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ARS Home » Research » Publications at this Location » Publication #208675
Title: The Characterization of Total and Leachable Metals in Foundry Molding Sands

Author
item Dungan, Robert - Rob
item Dees, Nikki

Submitted to: Journal of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/2/2007
Publication Date: 1/2/2009
Citation: Dungan, R.S., Dees, N.H. 2009. The Characterization of Total and Leachable Metals in Foundry Molding Sands. Journal of Environmental Management. 90:539-548.

Interpretive Summary: Molding sands are used by the foundry industry to cast metal objects. However, mechanical abrasion decreases the size of the sand particles, at which point the sands are land filled. While waste molding sands have been successfully used as a substitute for virgin sand in manufactured soils, concern over metal contamination must be addressed before many states will consider this beneficial use. Since there is little data available on this topic, the purpose of this study was to characterize total and leachable metals from waste molding sands. A total of 43 waste molding sands were tested for 19 metals. The total metal concentrations in the molding sands were like those found in agricultural soils. The leaching of metals was assessed via three different leaching procedures known as the toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), and ASTM water leach test. The TCLP was specifically designed to simulate acidic conditions in a sanitary landfill, while the SPLP was designed to simulate the leaching of metals and organics from wastes or contaminated soils with an extraction fluid similar to slightly acidic rainfall. Compared to the TCLP results, the metal concentrations were generally lower in the SPLP and ASTM extracts. However, all three leach tests revealed that the majority of the waste molding sands have a low metal leaching potential.

Technical Abstract: Waste molding sands from the foundry industry have been successfully used as a component in manufactured soils, but concern over metal contamination must be addressed before many states will consider this beneficial use. Since there is little data available on this topic, the purpose of this study was to characterize total and leachable metals from waste molding sands. A total elemental analysis for Ag, Al, As, B, Ba, Be, Cd, Co, Cr, Cu, Fe, Mg, Mn, Mo, Ni, Pb, Sb, V, and Zn was conducted on 36 clay-bonded (called green sands) and 7 chemically-bonded molding sands. Total metal concentrations in the molding sands were like those found in agricultural soils. The leaching of metals (i.e., Ag, As, Ba, Be, Cd, Cr, Cu, Ni, Pb, Sb, and Zn) was assessed via the toxicity characteristic leaching procedure (TCLP), synthetic precipitation leaching procedure (SPLP), and ASTM water leach test. Based on the TCLP data, none of the 43 molding sands would meet the RCRA characteristic for toxicity due to high Ag, As, Ba, Cd, Cr, and Pb. Compared to the TCLP results, the metal concentrations were generally lower in the SPLP and ASTM extracts, which is likely related to the buffering capacity of the extraction fluids. All three leach tests revealed that the majority of the waste molding sands have a low metal leaching potential.