Heavy Metals Desorption from Synthesized and Natural Iron and Manganese Oxyhydroxides: Effect of Reductive Conditions.

Reductive conditions in soils can lead to the dissolution of iron and manganese oxyhydroxides, releasing heavy metal pollutants (e.g., Pb and Cd) bound to them. The present study used hydroxylamine as a reducing agent. Laboratory batch experiments were conducted, varying pH and hydroxylamine concentrations, with artificially contaminated synthetic amorphous Fe(OH)(3s) and MnO(2) and with a polluted cultivated soil. Until conditions were reductive enough to dissolve solids, remobilization of metals depended on their surface complexation constant and readsorption of metal was possible. However, if conditions were sufficiently reductive, all solids were dissolved and metals were released into solution. A straightforward surface complexation model for cation desorption was carried out to support these results. Copyright 2000 Academic Press.