Counterion exchange selectivity coefficients at water-in-oil microemulsion interface.
The counterion binding at a water/Aerosol-OT (AOT)/heptane microemulsion interface was treated in the context of the pseudo-phase ion exchange formalism. Two approaches were used to determine the selectivity coefficient for copper/sodium counterion binding at the AOT microemulsion interface: measurements of the Cu(II) concentration taken up by the reverse micelle in a Winsor II microemulsion system and steady-state emission quenching measurements of an anionic water-solubilized probe, the tris-(4,4'-dicarboxy-2,2'-bipyridine) ruthenium (II) ion. In addition, the selectivity coefficient for methyl viologen/sodium at the microemulsion surface was determined by the same photophysical technique. The value for copper (II)/sodium exchange (K(Cu/Na)) is 1.1+/-0.3 and that for methyl viologen/sodium (K(MV/Na)) is 0.9+/-0.3. The results show that the pseudo-phase ion exchange model can be used to obtain the selectivity coefficient in a microemulsion system.
Departamento de Qui;mica da Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, USP, Av. dos Bandeirantes, 3900, 14040-901 Ribeirão Preto, SP, Brazil.
Saulo A P
SA
Gonçalves
Silvia H
SH
De Pauli
Antonio C
AC
Tedesco
Frank H
FH
Quina
Laura T
LT
Okano
João B S
JB
Bonilha