Colloid transport in natural porous media: influence of surface chemistry and flow velocity

Abstract Mobile colloids in soils and groundwater aquifers can act as carriers for strongly sorbing chemicals and may enhance contaminant transport. Field studies suggest that mobile colloids can include clay minerals, oxides or hydroxides of Fe and Al, colloidal silica, organic matter, and biocolloids such as viruses and bacteria. The transport of colloids through porous media strongly depends on the kinetics of colloid deposition and release. Important chemical factors controlling colloid deposition and release kinetics in natural porous media are the charge of matrix and colloid surfaces and electrolyte type and concentration in the solution phase. The surface charge is strongly influenced by solution pH and the presence of specifically adsorbing ions, including organic polyelectrolytes such as humic substances. Surface charge heterogeneities on colloids and matrix surfaces also play an important role. Colloid transport experiments conducted under well-controlled conditions were conducted to investigate the influence of surface chemistry, solution chemistry, and flow velocity on the kinetics of colloid deposition in natural porous media.