Surfactant adsorption classification

Cetyltrimethylammonium bromide CH3(CH2)i5N(CH 3)381 is a typical cationic surfactant. Dissociation of this compound results in amphiphilic cations and small hydrophilic anions. This classification of surfactants is similar to the classification of strongly interacting compounds (other than surfactants) in Sections II and III into cations (Section II A), anions (Section II B) and electroneutral and zwitterionic organic compounds (Section III). The adsorption of anionic surfactants is indeed enhanced, when the adsorbent carries high positive surface charge (at low pH for materials hsted in Tables 3.1, and 3.3-3.5), and adsorption of cationic surfactants is more pronounced at high pH, and the adsoiption of nonionic surfactants is often rather insensitive to the pH. However, the mechanisms of surfactant adsorption, and experimentally observed adsorption isotherms of surfactants are very different from the compounds discussed in Sections II and III. 

Brunauer classification, 1 591 and column performance, 1 604—606 gas adsorption, 1 622-623, 626-629 of nonionic surfactants, 24 142—143 predicting, 24 139-140 Adsorption kinetics... 

The cmc is indicated by an arrow. The three nonpolar phases, SAS, MOS and ODS Hypersil , show a Langmuir-like adsorption isotherm with a concave shape or L type in the Giles classification [12]. The polar CPS phase shows a convex shape or S type cooperative adsorption. The amount of adsorbed surfactant increases in the order bare silica < CPS < SAS < MOS < ODS. This is exactly the decreasing order of the stationary phase polarity. No adsorption of SDS on the bare silica was observed in this low concentration range [11]. Above 0.004 M, the SDS adsorption on SAS Hypersil passes the one on MOS Hypersil . Hydrophobic interactions are mainly responsible for SDS adsorption in sub micellar solutions. 

In this overview, the first section will on general classification of polymeric surfactants. This is followed by a section on preparation of polymeric snrfactants, with particular reference to sugar-based molecules. This is followed by a discussion of their solntion properties. The next section will be devoted to the adsorption of polymeric snrfactants at the solid/liquid (S/L) interface, whereby a summary will be given to some of the theoretical treatments and the methods that... 

Some classification of parameters in their connection with physical or mechanical processes is to be done. The main parameter connecting hydrodynamic and diffusion parts of the film flow problem with surfactant is Marangoni number Ma. The both variants of positive (Ma > 0) and negative (Ma < 0) solutal systems are considered. The main hydrodynamic parameters are Re, 7 or equivalently S. 7. This two values determine the mean film thickness i/, mean velocity and flow rate as well as parameter k. The diffusion parameters Pe,co determine the local thickness of diffusion boundary layer h and smallness parameter e. Two values T, Di characterize the masstransfer of surfactant by the adsorption-desorption and the intensity of dissipation by the surface diffusion. Besides the limiting case of fast desorption (T = 0) the more general case (T 1) are considered. Intensity of the surfactant evaporation by parameter Bi is determined. The remaining parameter G gives an indication to the typical value of surface excess concentration A in comparison with c. ... 

In this section we describe the general classification of dispersing agents. The adsorption of surfactants and polymers at the solid/liquid interface was treated in Chapter 5. The various classes can be summarised as follows. 

The adsorption phenomena discussed in the previous section utilized amphiphilic molecules of organic surfactants (predominantly synthetic ones). Here, it would be worthwhile to provide a brief description and classification of the most common types of organic surfactants [11-24],... 

This chapter will start with a short account of the general classification and description of polymeric surfactants. This is followed by a summary on then-solutions properties. The adsorption and conformation of polymeric surfactants at the solid-liquid interface will be discussed at a fundamental level and some experimental results will be presented to illustrate the prediction of the theories. The interaction energies between particles or droplets containing adsorbed polymeric surfactants will be briefly described. The final section will give some applications of polymeric surfactants in suspensions, emulsions, and multiple emulsions. 

All of the above-mentioned charging mechanisms are involved in the Sposito s concept except the specific (item 5 in Everett s classification) or preferential (item 3 in Stumm s list) adsorption of, for example, surfactant ions. The question is whether this kind of preferential adsorption is involved in surface charging at all. This case coincides with the most serious problem of aqueous interfaces (i.e., which part of the interface belongs to the sohd phase ). Can we consider an adsorbed layer bonded via hydrophobic interaction, even it is enough sfrong, as an inherent part... 

The adsorption of snrfactants at liquid interfaces and their applications were described in many pnbhcations. Also books have been dedicated to this subject. For example in [1] not only the general classification of snrfactants and the synthesis and application of the main types of surfactants were discnssed but also the adsorption characteristics for a large number of homologous series of surfactants were snmmarized. hi various technologies the action of snrfactants is essential, snch as in the formation for foams and emulsions [2]. 

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