A mixed extractant solvent including
calix[4]arene-bis-(tert-octylbenzo)-crown-6 ("BOBCalixC6"),
4',4',(5')-di-(t-butyldicyclo-hexano)-18-crown-6 ("DtBu18C6"), and at
least one modifier dissolved in a diluent. The mixed extractant solvent
may be used to remove cesium and strontium from an acidic solution. The
DtBu18C6 may be present from approximately 0.01 M to approximately 0.4M,
such as from approximately 0.086 M to approximately 0.108 M. The modifier
may be 1-(2,2,3,3-tetrafluoropropoxy)-3-(4-sec-butylphenoxy)-2-propanol
("Cs-7SB") and may be present from approximately 0.01M to approximately
0.8M. In one embodiment, the mixed extractant solvent includes
approximately 0.15M DtBu18C6, approximately 0.007M BOBCalixC6, and
approximately 0.75M Cs-7SB modifier dissolved in an isoparaffinic
hydrocarbon diluent. The mixed extractant solvent may form an organic
phase in an extraction system that also includes an aqueous phase.
Methods of extracting cesium and strontium as well as strontium alone are
also disclosed.