Lyalikova, N. N.; Lyubavina, L. L.; Solozhenkin, P. M.; Institute of Microbiology of the Academy of Sciences, Moscow, USSR; Institute of Chemistry of the Academy of Sciences of Tadzhikistan, Dushanbe, USSR (1977)
      The culture of sulfate-reducing bacteria was used as a sulfideproducer for the enrichment of oxidized antimony and lead ores. The recovery of antimony and lead was 5~10% higher than extraction by standard floatation method. Sulfate-reducing bacteria were successfully used as the desorbent and depressor in floatation of sulfide collective concentrates resulting in selection of lead and zink, copper and molybdeniun, Sulfate-reducing bacteria could be used as highly effective float— ing reagent, if subjected to increased investigation in this direction. Applicat

      Ehrlich, Henry L.; Department of Biology, Rensselaer Polytechnic Institute Troy, NY 12181 (1977)
      A chalcopyrite-containing ore was shown to be able to retain measurable amounts of Cu2* ions from a 9 mM copper sulfate solution at pH values of 1.5 or above, which was percolated through it. The ore also exhibited significant buffering capacity when titrated with 0.01 N H,S0, or 0.01 N NaOH. Thiobacillus ferrooxidans strain Cu,S-2 accelerated leaching of the ore when using iron-free 1lixiviant at pH 1.5 or ferrous iron-containing lixiviant at pH 1.5. The total copper recovered in 20 weeks from inoculated percolation columns fed with ferrous lixiviant was the same as that recovered from inoculated columns fed with iron-free lixiviant, namely about 20% of the total copper in the ore, but the amount of copper recovered from uninoculated, sterile columns when using ferrous lixiviant was only about a third (3.2%) of that obtained with iron-free lixiviant fed to uninoculated, sterile columns in the same length of time (10.2%). When the ore was fed ferric lixiviant at pH 1.5, the bacteria exerted a strong retarding effect on the leaching process. In their absence, about 2.5 times as much copper (about 52% of the total copper in the ore) was recovered in 20 weeks than in their presence. The amount of copper recovered with bacteria in this case equalled approximately the amount recovered with bacteria using iron-free or ferrous ironcontaining lixiviants.

      Beck, Jay V.; Department of Microbiology, Brigham Young University Provo, Utah, USA (1977)
      Suspensions of intact cells of Thiobacillus ferrooxidans catalyze a rapid oxidation of finely ground chalcocite to covellite and soluble copper as shown in the following equation: 2Cu2S + 0» + 2HyS0, ————> 2CuS + 2CuS0, + 2Hy0 This reaction occurs spontaneously, but bacterial action increases the oxidation rate about 40 times. The oxidation reaction consumes protons thus causing an increased pH. Both spontaneous and biologically catalyzed oxidations cease when the pH reaches 4.6 - 4.7. In the presence of bacteria and under experimental conditions as described, a period of only about five hours is required to completely convert 0.3 gm of chalcocite to covellite with a 50% solubilization of the chalcocite copper.

      Zajic, J. E.; Jack, T. R.; Sullivan, E. A.; Faculty of Engineering Science The University of Western Ontario London, Ontario Canada (1977)
      The vast deposits of oil sands in the Province of Alberta Canada bear significant quantities of vanadium, nickel, titanium and iron in the bitumen component. During the production of oil from this bitumen, the metals are concentrated in the coke and coke ash refinery by-products. This study is concerned with the removal of metals, particularly vanadium, from the coke and coke ash obtained from different coking processes. The feasibility of marketable metal recovery by both chemical and microbially assisted leaching techniques has been assessed. Further the environmental impact of the solid waste disposal of untreated coke and coke ash has been evaluated by investigating the mechanism and extent of metal leaching under natural conditions and by investigating the toxicity of these "natural" leachates in a novel bioassay system. The study presents the data obtained in a critical evaluation of the leaching of metals from coke and coke ash in both economic and ecological contexts.

      Wyckoff, Ralph W. G.; Davidson, Franklin D.; Department of Physics, University of Arizona Tucson, Arizona, USA (1977)
      Studies have been made of the composition, morphology and ability to metabolize sulfides of certain autotrophic microorganisms collected from the neighborhood of fumaroles. Some are thermophilic and resemble the Sulfolobus described in the United States by Brock and the Brierleys. Others, living at lower temperatures, resemble but are in certain respects different from thiobacteria. They have been more effective than sulfur bacteria in attacking chalcopyrite and their reaction with this mineral is described. Attention is given to their pleomorphism and to their possibly primitive nature. Differences noted between strains from different localities emphasize the desirability of obtaining and testing samples from many sources, Our

      Le Roux, N. W.; Marshall, Vivian M.; Warren Spring Laboratory, Stevenage, Herts., England (1977-07)
      The aim was to study the effect of visible and ultra-violet light on some members of the genus Thiobacillus. This genus is one more example of an aerobic organism which undergoes what appears to be the widespread phenomenon of light inhibition. Light inhibition of thiobacilli has been observed before and these other observations are presented. In the present study the effect of both visible and U-V light on three species was considered viz. T.thiooxidans, T.thioparus and T.ferrooxidans, the latter species being studied more thoroughly with respect to different intensities and wavelengths of light and the shielding effect of bacterial numbers and ferric iron. The photoreactivation of T.ferrooxidans cells after irradiation by U-V light was also examined, Using unfiltered, visible light, there was an inhibitory effect on all three of the thiobacilli irrespective of the energy source being used. When selected wavelengths were studied it was seen that the blue end of the visible spectrum was most inhibitory. A relationship between ferric iron concentration and protection from visible light» was shown and the beneficial protective effect of particulate suspensions was demonstrated. afforded by ferric iron and cell numbers was assessed. Photoreactivation of U-V irradiated cells by exposure to visible light showed that this phenomenon occurred using wavelengths of visible light which, by themselves, were inhibitory. Some practical implication of these findings are offered.

      Barbic, F.; Lucic, J.; Babic, M.; Institut fur die Technologie von Nuklearrohstoffen und anderen mineralischen Rohstoffen, Belgrad (1977-07)
      Various sulphur compounds were investigated as energy sources for the growth of Th. ferrooxidans. At the same time the tolerance of Th. ferrooxidans for various compounds was examined. Th. ferrooxidans responds in different ways to sulphur compounds, depending on their kind and concentration. Some of the sulphur compounds examined can replace iron as an energy source. The compounds examined can be lethal to Th. ferrooxidans depending on their concentration.

      Illi, H.; Bertram, R.; Institut flir Physikalische Chemie, Technische Universitdt Braunschweig, Braunschweig, FRG (1977)
      Samples of naturally occurring chalcopyrite were dissolved anodically under potentiostatic conditions in various electrolytes. Limiting currents through the supply of holes were not observed. Because of the high current densities, even with a slight overpotential one observes a considerable resistance polarization depending on the conductivity of the electrolyte. A comparison with the results obtained through the leaching in the absence of current shows that the dissolution of the ore is strongly activated through the application of an external potential.

      Kelly, D. P.; Eccleston, M.; Jones, Carol A.; Department of Environmental Sciences, University of Warwick, Coventry CV4 7AL, England; Glaxo Research Ltd., Sefton Park, Stoke Poges, Buckinghamshire, England (1977-07)
      Thiobacillus ferrooxidans was cultured in continuous flow chemostats on FeSO, at pHl.6 and K was subject to one or other of non-competitive product inhibition (NCP1) or 254% at pH2.5. On iron as the limiting substrate, growth predominatly competitive product inhibition (PCP1). This resulted in premature washout at dilution rates dependent on the concentration of FeSO, in the medium feed. Growth yield, apparent maintenance energy requirement and maximum specific growth rate ae were determined over a wide range of dilution rates for cultures subject to either NCPl or PCP1l. With tetrathionate as the limiting substrate no inhibition effects were observed in the chemostat pH2.5, although tetrathionate is an inhibitory substrate at some pH values. Yield, apparent maintenance and ee page eater For both substrates, true growth yield, Yo (g dry wt per g atom Fe or g mole KS 96 oxidized) was determined from the experimental data and enabled calculation 24 of the Yarp (g dry wt per mole ATP available from each substrate) and the probable ° + ° : . . . ATP requirement for NAD reduction during iron oxidation.

      Tepper, K. P.; Näveke, R.; Lehrstuhl für Mikrobiologie, Technische Universitat Braunschweig Braunschweig, FRG (1977)
      The influence of direct current and of current with changing the poles two times per sec at intensities of 0,2...15 mA and at tensions of 12...170 Von leaching of pyrite dispersed in quartzite in percolators with Thiobacillus ferrooxidans was studied. The solution of iron was accelerated by bacteria without current and by current without bacteria, but in combination the acceleration did not exceed the sum of both single effects. The results suggest that there is no direct elec- trophysiological influence of current on bacteria under conditions of our experiments. At present we try to utilize indirect electrochemical effects of current on bacterial leaching of chalcopyrite.

      Brierley, J. A.; Le Roux, N. W.; Department of Biology, New Mexico Institute of Mining and Technology Socorro, NM 87801, USA; Department of Industry, Warren Spring Laboratory Stevenage, Hertfordshire SG] 2BX, England (1977-07)
      A rod-shaped microbe, isolated from an Icelandic thermal spring grows well at 50° C and oxidises metal sulphides e.g., pyrite (FeS,), pentlandite ((NiFe) SQ) and chalcopyrite (CuFeS,). Initial isolation on a modified ferrous iron medium at pH 3.6 and 60° C indicated that the bacteria were capable of oxidising ferrous iron but that growth was poor. For good growth on sulphide minerals, yeast extract is a requirement. This paper reports on the oxidation of soluble ferrous iron and pyrite by this microbe. The microbe grows slowly at 30° C using ferrous iron but does not grow on pyrite; growth on the latter substrate begins at 40° C. Growth on iron occurs at 50° C, but not at 55° C; growth on pyrite is present at 55° C but not at 60° C. The microbe grows using sulphur as an energy source. The thermophile also grows when yeast extract provides the only apparent energy source. Pyrite-grown cells were used for manometric experiments. Using ferrous iron, the oxygen uptake was non-linear, decreasing with time; the rate increased with increasing pH from 1.3 to 3.2 and also increasing ferrous iron concentration to 8] mM Fe(II). The rate then remained the same at 111mM Fe(II). Using pyrite, the oxygen uptake was linear, the rate being a maximum at pH 2.6. Oxidation of pyrite was slight at pH 1.1 and 3.5. The greatest rate of pyrite oxidation occurred with 100 g c pyrite, the largest concentration tested. Oxygen uptake during the manometric tests with ferrous iron was not greatly affected by the absence of yeast extract; pyrite oxidation was slightly greater without yeast extract. The relevance of the activity of this microbe to biohydrometallurgy is discussed.

      Brock, Thomas D.; Department of Bacteriology, University of Wisconsin, Madison, WI 53706 U.S.A. (1977-07)
      Acidophilic bacteria of the genera Thiobacillus and Sulfolobus reduce ferric iron when growing on elemental sulfur as an energy source. This process can be demonstrated aerobically in T. thiooxidans and S, acidocaldarius, but only anaerobically in T. ferrooxidans, since under aerobic conditions this latter organism reoxidizes the ferrous iron it produces as a result of ferric reduction. Since oxidation of sulfide minerals probably proceeds through the intermediary accumulation of elemental sulfur, the bacterial coupling of elemental’sulfur and ferric iron may be important in the overall process of sulfide mineral oxidation, especially when 0, is limiting. Considerations of the environment and ecology of leach dumps suggest that 0, is often limiting, and anaerobic conditions may develop. Thus, the bacterial catalysis of the elemental sulfur-ferric iron reaction may play a major role in the effective operation of a leaching process.
    • Foreword - Contents - List of authors

      Schwartz, Wilhelm; Kula, M.-R. (1977)
      FOREWORD It is a long way from theoretical considerations and laboratory experiments to technical applications, especially with the economic uncertainties lurking in the background. Since the publication in 1964 by Silverman and Ehrlich, containing a survey of what had until then been tried in microbiological formation and degradation of minerals by thiobacilli and other microorganisms, technical applications of thiobacilli have been developed on a broad scale only for sulphidic copper ores and for uranium ores along the lines of the primary program for low-grade ores, heap leaching and in-situ leaching of exhausted mines. During the last 10 years, new topics of leaching research have been discussed or are already developing: batch leaching with suspensions of ore concentrates; combined methods of chemical and microbial, and of electrolytic and microbial leaching; experiments to separate heavy-metal mixtures by microbial methods; leaching at high temperatures within the biological range or at high hydrostatic pressures; uranium leaching of phosphorites; leaching of industrial wastes and residues; application of acid-producing microorganisms other than thiobacilli; problems of freshwater shortage and its circumvention by the use of brackish water or sea water and adapted Thiobacillus strains; synergistic effects of thiobacilli and other microorganisms during the leaching process; treatment of mining waste waters with thiobacilli; relations between metal precipitation and solubilisation in the formation of sedimentary ore beds and in leaching processes. A quite different approach to leaching processes is the use of complexing or chelating metabolites produced by heterotrophic microorganisms. This had already been tried successfully by Perkins and Novielli (1962) with manganese oxides; it is again being discussed on a broader basis. Most of these topics were discussed or at least mentioned at our Conference, but some were not yet touched upon. As far as the technical and economic situation, the discussions on waste problems, environmental contamination, and shortages of raw materials are concerned, we may assume that biotechnical leaching has not yet reached its high point, but will continue to be extended and developed. | hope that the Conference will stimulate interest in this field of biotechnical research and also discussions between microbiologists and engineers of the mining and metallurgical industries on problems where interdisciplinary contacts may be profitable to both sides. | acknowledge with pleasure the support of this Conference by Dr. M.-R. Kula, Scientific Director of the GBF. | am especially grateful to the authors, and to Dr. Walsdorff of the GBF for their cooperation in preparing this volume. Braunschweig, July 1977 W. Schwartz Research and development at the GBF (Institute for Biotechnological Research Ltd.) is centered on the apparently unlimited biosynthetic capabilities of living cells: microorganisms as well as cell cultures. This potential is exploited for the production of organic chemicals, pharmaceuticals and materials such as single cell protein and specific enzymes. This also involves engineering, scale-up and development of new methods. Through the Leaching Conference, held here on 23-26 March 1977, the GBF has for the first time supported a scientific discipline that, although belonging to Biotechnology, is at present not being worked on at this Institute. However, the scientists at the GBF are aware that in recent years the leaching of low-grade ores has made fast progress in some areas. Thus we welcomed Prof. Schwartz’s suggestion to invite specialists in this field to a conference, in order to obtain a comprehensive and up-to-date survey of the field and to learn of problems and progress. We thank the participants of this Conference for their successful effort. It was decided to publish the papers of the Conference in the GBF Monograph Series, since, according to experts on modern leaching, there exists neither a comprehensive book nor a symposium volume that reflects the state of the art. This was clearly a correct decision, judging by the numerous requests already received. The present volume not only makes available a collection of the complete papers to the participants of the Conference, but is also intended to let other research groups in industry and academia gain insight into the area of microbial leaching, and to stimulate work in this field, especially in our country, where efforts are made to intensify work in this direction. Braunschweig-Stöckheim, July 1977 M.-R. Kula

      Torma, A. E.; Itzkovitch, I. J.; Department of Metallurgical and Materials Engineering, New Mexico Institute of Mining and Technology, Socorro, New Mexico 87801, USA and Department of Metallurgy, Ontario Research Foundation, Mississauga, Ontario, Canada, L5K 1B3. (1977)
      Microbiological leaching as applied to uranium ores involves the metabolic oxidation by Thiobacillus ferrooxidans of associated pyrite to sulfuric acid and ferric sulfate. The sulfuric acid and ferric sulfate generated are effective leachants for common uranium minerals. Dissolved uranium can be recovered from the aqueous leach solutions by solvent extraction or ion exchange techniques. The present study explored the effects of potential solvent extraction reagents for uranium on pyrite oxidation ability of Thiobacillus ferrooxidans. For the solvents studied it was found that in all cases the dissolved organic matter decreased the pyrite oxidation activity of the bacteria, the surface tensionof the leach solutions and the oxygen saturation concentration. The following order of inhibition was established for the solvents and modifiers studied: aliquat 336 > nonyl phenol > kerosene 140 > alamine 310 > adogen 381 > di (2-ethylhexyl) phosphoric acid > adogen 365 > tri-n-butyl phosphate > ¥sodecanol > alamine 308 > alamine 336 > alamine 304. Suggestions to integrate solvent extraction and bacterial leaching for uranium by treating the recirculating raffinate are described.

      Kiel, Hildegard; Institut für Mikrobiologie der T.U. Braunschweig Arbeitsgruppe Prof.Dr.W,.Schwartz (1977)
      Leaching of carbonate and silicate ores with Thiobacilli under laboratory conditions has not been very successful. We have tested the leaching effects of organic acids and of acid producing heterotrophic microorganisms upon a low-grade copper ore, containing carbonates and silicates, from Timna, Israel. Good results were obtained with citric, lactic, glycollic, and tartaric acids. Citric acid, 0.05 M, for instance, solubilized 82% Cu. By lowering the pH with sulphuric acid to pH 2, lactic, eitric, and glycollic acids yielded almost 100% Cu. Citric acid producing strains of Aspergillus niger, growing in surface cultures on a Ssucrose fermentation medium, leached more than 80% Cu. Sulphite liquor may be used with fair results as a fermentation medium for A. niger. Anaerobic leaching experiments with whey, containing homofermentative lactobacilli, yielded 83% Cu.

      Khalid, A. M.; Ralph, B. J.; School of Biological Technology, University of New South Wales, Kensington, New South Wales, Australia (1977)
      The availability of high-grade specimens of sphalerite, wurtzite and marmatite prompted a comparative study of the leaching rates of these minerals in the presence of Thiobacillus ferrooxidans, T. thiooxidans and T. thioparus. In this preliminary study, samples of the finely-ground minerals, of equivalent surface area, were subjected to attack by populations of equal magnitude of each of the three bacterial species in shake flasks at 30 C. The microorganisms were acclimatised to the particular substrates. The results indicate that (1) Wurtzite is much more slowly degraded than marmatite or sphalerite by all three organisms. (ii) Marmatite is leached more rapidly by T. ferrooxidans and T, thiooxidans than sphalerite, in both the presence and absence of soluble iron. (iii) Iron-free synthetic zinc sulphide is leached more rapidly by T. thiooxidans than by T. ferrooxidans or T. thioparus. The hexagonal crystalline structure of zinc sulphide in wurtzite appears to be more recalcitrant to microbial degradation than the cubical form of sphalerite, and the substitution of iron for some of the zinc in the marmatitic form of zinc sulphide appears to greatly facilitate biodegradation.

      Coombes, A. J.; Lepp, N. W.; Phipps, D. A.; Department of Biology and Department of Chemistry, Liverpool Polytechnic, Byrom St., Liverpool, L3 3AF, U.K. (1977)
      When roots of bean plants (Phaseolus vulgaris L.) grown in solution culture, were supplied with increasing levels of copper, increases in the quantities of the positively charged forms of copper, calcium and magnesium which were leached from the foliage of such plants were observed. However, subsequent analysis of the results indicated the presence of a large interactive component in the observed variations, and incorporation of this factor showed that the observed increases in leaching were not significantly related to nutrient copper levels. Correlation between foliar copper levels and the quantity of all leached cations was obtained and the quantities of the individual elements leached were also highly correlated. This is good indication of the implication of a single factor as a causal agent for increased cation leaching. The leaching of anionic forms of the above elements was more variable. Anionic forms of all 3 elements were detected and the quantities leached showed similar trends, but due to large variability, only the effect of the treatments on anionic magnesium was significant. The number of samples containing anions was significantly reduced by an increased root copper supply.

      Tsuchiya, H. M.; Department of Chemical Engineering and Materials Science, and Department of Microbiology University of Minnesota Minneapolis, Minnesota 55455 (1977)
      Results of leaching tests on a mixed copper and nickel sulfide concentrate from the Duluth Gabbro complex are reported here. The relative efficacies of pure cultures of Thiobacillus ferrooxidans and mixed cultures of T. ferrooxidans and Beijerinckia lacticogenes are compared as possible leaching aids

      Agate, A. D.; Deshpande, H. A.; Microbiology Department, Abasaheb Garware College Poona, INDIA (1977)
      When low grade manganiferous material (-65 mesh) obtained from Andhra Pradesh and Goa, India was subjected to leaching experiments , an efficiency of 70 to 85 % resulted,using an Arthrobacter species. The inoculum could be best cultivated in enriched soil extract - manganese medium and percolating columns with filtration were used for a period of 14 days. The optimum conditions for maximum leaching were worked out and the operation was found to be economically feasible on a large scale, when the adsorbed manganese was quantitatively precipitated with lime, Under the same conditions, other heterotrophic bacteria belonging to the genera Bacillus and Pseudomonas, isolated from fresh water pipeline deposits alongwith the predominant Arthrobacter species tested above, took upto 90 days to carry out the leaching of manganese,

      Karavaiko, G. I.; Pirovarova, T. A.; Institute of Microbiology, USSR Academy of Sciences, Moscow (1977-07)
      The mechanism of transport sulphur both outside and inside the cells was studied. Macroroentgen structural analysis and electronicmicroscopic researches showed that the membrane structures of thiobacilli carry out not only the oxidation function, but the transport function as well, which consists in the extraction of the formed sulphur from cell. This mechanism of sulphur deposition develops ac-— cording to the exocytosis type. The transport of elemental sulphur inside the cell involves the surface membrane structures (vesicles), while oxidation of the sulphur to sulphuric acid takes place on the outer surface of the cytoplasmic membrane. The vesicles are supposed also to participate in the primary dissolution of elemental sulphur at the site of contact of the cells with the mineral. The study of bacterial oxidation of sulphide minerals has shown the electrochemical nature of microbiological oxidation of sulphide minerals, which takes place at the level of its electronic structure. Pyrite with hole conductivity (with the cation deficit in composition) is oxidized by means of Thiobacillus ferrooxidans not only much more intensively, but also continuously as compared to pyrite with electron conductivity. Thiobacilli play a leading role in the oxidation of reduced sulphur compounds under natural conditions. The mechanism of this process however have not been studied sufficiently well so far. The main purpose of this work was to study the mechanism of sulphur transport, when sulphur was deposited or oxidized by thiobacilli, by means of cytological and cytochemical techniques. We believed that the mechanism,of sulphur transport either from, or into, the cell must be closely related to the submicroscopic organization of thiobacilli