Waste or Resource? Extraction Potential from Acid Mine Drainage for Useful Resources

摘要

Acid mine drainage could be a source of hydrogen, metals, and gypsum for energy and com-mercial products. For example, discharge from the Richmond Tunnel at Iron Mountain, California and the Reynolds adit at the Summitville mine, Colorado, each release between 30 and 200 metric tons per year of dissolved copper. For the period of 1994-2002, an estimated $6 million in copper and $14 million in iron was discharged from Iron Mountain. Instead of treating this drainage water with lime or limestone to produce an uneconomic sludge, the copper and other metals could be recovered and recycled into resources for commercial products. Currently a low-iron water near Breckenridge, Colorado, produces about 40,000 kg/yr of zinc by precipita-tion with sulfide and the insoluble material is shipped to a smelter to enrich the feed in zinc for better recovery. A demonstration plant removing high-purity gypsum from contaminated groundwater at a mining site in Arizona has been operating for more than 5 years. In China, removal of copper from an acid mine water by sulfide precipitation has also been found to be viable. The challenge is (1) to separate the valuable components from each other in a manner that is efficient and economically viable, (2) to stockpile components in an environmentally safe manner, and (3) to transport the separated components to an industry that can use them as source material for production. Every site must be assessed individually to ascertain what types of extraction, stockpiling, and transport are most appropriate.