Acid mine drainage extraction

Powell, R. W., "Hydrocarbon Extraction of Acid Mine Drainage, ... 

McCarty, D.K., Moore, J.N. and Marcus, W.A. (1998) Mineralogy and trace element association in an acid mine drainage iron oxide precipitate comparison of selective extractions. Appl. Geochem., 13, 165. 

J. B. Pfeiffer, The Treatment of Acid Mine Drainage—Two Years of Successful Operation, in Extraction and Processing for the Treatment and Minimization of Wastes,... 

Chakraborty et al. [76] also found that degree of chromiuin(VI) extraction is a function of time in acidic pH with the extractants Aliquat 336, tri- -octyl amine and their mixtures (see Fig. 4.9). Furthermore, a slight synergistic effect was observed when the two extractants were mixed. Valenzuela et al. [77] studied that the initial copper extraction rate was proportional to the concentration of oximic carrier in the organic phase and to the metal content in the acid mine drainage. 

Not all mine drainage or natural runoff from rock outcrops are acidic, even when extensive sulfide oxidation is present. Synthetic cyanide solutions, which are often used to extract gold and other metals from ores, can greatly increase the alkalinity of mining wastes and neutralize sulfuric acid (Craw et al., 1999). In other cases, the sulfuric acid is effectively neutralized by alkaline soils, limestones, dolostones, marbles, shams, or other carbonate-rich rocks (Pfeifer et al., 2004, 219 Razo et al., 2004 Lee, Lee and Lee, 2001, 491 Mendoza et al., 2006). Reactions between calcium carbonate and sulfuric acid may precipitate gypsum (CaS04 2H20). 

Mining also adds to the heavy metal pollution problem. As the earth is mined, deposits of minerals, which contain metals, are exposed. If the chemicals used in extracting ore or coal deposits are acidic, then the metals in the minerals are dissolved, and they may make their way into the surface water and sometimes the groundwater. This problem is sometimes controlled with a process that isolates mine drainage and then treats it to remove the metal ions. 

The source of the problem, highly contamined acid drainages from disposal of mineral wastes from coal extraction, has been thoroughly documented. Tables 1, 2, and 3 show the mineralogy, trace element content, and leaching concentrations of the trace elements for a typical coal waste derived from mining high-sulfur Appalachian coal in western Pennsylvania. 

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