What is deionized water

Speaking of deionized water, I believe many people have heard of it. It is often used in laboratory research and chemical raw materials. Due to its wide range of uses, we can hear the name of deionized water all the time. Although its name is well known to us, people still don’t have a thorough understanding of what deionized water is. Let’s take a brief look at this issue below.

Deionized water is pure water from which impurities in the form of ions have been removed. International Organization for Standardization ISO/TC

The definition of "deionization" stipulated in 147 is: "Deionized water is completely or incompletely free of ionic substances." Today's process mainly uses RO reverse osmosis to produce it. Ion exchange resins are used to remove anions and cations from water, but soluble organic matter is still present in the water, which can contaminate the ion exchange column and reduce its effectiveness. Deionized water is also prone to bacterial growth after storage.

Process Equipment

Deionized water is nearly pure water obtained by removing ionic impurities in water through ion exchange resin. The rationality of the design of its production equipment is directly related to the quality of deionized water and the economic efficiency of operation. [1]

Deionized water preparation process and its characteristics

1. The traditional water treatment method of producing deionized water with ion exchange resin has the following basic process flow:

Raw water → multi-media filter → activated carbon filter → precision filter → cation bed → anion bed → mixed bed → post-safety filter → water use point.

(Features: relatively high pollution, low degree of automation, low initial investment)

2. Reverse osmosis-ion exchange equipment produces deionized water with stable water quality and high purity. Its basic process flow is:

Raw water → multi-media filter → activated carbon filter → precision filter → reverse osmosis equipment → mixed bed → ultrapure water tank → ultrapure water pump → post-safety filter → water use point.

(Features: low pollution, high degree of automation, medium initial investment, moderate price)

3. The method of producing deionized water by combining reverse osmosis equipment with electrodeionization (EDI) equipment is the latest process for producing ultrapure water. It is also an environmentally friendly, economical and highly potential ultrapure water preparation process. The basic process flow is as follows:

Raw water → multi-media filter → activated carbon filter → precision filter → reverse osmosis equipment → electrodeionization (EDI) → ultrapure water tank → ultrapure water pump → post-safety filter → water use point.

(Features: environmentally friendly, high degree of automation, large initial investment, relatively expensive.)

From tap water to deionized water, it generally goes through several steps:

1. First filter out the coarser impurities through quartz sand.

2. Then high pressure passes through the reverse osmosis membrane.

3. Finally, ultraviolet sterilization is usually required to remove microorganisms in the water.

4. If the resistivity has not reached the requirement at this time, another ion exchange process can be carried out and the maximum resistivity can reach 18 megahertz.

Relatively speaking, distilled water is simply vaporized and then condensed, and its purity, such as resistivity, is generally not as good as high-purity deionized water. Most of the water used in the semiconductor industry is high-purity deionized water.

Main Application

1. Water used in laboratories and chemical laboratories, routine tests in general laboratories, preparation of standing solutions, cleaning of glassware, etc.;

2. Electronic industry production, such as cathode ray tube glass shell, cathode ray tube, liquid crystal display, circuit board, computer hard disk, integrated circuit chip, single crystal silicon semiconductor, etc.;

3. Electric power boilers, softened water and desalination required for boilers;

4. Surface coating, electroplating, coated glass cleaning of automobiles, household appliances, and building materials, etc.;

5. Petrochemical industry, chemical reaction cooling water, chemical agents, production liquid water, etc.;

6. Industrial textile printing and dyeing, steel cleaning water, etc.;

7. Water used in the production of food, beverages, alcoholic beverages and cosmetics;

8. Purification of sea water, brackish water, etc.

The widely used EDI system is the most popular new type of electrolytic desalination system [2]. It has replaced the traditional ion mixed bed device and become the rising star in the pure water industry. The EDI system not only makes up for the defects of traditional processes and simplifies the process steps, but also improves production efficiency; it has more advantages than traditional deionized water equipment in terms of both the performance of the equipment itself and the economic investment.

standard:

1. Colorless, clear liquid, odorless and tasteless.

2. The resistivity is greater than 0.5 MΩ·cm (megaohm·centimeter), and the highest resistivity can reach 18 megaohms.

3. The purity of deionized water is higher than that of distilled water.