How de-alkalisation works.

De-alkalisation

De-Alk resin is a great way of reducing scale build up in hard water areas. It reduces temporary hardness to prevent scale from forming.

The process called dealkalisation means that the alkalinity ions are taken out of the water. The dealkalisation of water refers to the removal of alkalinity ions from water. Chloride cycle anion ion exchange dealkalizers remove alkalinity from water.

Chloride cycle dealkalisers operate similar to sodium cycle cation water softeners. Like water softeners, dealkalisers contain ion exchange resins that are regenerated with a concentrated salt (brine) solution – NaCl. In the case of a water softener, the cation exchange resin is exchanging sodium (the Na+ ion of NaCl) for hardness minerals such as calcium and magnesium.

A dealkaliser contains strong base anion exchange resin that exchanges chloride (the Cl– ion of the NaCl) for carbonate (CO− 3), bicarbonate (HCO− 3) and sulfate (SO2− 4). As water passes through the anion resin the carbonate, bicarbonate and sulfate ions are exchanged for chloride ions.

Higher capacities can be realised by use of type II rather than type I strong base anion resins. Although bicarbonates are not held as tightly as chlorides on the SBA (strong base anion) resins in the hydroxide form, when the resin is predominantly in the chloride form the pH has been raised by a small addition of caustic to the brine regenerant, there will be a favourable exchange of bicarbonate for the chloride. This exchange works well only with high alkalinity waters (40% to 80%), with capacities of 4 to 10 Kg/CF being obtained. The advantages of SBA resin dealkalisation is that low-cost salt is used in place of the acid necessary for the SAC (strong acid cation)and un-lined steel tanks can be used.