Effects of surfactant concentration

Fig. 5. Effect of surfactant concentration on moisture content of <500 fim coal filter cake (51). Poiat A represents 2ero surfactant concentration Poiat B,...

In this section the laboratory measurements of CC -foam mobility are presented along with the description of the experimental procedure, the apparatus, and the evaluation of the mobility. The mobility results are shown in the order of the effects of surfactant concentration, CC -foam fraction, and rock permeability. The preparation of the surfactant solution is briefly mentioned in the Effect of Surfactant Concentrations section. A zwitteronic surfactant Varion CAS (ZS) from Sherex (23) and an anionic surfactant Enordet X2001 (AEGS) from Shell were used for this experimental study. 

The Effect of Surfactant Concentrations, The effect of surfactant concentrations on CC -foam mobility is plotted on a log-log scale in Figure 3. The presented data points are the average mobility values obtained from a superficial velocity range of 2-10 ft/day, with the CC -foam fraction was kept constant around 80%. With Berea sandstone, ZS and AEGS surfactants were used. The measured average permeability of the Berea sandstone with 1% brine was 305 md. With Baker dolomite, AEGS was used to make comparison with Berea sandstone. The permeability of the Baker dolomite was 6.09 md measured with 1% brine solution. 

E. K. Anderberg, M. Bisrat, C. Nystrom. Physicochemical aspects of drug release. VII. The effect of surfactant concentration and drug particle size on solubility and dissolution rate of felodipine, a sparingly soluble drug. Int. I. Pharm. 1988, 47, 67-77. 

Table 3 Effect of Surfactant Concentration on CL Intensity with 1.0 X 10"5 M Pyrogallol...

Anderberg, E.K., Bisrat, M., and Nystrom, C. (1988), Physicochemical Aspects of Drug Release. VII. The Effect of Surfactant Concentration and Drug Particle Size on Solubility and Dissolution Rate of Felodipine, a Sparingly Soluble Drug, Intemat. J. of Pharma., 47, 67-77. 

Figure 2. Effect of surfactant concentration in the aqueous phase (Cw) on the partition coefficient (Kp) of Makon-14...

Partition coefficients of surfactants have been reported to remain constant below the critical micelle concentration (CMC), and to increase with concentration above the CMC (2,9,10). The effect of surfactant concentration in the aqueous phase (C ) on K was investigated with Makon 14 (14 mol% ethylene oxide, NPEj ), the results are given in Fig. 2. These data indicate a CMC of about O.lg/1, or 12 piM, in close agreement with the value obtained by surface tension measurements (our data and ref. 22). In subsequent determinations of Kp, C was just below the CMC to minimize the effects of micellization (15,23). 

Fig. 10 Effect of surfactant concentration on the optimum formulation (minimum tension position) for anionic mixtures (/e/t), pure anionic surfactant center) and ethoxylated nonionic mixtures (right)...

And rez JM, Bracho CL, Sereno S, Salager JL (1993) Effect of surfactant concentration on the properties of anionic-nonionic mixed surfactant-oU-brine systems. Colloid Surface A 76 249-256... 

The effect of surfactant concentration on critical osmotic pressure was also studied [97], Below a critical surfactant concentration, emulsions are always unstable due to incomplete coverage of the oil-water interfaces. Above this, Jt increases with increasing surfactant concentration until the critical micelle concentration (CMC) is reached, above which it remains more or less constant. 

In conclusion to this Section it is worth noting that in order to understand and detect the CBF/NBF transition, the h(Cel) at pa = const and n(/i) dependences are of equal importance, since they allow to establish the origin of the Fima barrier, the effect of surfactant concentration, Ceixr, pH, etc. 

The foam behaviour at low surfactant concentrations is the same as the described above. However, the formation of polyhedral foam at the upper parts of the foam column occurs at much lower surfactant concentrations. It should be noted that these concentrations are considerably lower than those at which form CBF and NBF. This is related to the effect of surfactant concentration in the foam and depends mainly on the surface activity of the substances and on the foam film thickness [53,54,121]. The higher surface activity of... 

FIGURE 14.13. Effect of surfactant concentration (2CI6QA) on the degree of extraction of DNA from the aqueous phase into the organic phase. The extraction was performed under the following conditions 10 mM TWs-HCl buffer, pH 8, DNA 50 pg/ml, salt-ftee and 2-ethyIhexylalcohol 3.8% (v/v) [22]. 

Figure 4. Effect of surfactant concentration with varying surfactant ratio on size of micelles and on polymerization rate...

The effect of surfactant concentration upon the solubility of cobalt(III) acetylacetonate in buffered aqueous phases at 50 C was also investigated spectroscopically. Saturated solutions were prepared by shaking excess finely-powdered cobalt(III) acetylacetonate with solutions of sodium dodecyl sulphate for approximately one hour at 50 C. It appeared that one hour was sufficient time for the attainment of equilibrium. 

Effect of Surfactant Concentrations. The effect of the surfactant concentration on foam mobility has been studied extensively. The surfactant under investigation for this effect was Varion CAS, a zwitterionic surfactant from Sherex. The rock under study was Berea sandstone which has a permeability of 308 9 md measured by using 1% brine solution. The permeability using N2 gas at atmospheric pressure was 1000 6.2 md. 

Figure 3. Effect of surfactant concentration on foam mobility.

Effect of Surfactant Concentration Emulsion stabdity generally increases with increasing surfactant concentration [92,93]. As discussed in Section 25.4.2.3, an increase in surfactant concentration leads to the lowering of leakage due to an increase in the mechanical resistance of the membrane. An increase in this parameter also increases the membrane phase viscosity as well as its resistance to mass transfer including water mass transfer, thus reducing osmosis [89,94]. 

Figure 9 shows the effect of surfactant concentration on the volume of the middle phase microemulsion. It is interesting that the plot goes through the origin indicating that even at very low surfactant concentrations, a microscopic amount of the midddle phase microemulsion must exist at the interface between oil and brine. 

Figure 9. Effect of surfactant concentration on the volume of middle phase microemulsion. Key o, 1.5% isobutanol , 3% isobutanol.

Apart from the fact that the use of the HLB system is limited as it is based on the observation of creaming or separation of the emulsions, as an index of instability the HLB system also neglects the effects of surfactant concentration on stability (26) and of course it is irrelevant to the particular problems with multiple emulsion systems. Nevertheless, it provides a useful approach to the choice of optimal surfactant system. In general, in a w/o/w emulsion, the optimal HLB value of the primary surfactant will be in the range 2-7 and in the range 6-16 for the secondary surfactant. Equilibration of the systems after mixing will undoubtedly result in the transfer of surfactant between the aqueous and nonaqueous components. Saturation of the phases with the two surfactants used should prevent instability during this equilibration. 

Figure 12. Effect of surfactant concentration on bulk phase viscos-ity 0 ECA 4360,0 Span 20, A Span 80, o Span 85.

Phase inversion is a commonly observed phenomenon in which the continuous phase abruptly becomes the dispersed phase and vice versa (see Pacek et al. and Pacek, Nienow, and Moore Systematic studies on the effect of surfactant concentration and mixing on phase inversion and emulsion drop size have been carried out by Brooks and Richmond. Fig. 5 shows schematically the steps occurring during phase inversion. Although conflicting information exists on the subject, the following conclusions can be made ... 

FIGURE 6.10 Effect of surfactant concentration on elastic modulus and relaxation time. Source Data from Kang (2001). 

FIGURE 8.4 Effect of surfactant concentration on optimum salinity for 1 wt.% alkaline chemicals, brine, n-tetradecane, and surfactant Exxon 914-22. Source Martin and Oxley (1985). 

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