Demineralization is the removal of all cations (e.g. calcium, magnesium, sodium, potassium, Iron and other heavy metals) and all anions (e.g. bicarbonate alkalinity, chloride, sulfate, nitrate, silica and CO2) from a solution, typically water. The cations are replaced with H+ ions and the anions are replaced with OH- ions to form water. This reduces the total dissolved solids of the solution.
Where is it needed?
- High Pressure Boiler Feed
- Sugar Processing
- Rinse Water for Electronic Devices
- Process Water for Various Industrial Applications
- Water for Laboratories
How does it work?
- Cations are exchanged for H+ ions on a SAC resin
- Anions are exchanged with OH- ions on a SBA resin
- H+ and OH- form pure water
- Each resin is regenerated separately to return them to the H+ and OH- forms using acid and caustic, respectively.
Mixed Bed Demineralization
There are many applications where the cation and anion resins can mixed together in a single vessel as a mixed bed. This configuration can be used for primary demineralization or as a polishing step following a two bed or multi-bed system.
Additional Equipment Considerations:
- Weak Acid Cation (WAC) resins can be used prior to a SAC resin – these will only remove cations associated with alkalinity.
- Weak Base Anion (WBA) resins can be used prior to an SBA resin – these will only remove free mineral acidity (FMA), meaning SO4, Cl, and NO3.
- A degassifier can be placed prior to an SBA vessel to reduce the load of alkalinity down to 6-12 ppm as CaCO3.