Leaching behaviour of mechano-chemically activated bio-oxidised refractory flotation gold concentrates

• Published in: Powder technology 2018-05, Vol.331, p.258-269
• Main Authors: Asamoah, Richmond K., Skinner, William, Addai-Mensah, Jonas
• Format: Article
• Language: English
• Subjects: Activation; Agglomerates; Biological oxidation; Cleaning; Concentrates (ores); Cyanide leaching behaviour; Cyanides; Disintegration; Flotation; Gangue; Gold; Leaching; Mechano-chemical activation; Minerals; Organic chemistry; Oxidation; Particle size; Physico-chemical properties; Pulp; Reagents; Refractory gold ores; Thermal resistance
• ISSN: 0032-5910; 1873-328X
• DOI: 10.1016/j.powtec.2018.03.040

In this paper, the leaching behaviour of mechano-chemically activated, refractory, bio-oxidised flotation gold concentrates has been investigated. In particular, the effect of activation parameters (e.g., milling time and speed, and ball to pulp ratio) and cognate physico-chemical changes on the impact of the refractory mineral components in the ore was studied. The results showed that mechano-chemical activation led to reduction in the average particle size and increased surface area and reagent consumption in tandem with remarkable mineral amorphisation of the bio-oxidised products. The gold yield increased by a maximum of ~1.8 times after 24 h of cyanide leaching, irrespective of the magnitude of milling speed, milling time, ball to pulp ratio and the degree of mineral amorphisation. Furthermore, the increase in reagent consumption was consistent with increasing mineral particle stress and exposure of reactive gangue mineral phases (e.g., sulphate minerals), a factor that least influenced the gold yield. It appears that the improvement in gold extraction efficacy was due to gold surface cleaning, creation of pores/crevices that are linked to gold sites, and disintegration of gold-gangue mineral agglomerates that encapsulated gold particles. The findings were consistent with the nature of refractoriness and necessary for understanding ways of mitigating gold refractoriness in bio-oxidised flotation concentrates. [Display omitted] •Mitigation of bio-oxidised gold concentrate refractoriness posed by secondary mineral gold passivation.•Complementing ore bio-oxidation with mechano-chemical activation for improved gold extraction.•Increasing mechanical stress does not always increase processability of mineral ores.