Toxic Metal Removal from Polluted Soil by Acid Extraction

Sulfuric acid leaching is a promising technique to extract toxic metals from polluted soils. The objective of this study was to define the optimum sulfuric acid leaching conditions for decontamination of the fine particle fraction (<125???m) of an industrial soil polluted by Cd (16.8?mg?kg^?1), Cu (3,350?mg?kg^?1), Pb (631?mg?kg^?1) and Zn (3,010?mg?kg^?1). Batch leaching tests in Erlenmeyer shake flasks showed that a soil pulp pH between 1.5 and 2.0 using a solid concentration (SC) ranging from 5 to 20?% is adequate to efficiently solubilize toxic metals. Leaching tests performed at different temperatures (20, 40, 60 and 80?°C) also revealed that it is not beneficial to heat the soil suspension during the leaching treatment. The application in a 1-L stirred tank reactor of five consecutive 1-h leaching steps at 10?% SC and ambient temperature, followed by three water washings steps resulted in the following metal extraction yields: 30?% As, 90?% Cd, 43?% Co, 7?% Cr, 88?% Cu, 75?% Mn, 26?% Ni, 18?% Pb and 86?% Zn. The decontaminated soil conformed to Quebec norms for commercial and industrial use of soil.