Effect of surfactant type and

Effect of surfactant type and concentration An increase in surfactant concentration results in an increase in the number of micelles rather than any substantial change in size, and this enhances the capacity of the reverse micelle phase to solubilize proteins. Woll and Hatton [24] observed increasing protein solubilization in the reverse micelle phase with increasing surfactant concentration. In contrast, Jarudilokkul et al. [25] found that at low minimal concentrations (6-20 mmol dm AOT), reverse mieelles eould be highly seleetive in separating very similar proteins from... 

Emory, S.F. Koga, Y. Azuma, N. Matsumoto, K. The effects of surfactant types and latex-particle feed concentration on membrane retention. Ultrapure Water 1993, 10 (2), 41 4. 

Effect of Surfactant Type and Concentration. Surfactant concentration and type is of great importance for the stability of thin liquid films and for emulsion stability. Type and concentration of surfactants are responsible for the degree of lowering the interfacial tension and for the viscoelastic properties of droplet surface, as well as for the film thickness between two droplets. 

Figure 10. Effect of surfactant type and surfactant concentration on emulsion stability Span 20 o Span 80 V Span 85 breaking time 20 s.

In these studies, polymeric nanocapsules with encapsulated dsDNA (790 base pairs) were produced via anionic polymerization of n-butylcyanoacrylate (BCA) carried out at the interface of homogeneously distributed aqueous droplets in inverse miniemulsion which are in a second step then redispersed in an aqueous continuous phase. The obtained capsules were characterized in terms of size, size distribution, morphology, polymer molecular weight, and encapsulation efficiency of DNA. The effects of surfactant type and concentration, viscosity of the continuous phase, monomer amount, and water-to-oil ratio were investigated and results are discussed in this paper. 

Fig. 5. Effect of surfactant type on surface resistivity, (a) Concentration of surface-active compound in low density polyethylene (LDPE) requked to achieve 10 Q/sq surface resistivity and (b) effect on surface resistivity of an acrylic polymer. Concentration of surface-active compound is 0.3%.

The amount of water solubilized in a reverse micelle solution is commonly referred to as W, the molar ratio of water to surfactant, and this is also a good qualitative indicator of micelle size. This is an extremely important parameter since it will determine the number of surfactant molecules per micelle and is the main factor affecting micelle size. For an (AOT)/iso-octane/H20 system, the maximum Wq is around 60 [16], and above this value the transparent reverse micelle solution becomes a turbid emulsion, and phase separation may occur. The effect of salt type and concentration on water solubilization is important. Cations with a smaller hydration size, but the same ionic charge, result in less solubilization than cations with a large hydration size [17,18]. Micelle size depends on the salt type and concentration, solvent, surfactant type and concentration, and also temperature. 

The paddle mill was used to study the effect of surfactant type on a solvent-aqueous-surfactant extraction scheme for the recovery of bitumen from Athabasca tar sand. n the experiments of Figures 4,5 and 6, bitumen recovered from the surface phases was measured as a function of the mole fraction of ethylene oxide in the surfactant and as a function of the extraction step in which the surfactant was added. The results are reported as the % of the total bitumen present in the surface fraction. The amount of surfactant used was that required to give a final aqueous concentration of 0.02% (w/v), but in different sets of experiments the surfactant was added at various stages in the process. 

FIGURE 6.16 Effect of surfactant type on the microchip separation of 2 mg/L TNT, 1 mg/L TNB, and 2 mg/L tetryl. The separation buffer contained MeCN/MeOH (87.5/12.5 ([v/v])), 2.5 mM NaOH, and with (a) no surfactant, (b) 0.5 mM CTAB, (c) 1.0 mM SDS. Applied separation field strength, 506 V/cm, using a 1-s floating injection. Colorimetric detection was achieved using a green LED source (505 nm) [622]. Reprinted with permission from Elsevier Science. 

Both stirring and temperature elevation have been shown to accelerate demulsihcation [130,138,150]. Hsu and Li [130] report that insulation material having a dielectric constant >4 offered better demulsihcation performance. Goto et al. [140] report on the effect of surfactant type on demulsihcahon. 

Capillary electrokinetic chromatography (CEKC) with ESI-MS requires either the use of additives that do not significantly impact the ESI process or a method for their removal prior to the electrospray. Although this problem has not yet been completely solved, recent reports have suggested that considered choices of surfactant type and reduction of electro-osmotic flow (EOF) and surfactant in the capillary can decrease problems. Because most analytes that benefit from the CEKC mode of operation can be effectively addressed by the interface of other separations methods with MS, more emphasis has until now been placed upon interfacing with other CE modes. For small-molecule CE analysis, in which micellar and inclusion complex systems are commonly used, atmospheric pressure chemical ionization (APCI) may provide a useful alternative to ESI, as it is not as greatly affected by involatile salts and additives. 

Sharma, A., Goswami, A.N., Rawat, B.S. and Krishna, R. (1987). Effect of surfactant type on the selectivity for separation of 1-methyl naphthalene and dodecane using liquid membranes. J. Membr. Sci., 42, 19-30. 

FIG. 8.22 Effect of surfactant type on protease stability (AE, alcohol ethoxylate AE25-3S, alcohol ethoxy sulfate LAS, linear alkylbenzene aulfonate). (Reproduced from Kravetz, L. and Guin, K.F. J. Am. Oil Chem. Soc., 62, 943, 1985. With permission.)... 

Dynamic surface tension is an important property of a surfactant solution and a recent book [14] provides an excellent review of the area. However, the effects that surfactant type and structure, micelle formation, CMC, and equilibrium tension have on the decay of surface tension with time (y(t)) are still unclear. The Ward and Tordai equation [15] describes the diffusion-controlled... 

Effect of Surfactant Type, Concentration and Viscosity of the Continuous Phase... 

The material used for the electrode also had a strong influence on E° (Figure 7). For Mb in DDAB films, F° values ranged from -50 to +120 mV versus NHF at pH 5.5 in the order lTOapparent rate constant depended weakly on electrode material. Clearly, proteins in snrfactant films do not give the same F° -valnes as in solntion. The influence of surfactant type and electrode material suggests a possible electrical double-layer effect at the electrode-film interface on the potential felt by the protein. Surfactant-protein interactions may also be important. 

Thuwapanichayanan et al. (2012) determined the drying curves of banana foams produced with aid from one of three foaming agents, namely egg albumin (EA), soy protein isolate (SPI) and whey protein concentrate (WPG) (Fig. 6.19). The results of these studies showed a strong effect of surfactant type on drying rate due to the development of different foam structures, while the exponential decrease in moisture content with time proved that the drying process of banana foams was controlled by internal diffusion. 

Studies of flow-induced coalescence are possible with the methods described here. Effects of flow conditions and emulsion properties, such as shear rate, initial droplet size, viscosity and type of surfactant can be investigated in detail. Recently developed, fast (3-10 s) [82, 83] PFG NMR methods of measuring droplet size distributions have provided nearly real-time droplet distribution curves during evolving flows such as emulsification [83], Studies of other destabilization mechanisms in emulsions such as creaming and flocculation can also be performed. 

Oil/water interfacial tensions were measured for a number of heavy crude oils at temperatures up to 200°C using the spinning drop technique. The influences of spinning rate, surfactant type and concentration, NaCI and CaCI2 concentrations, and temperature were studied. The heavy oil type and pH (in the presence of surfactant) had little effect on interfacial tensions. Instead, interfacial tensions depended strongly on the surfactant type, temperature, and NaCI and CaCL concentrations. Low interfacial tensions (<0.1 mN/m) were difficult to achieve at elevated temperatures. 

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