Experimental investigation for colloid migration in porous media under particle-rock repulsion

Electrophoretic mobilities of carboxylate-modified latex microspheres and zeta potential of soda-lime glass beads were measured at zero ionic strength and high pH. Surface potential for latex microspheres was calculated using Ohshima’s theory for soft particles. Total potential of interaction between colloidal particles and engineered porous medium evaluated according to DLVO theory showed negligibly small secondary minimum, a high potential barrier, and a primary minimum. Such conditions favour particle-bead repulsion resulting in size exclusion being a major particle retaining mechanism. Normalised outlet concentration is inverse function of particle concentration. Concentration of captured particles reduced along the length of the column in downstream direction. An analytical model for deep bed filtration of suspension in porous media and straining under size exclusion capture mechanism is developed and validated by laboratory tests on suspension flow in engineered media. The model is successfully matched with the results from column experiments, predicting the suspended particle concentrations at the outlet.