ABSTRACT
Ion exchange is used to detect and measure dissolved pollutants in water. It is used in two ways: first, to collect and concentrate traces of impurities from large volumes of water, and second, to separate various substances of interest after they have been concentrated. Ion exchange is a competitive process, and it is effective for preconcentration only if the exchanger is selective for the ions of interest. A new technique called "reactive ion exchange" can be used to collect trace elements from water. It consists of incorporating in the ion-exchange column an ion that will react selectively with the ionic species to be collected and fixing it in the column. Once trace metals have been concentrated into a small volume of solution, ion exchange can be used in well-known ways to separate the metal ions. The separation can often be carried out on the same column that was used for preconcentration.
