Adsorption isotherms Aggregates, formed from

Some essential discoveries concerning the organization of the adsorbed layer derive from the various spectroscopic measurements [38-46]. Here considerable experimental evidence is consistent with the postulate that ionic surfactants form localized aggregates on the solid surface. Microscopic properties like polarity and viscosity as well as aggregation number of such adsorbate microstructures for different regions in the adsorption isotherm of the sodium dedecyl sulfate/water/alumina system were determined by fluorescence decay (FDS) and electron spin resonance (ESR) spectroscopic methods. Two types of molecular probes incorporated in the solid-liquid interface under in situ equilibrium conditions... 

Until recently, the fast rate at which a surfactant layer forms at the solid-liquid interface has prevented accurate investigation of the adsorption process. As a result, the mechanism of surfactant adsorption has been inferred from thermodynamic data. Such explanations have been further confused by misinterpretation of the equilibrium morphology of the adsorbed surfactant as either monolayers or bilayers, rather than the discrete surface aggregates that form in many surfactant-substrate systems.2 However, the recent development of techniques with high temporal resolution has made possible studies of the adsorption, desorption,25>38,4i,48-6o exchange rates of surfactants. In this section, we describe the adsorption kinetics of C ,TAB surfactants at the silica-aqueous solution interface, elucidated by optical reflectometry in a wall-jet flow cell. The adsorption of C jTAB surfactants to silica is the most widely studied system - and hence the adsorption kinetics can be related to the adsorption process with great clarity. For a more thorough review of adsorptions isotherms, the t5q)es of surfactant structures that form at the solid-liquid interface, and the influence of these factors on adsorption, the reader is directed to Reference 24. 

Within this ehapter we are mostly concerned with physical adsorption. Our first task is to explore some simple and frequently used equations for adsorption isotherms. We will foeus on the acidity/basicity of the adsorbate and adsorbent as a eriterion for the adsorbate-adsorbent interaction energy, and make a special case of the adsorption of aleohol molecules from apolar solvents. The alcohol molecules self-assoeiate and form molecular clusters in apolar and inert solvents. This aggregation proeess may influence the adsorption process and will be encountered when diseussing and analyzing the alcohol adsorption isotherms. 

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