Assessing the arrest of coalescence due to Marangoni effects in flowing emulsions using population balance.

The conditions for coalescence arrest due to Marangoni effect of surfactant enriched emulsions flowing through a microfluidic device are analyzed. For that aim, we develop a Population Balance Equation model that allows the quantification of coalescence occurrence for emulsion systems at different surfactant concentration making use of isotherms. Besides, our model requires three parameters with physical significance to describe the behavior of the emulsions under shear to include Marangoni flow. The results were benchmarked by comparison to microfluidic experiments reported in the literature. Hydrodynamic coupling was observed at intermediate shear rates wherein coalescence was favored compared to the kinetics without surfactant. The coalescence kinetics was found to depend on the intertwined roles of both surfactant coverage and flow properties. These results represent a step towards the use of Population Balance Equation models not only for the study and prediction of conditions leading to coalescence arrest determined by either the external shear, repulsive barriers or Marangoni based forces but also for product design and control.