Ion Exchange

Ion exchange has had a curious history. It has been known for almost a hundred years but the manifold applications as well as the complexity of the theoretical aspects are only a few decades old. This history has been characterized by its discontinuity in development. Two English soil scientists, Way and Thompson (1, 2) are credited with the discovery of ion exchange. Their work was concerned with the action of water-soluble fertilizer salts such as ammonium sulfate and potassium chloride and the curious fact that such salts could not easily be leached out from the soil by the action of rain water. The phenomenon then discovered remained dormant until the German chemist Gans in the year 1910, after studying the colloidal chemistry of aluminosilicates, realized that it could be applied to the softening of hard water (3, 4, 5). While the softening of water by naturally occurring mineral was known, the search for higher capacity materials such as synthetic aluminosilicate gels (6) and fused aluminosilicates (5) gave a new impetus to the water conditioning industry. None of these exchangers lend themselves to the exchange of hydrogen ions, and attempts by Borrowman to use huminlike substances (7) were commercially unsuccessful. In 1935, organic ion exchange materials t h a t could be used for hydrogen interchange were successfully prepared.