Stabilization mechanism of reverse emulsions containing chromium (III): effect of interphase modification and dispersed phase viscosity

Abstract

The stabilization mechanism of concentrated and highly concentrated emulsions containing chromium (III) sulfate colloidal solution as dispersed phase is presented. It is concluded that the internal interphase is stabilized mechanically by a chromium (III)—dodecyl sulfate complex formed during emulsion preparation. Moreover, the dynamic viscosity of the colloidal solution plays a significant role in emulsion stabilization. Both formation of a mechanically stable interphase and the viscosity of the colloidal solution depend drastically on the initial composition of the phases. To derive the corresponding stabilization mechanism, we quantify this dependency by employing empirical modeling of the maximum content of the dispersed phase, taken as a measure of the emulsion stability. Analysis of the model reveals a complex interplay of the stabilization and destabilization processes involved which depend on the mechanical properties of both the interphase and the disperse phase. In particular, we demonstrate that the highest content of the dispersed phase can be achieved when the initial composition of the phases favors the formation of a stiff interphase and the viscosity of the dispersed phase is sufficiently high.

Graphical Abstract

Keywords:

• Reverse emulsion
• stability
• colloidal solution
• viscosity
• chromium

Acknowledgments

The authors sincerely thank Dr. Jürgen Hartmann for assistance with scanning electron microscopy imaging. V.L. sincerely thanks Dr. Florian Lovis for useful recommendations and constructive feedback on the manuscript and Prof. Dr. Ronald Imbihl for his kind hospitality. V.L., V.R. and G.B. dedicate this article to the memory of Prof. Boris Tanganov who sadly passed away during the revision process.

Additional information

Funding

This work was supported by DAAD (Deutscher Akademischer Austausch Dienst) and the Ministry of Education and Science of the Russian Federation (program “Mikhail Lomonosov II”), and successively by DAAD (Postgraduate research stay program).