De-emulsification

Performance can be illustrated for example by the time necessary for deaeration or de-emulsification of oils, anti-rust properties, copper strip corrosion test, the flash point in closed or open cup, the cloud and pour points, the foaming characteristics, etc. 

De-emulsification, ie, the breaking of foams or emulsions, is an important process, with the oU iadustry being a common one ia which the process is oftea critical. Chemical and particulate agents that displace the surfactant and permit an unstabilized iaterface to form are used for this purpose. 

Due to their distinctive physico-chemical properties, non-ionic surfactants are applied in the fields of industry, processing technology and science, wherever their interfacial effects of detergency, (de)foaming, (de)emulsification, dispersion or solubilisation can enhance product or process performance. The characteristics of non-ionic surfactants that make them beneficial for detergents include their relatively low ionic sensitivity and their sorptive behaviour [17]. 

Dual-phase extraction cannot remediate heavy chlorinated compounds, pesticides, or heavy hydrocarbons including polychlorinated biphenyls (RGBs), dioxin, fuel oil No. 6, or metals (with the possible exception of mercury). High-velocity pump systems (such as liquid ring vacuum pumps) tend to form emulsions, especially when diesel fuel is part of the recovered fluids. The problem of emulsion can be solved with prepump separation or a de-emulsification unit. 

Pont, E. G. 1955. A de-emulsification technique for use in the peroxide test on the fat of milk, cream, concentrated and dried milks. Aust. J. Dairy TechnoL 10, 72-74. 

For breaking W/O emulsion in wastewater treatment, electrostatic deemulsification techniques are generally used [11,14, 66-69]. Other methods of de-emulsification have been tried to include heat treatment, phase dilution, and high shear [70-72]. 

De-emulsiftcation one of the stumbhng blocks in the construction of a continuous liquid membrane process plant is de-emulsification and recovery of the solvent. De-emulsification involves coalescence of dispersed droplets into larger droplets with subsequent phase separation by gravity. The most popular method to augment this process is by apphcation of an electric field. This indicates that hquid membrane plants will be energy intensive. 

The methods of emulsion breaking (de-emulsification) are of importance in various areas of industry [39,61], especially in oil recovery in crude petroleum the content of highly saline water may be as high as 50 - 60%. Oil-soluble surfactants present in petroleum (asphaltenes, porphyrines, etc) and those introduced during tertiary recovery form highly developed adsorption layers at the water surface, and thus create structural-mechanical... 

De-emulsification is important, for example in the oil industry. Agents for this purpose have to be capable of displacing the stabilising surfactant, leaving a non-stabilising interface. The... 

The oil extracted from a well usually contains water dispersed as a fine emulsion. The de-emulsification of the oil is an important part of the overall processing, and improved and more economical methods of achieving this depend on the application of colloid techniques. 

Further liberation of free fat may occur under adverse storage conditions. If powder absorbs water it becomes clammy and lactose crystallizes, resulting in the expulsion of other milk components from the lactose crystals into the spaces between the crystals. De-emulsification of the fat may occur due to the mechanical action of sharp edges of lactose crystals on the fat globule membrane. If the fat is liquid at the time of membrane rupture, or if it becomes liquid during storage, it will adsorb on to the powder particles, forming a water-repellant film around the particles. 

In a standard ice cream formulation, sufficient partial coalescence occurs to enable a stable air cell structure to be maintained at overruns up to about 120%. It can be difficult to obtain overruns of more than about 60% in products where fat and protein are not present, or only present in small quantities, such as sorbets. Similarly it is difficult to obtain high overruns if there is insufficient shear (for example because of a very short residence time) to produce partially coalesced fat. Extra shear, and hence increased de-emulsification, can be produced either by increasing the dasher speed or by using a closed dasher. 

Destabilized (de-emulsif ed) fat Fat that has undergone partial (or total) coalescence so that it is no longer in the form of a fine emulsion. 

In earlier days, the method used to destabilize a crude oil/water emulsion was gravity-heating sedimentation. Nowadays, however, chemical de-emulsification and improved electromagnetic and gravitational techniques are the main methods used to break down an emulsion. 

Ag-poly(butyl acrylate-co-styrene) nanocomposites were prepared by Yin et al. [410] where the silver nanoparticles were obtained from a microemulsion. An aqueous solution of AgN03 was added to a mixture of toluene, butylacrylate, styrene, sodium dodecyl sulfate and 2-hydroxy-a-methacrylate (HEMA). A transparent microemulsion formed after addition of Span 80 under stirring. This product was bubbled with N2 and irradiated with to y-ray source for 6h (the irradiation helped both polymerization of monomers and reduction of metal ions). Silver particles, collected after de-emulsification by acetone and water, had an average size of about 8.5 nm. 

In this chaptCT we focus our attention on key optical methods and nuclear magnetic resonance (NMR), which have been indispensable for quantitative descriptions of size and structure, and diffusivity, where size and structure play an important role. Whereas in the previous chapters we have tended to focus on the overall dynamics, we concentrate here at the smallest scale needed to understand what the fundammtal building blocks are in those systems. With the exception of NMR, the other methods are restricted to transparent systems. This can sometimes be a drawback, as in the study of water-in-crude oil emulsions, which are black in color. These are very important systems industrially and require de-emulsification. NMR techniques for measurement of drop size distributions in such emulsions, while beyond the scope of this chapter, have been reviewed by Pena and Hirasaki (2003). 

Core-sheath nanofibers of PEG-PLA and PEG can be prepared by electrospinning a water-in-oil emulsion in which the aqueous phase consists of a PEO solution in water and the oily phase is a chloroform solution of an amphiphilic PEG-PLLA diblock copolymer. The fibers obtained are composed of a PEO core and a PEG-PLA sheath with a sharp boundary in between. By adjusting the emulsion composition and the emulsification parameters the overall fiber size and the relative diameters of the core and the sheath can be changed. As shown in Fig. 5.15, a mechanism is proposed to explain the process of transformation fi-om the emulsion to the core-sheath fibers, i.e., the stretching and evaporation induced de-emulsification. In principle, this process can be applied to other systems to... 

Due to their high efficiency, ELMs would appear to be attractive alternatives to SLMs. However ELM systems often suffer from problems of low solubility and difficulties with de-emulsification. To overcome these problems, a new liquid membrane process, the emulsion free liquid membrane (EI M), was developed by Kumar ef al. (60). Application of this novel technique to hydrometallurgical processes is quite promising (67). Recent studies of separating heavy metals, such as Cr(VI) and Cu(II) from electroplating effluents, with an EFLM system indicate that the technique is very efficient and superior to other types of LMs. 

Although very rapid separations can be accomplished with ELM systems, the process is rather complicated due to the requirement of de-emulsification to recover the encapsulated droplets. Poor stability of the emulsions is another drawback. 

Studies of W/O emulsions and thin aqueous surfactant films between oil phases using Span 80 and other low HLB surfactants by Sonntag and Klare [119] have drawn attention to the importance of the stability of the thin film between the water droplets when flocculation occurs. Addition of electrolyte causes dehydration of the surfactant molecules and promotes de-emulsification. As with O/W emulsions, addition of electrolyte causes a shift in the HLB of the surfactant molecules. Increase in temperature results in an increased rate of flocculation because of surfactant desorption and an increase in the rate of coalescence. Using water droplets in octane the temperature for coalescence increased with Span 80 concentration from 42°C at 0.1 gl" to 68°C at 1 gl and > 75 C at 5gl" The equilibrium non-aqueous black films which form between the water droplets are unaffected by temperature but their thickness is controlled by the nature of the oil phase. Span 80 in octane forms a film 3.9 nm thick, while in xylene the black film has a thickness of 28 nm [119]. Sonntag and Netzel have carried out similar measurements on this film relevant to O/W stability [120]. Because of the complexities of the real emulsion system such studies, discussed in some more detail in [4], have many uses in allowing the experimenter to isolate some of the variables in the system. The reader is referred to the literature on these films (see [121]) for further details and to Sonntag s paper in particular for information concerning non-ionic surfactant behaviour in aqueous and non-aqueous films (see [122-124]). 

Uses Polyol for aq. adhesives, deck and sports coatings, cast-elastomers, and crude oil de-emulsification... 

Uses Used in caulks, sealants, deck and sports coatings, deck and sports flooring. Inks, lubrication, metalworking, antistatic agents, crude oil de-emulsification in adhesives for food pkg. food-pkg. adhesives, paper/paperboard, cellophane ... 

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