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Pyrite Oxidation in Saturated and Unsaturated Coal Waste.
Achiev Land Use Potential Through Recl assmr 9-92 Am Soc for Surf Min & Recl P191-205 :15 pages
Currently, the main strategy used to limit acid mine drainage (AMD) from pyritic coal waste materials (i.e., spoil and refuse) is to minimize the contact of these materials with water. An alternative approach, not generally practiced in the coal industry, is to keep the pyritic material inundated with water. The U.S. Bureau of Mines conducted laboratory tests to determine the effects of dissolved oxygen and ferric iron on pyrite oxidation. These tests used triplicate small columns (5.1-Cm diameter by 46 cm) filled with 590 g each of coal refuse (2.54 Cm by 10 mesh) that contained 10.1 Wt pct pyritic sulfur. Four different hydrologic scenarios were studied: leaching with deionized water under unsaturated and saturated conditions and leaching with a ferric-iron-laden AMD under unsaturated and saturated conditions. Results indicate that maintaining the pyritic material under water virtually stops pyrite oxidation. After 189 days, sulfate loads removed from the columns averaged 34.5 +/- 4.9 G for the unsaturated columns leached with deionized water; 34.2 +/- 5.8 G for the unsaturated columns leached with AMD; 0.15 +/- 0.04 G for the saturated columns leached with deionized water; and -0.46 +/- 0.06 G for the saturated columns leached with AMD. The negative sulfate load indicates that sulfate was retained in the columns. Results from this and other studies, theoretical calculations, and experience from the metal mining industry show that disposal under saturated conditions can significantly reduce contaminant concentrations from pyritic material.
Achiev. Land Use Potential Through Recl.(assmr 9-92). Am. Soc. for Surf. Min. & Recl., P191-205
Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division