Stability of phenol-formaldehyde ion-exchange sorbents in aqueous solutions

It is shown that ion-exchange sorbents based on phenol-formaldehyde resins can be used for a long time for isolating and separating rare alkali metals without any significant changes in the ion-exchange selectivity and capacity. When the phenol sorbents were used in alkaline solutions at elevated temperatures, carboxyl groups gradually accumulated in them as a result of the oxidation of methylol groups with oxygen dissolved in the solution. This led to a considerable increase in the ion-exchange capacity of the sorbents and a simultaneous decrease in the selectivity with respect to Cs + -Rb + and Rb + -K + ions (it is desirable to avoid the drying of phenol ionites in air by storing them in a swelled state in closed vessels).