Mass transfer - Mass transfer kinetics between two phases

While the study of chemical equilibria, or at least the general laws governing them, has long enjoyed independent status (it is in fact a branch of thermodynamics), the study of the kinetics of matter transfer, and particularly that of transfer at the interface of two phases, has remained essentially within chemical engineering.

Certainly, through reasoning based on similarity, it maintains close links with fluid mechanics and thermodynamics. In addition, non-equilibrium thermodynamics (developed by Onsager and his successors) has provided it with a conceptual framework. But none of these disciplines has succeeded in absorbing it, so far at least.

This detour into the recent history of science explains the presence in this treatise of an article devoted to the kinetics of matter transfer.

What's more, while the need for kinetic data essentially concerns transfer between two phases (§ 2 ), this article begins with developments on material transfer within a single phase (§ 1 ). This is not only due to a didactic concern (to go from the simple to the complex...). It is in fact a choice linked to the nature of the models.

Indeed, most of the models proposed and used to describe interfacial transfer are based on the assumption that the phase change, stricto sensu, is not the stage that limits the overall act, and that it is therefore the transport in either phase, between the core of these and the interface, that determines the transfer rate.