Enhanced Techniques of Soil Washing for the Remediation of Heavy Metal-Contaminated Soils

Soil washing has been developed as one of the ex situ traditional remediation methods for heavy metal polluted soils. It has been found to be effective in metal extraction. However, due to the distribution and speciation in soils, most metal(loid)s are present in less mobile forms which limit the washing efficiency. Therefore, methods are studied to enhance the washing performance by increasing the metals solubility and availability. This paper introduces some currently used methods and technologies, including the optimization of washing variables, lowering soil pH, application of assisted amendments and integration of electro-kinetic remediation and ultrasonication to enhance the removal of metals. In addition, it also suggests some further studies.