“…4,5 For systems that exhibit nonlinear increases in adsorption with solute concentration, several mathematical formulas can describe the adsorption process. Examples of nonlinear isotherms include Freundlich, 6 Dubinin-Ashtakov, 7,8,9 Tempkin, 10 Volmer, 11 Sips, 12 Fowler-Guggenheim, 13,14 Frumkin-Damskin, 15 RedlichPeterson, 16 Toth, 17 Levan-Vermeulen, 18 Vacancy Solute Theory, 19 Radke-Prausnitz, 20 Sigmoidal, 21 General Adsorption Theory, 22 Langmuir-Freundlich, 23 Margules, FowlerGuggenheim/Langmuir-Freundlich, 24 Fowler-Guggenheim/Jovanovic-Freundlich, 25 Jaroniec, 26,24 Ideal Adsorbed Solute Theory, 27,28,29 and Sheindorf-Rebuhn-Sheintuch 30 (see Appendix A). It is important to note that successfully fitting isotherms to adsorption data does not, in general, provide information about the mechanism of sorption.…”