Ion exchange water treatment system is one of the most common processes and it is works on the basis on ion exchange principle. It removes the scale-forming calcium and magnesium and others metal ions from hard water. To removes these ions water are passes through ion exchange column filled with synthetic resin.
Ion exchange column
There are two type ion exchange column; cation exchange column and anion exchange column. In cation exchange column selectively cations are adsorb, on the other hands in anion exchange column selectively anions are adsorbs from supplied water and release same type of ions. Depends on application only cation exchange column or both ion exchange column are used for water treatment. For boiler and demineralised water needs both ion exchange column.
Cation exchange column
The column that filled with the resins containing base exchanging radicals are called cation exchange column. Sodium or hydrogen cation exchangers are generally used in this column. Hydrogen cation exchanger is used to remove all cations from water including sodium ion. The process of ion exchange will continue until available cations are packed. Then it should be need regeneration with suitable chemicals. The following reactions are taken place in cation exchange column.
2HR + Ca(HCO3)2 → CaR2 + 2H2O + 2CO2
2HR + 2NaHCO3 → 2NaR + 2H2O + 2CO2
2HR + MgSO4 → MgR2 + H2SO4
Regeneration: MgR2 + H2SO4 → 2HR + MgSO4
Anion exchange column
The column that filled with the resins containing acid exchanging radicals are called anion exchange column. Here OH- ion is exchanged for the anion. The process of ion exchange will continue until available anions are packed. Then it should be need regeneration with suitable chemicals such as caustic soda. The following reactions are taken place in anion exchange column.
H2SO4 + 2R4NOH → (R4N)2SO4 + 2H2O
Regeneration: (R4N)2SO4 + NaOH → 2R4NOH + Na2SO4
The softening water by Ion exchange water treatment system can be used all purpose, even boiler. Because of the process removes all ions and acids from water. To produce house hold water, laundry process water it should be used sodium cation exchanger only. In this case regeneration is completed by passing a NaCl solution through the resin.