Successful heap leaching depends on three major factors: 1. Chemical conditions appropriate for the dissolution of the valuable
metal; 2. Contact between the leach solution and the valuable metal particles;
and 3. Movement of the leach solution through, and out of, the heap.
Given that appropriate chemical conditions can be provided, and the
individual particles have sufficient permeability to allow solute/solvent
contact, the problem of getting the solution to and from the particles
remains. Non-uniform percolation of solution throughout the heap,
caused by the presence of fines, is a common problem which occurs, to
some extent, with all heap leachable ore. The conventional solution to
this problem is agglomeration, which involves the attachment of fine
particles to larger particles, effectively modifying the size distribution by
preventing the fine particles from acting on their own. While agglomeration must be considered as an extremely effective
technique with virtually no limit to its application from a technical point
of view, its application is limited by economic considerations. A new technique has been developed which is not only a low cost
alternative to agglomeration, but also has the potential for enabling the
application of low cost heap and vat leach techniques to a significantly
wider range of ores than current practice would suggest. The new technique, known as Electrokinetic Leaching, utilises
electro-osmotic flow to enhance percolation through the heap. This paper describes and presents results of the laboratory testing, pilot
heap operation and commercial application of Electrokinetic Leaching of
a low grade gold ore and a tailings deposit. Comparative cost analyses between conventional and the alternative
processing techniques are presented.