Application of Kapton nuclear track microfilters in liquid-liquid extraction of actinoide elements

Kapton Track Microfilters (KTM) are used to separate emulsions formed by two strongly mixed immiscible liquid phases. Many different organic diluents and solvents (the organic phase) have been tested. The aqueous phase was 2N HNO3. Kapton filters with a range of pore sizes (inner diameter (d) = 3 μm < d < 13 μm) have been used in order to get a complete separation of the organic part of the emulsion under well-defined conditions. Best results were obtained from filters with pore sizes of approximately 7 μm. About 90% of the organic phase passed through the filter within one minute. The time needed to extract the remaining 10% varied from 5–15 minutes depending on the type of organic liquid. After the separation of the organic phase was completed, the process stopped by itself, leaving the pure aqueous phase behind. To get a complete separation and reproducible results, the filter has to be wetted with the appropriate organic phase before use. The use of these filters for liquid-liquid extraction of actinides, such as the system Np-237 out of pure nitric acid solutions or solutions containing uranium in high concentrations was investigated. The filters were quite useful for these extractions, giving yields of almost 100%.