Removal of Cu, Pb and Zn in an applied electric field in calcareous and non-calcareous soils

The pH dependency of the removal of Cu, Zn and Pb by electrodialytic soil r emediation from different industrially polluted soils was examined. From 18 experiments performed with five different soils, it was found that the ord er of mobilization due to a pH decrease was Zn > Cu > Pb. It was found, too , that each of the elements was removed at higher soil pH in calcareous soi ls (about 12% carbonates) than in soils with a carbonate content of less th an 3.7%. In soils rich in carbonates, precipitation of heavy metal carbonat es is an important retention mechanism and the heavy metal carbonates are d issolved at higher pH values than the pH at which heavy metals are desorbed in non-calcareous soils. Thus, the relation between the soil pH and the mo bility of the heavy metal in the electric field is not only dependent on th e heavy metal in focus, but also on the fraction of the heavy metal precipi tated as carbonates. (C) 2001 Elsevier Science BN. All rights reserved.