Interdiffusion coefficient, variation

Interdiffusion phenomena are governed by Pick s law but gas interdiffusion is not activated - the interdiffusion coefficients (variation of Xo in [12.25]) vary as a power of temperature. We will now focus on the catalytic act and more generally on the phenomena occurring at the catalyst s surface area. Gas pressures that will take part in the specified expressions are the pressures in close proximity to the surface. They become the partial pressures in the volume of the gas phase only in the case of very fast interdiffusions. 

Fig. 67. Experimental variations of the interdiffusion coefficient Qi(Q)/Q2 as a function of Q at the total polymer concentration c = 0.34 g/cm3 for the two investigated sytems ( ) diblock copolymer PSD-PSH 561/ben-zene + d-benzene ( ) mixture of homopolymers PSH155/PSD425/d-benzene. The solid lines are visual aids. (Reprinted with permission from [171]. Copyright 1989 American Chemical Society, Washington)...

The application of ion-exchange dynamics for the determination of HETP or HTU values should be studied in ion-exchange systems characterized by invariable static and kinetic parameters such as ion-exchanger swelling, electrolyte sorption, separation coefficient, and interdiffusion coefficients in solution and resin phases over experimentally investigated ranges of component variation. 

The process of solving the variation problem (Equations 12.46 and 12.47) will be performed according to the algorithm given in Equation 12.2. For the calculations, we use a set of parameters presented in Equation 12.2. To calculate the triple product sDh, we apply the expression for interdiffusion coefficient in Darken s approximations ... 

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