Gold mineralisation in selected bio-oxidised refractory gold concentrates
Date
2015
Authors
Asamoah, R.K.
Zanin, M.
Skinner, W.
Addai Mensah, J.
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Conference paper
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Asia Pacific Confederation of Chemical Engineering Congress 2015: APCChE 2015, incorporating CHEMECA 2015, 2015, iss.3126435, pp.177-188
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Asia Pacific Confederation of Chemical Engineering Congress 2015: APCChE 2015, incorporating CHEMECA 2015 (27 Sep 2015 : Melbourne, Australia)
Abstract
Formation of refractory secondary sulphate (RSS) minerals during biological oxidation (BIOX) and post- BIOX lime neutralisation have serious implications on the alkaline cyanide leaching stage. In this paper, physical surface activation (PSA) of biologically oxidized highly refractory flotation concentrate comprising RSS minerals has been investigated to enhance gold extraction rate and yield. Detailed particle size analysis (laser diffraction), mineralogy/chemistry (QXRD/XRF/laser ablation), gold occurrence in host gangue minerals (BSE/EDXS) and gold alkaline cyanide leaching behaviour of the leach feeds before (LFB) and after (LFA) surface activation have been reported. The results showed that PSA reduced the sauter and mass D[4,3]) mean diameters of the particles by approximately 30% and 51%, respectively, and increased the BET specific surface area by = 2.3 times. It was also observed that the mineralogy of sample LFB remained complex and approximately the same comprising mixture of silicates, oxides and sulphates after PSA (sample LFA). Gangue mineral agglomerates that were cemented by refractory secondary sulphate minerals (e.g., jarosite) were disintegrated after PSA and all associated/encapsulated gold particles liberated for extraction. The alkaline cyanide leaching rate of gold from sample LFA increased by = 2.5 times compared with sample LFB. It appears from the results that the increase in gold leaching rate and yield is not only due to the increase in surface area and reduction in particle size but also the liberation and activation of gold particles from deleterious cementation action of secondary sulphate minerals (jarosite).
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Copyright 2015 Engineers Australia