Electrochemical soil remediation

Soil contamination, by several pollutants, is a serious environmental problem, which has recently attracted the attention of governments and environmental associations. Among the possible answers to that problem, electrokinetic soil remediation [1] represents a new technological development. This process has recently made significant advances and has been tested for commercial application in the United States and The Netherlands. When a DC current is passed through the contaminated soil, the contaminating species are transported towards the electrodes, and then removed from soil, under the action of the electric field. The electrochemical remediation takes place through different mechanisms depending on nature of the pollutant. Charged species respond to the applied electric field mostly by migrating through the soil solution [1]. Radionuclides, heavy metals, ionized organic compounds or mixed inorganic species and organic wastes are extracted from soils and slurries according to this mechanism [2]. Neutral species are essentially displaced by electrokinetic effects, like electro-osmosis [5,6]. Gasoline components, trichloroethylene, exachlorophenol have been extracted from polluted samples, exploiting the partition of the pollutant between solid phases in the soil and soil solution moving under applied field due to electro-osmotic effect. Electrophoresis phenomena may become important in the displacement of insoluble liquids dispersed as droplets in the spoil matrix.. Several works have dealt with heavy metals, and more generally inorganic species; while a significantly much less have been focused on decontamination from organic compounds. The feasibility and cost-effectiveness of electrokinetic remediation in extracting some inorganic species have been demonstrated. The efficiency of extraction relies upon several factors such as the type of pollutants, their solubility in the specific soil, their electrical charge, their relative concentration with respect to other species, their location and form in the soil; on the other hand, other important aspects are the availability of counter ions and/or organic matter in the soil, the type of soil, and the type of conditioning and enhancement scheme employed in the electrokinetic remediation process. The present communication focuses on the removal of organic species and heavy metals from a given, contaminated soil; in particular, data have been collected from the works realized in the last years and the in-situ application of the design in one Italian industry will be presented. [1] Z. Li, J. W. Yu and I. Neretnieks, J. Hazard. Mater., 55 (1997) 295-304. [2] Y. B. Acar, R. J. Gale, A. N. Alshawabkeh, R. E. Marks, S. Puppala and R. Parker, J. Hazard. Mater., 40 (1995) 117-137. [3] R.F. Probstein and R. E. Hicks, Science, 260 (1993) 498-503. [4] S. Pamukcu, Environmental Progress, 11 (3) (1992) 241-250. [5] A. P. Shapiro and R.F. Probstein, Environ. Sci. Technol., 27 (2) (1993) 283-291. [6] R. Lageman, Environ. Sci. Technol., 27 (13) (1993) 2648-2650.