APPLICABILITY OF A CALIXARENE-CROWN COMPOUND FOR THE REMOVAL OF CESIUM FROM ALKALINE TANK WASTE

In terms of extractive strength and selectivity over sodium, calix[4]a rene-bis-(2,3-naphtho-crown-6) exhibits superior properties in compari son with simple crown ethers for separating cesium from an alkaline so lution simulating a Hanford tank supernatant waste. The calixarene was studied at 0.01 M in four diluents. In two cases a cesium distributio n coefficient near unity was obtained. Successive water washes suffice d to strip the loaded solvents. In addition, selectivity ratios for ce sium over sodium exceeded 10(4) for all of the diluents. By contrast, bis-(tert-butylbenzo)-21-crown-7 gave distribution coefficients an ave rage of 200 times lower under identical conditions; its selectivity ra tio for cesium over sodium was at best 200 in one of the four diluents tried. Although Cs/Na selectivity in the case of the calixarene is so high as to make Na+ ion extraction inconsequential, Cs/K selectivity lay in the lower range 122-935. Owing to the relatively high concentra tion of K+ ion in the waste, strong competition due to K+ ion extracti on resulting in high loading of the calixarene was observed to limit t he effectiveness of cesium extraction and stripping. For both the cali xarene and crown ether, extraction strength correlates with the empiri cal solvent polarity parameters DP and E-T.