Spent Casting Sands

In most foundries, casting sands are recycled internally until they can no longer be used for casting. At that time, many of the sands, such as those from iron foundries, are landfilled as nonhazardous waste. Casting sands used in the production of brass castings may be contaminated with lead and must be disposed of as hazardous waste. Methods which can be employed to reduce the toxicity or volume of these wastes are discussed below  

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Foundries purchase new, virgin sand to make casting molds, and the sand is reused numerous times within the foundry. However, heat and mechanical abrasion eventually render the sand unsuitable for use in casting molds, and a portion of the sand is continuously removed and replaced with virgin sand. The removed sand becomes spent foundry sand, which is discarded from the foundry facility. 

Depending on the binder and type of metal cast, the pH of spent foundry sand12 can vary from approximately 4 to 8. As such, it has been reported that some spent foundry sands can be corrosive to metals.14 Spent foundry sand must be monitored to assess the need to establish controls for potential phenol discharges.91516... 

Other possibilities of management of spent foundry sands - originated from various casting technologies - are presented in Table I. 

The biggest disadvantage of tubes is their cost. The porous support tube (often fiberglass reinforced epoxy) is the dominant cost factor and the membrane area per foot of tube is low. When the membrane is spent, usually the whole tube must be replaced. PCI utilizes a "paper" insert on which the membrane is cast as the replaceable element. Others have developed epoxy bonded consolidated sand as the porous support in an attempt to reduce costs. 

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