Remediation of soil burdened with excesses of hydrophobic organic contaminants (HOCs) and toxic trace metals (TMs)

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Within the general objective of optimizing procedures to remediate soil that has been burdened with excesses of hydrophobic organic contaminants (HOCs) and trace metals (TMs), a series of studies have been designed to maximize the efficiency of the overall process while minimizing costs. The process consists of four sequential steps. Pollutants (HOCs and TMs) are simultaneously mobilized/removed from the soil by washing with an aqueous surfactant suspension (ASS) containing complexing reagent(s). The HOC fraction is recovered by back-extraction of the ASS phase with a non-polar organic solvent (hexane) and detoxified by hydrodechlorination /reduction during contact with a noble-metal catalyst. Subsequently, the heavy metal fraction is recovered by precipition with zero-valent magnesium (Mg0) to form insoluble oxyhydroxides that are recovered by filtration. The purified ASS fraction (now devoid of both HOCs and TMs) is returned to clean more soil. With this process, both classes of toxicant are converted to toxicologically innocuous products.