JPH04250882A - Production of pure water - Google Patents

Abstract

PURPOSE:To obtain pure water having high purity and stable water quality with the electric power consumption lower than in the conventional methods by housing a mixed body composed of a weakly acidic cation exchange resin of a regeneration type and an II type strongly basic anion exchange resin of a regeneration type into the desalting chamber of an electrolytic dialysis device, then executing an electrolytic dialysis while passing the water to be treated in the desalting chamber. CONSTITUTION:The electrolytic dialysis device is constituted of the desalting chamber 7 formed of the alternately arranged anion exchange membranes 5 and cation exchange membranes 6 and a thickening chamber 8 between a cathode chamber 4 having a cathode 2 and an anion chamber 3 having an anode 3. The mixed body composed of the weakly acidic cation exchange resin of the regeneration type and the II type strongly basic anion exchange resin of the regeneration type is housed into the desalting chamber 7 thereof and thereafter, the electrolytic dialysis is executed while the water to be treated is circulated into the desalting chamber 7, by which the pure water is produced. Consequently, the pure water having the high purity and the stable water quality is obtd. with the electric power consumption lower than in the conventional method.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a method for producing pure water,
More specifically, the present invention relates to an improvement in an electrically regenerated pure water production method for producing pure water by combining an ion exchange resin and an ion exchange membrane.

0002

[Prior Art] As a method for producing pure water, purified water is obtained by passing water to be treated through a regenerated ion exchange resin bed. The ion exchange resin method, in which the material is regenerated using an acid or alkali regenerant and then reused, is widely used. This method uses acid or alkali as a regenerating agent to regenerate the ion exchange resin, so there is a problem in that acidic and alkaline regeneration waste liquids are discharged.

[0003] Therefore, there is a demand for a method for producing pure water that does not use a regenerating agent, and in recent years, an electric regeneration method for producing pure water that combines an ion exchange resin and an ion exchange membrane has been attracting attention. This method involves forming a mixed resin layer of an anion exchange resin and a cation exchange resin in a desalination chamber of an electrodialysis device in which anion exchange membranes and cation exchange membranes are arranged and incorporated in an alternating manner.
In this method, pure water is produced by applying a voltage to perform electrodialysis while passing the water to be treated through this desalination chamber. However, this method also has the following problems. That is, if the operation continues for a long time, the electric conductivity of the mixed ion exchange resin layer in the demineralization chamber becomes non-uniform, and the mixed ion exchange resin layer is not uniformly regenerated, resulting in a gradual decrease in the purity of the pure water.

[0004] As a method to solve such problems,
The present applicant previously proposed storing a mixture of a regenerated weakly basic ion-exchange resin and a weakly acidic ion-exchange resin as an ion-exchange resin in the demineralization chamber of an electrodialyzer. (Japanese Unexamined Patent Publication No. 2-17715), in the electric regeneration pure water production method, the ion exchange resin is regenerated using direct current, so it is important to reduce the power consumption.
Although this method can stably obtain high-purity pure water, it has disadvantages such as a relatively high voltage current, which increases power consumption, and may shorten the life of the ion exchange membrane. Ta.

[0005]

[Problems to be Solved by the Invention] Against this background, the present inventors have determined that the power consumption of the electric regeneration pure water production method is mainly expressed as the value obtained by multiplying the square of the current by the electrical conductivity of the desalination chamber. Therefore, we conducted repeated research on a method for reducing the electrical resistance of the demineralization chamber, and finally completed the present invention.

[0006]

[Means for Solving the Problems] That is, the present invention is a method for reducing the electrical resistance of a demineralization chamber in an electrically regenerated pure water production method. A regenerated weakly acidic cation exchange resin and a regenerated type II strong base are placed in the demineralization chamber of an electrodialysis machine in which cation exchange membranes and anion exchange membranes are arranged alternately between the anode chamber and the anode. The present invention provides a method for producing pure water, which comprises storing a mixture of anion exchange resins and then performing electrodialysis while passing the water to be treated through the desalination chamber to produce pure water. It is something.

To explain the present invention in more detail, in a known method for producing pure water by combining an ion exchange resin and an ion exchange membrane, a regenerated form of weakly acidic cation is used as the ion exchange resin housed in the desalting chamber. Ion exchange resin and regenerated form I
The present invention provides a method for producing pure water with low power consumption by using a mixture of Type I strongly basic anion exchange resins and increasing the electrical conductivity of a demineralization chamber. In order to consider reducing the electrical resistance of the demineralization chamber, the present inventors measured and investigated the electrical conductivity of the ion exchange resin itself due to differences in the functional groups of various ion exchange resins, and as a result, the following results were obtained. It got a good reputation.

[0008]

[Table 1]

That is, if a mixture of regenerated strong ion exchange resins is used as in the conventional electric regeneration pure water production method, although the electrical resistance of the demineralization chamber becomes small, the current mainly flows from the regenerated type. In order to flow into the ion exchange resin,
Loaded ions are difficult to remove from the loaded ion exchange resin, and sufficient regeneration is not achieved. Therefore, since the proportion of loaded resin gradually increases, the quality of the treated water decreases accordingly. On the other hand, if a mixture of regenerated weak ion exchange resins is used, pure water with stable water quality can be obtained, but because the electrical conductivity of the ion exchange resin is low, a high voltage power source is required. The disadvantage is that power consumption is large. Therefore, in the present invention, a mixture of a regenerated weak ion exchange resin as the cation exchange resin and a regenerated Type II strong ion exchange resin as the anion exchange resin is employed. This mixture is mixed uniformly and placed in the desalination chamber of the electrodialysis machine.

[0010] If electrodialysis is performed while the water to be treated is passed through the demineralization chamber, the electrical conductivity of the mixture is much higher than that of a mixture of weak ion exchange resins. The electrical resistance of the water is also reduced, so pure water of stable quality can be obtained with a small amount of electricity without the need for high-voltage current. In addition, even if the load on the mixture increases due to continuous flow of liquid for a long time, the mixture of the weakly acidic cation exchange resin of the present invention and the type II strong basic anion exchange resin will not be able to handle the load. When shaped, its electrical conductivity increases, making it easier for electric current to pass through it. Therefore, the loaded type is immediately regenerated into the regenerated type, and the ratio of the loaded type to the entire mixture does not increase.Moreover, it can be regenerated with less power consumption than conventional power consumption, and it is possible to achieve high purity. Can supply pure water.

The details of the present invention will be explained with reference to FIG. FIG. 1 is a schematic vertical cross-sectional view of an electrodialysis apparatus used in the present invention. The electrodialysis device consists of an anode chamber 3 containing an anode plate 1, a cathode chamber 4 containing a cathode plate 2, and an anion exchange membrane 5 and a cation exchange membrane 6 arranged alternately between them. It is composed of a salt chamber 7 and a concentration chamber 8.

[0012] The anode chamber 3 and the cathode chamber 4 contain an electrolytic chamber solution to provide electrical conductivity. Since the concentration of this electrolyte solution gradually decreases, it is preferable to always maintain a constant value. As a method for this, it is preferable to circulate a part of the concentrated water discharged from the concentration chamber 8. The desalting chamber 7 houses a mixed ion exchange resin consisting of a regenerated weakly acidic cation exchange resin and a regenerated Type II strongly basic anion exchange resin.

When a direct current is passed through the demineralization chamber 7 and concentration chamber 8 of the electrodialysis apparatus constructed as described above while flowing the water to be treated, impurity ions in the water to be treated are ion-exchanged in the demineralization chamber 7. At the same time, impurity ions adsorbed on the ion exchange resin are electrodialyzed by the ion exchange membrane and moved to the concentration chamber 8, where they are removed by the resin and pure water is produced.
It flows out as concentrated water.

The weakly acidic cation exchange resin employed in the present invention is an ion exchange resin in which an exchange group such as a phosphoric acid group or a carboxylic acid group is bonded to a three-dimensionally condensed polymer base. Therefore, the dissociation constant (pK) of the exchange group is 2~
Those in the range of 6 are preferred. On the other hand, strongly basic anion exchange resins have a quaternary ammonium group as an exchange group, and in particular, the structure of the exchange group is as shown below, and the dissociation constant (pK) is slightly low in basicity. 13 or higher type II types are adopted.

[0015]

embedded image The weakly acidic cation exchange resins used in the present invention include Amberlite IRC-84 (trade name, manufactured by Rohm and Haas Co.), DOWEX CCR-20 (trade name, manufactured by Dow Chemical Co.). ), Duolite CC-3 (product name, manufactured by Rohm and Haas Co.), Revachit CN
P-80 (product name, manufactured by Bayer AG), Imac Z-5
There are commercially available products such as (trade name, manufactured by Rohm and Haas Co.) and Diaion WK-20 (trade name, manufactured by Mitsubishi Kasei Corporation).

[0016] Type II strongly basic anion exchange resins include Amberlite IRA-410 and IRA-91.
0, Duolite A-102D, A-162 (all product names, manufactured by Rohm and Haas Co.), IONAC A
-550 (product name, manufactured by Cyblon Co.), Revachit M-600, MP-600 (product name: Bayer AG)
．． ), Imac S5-42 (product name, manufactured by Rohm and Haas Co.), Diaion SA-20A, PA40
There are commercially available products such as No. 0 series (all product names manufactured by Mitsubishi Kasei Corporation).

After the above-mentioned ion exchange resin is made into a regenerated form by a conventional method, the ion exchange capacity ratio of weakly acidic cation exchange resin:strongly basic anion exchange resin is uniform in the range of 1:2 to 2:1. and house them in the desalination chamber of the electrodialysis machine. The present invention is characterized by a mixture of ion exchange resins housed in a desalination chamber, and conventionally known electrodialysis equipment including ion exchange and its operating conditions can be used in combination as appropriate. . For example, the electrodialysis device used in the present invention is not particularly limited to known electrodialysis devices as long as it has a structure in which cation exchange membranes and anion exchange membranes are alternately arranged between the cathode and anode electrodes. Adopted.

A typical method is to alternately arrange cation exchange membranes and anion exchange membranes between the cathode and the anode through a chamber frame, and use these ion exchange membranes and the chamber frame to form a demineralization chamber. This is an electrodialysis device such as a filter press type or a unit cell type that has a structure in which a concentration chamber is formed. The number of membranes used in such an electrodialysis apparatus, the channel spacing between the demineralization chamber and the concentration chamber (membrane spacing), etc. are appropriately selected depending on the salt content and treatment amount of the water to be treated.

[0019]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way.

Example 1 Pure water was produced using the electrodialysis apparatus shown in FIG. There are 3 desalting chambers and 2 concentrating chambers, each desalting chamber is 390 mm long, 130 mm wide, and 8 mm wide, and each desalting chamber is filled with regenerated weakly acidic cation exchange resin Diamond W.
K20 (trade name, manufactured by Mitsubishi Kasei Corporation), 106ml and recycled type II strong basic anion exchange resin Diaion P
A418 (trade name, manufactured by Mitsubishi Kasei Corporation), 300 ml, was mixed uniformly and stored.

On the other hand, each concentration chamber has a length of 390 mm and a width of 130 mm.
mm, width 2 mm, and was not filled with anything. Next, NaCl was dissolved in pure water to adjust the electrical conductivity to 20 μs/cm, and this was used as water to be treated. This treated water is fed to the desalination chamber of the electrodialysis machine at 26 l/hr and to the concentration chamber at 20 l/hr.
Water is passed through the electrode chamber at a rate of 100 l/hr, and at the same time, a direct current of 200 mA is applied to the electrode plate of the electrode chamber at a constant rate to determine the electrical conductivity and Changes in applied voltage were measured. The results when water was passed for 200 hours were as shown in FIGS. 2 and 3.

Comparative Example 1 In the same electrodialysis apparatus as that used in Example 1, each demineralization chamber was filled with regenerated weakly acidic cation exchange resin Diaion WK20 (trade name, manufactured by Mitsubishi Kasei Corporation), 106ml
and regenerated form of weakly basic anion exchange resin Diaion WA
30 (trade name, manufactured by Mitsubishi Kasei Corporation), 300 ml was mixed and stored, and a water flow test was conducted.

The water quality, water flow conditions, and current flow conditions of the water to be treated were the same as in Example 1, and changes in the electrical conductivity and applied voltage of the treated water were measured in the same manner as in Example 1. The results were as shown in FIGS. 2 and 3.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view of an electrodialysis device.

[Explanation of symbols]

1 Anode plate 2 Cathode plate 3 Anode chamber 4 Cathode chamber 5 Anion exchange membrane 6 Cation exchange membrane 7 Demineralization room 8 Concentration chamber

FIG. 2 is a diagram showing changes over time in the quality of treated water in Example 1 and Comparative Example 1 in electrical conductivity (μs/cm). The vertical axis is treated water quality (μs/cm), and the horizontal axis is water flow time (hr).
represents.

[Explanation of symbols]

1 Results of Example 1 2 Results of Comparative Example 1

[Figure 3] Figure 3 shows the applied voltage (V) of Example 1 and Comparative Example 1.
FIG. 2 is a diagram showing changes over time. The vertical axis is the applied voltage (V),
The horizontal axis represents water flow time (hr).

[Explanation of symbols]

1 Results of Example 1 2 Results of Comparative Example 1

Claims (1)

[Claims] Claim 1: A regenerated form of weak acid After accommodating a mixture of a cation exchange resin and a regenerated type II strongly basic anion exchange resin, pure water is produced by performing electrodialysis while passing the water to be treated through the desalination chamber. A pure water production method characterized by: