Ion Exchangers are insoluble granular substances which have in their molecular structure acidic or basic radicals that can exchange. The positive or negative ions fixed on these radicals are replaced by ions of the same sign in solution in the liquid in contact with them.
The ion exchange is complete without:
Now days, the ion exchange substances are used almost exclusively under the name of resins. There are two categories of resins: the resins of the gel type and those of the macroporous or loosely cross-linked type. Their basic structure is identical: the macromolecular structure is obtained in both cases by copolymerization. The difference between them lies in their porosity.
|Gel type resins have a natural porosity limited to intermolecular distances. It is a microporous type structure|
|Macroporous type resins have an additional artificial porosity which is obtained by adding a substance designed for this purpose.|
The exchanger is known as monofunctional if there is only one variety of radicals and it is called polyfunctional if the molecule contains various type of radicals.