Metals in waste foundry sands and an evaluation of their leaching and transport to groundwater

While most waste molding foundry sands (WFSs) are not hazardous in nature, regulatory agencies are often reluctant to permit their beneficial use in agricultural and geotechnical applications due to concerns over metal leaching. The objective of this study was to quantify total and Toxicity Characteristic Leaching Procedure (TCLP) metals in 16 waste sands from Brazilian ferrous foundries and assess their potential to leach metals to groundwater using a probabilistic model developed by the U.S. EPA. Total and TCLP metal concentrations in the non-hazardous sands fell within ranges as reported in the literature, although some of the leachate concentrations were found to exceed drinking water and groundwater maximum contaminant levels MCLs. Leachate values above the MCLs were then used in the model to estimate groundwater concentrations at hypothetical wells up to 400 m downgradient from the land application unit. A conservative scenario of one hectare of land applied WFS and high annual rainfall totals (> 1219 mm/year) suggested that groundwater concentrations of Ba, Hg, Mn, Ni, and Pb could potentially exceed health-based MCLs at most wells. Compared to moderate rainfall totals (813–1016 mm/year), the model demonstrated that wet climates can exacerbate the transport of metals from unconsolidated applications of WFS; however, the use of TCLP results as model input values is not considered appropriate for most byproduct beneficial use scenarios since it simulates low pH conditions within a municipal landfill

Use of an integrated approach to characterize the physicochemical properties of foundry green sands

A fresh green sand, spent green sand, and a weathered spent green sand from a landfill were analyzed using diffractometry, electron microscopy, granulometry, spectrometry, and thermogravimetry. Our objective was to understand how the physicochemical properties of the green sands change from their original form after being subjected to the casting process, then after weathering at the landfill. A quantitative phase composition model was also postulated for each material based on thermogravimetric results and it was found to be the most reliable and informative quantitative data for this type of residue. The weathered sample, that remained in a landfill for two years, was found to be composed of almost pure sand. Because of the weathering process, it may be possible to use the wSGS as a virgin sand replacement in the regeneration system or in geotechnical applications where bentonite would affect the properties of the final product

Use of an integrated approach to characterize the physicochemical properties of foundry green sands

A fresh green sand, spent green sand, and a weathered spent green sand from a landfill were analyzed using diffractometry, electron microscopy, granulometry, spectrometry, and thermogravimetry. Our objective was to understand how the physicochemical properties of the green sands change from their original form after being subjected to the casting process, then after weathering at the landfill. A quantitative phase composition model was also postulated for each material based on thermogravimetric results and it was found to be the most reliable and informative quantitative data for this type of residue. The weathered sample, that remained in a landfill for two years, was found to be composed of almost pure sand. Because of the weathering process, it may be possible to use the wSGS as a virgin sand replacement in the regeneration system or in geotechnical applications where bentonite would affect the properties of the final product

Metals in waste foundry sands and an evaluation of their leaching and transport to groundwater

While most waste molding foundry sands (WFSs) are not hazardous in nature, regulatory agencies are often reluctant to permit their beneficial use in agricultural and geotechnical applications due to concerns over metal leaching. The objective of this study was to quantify total and Toxicity Characteristic Leaching Procedure (TCLP) metals in 16 waste sands from Brazilian ferrous foundries and assess their potential to leach metals to groundwater using a probabilistic model developed by the U.S. EPA. Total and TCLP metal concentrations in the non-hazardous sands fell within ranges as reported in the literature, although some of the leachate concentrations were found to exceed drinking water and groundwater maximum contaminant levels MCLs. Leachate values above the MCLs were then used in the model to estimate groundwater concentrations at hypothetical wells up to 400 m downgradient from the land application unit. A conservative scenario of one hectare of land applied WFS and high annual rainfall totals (> 1219 mm/year) suggested that groundwater concentrations of Ba, Hg, Mn, Ni, and Pb could potentially exceed health-based MCLs at most wells. Compared to moderate rainfall totals (813–1016 mm/year), the model demonstrated that wet climates can exacerbate the transport of metals from unconsolidated applications of WFS; however, the use of TCLP results as model input values is not considered appropriate for most byproduct beneficial use scenarios since it simulates low pH conditions within a municipal landfill