Further applications of carrier-mediated transport theory—A survey

Recent studies of “facilitated diffusion” or “carrier-mediated transport” in membranes and liquid films, mainly as models of biological mass transfer, have led to several advances in the theoretical understanding and analysis of such phenomena. It will be shown here that many of the concepts and methods are applicable to a variety of processes involving diffusion and convection accompanied by homogeneous chemical reaction such as blood oxygenation, metallurgical oxidation or sulphation of alloys, and heat transfer in reacting gases.Thus, the notions of carrier-mediation, global reactivity versus non-reactivity, reaction invariance, and equilibrium or “frozen” transport, according to the appropriate Damkohler criteria, find widespread applicability in characterizing various molecular transport systems. The main objective here is to discuss the applications to the regime of rapid, near-equilibrium reaction.It is concluded that the boundary-layer methods developed recently for facilitated diffusion in membranes may be highly useful in the treatment of convection as well. There are, however, several important exceptions, which generally involve singular reaction equilibria and detached reaction zones, typical of rapid irreversible reaction exhibiting the classical “thin-flame” structure.