POTENTIAL RECOVERY OF CRITICAL ELEMENTS FROM HISTORICAL METAL MINING WASTE: THE EFFECTIVENESS OF USING VARIOUS LEACHANTS TO EXTRACT PRECIOUS METALS, PLATINUM GROUP ELEMENTS, SELECTED RARE-EARTH-ELEMENTS, AND VARIOUS INDUSTRIAL METALS

As part of an effort to examine the life cycle of mineral resources, we assembled and prepared about 100 historical metal mine waste samples from seven different deposit types. Bulk chemistry was determined on prepared samples using INAA, ICP-AES, and ICP-MS. We then leached the ground mine waste samples using a variety of leaching extracts that have been used by industry. Leachants included: aqua regia, sulfuric acid, cyanide (a limited number of samples), ammonium thiosulfate, and EDTA. After leaching, the extracts were analyzed using ICP-MS and ICP-OES. This presentation provides preliminary leaching results illustrating that various mineral deposit types produce diverse and unique leaching characteristics. The results also show that certain leachants are more effective than others in extracting specific elements from the mine wastes. When the leachate data are categorized by deposit type, the results indicate that historical mine waste piles could be a viable, untapped source of metals.