On the use of electrical conductance measurements for the stability of oil-in-water Pickering emulsions

Non-intrusive and continuous (on-line) techniques for the assessment of emulsion stability are of increasing interest. In this context, this work examines the potential of a new electrical technique (non-intrusive/continuous) against two traditional techniques, an optical technique (intrusive/intermittent) and a volumetric technique (non-intrusive/intermittent), for the assessment of the stability of Pickering emulsions. Surface modified hydrophilic particles (OS1, Sasol) were employed in making O/W Pickering emulsions. Experiments were performed with different water/oil volume ratios and particles concentrations. Emulsions stability was registered simultaneously by: (i) Electrical conductance signals taken continuously at a certain height inside the test vessel for determining the evolution of the local water fraction. (ii) Microscopy photos of samples withdrawn at regular intervals from the test vessel at the same height as electrical measurements for determining the evolution of the local droplet size distribution. (iii). Global volumetric measurements of the different phases (water, oil, emulsion) inside the test vessel made at regular intervals for determining the evolution of the location of the phases separation interface. Analysis of the results of each technique and comparisons among them are presented and discussed in detail.