Fate of Sorbed Lead During Treatment of Contaminated Soils by Catalyzed H2O2 Propagations (Modified Fenton's Reagent)

Abstract

The release of lead sorbed onto three soils was studied during treatment with catalyzed H2O2 propagations (CHP) (modified Fenton's reagent). Soils from the Hanford Reservation, WA, Kamiak Butte, WA, and the front range of Colorado were spiked with lead, treated with CHP at pH 3 and pH 7, and analyzed for soluble lead. At pH 3, lead release was minimal from the Hanford soil while small releases occurred in the Kamiak Butte and Colorado soils. At pH 7, lead was not released from any of the soils. Because the Kamiak Butte and Colorado soils contained more soil organic matter (SOM) than the Hanford soil, the release at pH 3 may be due to the destruction of SOM with concomitant release of lead. CHP treatment at pH 7 also likely destroyed SOM in the Kamiak Butte and Colorado soils; however, the lead released then likely precipitated due to the higher oxidation-reduction potential of the pH 7 system. When hydroxyl radical was scavenged from the reactions, leaving the reductant superoxide as the primary reactant, lead desorption increased significantly. These results show that lead release is not significant during CHP remediation of soil and groundwater; however, CHP formulations that generate only superoxide may have promise for decontaminating lead-laden solids.