Abstract
The theory of Irreversible Thermodynamics (IT), in particular the Generalized Maxwell-Stefan relations for describing the relative motion of species in a multicomponent mixture, is used to develop the fundamental basis for separation processes. The IT approach, and formulation, is shown to be indispensible in the estimation of the mass diffusivities of thermodynamically non-ideal fluid mixtures, description of separation processes in the region of the critical point, prediction of mass transfer rates and stage efficiencies in multicomponent separation processes, and for the correct modelling of separation processes involving more than one driving force. Use of the “dusty” fluid model allows the IT formulation to be consistently extended to the treatment of separation processes involving porous barriers of membranes