"The Bureau of Mines conducted physical and chemical beneficiation studies on three samples of waste investment casting molds to devise a method to liberate and recover zircon. Rod mill grinding, autogenous attrition grinding, and caustic leaching were liberation methods investigated. Flotation, gravity separation, and caustic leaching and sizing were recovery methods investigated. Flotation techniques produced concentrates containing up to 74.2 pct zircon with a zircon recovery of 53.4 pct. Gravity concentration produced concentrates containing up to 98.6 pct zircon; however, recovery of the zircon was only 57 pct. Caustic leaching and sizing produced concentrates containing up to 98 pct zircon with attendant recoveries of 81 pct. This report is based upon work done under a memorandum of agreement between the Bureau of Mines, U.S. Department of the Interior, and the University of Alabama." - NIOSHTIC-2 NIOSHTIC no. 10004547

National Institute for Occupational Safety and Health