When you choose water, have you ever noticed deionized water and wondered: What is deionized water? Is it safe to drink? This article will detail the characteristics and applications of deionised water, and how you can obtain it.

What is Deionized Water?

Deionized water, also known as softened water, DI water, or DM water, refers to water that has had its ions removed, resulting in water that contains almost no ions or charges. Ions are atoms or molecules with a positive or negative charge and are typically found in water as dissolved minerals. Common dissolved salts and minerals include substances such as sodium, magnesium, calcium, iron, iodine, chlorides, sulfates, nitrates, carbonates, and silica.

The pH value of deionised water is 7, and it is highly reactive, easily reacting with other substances. Its resistivity is usually 0.055 µS/cm, and its resistivity is 18.2 mΩ/cm. At 25°C, the resistivity of deionized water is 18 megaohms, which means it is free of impurities and highly insulative. Additionally, since all ions are removed, deionized water is typically colorless and tasteless. Because of these properties, DI water plays a crucial role in many industries that require highly pure water.

Why Is It Important?

Due to its high purity and low conductivity, deionized water holds significant importance in many applications. It can minimize the interference of impurities in water on technical research and chemical experimental analysis of scientific and medical products, ensuring the purity and safety of these products. Therefore, it is an ideal choice for pharmaceuticals, medical applications, and laboratories.

DI water, almost free of minerals and impurities, can prevent scale formation, avoiding accumulation in industrial equipment, household appliances, and pipelines. Some industrial projects use deionised water to prevent scaling and corrosion of equipment, extending their lifespan and reducing maintenance costs, such as in boilers, cooling towers, and other heat exchange systems.

Moreover, in the cleaning industry and the manufacturing of high-quality electronic components and semiconductor products, using deionized water can ensure the cleaning effectiveness of precision equipment and the quality of products. This is because deionized water does not contain impurity ions that affect product quality or minerals that can cause water spots.

Can You Drink Deionized Water?

Yes, after processing, deionized water removes most dissolved salts, minerals, and other impurities, making it very pure and suitable for limited consumption. Soft water, with fewer minerals, can make hair and skin smoother and more lustrous.

However, deionized water lacks essential minerals like calcium and magnesium needed by humans and plants, and it has a bland taste. While food remains the primary source of minerals and trace elements for the body, deionized water may still contain organic pollutants, bacteria, and viruses.

Regular tap water treated by water treatment plants typically removes most ions and harmful impurities, making it safe to drink directly. If you’re concerned about chlorine contamination or the presence of lead, copper, or iron in your pipes, consider installing a home water filter.

How to Make Deionized Water?

Ion Exchange 

Ion Exchange IX, it is a water treatment process that achieves ion exchange reactions through cation exchange resins and anion exchange resins. Cation exchange resins have negatively charged functional groups that attract cations in the water (such as calcium, magnesium, and sodium), releasing hydrogen ions in the process.

Similarly, anion exchange resins adsorb anions in the water (such as chlorides and sulfates), and release hydroxide ions. Subsequently, hydrogen ions and hydroxide ions combine to form water molecules, significantly reducing the concentration of other ions, thereby obtaining pure deionized water.

Electrodeionization

Electrodeionization (EDI), also known as electro-deionization, this method combines electrodialysis and ion exchange technology, using electricity, ion exchange, and resins to remove ions from water. When water enters the EDI module, ions are adsorbed by cation exchange resins and anion exchange resins, and replaced with hydrogen ions and hydroxide ions. Under the influence of an external electric field, cations on the cation exchange resin and anions on the anion exchange resin migrate through a semi-permeable membrane to separate compartments.

This process also generates hydrogen ions and hydroxide ions, which maintain the regeneration capability of the cation and anion resins. The ions in the compartments form concentrated wastewater that is discharged, leaving highly purified water behind. This continuous ion exchange and electric field-driven deionization process makes EDI technology cost-effective and efficient.

Reverse osmosis

Reverse osmosis (RO), it is a membrane separation process that separates the solvent from the solution through a pressure difference. The working principle involves applying pressure to one side of the RO membrane. When the pressure exceeds the osmotic pressure of the solution, only water molecules can pass through the selective semi-permeable membrane against the natural direction of osmosis.

The ions, organic compounds, and dissolved salt particles in the feed water become highly concentrated into a concentrate, while pure deionized water is obtained on the other side.

Distillation

The working principle of distillation takes advantage of the differences in boiling points of substances. By heating the water, it boils and turns into steam. The steam is then cooled via a condenser and condenses into liquid water in a clean collection container. Most dissolved substances and ions are left behind in the evaporator, resulting in highly purified water.

Is DI Water Same As Distilled Water?

DI water and distilled water are both high-purity waters, but they are not the same. The main differences between them lie in their preparation methods and purity levels.

Deionized water is usually produced by chemical treatment methods. The common production methods and their working principles have been mentioned above. The deionization process removes almost all ions and soluble salts in water, and the purity is very high. It is suitable for the pharmaceutical industry, aviation industry and semiconductor industry, which have strict requirements on the ion content in water.

Distillation is a physical treatment method that heats water to boiling, condenses the generated water vapor back into liquid, and most of the soluble substances and impurities are left in the distillation device. It is worth noting that the purity of distilled water obtained after only one distillation is not high. Only after multiple stages of distillation can extremely pure distilled water be obtained. Compared with the production of deionized water, the distillation process requires higher energy consumption and complex equipment, and the cost is higher. Distilled water is widely used in medical, laboratory, cosmetics, automobile maintenance, household appliances and food and beverage processing due to its extremely high purity.

Reading this article，you will learn more about the difference and connection between deionized water and distilled water.

What Is Deionized Water Used for?

• Electronics Manufacturing: Production and cleaning of electronic components
• Pharmaceutical Production: Drug preparation and solvent formulation
• Laboratory: Cleaning of experiments and laboratory equipment. For example: Type 1 and Type 2 deionized water.
• Automotive: Cooling systems and battery maintenance, car cleaning
• Sterilization: High-pressure sterilizers and cleaning of surgical instruments
• Dialysis: Purification process in dialysis machines
• Ingredient Preparation: Production of food and beverages
• Cleaning: Equipment cleaning
• Cosmetic Product Formulation: Basic ingredients for cosmetics, shampoos, and skincare products
• Cooling Systems: Boiler cooling water, cooling towers, and heat exchangers
• Chemical Analysis: Analytical techniques
• Biotechnology: Preparation of culture media and reagents
• Water Quality Management: Maintaining optimal water conditions for aquatic organisms

How Do I Get Deionized Water?

If your demand for deionized water is small, you can purchase it directly from supermarkets, online stores, or from pharmaceutical and laboratory suppliers.

However, if you require larger volumes of water, it is advisable to choose appropriate deionized water system and consider the following factors:

• Water quality standards/requirements for your specific use
• Quality of the water source
• Daily water production capacity/flow rate
• Type of equipment (e.g., RO, DI, EDI)
• Maintenance and operating cost budget
• Brand and model of the equipment
• System certifications and standards

Additionally, high purity requirements may necessitate the use of multiple technologies combined. For industrial ultra pure water applications, this could involve high-performance dual-pass RO systems combined with EDI, or RO+DI technologies.

Choosing well-known brands and equipment that meet industry standards is crucial. You can find our deionized water filtration products on our website.

If you have difficulty selecting a model, we recommend consulting the supplier directly or contacting our professional water treatment engineers to ensure you choose the deionized water system that best meets your needs.

Faqs:

What Is DI Water vs RO Water?

Deionised water (DI water) and reverse osmosis water (RO water) are two different types of purified water.

DI water is typically produced using ion exchange resins or electrodeionization (EDI) technology, which removes nearly all cations and anions from water, resulting in extremely low conductivity, approaching zero. It is suitable for applications that require high-quality pure water.

RO water is filtered through a reverse osmosis membrane, which removes most dissolved substances, including ions, organic materials, and microorganisms. However, RO cannot remove all ions, and its conductivity is slightly higher than DI water, resulting in lower purity. RO water is more suitable for household drinking water purification, food processing, commercial water purification, and general laboratory use. When choosing between them, specific water quality requirements and industry standards should be considered. You can learn more about this topic through this article：DI Water vs RO Water.

Does Deionized Water Go Bad?

Deionized water (DI water) itself does not spoil because it contains almost no dissolved ions or microorganisms. However, it is important to note that DI water is susceptible to contamination during storage and use. For example, it can be contaminated by bacteria from the surfaces of storage containers, and it can absorb carbon dioxide and organic substances when exposed to air. These factors can lead to a decrease in purity, affecting the stability and effectiveness of the water.

Therefore, when using and storing deionized water, it is important to maintain the cleanliness of the storage vessel and minimize prolonged exposure to air to extend the shelf life of DI water.

Can Bacteria Grow in Deionized Water?

Bacteria generally do not grow or reproduce in deionised water. This is because deionized water contains almost no dissolved ions and nutrients, which are essential elements for bacterial growth and reproduction. The extremely low conductivity and high purity of deionized water typically do not support bacterial survival. Therefore, it is widely used in industries and laboratory applications that require highly clean and sterile environments.

Is Deionized Water Recommended for Home Use?

For certain non-drinking water purposes at home, such as cleaning car windows and some electronic devices and circuit boards, deionized water is a good choice. However, it’s important to note that deionised water removes essential minerals for the human body, such as calcium and magnesium ions. Therefore, drinking deionized water is not recommended.

In addition, deionized water equipment is expensive and complicated to operate and maintain. Generally speaking, tap water treated by a water plant meets drinking water standards and is safe to drink. If you have higher standards for domestic water, you can install a whole-house filter or purchase a small household reverse osmosis filter.