One-dimensional experimental investigation and simulation on the transport characteristics of heterogeneous colloidal Mg(OH) 2 in saturated porous media.

Recent laboratory studies have shown the injection of colloidal Mg(OH)2 could provide an effective and low cost alternative as a long term pH buffering system. In this study, Mg(OH)2 was modified by Tween 80 and SDS and the modified suspension had the properties of high stability, small particle size (the average particle diameter D50 was smaller than 1 μm) and negative charge (zeta potential = -14.26 mV at pH = 10.54). All of these properties demonstrated that colloidal Mg(OH)2 may have satisfactory transport performance in porous media. However, colloidal Mg(OH)2 is heterogeneous colloids with a high concentration, the transport performance in porous media is significantly different from homogeneous colloids, and the model simulation is relatively complex. To solve these problems, method of calculus combined with colloid filtration theory (CFT), T-E equation and modified Maxwell theory was used to simulate the transport performance of high concentration of Mg(OH)2 colloids. Results indicated that the observed experimental results matched well with the model simulations. Hydrodynamic force, DLVO attractive force and colloid diffusion are the major factors controlling the migration of colloidal Mg(OH)2 in porous media and could quantitatively describe the influence of injection velocity, porous media size and ionic strength on colloidal Mg(OH)2 transport properties by model calculation.