Removal of Heavy Metals and Radionuclides from Soils Using Cationic Surfactant Flushing

Soil excavation and ex situ decontamination are inevitable in some heavily contaminated industrial sites and Department of Energry sites, where heavy metals and radionuclides are most important inorganic contaminants in soils. Cesium-137 and cesium-137 are fission products typically present in nuclear wastes. Because of their long half-lives and high solubility, these radionuclides are considered among the most hazardous in the spent nuclear fuel. Sorption studies of Cs on kaolinite show that large amounts of Cs are sorbed onto the surface of kaolinite while associated cation desorption nearly equals Cs sorption, suggesting that ion exchange is the dominant mechanism. Lead is another widespread soil contaminant. Lead is sorbed on soil particles due to specific sorption and cation exchange. Several studies have used chelating agents to remove lead from soil, but with progressively higher pH, competitive chelation of EDTA by Ca, and to a lesser extent, by Mg, suppressed Pb solubilization, thus making Pb extraction less efficient. This research will examine the feasibility and applicability of using cationic surfactant as the desorbing reagent to remove heavy metals and radionuclides from soils using Pb and Cs to represent each. We hypothesize that the strong affinity between soil surface and long chain cationic surfactants can significantly increase Cs and Pb desorption kinetics and desorption efficiency. Previous results show that Sr and Zn desorption from zeolite surface was achieved using hexadecyltrimethylammonium. Since ion exchange is the dominant reaction of Cs and Sr sorption in soils, and geochemical similarity between Pb and Zn, it is expected that the desorption of Cs and Pb will follow the same pattern as with Sr and Zn.