Transient deposition of colloidal particles in heterogeneous porous media

A general theoretical model for particle deposition and transport in heterogeneous porous media is developed. The model can describe the transient particle deposition and the nonuniform particle coverage of porous media surfaces, resulting from surface charge heterogeneity, surface roughness, or other unevenly distributed surface properties. The model is applied to a packed-bed column with spherical collectors whose surfaces are heterogeneously charged. Results indicate that, under unfavorable chemical conditions, it is the degree of surface charge heterogeneity that mainly determines the transient (dynamic) deposition behavior. This transient behavior can be predicted by the flux-correcting function, a function strongly dependent on the charge heterogeneity of solid surfaces. It is further shown that the effect of surface charge heterogeneity on particle deposition dynamics can be quantitatively represented by a few parameters. These parameters are λ, the fraction of favorable surface sites, and α, the collision efficiency of colloidal particles with the unfavorable surface in the patchwise charge distribution model; and ψ₀, the average surface potential, and σ, the standard deviation of surface potential in the normal charge distribution model.