Fate and cotransport of Pb(II) and Cd(II) heavy ions with bentonite colloidal flow in saturated porous media: The role of filter cake, counter ions, colloid concentration, and fluid velocity.

This study examines the transport and retention of colloidal particles and heavy ions in porous sand, focusing on the environmental risks associated with waste from oil and gas drilling. Experimental and numerical models assess the influence of flow rate, external filter cake layer, and ionic strength on bentonite clay particles and heavy ions, such as cadmium (Cd) and lead (Pb), in near-wellbore (high-flux) and far-field (low-flux) scenarios. Colloidal filtration theory and the one-dimensional convection-dispersion equation with two-site kinetic model for attachment and detachment were utilized to calibrate and predict the transport of colloidal suspension in porous media.