Metal extraction using bioleaching: an example from the Old Tailings Dam, Tasmania, Australia
2016
Mineralogical and geochemical characterisation of sulphide minerals in historic tailings can assist in
determining whether there are economic and environmental benefits of reprocessing such
materials using modern metallurgical practices. At the Old Tailings Dam (OTD), Savage River,
Western Tasmania, 38 million tonnes of pyritic tailings were deposited (1967 to 1982), and has
since been generating acid and metalliferous drainage (AMD). Long term management options
considered for this site have included the establishment of either a water, hard engineered or
vegetation cover. However, due to geotechnical challenges posed and the lack of success
demonstrated by previous pilot studies, these strategies have not been implemented. A detailed
mineral chemistry indicated elevated cobalt in pyrite (up to 3 wt. %), however, as this is refractory,
recovery via biohydrometallurgical processing was tested. Bulk tailings samples (n= 4) were collected across the OTD from up to between 0.5 to 1.5 m
depth specifically targeting three sulphide-bearing facies (C - E), across four physical zones (1 to 4;
defined by hydrological regime and grain size). A bulk composite of these materials was subjected to
bacterial oxidation using BIOX® bacteria to determine if Co could effectively be leached under
standard operating conditions. Our adaption testwork shows that the BIOX® bacteria were well
adapted to the lean OTD feed material after 10 days with 93% cobalt recovery. This indicates that
reprocessing of these deleterious materials may be a viable option for managing this historic site as
part of a larger tailings desulphurisation management strategy.
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