Numerical Simulation of Transport of Four Heavy Metals in Kaolinite Clay

A multicomponent reactive solute-transport model was used to study the migration of dissolved heavy metals (Cd 2+ , Pb 2+ , Cu 2+ , and Zn 2+ ) in a clay barrier subject to two leachates having different pH values. This solute-transport model is capable of simulating simultaneous processes of water flow, advective-dispersive-solute transport, and chemical reactions. The migration of these metals was simulated in a kaolinite landfill liner, which was assigned realistic physical and chemical properties and boundary conditions to model one-dimensional contaminant transport. The leachate input properties to the model were those of an actual leachate containing the four heavy metals. The numerical simulations were focused on the concentration profiles of these metals in the simulated clay barrier and leachate pH affects their mobilities. The numerical results indicate that with a nearly neutral leachate, the heavy metals mobility follows: Cd 2+ < Pb 2+ < Cu 2+ < Zn 2+ . With an acidic leachate, the order changes to Pb 2+ < Cu 2+ < Zn 2+ < Cd 2+ . Leachate pH has a significant effect on Cd 2+ and Pb 2+ mobility and a small effect on Cu 2+ and Zn 2+ .