JP5136774B2 - Chemical purification method using electrodeionization equipment for chemical purification - Google Patents

Description

  The present invention relates to an electrodeionization apparatus for purifying a chemical containing impurities and a chemical purification method using the same.

A chemical such as sodium hydroxide is used to regenerate an ion exchange resin (anion exchange resin) used for pure water production or the like. Some of such chemicals contain trace amounts of boron (borate ion; H ₂ BO ₃ ⁻ , HBO ₃ ²⁻ , BO ₃ ³⁻ , mainly H ₂ BO ₃ ⁻ ) as impurities, When the regeneration treatment of the ion exchange resin is performed using chemicals containing various impurities, the ion exchange resin is gradually contaminated, and the treated water quality may be adversely affected. Therefore, it is desired to improve the purity of such chemicals.

  In order to produce such high-purity chemicals, conventionally, contamination during chemical production has been reduced to prevent impurities from entering the chemicals, and chromatographic treatments and ion exchange resin treatments. For example, impurities are separated and removed from chemicals.

  However, the purity of the chemical can be improved to some extent by suppressing the contamination of the chemical by the treatment as described above, or by separating and removing the impurity from the chemical. It was not possible to obtain a chemical having a purity that satisfies the above requirements. In particular, since borate ions are weak ions, it has been difficult to sufficiently remove them from chemicals by treatment with an ion exchange resin or the like.

  In view of such a problem, an object of the present invention is to provide an electrodeionization apparatus for chemical purification and a chemical purification method capable of obtaining a high-purity chemical by removing the impurity from the chemical containing the impurity. .

In order to solve the above-described problems, the present invention provides a concentration chamber and a processing chamber which are partitioned by alternately arranging an anion exchange membrane or a cation exchange membrane and a bipolar membrane between a cathode and an anode. An electrodeionization apparatus for chemical purification is provided ( Invention 1), wherein a chemical containing impurities is passed through the processing chamber and only the impurities are moved to the concentration chamber.

According to the above invention ( Invention 1), since only impurities (for example, borate ions, H ₂ BO ₃ ⁻ ) contained in the chemical can be moved to the concentration chamber, high purity from which impurities are removed and separated. Can be obtained from the processing chamber.

In the said invention ( invention 1), it is preferable that the said process chamber is filled with the ion exchanger ( invention 2). According to this invention ( Invention 2), the movement of ionic impurities to the concentration chamber side (anion exchange membrane or cation exchange membrane side) can be promoted in the processing chamber, so that impurities can be more efficiently removed from the chemical. It can be removed and a higher-purity chemical can be obtained. In addition, the ion exchanger in the processing chamber can be regenerated by hydrogen ions (H ⁺ ) or hydroxide ions (OH ⁻ ) generated at the interface of the bipolar membrane during operation of the electrodeionization apparatus for chemical purification. There is no need to recycle the exchanger. Furthermore, since the process chamber is filled with the ion exchanger, even if it is an impurity that is difficult to dissociate, it is easy to be ionized, so that a high-purity chemical can be obtained more easily. In addition, the ion exchanger in this invention contains all of an anion exchanger, a cation exchanger, and an amphoteric ion exchanger.

In the above inventions ( Inventions 1 and 2), the anion exchange membrane and the bipolar membrane are alternately arranged between the cathode and the anode, and the impurity is preferably an anion component ( In invention 3), in this invention ( invention 3), it is preferable that the anion component is a borate ion and the chemical is a sodium hydroxide aqueous solution ( invention 4).

Sodium hydroxide as a chemical used in the regeneration of anion exchange resins for the production of pure water contains a trace amount of boron (borate ion) as an impurity. When an anion exchange resin is regenerated using sodium, the anion exchange resin may be contaminated with boron and the quality of the treated water may deteriorate. According to the invention ( Invention 4), it is contained in a small amount in sodium hydroxide. Since boron can be removed, the purity of sodium hydroxide can be improved. If the anion exchange resin for producing pure water is regenerated using the high-purity sodium hydroxide thus obtained, the treated water can be expected to be improved without contaminating the resin in the regeneration treatment.

In addition, the present invention provides a chemical purification method characterized by treating the chemical containing the impurities using the electrodeionization apparatus for chemical purification according to the above inventions ( Inventions 1 to 4) ( Invention 5). ).

  According to the present invention, impurities contained in a chemical can be removed to obtain a high-purity chemical, and an ion exchanger (anion exchanger or cation exchanger) filled in a processing chamber can be electrodeionized. Since it can be regenerated during the operation of the apparatus, it is not necessary to regenerate the ion exchanger, and it is possible to simply carry out a chemical purification process.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a schematic configuration diagram of a chemical purification electrodeionization apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic diagram illustrating an operation of the drug purification electrodeionization apparatus according to the embodiment. .

  As shown in FIG. 1, a chemical purification electrodeionization apparatus 1 according to the present embodiment includes a plurality of bipolar membranes 4 and anion exchange membranes 5 arranged alternately between a cathode 6 and an anode 7. A plurality of desalting chambers 2 and a concentrating chamber 3 formed by the bipolar membrane 4 and the anion exchange membrane 5.

A flow path of an aqueous solution of sodium hydroxide (NaOH) containing borate ions (H ₂ BO ₃ ⁻ ) is connected to the inlet side of the desalting chamber 2, and an aqueous NaOH solution is connected to the outlet side of the desalting chamber 2. Are connected. The inlet side of the concentration compartment 3 has a flow path of the pure water is connected to the outlet side of the concentration compartment 3 H ₂ BO ₃ ^- flow path for ion-containing water is connected.

The bipolar membrane 4 is disposed such that the anion exchange layer surface 4A is located on the cathode 7 side and the cation exchange layer surface 4B is located on the anode 6 side. The bipolar membrane 4 includes the anion exchange layer surface 4A and the anion exchange membrane 5. Concentrated chamber 3 is formed by partitioning, and processing chamber 2 is formed by partitioning by cation exchange layer surface 4B of bipolar membrane 4 and anion exchange membrane 5. As a result, H ₂ BO ₃ ⁻ contained in the NaOH aqueous solution supplied to the processing chamber 2 moves to the concentration chamber 3 through the anion exchange membrane 5, and Na ⁺ remains in the processing chamber 2, so that impurities are removed. A high-purity aqueous NaOH solution can be obtained from the processing chamber 2.

  The bipolar membrane 4 in the present embodiment is not particularly limited as long as it has a cation exchange layer surface 4a and an anion exchange layer surface 4b and has high water electrolysis efficiency. Moreover, depending on the case, you may use what overlap | superposed the cation exchange membrane and the anion exchange membrane.

The processing chamber 2 is filled with an anion exchanger 8a. Thus, _H 2 BO ₃ as an impurity in the aqueous NaOH solution ^- can be further facilitate the transfer to the anode 6 side. The concentration chamber 3 is also filled with an ion exchanger 8b, and the ion exchanger 8b may be either an anion exchanger or a cation exchanger, or a mixture thereof. Good. Further, the anode chamber 6 and the cathode chamber 7 may be filled with an ion exchanger.

  In the present embodiment, the ion exchanger (anion exchanger 8a and cation exchanger) may be, for example, an ion exchange resin (anion exchange resin and cation exchange resin) or the like, or an ion exchange fiber (anion exchange resin). Fiber and cation exchange fiber).

In such electrodeionization apparatus 1, the processing chamber 2 of the inlet side to the _H 2 BO ₃ ^- When the content aqueous NaOH is supplied, as shown in FIG. 2, _H is introduced into the processing chamber 2 2 BO ₃ ^- H ₂ BO ₃ ⁻ that is an impurity in the aqueous NaOH solution moves to the anode 7 side (anion exchange membrane 5 side) through the anion exchanger 8a, and Na ⁺ in the aqueous NaOH solution containing H ₂ BO ₃ ⁻ It moves to the cathode 6 side (bipolar film 4 side).

Then, H ₂ BO ₃ ⁻ moved to the anode 7 side passes through the anion exchange membrane 5 and moves to the concentration chamber 3 on the anode 7 side. On the other hand, Na ^{+ that} has moved to the cathode 6 side does not pass through the anion exchange layer surface 4b of the bipolar membrane 4 and remains in the processing chamber 2 to treat an aqueous NaOH solution from which H ₂ BO ₃ ⁻ has been removed as impurities. It is discharged from the chamber 2. In this way, an aqueous NaOH solution having high purity from which H ₂ BO ₃ ^— has been removed can be obtained.

As shown in FIG. 2, by energizing a direct current to the cathode 6 and the anode 7, H ₂ BO ₃ ^- Supplying containing aqueous NaOH into the processing chamber 2, the cation exchange layer surface 4a of the bipolar membrane 4 and the anion exchange layers face 4b Water dissociation occurs at the interface. Thereby, hydrogen ions (H ⁺ ) and hydroxide ions (OH ⁻ ) are generated, and the anion exchanger 8 a filled in the processing chamber 2 is regenerated by the hydroxide ions (OH ⁻ ).

Above according to the electrodeionization apparatus 1 according to the present embodiment described, H ₂ BO ₃ contained in the NaOH aqueous solution ^- boric acid ion such removal, it is possible to obtain a high-purity aqueous NaOH, bipolar Since the anion exchanger 8a filled in the processing chamber 2 can be regenerated during the operation of the electrodeionization apparatus 1 by hydroxide ions (OH ⁻ ) generated by water dissociation at the interface of the membrane 4. There is no need to regenerate the anion exchanger 8a separately, and the NaOH aqueous solution can be easily purified.

  The embodiment described above is described for facilitating understanding of the present invention, and is not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, in the above-described embodiment, the NaOH aqueous solution containing H ₂ BO ₃ ^- as an impurity is purified. However, the present invention is not limited to this, and any chemical may be used as long as the chemical contains ionic impurities. Even so, purification treatment can be performed.

  EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited to the following Example at all.

[Example 1]
The following are used as the anion exchange membrane 5, the bipolar membrane 4, the anion exchanger 8 a filling the treatment chamber 2 and the ion exchanger 8 b filling the concentration chamber 3 of the electrodeionization apparatus 1 having the configuration shown in FIG. Industrial caustic soda was supplied to the processing chamber 2.

(1) Anion exchange membrane 5: Neoceptor AMX (product name, manufactured by Astom)
(2) Bipolar membrane 4: BP-1 (product name, manufactured by Astom)
(3) Anion exchanger 8a: anion exchange resin (manufactured by Dow Chemical Company, product name: Dowex 550A)
(4) Ion exchanger 8b: Anion exchange resin (Dow Chemical Co., product name: Dowex 550A) and cation exchange resin (Dow Chemical Co., product name: Dowex 650C) in a volume mixing ratio of 6: 5. Mixed

  Using the thus purified NaOH for the regeneration treatment of pure water production anion exchange resin (manufactured by Kurita Kogyo Co., Ltd.), the production of ultra pure water using the anion exchange resin subjected to the regeneration treatment The water to be treated was treated using a polishing unit (manufactured by Kurita Kogyo Co., Ltd.).

  The obtained treated water was analyzed by ICP-MS, but almost no boron was detected (less than 1 ppt).

[Comparative Example 1]
Polishing for ultrapure water production using an anion exchange resin that has been subjected to regeneration treatment without purification of industrial caustic soda and used for regeneration treatment of anion exchange resin for pure water production (manufactured by Kurita Kogyo Co., Ltd.) The treated water was treated using a unit (product name: Kurita Kogyo Co., Ltd.).

  The obtained treated water was analyzed by ICP-MS. As a result, 3 ppt of boron was contained in the treated water.

From the above results, by purifying the chemical (NaOH aqueous solution) using the chemical purification electrodeionization apparatus according to the present invention, the ionic impurities (H ₂ BO ₃ ⁻ etc.) contained in the chemical (NaOH aqueous solution) ) Can be removed. Thus, according to the electrodeionization apparatus for chemical purification according to the present invention, the purity of the chemical (NaOH aqueous solution) can be improved.

  The electrodeionization apparatus for chemical purification of the present invention is useful for purification treatment of an aqueous sodium hydroxide solution used for regeneration of an anion exchange resin.

1 is a schematic configuration diagram showing an electrodeionization apparatus for chemical purification according to an embodiment of the present invention. It is the schematic which shows the effect | action in the electrodeionization apparatus for chemical purification which concerns on the same embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Electrodeionization apparatus 2 ... Processing chamber 3 ... Concentration chamber 4 ... Bipolar membrane 4a ... Cation exchange layer surface 4b ... Anion exchange layer surface 5 ... Anion exchange membrane 6 ... Cathode 7 ... Anode 8a ... Anion exchanger 8b ... Ion exchanger

Claims (2)

  A chemical purification method for treating chemicals containing impurities using an electrodeionization apparatus for chemical purification,
  The electrodeionization apparatus for chemical purification comprises a concentration chamber and a processing chamber that are partitioned by alternately arranging an anion exchange membrane and a bipolar membrane between a cathode and an anode, and the processing chamber includes A chemical containing impurities is passed through and only the impurities are moved to the concentration chamber.
  The impurities are borate ions;
  A chemical refining method, wherein the chemical is an aqueous sodium hydroxide solution.   The chemical purification method according to claim 1, wherein the treatment chamber is filled with an ion exchanger.

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