Weakly Basic Anion Exchange ResinsDIAION™ series

Mitsubishi Chemical Corporation

Environment & Living Solutions

The weakly basic anion exchange resins use either a polystyrene or polyacrylic ester frame and a primary-ternary amino group as the functional group. Although the anion of a salt like NaCl or Na2SO4 cannot be exchanged, the exchange of an anion of a mineral acid such as HCl and H2SO4, or the salt of a weak base like NH44Cl can be carried out.

ION-EXCHANGE RESINS[Open in a new window]

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Resins using the primary-ternary amino groups as functional groups behave like weak bases and are therefore called weakly basic anion exchange resins.

Because the weakly basic anion exchange resin has a weakly alkaline functional group, in basic solution it does not dissociate and therefore has no ion exchange ability.
Although the anion of a salt like NaCl or Na₂SO₄ cannot be exchanged, the anion of a mineral acid such as HCl and H₂SO₄, or the salt of a weak base like NH4₄Cl can be carried out as shown in the reactions below.

R-NH₂＋　HCl　　→　R-NH₃Cl

R-NH₂＋　NH₄Cl　→　R-NH₃Cl　＋　NH₃

Weak acid is generally hard to capture, and although there is a resin with which H₂CO₃ is exchangeable, silicic acid (silica) cannot be exchanged.
An advantage of the weakly basic resin is that it is easy to regenerate. Of course NaOH, but even Na₂CO₃, NH₃, etc. can be used for regeneration. And this regeneration is economical as only slightly more than the theoretical chemical equivalent amount of regenerant solution is required.