Papers by Author: Jörg Langwaldt

Abstract: Black schist ores in Finland are often enriched with sulfide minerals, containing a variety of base metals such as nickel, copper, zinc and cobalt. As these ores are low grade with respect to the metals contained and the sulfide minerals cannot be effectively concentrated from the schists, they are currently being studied with regard to their suitability for bioleaching [1]. As part of this investigation, a large-scale column measuring 3 x 3 x 9 m was built and filled with 110 tons of the crushed black schist ore. A solution was circulated in the column for 95 weeks; this solution was adjusted to 1.8 prior to entry in the column and averaged 2.7 when leaving the column. During this time, approximately 22% of Mn, 10% of Ni and 5% of Zn were leached from the ore. Iron was also leached, but precipitated in the column. Any soluble iron in the effluent was mainly Fe (II). During this same time period, total cell counts averaged 3.6 x 107 cells/ml of effluent. On three different occasions over nearly a one-year period, culturable cells were enumerated on a variety of solid media [2] and represented only about 1% of the total cell counts. Of the culturable cells, ironoxidizing acidophiles (namely Acidithiobacillus ferrooxidans) far outnumbered any other acidophile by at least a factor of ten. Changes in populations were also monitored by molecular means (T-RFLP and SSCP) on five different occasions during the same year; again, populations in early samples were dominated by Acidithiobacillus ferrooxidans (at least two strains/sub-species). As the temperature of the column was increased from ~20 to 35°C by heating both the recirculated liquor and the air used for column aeration, the relative abundance of At. ferrooxidans-like bacteria decreased while the abundance of unidentified bacteria increased. Some of these bacteria have also been detected in lab-scale column experiments using the same ore [3]. Total cell counts varied little as the temperature increased, nor was there any change in the rate of metal leaching. It was apparent that even though the leaching of metals from black schist ores was not greatly influenced by increases of temperature in the column, active microbial populations were present and were influenced by temperature.

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: The Bioshale project, involving 13 partners throughout Europe, is co-funded by the European Commission under the FP6 program. The main objective of this project (which started in October 2004) is to identify and develop innovative biotechnological processes for ‘’eco-efficient’’ exploitation of metal-rich, black shale ores. Three extensive deposits have been selected for R&D actions. These are: (i) a site (in Talvivaara, Finland) that, at the outset of the project, had not been exploited; (ii) a deposit (in Lubin, Poland) that is currently being actively mined, and (iii) a third site (in Mansfeld, Germany) where the ore had been actively mined in the past, but which is no longer exploited. The black shale ores contain base (e.g. copper and nickel), precious (principally silver) and PGM metals, but also high contents of organic matter that potentially handicap metal recovery by conventional techniques. The main technical aspects of the work plan can be summarized as: (i) evaluation of the geological resources and selection of metal-bearing components; (ii) selection of biological consortia to be tested; (iii) assessment of bioprocessing routes, including hydrometallurgical processing; (iv) techno-economic evaluation of new processes from mining to metal recovery including social, and (v) assessing the environmental impacts of biotechnological compared to conventional processing of the ores. An overview of the main results obtained to date are presented, with special emphasis on the development of bioleaching technologies for metal recovery that can be applied to multielement concentrates and black shale ores.