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AUG- 9-95 WED 16:C5 CROWN TECHNOLOGY FaX NO 3178159086 P. 06 <br /> TESTING <br /> Laboratory testwork Should be conducted to determine ferrous sulfate consumptions <br /> and residual cyanide levels in aclution following treatment. <br /> For tailings slurries, samples of slurry should be placed In agitated beakers and dif- <br /> ferent quantities of ferrous sulfate should be added to each beaker, By taking samples <br /> of the slurry at suitable intervals and titrating the solutions for free cyanide, reaction kinetics <br /> can be obtained. Thirty minutes total reaction time should be sufficient and the final free <br /> cyanide concentrations in solution are then determined. Ferrous sulfate addition rates to <br /> obtain the desired residual cyanide concentration can then be calculated. After ferrous <br /> sulfate is added to the tailings pond, free cyanide titrations of pond solution should be <br /> conducted on a routine basis, daily is preferable, to monitor for cyanide concentrations. <br /> Testing of heap leach dump treatment is simulated In column leach tests. After runn- <br /> ing cyanide solution through the columns, the columns should be allowed to drain. If stan- <br /> dard operating practice is to give the heaps a water wash prior to disposal, this should <br /> be done to the columns and allowed to drain. Known but different quantities of ferrous <br /> sulfate in solution should then be percolated through the columns. The columns should <br /> then be allowed to drain. A water wash should then be applied and free cyanide concen- <br /> trations In the drained solution should be determined at periodic Intervals. The amount <br /> of residual cyanide left in the columns can then be determined and ferrous sulfate addi- <br /> tion rates be calculated. A reference column test with no ferrous sulfate addition should <br /> be run to determine treatment effectiveness. <br /> — 4 — <br />