Soil washing for metal removal: A review of physical/chemical technologies and field applications

Soil washing is one of the few permanent treatment alternatives to remove metal contaminants from soils. This paper reviews the various technology types and pilot/full-scale field applications of soil washing applicable to soils highly contaminated with heavy metals. The physical separation technologies, the chemical extraction processes and the integrated processes that combine both physical and chemical methods are discussed separately. This paper reviews basic principles, applicability, advantages and limitations, methods of predicting and improving performance of each physical/chemical technology. The discussion is based on a review of 30 recent laboratory investigations and 37 field applications of soil washing systems which have been undertaken, mostly in the US, for the period 1990-2007. This paper also examines and compares the status of soil washing technology for remediation of soils contaminated with metals in the US, in Canada and in Europe.