Papers by Keyword: Thermophilic

Abstract: The catalytic influence of Sulfolobus metallicus in the bioleaching of pure chalcopyrite at 70° C and pH 1.5 was studied in shake flask experiments. In order to evaluate separately the influence of planktonic and attached cells on the catalytic process, in some experiments the microorganisms were prevented from reaching chalcopyrite surface by keeping them in a chamber separated by a 0.1 Millipore membrane. Leaching, which was conducted with a -80 # + 120# chalcopyrite sample, was characterized from monitoring Eh, pH, copper, ferrous and ferric ion concentration in solution. In addition, the concentration of different sulphur species dissolved in solution either in aerated-abiotic and aerobic - biotic conditions, was determined with HPLC. Maximum copper dissolution was reached in experiments where all the microorganisms could reach chalcopyrite. In experiments where microorganisms were maintained separated from the sulphide, the population of microorganisms still increased. However, in this case copper dissolution was only 50 % of the maximum reached when contact of microorganisms with chalcopyrite was allowed, similar to that obtained in aerobic-abiotic conditions. On the other hand, in aerobic-abiotic conditions there was formation of bisulfite (HSO3)-, bisulfate (HSO4)- and sulfate (SO4)2-, while in leaching experiments where microorganisms could reach chalcopyrite the formation of thiosulfate (S2O3)2- and sulfite (SO3)2- was additionally observed. It can be concluded that bioleaching of chalcopyrite in the presence of Sulfolobus metallicus is the result of the cooperative action of attached cells which catalize copper dissolution through formation of thiosulfate, sulfite and bisulfite, and planktonic cells which further oxidize these intermediate compound to bi-sulfate and sulfate.

Abstract: In this work the leaching of black shale ore and froth flotation concentrates produced from the black shale was studied. The complex black shale contained various sulphide minerals (alabandite, sphalerite, pyrrhotite, pentlandite, violarite, chalcopyrite, pyrite). Concentrations of base metals in the ore were Fe 13.2%, Mn 0.97%, Ni 0.3%, Zn 0.57%, Cu 0.23% and Co 0.03%. The base metal content was two to three times higher in the flotation concentrate than in the ore. Ore and concentrate were leached in shake flasks and stirred tank reactors at pulp density of 10 to 20%, pH 1.2 to 2.0 and 60 to 77°C. A thermophilic enrichment culture related to Sulfolobus metallicus was applied. The pulp was aerated with ambient air and dinitrogen gas was used in a control test. Experimental duration was from 12 to 49 days. Leaching of Mn, Fe, Zn, Ni, Cu, and Co was up to 96, 52, 99, 99, 97 and 76%, respectively. Mn and Zn were rapidly leached within the first 2 to 3 days. In test with the ore, metal recovery was negatively affected by precipitate formation towards the end of leaching period. The H2SO4 consumption was in the range of 177 to 346 g/kg ore and 11 to 122 g NaOH/kg ore was consumed respectively. In bioleaching tests with flotation concentrates the H2SO4 consumption was from 205 to 415 g/kg concentrate and 73 to 183 g NaOH/kg concentrate was consumed, respectively. The final redox potential varied between 423 and 710 mV vs. Ag/AgCl. In experiments with fine ground ore, -50 8m, the ferric iron was at best 64% of dissolved total iron. Compared with coarser material (250-355, 710-1000 8m) leaching proceeded best with fine ground ore -50 8m). In tests with coarse ore (710-1000 8m). dissolved ferric iron was up to 97% of the total dissolved iron. Mechanical stirring and fine particles caused increase of dead cell numbers during leaching. The study demonstrates that the thermophilic enrichment culture can leach complex black shale ore at high pulp density and temperature.

Abstract: My perceptions of the biohydrometallurgical field span four decades and stem from being a professional microbiologist conducting academic research and research for process development and applications. My experiences have given me an appreciation for knowledge gained through fundamental research and the transfer of this knowledge to development of commercial scale applications of microbial processes. The symposia series for international activities in biohydrometallurgy has been a major factor in advancing knowledge and applications for microbial bioleach systems. The first international biohydrometallurgy meeting was held in Braunschweig, Germany in 1977. This was the predecessor for the International Biohydrometallurgy Symposia. As evident from the Symposia, advances in development and applications of biohydrometallurgy technologies follow an evolutionary, rather than revolutionary progression from demonstration of knowledge at the laboratory scale to engineering commercial plants.