A phenomenon of mass transfer with chemical reaction takes place whenever
two phases which are not at chemical equilibrium with one another
are brought into contact. Such phenomena are made up of a number of elementary
steps, which may be summarised as follows.
(i) Diffusion of one or more reactants from the bulk of phase I to the
interface between the two phases.
(ii) Diffusion of the reactants from the interface towards the bulk of
phase 2.
(iii) Chemical reaction within phase 2.
(iv) Diffusion of reactants initially present within phase 2, and/or of
reaction products, within phase 2 itself due to concentration gradients which
are set up by the chemical reaction.
Steps (ii) , (iii) and (iv) may take place simultaneously, and thus mutually
interfere; the overall phenomenon resulting from steps (ii) , (iii) and (iv) takes
place in series with step (i). If step (i) is rate controlling, the overall rate is
not influenced by the chemical reaction, and the process may be regarded as a simple mass transfer phenomenon which is not influenced by the reaction rate.
The analysis of mass transfer with chemical reaction is of interest when
the overall phenomenon resulting from steps (ii), (iii) and (iv) is rate-controlling.
Chemical reactions which accompany mass transfer between phases are
usually classified as, slow, fast and instantaneous.
In this paper the" nature of these reactions is described and the mathematical
models related to such phenomena are presented and discussed.
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