title: Retrograde adsorption isotherms: an impossible fact?
abstract: "Retrograde" adsorption isotherms have been reported, but seem to violate thermodynamics and would cause concentration steps to migrate against the direction of fluid-phase flow. In general, what appears to be retrograde behavior is caused by one or more additional, uncontrolled variables. This is illustrated with adsorption of sulfonate on a weak-acid ion exchanger, where adsorption is accompanied by partial conversion of the ion exchanger to the sodium form.
authors.affiliation: Department of Chemical Engineering, The Pennsylvania State University, University Park, PA 16802, USA. fxh1@psu.edu
authors.forename: Friedrich G
authors.initials: FG
authors.lastname: Helfferich
mesh_terms: D000327:Adsorption; D007475:Ion Exchange Resins / Q000737:chemistry*; D012964:Sodium / Q000737:chemistry; D013451:Sulfonic Acids / Q000737:chemistry; D013816:Thermodynamics
chemical_list: D007475:Ion Exchange Resins; D013451:Sulfonic Acids; D012964:Sodium