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Suppression of pyritic sulphur during flotation tests using the bacterium Thiobacillus ferrooxidans
Author(s) -
Townsley C. C.,
Atkins A. S.,
Davis A. J.
Publication year - 1987
Publication title -
biotechnology and bioengineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.136
H-Index - 189
eISSN - 1097-0290
pISSN - 0006-3592
DOI - 10.1002/bit.260300102
Subject(s) - pyrite , chemistry , distilled water , sulfur , leaching (pedology) , thiobacillus , bioleaching , pulp (tooth) , coal , pulp and paper industry , thiobacillus ferrooxidans , flue gas desulfurization , tailings , environmental chemistry , metallurgy , mineralogy , chromatography , copper , environmental science , organic chemistry , materials science , medicine , pathology , soil science , engineering , soil water
Environmental concern about sulphur dioxide emissions has led to the examination of the possibility of removing pyritic sulphur from coal prior to combustion during froth flotation, a routine method for coal cleaning at the pit‐head. The bacterium Thiobacillus ferrooxidans was effective in leaching 80% and 63% −53 μm pyrite at 2% and 6% pulp density in shake flasks in 240 and 340 h, respectively. The natural floatability of pyrite was significantly reduced in the Hallimond tube following 2.5 min of conditioning in membrane‐filtered bacterial liquor prior to flotation. The suppression effect was greatly enhanced in the presence of Thiobacillus ferrooxidans. A bacterial suspension in pH 2.0 distilled water showed 85% suppression, whereas in spent growth liquor this value was 95%. The optimum bacterial density was 3.25 × 10 10 cells/g pyrite in 230‐ml distilled water (2% pulp density) in the Hallimond tube. The degree of suppression by the cells was related to particle size but not to pH or temperature. The sulphur content of a synthetic coal/pyrite mixture was reduced from 10.9 to 2.1% by flotation after bacterial preconditioning. It is postulated that pyrite removal in coals which are cleaned by froth flotation could be significantly reduced using a bacterial preconditioning stage with a short residence time of 2.5 min.