Surface chemistry of surfactants

The adsorption of the anionic surfactant sodium dodecyl sulphate (SDS), probably the most frequently studied surfactant and often used as model substance at the air/water and at the decane /interface is given in Fig. 1.5. The surface and interfacial tension have been plotted as a function of SDS concentration in the aqueous phase. From the slope of the tangents to the curves in Fig. 1.5 the interfacial excess concentration (adsorption density) F at different interfacial tensions can be calculated directly using Gibbs fundamental adsorption isotherm (see section 2.4.1), 

The von Szyszkowski isotherm establishes the connection between the change in surface tension y and the surfactant bulk concentration. Stauff (1957) has evaluated the parameters of this semi-empirical adsorption isotherm and has shown that it is in agreement with interfacial thermodynamics. Frumkin s isotherm has often recently been used to describe the adsorption of different types of surfactants, for example by Lunkenheimer (1983), Miller (1986), Wiisteneck et al. (1993), and others. One of the main aims of this book is to show that in the many 

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Hsu, C. and Berger, P.D. "Surface Chemistry of Surfactants Used to Prevent Surface Coatings Defects," 1988 Symposium on Coatings Defects Federation of Soc. for Coatings Technol., Orlando, May 17-18. 

Surface Chemistry of Surfactants and Basic Adsorption Phenomena... 

The geometry and surface chemistry of the dendrimer assemblies can be varied through the addition of surfactants. These dendrimer/surfactant aggregates can be tuned to template the formation of the different phases of calcium carbonate [40]. In combination with hexadecyltrimethylammonium bromide (CTAB), small spherical aggregates were formed that induce the formation of vaterite. Over a period of five days, the vaterite was transformed into calcite. The use of the negatively charged surfactant, sodium dodecylsulfonate (SDS), result-... 

A surfactant was defined in Chapter 8 as an agent, soluble or dispersible in a liquid, which reduces the surface tension of the liquid [1]. It is helpful to visualise surfactant molecules as being composed of opposing solubility tendencies. Thus, those effective in aqueous media typically contain an oil-soluble hydrocarbon-based chain (the hydrophobe) and a smaller water-solubilising moiety which may or may not confer ionic character (the hydrophile). The limitations of space do not permit a comprehensive detailed treatment of the chemistry of surfactants. The emphasis is therefore on a broad-brush discussion of the principal types of surfactant encountered in textile preparation and coloration processes. Comprehensive accounts of the chemistry and properties of surfactants are available [2-13]. A useful and lucid account of the chemistry and technology of surfactant manufacturing processes is given by Davidsohn and Milwidsky [ 14] ... 

Magid, L. Solvent effects on amphiphilic aggregation. In Proceedings of the section on solution chemistry of surfactants held at the 52nd Colloid and Surface Science Sympos. Knoxville, TN 1978... 

The polarity and adsorption data discussed above reveal some interesting aspects of the surface chemistry of vinyl acrylic latex surfaces. It is quite likely that the polarity of the latex films, expecially of the two co-polymers, determined by contact angle measurements may not correspond exactly with their respective latex surfaces in the dispersed state due to reorientation of polymer chains during film formation. But the surfactant adsorption data shows clearly that the three latex surfaces in their dispersed state do exhibit varying polarity paralleling the trend found from contact angle measurements. The result also shows that the surface of the co-polymer latex surface is a mixture of vinyl acetate and acrylate units. This result is somewhat unexpected in a vinyl acrylic latex, prepared by a batch... 

Lucassen-Reynders, E.H. Surface Elasticity and Viscoaity in Compression/Dilation in Anionic Surfactants Physical Chemistry of Surfactant Action, Lucassen-Reynders, E.H. (Ed.), Dekker New York, 1981, pp.173-216. 

The surface properties of most minerals are generally influenced by the structure of the mineral-water interface and by surface species. The knowledge of these characteristics is required to understand the surface chemistry of solids. From the thermodynamic point of view, adsorption of surfactants on a mineral surface is very complicated. This is caused by the complex structure and ionic composition of the mineral-water interface formed during grinding the mineral in water. 

An elegant example of the analysis of colloid surfaces containing covalently attached hydrophilic species has been provided by Brindley et al who studied the surface chemistry of polystyrene colloids with surface grafted polyethylene glycol groups [39]. These colloids were prepared by surfactant-free copolymerization of styrene with PEG using potassium persulphate as an initiator. The XPS analysis of these microparticles is shown in Fig. 11. 

G. H. Harris, Reagents in MineralTechnology, Surfactant Science Series, Vol. 27, Marcel Dekker, Inc., New York, 1988, pp. 371—383. f. Leja, Surface Chemistry of Froth Flotation, Plenum Press, New York, 1982. 

E.H. Lucassen-Reynders, Surface Elasticity and Viscosity in Compression/ Dilation, in Anionic Surfactants Physical Chemistry of Surfactants, E.H. Lucassen-Reynders, Ed., Marcel Dekker (1981). (Principles are emphasized, additional reading to sec. 4.5.)... 

The adsorption of organic electrolytes is a more complicated process than that of nonelectrolytes because it is a complex interplay between electrostatic and nonelectrostatic interactions. In this section, I present results obtained with three representative types of organic electrolytes phenol and its derivatives, dyes, and surfactants. These observations demonstrate the importance of the surface chemistry of carbons on the adsorption processes. 

Monolayer techniques have been used with much success to study the interaction of proteins with surfactants (11, 12, 13), ions and lipids (14), and other proteins (15). This paper investigates, through well-established procedures, the surface chemistry of monolayers of a major component of heterogeneous wheat gluten protein, gliadin, and explores these interactions with various surface-active agents. 

The basic interfacial process in flotation is selective hydrophobization (or lepophiliza-tion) and hydrophilization of particulate matter. The role of the solution chemistry is very important in flotation as it is determined by the dissolution behavior of mineral particles in the aqueous solution (pulp) and subsequent dissociation, hydrolysis and precipitation of the soluble species the dissolution, association, dispersion and emulsion behavior of various flotation reagents in the pulp and interactions among reagents with both soluble and surface species of minerals. The efficiency of flotation and separation of mineral particles and consumption of reagents are thus controlled by the solution chemistry of the pulp. As other processes such as oil displacement are also governed by such interactions and in turn by the wettability of the solid surface, the study of solution chemistry of surfactant/mineral/additive systems become very important for the development of many technologies. 

Goodrich, F.C., "Rheological properties of fluid Interfaces" in Solution Chemistry of Surfactants, Mittal, K.L., (Ed.), Plenum Press, New York, Vol. 1, (1969)738 Goodrich, F.C., "Surface viscosity as a capillary excess transport property" in "The Modem Theory of Capillarity", Akademie-Verlag, Berlin, 1981 Grader, L., PhD Thesis, Leuna-Merseburg, 1985... 

In contrast to the large achievements in investigations of kinetic stability, modest attention has been paid to the fundamentals of thermodynamic stability in emulsions, especially regarding the surfactant adsorption layer s influence on the coalescence time. There are several investigations devoted to the surface chemistry of adsorption related to emulsification and demulsification. However, the link between the chemical nature of an adsorption layer, its structure, and the coalescence time is not yet quantified. 

The Influence of Soil Surface Chemistry on Surfactant Sorption and Wettabiiity Alterations... 

Depending on the particle-surfactant system, one or more of the above contributions can be responsible for adsorption. The dominating one would depend on the nature and concentration of the surfactant, the surface chemistry of the particle, and solution properties such as pH and ionic strength. Electrostatic and lateral interaction forces are usually the major factors determining the adsorption of surfactants on oxides and other non-metallic minerals. Chemical interactions become more dominant for surfactant adsorption on salt-type minerals, such as carbonates and sulfides. 

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