Solvent extraction of sodium perrhenate by 3m-crown-m ethers (m=5, 6) and their mono-benzo-derivatives into 1,2-dichloroethane:: Elucidation of an overall extraction equilibrium based on component equilibria containing an ion-pair formation in water

Equilibrium constants (K-MLA(0)/mol(-1) dm(3)) for the ion-pair formation of a complex ion NaL+ with ReO4- in water were determined potentiometrically at 25 degrees C and the ionic strength (I) of 0 mol dm(-3) using a Na+-selective electrode. Here, crown ethers, L, were 15-crown-5 ether (15C5), benzo-15C5, 18-crown-6 ether (18C6) and benzo-18C6. Also, NaReO4 was extracted by the L into 1,2-dichloroethane and then extraction constants (K-ex/mol(-2) dm(6)) for the species, NaLReO4, were determined at 25 degrees C by AAS. These K-ex values were resolved into four component equilibrium constants containing K-MLA calculated at given I values. Based on these data, extraction-abilities of the L against the perrhenate were discussed in comparison with those of sodium picrate-L systems reported previously. (c) 2006 Elsevier B.V. All rights reserved.