An evaluation of liberation models for the prediction of diagnostic leaching results

[摘要] ENGLISH ABSTRACT: The interrelationship between mineral liberation and leaching behaviour of a goldore is ill defined and lacks understanding mainly due to the complexity of theindividually processes, i.e. leaching and mineral liberation. An understanding ofthis relationship could result in lower costs, since an increase in the efficiency ofgold dissolution and a decrease in costs related to the crushing and grindingoperations, could be expected.Diagnostic leaching was used as the analytical method to investigate themineralogy (gold deportment) of various gold-bearing ores designating fromdifferent goldfields in South Africa. A thorough literature survey was alsoconducted to determine the availability of theoretical models which could describethe relationship between liberation and leaching behaviour.From the experimental results obtained, it was concluded that the leachability ofan ore is not only dependent on the degree of liberation of that ore whencomminuted, but that it is also very much dependent on the degree of exposure ofgold grains throughout the whole of the ore. It was found that all the theoreticalliberation and exposure models underestimated the amount of leachable gold ineach particle size fraction, mainly due to the neglecting of exposed gold grainssituated in minor cracks and fractures.It became evident in this research, that in order to model the leachability of goldfundamentally, the data obtained from diagnostic leaching tests alone areinsufficient. Data concerning the amounts of gold bearing minerals, present in theores as well as SEM data of the gold grains, are needed together with diagnosticleaching results.However, an empirical model was developed that predicts the degree of liberation(leachability) of an ore milled to 70% -75μm fairly accurately as a first attempt tomodel this highly complex process. The degree of liberation (leachability) wasfound to be a function of the particle size and the gold deportment of the unmilledore. It was decided to extend the King liberation model and the exposure modeldeveloped by Hsih and co-workers empirically to provide for the fraction of goldnot directly related to liberation. Both the models showed good agreements withthe experimental results. Neural network analysis of the diagnostic leachingresults were done with partial success, but unfortunately more data is still neededto assist in the development of an accurate leaching or liberation model.

[发布机构] Stellenbosch University