EFFECT OF BOUNDARY-LAYER MASS-TRANSFER RESISTANCE IN THE PERVAPORATION OF DILUTE ORGANICS

Pervaporation separation of dilute aromatic organic solutes is investigated. For the given hydrodynamic conditions, the mass transfer boundary layer resistance is found to contribute significantly to overall solute transport. The boundary layer effect is experimentally investigated by studying the variation of solute permeability with membrane thickness. In theory, the resistance-in-series concept is used to derive an equation for the variation of observed permeability with membrane thickness. The permeability coefficient is defined based on the general flux equation expressed in terms of the chemical potential driving force. Selectivity relationships for various conditions are also established. Further, an attempt has also been made to reconcile the seemingly different pervaporation expressions employed by various investigators. The current study, thus, seeks to emphasize the importance of the boundary layer resistance in studying the transport of organic solutes by pervaporation through a membrane with a high selectivity and/or permeability.