LONG-TERM BEHAVIOR OF TOXIC METALS IN STABILIZED STEEL FOUNDRY DUSTS

A study of the long-term behaviour of stabilized steel foundry dust (S FD) wastes has been performed using a dynamic leaching test (DLT). Two stabilized/solidified forms were produced by solidifying the SFD (con taining Pb, Cr, Cd and Zn) using either cement or cement and anhydrite (waste material) as binders. The results of the dynamic leaching test were fitted to a semi-empirical mathematical model based on simple le aching rate mechanism, which permitted the evaluation of an apparent d iffusion coefficient and a leachability index, thus providing a measur e of the contaminants' mobility in the solidified waste. In the case o f Pb and Zn, the rate of leaching was controlled by either an initial resistance or an initial washoff, followed by diffusion of the metalli c contaminants. The leaching indexes obtained in both cases were highe r than 12, suggesting that both solidification/stabilization processes are acceptable.