Entropic effects in diffusion-adsorption processes in micropores
1 UMJ-Facultad de Ciencias, Universidad Nacional Autónoma de México Campus Juriquilla, Querétaro 76230, Mexico
2 Department of Physical Chemistry and Technology of Polymers, Silesian University of Technology, Strzody 9, 44-100 Gliwice, Poland
3 Facultat de Física, Universitat de Barcelona, Av. Diagonal 647, 08028 Barcelona, Spain
Revised: 23 April 2013
Published online: 17 June 2013
We analyze the kinetics of diffusion-adsorption processes of one component systems in micropores. In realistic situations, the pores exhibit irregular forms which give rise to inhomogeneous adsorption with preferred sites for the adsorbing particles. By modeling the tortuosity of the pores by means of entropic barriers, we obtain a kinetic equation for the averaged concentration of particles along the pore and on its surface. The analysis performed yields expressions for the adsorption rate, the effective diffusion coeffcient, the adsorption isotherms and the concentration of the adsorbed particles. It is shown that this last quantity strongly depends on the form of the pore. This feature opens the possibility to design micropores with an optimal adsorption rate at selected sites. Our results show that to consider the geometry of the pore in the reaction-diffusion scheme is crucial to reproduce experimental observations of the concentration of adsorbed particles in micropores.
© EDP Sciences, Springer-Verlag, 2013