JPS61254292A - Method for making pure water - Google Patents

Abstract

PURPOSE:To stably obtain high purity water while preventing the oxidative deterioration of an ion exchange resin, by adding a nitrogen compound to raw water. CONSTITUTION:In performing the ion exchange of raw water containing residual chlorine by an ion exchange resin, a nitrogen compound such as hydrazine is added to raw water as a reducing agent in an amount of 1.3-2.0 equivalent on the basis of residual chlorine in raw water. By this method, high purity water can be obtained and the stable preserving period thereof can be prolonged.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for producing pure water, and in particular, a method for preventing oxidative deterioration of an ion exchange resin when producing pure water using an ion exchange resin. , relates to a method for producing pure water that can stably produce highly purified water.

[Prior art] Alternatively, when producing ultrapure water, chlorine remains in tap water, and this residual chlorine oxidizes and degrades the ion exchange resin, causing the quality of the treated water to deteriorate over the course of an hour. There is a problem.

For this reason, in conventional systems for producing pure water or ultrapure water using ion exchange resins, residual chlorine in raw water is reduced with a reducing agent to prevent oxidative deterioration of the ion exchange resins. However, as this reducing agent, Na2SO
3. Sulfur compound-based reducing agents such as 25205 are used for NaH3O3°Na2S205.

[Problems to be Solved by the Invention] However, when the conventionally used sulfur compound-based reducing agents are added in excess of the equivalent amount of residual chlorine in the raw water, S Os, S 02 generated from the reducing agent There was a problem in that sulfur compounds such as sulfur compounds leaked into the treated water without being ion-exchanged, reducing the purity of the treated water. Moreover, these sulfur compounds concentrated in the treated water have a very small amount of adsorption on ion exchange resins, and ultrafiltration (UF
) membrane or reverse osmosis (RO) membrane, and even if the treated water was further subjected to ion exchange or membrane separation treatment, highly pure water could not be obtained.

[Means for Solving the Problems] The present invention solves the above problems and provides a method for producing pure water that can stably obtain highly purified water, which does not contain residual chlorine. In a method for obtaining pure water by passing raw water through an ion exchange resin layer, a nitrogen compound is added to the raw water.

The present invention will be explained in detail below.

In the present invention, when raw water containing residual chlorine is ion-exchanged with an ion exchange resin, a nitrogen compound is added to the raw water as a reducing agent.

In the present invention, hydrazine (H2H4) is suitable as a nitrogen compound used as a reducing agent, but other examples include NaNO2, KNO2, and the like. By using particularly purified nitrogen compounds, the purity of the obtained pure water can be made higher.

The method of the present invention is applicable to all systems that produce pure water or ultrapure water from raw water containing residual chlorine by an ion exchange method. A system that produces pure water by exchanging ions with an ion exchange device, or ■ After filtering the raw water, RO membrane separation device → mixed bed ion exchange device → ultraviolet oxidation device → cartridge deionizer (non-regenerative mixed bed type) Examples include a system that sequentially supplies ultrapure water (water purifier) to a UF membrane separation device to produce ultrapure water. In particular, when the method of the present invention is adopted in an ultrapure water production system such as (2), it produces extremely remarkable effects.

In the present invention, the nitrogen compound may be added to the raw water as long as it is before the raw water is supplied to the ion exchange resin layer, but it is particularly preferable to add the nitrogen compound immediately before the raw water is supplied to the ion exchange resin layer, since this does not affect other equipment.

It is preferable that the amount of the nitrogen compound added be slightly in excess of the equivalent of residual chlorine in the raw water, particularly preferably 1.3 to 2.0 equivalents of the residual chlorine in the raw water. In the present invention, unlike the conventional method of adding sulfur-based compounds as reducing agents, even when nitrogen compounds are added in large excess of about lθ times the equivalent of residual chlorine, the problem of deterioration of the quality of treated water is avoided. do not have.

[Action] When hydrazine (N2H4) is added as a nitrogen compound, hydrazine converts chlorine in raw water into 2CM2+N2H4
→Reduced by the reaction N2 +4HC1. Therefore, excess N2H4 and HC generated in the reduction reaction! Since L is captured by the ion exchange resin, it does not leak into the treated water, and since N2 is an inert substance, the quality of the treated water is maintained at a good level. Moreover, Na HS O3
Whereas sulfur compounds such as hydrazine have a load of cations and anions, hydrazine has only a load of cations of the ion exchange resin, so there is no fear of anion break.

Also, when the nitrogen compound is NaN02 or KNO2, HCl l! :N a N O3 or K
N O3 is produced and these are captured by the ion exchange resin.

Therefore, according to the present invention, by reducing the residual chlorine in raw water, it is possible to prevent oxidative deterioration of the ion exchange resin and to perform stable ion exchange treatment over a long period of time. There is no reduction in the quality of the exchange treated water.

[Examples] The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples unless it exceeds the gist thereof.

Comparative Example 1 Pure water was produced by sequentially passing Yokohama city tap water (chlorine concentration 0.3 ppm, conductivity 120 s/cm) through an RO membrane separation device → mixed bed ion exchange device → cartridge deionizer In this system, on the supply side to the hotbed type ion exchanger, 10ppm of Na HS O3 is added to the raw water to produce pure water.
).

The specifications of the mixed bed ion exchange device and cartridge deionizer used are as follows.

Ion Column body: 50mmφX10X100O Cation exchange resin: Diaion PK228 (Mitsubishi Chemical Co., Ltd.) 200m! ; L Anion exchange resin: Diaion PA312 (manufactured by Mitsubishi Chemical Industries, Ltd.) 400 m column body: 25 mm φ When the quality of the treated water was examined using a CIA water quality meter installed on the outlet side of the cartridge water purifier, the specific resistance was 16MΩ・Cm at the beginning, but after 1.5 hours It was found that the purity of the treated water decreased over time.

Example 1 Instead of N a HS O3 (7), N 2 H4 was added to 10
Pure water was produced in the same manner as in Comparative Example 1 except that ppm was added, and the quality of the treated water was examined on the outlet side of the cartridge water purifier.

As a result, the quality of the treated water was constant at 17 MΩ·cm, and the water quality did not deteriorate even after water flow for 24 hours.

From Example 1, it is clear that according to the method of the present invention, extremely high purity pure water can be stably produced over a long period of time.

[Effects] As detailed above, the pure water production apparatus of the present invention adds a nitrogen compound as a reducing agent for residual chlorine in raw water. ,
High purity pure water can be produced.

■ The quality of ion exchange treated water does not deteriorate due to excessive addition of reducing agent.

(2) Therefore, there is no need for complicated operations such as controlling the amount of reducing agent added.

- Compared to sulfur compounds, nitrogen compounds are more stable in the atmosphere, less susceptible to deterioration, and have a longer stable storage period, making treatment operations easier.

Effects such as this are produced.

Therefore, according to the present invention, extremely high-purity pure water or ultrapure water can be produced stably for a long period of time, and can be used industrially in various fields, such as the production of ultrapure water in the cleaning process of LSIs and ultra-LSIs. This is extremely advantageous.

Claims (2)

[Claims] (1) A method for producing pure water, characterized in that a nitrogen compound is added to the raw water in a method for obtaining pure water by passing raw water containing residual chlorine through an ion exchange resin layer. (2) The method for producing pure water according to claim 1, wherein the nitrogen compound is hydrazine.