TRANSPORT OF CESIUM FROM REPROCESSING CONCENTRATE SOLUTIONS THROUGH FLAT-SHEET-SUPPORTED LIQUID MEMBRANES - INFLUENCE OF THE EXTRACTANT

The influence of the extractant on cesium transport from nuclear fuel reprocessing concentrate solutions to demineralized water through flat -sheet-supported liquid membranes (FSSLMs) was studied using four crow n ethers of different lipophility: dibenzo-21-crown-7 (DB21C7), benzo- 21-crown-7 (B21C7), t-butylbenzo-21-crown-7 (tBuB21C7), and n-decylben zo-21-crown-7 (nDecB21C7). The distribution coefficients of cesium sho w that the four crown ethers have similar extraction capacities which follow the sequence nDecB21C7 > tBuB21C7 > B21C7 >; DB21C7. DB21C7 and B21C7 cannot be used in cesium transport experiments due to the low o rganic solubility of the former and the great tendency of the latter t o form a third phase between the organic phase and the aqueous extract ion phase. Of the other two crown ethers, nDecB21C7 leads to faster ce sium transport than tBuB21C7 due to the stronger lipophilic character of the former; this allows a higher crown-ether concentration in the m embrane to be obtained when nDecB21C7 is used.