Review on modeling the transport and retention of colloids in saturated porous media

The research progress on the modeling of colloid transport and retention in saturated porous media is reviewed. Colloids transport in porous media due to convection and dispersion but retain in porous media due to surface deposition and straining. The advection dispersion equation with retention term can effectively describe the form of the breakthrough curves and the retention profiles in the one-dimensional column tests, and the macroscopic transport and retention parameters of the colloid can be obtained through fitting. However, the convection dispersion equation is a macroscopic description of the test curves and cannot explain the microscopic mechanism behind them. The micromechanical analysis of colloid decides its transport and retention behavior, including the Brownian motion of the colloid itself, the interaction between colloid- colloid/colloid-solid surface, and the force of the flow field acting on the colloid. Macroscopic parameters of colloidal movement in porous media can be predicted based on colloidal filtration theory and its subsequent modification methods. However, existing methods are usually based on a simplified structure and internal flow field of porous media, ignoring the influence of pore structure and surface characteristics of porous media. The pore structure model is a simplified model of porous media pore structure. Based on this model, the macroscopic transport and retention behavior of colloids can be predicted considering the micromechanical analysis of colloids. However, the various effects of colloid transport and retention in porous media have not been fully considered in current studies. The problems to be solved in this field are summarized, including the establishment of convection dispersion equation considering microscopic mechanism, the development of colloid filtration theory considering pore structure of porous media, and the improvement of colloid transport and retention simulation method based on pore structure model. © 2022, Editorial Board of China Environmental Science. All right reserved.