Three isotherms for multisolute absorption of Freundlich type, the Ideal Adsorption Solution Theory, the Multicomponent Freundlich Isotherm and the Empirical Freundlich Isotherm are assessed and compared for convenience and reliability of application. Isotherms that describe adsorption from backgrounds of multisolute mixtures of unknown composition are derived for Langmuir and for Freundlich types of behavior, based on the Multicomponent Competitive Langmuir and the Multi-component Freundlich Isotherms respectively. Ways of using these expressions are proposed depending on available information and experimental strategies. Their descriptive and prediction validity and limitations are discussed and tested in a simulated adsorption experiment. Studies are recommended to determine distributions of absorption coefficients of representative backgrounds, using existing modern methods of fractionation, which will provide data for reliable estimation of adsorption equilibria.
- multisolute adsorption
- unknown backgrounds