Tj. Haverlock et al., APPLICABILITY OF A CALIXARENE-CROWN COMPOUND FOR THE REMOVAL OF CESIUM FROM ALKALINE TANK WASTE, Radiochimica Acta, 76(1-2), 1997, pp. 103-108
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.