COLLOID TRANSPORT AND THE GAS WATER INTERFACE IN POROUS-MEDIA

The influence of the gas-water interface on the transport of colloidal sized particles through porous media was experimentally studied in micromodels and columns. The interfaces were created by trapping gas bubbles in the pore space. Several variables were tested: particle hydrophobicity, particle charge, and ionic strength of the solution. The gas-water interface adsorbed negatively and positively charged polystyrene latex particles and clean clay particles, over a wide range of ionic strengths. The degree of this adsorption increased with ionic strength. Positively charged particles had more affinity for the interface. Once particles were adsorbed onto the gas bubbles, it was difficult to detach them by shear stress. This adsorption was also irreversible to changes in ionic strength. A gas-water interface in motion effectively stripped particles from solid surfaces and carried them along. These results suggest that gas water interfaces play an important role in colloid transport, that might be manipulated to enhance aquifer remediation.