DOWEX Ion Exchange Resins WATER CONDITIONING MANUAL

Ion Exchange Resin Operational Information
Figure 23. Type 1 strong base anion resin: salt splitting capacity loss vs. temperature.
Reference Document: Tech Facts 177-01751
9.6.2 Oxidation
Exposing an ion exchange resin to a highly oxidative environment can shorten resin life by attacking the
polymer crosslinks, which weakens the bead structure, or by chemically attacking the functional groups.
One of the most common oxidants encountered in water treatment is free chlorine (Cl2). Hydrogen
peroxide (H2O2), nitric acid (HNO3), chromic acid (H2CrO4), and HCl can also cause resin deterioration.
Dissolved oxygen by itself does not usually cause any significant decline in performance, unless heavy
metals and/or elevated temperatures are also present to accelerate degradation, particularly with anion
exchange resins.
When a strong base anion resin experiences chemical attack, the polymer chain usually remains intact,
but the quaternary ammonium strong functional group (trimethylamine for type 1 anion resins) splits off.
Alternately, the strong base functional groups are converted to weak base tertiary amine groups, and the
resin becomes bifunctional, meaning it has both strong base and weak base capacity. The decline in
strong base (salt splitting) capacity may not be noted until more than 25% of the capacity has been
converted.
Although weak base anion resins are more stable than strong base anion resins, they can oxidize and
form weak acid groups. When this occurs, the resin tends to retain sodium and requires a greater than
normal volume of rinse water following regeneration.
Cation exchange resins are more thermally stable than anion exchange resins. Chemical attack on a
cation exchange resin usually results in the destruction of the polymer crosslinks, resulting in an increase
in water retention capacity and a decrease in the total wet volume exchange capacity. Although it is not
possible to accurately predict resin life when other factors are considered, the following guidelines for
feed water chlorine levels will maximize the life of cation resins (Table 19).
DOWEX Ion Exchange Resins 53 Water Conditioning Manual