TRANSIENT DEPOSITION OF COLLOIDAL PARTICLES IN HETEROGENEOUS POROUS-MEDIA

A general theoretical model for particle deposition and transport in h eterogeneous porous media is developed. The model can describe the tra nsient particle deposition and the nonuniform particle coverage of por ous media surfaces, resulting from surface charge heterogeneity, surfa ce roughness, or other unevenly dis tributed surface properties. The m odel is applied to a packed-bed column with spherical collectors whose surfaces are heterogeneously charged. Results indicate that, under un favorable chemical conditions, it is the degree of surface charge hete rogeneity that mainly determines the transient (dynamic) deposition be havior. This transient behavior can be predicted by the flux-correctin g function, a function strongly dependent on the charge heterogeneity of solid surfaces. It is further shown that the effect of surface char ge heterogeneity on particle deposition dynamics can be quantitatively represented by a few parameters. These parameters are lambda, the fra ction of favorable surface sites, and alpha, the collision efficiency of colloidal particles with the unfavorable surface in the patchwise c harge distribution model; and psi(0), the average surface potential, a nd sigma, the standard deviation of surface potential in the normal ch arge distribution model. (C) 1994 Academic Press, Inc.