Sr(ii) extraction by crown ether in HFC: entropy driven mechanism through HPFTOUD.

The solvent extraction of Sr(ii) was carried out using dicyclohexano-18-crown-6 (DCH18C6) and two HFC mixed solvents MS1 and MS2, where MS1 was composed of 30/60 (w/w)% -1,2-dichloroethylene/HFC-43 (HFC-43: 1,1,1,2,2,3,4,5,5,5-decafluoropentane) and MS2 was 5/95 (w/w)% heptane/HFC-43. Nitric acid and perfuruoro-3-6-9-trioxaundecane-1,11-dioic acid (HPFTOUD) were used to study the effect of acid on the extraction. The maximum distribution ratio of Sr(ii) ( ) observed for HPFTOUD conditions was ∼180, and >10 times larger than aqueous nitric acid conditions.