Deionized Water: Benefits and Risks

Water comes in many different types – tap water, purified water, filtered water, and deionized water, to name a few. While many are safe to drink, they are generally not suitable for applications that use water as a rinse water, ingredient, or solvent (e.g., the food, cosmetics, and medical industries).

The fact is that water coming out of the tap or other sources contains ions, such as sodium, calcium, iron, copper, and others that are naturally found in soil. While these mineral ions help keep our bodies healthy, they often cause contamination, interference, and other problems in “sensitive” industrial and household processes.

For instance, ions in water can complicate lab experiments, sterilizing equipment, cleaning glassware, and other activities. In such cases, it is important to remove these ions from the water before use. Fortunately, there is a simple fix: deionized water.

But what is deionized water and how is it made? What are the benefits and risks of using it? Is it safe to drink? We explore the facts in this article.

What is deionized water?

Deionized water (also known as “DI water” or demineralized water) is water that has had all or most of its ions removed, usually by an ion exchange process.

How is DI water made?

DI water is created by running source water through one or more separate charged resins. But before the water goes through the DI system, it is usually filtered using reverse osmosis (RO) to remove organic matter and most other contaminants that may be present in the water. This pre-filtration process leaves the water relatively clean before deionization.

As water enters the DI system, it passes through two types of ion exchange resins: cation resins containing positively charged ions and anion resins containing negatively charged ions. However, some DI systems use a single mixed ion exchange resin bed with both anions and cations.

Resins are small particles consisting of organic polymer chains with functional groups built into the resin beads. Each functional group has a fixed positive or negative charge. Cationic resins contain a negatively charged functional group that attracts positively charged ions in water. Anionic resins, on the other hand, have a positively charged functional group that attracts negatively charged ions.

To produce DI water, Hydrochloric Acid (HCI) is used to regenerate the cation resin. The positively charged Hydrogen (H+) then attaches itself to the negatively charged cation bead. The anion resin is regenerated with sodium hydroxide (NaOH) and the negatively charged Hydroxyl (OH-) attaches itself to the positively charged anion resin bead.

Now, the bonds between different ions are not the same; some are stronger and some are weaker. For example, calcium has a stronger bond between the cation resin than sodium. The H+ on the cation resin and the OH- on the anion resin do not have a strong attraction to the resin, allowing ion exchange to occur.

Therefore, as positively charged ions flow through the cation resin beads, the cations are exchanged for hydrogen (H+). Similarly, as negatively charged anions flow through the anion resin beads, the anions are exchanged for Hydroxyl (OH-). When the H+ and OH- combine, they form “pure” H2O. When all the exchange sites on the cation and anion resin beads have been used up and the tank is no longer producing DI water, the resin beads need to be regenerated to prepare them for reuse.

Note: While DI water is relatively clean and safe, it is not necessarily pure. This is because the deionization process does not remove pathogens, organic contaminants, or any impurities that do not have an electrical charge. Additionally, its purity depends on the type of contaminants in the source water and the pre-filtration method.

Types of deionized water

There are three types of deionization processes: co-current deionization, counter-current deionization, and mixed-current deionization.

Here’s a brief summary of how each one functions:

• Co-current deionization involves the standard down-flow process. In this process, both the feed water and the regeneration chemicals enter the top ion exchange column simultaneously and exit at the bottom.
• Countercurrent deionization involves water flowing from above and regenerative chemicals from below or vice versa. Compared to co-current deionization, countercurrent requires less time for regeneration, resulting in less regenerative chemicals used and lower overall costs.
• Mixed bed deionization involves a mixture of cation and anion resins in a single ion exchange column. This process usually requires a complex regeneration process that usually produces the best quality purified water of the three processes but at a higher cost.

10 common uses of DI water

DI water is the water of choice in various industries, mainly due to its high purity. Assuming the source water is tap water, spring water, or distilled water, DI water is pure enough to be used for almost all similar experiments and procedures.

Here are some applications of DI water:

1. Hand washing and disinfection

Thanks to its high purity, DI water is used in hospitals, doctors’ offices, and other medical facilities. These facilities use DI water to sterilize medical instruments and wash hands. The lack of minerals in deionized water prevents spots and residue when used to sterilize equipment, thereby preventing infection and cross-contamination.

2. Laboratory testing

When conducting laboratory experiments, getting the most accurate results possible is of utmost importance. That is why biologists and other laboratory professionals use DI water for various experiments and procedures. The mineral content and potential contaminants in regular water can distort test results, leading to unusual reactions, large financial losses, and even damage. DI water is therefore used for preparing solutions and cleaning instruments and materials.

3. Cooling system

Demineralized water has a low electrical conductivity. Therefore, it is suitable for cooling and lubricating equipment such as high-power lasers. It can prevent overheating in such equipment, which is why it is also used in other medical devices to help maintain the appropriate temperature.

4. Industrial machinery

If you have any experience in the manufacturing industry, you will know that industrial machinery is used a lot. Therefore, it needs to be cleaned regularly to avoid dirt accumulation. Regular water should not be used to clean industrial equipment because the mineral content in the water can cause parts to corrode much faster. For this reason, DI water is used to cool, clean and lubricate heavy machinery, increasing the life of the machinery.

5. Car maintenance

DI water is widely used to increase the life-span of lead-acid car batteries or car engine cooling systems. The ions found in regular water can cause engine rust, significantly reducing the life of lead-acid batteries. Therefore, DI water is preferred over tap water for use in car cooling systems.

6. Aquarium

Ensuring a favorable environment for marine life is crucial for their survival and well-being. So, if you own an aquarium, you need to fill it with water that is free of chlorine, copper, and all other contaminants that can harm your pet fish. Using DI water is ideal as it contains fewer impurities than regular water. It helps keep the marine life in the tank disease-free and prevents algae buildup on aquatic plants due to the lack of phosphates and silicates. Furthermore, DI water is of high quality and can therefore improve the overall health of your fish.

7. Food production and processing

Water quality is an essential part of food preparation and processing. As you may know, the water used to prepare food can affect the taste, nutrition, appearance, and most importantly, the safety of the food. Therefore, food manufacturing and processing plants use deionized water to wash fruits and vegetables, create food products, and process various foods. Even something as simple as tomato sauce is made with DI water.

8. Cosmetics and pharmaceuticals

From makeup to lotions, gels, and creams, DI water is a common ingredient in most cosmetic products. Water is used as a solvent to effectively transfer ingredients to your skin or hair. However, regular water can cause a host of problems when used in health and beauty products. For one thing, it can shorten the shelf life of a product. It can also aggravate existing skin conditions, such as blemishes, rashes, and eczema. In that case, manufacturers must create skin care and makeup products with the purest water possible – hence the need for DI water.

9. Cleaning house furniture

If you’ve ever used unfiltered water to clean glass doors, tabletops, computer screens, windows, and similar surfaces, you know the results can be disappointing. That’s because the dissolved salts and minerals in some water often leave behind unpleasant soap scum and mineral buildup on those surfaces. But because DI water contains no ions, it becomes an “ion magnet.” That means the ions in dirt are attracted to DI water, making it a great cleaning agent. Using DI water for cleaning and other household activities will give you brighter, smoother, cleaner windows and fixtures in your bathroom and kitchen. Furthermore, DI water’s zero mineral content leaves no mineral buildup and deposits that can damage delicate appliances and surfaces.

10. Fire fighting system

Demineralized water is also used in water mist fire suppression systems. These systems are used in sensitive environments, such as where high voltage electrical equipment and sophisticated electronics are used. Because DI water has a lower electronic conductivity than regular water, it will extinguish a fire without damaging the equipment as much as regular water.

Difference Between Deionized Water and Distilled Water

People often think of distilled water and deionized water as the same thing. However, there are some important differences between the two. Even the results they produce are less similar than you might realize.

Deionized water vs distilled water

DI water is produced by passing water through one or two charged resins. Unlike distillation, which removes most of the mineral ions and contaminants, deionization only removes ions from the water. Therefore, the water must be pre-filtered to remove organic matter, and then further filtered using an RO system to remove a significant amount of additional contaminants. This pre-treatment leaves only a small amount of ionized minerals for the DI system to remove.

Distilled water, on the other hand, is made by first boiling water into steam, then collecting the steam in a sterile container, where it condenses and turns back into water. Because water has a lower boiling point than most contaminants (including minerals), they are left behind when the water turns into steam. The resulting water is very pure – 99.9% of salts, minerals, and other organic and inorganic substances are removed. However, that does not mean that the distillation process removes everything. Impurities will evaporate and remain in the distilled water, especially if the water source is not pre-filtered and contains volatile organics and other specific contaminants.

How do they differ in usage?

Since deionization and distillation produce water of high purity, the choice between DI water and distilled water depends on how you intend to use it. Distilled water is typically purer, especially if it has been pre-filtered. If so, it should be free of any bacteria and other pathogens that may be present in DI water. Additionally, distilled water can be double or triple distilled, making it more suitable for most laboratory applications, including those where DI water is not pure enough.

That said, DI water is a great choice for many uses, including laboratory use, cooling applications, cosmetics, food and pharmaceuticals, and more. Unless very high purity water is needed, DI water is often the better alternative because you can produce it faster at a relatively lower cost.

What about the time and cost difference?

Distillation can take a relatively long time, especially when large amounts of water need to be boiled, cooled, and collected. Furthermore, distillation requires heat to boil the water and sterile containers to store it. Additionally, when distilled water is exposed to air over time, it essentially becomes deionized water..

On the other hand, deionization can be done relatively quickly, primarily if a mixed resin is used. This means that the water will only need to go through it once. Many DI water systems use two cartridges or mixed tanks to ensure that all ions have been removed. However, it is a quick process compared to distillation. Additionally, deionization is a chemical process, so energy is often required to monitor the process and move the water through the system. Additionally, if the DI resin is regenerated on-site, this can add time and cost to the process.

Advantages of Using Deionized Water

Depending on where it is used and what it is used for, deionized water may be a good choice.

Here are some of the benefits of DI water:

• High Purity: DI water is one of the purest types of water available to humans. No wonder why it is the water of choice for many manufacturers in various industries who want to avoid damage to machinery due to corrosion, build-up, and contamination of food, beverages, drugs, cosmetics, and other products.
• Non-corrosive: Due to the removal of minerals, DI water does not react with metals in a way that leads to corrosion.
• No residue: Since demineralized water contains no contaminants, it leaves no residue when the water is drained. It also minimizes mineral deposits and calcification.
• Low Conductivity: DI water has little or no ions and is therefore a poor conductor of electricity. This property is essential in situations where highly conductive water can cause damage and interference.
• Great Solvent: Deionized water is a unique solvent. It helps to combine different ingredients without adding minerals that can ruin the mixture or cause problems when applied.
• Fast Production Time: Although the deionization process can be complex, producing DI water is still faster than other processes used to create different types of water.

Risks of using deionized water

• Little or No Absorption of Calcium, Magnesium, and Other Nutrients: While water is not a major source of calcium, magnesium, and several other important minerals, the lack of them in DI water can put individuals at a higher risk of nutrient deficiencies. Considering that most modern diets are deficient in these minerals, a person may experience premature birth, heart disease, and bone fractures if their nutritional needs are not met from the foods they eat on a daily basis.
• Effects on intestinal mucosa, metabolism, mineral homeostasis and other body functions: It has been well established that drinking water with low mineral content will damage the homeostasis mechanism, affecting the body’s water and mineral metabolism.
• May increase the amount of toxic metals in your diet: Demineralized water is highly corrosive. This means it attacks water distribution pipes and containers, leaching metals into the water and increasing the amount of toxic metals you absorb. DI water can also leach plastics from containers made from plastic monomers and similar materials.
• It is considered to be less thirst-quenching: DI water is said to be less thirst-quenching. This is probably because there are no electrolytes in the water needed to replace what is lost through sweating and urination.
• Increased risk of tooth decay: Fluoride is added to public water systems to reduce tooth decay and other dental problems. But because fluoride is removed during the deionization process, a person may be at risk of tooth decay unless they practice proper oral hygiene.
• Bad/ Unpleasant Taste: Because DI water lacks the minerals that give water its flavor, it is said to have a poor taste. Some people complain that it tastes flat, with less flavor than regular water. Some also say that it feels strange and gritty on the tongue, although it does not burn or dissolve the tissues in their mouth. With this in mind, you may be forced to seek out other beverages like soda, which are bad for your health.

So, should you drink deionized water?

While deionization does not necessarily make DI water unsafe to drink, it is important to note that the process only removes ions. Other contaminants, including bacteria and viruses, are not removed during this process. Additionally, although DI water is typically made from treated water from a municipal source, it can leach contaminants from old pipes and carry them into your drinking glass. So unless you have a home water filter installed to improve your water quality, we do not recommend drinking DI water. Even if you do drink it, you risk missing out on important minerals and having water that tastes bad.

A better solution is to filter your tap water with a home water filtration system. These systems can remove various contaminants common in tap water while retaining its great taste and important minerals.

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Translator: Duong Nguyen Hoang Khang