ION EXCHANGE Update 5 July 2009

Limits of use of anion exchange resins

Anion exchange resins are sensitive to temperature, as heat may damage or destroy the functional groups, and to organics, which may cause fouling.

The temperature limit is valid for permanent exposure in service, and for regeneration.

The limit of organic load corresponds to the quantity of organics passing through the resin during one run. Not all the organic matter is removed!

Another way of assessing the suitability of the resin without calculation of the organic load is to use the fouling index of the water. This fouling index is defined as:

Fouling index

Maximum temperature and organic load for anion resins
Resin Type Maximum
Temperature
(°C)
Maximum
Organic Load
g as KMnO4
per L resin
Maximum
Acceptable
Fouling Index
N
SBA styrenic type 1, gel 60 2 3
SBA styrenic type 2, gel 35 3 6
SBA styrenic type 1, macroporous 60 4 6
SBA styrenic type 2, macroporous 35 5 10
SBA acrylic 35 8 15
SBA Acrylic, macroporous 60 15 18
SBA nitrate selective, macroporous 35 2 3
Bifunctional acrylic 25 10 15
WBA styrenic, macroporous 60 12 12
WBA acrylic, gel 60 25 20
WBA boron selective 40 5 6

The organics here are natural organic matter found in surface waters. The table is not valid for other organic impurities. Water treatment only: in some special applications, higher temperatures may be used. The ionic load of the SBA resins is not shown; the resins are assumed to operate in demineralisation cycle, i.e. regenerated with NaOH.

Sensitivity to organics and temperature may vary according to the properties of the resin, notably their porosity. However the above data can be considered as a good guideline.

The "Total Anions" value shown in the fouling index are those forming the anionic load of the resin, after degasifier if any. It is difficult to calculate for WBA/SBA couples.


© François de Dardel