The most important result of this work is to show that, when extracting metal ions from contaminated soils, waterinsoluble chelators have the same yield when they are dissolved in a mostly aqueous, nontoxic solvent solution (e.g., a 99% water-1% ethanol mixture), as when more toxic systems (e.g., a 50% water-50% acetone mixture) are used. In addition, the solvent solution can be composed mainly of water, with only a very small amount (1% in our case) of solvent added to dissolve the complexing agent. These results extend and generalize those presented in Mauri et al. (1997).One of the most promising methods of separating metal ions is to complex them to a molecule (a ligand or chelator) that exhibits specific binding affinity for a toxic metal, even in the presence of other more benign metals (see the review article by Peters, 1999, and references therein). Because the selectivity of the chelators is critical to the goal of removing thc toxic metals from their less toxic counterparts, this approach consists of building a ligand framework that complements the unique characteristics of the toxic metal (size, charge, and shape) while minimizing interactions with nontoxic metals (Smith et al., 1996). Although environmentally benign wet extraction processes have been developed that use aqueous solvent solutions (Rogers et al., 1995; Huddleston et al., 19901, many chelators are water-insoluble, and therefore nonaqueous solvents are required.Our work on soil remediation is based on the results of our research in the related area of extraction of biological compounds from fermentation broths. Our approach was based on first adding solvents that are soluble with water to extract the solutes, and then phase separating the resulting mixture into two phases by changing either the temperature (Ullmann et al., 1905) or the composition (Gupta et al., 1996) of the that the extraction yield is much higher and the extraction faster than in conventional solvent extraction processes, due to the fact that the particles to be extracted are more effectively wetted by our water-soluble solvents than by the conventional, mostly water-insoluble ones. In fact. when the particles to be extracted are porous and preferentially wetted by water, conventional solvents cannot penetrate the pores well, resulting in very slow extraction (Gupta et al.. 1996).In this article, we intend to show that the experimental technique described in Gupta et al. (1996) can also be applied to soil remediation from metal ions, since, as most soils contain adsorbed water, their wettability by water-insoluble solvents is rather poor. In fact, to understand where the advantages of this approach lie, let us list some of the problems encountered in soil remediation by solvent extraction.Most of the compounds that form stable complexes with metal ions are only weakly soluble in water, and preferentially adsorb on soil. The low solubility of both ions and complexing agents in water makes water an unsuitable extractant. Now, more powerful solvents can be used instead, ...