DI water systems produce highly purified water by removing dissolved mineral ions through a process called deionization. This results in water that is essential for many industrial, laboratory, and medical applications where mineral content is detrimental.
The Core Process: Ion Exchange
According to the reference, a deionization water treatment system is an arrangement of tanks that deionizes water through the ion exchange process. This is the fundamental mechanism by which these systems operate.
Instead of filtering out contaminants based on size, like many other water purification methods, deionization removes charged particles (ions) by swapping them with other ions that don't form mineral impurities.
Key Components
A typical DI water system involves specific components designed to facilitate this ion exchange:
- Tanks: The system is often an arrangement of tanks holding the resin.
- Resin Bed: Water is forced through a resin bed. This bed contains millions of small, porous plastic beads called ion exchange resins. The reference notes this can be in a pressure tank or in a drop-in cartridge inserted into a tank.
How Ions Are Removed
The ion exchange process within the resin bed is where the purification happens:
- Water Flow: Untreated water containing dissolved mineral ions flows into the tank and is forced through the resin bed.
- Ion Attraction: The resin beads have specific electrical charges and properties that attract dissolved ions. As the reference states, mineral particles attach to resin beads with the corresponding electrical charges.
- The Exchange: The resin beads effectively swap the mineral ions in the water for hydrogen (H⁺) and hydroxyl (OH⁻) ions that are part of the resin structure.
- Positively charged mineral ions (like Calcium Ca²⁺, Magnesium Mg²⁺) are exchanged for H⁺ ions by cation exchange resins.
- Negatively charged mineral ions (like Chloride Cl⁻, Sulfate SO₄²⁻) are exchanged for OH⁻ ions by anion exchange resins.
- Pure Water Formation: The exchanged H⁺ and OH⁻ ions combine to form pure water (H₂O), which is essentially free of the dissolved mineral ions.
This continuous swapping action results in water with extremely low conductivity, indicating very few dissolved ions.
What Ions Are Typically Removed?
Deionization is effective at removing a wide range of dissolved ions, including:
- Cations (Positive Charge): Sodium (Na⁺), Calcium (Ca²⁺), Magnesium (Mg²⁺), Potassium (K⁺), Iron (Fe²⁺/Fe³⁺), Manganese (Mn²⁺).
- Anions (Negative Charge): Chloride (Cl⁻), Sulfate (SO₄²⁻), Nitrate (NO₃⁻), Carbonate (CO₃²⁻), Bicarbonate (HCO₃⁻), Silica (SiO₂).
It's important to note that DI systems do not effectively remove non-ionic contaminants like bacteria, viruses, or dissolved organic compounds. Often, DI is used as a polishing step after other purification methods like reverse osmosis.
In summary, DI water systems work by using the chemical process of ion exchange within a resin bed to remove dissolved mineral ions from water, resulting in highly purified water.
