Bioleaching

This investigation compares bacterial leaching to chemical leaching to solubilize copper from a copper containing ore of the new site Northern Qarashoshaq in Zhylandy (Kazakhstan) which is currently under commercial development. From ICP-OES analysis the bulk ore sample contains 1.5% of Cu and a trace level at 0.0024 % of Ag. Phase analysis shows the main copper containing minerals are covellite, сhalcocite, malachite, chrysocolla and chalcopyrite. According to X-ray diffraction analysis silver is mainly presented as jalpaite (Ag3CuS2) minerals. Copper leaching was carried out by acidophilic bioleaching for comparison with extraction by chemical methods involving the addition of sulfuric acid and Fe3+ or only sulfuric acid in flasks, as well as column leaching tests to simulate heap leaching. Ag was extracted by cyanidation methods again in flasks as well as column leaching tests. Results showed that copper extraction is up to 95% when using bioleaching in the flask, 83% in the case of Fe3+ with sulfuric acid and 76% for sulfuric acid. Furthermore, subsequent extraction of Ag reaches 97% for bioleaching and 92% for chemical leaching. Column bioleaching tests showed an 82.3% yield of copper after 70 days of the experiment and a 70% of silver, whereas for chemical leaching the yield of copper is 66.8% and silver is 51%. In conclusion this investigation demonstrated higher extraction for both copper and silver from the primary ore in the bioleaching sample compared to the chemical leaching sample. More silver was extracted in the bioleaching case as there was less copper remaining to compete for the cyanide anions.

Fe 2+ oxidation by Acidithiobacillus ferrooxidans (At. ferrooxidans) under different solid contents by adding inert Al 2 O 3 powder was examined in rotating-drum and stirred-tank reactors. The results show that the bioactivity of At. ferrooxidans in the stirred-tank is higher than that in the rotating-drum in the absence of Al 2 O 3 powder, but the biooxidation rate of Fe 2+ decreases markedly from 0.23 g/(L·h) to 0.025 g/(L·h) with increasing the content of Al 2 O 3 powder from 0 to 50% (mass fraction) in the stirred-tank probably due to the deactivation of At. ferrooxidans resulting from the collision and friction of solid particles. The increase in Al 2 O 3 content has a little adverse effect on the bioactivity of At. ferrooxidans in the rotating-drum due to different mixing mechanisms of the two reactors. The biooxidation rate of Fe 2+ in the rotating-drum is higher than that in the stirred-tank at the same content of Al 2 O 3 powder, especially at high solid content. The higher bioactivity of At. ferrooxidans can be maintained for allowing high solid content in the rotating-drum reactor, but its application potential still needs to be verified further by the sulfide bioleaching for the property differences of Al 2 O 3 powder and sulfide minerals.

Biological formation of K + and NH 4 + jarosites. Raman and FTIR microspectroscopies to probe the whole ore chalcopyrite–bacteria interactions. Probing the matrix of the extracellular polymeric substances during the bioleaching process. a b s t r a c t The whole ore chalcopyrite–bacteria interaction and the formation of the extracellular polymeric substances (EPS) during the bioleaching process by microorganisms found in the mine of Hellenic Copper Mines in Cyprus were investigated. Raman and FTIR microspectroscopies have been applied towards establishing a direct method for monitoring the formation of secondary minerals and the newly found vibrational marker bands were used to monitor the time evolution of the formation of covellite, and the K + and NH 4 +-jarosites from the chalcopyrite surfaces. The Raman data indicate that the formation of K +-jarosite is followed by the formation of NH 4 +-jarosite. The variation in color in the FTIR imaging data and the observation of the amide I vibration at 1637 cm À1 indicate that the microorganisms are attached on the mineral surface and the changes in the frequency/intensity of the biofilm marker bands in the 900–1140 cm À1 frequency range with time demonstrate the existence of biofilm conformations.