https://doi.org/10.1007/s100510050192
Donnan equilibrium and the osmotic pressure of charged colloidal lattices
Instituto de Física,
Universidade Federal do Rio Grande do Sul,
Caixa Postal 15051, 91501-970 Porto Alegre (RS), Brazil
Corresponding author: a mtamash@if.ufrgs.br
Received:
26
June
1997
Revised:
3
November
1997
Accepted:
10
November
1997
Published online: 15 February 1998
We consider a system composed of a monodisperse charge-stabilized colloidal suspension in the presence of monovalent salt, separated from the pure electrolyte by a semipermeable membrane, which allows the crossing of solvent, counterions, and salt particles, but prevents the passage of polyions. The colloidal suspension, that is in a crystalline phase, is considered using a spherical Wigner-Seitz cell. After the Donnan equilibrium is achieved, there will be a difference in pressure between the two sides of the membrane. Using the functional density theory, we obtained the expression for the osmotic pressure as a function of the concentration of added salt, the colloidal volume fraction, and the size and charge of the colloidal particles. The results are compared with the experimental measurements for ordered polystyrene lattices of two different particle sizes over a range of ionic strengths and colloidal volume fractions.
PACS: 82.70.Dd – Colloids / 36.20.-r – Macromolecules and polymer molecules / 64.60.Cn – Order-disorder transformations; statistical mechanics of model systems
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1998