KINETICS OF COLLOID DEPOSITION ONTO HETEROGENEOUSLY CHARGED SURFACES IN POROUS-MEDIA

A general theoretical approach for the calculation of colloid deposition rate onto heterogeneously charged surfaces is presented. Patchwise and random distribution models are used to quantitatively describe surface charge heterogeneity and its effect on the kinetics of colloid deposition. It is shown that unfavorable surfaces with only minor amounts of charge heterogeneity have particle deposition rates that are orders of magnitude larger than similar surfaces having no charge heterogeneity. Furthermore, the sensitivity of particle deposition rate to solution ionic strength decreases as the degree of surface charge heterogeneity increases. Parameters characterizing the surface charge heterogeneity of collectors in porous media are identified from experimental data of colloid deposition by using the inverse procedure of parameter estimation. These heterogeneity parameters can be used in conjunction with current theories of particle deposition to explain experimental results of colloid deposition rates under chemical conditions that are unfavorable for particle deposition.