Abstract
The aim of this study is the development of an emulsification device for two immiscible liquids with a total volume of approximately 3 mL. The heart of the device is a piston, with an aluminum plate fixed at its tip, which moves periodically up and down inside a rectangular cell. The plate geometry (uniform or non-uniform height) affects significantly both the emulsions stability and the size of the droplets of the prepared emulsions. Five parameters are examined during testing (surfactant type, surfactant concentration, proportion of immiscible liquids, piston stroke frequency, duration of emulsification) and all of them appear to have an important role in the resulting droplet size distribution. A macroscopic theoretical model is developed for the determination of the main hydrodynamic parameters of the innovative device. It is shown that the non-uniform height plate achieves higher shear rates when compared to the uniform height plate because of the smaller gap between the plate and the cell walls. However, the benefits of the higher shear rate are overturned by the larger effective breakage time encountered in the uniform height plate resulting from the larger surface area of its sides. The results of the emulsification experiments are analyzed using the parameter values derived by the developed model.
Highlights
Emulsions constitute a topic of great interest in the scientific literature because of their significance in a multitude of industrial applications
It is noted that probability density function (PDF) is a density function, it has inverse length units and it has to be integrated among two droplet sizes to give the percentage of the droplets having size between the particular values
Evaluation of the produced emulsion stability is investigated by means of (i) the evolution of phases separation versus time and (ii) the initial oil droplet size distribution
Summary
Emulsions constitute a topic of great interest in the scientific literature because of their significance in a multitude of industrial applications. Emulsions are widely applied in foods, cosmetics, pharmaceuticals, agriculture, oil and petroleum industry, etc., [1]. They are heterogeneous systems consisting of two immiscible liquids, where droplets of the first liquid (dispersed phase) are dispersed inside the second liquid (continuous phase) [2,3,4,5]. Many different destabilization processes may take place during emulsion storage, with sedimentation, flocculation, coalescence, phase inversion, and Ostwald ripening of dispersed droplets being the most important among them [10]. Several parameters like the volume of the dispersed phase, the droplet size distribution, the surfactant concentration, and the continuous phase viscosity have been found to play an important role on emulsions stability [11,12,13]
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