  Theoretical calculations of the mixed aggregation/coalescence (kFC) rate
corresponding to a set of hexadecane-in-water nano-emulsions stabilized with
sodium dodecyl sulphate (SDS) at different NaCl concentrations are presented.
The rates were obtained through the change of the total number of aggregates of
the dispersions as a function of time, predicted by Emulsion Stability
Simulation (ESS). Two different models were implemented in order to mimic the
dependence of the surface excess of the surfactant on the salt concentration.
Experimental measurements of kFC were also made, based on the change of the
turbidity of the emulsions as a function of time. A satisfactory agreement
between theory and experiment is only attained if the model of surfactant
adsorption accounts for the balance between the salting out of the surfactant
solution and the partial screening of the surface charge of the drops induced
by the increase of the ionic strength of the continuous phase. The observed
behavior cannot be justified on the grounds of the
Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Instead, the reversible
flocculation of the aggregates of any size is proposed as an alternative
mechanism to explain the dependence of kFC as a function of the salt
concentration.

Soft Condensed Matter