Langmuir equation, sorption behavior

A matrix of surfactant sorption experiments was conducted as a function of mixing time, initial concentration, and soil type for Tween 60, Tween 80 and Triton X-100. Although only data for Tween 80 and Appling soil are presented here, all of the soil-surfactant systems investigated ediibited Langmuir-type sorption behavior. The Langmuir equation may be written as ... 

Many empirical equations have been proposed to describe sorption behavior of aqueous species on solid surfaces. The most conventional methods of plotting sorption data are the Freundlich and Langmuir isotherms (7). Both isotherms were developed for the sorption of gases by solid surfaces. However, they often, but not always, describe the sorption of nonelectrolytes and other species from liquid solution onto solid... 

Both Equations [18.1] and [18.5] describe ideal cases. In many experimental situations, sorption isotherms are non-linear, showing a negative behavior compared to Henry s law. Some cases can be described using a dual sorption theory (Paul and Koros, 1976) in which the global sorption capacity is the result of two different contributions, one that follows Henry s law and a second that follows Langmuir behavior ... 

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