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along with the trace associations of precious metals and heavy metals that occur. This is the material collected in the <br />table and flotation concentrate for sale to a third party for further treatment and refining. <br />The acid formation occurs through a natural weathering phenomenon of the sulfide minerals, in this case mainly <br />pyrites, with air and rainwater. This process occurs naturally underground as a natural geologic event. The problem <br />in this mining district is that the weathering process has been accelerated because the rock containing these minerals <br />has been brought to the suface and deposited in concentrated piles. With increased air transfer and increased <br />contact with rainwater, the accelerated oxidation creates an acidic nm-off more quickly that harms the environment. <br />The basic steps in this weathering chemistry can be seen as follows: <br />• Step one: The pyrite oxidizes upon contact with air and water. <br />Fe+2 + 1/4 O2 + H+ --> Fe+s +1/2 H2O <br />• Step two: Iron oxidizes to ferric iron. <br />FeS2 + 7/2 OZ + H2O --> 2SO4-2 + Fe +2 + 2H+ <br />• Step three: Precipitation occurs with ferric iron to ferric hydroxide. <br />Fer3 + 3H2O --> Fe(OH)3 + 3H' <br />• Step four: All combined to create a dilute sulfuric acid run-off. <br />• FeS2 + 1514 O2 + 7/2 H2O --> 2H2SO4 + Fe(OH)3 4 <br />For a very conclusive analysis of this phenomenon please reference A Water Handbook for Metal Minim <br />Operations, by Thomas R. Wildeman (attached in the appendix of Exhibit Q. This work was done considering <br />specific examples in this vicinity, <br />Using time in the mill process stream to regulate the pH to a more alkaline level is a good way to manage the <br />dissolved metals. According to Physicochemical Treatment Processes Volume 3 2nd edition 2005, by Lawrence K. <br />Wang, Yung-Tse Hung, and Nazih K. Shammas: <br />"Dissolved heavy metal ions can be chemically precipitated as hydroxide for removal by physical <br />means such as sedimentation or filtration. The process uses an alkaline agent to raise the pH of <br />the water that causes the solubility of metal ions to decrease and thus precipitate out of the <br />solvent <br />A simple form of the hydroxide precipitation reaction may be written as <br />.A42+ + 2(011)- = M(OH)2 (7) <br />The product formed is an insoluble metal hydroxide. <br />Reagents commonly used to effect the hydroxide precipitation include alkaline compounds such as <br />lime or caustic soda (sodium hydroxide). Linae in the form of quicklime or un-slaked lime, CaO, <br />and hydrated lime, Ca(OH)2, can be used. Lime is generally made into wet suspensions or <br />slurries before introduction into the treatment system. The precise steps involved in converting <br />line frorn the dry to wet stage will vary according to the size of the operation and the type and <br />• form of lime used. In the smallest plants, bagged hydrated lime is often charged manually into a <br />batch-mixing tank with the resulting "milk-of-lime " (or slurry) being fed by means of a solution <br />Page 28 of 31