Kinetics of Surface Migration

Deslandes, Y. Study on the kinetics of surface migration of surface modifying macromolecules in membrane preparation. Macromolecules 2002, 35, 3017-3021. 

Suk, D., Chowdhury, G., Matsuura, T., Narbaitz, R.M., Santerre, P., Pleizier, G. and Deslandes, Y. 2002. Study on the kinetics of surface migration of surface modifying macromolecules in membrane preparation. Q mmolead 35 3017-3021. 

The migration of K on Fe/Al203 has been studied by Auger electron spectroscopy [234]. The migration is faster in H2 than in O2, and faster in moist gas than in dry. The kinetics of surface migration was found to be consistent with a surface diffusion mechanism [234]. 

The very striking phenomenon of surface migration during condensation is presumably due to the molecules striking the surface with considerable kinetic energy, so that they take some time to settle down into thermal equilibrium with the underlying solid, the oscillations of the atoms when... 

In addition to the theoretical studies of equilibrium adsorption, Roginskii has conducted extensive investigations of the kinetics of adsorption on nonuniform surfaces and has shown that the character of the kinetics of adsorption is dependent upon the presence or absence of surface migration. Migration of the adsorbate molecules brings about a redistribution which conforms with the values of the adsorption coeffi-... 

Analysis of the dynamics of SCR catalysts is also very important. It has been shown that surface heterogeneity must be considered to describe transient kinetics of NH3 adsorption-desorption and that the rate of NO conversion does not depend on the ammonia surface coverage above a critical value [79], There is probably a reservoir of adsorbed species which may migrate during the catalytic reaction to the active vanadium sites. It was also noted in these studies that ammonia desorption is a much slower process than ammonia adsorption, the rate of the latter being comparable to that of the surface reaction. In the S02 oxidation on the same catalysts, it was also noted in transient experiments [80] that the build up/depletion of sulphates at the catalyst surface is rate controlling in S02 oxidation. 

Fig. 16.3 Quantum yield (QY) for electron and hole transfer to solution redox acceptors/donors as a function of the reduced variables y (related to the surface properties of the catalyst, i.e., ratio between interfacial electron transfer rate and surface recombination rate) and w (related to the ratio between surface migration currents of hole and electrons to the rate of bulk recombination), according to the proposed kinetic model [23],...

The rate of adsorption and the rate of desorption are assumed to be dependent on the geometric relationship of the rock and solution (i.e., dependent upon the volume of solution and on the shape and area of the solid medium in contact with the solution). Because the dependence of sorption kinetics on the geometric relationship is not known, the rates for sorption are determined by experiment for the particular geometry (surface area of rock to volume of solution) for which the prediction of nuclide migration is desired. 

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