Mass transport processes oxygen diffusion coefficient

Many other cases of combined transport coefficients are in use, e.g. the combined (additive) transport of oxygen and metal ions commonly that we shall address later (and exemphfy by the high temperature oxidation of metals), the combination of two diffusivities involved in interdiffusion (mixing) processes, and the mass transport in creep being rate hmited by the smallest out of cation and anion diffusivities in a binary compound. As some of these sometimes are referred to as ambipolar or chemical diffusivities, we want to stress the above simple definition of ambipolar transport coefficients as relevant for membrane applications using mixed conductors. 

In general, the volatilization rate, iJy, is a first-order kinetic process (Appendix D-4 Liss and Slater, 1974 Mackay and Leinonen, 1975). For hi ly volatile compounds and for Henry s law constant He > 3000 torr volatilization rate is determined by the diffusion through the liquid-phase boundary layer (Appendix D-5). In cases where He < 0 torr M , the diffusion through the gas-phase boundary layer limits the volatilization rate. For conditions between 3000 and 10 torr both liquid and gas phase are significant. In these cases, the mass transport coefficients of the chemical in the water column are estimated from representative values of mass transport coefficient for oxygen reaeration and water where liquid-phase resistance and gas-phase resistance are controlled, respectively. 

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