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262 4. Adsorption and Ion Exchange

Figure 4.12 Amine groups for the manufacture of chelating resins.

removed from the liquid by means of a magnetic f an inor ield, xchanger containing ganic e
magnetite can be used (IAEA, 2002). Another reason in for of composite ion e a v xchang-
ers is that in this way, a granular material appropriate for column use may be formed from
ion exchangers that normally do not form or only form weak granules themselv as long es,
as a proper inorganic binder is used.

esins Chemical stability of r
The chemical stability of resins may be degraded due to chemical interactions with oxi-
dizing agents. The latter interact with CH 2 groups and gradually lead to the destruction of
the matrix. The main oxidizing substances are

• O 2 at high temperatures
• H 2 O 2 leads (Fenton reaction) to the complete dissolution/destruction
• O 3 splits aromatic double bonds
xchangers,
• C l 2 decomposes cation e and oxidizes amino and ammonium groups of
xchangers anion e
• CrO 3 (chromic acid) destroys the cross-linking of cation e xchangers
• a N 2 S O 2 8 separates functional groups of anion e xchangers
xchangers,
• HNO 3 may damage polycondensation cation e easily damages functional
groups of anion e xchangers.
v
However, reductie agents may also affect resins. For e hydrogen may damage xample,
sulfonic acid groups of strongly acidic cation e xchangers.

4.1.3 Kinetics

Ion exchange shares many characteristics with adsorption, such as mass transfer from the
v
er
fluid to the solid phase; there are, ho some significant differences. Specif , ically
we
,
although both processes can be characterized as sorption processes, the sorbed species are
xchange,
ions in ion e whereas electrically neutral substances are sorbed in adsorption.
v
Moreover, in ion e the ions remoed from the liquid phase are replaced by ions
xchange,
al from the solid phase. So, there actually occurs an e xchange of ions and not only a remo v