EFFECT OF CROWN-ETHERS ON THE ION-EXCHANGE BEHAVIOR OF ALKALINE-EARTHMETALS - TOWARD IMPROVED LON EXCHANGE METHODS FOR THE SEPARATION AND PRECONCENTRATION OF RADIUM
Ml. Dietz et al., EFFECT OF CROWN-ETHERS ON THE ION-EXCHANGE BEHAVIOR OF ALKALINE-EARTHMETALS - TOWARD IMPROVED LON EXCHANGE METHODS FOR THE SEPARATION AND PRECONCENTRATION OF RADIUM, Analytical chemistry, 69(15), 1997, pp. 3028-3037
The effect of selected crown ethers on the uptake of alkaline earth ca
tions by sulfonic acid and diphosphonic acid-based cation-exchange res
ins from hydrochloric acid media is examined. The effect observed is s
hown to vary with the hydrophobicity of the crown ether, Water-soluble
crown ethers enhance the sorption of certain cations, thereby improvi
ng the selectivity of the resin for other alkaline earths over calcium
ion, an apparent result of a synergistic interaction between crown et
her present in the resin phase and the ionic functional groups of the
resin. In the presence of more hydrophobic crown ethers, a decrease in
cation sorption is often observed, a result of the exclusion of the c
rown ether from the resin phase and the formation of cation-crown comp
lexes in the solution phase, The result can be a reversal of the selec
tivity sequence ordinarily exhibited by the resin.