Ion Exchange refers to the process where a contaminant ion from the water is exchanged for a presaturant ion in solid phase from a resin, typically in a reversible chemical reaction so that the resin can be easily regenerated. Naturally, some degradation will occur after a certain number of regeneration cycles and the resin bead will have to be replaced. For numerous applications, an ion exchange resin bead or alumina granules is commonly used.
Activated alumina is very useful in order to remove arsenic, selenium or fluoride from water. It presents the disadvantage of having poor regeneration efficiency.
The resin bead used for ion-exchange are typically composed of a polymer matrix where the functional groups are attached through covalent bonding, The matrix is usually polystyrene cross –linked with 3 to 8% divinylbenzene,
Regarding the functional group resins are categorized in four different groups:
1) Strong Acid Cation (SAC)
2) Weak Acid Cation (WAC)
3) Strong Base Anion (SBA)
4) Weak Base Anion (WBA)
Typically, a SAC resin is commonly used for several water softening applications. WAC resins can be used for water softening applications where there is only carbonate hardness. SBA resins are very efficient in removing nitrate while WBA are rarely used for water treatment applications.
A properly designed ion-exchange water treatment process provides a cost-effective solution for mineral contaminants removal. With more than 3000 projects executed worldwide and over 300 years of combined experience the designers at Napier-Reid have the solution for all your water treatment requirements