Diffusion-convection particles perfusive

Liapis and McCoy [63] have assumed that the bimodal pore structure of per-fusive adsorbent particles is made of a macroporous region, in which mass transfer takes place through intraparticle convection and pore diffusion, and a microp-orous region made of spherical microparticles in which mass transfer takes place through pure diffusion. Frey et al. [61] developed a model for the analysis of mass transfer in spherical particles having a bimodal pore distribution and derived the following expression for h nt in perfusion chromatography. 

Permeable particles containing large pores are used in separation and reaction engineering as adsorbents and catalysts. Perfusion chromatography, developed in 1990 [1] for the separation of proteins, is based on the concept of augmented dif-fusivity by convection [2], which combines the contributions of mass transport by convection and diffusion in adsorbent pores. An example of flow-through particles is given in Fig. 3.4-1 where wide pores are of the order of 7000 A and polymeric microspheres contain small diffusive pores. 

Fig. 9-2. Conventional and perfusion chromatography particles, (a) In a conventional chromatography particle there are no throughpores so convective flow is around the particle and the inner sites for adsorption are reached by molecular diffusion, (b) In a perfusion chromatography particle there are large throughpores which can be used for connective flow and so the inner site for adsorption are reached without molecular diffusion.

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