bacteria in washing water are usually sterilized by ultraviolet sterilization. In addition, precious metals such as gold may be plated in the formation of electronic circuits. In this case, the cleaning water used in the plating process contains a small amount of precious metals, from the viewpoint of effective use of resources. There is also a need for a method of collecting these. The recovery of these trace precious metals is mainly performed by an adsorption method. In other words, measures against bacteria and precious metal recovery are performed in different steps.

JP-A-8-103631 JP-A-7-227547 Japanese Patent No. 3436267

  The inactivation effect of bacteria by ultraviolet rays is widely used in various applications. However, inactivation by ultraviolet rays suppresses the ability of bacteria to grow, so that the bacteria remain in the water as they are. Therefore, the ultraviolet treatment has no effect on the yield improvement in the plating process. In addition, bacteria that have been inactivated by ultraviolet rays are known to recover their proliferation ability (photorecovery) by irradiation with near ultraviolet rays, and ultraviolet rays are not an effective means depending on the use environment. On the other hand, noble metal recovery is performed by an adsorption method, but since this is performed in a completely different process from the above-mentioned countermeasure against bacteria, it is necessary to install two types of equipment for sterilization countermeasures and noble metal recovery.

An object of the present invention is to recycle a plating cleaning water system and a plating cleaning water treatment device that can prevent the deterioration of product yield and can easily recover precious metals even when the cleaning water is repeatedly circulated. To provide.

  The present invention relates to an apparatus for purifying cleaning water used in a plating process, and a composite oxidation of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti. A non-woven fabric of silica-based composite oxide fibers having a photocatalytic function, wherein the presence ratio of Ti of the metal oxide constituting the second phase is inclined toward the surface layer of the fibers. Place the formed molding in multiple stages in the reaction vessel, purify the molded product and cleaning water by contacting them under irradiation with actinic rays, and reuse the purified cleaning water again in the plating process. Provided is a plating cleaning water reuse system.

  The present invention provides the above-described plating cleaning water reuse system in which the molded product is in a conical shape, a hollow frustum shape, or a disk shape.

  The present invention provides the above-described plating washing water reuse system used as a photocatalyst cartridge that is detachable into a reaction vessel, in which a molded product is installed in a plurality of stages in series on a connecting rod.

  The present invention provides the above-described plating cleaning water recycling system, wherein the molded product has at least one opening.

  The present invention provides the plating cleaning water recycling system in which the molded product is disposed in the reaction vessel in a direction horizontal to the central axis of the reaction vessel.

  The present invention provides the above-described plating cleaning water reuse system in which an actinic ray irradiator is provided in the reaction vessel and / or outside the reaction vessel in parallel with the central axis of the reaction vessel.

  The present invention provides the above-described reuse system for plating washing water, wherein the abundance ratio of the first phase is 98 to 40% by weight and the abundance ratio of the second phase is 2 to 60% by weight with respect to the whole fiber.

  The present invention provides the above reuse system for plating washing water in which the gradient of the Ti content of the metal oxide constituting the second phase exists at a depth of 5 to 500 nm from the fiber surface.

  The present invention provides the plating cleaning water recycling system, wherein the second phase metal oxide is titania and the crystal grain size is 15 nm or less.

  The present invention provides the above-described plating cleaning water reuse system for recovering precious metals adhering to a molded product used for purification treatment by a combustion method or a melting method.

  The present invention relates to an apparatus for purifying cleaning water used in a plating process, and a composite oxidation of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti. A non-woven fabric of silica-based composite oxide fibers having a photocatalytic function, wherein the presence ratio of Ti of the metal oxide constituting the second phase is inclined toward the surface layer of the fibers. The formed product is arranged in a plurality of stages in the reaction vessel, and the product and cleaning water are brought into contact with each other under irradiation of actinic rays, thereby reducing particulate matter derived from bacteria in the plating cleaning water, In addition, a plating cleaning water treatment device is provided that can easily collect precious metals in plating cleaning water.

  According to the present invention, from the cleaning water used in the plating process, not only the complete decomposition of bacteria in the cleaning water, but also a plating cleaning water reuse system and a processing apparatus that can be recovered by precious metals depositing on the surface of the photocatalyst. Is provided. That is, according to the present invention, it is possible to simultaneously collect a trace amount of noble metals contained in the plating washing water with one type of apparatus at the same time as reducing the particulate matter derived from bacteria that causes a decrease in product yield. A plating cleaning water reuse system and processing apparatus are provided.

  The present inventors have already succeeded in developing a purification apparatus using a photocatalyst as shown in Japanese Patent No. 3436267. The principle of the photocatalyst (mainly titania) is as follows. Excited by irradiation with light (mainly ultraviolet light), electrons in the valence band move to the conduction band. At this time, holes are generated in the valence band of titania. These holes generate active oxygen species represented by OH radicals having strong oxidizing power by taking electrons from the water around the titania. On the other hand, the electrons moved to the conduction band reduce oxygen around titania. The said purification apparatus is utilized for environmental purification | cleaning by oxidative decomposition of organic substance using such a characteristic.

  The organic substance decomposition performance of this purification device is also extremely effective against bacteria. By using this purification device, bacteria are completely oxidized and decomposed, and particulate matter derived from bacteria in water is greatly reduced. The inventors have found that this is possible. Furthermore, it has been found that by using this purification device for purification of water containing a trace amount of noble metals together with bacteria, not only the complete decomposition of bacteria but also the precious metals can be recovered by depositing on the photocatalyst surface. This is because, in the principle of the photocatalyst, electrons in the conduction band usually reduce oxygen, but when noble metal ions are present in water, they are more likely to be reduced than oxygen, so noble metal ions are present on the photocatalyst. Presumed to be precipitated by reduction. In this way, by using this purification device for plating washing water, it is possible to reduce the amount of precious metals contained in the plating washing water at the same time as reducing the particulate matter derived from bacteria that causes a decrease in product yield. This can be done with one type of device. That is, according to the present invention, there is provided a plating cleaning water reusing system that uses the purifying device using the photocatalyst disclosed in Japanese Patent No. 3436267 to circulate and use the purified plating cleaning water again in the plating process.

  In the silica-based composite oxide fiber of the present invention, the oxide phase (first phase) mainly composed of the silica component may be amorphous or crystalline, and may be a solid solution or eutectic point with silica. You may contain the metal element or metal oxide which can form a compound. The metal element (A) capable of forming a solid solution with silica or its oxide is not particularly limited as the metal element (B) capable of forming a compound having a specific composition with silica. Examples of (B) include aluminum, zirconium, yttrium, lithium, sodium, barium, calcium, boron, zinc, nickel, manganese, magnesium, iron and the like.

  This first phase forms the internal phase of the fiber obtained in the present invention and plays an important role in bearing the mechanical properties. The ratio of the first phase to the entire fiber is preferably 98 to 40% by weight, and in order to sufficiently develop the target second phase function and also to exhibit high mechanical properties, It is preferable to control the existence ratio of one phase within the range of 50 to 95% by weight.

  On the other hand, the metal oxide constituting the second phase plays an important role in developing the photocatalytic function. Ti is mentioned as a metal which comprises a metal oxide phase. 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 abundance ratio of the second phase constituting the surface layer portion of the fiber is preferably 2 to 60% by weight, although it varies depending on the type of the oxide, in order to fully exhibit its function and simultaneously exhibit high strength. It is preferable to control within the range of 5 to 50% by weight. The crystal grain size of the metal oxide containing the second phase Ti is preferably 15 nm or less, particularly preferably 10 nm or less.

  The proportion of Ti present in the metal oxide constituting the second phase increases in a gradient toward the fiber surface, and the thickness of the region where the composition gradient is clearly recognized is in the range of 5 to 500 nm. However, it may be about 1/3 of the fiber diameter. In the present invention, the “existence ratio” of the first phase and the second phase means the metal oxide constituting the first phase and the whole metal oxide constituting the second phase, that is, the first phase relative to the whole fiber. By weight of metal oxide and second phase metal oxide is meant.

  The silica-based composite oxide fiber has a photocatalytic function and at the same time excellent heat resistance. For example, the temperature at which 90% or more of the original fiber strength remains in heated air for 1 hour is 1000 ° C.

  Next, the manufacturing method of the silica group composite oxide fiber of this invention is demonstrated. In the present invention, the general formula

（但し、式中のＲは水素原子、炭素原子数１〜４の低級アルキル基又はフェニル基を示す。）で表される主鎖骨格を有する数平均分子量が２００〜１０，０００のポリカルボシランを、Ｔｉを含む有機金属化合物で修飾した構造を有する変性ポリカルボシラン、或いは変性ポリカルボシランとＴｉを含む有機金属化合物との混合物を溶融紡糸し、不融化処理後、空気中又は酸素中で焼成することにより、シリカ基複合酸化物繊維を製造することができる。

(However, R in the formula represents a hydrogen atom, a lower alkyl group having 1 to 4 carbon atoms, or a phenyl group.) A polycarbosilane having a main chain skeleton represented by 200 to 10,000. A modified polycarbosilane having a structure modified with an organometallic compound containing Ti, or a mixture of a modified polycarbosilane and an organometallic compound containing Ti is melt-spun, and after infusibilizing treatment, in air or oxygen By firing, a silica-based composite oxide fiber can be produced.

  The first step 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 fiber. The basic production method of the modified polycarbosilane is very similar to that disclosed in JP-A-56-74126, but in the present invention, it is necessary to carefully control the bonding state of the functional group described therein. is there. This is outlined below.

  The modified polycarbosilane as a starting material is mainly represented by the general formula

(Wherein R represents a hydrogen atom, a lower alkyl group having 1 to 4 carbon atoms or a phenyl group) and a polycarbosilane having a main skeleton represented by 200 to 10,000 , M (OR ′) n or MR ″ m (M is at least Ti, R ′ is an alkyl or phenyl group having 1 to 20 carbon atoms, R ″ is acetylacetonate, m and n are It is derived from an organometallic compound containing Ti (an integer greater than 1) having a basic structure (hereinafter simply referred to as an organometallic compound).

  Here, in order to produce the fiber having the gradient composition of the present invention, 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 the above-mentioned monofunctional is reacted and an unreacted organometallic compound remains, conversely, a decrease in melt viscosity is observed.

  In the present invention, it is desirable to select conditions for intentionally leaving an unreacted organometallic compound. In the present invention, a material in which the modified polycarbosilane and the unreacted organometallic compound or an organometallic compound of about 2 to 3 trimmers coexist is used as a starting material. However, even with the modified polycarbosilane alone, the molecular weight is extremely low. When the modified polycarbosilane component is included, it can be used as a starting material of the present invention.

  In the 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 referred to as precursor polymer). 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 the high-speed winding device installed at the lower part of the spinning machine.

  In the second step, in addition to the melt spinning, the precursor polymer obtained in the first step is dissolved in, for example, benzene, toluene, xylene or other solvent capable of melting the precursor polymer, In some cases, this is filtered to remove harmful substances during spinning, such as macrogel and impurities, and then the spinning solution is spun by a dry spinning method with a synthetic fiber spinning device usually used, and the winding speed is controlled. The target fiber can be obtained.

  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.

  In the third step, the spinning fiber is preheated in an oxidizing atmosphere under the action of tension or no tension to infusibilize the spinning 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 the treatment time vary depending on the composition and are not particularly defined, 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 oxide, 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 third step and the second step, the low molecular weight compound contained in the raw material is bleed out to the fiber surface, and the base of the target gradient composition is formed. Yes.

  In the fourth step, the infusible fiber is baked in an oxidizing atmosphere in a temperature range of 500 to 1800 ° C. under tension or no tension, and a target oxide phase mainly composed of a silica component (first step). 1 phase) and a metal oxide phase (second phase) containing Ti, a silica in which the Ti content of the metal oxide constituting the second phase increases in a gradient toward the surface layer. A base composite 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.

In this invention, after making the silica group composite oxide fiber which has a photocatalytic function obtained by the said manufacturing method into a short fiber, it is set as a nonwoven fabric by performing a needle punch. Although there are no particular limitations on the basis weight and thickness of the nonwoven fabric, those with a basis weight of 50 to 500 g / m ² and a thickness of 0.5 to ²⁰ mm are usually used. May be laminated.

  Further, the nonwoven fabric of silica-based composite oxide fiber of the present invention melts the precursor polymer using a melt blow method, discharges the melt from a spinning nozzle, and ejects heated nitrogen gas from the periphery of the spinning nozzle. The nonwoven fabric is formed by collecting the spun fibers in a receiver disposed at the bottom of the spinning nozzle, and then firing the nonwoven fabric in an oxidizing atmosphere after infusibility treatment. it can.

  The diameter of the spinning nozzle is usually about 100 to 500 μm. The 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 blow method, air is used as an ejection gas, but nitrogen needs to be used to spin the precursor polymer. By using nitrogen as the ejection gas, spinning can be performed stably.

  Further, when spinning the precursor polymer and collecting the spun fiber in a receiver disposed at the lower part of the spinning nozzle, it is preferable to use a suckable receiver while sucking from the lower side of the 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.

  Next, the nonwoven fabric of the silica-based composite oxide fiber of the present invention is obtained by subjecting the obtained nonwoven fabric to infusibilization treatment and baking similar to those in the case of melt spinning. 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, and more preferably 2 to 6 μm, compared to fibers produced by the melt spinning method. It can be made thinner. Thereby, the surface area of a fiber can also be enlarged and catalyst activity increases. Moreover, the nonwoven fabric manufactured by the melt blow method has a long fiber compared to the short fiber manufactured by the melt spinning method and having a length of about 40 to 50 μm formed 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.

  Next, the nonwoven fabric obtained as described above is formed into a desired shape, and the obtained molded product is detachably attached to the reaction vessel by connecting in series with a space such as a connecting rod. A photocatalyst cartridge is obtained. Although there is no restriction | limiting in particular about a shaping | molding method, For example, it can shape | mold into a specific-shaped thing by using a stainless steel metal mesh etc. as a supporting member.

  FIG. 1 shows a plating cleaning water treatment apparatus used in a plating cleaning water reuse system of the present invention in which a non-woven fabric molded product 5 has a hollow frustum shape. This plating washing water treatment apparatus is provided with a plating washing water inlet 7 at the bottom of the reaction vessel 2 and a plating washing water outlet 8 at the ceiling of the reaction vessel 2, and is arranged in a protective tube 4 at the center of the reaction vessel 1. An ultraviolet lamp 3 is installed. The washing water used in the plating process supplied from the inlet 7 passes through the gap between the fibers forming the molded product 5 and is discharged from the outlet 8. The discharged washing water is supplied again from the inlet 7 to the reaction vessel 1 and is circulated as many times as necessary. As the circulation time, an appropriate time is selected as necessary.

  FIG. 2 shows a plating cleaning water treatment apparatus used in the plating cleaning water reuse system of the present invention in which the non-woven fabric molded product 5 has a disk shape. The plating cleaning water treatment apparatus includes a plating cleaning water inlet 7 at the bottom of the reaction vessel 2, an outlet 8 at the ceiling of the reaction vessel 2, and an ultraviolet lamp 3 is installed on the outer periphery of the reaction vessel 2. In this apparatus, a photocatalyst cartridge 1 in which a molded product 5 is connected by a connecting rod 6 is installed. The washing water used in the plating process supplied from the inlet 7 of the reaction vessel 2 passes through an opening provided in a part of the disk-shaped molded product, and comes into contact with the molded product from the outlet 8 of the reaction vessel 2. Discharged. The discharged washing water is supplied again from the inlet 7 to the reaction vessel 2 and is circulated as many times as necessary. In both FIG. 1 and FIG. 2, the nonwoven fabric molded product has a line connecting its periphery perpendicular to the central axis of the reaction vessel, and the ultraviolet lamp is arranged parallel to the central axis of the reaction vessel. .

  As a molded product from a nonwoven fabric, a material in which a nonwoven fabric is fixed to both surfaces of a support member such as a wire mesh is usually used. Noble metals are recovered by burning or dissolving the product excluding the support member from the molded product. In the case of the dissolution method, a solvent that dissolves the nonwoven fabric used in the present invention, such as hydrofluoric acid, is used.

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

  After adding 100 g of toluene and 64 g of tetrabutoxytitanium to 16 g of the synthesized polycarbosilane, preheating it at 100 ° C. for 1 hour, slowly raising the temperature to 150 ° C., distilling off the toluene, and reacting for 5 hours as it is, The temperature was raised 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.

  The mixture of the modified polycarbosilane and the low molecular weight organometallic compound was dissolved in toluene, and then charged into a glass spinning apparatus. After the inside was sufficiently purged with nitrogen, the temperature was raised to distill off the toluene, 180 ° C. And melt spinning. The spun fiber was heated to 150 ° C. stepwise in air and infusible, and then fired in air at 1200 ° C. for 1 hour to obtain a titania / silica fiber.

  As a result of X-ray diffraction, the obtained fiber (average diameter: 13 μm) was composed of amorphous silica and anatase titania, and the Ti / Si (molar ratio) of the entire fiber was 0.17. Further, when the distribution state of the constituent atoms by EPMA was examined, Ti / Si (molar ratio) = 0.87 in the region of 1 μm from the outermost periphery, and Ti / Si (molar ratio) in the region of 3-4 μm from the outermost periphery. = 0.15, Ti / Si (molar ratio) = 0.04 at the center, and it was confirmed that the gradient composition was such that titanium increased toward the surface. The tensile strength of the fiber was 1.5 GPa, which was extremely high compared to the anatase-type titania / silica fiber obtained by a conventionally known sol-gel method.

The obtained titania / silica fiber was made into a short fiber having a length of 50 mm, and then needle punching was performed to obtain a titania / silica fiber felt having a basis weight of 100 g / m ² and a thickness of 1 mm.

Example 1
Ten sheets of the titania / silica fiber felt obtained in Reference Example 1 were laminated to a thickness of about 10 mm, and this was made into a stainless steel wire mesh (wire diameter 1 mm, 3 mesh) as a supporting member, with a diameter of about 85 mm and a height of 41 mm. A hollow frustum-shaped molded product having a hole with a diameter of 15 mm in the center was prepared. As shown in FIG. 1, the plating washing water treatment apparatus was prepared by arranging the reaction vessel 2 in multiple stages.

The diameter of the reaction vessel was about 85 mm, and a 40 W ultraviolet lamp was used. Using this apparatus, the water in the plating washing tank (volume 3 m ³ ) was circulated and purified at a flow rate of 3000 L / h. The number of viable bacteria in the water before purification was 3600 cfu / ml, and the amount of particulate matter of 5 μm or less was 5700 / ml. When the water quality after the 3-hour circulation treatment was examined, the viable cell count was 20 cfu / ml, and the particulate matter having a size of 5 μm or less was 100 cells / ml or less. Thus, the effect of reducing particulate matter was confirmed together with the sterilization performance. Furthermore, after the irradiated water was irradiated with near-ultraviolet rays (wavelength: 360 nm, irradiation intensity 200 μW / cm ² ) for 1 hour, the number of viable bacteria was measured again, and there was no change with 20 cfu / ml. I couldn't. When the quality of the plated product manufactured in this state was inspected, the defect rate due to bacteria and particulate matter in the cleaning tank was 0%.

Comparative Example 1
In the plating washing water treatment apparatus shown in Example 1, the hollow frustoconical shaped product was removed to create an ultraviolet sterilization apparatus. Using this apparatus, the water in the plating washing tank (volume 3 m ³ ) was circulated and purified at a flow rate of 3000 L / h. The number of viable bacteria in the water before purification was 3600 cfu / ml, and the amount of particulate matter of 5 μm or less was 5700 / ml. When the water quality after the 3-hour circulation treatment was examined, the viable cell count was 50 cfu / ml and the particulate matter of 5 μm or less was 5500 cells / ml. Furthermore, after the irradiated water was irradiated with near ultraviolet rays (wavelength: 360 nm, irradiation intensity 200 μW / cm ² ) for 1 hour, and the viable cell count was measured again, it grew to 600 cfu / ml, and the photorecovery phenomenon was observed. Admitted. When the quality of the plated product manufactured in this state was inspected, the defect rate due to bacteria and particulate matter in the plating washing tank was 20%.

Example 2
Using the apparatus shown in Example 1, the water in the plating cleaning tank (volume 3 m ³ ) was circulated and purified at a flow rate of 3000 L / h. The number of viable bacteria in water before purification was 10000 cfu / ml, and the amount of particulate matter of 5 μm or less was 15000 / ml. In addition, 2 ppm of gold ions were included. When the water quality after the 3-hour circulation treatment was examined, the viable cell count was 20 cfu / ml, and the particulate matter having a size of 5 μm or less was 100 cells / ml or less. The gold ion concentration was 0.1 ppm or less. Thus, the effect of reducing particulate matter was confirmed together with the sterilization performance. Furthermore, as a result of analyzing the photocatalyst surface after the treatment by EPMA, gold deposition on the surface of the molded product was confirmed. When this molded product was purified through combustion, crushing, and extraction, 5 g of gold having a purity of 99.5% or more was recovered.

Comparative Example 2
The hollow frustum-shaped molding was removed from the apparatus shown in Example 1, and the ultraviolet sterilizer was created. Using this apparatus, the water in the plating washing tank (volume 3 m ³ ) was circulated and purified at a flow rate of 3000 L / h. The number of viable bacteria in water before purification was 10000 cfu / ml, and the amount of particulate matter of 5 μm or less was 15000 / ml. Furthermore, 200 ppm of gold ions was contained. When the water quality after the 3-hour circulation treatment was examined, the viable cell count was 50 cfu / ml and the particulate matter of 5 μm or less was 15000 cells / ml. The gold ion concentration was 2 ppm, and no change was observed except for the viable cell count.

The plating washing water processing apparatus of the present invention is shown. The other example of the plating washing water processing apparatus of this invention is shown.

Explanation of symbols

1 Photocatalyst cartridge 2 Reaction vessel 3 UV lamp 4 Protective tube 5 Molded product 6 Connecting member 7 Washing water inlet 8 Washing water outlet 9 Supporting member

Claims (11)

  A fiber made of a composite oxide of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti in an apparatus for purifying cleaning water used in a plating process. A molded product formed from a non-woven fabric of silica-based composite oxide fibers having a photocatalytic function, in which the Ti content of the metal oxide constituting the second phase increases in a gradient manner toward the surface layer of the fibers. The plating is characterized in that a plurality of stages are arranged in a reaction vessel, purified under contact with actinic rays by contacting the molded product with cleaning water, and the purified cleaning water is recycled and used in the plating process again. Wash water reuse system.   2. The plating cleaning water reuse system according to claim 1, wherein the molded product has a conical shape, a hollow frustum shape, or a disk shape.   2. The plating cleaning water reuse system according to claim 1, wherein the molded product is used as a photocatalyst cartridge which is installed in a plurality of stages in series on a frame and is detachable into a reaction vessel.   4. The plating cleaning water reuse system according to claim 2, wherein the molded product has at least one opening.   5. The plating cleaning water reuse system according to claim 1, wherein the molded product is disposed in the reaction container in a direction perpendicular to the central axis of the reaction container.   2. The plating cleaning water reuse system according to claim 1, wherein the actinic ray irradiator is provided in the reaction vessel and / or outside the reaction vessel in parallel with the central axis of the reaction vessel.   The reuse system of plating washing water according to claim 1, wherein the proportion of the first phase is 98 to 40% by weight and the proportion of the second phase is 2 to 60% by weight with respect to the whole fiber.   The plating cleaning water reuse system according to claim 1, wherein the Ti of the metal oxide constituting the second phase is inclined at a depth of 5 to 500 nm from the fiber surface.   2. The plating cleaning water reuse system according to claim 1, wherein the second phase metal oxide is titania and the crystal grain size thereof is 15 nm or less.   11. The plating cleaning water reuse system according to claim 10, wherein the precious metals deposited on the molded product used for the purification treatment are recovered by a combustion method or a dissolution method.   A fiber made of a composite oxide of an oxide phase (first phase) mainly composed of a silica component and a metal oxide phase (second phase) containing Ti in an apparatus for purifying cleaning water used in a plating process. A molded product formed from a non-woven fabric of silica-based composite oxide fibers having a photocatalytic function, in which the Ti content of the metal oxide constituting the second phase increases in a gradient manner toward the surface layer of the fibers. A plating washing water treatment apparatus, wherein a plurality of stages are arranged in a reaction vessel, and a molded product and washing water are brought into contact with each other under irradiation of actinic rays.

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