Bio-beneficiation of multimetal black shale ore by flotation.
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Geological Survey of Finland
Jörg Landwaldt   

Geological Survey of Finland, Mineral Processing, Tutkijankatu 1, 83500 Outokumpu, Finland
Publication date: 2007-01-01
Physicochem. Probl. Miner. Process. 2007;41(1):291–299
Within the framework of the EU co-funded Bioshale project the bio-benefication of multimetal black shale ore was studied. The EU-co-funded Bioshale project aims to define innovative biotechnological processes for ‘’eco-efficient’’ exploitation of black shale ores. The ore sample was from the Talvivaara deposit in Finland. In the black shale ore sample, the total amount of sulphides was 31.5% of which the Ni-minerals pentlandite and altered pentlandite is 0.52%. Nickel is distributed into pyrrhotite and oxidized pyrrhotite, 32.5%, and pentlandite and altered pentlandite, 66.0%. Other sulphides are chalcopyrite (Cu), sphalerite (Zn), pyrite (Co) and alabandite (Mn). The ore sample contanied 12.3% graphite as a fine mixture with other minerals. In standard flotation, a low grade sulphide concentrate with 0.67 % Ni and nickel recovery of 74 % was obtained from the studied black shale ore. The mass of concentrate was then 34.5% of the ore feed. The recoveries of copper and zinc were 91%, of cobalt 89% and of manganese 53%. The content of carbon in the concentrate was 11.3% as graphite represents a naturally floating harmful mineral in the ore. The bioflotation tests showed that collector chemicals, i.e xanthates, had to be supplied to achieve reasonable flotation results. Out of the three tested bacterial strains, Staphylococcus carnosus, Bacillus firmus and Bacillus subtilis, the minor hydrophobic strain S. carnosus yielded the best test results. However, results of bioflotation tests failed to substantially improve the product recovery or grade.