2016-11-08_REVISION - M1980244 (8)

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9.2 pH of effluent after extraction 9.3 Total dry weight of mine rock sample used for MWMP. 9.4 Feed and retained (after extraction and draining) moisture contents. 9.5 Time of contact in the extraction device. 9.6 Procedures (synopsis) used for MWMP extraction, effluent filtration, and extract preservation. 9.7 Results of Profile I or Profile II analyses on extract. 1. Standard Methods for the Examination of Water and Wastewater, 18th edition, APHA/AWWANVEF, 1992, Method 1080. Based upon data collected for wet depositions in Nevada, obtained from Desert Research Institute, University of Nevada System, Type II reagent grade water most closely simulates meteoric water in Nevada in terms of both composition and pH range. Personal communication, M.N. Shen with Rick Stone, June 1995. 2. The extraction fluid can be metered via variable speed delivery devices such as peristaltic pumps or diaphragm pumps.A constant hydraulic head device can be used wherein a single speed pump delivers the extraction fluid to an elevated vessel which is equipped with an overflow back to the extraction fluid reservoir. The constant head vessel is tapped at the bottom to supply extraction fluid to the extraction column. A variable pinch clamp or screw clamp can be used to control the rate of extraction fluid application to the column. 3. The effluent container can be calibrated so as to overflow after the desired volume of extract has been collected. For example, if a 5 kg charge of solids is used, a 5 1 vacuum flask can be used as receiver. Sufficient inert glass beads can be added to the vessel to cause overflow when 5 1 of extract has been received. Therefore a technician need not be available at the exact time the target effluent volume has been achieved. 4. If the effluent contains finely divided suspended matter, filtration may be difficult. It is suggested that in such cases filtration through a 0.45 pm membrane be preceded by centrifugation and/or prefiltration using a larger pore glass fiber filter. 5.An aliquot for metals analysis must be preserved with reagent grade nitric acid to pH <2.An aliquot for phosphorus and nitrate analysis must be preserved with reagent grade sulfuric acid to pH <2. An aliquot for cyanide analysis must be preserved with reagent grade sodium hydroxide to pH > 12. All other analyses reported in Profiles I and II require only that the sample be stored without preservative at 4±2 deg C. 6. Residual moisture can be determined by placing a representative portion of the moist mine rock residue(following Step 8.9) into a pre-weighed beaker or similar vessel. The sample is then placed in an oven controlled at 105±2 deg C overnight, or until the difference between weighings at 30 minute heating intervals is less than 0.1%. The difference between wet and dry weight and multiplied by 100 yields the percent residual moisture: [(wet wt—dry wt)_dry wt] x 100 = %RM. Reference Nevada Mining Association (1996), Meteoric Water Mobility Procedure (MWMP), Standardized Column Percolation Test Procedure, Nevada Mining Association, Reno, NV, 5p.