Diagnostic leaching as an analytical tool for evaluating the effect of reagents on the performance of a gold plant

Abstract

Diagnostic leaching is an analytical tool which was developed at the Anglo American Research Laboratories to examine the deportment of gold in ore or any type of plant product. Diagnostic leaching can be carried out on fairly representative samples and produces easily interpreted results. The concept of diagnostic leaching is very simple, in that the least stable mineral present in the matrix of the sample is eliminated first in aqueous medium using a selective oxidative leach, after which cyanidation is used to extract the gold liberated by the destruction of this mineral. The gold extracted can be measured in solution to give a fairly accurate record of the amount of gold associated with that mineral. Furthermore, the residue from this first stage can be subjected to a more oxidative acid leach and the process repeated. At the end of this diagnostic leach, the metallurgist is left with an almost complete record of the deportment of gold in the sample. He can now use this information to design metallurgical flowsheets, solve problems occuring at an existing plant and/or evaluate the effect of various reagents on the performance of an existing plant. The information gained from a diagnostic leach indicates what changes in the process parameters are necessary or whether the process should be modified for a specific reagent. Diagnostic leaching can deal with any type of intermediary produced at a plant, thus making it an ideal analytical tool for analysing the effect of selective reagents on an intermediate stream. The method is flexible and depends on the intermediary or stream to be analysed. The technique of diagnostic leaching can thus be used in the laboratory by plant personnel, reagent manufacturers and distributors to evaluate the effect of introducing a reagent into the plant.