Anionic surfactants, description

In this section the laboratory measurements of CC -foam mobility are presented along with the description of the experimental procedure, the apparatus, and the evaluation of the mobility. The mobility results are shown in the order of the effects of surfactant concentration, CC -foam fraction, and rock permeability. The preparation of the surfactant solution is briefly mentioned in the Effect of Surfactant Concentrations section. A zwitteronic surfactant Varion CAS (ZS) from Sherex (23) and an anionic surfactant Enordet X2001 (AEGS) from Shell were used for this experimental study. 

Based on their data for sorption onto a lake sediment, Kiewiet et al. (1996) derived an equation predicting sorption coefficients of CnEOms as a functions of alkyl chain length and the number of oxyethylene units. Di Toro et al. (1990) proposed a model for description of sorption of anionic surfactants which includes sorbent properties (organic carbon content, cation exchange capacity, and particle concentration) and the CMC as a function of the solution properties (ionic strength, temperature). The CMC is used as a relative hydrophobicity parameter. Since the model takes the contribution of electrostatic as well as hydrophobic forces explicitly into account, it is an example of an attempt to model surfactant behavior on the basis of the underlying mechanisms. 

Anionic surfactants are organic compounds which upon dissociation in water produce large anions containing hydrocarbon chain. These anions are the carriers of the surface activity, while cations are not surface active at the air-solution interface. The description of the most important anionic surfactants is given below [27]. 

In the conditioning process, under suitable alkaline conditions, both ionization of functional groups at the bitumen surface [33, 105] and adsorption of the natural anionic surfactant molecules at the bitumen/ aqueous interface [100,101,104] occur. Descriptions of the experimental techniques, including microelectrophoresis, employed to study the effects are given elsewhere [100,102,104,106]. Figure 14 shows how addition of NaOH in the process increases the concentrations of surfactant in the aqueous phase, which in turn increases the extents of surfactant adsorption at all of the aqueous phase interfaces present in the system gas/ aqueous, bitumen/aqueous, and solid/aqueous. The adsorption increases until monolayer coverage is achieved and thereafter either levels off or continues into multilayer adsorption. 

Description Control electrostatic discharge at low concentration minimal effect on processing reactivity minimal effect on other polymer properties. Available as 100% active products or as fluids in a variety of solvents. Stable in dilute acids, unstable in strong alkalis compatible with nonionic and cationic surface active agents incompatible with soaps and anionic surfactants ... 

Several other anionic surfactants are commercially available such as sulfosuccinates, isethionates and taurates and these are sometimes used for special applications. A brief description of the above anionic classes is given below with some of their applications. 

A simple classification of surfactants based on the nature of the hydrophilic group is commonly used. Four main classes may be distinguished, namely, anionic, cationic, zwitterionic, and nonionic. A useful technical reference is McCutchen. Another useful text, by van Oss et al., gives a list of the physicochemical properties of selected anionic, cationic, and nonionic surfactants. The handbook by Porter is also a useful book for classification of surfactants. Another important class of surfactants, which has attracted considerable attention in recent years, is the polymeric type. A brief description of the various classes is given below. 

Surfactants are generally classified by ionic types which relate to their chemical structure and are described as anionic, non-ionic, cationic and amphoteric. Following descriptions of the theory behind surfactants, each category is considered with a brief summary of methods of manufacture but with the main emphasis on properties and applications. 

Information regarding the structure of EDL and the nature of some colloidal phenomena resulting from the interactions between ions and the interface can be obtained from the studies of electrocapillary phenomena, focusing at how the interfacial charge influences the surface tension. A complete description of electrocapillarity is given in courses in electrochemistry. Here we will only discuss the basic laws governing these phenomena that are important for understanding such colloidal phenomena as the adsorption of anionic and cationic surfactants, nucleation (see Chapter... 

In a series of papers we have developed a model for the thermodynamic properties of ionic surfactant-water systems [3-5]. This has led to fairly satisfactory description of phase equilibria in two and three component systems. As a continuation of this work we present a study of a model four-component system HiO-A X - A X where A and A are an anionic and a cationic surfactant, respectively, while X""X forms an ordinary electrolyte. Dealing with four components in studies of phase equilibria poses a substantial problem due to the complexity... 

In contrast to the Detergent Laws, the general water legislation does not cover the anionic and nonionic surfactants specifically, but it covers surfactants in the same way as any other components present in effluent however, this is not done via product-specific analytical methods, but within the ambit of the particular requisite parameters, or at least via general parameters such as, for example COD [chemical oxygen demand] or DOC [dissolved organic carbon]. However, this is then no longer specific to surfactants, so that a further description is unnecessary. 

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