Magnetic and density characteristics of a heavily polluted soil with municipal solid waste incinerator residues: Significance for remediation strategies

• Magnetic and dense media separation can successfully remove metals from soil.
• In soil contaminated by incinerator ash, As and Sn are associated with iron material.
• Fe, As and Sn were concentrated in the magnetic fraction using low magnetic intensities.
• Density separation is the most appropriate method to treat inorganic contaminated soil.

Physical separation methods are usually the preferred extraction methods for inorganic contaminants. However, successful remediation of inorganically contaminated sites requires proper knowledge of the contaminants. This paper describes the magnetic and density characteristics of a soil polluted with municipal solid waste incinerator residues, allowing the best separation method or combination of methods for remediating the 0.250–1 mm and the 1–2 mm soil fractions to be selected. Magnetic characterization was performed using a CARPCO high intensity magnetic separator with increasing magnetic fields from 0.04 to 0.7 Tesla. A second characterization using a factorial design was performed for three magnetic field intensities (0.08 and 0.4 and 0.7 Tesla) and three relative density fractions (light, intermediate and heavy). The results showed that As, Fe and Sn can be concentrated into the magnetic fraction using low intensity magnetism but not Cu, Pb, Sb and Zn. Moreover, high intensity magnetic separation was not appropriate for concentrating the contaminants present in our soil. The association of the contaminants with iron likely explained this finding, especially for Sn. A significant overlap exists in the removal yields for magnetic and density separation of the different inorganic contaminants, ranging from 29% to 72% depending on the contaminants and the soil fraction. Density separation alone should be preferred to magnetic separation alone because of the better removal efficiency and the lower soil mass in the contaminated fraction afforded by density separation.