Characterization of extracellular polymeric substances extracted during the bioleaching of chalcopyrite concentrate

A mixed culture of moderately thermophilic microorganisms was used to bioleach chalcopyrite concentrate in a stirred tank reactor which achieved up to 84.7% copper extraction in 24 days at a pulp density of 6%. The leaching rate increased with an increase of dissolved total iron concentration. Extracellular polymeric substances (EPS) were extracted from the surface of the chalcopyrite concentrate during bioleaching and analyzed. EPS mainly consisted of proteins, lipids, sugars and ferric ions. After the 8th day the total amount of EPS remained relatively constant but the amount of ferric ion in the EPS decreased due to the formation of jarosite on the mineral surface.