Anionic surfactants adsorption behavior

Recent investigations have shown that the behavior and interactions of surfactants in a polyvinyl acetate latex are quite different and complex compared to that in a polystyrene latex (1, 2). Surfactant adsorption at the fairly polar vinyl acetate latex surface is generally weak (3,4) and at times shows a complex adsorption isotherm (2). Earlier work (5,6) has also shown that anionic surfactants adsorb on polyvinyl acetate, then slowly penetrate into the particle leading to the formation of a poly-electroyte type solubilized polymer-surfactant complex. Such a solubilization process is generally accompanied by an increase in viscosity. The first objective of this work is to better under-stand the effects of type and structure of surfactants on the solubilization phenomena in vinyl acetate and vinyl acetate-butyl acrylate copolymer latexes. 

Dependence of Adsorption, on Rock Type. Table I shows that gas injection EOR projects are being conducted in sandstone and carbonate pools. Hydrocarbon- and C02-misdble projects are run largely in carbonate reservoirs. With the exception of several studies that report adsorption levels of EOR surfactants on carbonates (4,11,12, 24, 33, 62—64, 86), the petroleum literature has dealt almost exclusively with anionic, and sometimes nonionic, surfactant adsorption on sandstones, because most studies have been carried out with surfactants used in low-tension flooding. These surfactants are not considered suitable for application in carbonate reservoirs because of their low salinity and hardness tolerance. Foam-forming surfactants suitable for high-salinity environments include amphoteric surfactants (2). The adsorption behavior of this surfactant type has also rarely been studied (10—12, 87, 88). 

The second example involves a mixture of two different types of commercial foam-forming surfactants anionic and amphoteric (7). Unlike the mixture of the previous example, an anionic—amphoteric surfactant mixture probably does not follow ideal mixed micelle behavior (138). The results of three core-floods, performed separately with each surfactant and with a mixture of the two surfactants, are summarized as follows. The anionic surfactant adsorbs negligibly when used either by itself or when mixed with the betaine (at least at the low salinity used in these particular core-floods). Betaine adsorption is lowered by about an order of magnitude by mixing it with the anionic surfactant, from 1.7 down to 0.2 mg/g. 

Such a study has been performed for fluorocarbon and hydrocarbon anionic surfactants [48]. It has been found that the fluorocarbon surfactant ions are more rapidly adsorbed than the hydrocarbon surfactant ions. The two surfactants, which exhibit an antipathy manifested by micellar demixing, compete for surface sites and their total adsorption is reduced when both are present. Furthermore, the variations of potentials of the bubbles depending on compositions and concentrations of mixtures of the two surfactants in the solutions of which they are immersed are found to be closely correlated with the micellar phase diagram of these surfactants. These behaviors would deserve to be strengthened by measurements on other surfactant mixtures. 

Adsorption of anionic surfactant monomers on the surface of a Cl 8 stationary phase also causes protonated organic bases to be retained a longer period of time than the neutral free-base forms, because of electrostatic attraction. Consequently, the elution behavior of protonated bases will mimic that of acids on C18 columns (Fig. 5.12), in contrast to the behavior observed on cyano columns. Figures 5.10 and 5.12 are mirror images of each other. 

Anionic Surfactants onto Kaolinite and lUite. In the investigation of the adsorption of sodium dodecylbenzenesulfonate (SDBS) and sodium dodecyl sulfate (SDS) onto asphalt covered kaolinite and illite surfaces, Siffert et al. [5S] observed Langmuir type I isotherms for SDS adsorption onto Na kaolinite and Na illite while the SDBS exhibited a maximum in adsorption with a decrease beginning near the CMC. Adsorption maxima were observed near the CMC for both surfactants in the Ca kaolinite and Ca illite systems. The adsorption behavior was explained as precipitation of the calcium salt of the surfactants (an idea supported by other studies), and the interaction of the aromatic ring in SDBS with the asphalt. This interaction favors desorption of the asphalt rather than adsorption of the SDBS. The amount of asphalt desorbed by SDBS was twice that desorbed by SDS. Other explanations for adsorption maxima include mixed micelle formation [55] and electrostatic repulsion of micelles from the bdayer covered surface [59]. 

Anionic Surfactant Blend and Amphoteric Surfactants onto Berea Sandstone, Indiana Limestone, Baker Dolomite, and Quartz. The first study to be presented examined the adsorption behavior of two amphoteric surfactants, a betaine (Empigen BT) and a sulfobetaine (Varion CAS) and a 50 50 blend of a Cio diphenyl ether disulfonate (DOWFAX 3B2), and a Ci4 i6 ot-olefm sulfonate [11]. The anionic surfactant blend was designated as DOW XS84321.05. The Cio diphenyl ether disulfonate surfactant is one isomer in a suite of surfactants which differ in their degree of alkylation and sulfonation and in their chain lengths. This suite consists of monoalkyl disulfonates (MADS), dialkyl disulfonates (DADS), monoalkyl monosulfonates (MAMS), and... 

Reference has already been made to the unusual behavior, e.g., lowering of surface tension (57,58,75), development of surface viscosity (74), and so forth, observed in mixed solutions of polycations and anionic surfactants. Buckingham et al. (75) arrived at the following form of the Gibbs adsorption equation for their system (poly-L-lysine/SDS) ... 

The adsorption mechanism of PEO on silica is well established in literature and seems to proceed by hydrogen-bonding between the ether oxygen of the polymer and the silanol groups of the silica surface. Maltesh and Somasundaran showed that the anionic surfactant which did not adsorb on silica by itself does so to a considerable extent in the presence of preadsorbed PEO. Figure 8 illustrates their results, comparing the SDS adsorption behavior on naked silica (no adsorption) and that on PEO preadsorbed silica. 

The enhancement of the PVP adsorbed amount at the alumina-water interface, due to its interaction with an anionic surfactant, depends on the nature of the surfactant, as has been pointed out by Esumi et al. [50]. They studied the adsorption behavior on alumina of a system composed of PVP and a double-chained anionic surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (Aerosol OT). In an aqueous solution. Aerosol OT interacts with PVP as shown by surface-tension measmements which evidence the two typical Q and Ca concentrations [18] (Fig. 13). Ci at 2 mmol/L is the same as for the PVP-SDS system or the PVP-LiDS pair. Ca of the SDS-PVP system is approximately two times that of the Aerosol OT-PVP pair (i.e., around 2.3 mmol/L and 1.3 mmol/L, respectively). 

Yardim Y, Levent A, Keskin E et al (2011) Voltammetric behavior of benzo(a)pyrene at boron-doped diamond electrode a study of its determination by adsorptive transfer stripping voltammetry based on the enhancement effect of anionic surfactant, sodium dodecylsulfate. Talanta 85 441 148... 

There has been a recent revival of interest in zwitterionic surfactants (L 4) because of certain useful properties shown by these molecules, including 1) mild behavior on the skin, 2) compatability with both anionics and cationics, 3) adsorption onto skin and hair, and 4) lime soap dispersing ability. Although this type of surfactant has been produced and used industrially for the last few decades, there have been few studies of the properties of well purified surfactants of this type (5-11) and almost all of these have been concerned with the micellar properties of these compounds rather than with their behavior at interfaces. 

Micellar mobile phases of anionic, cationic, nonionic and zwitterionic surfactants are used in conjunction with different bonded stationary phases (including C8, Cl8 and cyano). Considerably less surfactant (usually <0.2 M) is used compared to the organic modifier content in an analogous traditional separation. A variation in the concentration of surfactant is translated into an increase in the concentration of micelles in the solution, whereas the number of monomers of surfactant remain constant. As a consequence, the characteristics of the stationary phase modified by the adsorption of surfactant are very stable, and usually, a regular retention behavior is observed as a function of the concentration of surfactant. 

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