Mine Waste Technology Program, Electrochemical Tailings Cover (EPA/600/R-08/095) July 2008
This report summarizes the results of Mine Waste Technology Program Activity III, Project 40, Electrochemical Tailings Cover, funded by the U.S. Environmental Protection Agency (EPA) and jointly administered by EPA and the U.S. Department of Energy (DOE). MSE Technology Applications, Inc. implemented the technology demonstration for EPA and DOE. This project addressed EPA’s technical issue of Mobile Toxic Constituents – Water and Acid Generation.
The objective of Project 40 was to demonstrate the effectiveness of an electrochemical enhancement of conventional soil covers to inhibit the oxidation of sulfide minerals in mine waste to control generation of acid mine drainage. ENPAR Technologies, Inc. of Guelph Ontario, Canada, was the technology provider for trademarked electrochemical cover AmdEI™, which is an alternative to conventional earthen covers for decommissioning and long-term management of deposits of mill tailings and mine waste rock containing acid-generating sulfide minerals.
This demonstration showed evidence that the electrochemical tailings cover could reduce the oxidation of sulfide minerals in sulfide-containing mine waste. The reduction in oxidation of sulfur in the tailings was best shown by the post-test ABA analysis. The electrochemically treated cells retain total sulfur and pyritic sulfur at significantly higher levels than in the control cells that had no special treatment. In fact, treatment cell T2 retained over 90 percent of its original sulfur content. Nearly 50 percent of the sulfur was retained in the other treatment cell, T1; however, there was a large degree of variation in the initial sulfur data for this treatment cell, which seemed somewhat suspect due to high total sulfur content when compared to the three other test cells. Interestingly, both cells with the electrochemical treatment retained about 4.5 percent total sulfur while the untreated cells contained less than 0.05 percent sulfur at the conclusion of the demonstration. It is apparent that the sulfur was readily oxidized and leached away from the top few inches of tailings in the untreated control cells since initial total sulfur in the cells ranged from 4.78 percent to 9.44 percent.
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