Decontamination of Heavy-Metal-Laden Waste Foundry Sand using Chelant-Assisted Washing Treatment

Abstract

Molding sands are used in the foundry industry to produce metal casting-molds during the casting process. A waste foundry sand (WFS) from foundry industry have been reused as construction materials.  Heavy metals in the WFS have been demanded to remove from the view point of resource strategy with environmental-friendship. In this study, a decontamination technique of heavy-metal-laden WFS by using chelant-assisted washing was used to the WFS containing copper (1.8 %) and lead (0.43 %).  Increasing of EDTA concentration significantly promoted metal dissolution due to conform chelate-complex.  A dissolution rate of copper was incremented by adding NH₃ and NaOH as dose-substance.  The optimum washing solution was composed of 50 mmol L^-1 EDTA, 0.2 mol L^-1 NaOH and 0.3 mol L^-1 NH₃.  The copper and lead in the WFS were quantitatively removed after 3 times of sequential treatments using comparatively moderate reagents; the removal efficiencies were 113 % and 96 %, respectively.