Emulsification, agitators

A (macro)emulsion is formed when two immiscible Hquids, usually water and a hydrophobic organic solvent, an oil, are mechanically agitated (5) so that one Hquid forms droplets in the other one. A microemulsion, on the other hand, forms spontaneously because of the self-association of added amphiphilic molecules. During the emulsification agitation both Hquids form droplets, and with no stabilization, two emulsion layers are formed, one with oil droplets in water (o /w) and one of water in oil (w/o). However, if not stabilized the droplets separate into two phases when the agitation ceases. If an emulsifier (a stabilizing compound) is added to the two immiscible Hquids, one of them becomes continuous and the other one remains in droplet form. 

It is quite clear, first of all, that since emulsions present a large interfacial area, any reduction in interfacial tension must reduce the driving force toward coalescence and should promote stability. We have here, then, a simple thermodynamic basis for the role of emulsifying agents. Harkins [17] mentions, as an example, the case of the system paraffin oil-water. With pure liquids, the inter-facial tension was 41 dyn/cm, and this was reduced to 31 dyn/cm on making the aqueous phase 0.00 IM in oleic acid, under which conditions a reasonably stable emulsion could be formed. On neutralization by 0.001 M sodium hydroxide, the interfacial tension fell to 7.2 dyn/cm, and if also made O.OOIM in sodium chloride, it became less than 0.01 dyn/cm. With olive oil in place of the paraffin oil, the final interfacial tension was 0.002 dyn/cm. These last systems emulsified spontaneously—that is, on combining the oil and water phases, no agitation was needed for emulsification to occur. 

Monomer emulsions ate prepared in separate stainless steel emulsification tanks that are usually equipped with a turbine agitator, manometer level gage, cooling cods, a sprayer inert gas, temperature recorder, mpture disk, flame arrester, and various nossles for charging the ingredients. Monomer emulsions are commonly fed continuously to the reactor throughout the polymerisation. 

Formation of Hposomal vesicles under controlled conditions of emulsification of Hpids with phosphoHpids has achieved prominence in the development of dmgs and cosmetics (42). Such vesicles are formed not only by phosphoHpids but also by certain nonionic emulsifying agents. Formation is further enhanced by use of specialized agitation equipment known as microfluidizers. The almost spontaneous formation of Hposomal vesicles arises from the self-assembly concepts of surfactant molecules (43). Vesicles of this type are unusual sustained-release disperse systems that have been widely promoted in the dmg and cosmetic industries. 

Proper emulsification is essential to the satisfactory performance of a carrier. A weU-formulated carrier readily disperses when poured into water, and forms a milky emulsion upon agitation or steaming. It should not cause oil separation upon heating or crystallization and sedimentation upon cooling. 

Excessive mixing Limit agitator power input and provide proper of reactants or impeller design impurities which, Return process to pilot or development to rede-promotes process to eliminate or minimize this emulsification. problem Poor phase separa- tion resulting in L it shaft speed problems in subse- Monitor shaft speed quent processing, phase separation steps or in down- stream equipment. I" " de-emulsifiers CCPS G-29 Lees 1996... 

The type of agitator and tank geometry required to achieve a particular process result, is determined from pilot plant experiments. The desired process result may be the dispersion or emulsification of immiscible liquids, the completion of a chemical reaction, the suspension of solids in a liquid or any one of a number of other processes [Holland and Chapman (1966)]. 

Immiscible liquids Emulsification Turboemulsifier (agitated vessel)... 

These equations, referring to completely unstirred systems, are not usually valid in practice complications such as spontaneous interfacial turbulence and spontaneous emulsification often arise during transfer, while, if external stirring or agitation is applied to decrease Ri and R2, the hydrodynamics become complicated and each system must be considered separately. The testing of the above equations will be discussed below, after a consideration of overall coefficients and of interfacial turbulence. 

Agitating the soil in an aqueous solution of nonionic biodegradable detergent to promote emulsification of the oil... 

Another problem encountered with jet fuels is due to contaminants and the consequent plugging of filter systems in the jet aircraft. Handling and distribution systems for jet fuels are usually underground. Fuel is pumped out of the tank by water displacement. Understandably, when fuel is moved, there is some agitation. If an additive is present, emulsification is possible. Also, there may be many contaminants such as rust, dirt, and water. The rate of settling, naturally is a function of viscosity and density. 

This phenomenon of self-emulsification was first observed by Johannes Gad in 1878 when he gently layered a solution of lauric acid on top of an aqueous alkaline solution, thereby making a soap in situ but also forming an emulsion without the aid of external agitation. A laboratory curiosity for the next 50 or so years, the principle became recognized as being valuable for the formulation of herbicides and insecticides such as DDT. The concentrate could be reconstituted with ditch water and sprayed without the need to carry water to the site. 

Emulsion Capacity is the property of the protein product solution or suspension to emulsify oil. The measurement is of the maximum amount of oil that the mixture will emulsify without losing its emulsion characteristics. The steps involved in this test are 1) Hydration - formation of the aqueous mixture. 2) Oil addition - with agitation the cause of emulsification. 3) Stress - a result of the heat generated during emulsification. 

Alkaline cleaners are available which allow the separation of excess oily soil from the cleaner. These formulations involve the use of surfactants that are good detergents but poor emulsifiers. Agitation of the bath during the work shift causes a temporary emulsification, which keeps the soil in suspension. After a prolonged period of inactivity (usually overnight), the oily soils float to the surface where they are skimmed off. This method is quite effective with mineral oil-type soils but is less so with fatty oils. 

In this work the potential of biphasic synthesis mixtures for the synthesis of microporous silicoalumino-phosphates is investigated. The influence of emulsification of the synthesis mixture, agitation and temperature on the crystallization is studied. The structural identity of MCM-1 and A1P0.-H3, which is an aluminum phosphate hydrate that crystallizes in absence of template, is demonstrated. Special attention is paid to the mechanism of Si substitution in MCM-1, to its catalytic activity and its intracrystalline void structure. 

As described later, liquid-liquid reactors are mechanically agitated in order to achieve a good dispersion and large interfacial area between two immiscible liquids. The increase in interfacial area due to stirring enhances the reaction rate (e.g., saponification, bead polymerization, etc.). It should be noted that the interfacial area is also increased by the addition of surfactants. This process is called emulsification and is governed by completely different principles than the ones described here. 

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