Deionisation can remove dissolved solids from water through ion exchange techniques. This process effectively removes significant amounts of organic and inorganic substances dissolved in tap water, such as pesticides, fertilisers, sodium, and calcium compounds.
The resulting liquid is called deionised water.
In this post:
The Process of Deionisation
Mains and untreated water contain dissolved ions. The amount of ions depends on several environmental factors, such as the proximity of the water source from farms. Some inorganic fertilisers might be mixed with the water.
Below are the most commonly abundant ions in water:
Cations, or positively charged ions:
- Calcium (Ca)
- Magnesium (Mg)
- Sodium (Na)
- Potassium (K)
Anions, or negatively charged ions:
- Bicarbonate (HCO3)
- Chloride (Cl)
- Sulphate (SO4)
Watch our video to find out more about ReAgent’s deionisation process:
Ion exchange
These ions can be harmful to health, as well as to water pipes. One way of removing them is through the deionisation process. This process basically involves attracting ions to their corresponding opposite charges. The ions either precipitate as solids, or the gaseous components are released.
In industrial and commercial processes, ion-exchange resin is used. This resin is a polymer that functions as the medium for ion exchange.
The water to be purified passes through a matrix or a support structure of an ion-exchange resin in the form of microbeads with about 0.25 – 1.43 mm radius.
The small size of these beads creates a large surface area for the water, effectively trapping undesired dissolved ions while releasing other ions.
Key Takeaways
Deionisation is a commercial-industrial method of purifying water
There are several common ions dissolved in water, such as sodium, calcium, and carbonates
The dissolved ions can cause health issues and possible damage to water pipes
Ion-exchange resins are organic polymer beads that trap unwanted ions while releasing others
The deionisation process has several applications, such as laboratory testing
Key Components of a Deionisation System
A deionisation system has at least three main or key components. Central to these are the deionising resins. The other two key components are the pump and tanks.
Supporting components include pipes with valves, a pH metre, and the beater.
What Are the Uses of Deionised Water?
Deionised water has many applications in industry, medicine, laboratory, cosmetics, and pharmaceuticals. It’s very useful because of its electrical non-conductivity. For example, it is ideal for calibrating instruments.
Here are some examples of the major applications of deionised water:
- Precise laboratory experiments
- Pharmaceutical and medical use
- Electronics and manufacturing
- Automotive industry
- Food and beverage manufacturing
- Printing and photography
Let’s look at each of these in a little more detail…
Precise laboratory experiments
Lab experiments involving molar concentrations, neutral pH, and electrical conductivity are more reliable when you use deionised water.
The absence of ions in water means that experiments can be repeatable because of the precise measurements that can be taken.
Pharmaceutical and medical use
Medicines require a high degree of precision in formulation, so using deionised or a high grade of purified water is essential. Slight changes in a formulation could be dangerous in that the medicine’s efficacy and properties could change.
There are also medical procedures, such as dialysis, that require deionised water to prevent complications.
Electronics and manufacturing
Deionised water is used to clean circuit boards. It removes flux residues while not affecting the conductivity of the circuits or causing corrosion.
Automotive industry
Deionised water is often mixed with antifreeze and coolants to prevent rust and the formation of scale in engines. This type of water is also used in car batteries.
Food and beverage manufacturing
Processing food and beverages requires a high level of cleanliness. Using deionised water can help prevent contamination and the growth of microorganisms.
Power plants
Using deionised water in boilers prevents corrosion and scale buildup. It’s also used in high-pressure steam generation where the absence of ions prevents damage to turbines.
Deionisation vs. Other Purification Methods
Deionisation is sometimes used interchangeably with other methods of water purification, but there are major differences. Here are some comparisons.
Deionisation vs. Reverse Osmosis
The deionisation process removes ions through ion exchange, while reverse osmosis removes ions by forcing water to pass through a semipermeable membrane, leaving solutes behind.
Deionisation vs. Distillation
Distillation is a process that involves heating the water, evaporating it, then condensing it in a separate container, leaving dissolved solids behind.
However, some solids may still be attached to the water vapour as it evaporates and becomes steam.
The deionisation process does not involve heat. You can read more about distilled vs. deionised water here.
Conclusion
Deionisation involves ion exchange using resin beds. It has several practical applications in various fields, such as in manufacturing medicines. It is comparable or even superior in some cases to other methods of water purification.
