JPH0299146A - Method for reducing eluted substance from mixed resin bed - Google Patents

Abstract

PURPOSE:To reduce a resin eluted substance by suppressing decomposition in a mixed ion exchange resin by preserving or using the mixed ion exchange resin in an atmosphere lowered in oxygen or free from oxygen. CONSTITUTION:At the time of the preservation of a mixed resin bed consisting of a basic anion exchange resin and an acidic cation exchange resin, said resin bed is held in water lowered in the content of dissolved oxygen and/or an oxygen free atmosphere. At the time of the use of said mixed resin bed, a liquid to be treated lowered in the content of dissolved oxygen is passed through said bed in an oxygen free atmosphere to perform ion removal treatment. By this method, the bond of the carbon atom at the benzene position of the methylene chain of the crosslinked polystyrene of the skeletal of the anion exchange resin is not cut. Therefore, the decomposition of the resin itself is suppressed to reduce the amount of a resin eluted substance to treated water and clean water is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to basic anion exchange resins (hereinafter referred to as anion exchange resins) and acidic cation exchange resins (hereinafter referred to as anion exchange resins).
This invention relates to a method for suppressing the decomposition of a mixed resin bed made of a cation exchange resin (abbreviated as cation exchange resin) and reducing the amount of eluates from the bed.

[Prior Art] In recent years, ion exchange resins have been widely used for softening and purifying industrial water as the demand for water increases.

In particular, there is a demand for further purification to extremely high purity in medical water purification equipment, water purification equipment for power plants, and water purification equipment for the semiconductor industry. Along with ultrafiltration membranes, ion exchange resins have become important components of the purification process.

Ion exchange resin is mainly a copolymer of styrene and divinylbenzene (DVB) with functional groups added to it, and although it can be reused by repeated regeneration, it cannot be used for long periods of time. It is well known that its performance deteriorates, such as a decrease in exchange capacity.

Regarding this kind of natural deterioration, in the case of anion exchange resins, the only known decomposition is the Hoffman decomposition type as shown below, and the decomposition products and decomposition routes are largely unknown. Not yet.

(Hoffmann Decomposition Route) ■ In the case of cation exchange resins, the following hydrolysis type decomposition is known, but little is known about other decomposition products or decomposition routes.

(P)QSO3H+ H2O As described above, in order to meet the demand for high-purity water in a situation where sufficient knowledge about the structure and decomposition route of decomposition products has not been obtained, it is possible to The resin whose ion exchange resin part was made into a regenerated form (H form) was made into a salt form (Na form) again, which was made into a regenerated form again, and the anion exchange resin was made into a regenerated form (OH form). Each ion exchange resin can be washed using a resin washing method in which the resin is converted into a salt form (CI form) and regenerated again, a resin washing method with warm water, a resin washing method with a large amount of water, or a combination of these methods. A method has been adopted in which the resin eluate adhering inside the container is sufficiently eluted, mixed, and then used as a mixed resin bed for water sampling operation.

In fact, the ion-exchange resins used in deionized water equipment for power plants and deionized water equipment for the semiconductor industry, which require high-purity water, are not treated to reduce the amount of resin eluted as described above. However, in this case, the only method used is to clean the eluate remaining inside the resin.
It is not a completely essential method to suppress the formation of resin eluates.

[Problems to be solved by the invention] With the increasing sophistication of technology, the level of water quality requirements has become higher. There is a strong need for the development of a substantial method to reduce the amount of resin leached into water.

[Objective of the Invention] In view of the above circumstances, the object of the present invention is to precisely measure and analyze resin eluates from cation and anion exchange resins, and to perform both ion exchange using decomposition product generation routes estimated from this. A method is provided for reducing the total amount of eluate in a mixed resin bed by reducing the production of resin eluate itself.

In other words, in desalination equipment used in various industries, mixed ion exchange resins are stored in water with reduced dissolved oxygen and/or in an oxygen-free atmosphere until they are used for water sampling operation. or/and when a mixed ion exchange resin is provided during water sampling operation, the amount of dissolved oxygen in the water to be treated is reduced and/or
Alternatively, in an atmosphere without oxygen, the decomposition of both ion exchange resins is suppressed by passing the liquid through the mixed ion exchange resin bed and removing ions, resulting in the amount of decomposition eluate from the mixed ion exchange resin bed. The present invention relates to a method for obtaining high-purity treated water by reducing resin effluents and preventing leakage of resin eluates into treated water.

[Structure of the Invention] In view of the fact that the mechanism of decomposition and elution of anion exchange resins and cation exchange resins has hardly been elucidated, the inventors first developed an anion exchange resin having a trimethylammonium group. As a result of various studies and tests on resin eluates, we found that in addition to resin eluates due to the Hoffmann decomposition route such as trimethylamine and methanol, we found that resin eluates were generated by the decomposition of the following structures:
This was newly confirmed and identified.

It is presumed that these are generated as a result of cleavage of the bond of the carbon atom at the benzyl position of the methylene chain of the crosslinked polystyrene that constitutes the skeleton of the anion exchange resin.

As a result of various studies on resin eluates from sulfonic acid cation exchange resins, we have recently discovered that resin eluates with the following structure, which is presumed to be produced by oxidative decomposition in addition to sulfate ions caused by hydrolysis, have been found. revealed its existence.

Hydroxybenzoic acid It is presumed that these are generated as a result of cutting of the benzylic carbon atom of the methylene chain of the crosslinked polystyrene resin that constitutes the skeleton of the ion exchange resin.

The inventors obtained the knowledge that resin elution contains decomposition products as described above, and when a mixed ion exchange resin is stored and/or subjected to liquid passage treatment in an oxygen-free atmosphere, the resin elution is reduced. When investigating whether the amount of substances was reduced using the total organic carbon content (TOC) as an index, we found that it was significantly reduced compared to the amount of resin eluted from a control resin exposed to the atmosphere. This invention was completed.

The method of the present invention includes storing the mixed ion exchange resin in water with reduced dissolved oxygen and/or in an oxygen-free atmosphere when storing the mixed ion exchange resin prior to use; is a mixed ion exchange resin in which ions are removed by passing the liquid through the mixed ion exchange resin in a state in which the amount of dissolved oxygen in the water to be treated is reduced and/or in an oxygen-free atmosphere. This is a method of reducing the amount of resin eluate by suppressing the decomposition of.

As a method for reducing dissolved oxygen contained in water used for resin storage or water to be treated, it is effective in reducing dissolved oxygen, and suppresses the reaction that disrupts the crosslinked polystyrene resin backbone chain. Any method may be used as long as it does so.

For example, a method in which dissolved oxygen is replaced with an inert gas by passing an inert gas such as nitrogen gas through the water; Dissolved oxygen can be removed using chemical reducing agents such as hydrazine, sodium sulfite, etc., or organic reducing materials such as redox resins, within limits that do not adversely affect the quality of the water being treated. Methods include reducing dissolved oxygen, using ultrasound, and heating water to remove dissolved oxygen.

A few examples of these will be explained.

When using an insoluble reducing material that has a reducing group in the insoluble resin matrix, the solution to be treated is passed through this as a fixed bed to reduce dissolved oxygen. The liquid to be treated can be passed through the mixed ion exchange resin layer, or the mixed ion exchange resin can be stored in the liquid to be treated, and these are mentioned as means in the embodiments of the present invention.

In addition, when removing oxygen using a soluble reducing agent, for example, when using hydrazine, hydrazine is added to the liquid to be treated, and the treated liquid is stored in an inert gas atmosphere or in a closed system. Ions dissolved in the water to be treated are removed by contacting with a cation exchange resin, and then mixed ion exchange is performed in an inert gas atmosphere or in a closed system while reducing dissolved oxygen. Suppression of eluates according to the present invention is achieved by passing the resin through the resin or storing the mixed ion exchange resin.

In order to achieve the desired effect with this invention, dissolved oxygen in water should be brought as close to zero as possible.More quantitatively speaking, the amount of dissolved oxygen in water should be equal to or less than the amount of saturated oxygen. It is desirable that it is 50% or less, especially 3
It is preferably 0% or less.

When using an anion exchange resin and a cation exchange resin in a mixed resin bed, the mixing ratio of both exchange resins is 1:9 to 9:
It is within the range of 1.

Note that storage and use in an oxygen-free atmosphere includes, for example, storage and use of the mixed ion exchange resin in a closed container filled with an inert gas such as nitrogen gas.

As the anion exchange resin used in this invention, any commercially available product can be used as long as it contains even a portion of various commercially available anion exchange resins having a quaternary ammonium group.

As the cation exchange resin, any commercially available sulfonic acid cation exchange resin can be used.

[Effects of the Invention] If the method of the present invention is applied during storage or use of a mixed ion exchange resin, decomposition in the mixed ion exchange resin is suppressed and resin eluates are reduced, resulting in improved purity of treated water. will improve.

The amount of resin eluate produced by decomposition is very small and does not pose a problem during normal water softening and purification.
For semiconductor industry, pharmaceutical industry, nuclear power generation, etc.
Highly purified water that meets applicable standards is required, and when water is used for such purposes, trace amounts of resin eluates are a problem, so there is a method to reduce resin eluates. It is absolutely necessary to provide a method.

Accordingly, the method of the present invention is particularly useful as part of a cartridge polisher of a highly purified water production system for high technology applications.

[Example] Hereinafter, it will be shown that according to the present invention, by storing a mixed ion exchange resin in an oxygen-free atmosphere, decomposition in the ion exchange resin is suppressed and resin eluate is reduced.
This will be explained in detail by showing experimental results.

The present invention will be explained in detail with reference to examples, but the present invention is not limited to these examples.

Example 1 In the example shown below, a commercially available strongly basic anion exchange resin (Amberlite IRA-900, Amberlite is a registered trademark of Rohm and Haas Company, USA) was used with 1N Na0).
1 to form the regenerated form (OH form), then reversely regenerated with 1N HCI (C1 form), and then regenerated again with 1N NaOH (C1 form).
We used a regenerated anion exchange resin that had been thoroughly washed with deionized water to sufficiently remove the resin eluates contained in the resin.On the other hand, we used a commercially available strongly acidic cation exchange The resin (Amberlite 200) was made into a regenerated form (CH type) with 1N HC1, then reversely regenerated with 1N Na0)1 (Na form), and then again made into a regenerated form (H type) with 1N HCI. Finally, an experiment was conducted using a regenerated cation exchange resin that had been sufficiently washed with deionized water to sufficiently remove the resin eluate contained in the resin.

Take 25 ml of each of these ion exchange resins and combine them with a TOC of 100 ppb or less and a dissolved oxygen amount of 6.6 ppm.
Mix thoroughly with 100 ml of deionized water, then
Dissolved gases in the deionized water were removed by applying a vacuum to 10 mm Hg in a 500 ml flask.

Nitrogen gas was introduced into this and the pressure was raised to normal pressure.

This operation was repeated twice to replace the dissolved gas in the deionized water with nitrogen gas.

The amount of dissolved oxygen was O, lppm.

At the same time, the gas phase inside the flask was also replaced with nitrogen gas and the flask was sealed tightly.

This was placed in a constant temperature bath at 50°C and stirred with shaking for 7 hours, 63 hours, and 144 hours, respectively. Thereafter, the resin and the extract containing the resin eluate were separated through a microfilter (0.2 micron).

The extract was measured using TOC Analyzer 10B manufactured by Takasugi Seisakusho.

Each TOC value is 1.0.1.7.2.2 ppm
Met.

50 without performing the above-mentioned nitrogen gas replacement operation.
A similar experiment was conducted at ℃, and extracts were collected at each time point.

The TOC values of the extracts are 1.1.8.13.1, respectively.
The TOC value was 2.9 ppm, and it is recognized that the TOC value was significantly lower than that when exposed to the atmosphere.

The amount of dissolved oxygen was measured using [1O-2A manufactured by Toa Denpa Kogyo.

Example 2 25 ml of regenerated cation exchange resin of Example 1 and 50 ml of anion exchange resin were mixed, packed into a column, and SV:
Purified deionized water with a TOC content of 100 ppb or less and a dissolved oxygen fi of 6.6 ppm was passed through the tube at a constant rate of 12 in a sealed state, and fractions were collected after 5 minutes, 12 minutes, 30 minutes, and 1 hour. The TOC value was measured. The results are 0.1.1.1.0.6 and 0.1.1.1.0.6.
It was 3 ppm.

Next, TOC 100ppb or less, dissolved oxygen amount 6.6pp
Nitrogen gas was introduced into purified deionized water according to the method of Example 1 to replace dissolved oxygen.

The amount of dissolved oxygen is 0. It became lppm.

In advance, 25 ml of regenerated cation exchange resin and 50 ml of anion exchange resin were mixed, packed into a column, and water with the above-mentioned amount of dissolved oxygen reduced was added at a constant rate of SV: 12 in a closed system. The solution was passed through the solution, and fractions were taken after 5 minutes, 12 minutes, 30 minutes, and 1 hour, and the TOC value was measured.

The result is 0.1.0.9.0.4, and 0.2p
It was pm.

Example 3 Dissolved oxygen was removed from purified deionized water with a TOC of 100 ppb or less and a dissolved oxygen amount of 6.4 ppm by heating, and the water was cooled in a sealed state.

The dissolved oxygen was 0.9 ppm.

As in Example 2, this solution was passed through a column filled with 75 ml of regenerated mixed ion exchange resin at a constant flow rate of SV, 12 in an oxygen-free atmosphere for 5 minutes after passing. Fractions were taken after 12 minutes, 30 minutes, and 1 hour, and TOC values were measured.

The results are 0.1.1.0.0.4 and 0.2ppm
Met.

Example 4 15 mg of hydrazine (
N2H4.H2O) was added to remove dissolved oxygen under nitrogen atmosphere.

The amount of dissolved oxygen was 0.6 ppm.

Therefore, if this is treated with a cation exchange resin several times in an oxygen-free atmosphere and then treated with a mixed ion exchange resin, the resin eluate can be similarly reduced.

[Brief explanation of drawings]

FIG. 1 shows the T measured under the storage conditions of Example 1.
The OC values are shown as a graph. FIG. 2 is a graph showing the TOC values measured under liquid passage in Examples 2 and 3.

Claims (1)

[Scope of Claims] 1. Storing a mixed resin bed consisting of a basic anion exchange resin and an acidic cation exchange resin in water with a reduced amount of dissolved oxygen or/and in an oxygen-free atmosphere; or/and a basic process characterized by performing ion removal treatment by passing the liquid to be treated in an oxygen-free atmosphere or/and with a reduced amount of dissolved oxygen through the mixed resin bed; A method for reducing leachables from a mixed resin bed comprising an anion exchange resin and an acidic cation exchange resin. 2. The basic anion exchange resin has the general formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ A=CH_3 (Type I) A=C_2H_4OH (Type II) (However, (P) is a crosslinked copolymer. 2. The method according to claim 1, wherein the anion exchange resin has an exchange group represented by: 3. The acidic cation exchange resin has the general formula: ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, (P) indicates a crosslinked copolymer.) A cation exchange resin having an exchange group shown in the following. The method according to claim 1.