Electrochemical studies on interplay of mineralogical variation and particle size on bioleaching low grade complex sulphide ores

The interplay of mineralogical variation and mineral phase distribution within varying particle sizes on the dissolution behaviour of a low grade complex sulphide ore was investigated through bioleaching experiments and electrochemical technique. Investigations were carried out utilizing mineralogical data on the variations in mineral and phase distribution within particle sizes of <53μm,53-75μm,75-106μm and 106-150μm in mixed mesophilic cultures of Acidithiobacillus ferrooxidans,Acidithiobacillus thiooxidans and Leptospirillum ferrooxidans.Electrochemical behaviour was studied using particulate electrodes from the four varying particle sizes and from massive electrodes prepared from the two major sulphide mineral rich phases(sphalerite-rich and galena-rich)and a complex mineralogical phase of the bulk ore.Bioleaching studies reveal the highest recoveries at a particle size of 75μm,while electrochemical investigations reveal the highest dissolution at particle size of 106μm.Electrochemical results show that sphalerite rich phase has the highest dissolution rate while galena-rich complex phase has the least.SEM studies confirm the highest bacterial attack at the sphalerite-rich phase.The discrepancies between the dissolutions within particle sizes obtained from bioleaching experiments and electrochemical studies are consistent with and attributed both to the physical and mineralogical influences.Electrochemical behaviour is influenced and controlled by galvanic interaction resulting from mineralogical variation, while bioleaching behaviour is influenced by mineralogical variation as well as physical effect of particle size.

Role of ore mineralogy in optimizing conditions for bioleaching low-grade complex sulphide ores

The role that ore mineralogy plays in understanding and optimizing the conditions favouring the bioleaching of complex sulphide ore containing high amounts of siderite was studied using mixed cultures of mesophilic bacteria,with emphasis on zinc,lead and copper recoveries.The influencing parameters investigated include particle size,stirring speed,volume of inoculum,pulp density,and pH.The results show that the mixed mesophilic cultures can extract about two and a half times the amount of zinc than copper over an equivalent period of time.The highest zinc and copper recoveries of 89.2% and 36.4% respectively are obtained at particle size of 75 μm,stirring speed of 150 r/min,pulp density of 10% (w/v),12% (v/v) inoculum concentration,and a pH of 1.6.Variations in elemental composition within different particle sizes resulting from the mineralogy of the ore account for the bioleaching behaviour at varying particle sizes.The dissolution at varying pulp density,volume of inoculum,solution pH and the low solution potential observed are also influenced by ore mineralogy.

Study on the pre-treatment of oxidized zinc ore prior to flotation

The pre-treatment of zinc oxide bearing ores with high slime content is important to ensure that resources are utilized optimally. This paper reports an improved process using hydrocyclone de-sliming, dispersion reagents, and magnetic removal of iron minerals for the pre-treatment of zinc oxide ore with a high slime and iron content, and the benefits compared to traditional technologies are shown. In addition, this paper investigates the damage related to fine slime and iron during zinc oxide flotation, the necessity of using hydrocyclone de-sliming together with dispersion reagents to alleviate the influence of slime, and interactions among hydrocyclone de-sliming, reagent dispersion, and magnetic iron removal. Results show that under optimized operating conditions the entire beneficiation technology results in a flotation concentrate with a Zn grade of 34.66% and a recovery of 73.41%.