Abstract
Under certain conditions ion–ion correlations play a crucial
role in the description of the electrical double layer of colloidal
particles. In fact, in many instances, the inclusion of the short
range correlations between ions in the study of the ionic distribution
leads to quite different results with respect to the classical treatment
(where ions are assumed to be points). In particular, these discrepancies
become more noticeable for highly charged particles in the presence
of moderate or highly multivalent counterion concentrations. Moreover,
it can be shown that the existence of an electrolyte mixture consisting
of multi-~and monovalent counterions may cause that system to become
overcharged, a feature that cannot be predicted from a classical
point of view based on the Boltzmann distribution function. Precisely
this aspect has recently produced an enormous interest in the field
of biophysics since small variations in the physiological conditions
of biocolloidal systems (e.g.~the addition of a multivalent salt)
can induce important changes in their behaviour. In order to determine
the relevance of ion correlations in electrolyte mixtures, we present
some experimental results on the electrophoretic mobility of latex
particles in the presence of different 1:1 and 3:1 salt mixtures.
Likewise, these results are analysed within the so-called hypernetted-chain/mean
spherical approximation where ion size correlations are taken into
account.
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