Abstract
The distribution of the metal-bearing mineral grains within a particulate ore prepared for leaching, and the impact of this spatial heterogeneity on overall extraction efficiency is of key importance to a mining industry that must continuously target ever-reducing grades and more complex ore bodies. If accessibility and recovery of the target minerals is to be improved, a more detailed understanding of the behaviour of the system must be developed. We present an in situ analysis using X-ray computed tomography to quantify the rates of volume reduction of sulfide mineral grains in low grade agglomerated copper bearing ores during a miniature laboratory scale column leaching experiment. The data shows the scale of the heterogeneity in the leaching behaviour, with an overall reduction of sulphide mineral grains of 50%, but that this value masks significant mm3 to cm3 scale variability in reduction. On the scale of individual ore fragments, leaching efficiency ranged from 22% to 99%. We use novel quantitative methods to determine the volume fraction of the sulfide that is accessible to the leachate solution.
Highlights
The continued demand for commodity metals such as copper requires extraction from increasingly diminishing grades of ore, so maximising the efficiency of recovery from low grade ores in overall and energetic terms is of significant economic and environmental interest.Ideally these low-grade ores are processed to maximise metal recovery, leaving a waste rock with reduced environmental impact
The breccia material generally shows a higher leaching efficiency (9); The more coherent ore fragments exhibit variable leaching behaviour: some show a high degree of leaching (10); others show very little change (11); and some exhibit internally variable leaching (12); Some of the larger liberated sulfide grains have been removed completely. This appears to have occurred by leaching (13); whereas other grains may have dislocated from the region of study (14); Elsewhere the complex inter-grown nature of the sulfide phases is indicated by the variable and sieve like dissolution textures of some large sulfide grains (15), consistent with the differing leaching rates expected for pyrite, chalcocite and chalcopyrite
A lack of understanding of the mm3 to cm3 controls on leaching from ore fragments under heap conditions limits the development of predictive models that can be used to improve total Cu recovery and heap efficiency
Summary
The continued demand for commodity metals such as copper requires extraction from increasingly diminishing grades of ore, so maximising the efficiency of recovery from low grade The latest X-ray computed micro tomography (μCT) techniques are used to perform in situ visualisation and quantification of the mineral sulphide (MS) grains and gangue fractions, as well as assessment of the mineralogy (in this sample for some phases only), porosity and fracture networks within individual ore fragments, and the ore bed, as they undergo leaching in a small-scale laboratory column experiment. Nature of the behaviour of the sulfide using series the pre-analysis and post-leaching andThe performed agglomerated ore can be seenassessment in the 2Dusing slices the reconstructed volumes
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