JP2013208557A - Method for treating organic matter-containing water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating organic matter-containing water by which organic matter contained in water to be treated can be decomposed at low energy consumption.SOLUTION: A method for treating organic matter-containing water in which water to be treated containing organic matter is brought into contact with a metallic catalyst of a platinum group to decompose the organic matter, repeats the following steps of: making hydrogen water run through the catalyst; making oxygen water run through the catalyst; and then, making organic matter-containing water run through the catalyst.

Description

  The present invention relates to a method for treating organic substance-containing water, and more particularly to a method for decomposing organic substances in water to be treated with a metal catalyst.

  A high concentration chemical solution or detergent is used for cleaning or surface treatment of electronic components, and a large amount of pure water is used for rinsing them. In order to improve the quality of pure water and the reuse rate of wastewater, it is desired to develop a water treatment technique that can efficiently decompose organic matter (TOC) in water to a low concentration.

  As is well known, biological treatment or physicochemical treatment is widely performed as a method for decomposing a TOC component in water to be treated in an ultrapure water production process.

  For example, there is a method of recovering organic matter-containing wastewater, first biologically treating it to remove the TOC component, and then purifying the biologically treated water by treating it with a reverse osmosis membrane (RO membrane) (for example, Patent Document 1). . In the method of biologically treating the TOC-containing wastewater and passing it through the RO membrane separation device as in Patent Document 1, the membrane surface of the RO membrane is blocked by the biological metabolite generated by the decomposition of organic matter by microorganisms, and the flux There is a problem that decreases. Further, the power consumption of the RO pump is large.

  In addition, as physicochemical treatment, wastewater containing organic matter is directly passed through RO membrane separator; oxidant is added to wastewater containing organic matter and thermally decomposed; wastewater containing organic matter is irradiated with ultraviolet rays for decomposition (For example, Patent Document 2);

  However, these methods have a problem of high energy consumption. In addition, in RO treatment and UV treatment, when the organic matter in the organic matter-containing wastewater is a hardly decomposable organic matter represented by a nitrogen compound (such as urea) having a low molecular weight, the decomposition efficiency is extremely low.

  Patent Document 3 describes a method and apparatus for treating organic substance-containing water in which organic substance-containing water in which oxygen is dissolved is brought into contact with a platinum group metal catalyst that has adsorbed hydrogen to decompose the organic substance.

  In the method and apparatus for treating organic substance-containing water disclosed in Patent Document 3, water to be treated containing an organic substance is brought into contact with a platinum group metal catalyst, and the organic substance is decomposed by the catalytic action of the metal catalyst. Is easily decomposed at low energy. In the method and apparatus for treating organic substance-containing water, since the RO apparatus and UV irradiation treatment are not performed, the energy consumption is small.

JP 2002-336886 A JP2007-185587 WO2010 / 013677A1

  An object of this invention is to provide the processing method of the organic substance containing water which can decompose | disassemble the organic substance in to-be-processed water with low consumption energy more easily than patent document 3. FIG.

  The method for treating organic matter-containing water of the present invention is a step of bringing hydrogen water through a catalyst in a treatment method for organic matter-containing water in which water to be treated containing an organic matter is brought into contact with a platinum group metal catalyst and the organic matter is decomposed. Then, the step of passing oxygen water through the catalyst and the step of passing organic substance-containing water through the catalyst are repeated.

  In the present invention, the hydrogen water flow step, the oxygen water flow step, and the organic matter-containing raw water flow step are repeatedly performed on the platinum group metal catalyst.

  When hydrogen water is passed through the catalyst, hydrogen is adsorbed on the catalyst. By supplying oxygen water with hydrogen adsorbed on the catalyst, water molecules are generated on the catalyst, and some water molecules remain on the catalyst. Next, when the organic substance-containing water is supplied, the TOC such as urea having an unshared electron pair and the water molecule form a bond such as a coordination bond, and the organic substance is adsorbed on the catalyst. The adsorbed organic matter is partially decomposed by the action of the platinum group catalyst. And at the time of the next hydrogen water supply, hydrogen adsorb | sucks to a catalyst, and a decomposition product leaves | separates from a catalyst.

  In the present invention, the metal catalyst is accommodated in a plurality of reaction vessels, and while the hydrogen water flow step or the oxygen water flow step is performed in some of the reaction vessels, You may make it perform a water flow process. If it does in this way, the decomposition process of the organic substance in to-be-processed water can be implemented continuously.

  The metal catalyst may be made of platinum group metal fine particles. By supporting the platinum group metal fine particles on the ion exchange resin, the organic substance decomposition reaction proceeds efficiently.

  In the present invention, after water to be treated is brought into contact with the metal catalyst, this water may be brought into contact with at least one of an anion exchange resin and a cation exchange resin. If it does in this way, ionic substances, such as an organic acid generated by decomposition of TOC, will be adsorbed and removed by ion exchange resin.

  The present invention is suitable for treating raw water for producing ultrapure water (city water, well water, surface water, drainage from a drawing process of semiconductors or electronic components, etc.). The present invention is particularly suitable for application when the organic matter concentration of the raw water is about 1 to 1000 ppb, particularly about 1 to 50 ppb as TOC (total organic carbon).

It is a systematic diagram which shows embodiment of the processing method of the organic substance containing water of this invention.

  Embodiments of the method for treating organic substance-containing water of the present invention will be described in detail below with reference to the drawings.

  A raw water supply pipe 1 is connected to an inlet of a catalyst packed column (reaction vessel) 4. The outflow part of the catalyst packed column 4 is connected to the inlet of the ion exchange resin column 6 through a pipe 5. A treated water pipe 7 is connected to the outlet of the ion exchange resin column 6.

  A liquid phase chamber 2 a of a gas dissolving membrane module 2 is connected to the raw water supply pipe 1 through a pipe 3. The membrane module 2 is partitioned into a liquid phase chamber 2a and a gas phase chamber 2b by a gas permeable membrane 2c.

  The gas permeable membrane 2c is a membrane that transmits gas such as oxygen, nitrogen, carbon dioxide, and water vapor but does not transmit water. For example, a silicone film, a polytetrafluoroethylene film, a polyolefin film, and a polyurethane film. And so on.

  A hydrogen gas supply pipe 11 is connected to the gas phase chamber 2 b of the membrane module 2, and an oxygen gas supply pipe 12 and a nitrogen gas supply pipe 13 are connected to the hydrogen gas supply pipe 11. A pipe 14 branched from the nitrogen gas supply pipe 13 is connected to the exhaust pipe 15.

  The supply amount of a gas such as nitrogen to the gas phase chamber 2b is preferably 5 to 25% by volume of the water flow rate.

  As the water for gas dissolution, in order not to apply a TOC load to the catalyst 4a, it is desirable to use treated water of the catalyst packed column 4 or treated water treated with the catalyst packed column 4 and further treated with the ion exchange resin column 6. .

  Examples of the platinum group used for the metal catalyst 4a packed in the catalyst packed column 4 include ruthenium, rhodium, palladium, osmium, iridium and platinum. These platinum groups can be used alone, in combinations of two or more, can be used as alloys of two or more, or can be a naturally produced mixture of refined products. Can also be used without separating them into single bodies. Among these, platinum, palladium, a platinum / palladium alloy alone or a mixture of two or more of them is particularly suitable because of its strong catalytic activity.

  The platinum group metal catalyst 4a may be platinum group metal fine particles, or may be a metal supported catalyst in which platinum group metal nanocolloid particles are supported on the surface of a carrier.

  There is no restriction | limiting in particular in the method of manufacturing a platinum group metal nano colloid particle, For example, a metal salt reduction reaction method, a combustion method, etc. can be mentioned. Among these, the metal salt reduction reaction method can be suitably used because it is easy to produce and stable metal nanocolloid particles can be obtained. As the metal salt reduction reaction method, for example, 0.1 to 0.4 mmol / L aqueous solution of chloride such as platinum, nitrate, sulfate, metal complex, etc., alcohol, citric acid or a salt thereof, formic acid, acetone, Metal nanocolloid particles can be produced by adding 4 to 20 equivalents of a reducing agent such as acetaldehyde and boiling for 1 to 3 hours. Further, for example, by dissolving 1-2 mmol / L of hexachloroplatinic acid, potassium hexachloroplatinate, etc. in an aqueous polyvinylpyrrolidone solution, adding a reducing agent such as ethanol, and heating and refluxing in a nitrogen atmosphere for 2 to 3 hours, Nanocolloid particles can be produced.

  The average particle size of the platinum group metal nanocolloid particles is preferably 1 to 50 nm, more preferably 1.2 to 20 nm, and still more preferably 1.4 to 5 nm. If the average particle size of the metal nanocolloid particles is less than 1 nm, the catalytic activity for TOC decomposition and removal may be reduced. When the average particle diameter of the metal nanocolloid particles exceeds 50 nm, the specific surface area of the nanocolloid particles becomes small, and the catalytic activity for TOC decomposition and removal may be reduced.

  There is no restriction | limiting in particular in the support | carrier which carry | supports the platinum group metal nano colloid particle, For example, a magnesia, a titania, an alumina, a silica-alumina, a zirconia, activated carbon, a zeolite, a diatomaceous earth, an ion exchange resin etc. can be mentioned. Among these, an anion exchange resin can be particularly preferably used. Since the platinum group metal nanocolloid particles have an electric double layer and are negatively charged, they are stably supported on the anion exchange resin and hardly peeled off. The anion exchange resin is preferably a strongly basic anion exchange resin based on a styrene-divinylbenzene copolymer, and more preferably a gel resin. The exchange group of the anion exchange resin is preferably in the OH form.

  The amount of platinum group metal nanocolloid particles supported on the anion exchange resin is preferably 0.01 to 0.2% by weight, and more preferably 0.04 to 0.1% by weight. If the supported amount of metal nanocolloid particles is less than 0.01% by weight, the catalytic activity for the decomposition and removal of organic substances may be insufficient. The supported amount of the metal nanocolloid particles is 0.2% by weight or less, and sufficient catalytic activity is exhibited for the decomposition and removal of the organic matter. Usually, it is not necessary to support the metal nanocolloid particles exceeding 0.2% by weight. In addition, when the amount of metal nanocolloid particles supported increases, the risk of metal elution into water also increases.

  The ion exchange resin column 6 is filled with an ion exchange resin 6a. This ion exchange resin column is preferably a non-regenerative mixed bed ion exchange apparatus in which a strongly acidic cation exchange resin and a strongly basic anion exchange resin are mixed and packed in accordance with the ion load as the ion exchange resin 6a. By using a mixed bed type ion exchange apparatus, cations and anions in water are completely removed, and ultrapure water having extremely low electrical conductivity can be obtained. Further, undecomposed organic substances and organic acids generated during the decomposition process of organic substances are also removed.

  Next, an organic matter decomposition method for decomposing organic matter (TOC component) in the water to be treated using the apparatus of FIG. 1 will be described.

  First, hydrogen gas is supplied from the pipe 11 to the gas phase chamber 2b of the membrane module 2 and dissolved in the liquid phase. Undissolved surplus hydrogen is discharged from the exhaust pipe 15. At this time, nitrogen gas is supplied to the exhaust pipe 15 via the pipes 13 and 14 and merged with the hydrogen gas in the exhaust pipe 15 so that the hydrogen gas concentration after the merge is 4% (v / v) or less. It is desirable to discharge safely below the explosion limit of hydrogen.

  The concentration of hydrogen water is preferably about 0.1 to 1.6 mg / L (25 ° C.), particularly about 0.2 to 1.0 mg / L (25 ° C.).

  Although the amount of dissolved hydrogen supplied to the catalyst packed column 4 should just be 1 time or more of the hydrogen adsorption amount of the catalyst 4a, about 1 to 5 times is desirable. By supplying hydrogen water to the catalyst packed column 4, hydrogen is adsorbed on the catalyst 5a, and at the same time, the TOC component adsorbed so far is desorbed from the catalyst 4a. At least a part of the TOC component is decomposed and ionized.

  Next, in order to sufficiently discharge the TOC component and decomposition products from the catalyst packed column 4, nitrogen gas is supplied from the pipe 13 to the gas phase chamber 2 b and nitrogen water is supplied to the catalyst packed column 4. Undissolved nitrogen gas is discharged from the gas phase chamber 2b to the exhaust pipe 15. At this time, nitrogen gas is not supplied to the nitrogen gas branch pipe 14. Nitrogen gas is supplied to the nitrogen gas branch pipe 14 for dilution of exhaust gas only when hydrogen gas or oxygen gas is exhausted from the gas phase chamber 2b.

  The concentration of nitrogen water is preferably about 2 to 18 mg / L (25 ° C.), particularly about 2 to 12 mg / L (25 ° C.). The flow rate of nitrogen water is desirably 1 to 10 times the catalyst amount of the catalyst packed column 4 and is preferably about 2 to 5 times from the viewpoint of achieving both discharge properties and treatment time.

  Thereafter, oxygen gas is supplied from the pipe 12 to the gas phase chamber 2 b, and oxygen water is supplied to the catalyst packed column 4. At this time, since the oxygen gas discharged from the exhaust pipe 15 as undissolved oxygen gas has a flame-supporting property, the nitrogen from the nitrogen gas branch pipe 14 is merged so that the oxygen concentration is 20% (v / v) or less. It is desirable to discharge later. The concentration of oxygen water is preferably about 1 to 1000 μg / L, particularly about 1 to 100 μg / L.

  The amount of oxygen water supplied to the catalyst packed column 4 may be not less than ½ of the mass of the amount of hydrogen that can be adsorbed to the catalyst 4a (hydrogen adsorption capacity), but about 1/2 to 10 times the mass of the hydrogen adsorption capacity Is preferable, and about 1 to 5 times is particularly preferable.

  Next, water to be treated is supplied from the raw water supply pipe 1 to the catalyst packed column 4, and treated water from the catalyst 4 a is supplied from the pipe 5 to the ion exchange resin column 6. The ionic substances contained in the effluent of the catalyst packed column 4 are removed by ion exchange, and the treated water flows out from the pipe 7.

Thus, SV at the time of passing raw water through the catalyst packed column 4 is preferably about 30 to 200 h ^−1, particularly about 60 to 180 h ⁻¹ .

  Thereafter, the organic material-containing raw water is treated by sequentially repeating the hydrogen water flow step, the oxygen water flow step, and the raw water flow step. In this treatment method, when oxygen water is supplied in a state where hydrogen is adsorbed on the catalyst 4a, water molecules are generated and some water molecules remain on the catalyst 4a. Next, when raw water is supplied, the organic substance is adsorbed on the catalyst 4a by a bond such as a coordinate bond between an organic substance such as urea having an unshared electron pair and the water molecule, and the organic substance is reduced by the catalytic action. Decomposed into molecular objects. Then, at the next hydrogen water supply, hydrogen is adsorbed on the catalyst, and at the same time, the decomposition product leaves the catalyst 4 a and is discharged from the catalyst packed column 4.

  In the present invention, a plurality of catalyst-packed columns are installed in parallel, and when a hydrogen water flow step or an oxygen water flow step is performed in some reaction vessels, an organic substance-containing water flow step is performed in another reaction vessel. By performing, you may make it implement the process of to-be-processed water continuously.

  Hereinafter, the present invention will be described in detail using examples and comparative examples.

[Example 1]
Using the apparatus of FIG. 1, the raw water was treated under the following conditions.
Metal catalyst (catalyst resin): “Nano Saver” manufactured by Kurita Kogyo Co., Ltd.
Ion exchange resin), 2L
Degassing membrane module: “Lixel G420” manufactured by Celgard
Ion exchange resin: Kurata Kogyo "KR-UA1" 1L and "KR-UC1" 1L
Mixed resin water amount: 2L / min
As raw water, synthetic waste water in which urea was dissolved in 3 ppb (asC) in ultrapure water was used.

After the hydrogen water hydrogen to the raw water was dissolved 1.0 mg / L was 10min Rohm catalyst 4a at SV = ^{12h -1,} the catalytic nitrogen water nitrogen dissolved 16 mg / L to the raw water at SV = ^{60h -1} Water was passed through 4a for 20 min. Subsequently, oxygen water in which 100 μg / L of oxygen was dissolved in the raw water was passed through the catalyst 4 a for 30 min at SV = 60 h ⁻¹ . Thereafter, the raw water was passed through the catalyst 4a for 60 min at SV = 60h- ¹ .

  As a result of measuring the TOC concentration of the treated water in the outlet pipe 9 of the ion exchange resin column 6, it was 1 ppb or less.

[Comparative Example 1]
1 was used in place of the catalyst packed column 4 except that a low-pressure UV lamp device (“AZ-26” manufactured by Nippon Photo Science Co., Ltd.) was installed, and raw water was passed at a water volume of 2 L / min. In addition, water flow of hydrogen water, nitrogen water, and oxygen water was omitted.

  As a result of measuring the TOC concentration of the treated water in the outlet pipe 9 of the ion exchange resin column 6, it was 3 ppb, and urea was not decomposed at all.

2 Gas dissolution membrane module 4 Catalyst packed column 4a Metal catalyst 6 Ion exchange resin column

Claims (4)

In the method for treating organic matter-containing water, the water to be treated containing organic matter is brought into contact with a platinum group metal catalyst, and the organic matter is decomposed.
Passing hydrogen water through the catalyst;
Next, passing oxygen water through the catalyst;
Then, the process of passing organic substance containing water through a catalyst is performed repeatedly, The processing method of organic substance containing water characterized by the above-mentioned.   In claim 1, when a plurality of reaction containers containing the metal catalyst are used and a hydrogen water flow process or an oxygen water flow process is performed in some of the reaction containers, the organic substance-containing water flow is performed in another reaction container. A method for treating water containing organic matter, comprising performing a water step.   3. The method for treating organic substance-containing water according to claim 1, wherein the metal catalyst comprises platinum group metal fine particles and is supported on an ion exchange resin.   The water containing organic matter according to any one of claims 1 to 3, wherein the water to be treated is brought into contact with the metal catalyst, and then the water is brought into contact with at least one of an anion exchange resin and a cation exchange resin. Processing method.

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