EXTRACTION AND CHARACTERISATION OF EXTRACELLULAR POLYMERIC SUBSTANCES FROM THE MINERAL SURFACE DURING BIOLEACHING OF CHALCOPYRITE CONCENTRATE

摘要

A mixed culture of moderately thermophilic microorganisms was used to bioleach chalcopyriternconcentrate in a stirred tank reactor. The results show that up to 84.7 per cent of copper extractionrncould be achieved in 24 days at a pulp density of 6 per cent. The leaching rate of chalcopyriternconcentrate tended to increase with an increase of dissolved total iron concentration. Furthermore, thernextracellular polymeric substance (EPS) on the surface of the chalcopyrite concentrate was extractedrnand analysed. EPS was extracted at the first, third, eighth, 16th and 24th day during bioleaching, whichrnmainly consisted of proteins, lipids, sugars and ferric irons. After the eighth day the total amountrnof EPS remained relatively constant. However, the amount of ferric iron in the EPS decreased in arnlarge scale. The ore residue analysis indicates that the decrease of ferric iron was mainly due to thernformation of jarosite on the mineral surface.