The use of calcium to facilitate desorption and removal of cadmium and nickel in subsurface soils

The transport and elution behavior of Cd and Ni in the presence of Ca in subsurface soils was investigated using hatch and miscible-displacement experiments. The adsorption of Cd and Ni by the soils was dramatically decreased and their transport through the soils was significantly enhanced in the presence of Ca. These effects were attributed to the competition between Ca and these metals for exchange sites on the soil surfaces. The volume of CaCl₂ solution required to remove a certain % of Cd decreased with increasing concentration of CaCl₂. However, the concentration of CaCl₂ used to flush the soil did not significantly affect the final % of Cd removed, which was 90%. The position of the Cd elution peak varied with Ca concentration due to the nonlinear sorption behavior of Ca.