UBC Theses and Dissertations
Examination of the mineralogical effects of biologically-assisted leaching of a mixed copper sulphide ore from the Ivan mine, Chile Melluish, Julie Marguerite
A mineralogical and biohydrometallurgical study of a mixed copper-sulphide ore from the Ivan Mine near Antofagasta in northern Chile was conducted by a multidisciplinary group at the University of British Columbia. The purpose of the mineralogical study was to establish an understanding of current knowledge regarding biologically-assisted leaching, especially as it relates to the solids involved, while supplying mineralogical support for the metallurgical experiments. An extensive review of bioleaching, a brief description of the Ivan Mine, a summary of the metallurgical experiments, a discussion of results from computer modeling of a column leach experiment, a report of the results from a detailed mineralogical study of the solid residues from two of the column experiments, and suggestions for future studies are included in this work. Bacteria that utilize energy derived from oxidation of reduced iron and/or sulphur species play an important role in the leaching of copper suiphides by catalizing specific reactions. Although much is known about the leaching process current understanding of the interactions between these bacteria and the solids in the system is incomplete. The simulation of a colunm leach experiment using the computer program PATH supplied useful insights into the chemical processes occurring. Although the overall column reaction was studied here, a modeling program such as this is useful for examining possible reactions in microenvironments within the columns. Detailed mineralogical examination of the solid residues from two of the column experiments revealed several interesting features. The insoluble precipitates forming in the column are jarosite, a non-crystalline iron-phosphate (possibly strengite), and a non-crystalline iron oxide-sulphate (possibly schwertmannite). These precipitates generally occur in porous particle coatings scattered with silicate mineral grains. The leached particles commonly exhibit an increase in the number of veins, voids, and regions of porous silicate alteration, predominantly in rims up to 500 μm thick. Larger veins and regions of porous silicate alteration expose the interiors of many particles to the leach solution. Bornite and anilite appear to alter to covellite before solubilizing. Dissolution of covellite and large chalcopyrite grains (commonly aggregates) occurs along grain boundaries sometimes leaving a porous crust of elemental sulphur.
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