Use of Standardized Procedures to Evaluate Metal Leaching from Waste Foundry Sands

Abstract

As part of the casting process, foundries create sand molds and cores to hold the molten metal to specifi c dimensional tolerances. Although most of the waste foundry sands (WFSs) from this process are land fi lled, there is great interest in diverting them for use in agricultural and geotechnical applications. One potential limitation to their benefi cial use is concern that the WFSs will leach high levels of trace metals. Th e aim of this study was to quantify Ag, Ba, Cd, Cr, Cu, Ni, Pb, and Zn in leaching extracts from 96 waste molding and core sands from ferrous and nonferrous foundries. Th e procedures used to assess leaching in the WFSs were the Extraction Procedure, the Toxicity Characteristic Leaching Procedure, and the American Society for Testing and Materials water extraction procedure. Th e metal extract concentrations were compared with those found in virgin silica sands and Argentinean and U.S. hazardous waste laws to determine if the WFSs met toxicity limits. Regardless of metal cast and sand binder type, the majority of the WFS extracts analyzed contained metal concentrations similar to those found in virgin sand extracts and were below levels considered hazardous. However, 4 of 28 sands that used alkyd urethane binder were deemed hazardous because Pb concentrations in these sands were found to exceed regulatory thresholds. Although other regulated metals, such as As, Hg, and Se, were not analyzed in the extracts, this dataset provides additional evidence that many WFSs have a low metal leaching potential. Use of Standardized Procedures to Evaluate Metal Leaching from Waste Foundry SandsRoberto E. Miguel, James A. Ippolito, Atilio A. Porta, Roxana B. Banda Noriega , and Robert S. Dungan* F errous and nonferrous foundries produce metal castings to supply a variety of large markets, including the automotive, mining, petroleum, and marine industries. As part of the casting process, foundries create molds and cores using sand (e.g., silica, olivine, chromite, zircon) as refractory materials. Th e molds are made of virgin or reclaimed sand and binding agents such as clays or organic resins. Molding sands made with calcium and/or sodium bentonite clay are called green sands, which also contain lesser quantities of bituminous coal and cellulosic materials to prevent casting defects. Core sand grains are almost exclusively bound with organic resins such as phenolic urethane, furan, and novolac (Dungan and Reeves, 2005), although natural protein-, oil-, and polysaccharide-based binders are also available (Roa, 2003;Yu et al., 2009). When assembled, molds and cores form a cavity that holds the molten metal to specifi c dimensional tolerances.Aft er the molten metal has solidifi ed, the mold is broken to retrieve the casting. Depending on the technology used within the foundry, the sands can be reclaimed to make new molds or cores. However, a fraction of a foundry's system sand must be regularly discarded and replaced with virgin sand to avoid casting defects as a result of poor sand quality. Th e discarded...

Metals in Waste Foundry Sands and an Evaluation of Their Leaching and Transport to Groundwater

“…The TCLP test has been applied to numerous WFSs; and in almost all cases, sands from iron, steel, and aluminum foundries were not determined to be toxic (Deng 2009;Miguel et al 2013). The leaching results were also compared to groundwater MCLs ( (Table 5).…”

Mid-infrared spectroscopic analysis of chemically bound metalcasting sands

“…Research to date, however, has demonstrated that many WFSs are not hazardous, as metal concentrations in leaching extracts were reported to be below regulatory thresholds [4][5][6]. These results are not surprising since total metal concentrations in waste sands from iron, steel, and aluminum foundries fall within ranges found in native surface soils [7].…”

Assessment of soil quality in the area of casting parts waste storage specific to cast iron activities

“…Numerous researches have been carried out on the composition of residual sand. The results of the experiments showed that the residual foundry sand is a new material, with a modified composition, compared to fresh sand [3][4][5][6][7][8][9][10][11]. Most foundry sands are non-hazardous waste, but environmental authorities are often reluctant to allow their beneficial use in agricultural and geotechnical applications due to metal leaching concerns.…”