The migration of the adsorbate from the solution to the composite sites was characterized by diffusion or by intra-particle diffusion (mass transfer through the pores), or could be a combination of both [33].
In this work, analytical solutions were derived (for any methanol oxidation reaction order) for the profiles of methanol concentration and proton current density, by assuming diffusion mass transport mechanism, Tafel kinetics, and fast proton transport in the anodic catalyst layer of a direct methanol fuel cell.
In this type of microfluidic device, mixing mainly operates by diffusion mass transfer, helped by hydrodynamic focusing.
According to these results, anodic peak current was controlled by the mass diffusion indicating a diffusion-controlled process.
They suggested that the significant decrease might be caused by the mass diffusion of nanoparticles.
Phase lags between γ(t) and A t) and low γmin can be predicted by convective-diffusion mass transfer models at spherical coordinates, or even by simple planar mass transfer models, without considering intrinsic surface rheology effects.
This arrangement allows perpendicular blood flow to the fibers, improving mass transfer by reducing the diffusion path length compared to parallel flow.
The membrane reactor is described numerically by a set of kinetic-diffusion mass balance equations.
For these reasons, it is not logical to locally place NO3 − as a N-depot in soil because it will rapidly move out of the original spot into the surrounding soil by diffusion and mass flow [31].
The concentration of Pi in the soil solution is often low (2 10 µ m) and, consequently, the supply of Pi to the root surface by diffusion and mass flow is slow (Bieleski, 1973; Barber, 1995).
