Evaluation of Flow and Solute Transport Parameters for Heap Leach Recovery Materials
- David L. Decker * and
- Scott W. Tyler
Mining low-grade precious metals deposits often involves the bulk processing of ore by leaching with cyanide. Once the precious metals concentration in the leachate fluid drops to an economic cutoff point, processing ceases and the mine is required to meet drinking water standards for the latent leachate fluid that continues to drain from the heap. A common closure method is to rinse the heap with relatively clean water until the those requirements are met. However, it has been observed that concentrations of constituents, cyanide in particular, remain elevated at rinse times that exceed those times predicted with a simple advective-dispersive type of transport model. To quantify the flow and transport behavior of spent heaps, the hydraulic and solute transport characteristics of several heap-leach materials from northern Nevada have been determined. Data from the U.S. Bureau of Mines laboratory column tracer tests and new data collected from a series of tracer experiments with sodium Br− on heap material collected from the a large-scale heap in the Cariin Trend, Elko County, Nevada, are presented. A 6-m scale column incorporating time domain reflectometry was used to investigate the rinsing characteristics of spent heap-leach material. The breakthrough curve data from these experiments are analyzed using the traditional advection-dispersion equation and a dual-porosity model. The dual-porosity model provided significantly improved fits to the observed data compared with the advection-dispersion model. Data from the experimental results are used to show optimal rinsing strategies can be developed when heap hydraulic properties are considered.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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