SEPARATION OF SURFACTANTS

Coinjection of a low-concentration surfactant and a biopolymer, followed by a polymer buffer for mobility control, leads to reduced chemical consumption and high oil recovery. There may be synergistic effects between the surfactant and the polymer in a dynamic flood situation. The chromatographic separation of surfactant and polymer is important to obtain good oil recovery and low surfactant retention [1721],... 

Many separation and detection methods applied in combination with liquid chromatography (LC) that are described in the literature for the determination of surfactants are not specific to the detection of these compounds at trace levels. Even ultraviolet (UV) spectra obtained from diode array detectors often give only limited information. Furthermore, non-reproducible retention behaviour as well as coelution interference effects are frequently observed during the separation of surfactant-containing extracts. This is recognised, however, only in those cases where specific detection methods such as mass spectrometry (MS) are applied. 

The greatest disadvantage of all detector systems such as, e.g. FID, UV, diode array detection (UV-DAD), FL, refractory index (RI), light scattering detector (LSD) or conductivity, applied in combination with GC, LC or CZE, is that they only provide an electric signal at the detector. The retention time alone of standard compounds, if available, is not sufficient for a reliable identification. LC separation of surfactant-containing extracts may often result in non-reproducible retention... 

An organic phase can be used several times provided the sample feed (fermentation broth) does contain cells or cell debris. Presence of such contaminants may render it necessary to regenerate the organic phase for its prolonged use. A literature survey suggests that the knowledge available on the recovery and reuse of surfactants is very little. However, the removal of surfactants from the stripping aqueous solution can be achieved by filtration and then can be recycled [10]. Use of ultrafiltration was also shown to be a successful technique for the separation of surfactants from reverse micellar solution [203]. 

Surfactant Activity in Micellar Systems. The activities or concentrations of individual surfactant monomers in equilibrium with mixed micelles are the most important quantities predicted by micellar thermodynamic models. These variables often dictate practical performance of surfactant solutions. The monomer concentrations in mixed micellar systems have been measured by ultraf i Itration (I.), dialysis (2), a combination of conductivity and specific ion electrode measurements (3), a method using surface tension of mixtures at and above the CMC <4), gel filtration (5), conductivity (6), specific ion electrode measurements (7), NMR <8), chromatograph c separation of surfactants with a hydrophilic substrate (9> and by application of the Bibbs-Duhem equation to CMC data (iO). Surfactant specific electrodes have been used to measure anionic surfactant activities in single surfactant systems (11.12) and might be useful in mixed systems. ... 

The alternative approach is to treat micellisation as a simple phase separation of surfactant in an associated form, with the unassociated surfactant concentration remaining practically constant above the... 

The role of foams and foam films depends significantly on the flotation type. From all methods only the foam adsorptive accumulation of surfactants and their complexes with ions, is based entirely on the regularities of the process of substance accumulation by adsorption in the stable foam. That is why further on the main target will be the analysis of the regularities of the adsorptive accumulation and separation of surfactants in the polyhedral foam. 

The process of foam separation of surfactants is used for solving various problems accumulation of surfactants in a foam that aims their extraction or the purification of a... 

Foam separation of surfactant components from mixtures... 

As we discussed in Section 7.4 on phase behavior, alcohol can increase the solubility of a surfactant. Other factors could be temperature, chromatographic separation of surfactant species, and so on. 

This is related to the formation of a great number of large colloid particles at such a high surfactant concentration. Since at 10% conversion the system viscosity is still low, the colloid particles coalesce and the system separates into two phases (polymer and surfactant). The separation of surfactant from the oligomeric solvent results in the decrease of the system s optical density. 

Upon achieving the limiting size of the colloid particles and with increasing polymerization of the oligomer, the concentration of particles per unit volume of the solvent increases, causing loss of stabihty and producing aggregation with formation of a separate phase. Separation of surfactant from the polymer results in the abrupt increase of its concentration in the siuface layer when the system becomes incompatible a decrease in its siuface tension is observed. 

Let us consider the features of the polymerization of systems that incorporate surfactant. Depending on the reaction time, the character of the alteration of the surface tension is similar for DEG—PEPA systems that contain OP-10 or L-19. For the explanation of this, refer to the information presented in Section 2.3. At the start of the reaction, when the concentration of L-19 that has reacted with DEG-1 is still low, L-19 behaves similarly to an IS substance, i.e., OP-10. In the course of system polymerization, the compatibihty of RS substances with the oligomer increases (see Table 2.5), which is why the decrease of the surface tension cannot be caused by the separation of surfactant from the system. 

Distillation is generally not applicable to separation of surfactants. The ionic surfactants have no appreciable volatility unless derivatized. The lower oligomers of the ethoxylated nonionics can sometimes be distilled, but the separation requires high temperature and low... 

TABLE 3 Cation Exchange Chromatographic Separation of Surfactants... 

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