Surfactant adsorption behavior

Fig. XI-13. Adsorption isotherms for SNBS (sodium p-3-nonylbenzene sulfonate) (pH 4.1) and DPC (dodecyl pyridinium chloride) (pH 8.0) on mtile at approximately the same surface potential and NaCl concentration of O.OlAf showing the four regimes of surfactant adsorption behavior, from Ref. 175. [Reprinted with permission from Luuk K. Koopal, Ellen M. Lee, and Marcel R. Bohmer, J. Colloid Interface Science, 170, 85-97 (1995). Copyright Academic Press.]...

To obtain further information regarding the adsorption states at naturally hydrophobic mineral surfaces, the interfacial phenomena and surfactant adsorption behavior at graphite and sulfur surfaces were studied using MD simulation, with some interesting results to report. 

Polymer and surfactant do not interact with each other in solution. Nevertheless they adsorb both at the solid surface. As a consequence, both polymer and surfactant adsorption behavior is modified by the presence of the other. This kind of behavior can be treated in terms of adsorption competition between the polymer and the surfactant for the same solid surface. Very often, such situations are encountered for polymer and surfactant owning the same electrical charge and adsorbing onto an oppositely charged solid surface. 

The influence of the presence of alcohols on the CMC is also well known. In 1943 Miles and Shedlovsky [117] studied the effect of dodecanol on the surface tension of solutions of sodium dodecyl sulfate detecting a significant decrease of the surface tension and a displacement of the CMC toward lower surfactant concentrations. Schwuger studied the influence of different alcohols, such as hexanol, octanol, and decanol, on the surface tension of sodium hexa-decyl sulfate [118]. The effect of dodecyl alcohol on the surface tension, CMC, and adsorption behavior of sodium dodecyl sulfate was studied in detail by Batina et al. [119]. 

The adsorption behavior of homologous sodium alcohol sulfates at the interface can be characterized by the adsorption isotherms. However, the adsorption parameters of these isotherms are very sensitive to impurities present in the surfactant. Wiinstneck et al. [145] determined the equilibrium values of... 

The differences in time-dependent adsorption behavior between 99% PVAC at 25° and 50°C demonstrate the influence of intra- and intermolecular hydrogen bonding in the adsorption process. The limiting surface pressure of the hydrophobic water-soluble polymer appears to be 33 mN/m, approximately 7 mN/m below that of commonly used surfactants. The rate of attainment of equilibrium surface pressure values is faster if there is uniformity of the hydrophobic segments among the repeating units of the macromolecule. 

The presence of pre-adsorbed polyacrylic acid significantly reduces the adsorption of sodium dodecylsulfonate on hematite from dilute acidic solutions. Nonionic polyacrylamide was found to have a much lesser effect on the adsorption of sulfonate. The isotherm for sulfonate adsorption in absence of polymer on positively charged hematite exhibits the typical three regions characteristic of physical adsorption in aqueous surfactant systems. Adsorption behavior of the sulfonate and polymer is related to electrokinetic potentials in this system. Contact angle measurements on a hematite disk in sulfonate solutions revealed that pre-adsorption of polymer resulted in reduced surface hydrophobicity. 

The mechanism of interaction of amino acids at solid/ aqueous solution interfaces has been investigated through adsorption and electrokinetic measurements. Isotherms for the adsorption of glutamic acid, proline and lysine from aqueous solutions at the surface of rutile are quite different from those on hydroxyapatite. To delineate the role of the electrical double layer in adsorption behavior, electrophoretic mobilities were measured as a function of pH and amino acid concentrations. Mechanisms for interaction of these surfactants with rutile and hydroxyapatite are proposed, taking into consideration the structure of the amino acid ions, solution chemistry and the electrical aspects of adsorption. 

Equations 36-40 describe the entire adsorption behavior of 1 1 ionic surfactants in the absence of added salt or in the presence of salt with the... 

DobidS, B. Surfactant Adsorption on Minerals Related to Rotation. Vol. 56, pp. 91-147. Doughty, M. J., Diehn, B. Flavins as Photoreceptor Pigments for Behavioral Responses. Vol. 41, pp. 45-70. 

This overview will outline surfactant mixture properties and behavior in selected phenomena. Because of space limitations, not all of the many physical processes involving surfactant mixtures can be considered here, but some which are important and illustrative will be discussed these are micelle formation, monolayer formation, solubilization, surfactant precipitation, surfactant adsorption on solids, and cloud point Mechanisms of surfactant interaction will be as well as mathematical models which have been be useful in describing these systems,... 

This explanation for the entropy-dominated association of surfactant molecules is called the hydrophobic effect or, less precisely, hydrophobic bonding. Note that relatively little is said of any direct affinity between the associating species. It is more accurate to say that they are expelled from the water and —as far as the water is concerned —the effect is primarily entropic. The same hydrophobic effect is responsible for the adsorption behavior of amphi-pathic molecules and plays an important role in stabilizing a variety of other structures formed by surfactants in aqueous solutions. 

This paper describes a study of the dispersibility of Graphon (graphitized Spheron 6) in aqueous solutions of sodium dodecyl sulfate (SDS) an dodecyl trimethylammonium bromide (DTAB), and its relation to the adsorption behavior of the surfactants at the solid/liquid interface, with a view to determine the controlling process in the dispersibility of these systems. 

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. 

The second objective is to verify experimentally the predicted relationship between polymer polarity and surfactant adsorption by studying the adsorption of a non ionic surfactant that shows a saturation type isotherm behavior on vinyl acrylic latexes of varying polarity. 

It is well known (3,5,6) that sodium lauryl sulfate interacts with some polymers such as polyvinyl acetate causing solubilization of the insoluble polymer leading to an increase in viscosity. In Figure 3, viscosity of the homopolymer and 70/30 VA/BA at various NaLS/polymer ratio is shown. It is seen that the viscosity of the 2% latex dispersion increases with increase in NaLS/polymer ratio. Similar visoosity data for the 85/15 VA/BA was intermediate between the homopolymer and 70/30 VA/BA latexes. Surfactants that showed a normal saturation type adsorption behavior did not show any significant visoosity increase of the latex. 

Peker, S., S. Yapar, and N. Besiin. 1995. Adsorption behavior of surfactant on montmorillonite. Coll. Surf. 104 249-257. 

The added surfactant molecules intended for CMP slurry stabilization can adsorb not only onto the abrasive particle but also onto the surface of the wafer to be polished. Depending on the extent of such adsorption, the added surfactant may influence the CMP process in several ways such as change in friction behavior of the slurry, modification of removal rate and selectivity, alteration of defectivity level, and shift in post-CMP profile. In this section the impact of surfactant adsorption on the removal rate, selectivity, and post-CMP cleaning characteristics will be discussed. 

Phase Behavior and Surfactant Design. As described above, dispersion-based mobility control requires capillary snap-off to form the "correct" type of dispersion dispersion type depends on which fluid wets the porous medium and surfactant adsorption can change wettability. This section outlines some of the reasons why this chain of dependencies leads, in turn, to the need for detailed phase studies. The importance of phase diagrams for the development of surfactant-based mobility control is suggested by the complex phase behavior of systems that have been studied for high-capillary number EOR (78-82), and this importance is confirmed by high-pressure studies reported elsewhere in this book (Chapters 4 and 5). 

The other application of pore-level mechanisms exploits their dependence on dispersion type, wettability, capillary number, and capillary pressure to design surfactants that will optimize these parameters. Measurements of phase behavior, interfacial tensions, surfactant adsorption, wettability, and related parameters will be needed to fit the various requirements of different reservoirs, each of which has a unique combination of mineralogy, pore structure, temperature, pressure, oil and brine composition, etc. 

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