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Water Deionisation

Impurities in water are the result of ground mineral contamination, the measure of which is the electrical conductance of a sample of once centimetre cubed, displayed as a reading in uS/CM.

Untreated water would have a typical reading of between 100us/CM and 700us/CM (Town’s water) dependant on area. When Towns water is passed through a deioniser the impurities are retained within the plant and the resulting DI water will have, typically, 98% of impurities removed and will supply water from 0us to 30us.

A Good DI plant measures the impurities in the water continuously and when a present (adjustable) level is reached an automatic regeneration is initiated. This process removes the impurities from within the plant to drain.

There are typically TWO vessels on a Standard DI Plant one Filled with Cation Resin (+) and the second filled with Anion Resin (-)

Raw water enters the first Cation cylinder where the resin (regenerated) in the hydrogen (H) form this retains minerals and heavy metals, and for every molecule of impurity retained, a molecule of hydrogen is released (H) into the water;

CaCo3 -----RH+ -----H+Co3

The De Cat ionised water then passes into the second Anion column where the resin is in the hydroxyl form OH-, this retains the oxides and releases molecules of oxygen into the water.

H+Co3 ----- ROH -----H+OH ===H20

When the resin can no longer hold onto the molecules of impurities the conductivity begins to rise, when this reaches a pre-set point, usually 20 - 25 uS/CM, the plant automatically closes the service valve and begins to regenerate both Resins Automatically using Hydrochloric Acid and Sodium Hydroxide.

Deionisation removes not only calcium and magnesium ions as in the normal softening process, but also removes all other positive metallic ions and replaces them with hydrogen ions instead of sodium ions. This exchange of the hydrogen ions for metallic ions on an equivalent basis is chemical necessity that permits the exchange material to maintain a balance of electrical charges. Now because of the relatively high concentration of hydrogen ions, the solution is very acidic. This water then flows through a second unit, an anion exchange material which usually consists of hydroxyl anions and fixed cations. All the negative ions (anions) are absorbed and replaced by the hydroxyl anions which combine with the positive hydrogen ions from the first stage and leaves mineral-free, deionised water. Single bed units combine both the cation and anion exchangers in a single tank. Applications for deionised water include Pharmaceuticals, Electronic & Metal Finishing Industry.

At Adept we provide a full range of Water Deionisers to help get the production of water that you need. From single vessels systems like our I-on-x Exchange Cylinders to our Tri-on-x three vessel systems that are used to produce guaranteed water qualities higher than 1 Mega Ω (Ohm).

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