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Significance of Concentration-Dependent Intracrystalline Diffusion and Surface Permeation for Overall Mass Transfer

Significance of Concentration-Dependent Intracrystalline Diffusion and Surface Permeation for Overall Mass Transfer
chair:

Heinke, L. (2007)

place:

Diffusion Fundamentals 4 (2007), 12.1.–12.11

Date: 2007

Heinke, L. (2007): „Significance of Concentration-Dependent Intracrystalline Diffusion and Surface Permeation for Overall Mass Transfer“. In: Diffusion Fundamentals 4 (2007), 12.1.–12.11

Abstract

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The intracrystalline concentration profiles ev olving during molecular uptake and release by nanoporous materials as accessi ble by interference microscopy contain a lot of hidden information. For concentration-independent tran sport parameter, the influence of surface resistances to overall mass transfer can be calculated by correlating the actual surface concentration with the overall uptake.

By using a numerical solution of Fick’s 2nd law and considering a large variety of concentration de pendencies of the transport diffusivity and the surface permeability, we show that the factor by wh ich the transport process is retarded by the surface resistance may reasonably well be estimat ed by the type of correlation between the actual boundary concentr ation and the total uptake at a given time. In this way, a novel technique of uptake analysis which may anal ytically be shown to hold for constant diffusivities and surface permeabilities, is s hown to be quite generally applicable.