The kinetics of extraction of actinides and fission products at the liquid-liquid interface

The rate-controlling step in the extraction of lanthanides and actinides from aqeous systems by organophosphorous reagents may involve diffusion in either phase, complex formation or the elimination of water from ionic solvation layers. An analytical ultracentrifuge was employed to monitor the transport phenomena of the aforementioned elements at various concentrations. Simultaneous use was made of two different optical systems. Under the influence of a centrifugal field, artificial liquid-liquid interfaces may be easily created, whereby the use of the optical systems facilitates the observation of extraction phenomena from the very onset of reaction. In these unstirred solutions experimental data have been obtained by use of an Analytical Ultracentrifuge, for regions much closer to the interface of immiscible liquid-liquid systems than have hitherto been reported. The behaviour of the actinides and fission products could thereafter be monitored at these boundaries as desired. By considering the various laws of diffusion and the results of experiments involving these elements in single-phase systems using the same technique, it has proved possible to describe effectively the kinetics of extraction and isolate the principal rate-determining steps at the interface