CHARACTERIZATION OF HEAVY-METALS IN SOIL BY HIGH-GRADIENT MAGNETIC SEPARATION

In recent years forecasting soil cleaning efficiencies of polluted soi l, especially those contaminated with heavy metals, has become an impo rtant issue. Failure of the methods to predict the right efficiency ha s resulted in financial losses and penalties. This article describes a n addition to the traditional characterization methods for soils conta minated by heavy metals, improving the quality of the basic decisions td be made. The method is based on magnetic separation using a Frantz Isodynamic Separator (FIS) for this study. The FIS isolates soil parti cles containing heavy metals so that these particles, which are releva nt for soil cleaning, can be studied in more detail. Four contaminated soils were tested for example, soils that were a problem for the soil -cleaning industry. The experiments indicate that each soil has its ow n magnetic properties that should be regarded as a fingerprint Density measurements of two soils show that densities approach the quartz den sity separated at moderate and high magnetic fields suggesting that so me of the heavy metals cannot be removed by density separation techniq ues. A pilot plant scale test supports this conclusion. It also shows that a part of the heavy metals are found in particles lighter than qu artz. Based on the results, a qualitative model is proposed to account for the presence of the heavy metals in soil.