Emulsification conventional

By direct membrane emulsification (conventional membrane emulsification), the phase to be dispersed has to be pressed through a microporous membrane. Small droplets are formed and detached from the membrane by a flow of the continuous phase (Figure 13.5). For an appropriate droplet formation, the surface of the membrane has to be wetted by the continuous phase, for example a hydrophilic membrane has to be used to produce an o/w emulsion. 

T, Emulsification of silicone oil in water. Comparison between a micromixer and a conventional stirred tank, in Proceedings of the 4th International Conference on Microreaction Technology, IMRET 4, pp. 167-173 (5-9 March 2000), AIChE Topical Conf Proc., Atlanta, USA. 

Inverse emulsification A solution of the polymer within a volatile, water-immiscible organic solvent (or mixture of solvents) or a polymer melt is compounded with a long-chain fatty acid (e.g., oleic acid) using conventional rubbermixing equipment and mixed slowly with a dilute aqueous phase to give a W/O emulsion,... 

One of the most important advantages of the bio-based processes is operation under mild conditions however, this also poses a problem for its integration into conventional refining processes. Another issue is raised by the water solubility of the biocatalysts and the biocatalyst miscibility in oil. The development of new reactor designs, product or by-product recovery schemes and oil-water separation systems is, therefore, quite important in enabling commercialization. Emulsification is thus a necessary step in the process however, it should be noted that highly emulsified oil can pose significant downstream separation problems. 

The high content of water and emulsifier in this fuel creates some differences in handling and application compared to conventional diesel fuel. The surfactant quality of the emulsification additive in the fuel can remove existing deposits from the internal surfaces of fuel handling and storage systems. Problems with fuel discoloration and fuel filter plugging may follow. Compared with conventional diesel, fuel economy ratings per tank of fuel will drop because the overall carbon content per unit volume of fuel is lower. This is due to carbon displacement by water. 

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]. 

SPEs offer distinctive advantages over conventional liquid-liquid extractions. They are relatively fast, require small sample size, eliminate emulsification problems, provide the possibility of performing both cleanup and preconcentration of the extract in one analytical step, and offer high precision. Another great advantage of SPEs over liquid-liquid extractions is solvent savings. Unlike liquid-liquid extractions that often require hundreds of milliliters for single or multiple extractions, SPEs require only a few milliliters of solvents for analyte extraction and cleanup. 

The distinguishing feature of membrane emulsification technique is that droplet size is controlled primarily by the choice of the membrane, its microchannel structure and few process parameters, which can be used to tune droplets and emulsion properties. Comparing to the conventional emulsification processes, the membrane emulsification permits a better control of droplet-size distribution to be obtained, low energy, and materials consumption, modular and easy scale-up. Nevertheless, productivity (m3/day) is much lower, and therefore the challenge in the future is the development of new membranes and modules to keep the known advantages and maximize productivity. 

A peculiar advantage of membrane emulsification is that both droplet sizes and size distributions may be carefully and easily controlled by choosing suitable membranes and focusing on some fundamental process parameters reported below. Membrane emulsification is also an efficient process, since the energy-density requirement (energy input per cubic meter of emulsion produced, in the range of 104-106 J m-3) is low with respect to other conventional mechanical methods (106-108 J m-3), especially for emulsions with droplet diameters smaller than 1 (4m [1]. The lower energy density requirement also improves the quality and functionality... 

A few food products have been on the market using cross-flow membrane emulsification. The method can make emulsions that have small droplets with a narrow size distribution. Thus, it is possible to make sauces with lower oil content than with conventional emulsification techniques. The technique of cross-flow emulsification is clearly the best developed process for small-scale, high-value applications it is an attractive process. 

The casein retentate, when used as cheese milk, can almost be fully depleted of all whey proteins through a sufficient number of diafiltration volume turnovers. In contrast to conventional cheese technology, it is then possible to UHT treat the cheese milk in order to destruct spore formers. The whey proteins can be used as a WPG or WPI product or treated further in order to fractionate the whey proteins in their main components. Alternatively the whey proteins can particulated to form WPP see Section 19.5.1. Both approaches are options to build a platform for novel product matrices with specific properties such as gelling, foaming or emulsification. 

Another type of mechanical transducer which is frequently used for emulsification is the liquid whistle. Unlike the more conventional whistle, which operates on gas motion. 

Ultrasound-assisted emulsification in aqueous samples is the basis for the so-called liquid membrane process (LMP). This has been used mostly for the concentration and separation of metallic elements or other species such as weak acids and bases, hydrocarbons, gas mixtures and biologically important compounds such as amino acids [61-64]. LMP has aroused much interest as an alternative to conventional LLE. An LMP involves the previous preparation of the emulsion and its addition to the aqueous liquid sample. In this way, the continuous phase acts as a membrane between both the aqueous phases viz. those constituting the droplets and the sample). The separation principle is the diffusion of the target analytes from the sample to the droplets of the dispersed phase through the continuous phase. In comparison to conventional LLE, the emulsion-based method always affords easier, faster extraction and separation of the extract — which is sometimes mandatory in order to remove interferences from the organic solvents prior to detection. The formation and destruction of o/w or w/o emulsions by sonication have proved an effective method for extracting target species. 

Membrane emulsification is a relatively new technique with specific advantages (simplicity, potentially less energy demands, less surfactant, and narrow droplet-size distributions) compared to conventional emulsification techniques [102]. Depending on the membrane hydrophilicity/hydrophobicity and the composition of the two liquid phases, O/W, W/0, or MW emulsions may be produced. Most often used, O/W membrane emulsification consists of the pressurization of oil (dispersed phase) through membrane pores at high pressure (Figure 6.26). The oil jet flows formed in the circulating continuous phase are... 

Many examples are to be found in the chemical or biochemical literature e.g. ultrasonically induced emulsification/mixing has been utilized in the two-phase enzymatic synthesis of dipeptides [11]. For the dipeptide synthesis shown in reaction (1) the source of ultrasound was an ultrasonic bath (38 kHz). The importance of sonication in such a system is that it promotes biphasic reaction in solvent mixtures such as petroleum ether/water which are not effective under conventional conditions (Table 2). 

One of the earliest uses of power ultrasound in processing was in emulsification. If a bubble collapses near the phase boundary of two immiscible liquids, the resultant shock wave can provide a very efficient mixing of the layers. Stable emulsions generated with ultrasound have been used in the textile, cosmetic, pharmaceutical, and food industries. Such emulsions are often more stable than those produced conventionally and often require little, if any, surfactant. Emulsions with smaller droplet sizes within a narrow size distribution are obtained when compared to other methods. 

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