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Behavior of Emulsions and Microemulsions
Published in Victor M. Starov, Nanoscience, 2010
In the simplest case, two single-phase compositions of a simple ternary system such as o/w/alcohol are chosen in such a way that when one is added to the other, the composition passes directly form the single-phase region of the relevant ternary phase diagram into the portion of the two-phase region between the binodal and spinodal curves. Phase transformation occurs in the resulting supersaturated liquid by nucleation and growth, not by spinodal decomposition. Moreover, for a substantial portion of this supersaturated region homogeneous nucleation produces many small droplets almost immediately on mixing with the final emulsions being reasonably monodisperse and having drops that are a few micrometers in diameter. This phenomenon has been called the “ouzo effect” by Vitale and Katz [22] because such emulsification causes the alcoholic drink known as ouzo to appear white when it is diluted with water.
NanoemulsionsPreparation, Stability, and Application in Food
Published in C. Anandharamakrishnan, S. Parthasarathi, Food Nanotechnology, 2019
P. Karthik, Sayantani Dutta, C. Anandharamakrishnan
True SE occurs when two immiscible liquids in contact mix without any external influence (thermal or mechanical); it is influenced by solvents, with or without the presence of surfactants (Komaiko, 2016). When this mixing occurs with oil, water, and water-miscible solvents, the process is called “Ouzo effect” (Ganachaud and Katz, 2005; Komaiko, 2016). A schematic flow sheet of preparation of nanoparticles by the said technique has been summarized in Figure 8.5.
Microemulsion fuel formulation from used cooking oil with carbinol as the dispersion phase
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
In this study, microemulsion-based biofuels are formulated from UCO using carbinol and butan-2-ol. The formation of the Winsor Type IV stable microemulsion system was confirmed due to the appearance of nano-sized particles observed in the DLS study. Blend containing 50% UCO, 25% carbinol, and 25% butan-2-ol has been identified as the optimum. The major findings on the basis of this study are The droplet size distribution study estimated the particle size to be between 12 and 50 nm, which confirmed the formation of the reverse micellar system.Identified Optimum blend UCO:carbinol:Butan-2-ol(50:25:25) having a density of 0.862 g/cm3 with a calorific value of 31.15 MJ/kg and a viscosity of 5.74 cSt.The fatty acid composition study of UCO revealed the presence of components thatenhance the possibility of it being used as a microemulsion fuel. The presence of stearic acid, which acts as a natural surfactant, improves fuel stability for emulsion fuels.The presence of glyceridic signals in the emulsion systems confirms the absence of chemical reactions.The stable microemulsion system formed in the absence of surfactant can be attributed to the pre-Ouzo effect.Fuel property analysis confirms the possibility of utilizing UCO blended microemulsion fuel as an alternative for diesel fuel.
Key features of nano-emulsion formation by the phase inversion temperature method
Published in Journal of Dispersion Science and Technology, 2021
Jin Feng, Jordi Esquena, Carlos Rodriguez-Abreu, Conxita Solans
Depending on whether emulsification is triggered by a diffusion process[24,25] or by inversion of the spontaneous curvature of the surfactant during emulsification,[26,27] low-energy emulsification methods are classified as “self-emulsification” or “phase inversion,” respectively. For estimation of the spontaneous curvature, we refer to the seminal paper by Strey[28] and those that followed. In self-emulsification (also referred to as spontaneous-emulsification) energy is released by diluting with the continuous phase (typically water) the rest of components (typically a mixture of oil and a solvent miscible with both oil and water). During the dilution process leading to oil-in-water (O/W) nano-emulsions, diffusion of water-miscible components (solvent, surfactant, and/or cosurfactant) from the oil mixture into the aqueous phase is produced resulting in a metastable emulsion state.[24,25,29–32] The so-called Ouzo effect is self-emulsification produced in systems with no surfactant molecules. A drawback is that nanosized droplets can only be obtained at very high solvent/oil ratios (i.e., low oil volume fractions). In phase inversion methods, energy is released when phase transitions occur due to changes in the surfactant spontaneous curvature during emulsification which inverts from negative (W/O emulsions) to positive (O/W emulsions) or viceversa.[26,27] Inversion processes can be triggered by changing temperature (keeping composition constant)[26] or composition (at constant temperature),[27] the so-called PIT and phase inversion composition (PIC) methods, respectively.