Selective extraction of strontium with supercritical fluid carbon dioxide

Strontium (Sr2+) can be selectively extracted from aqueous solutions into s upercritical fluid CO2 at 60 degrees C and 100 atm with dicyclohexano-18-cr own-6 (DC18C6) using CF3(CF2)(6)CO2- (PFOA(-)) or CF3(CF2)(6)CF2SO3- (PFOSA (-)) as a counter anion; at a mole ratio of Sr2+ : DC18C6 : PFOA(-) = 1:10: 50, the extraction of Sr (5.6 x 10(-5) M) from water at pH 3 is near quanti tative whereas Ca2+ and Mg2+ at equal concentration are only extracted to a level of 7 and 1%, respectively; PFOSA(-) is an effective counter anion fo r selective extraction of Sr2+ from 1.3 M HNO3 with DC18C6 in supercritical CO2.