Ion exchangers are usually solid, macromolecular polyelectrolytes in the form of macroscopic particles with a porous structure. They are insoluble in water but capable of swelling. They are able to exchange bound ions against others dissolved in the surrounding medium. The cation exchangers (polyacids) carry fixed negatively charged functional groups (anchor groups grafted onto the polymer) with positive counter-ions, while the anion exchangers (polybases) have positively charged groups fixed onto the polymer with negative counter-ions to equalize the charge. Binding and release of the counter-ions are reversible processes and dependent on their concentration and affinity to the anchor groups.

There are inorganic ion exchangers which are natural aluminium silicates, e.g. Zeolites, which are used for water softening and desalting or Bentonite, which can be used for detoxification and as an adsorbent for proteins and viruses. Furthermore there are synthetic organic ion exchange resins, which are mainly produced by polymerization. They are of fundamental importance for many industrial applications and described below in more detail.

Ion exchangers on the basis of modified agarose, cellulose or dextran are used for the separation of large biomolecules, e.g. proteins or nucleic acids (see SERVACEL® Cellulose Ion Exchangers).

Adsorber resins have a similar basic matrix as ion exchange resins, but without functional groups. Binding of substances runs via non-ionic forces (see SERDOLIT®  PAD Resins).