Emulsification efficiency

As mentioned, the intensity of the process, or the effectiveness in making small droplets, is often governed by the net power density e. The net energy consumption per unit volume of emulsion then is given by 

What measures can be taken to enhance efficiency if an emulsion of given properties has to be made These may include the following. 

Optimize efficiency of agitation by increasing and decreasing dissipation time. This often means increasing the ratio of the active volume (where e is quite high) to the inactive volume. 

Add more surfactant, thereby creating a smaller Yett and possibly diminishing recoalescence. This measure can be readily combined with the previous one. Of course, adding more surfactant does increase costs. 

If possible, dissolve the surfactant in the disperse rather than in the continuous phase. It often leads to smaller droplets see Section 2.4, Spontaneous Emulsification. 

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The emulsification efficiency can be measured in various ways. One is based on the ratio between the volume of emulsified dispersed phase, V, and the initial volume of the dispersed phase, Vq. 

The influence of the vessel size in the preparation of emulsions under ultrasonic energy in discrete systems has been established in terms of parameter R, which is the ratio of the height of the liquid-liquid mixture in the vessel to the diameter of the vessel. Two cylindrical vessels of different size (specifically with an R value of 1 and 2.5) were used under the same working conditions. Similar to the tip diameter, the differences in emulsification efficiency between the two vessels were small at a high (93 W) or very low (15 W) ultrasonic power. On the other hand, at 33 and 63 W, the efficiency was higher for the vessel with R= 1 viz. a cylindrical vessel) [56],... 

The emulsification efficiency can be increased by increasing surfactant concentration in the medium in fact, emulsion droplets find it difficult to disperse and tend to grow large at low concentrations of surfactant. Figure 6.12C shows the variation of droplet size (expressed as the Sauter diameter, 0/3 2) in a w/o water-in-kerosene emulsion at variable... 

Dispersibility tests Dye tests Liquefaction time Robustness to Dilution In vitro lipolysis studies Characterization of self-emulsification efficiency of liquid SNEDDS Characterization of self-emulsification efficiency of solid SNEDDS pellets Characterization of solid SNEDDS as time equired for melting under in vivo conditions Determine the capability of the formulation to withstand possibly infinite dilutions Estimation of lipolysis rate and amount of lipid digestion... 

While the required amount of energy is provided by the flow rate only, which should be about 5-15 m/s [61]. However, [32] demonstrates that the emulsification efficiency can be achieved by an increase (>30°) of the conical widening at the reactor s input zone. At the same time, the effective dispersing of flows, different in density and viscosity, requires a value at the reactor s input in the range of 0.065-0.080 m /s, as well as its stability along the axis of the device [32, 57]. 

The major disadvantage of using the HLB number as a guide to choosing a surfactant for a particular emulsification experiment is that it is not indicative of the emulsification efficiency or effectiveness of the surfactant. It does not predict what concentration of the surfactant would be necessary for emulsification, or... 

Enhanced emulsification efficiency along a B -> A path can be reached by dissolving the hydrophilic surfactant inside the original oil phase. As water is added the surtaciant transfers from oil to water as soon as the Huids are in contact. This transient phenomenon often triggers a spontaneous emulsification that results in extremely small oil droplets. This i.s, however, loo complex an occurrence to be properly interpreted with the formulation-composition map features. 

With respect to the emulsification properties of biosurfactants, one parameter that is often reported in the literature is the emulsification efficiency (E%). To measure this parameter, equal volumes of oil and water are vortexted for 1 minute and then left to settle for 24 hours (E24). After that time, the percentage of the total volume of the liquid occupied by the emulsion is reported (E24%) [35]. This emulsification index can be measured, in principle, against any oil but most of the studies use kerosene as the reference oil. In the work of Benincasa and Accorsini [32], the rhamnolipid produced from sunflower soapstock had an E24 index of 50 (or 50%) against kerosene. In the work of Mercadd et al. [35], who used wastewater from olive oil mills, they obtained E24 indices ranging from 15 to 75 with kerosene. 

One consequence of the Z dependence is that the higher energy density per volume may be used to advantage by emulsification of the dispersed phase into a reduced amount of the continuous phase, followed by dilution. A reduced amount of the continuous phase means an increased value of Z, because the energy input is dissipated into a smaller volume. An exception to this rule is found if the continuous phase contains soHd particles. In such a case forces acting through the Hquid medium are not efficient for obvious reasons, and mechanical means such as a roUer mill should be used. 

Dietary fats, libers, and other carotenoids have been reported to interfere with carotenoid bioaccessibility. It is clear that by their presence in the gut, lipids create an environment in favor of hydrophobic compounds such as carotenoids. When arriving in the small intestinal lumen, dietary fats stimulate bile flow from the gallbladder and therefore enhance the micelle formation, which in turn could facilitate the emulsification of carotenoids into lipid micelles. Without micelle formation, carotenoids are poorly absorbed a minimum of 3 g of fat in meal is necessary for an efficient absorption of carotenoids, except for lutein esters that require higher amounts of fat. ... 

Key mechanisms important for improved oil mobilization by microbial formulations have been identified, including wettability alteration, emulsification, oil solubilization, alteration in interfacial forces, lowering of mobility ratio, and permeability modification. Aggregation of the bacteria at the oil-water-rock interface may produce localized high concentrations of metabolic chemical products that result in oil mobilization. A decrease in relative permeability to water and an increase in relative permeability to oil was usually observed in microbial-flooded cores, causing an apparent curve shift toward a more water-wet condition. Cores preflushed with sodium bicarbonate showed increased oil-recovery efficiency [355]. 

Effect of pH. Interfacial tensions between heavy crude oils and alkaline solutions were measured at temperatures up to 180°C by Mehdizadeh and Handy T341. They observed that tensions increased with an increase in temperature. However, recovery efficiencies obtained at high temperatures were comparable to those obtained at lower temperatures, apparently because the ease of emulsification at high temperatures counteracted the increase in tens i on. 

For self-emulsification the molar mass of the EUP must be within a certain range. If the molar mass is too high, the solubility of the EUP is too low. If the molar mass is too low, the solubilizing efficiency is insufficient. With an EUP from maleic anhydride (MA) and hexanediol-1,6 (HD) and acid terminal groups, the optimal molar mass for the solubilization of a hydrophobic comonomer, such as styrene (S), was found to be between about 1700 and 2200 [116]. 

The solvent extraction of chlorinated pesticide residues from soil is often achieved by using mixtures of solvents such as hexane-isopropanol or hexane acetone, but can be unsatisfactory owing to the emulsification problems [2, 3] or, with hexane-isopropanol, poor recovery [2, 4], Acetone extraction of soil is efficient [4, 5] but problems can arise from large amounts of coextracted material unless an efficient clean-up technique [6] is used prior to analysis by gas chromatography. 

Partition Coefficients of nonvl-phenyl-poly-(ethoxy)-ethanol (NPE) Surfactants. The solubility of surfactants in water and hydrophobic solvents is well documented (11,12,22), but only a few attempts at measuring partition coefficients between immiscible liquids have been reported (2,4,9,10). Partition coefficients of surfactants are of theoretical interest because of their relation to observed surfactant properties such as emulsification, wetting and detergency. Partition coefficients (K ) may be also of considerable practical value for predicting surfactant recov and recycling in industrial processes. For example, in the cold water extraction of tar sand, an effective surfactant with a high Kp could be efficiently recycled in the process water and would not follow the bitumen into the upgrading stream. 

There exists, in the literature on high internal phase emulsions, a small number of publications on possible applications of HIPEs, involving a diverse range of topics. The production of petroleum gels as safety fuels is one such example [124,125] this was mentioned in the section on non-aqueous HIPEs. The main advantage over conventional fuels is the prevention of spillage, which reduces the risk of fire in an accident. Also, studies on the flash-point of emulsified fuels [127] showed a considerable increase, compared to the liquid state, for commercial multicomponent fuels. In addition, there may be an enhancement of the efficiency of combustion of the fuel on emulsification, as it is known that a small amount of water in fuel can improve its performance [19]. 

Pouton, C.W. (1985). Self-emulsifying drug delivery systems Assessment of the efficiency of emulsification. Int. J. Pharmaceutics, 27, 335-348. 

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