Significance and Principal Features of Extended Driving Forces and a Transport Potential Model for Mass Transport between Two Liquids

Abstract

The fundamental characteristics and consistent structure of a new transport potential model and a set of new driving forces are reviewed. The model, derived for extractive mass transport of a solute between two liquids, adopts a new state quantity corresponding to the Gibbs free energy change of the species as an independent variable. Thus, the model has an approximate close relation to the thermodynamics. The present model incorporates the current two-film and pseudo-first order reaction models by introducing transport potentials. Three kinds of new driving forces are expressed as the gradients of the corresponding transport potentials for the forward, reverse and net processes. Accordingly, the dynamic exchange of a solute at equilibrium can be expressed. It is also shown that the transport potentials are analogous to the driving force defined in the non-equilibrium thermodynamics.

KEYWORDS:

• two-phase mass transport
• solvent extraction
• diffusion-controlled processes
• transport potential
• chemical potential
• Gibbs free energy
• reaction coordinate
• exchange driving force
• non-equilibrium thermodynamics
• TBP