Difference Between Distilled and Deionized Water

Main Difference – Distilled vs Deionized Water

Distilled water and deionized water are two forms of water that vary depending on the method of purification. Distilled water is produced by distilling water, i.e., boiling followed by condensation. Deionized water is produced by deionization, which involves removing all the charged particles from water. Deionized water is as pure as distilled water, maybe even purer. Distilled water is drinkable, but has no nutritional value since all minerals are removed. Deionized water may contain uncharged particles and molecules that cannot be removed in the process of deionization. The main difference between distilled water and deionized water is that distilled water is produced by boiling followed by condensation whereas deionized water is produced using ion exchange resins.

Key Areas Covered

1. What is Distilled Water
      – Definition, Production, Components that are Removed
2. What is Deionized Water
     – Definition, Explanation
3. What is the Difference Between Distilled and Deionized Water
     – Comparison of Key Differences

Key Terms: Deionized Water (DI Water), Distilled Water, Ion Exchange Resin, Minerals

What is Distilled Water

Distilled water is water that has been distilled to remove most of its impurities. This is done through distillation, which includes boiling water to make steam and then cooling to obtain water. Therefore, distilled water is a form of water that is free from contaminants and natural minerals.

At the temperature that is equal to the boiling point of water, the water boils and forms steam or water vapor. Then, when steam is condensed, water that is free from contaminants and other mineral components is produced. Since this water is obtained from distillation, it is called distilled water. When water is boiled, the mineral components remain in the bottom of the container since they have different boiling points than water.

Figure 1: Distilled Water

Distilled water is used in laboratories as well as in different industries. But, if we use equipment with impurities, the distilled water may get contaminated again. However, it does not cause any mineral build up in machines. Distilled water is even safe to drink, but has no advantage since it does not contain minerals and nutrients that we need.

The components in water that are removed when distilled are;

1. Bacteria
2. Viruses
3. Cysts
4. Heavy metals
5. Radionuclides
6. Organic and inorganic components
7. Toxins
8. Waste, etc.

What is Deionized Water

Deionized water is also known as DI water and is a form of water that is deeply demineralized. Deionized water can be made from tap water, river water, distilled water, etc. by passing through an electrically charged resin.

In the production of deionized water, a mixed ion exchange bed is used. This ion exchange bed consists of both positive and negative charges. The ion exchange resin contains H⁺ ions and OH^– ions. These ions can be exchanged with cations and anions in the water. However, deionization cannot remove uncharged particles and molecules from water.

Figure 2: Deionized Water

Since deionized water is pure, it is very reactive and starts to undergo chemical changes as soon as it is exposed to open air. Pure deionized water has pH 7, which is the neutral pH. But when exposed to the atmosphere, the pH is reduced due to the dissolution of acidic gases such as CO₂.

Difference Between Distilled and Deionized Water

Definition

Distilled Water: Distilled water is water that has been distilled to remove most of its impurities.

Deionized Water:  Deionized water is also known as DI water and is a form of water that is deeply demineralized.

Purity

Distilled Water: Distilled water is less pure than deionized water.

Deionized Water: Deionized is highly pure.

Method

Distilled Water: Distilled water is produced by distillation: water is boiled and then is condensed.

Deionized Water: Deionized water is produced using ion exchange resins that can remove ions from water.

Drawbacks

Distilled Water:  Distilled water is drinkable, but is not advantageous because it has no nutritional value.

Deionized Water: Deionized water is highly reactive and deionization cannot remove uncharged particles, molecules from water.

Conclusion

The difference between distilled and deionized water is their method of production; distilled water is produced by a process of distillation (boiling followed by condensation) whereas deionized water is produced by deionization, which involves ion exchange resins that can remove ions from water.

Reference:

1. “How to Distill Water.” Instructables.com, Instructables, 17 Oct. 2017, Available here.
2. “Distilled water.” Wikipedia, Wikimedia Foundation, 22 Jan. 2018, Available here.
3. Helmenstine, Anne Marie, Ph.D. “The Difference Between Distilled and Deionized Water.” ThoughtCo, Jan. 12, 2018, Available here.

Image Courtesy:

1. “1989 HK Sheung Wan Bonham Strand VITA Distilled Water” By DWatdonSHAM at Chinese Wikipedia – Transferred from zh.wikipedia to Commons (Public Domain) via Commons Wikimedia
2. “Wash bottle” By Kessaya.gae – Own work (CC BY-SA 4.0) via Commons Wikimedia