Evaluation of soil washing process to remove mixed contaminants from a sandy loam

Soil washing is a rernediation process which is primarily used to treat soils and sludges which are contaminated with only one or two groups of contaminants (e.g., metals and/or volatile organic compounds). This process, however, has not been extensively employed on soils that are contaminated with pesticides in addition to metals and volatile organic compounds. This paper decribes the development of a new soil washing process which is used to remove these mixed pollutants from soils. First, an overview of the soil washing process and its previous applications for soil remediation is presented. Then, an extensive experimental program which determined the most effective wash solution for removing mixed pollutants from a sandy loam is described. The sandy loam soil used for this experimentation was poorly graded, containing 66% sand and 34% silt/clay. The contaminants remediated in the experiments were: (1) metals; (cadmium, silver, and copper), (2) volatile organic compounds (ethyl benzene, methyl iso-butyl ketone), (3) halogenated compounds (chloroethene, tetra chloroethylene), and (4) pesticides, herbicides, and insecticides (lindane, methoxychlor, and endrin). The experimentation results determined that a combination of 2.5 N sulfuric acid and isopropyl alcohol in a 4:9 ratio and with a dilution of 5:1, solution to soil, would form as effective wash solution. The paper also describes the development of a bench-scale model and the results obtained from these bench-scale tests. These tests confirmed that the new soil washing process can remove the mixed pollutants efficiently and economically.