Collections in this community

Recent Submissions

  • UTILIZATION OF METAL BEARING INDUSTRIAL WASTE MATERIALS BY MICROBIOLOGICAL LEACHING

    Szolnoki, J.; Hungarian Academy of Sciences, Laboratory for Geochemical Research, Budapest, Hungary (1977)
    Chemoautotrophic sulphur-bacteria were isolated from mine drainage waters /Th. ferrooxidans/, which are able to oxidize the ferrous-iron into ferric-iron in biocatalytic way in a heavy acidic medium. These bacteria were adapted to high metal especially to high iron, aluminium and sodium concentrations. The ferric-sulphate produced by the bacterial oxidation is a strong leaching agent. The optimal parameters were determined under which the acidic ferric-sulphate bearing solution is favourable from the point of view of practical utilization. During the biological oxidation process a part of dissolved iron precipitated in form of ferric-hydroxide which is also utilizable material.
  • METAL EXTRACTION FROM INDUSTRIAL WASTE WITH THIOBACILLI

    Ebner, H. G.; Universitat Dortmund, Technische Chemie B, Dortmund, FRG (1977)
    During the last two decades a lot of research has been carried out on microbiological leaching of low-grade ores. Since the UNCTAD conferences on raw materials have shown that besides the energy resources also the metallic resources of the world are limeted and what is even worse not renewable the idea of recycling has become more and more attractive. This means that waste raterials will have to be processed to regain valuable metals. Bacterial leaching of inorganic industrial waste or tailings can be regarded at least under two beneficial aspects: 1. toxic substances from the wastes will be removee thus the cost for their disposal can be lowered and the environment will be protected, 2. valuable metals can be gained from the wastes. This part is probably even more economic because of the rising prices for raw-materials in the near future.
  • CHEMICAL AND MICROBIALLY-ASSISTED LEACHING OF ATHABASCA OIL SANDS COKE

    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.
  • SOME ASPECTS OF THE MECHANISMS OF SOLUBILIZATION AND INSOLUBILIZATION OF URANIUM FROM GRANITES BY HETEROTROPHIC MICROORGANISMS

    Berthelin, J.; Belgy, G.; Magne, R.; Centre de Pédologie biologique du C.N.R.S. B.P. 5 - 54500 Vandoeuvre-les-Nancy, France (*)now R. MAGNE is prospecting engineer at the C.E.A. (1977)
    In batch cultures, complex microflora from granitic mountain mass, promoted solubilization of U in presence of amino-acids as sole source of carbon and energy. Solubilized U amounted up to 100 mg U/1 in presence of microorganisms but was less than 35 mg U/1 in absence of microorganisms (sterile controls). Microflora involved contained different strains of bacteria, Pseudomonas fluorescens, P. putida, Achromobacter, Bacterium, Gaffkya or Peptococcus. In experimental design of factorial type with semi-continuous flow devices, the activity of different microflora from known forest soil was compared. Microflora specifically withstanding partial sterilization and comprising different Pseudomonas Bacillus licheniformis, B. cereus, B. lentus, B. polymyxa, B. megaterium, plus one or two unidentified yeasts promoted significantly microbial solubilization of U by synthesis of complexing agents with high complexing capacity for Al and Fe, but lower complexing capacity for U. But anaerobic microflora induced by waterlogging was much less active as compared by solubilization with control microflora. From the comparison of the different strains involved, Pseudomonas appeared to be the most active. In presence of an "organo-urany1" solution, obtained by adding glutamic or aspartic acids to uranium ore in sterile conditions, different bacteria originating from samples of granitic mountains mass could grow : Achromobacter, Brevibacterium, Acinetobacter, Gaffkya or Peptococcus, Pseudomonas, showing that such microorganisms could contribute to U deposition by metabolising organo-uranium compounds. Leaching and ecological implications of such processes are discussed.
  • LEACHING OF MANGANESE ORES USING ARTHROBACTER SPECIES

    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,
  • LAUGUNG VON KUPFERKARBONAT-UND KUPFERSILIKAT-ERZEN MIT HETEROTROPHEN MIKROORGANISMEN

    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.
  • 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
  • EXPERIMENTS ON COMBINED ELECTRO AND BACTERIAL LEACHING (Short Communication)

    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.
  • INFLUENCE OF URANIUM EXTRACTANTS ON PYRITE OXIDATION ABILITY OF Thiobacillus ferrooxidans

    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.
  • THE LEACHING BEHAVIOUR OF VARIOUS ZINC SULPHIDE MINERALS WITH THREE THIOBACILLUS SPECIES

    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.
  • PILOT-PLANT BACTERIAL FILM OXIDATION (BACFOX PROCESS) OF RECYCLED ACIDIFIED URANIUM PLANT FERROUS SULPHATE LEACH SOLUTION

    Livesey-Goldblatt, E.; Tunley, T. H.; Nagy, I. F. (1977)
    Laboratory tests have established that a rapid oxidation of an acidified solution of ferrous sulphate to ferric can be achieved by passage of an air saturated solution over a film of Thiobacillus ferro-oxidans, Pilot-plant units of various types were constructed and operated to assess their oxidising efficiency using ferrous solutions ranging from 3,5 to 12 gram Fe II/litre and 3,1 to 10,5 gram H280,/litre. The best results were obtained with a plastic corrugated packing media to support the film of bacteria submerged in the iron sulphate solution thoroughly air saturated by forced aeration. The maximum specific rate of oxidation of Fe II to Fe III achieved was 7,5 gram per square metre of bacterial surface per hour.
  • ELECTRO-LEACHING OF CHALCOPYRITE

    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.
  • THE NATURE OF THE PASSIVATION FILM ON COVELLITE EXPOSED TO OXYGEN

    Golding, R. M.; Harris, B.; Ralph, B. J.; Rickard, P. A. D.; Vanselow, D. G.; School of Chemistry, School of Metallurgy, School of Biological Technology, University of New South Wales, Kensington, N.S.W., Australia (1977)
    Evidence has been presented by Corrans et al. [1] that in the synthetic leaching of synthetic covellite, a direct mechanism operates by preventing the accumulation of a protective layer of sulphur and by the depolarisation of a cathodic reaction. The process of covellite passivation has been further studied, using sensitive methods for measurement of the consumption of oxygen and acid, and for the production of cupric and sulphate ions. The results indicate that passivation arises from the accumulation of approximately 30 micromole of elemental sulphur per square metre of covellite surface. The oxygen consumed during depassivation by various strains of Thiobacillus ferrooxidans supported this conclusion. Assuming an even distribution of sulphur over the surface, the passivation film has been calculated to be one or two atoms thick.
  • CHALCOCITE OXIDATION BY CONCENTRATED CELL SUSPENSIONS OF THIOBACILLUS FERROOXIDANS

    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.
  • STUDIES IN THE BACTERIAL LEACHING OF NICKEL ORES

    Bosecker, K.; Bundesanstalt für Geowissenschaften und Rohstoffe Hannover (1977)
    The applicability of bacterial leach technique in the extraction of nickel from naturally occurring nickel minerals and from sulfide and silicate nickel ores has been investigated. The nickel minerals gerstorffite, niccolite, and pentlandite could be leached with Thiobacillus thiooxidans whereas silicate nickel ores seemed to be inefficient to leaching with Thiobacillus. Within 100 days less than 1 % of the nickel was extracted from silicate ores. Sulfide nickel ores have been leached with Th. ferrooxidans and Th. thiooxidans. In air-lift-percolators within 100 days 17 % of the nickel were extracted using pure cultures of Th. thiooxidans, but only 5.6 % were recovered after leaching with Th. ferrooxidans. Within 30 days 38 %, 66 %,and 70 % of the nickel were extracted from ground material (Harzburger Gabbro) by submerged fermentation in shaking Erlenmeyer flasks adding pure cultures of Th. thiooxidans, Th. ferrooxidans and a mixed culture of both strains, respectively, to the culture medium.
  • BACTERIAL LEACHING OF A LOW-GRADE CHALCOPYRITE ORE WITH DIFFERENT LIXIVIANTS

    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.
  • UN PROBLEME POSE PAR DES PALEOBACTERIES : LA CRISTALLISATION DE LA GALENE DES DEPOTS STRATIFORMES EST-ELLE MICROBIOLOGIOUE ?

    Devigne, Jean-Pierre; Laboratoire de Sédimentologie, Batiment 504 Université Paris-Sud, 91405 Orsay Cedex, France (1977)
    SEM study of divers rocks (sandstones, clays, marls, dolomites. etc...) mineralised by galena has resulted jn the discovery of fossil bacteria within the galena crystals. Two significant facts result trom these studies : the first concerns the clearly developped and exclusive association of galena and certain paleobacteria and their absence within surrounding sediment. Current studies confirm that this mutual attraction is not an exception; it is already established that certain species of aerobic, anaerobic, autotroohic and heterotrophic bacteria are not adversly affected by leadrich environments. Our research has enabled us to follow the absorption of this cation within individual germs of Sarcina flava. Certain results obtained in vitro suggest that this metal may be utilised by organisms during their microbio-synthetic activities prior to its rejection in the form of black, cryptocrystalline sulphur, PbS. and in other cases, either as carbonate, as an oxide, or an organo-metallic complex. The second significant fact concerns the imprisoning of paleobacteria within the galena crystals irrespective of their age and mmposition or environment of denosition? By varying the focus of the SEM it was possible to penetrate several microns jnto the crystals. Invariably, this has lead to the observation that the crystals of galena have envelopped a multitude of bacteria. The absence of all traces of physial imperfections (fractures, etc..) which could have facilited their postcrystallisation emplacement seems to indicate not only that the bacteria in question have lived in this environment and are themselves enriched in Pb but also that the cristallisation of the galena is an early 108 J.-P. Devigne diagenetic phenomena. These observations pose the following questions to which we have attempted to reply : should one consider this crystallisation as a simple chemical or physical reaction, or should we consider that the paleobacteria are the instigators of this process, at least during the initial phases of crystal germ formation ? In this latter case the imprisoning of the lead-associated paleomicrobes within the crystal structure is only the result of progressive crystal qrowth.
  • THE PRACTICAL ASPECTS OF LABORATORY LEACHING STUDIES

    Bruynesteyn, A.; Duncan, D. W.; B. C. Research 3650 Wesbrook Mall Vancouver, B. C., Canada V6S 2L2 Telex: 04-507748 (1977)
    To construct and operate leach dumps under optimum conditions, it is necessary to study the leaching characteristics of leach ores. Knowing how a particular Jeach ore will behave under commercial conditions will make it possible to design both the physical and operational parameters of a leach dump so that the ore will yield a maximum amount of metal in minimum time. The paper discusses a two phase investigation program consisting of a preliminary low cost investigation to determine a mineral's general amenability to the leaching process and a series of large column tests which can be used to provide the necessary practical data for commercial applications, examples of which are discussed.
  • THE COMPOSITION, MORPHOLOGY AND ACTION UPON CHALCOPYRITE OF AUTOTROPHS RECOVERED FROM FUMAROLES

    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
  • THE METAL-TOLERANT ALGAE Hormidium fluitans (GAY) HEERING FROM ACID MINE DRAINAGE WATERS IN NORTHERN AUSTRALIA AND PAPUA-NEW GUINEA

    Madgwick, J. C.; Ralph, B. J.; School of Biological Technology, University of New South Wales, Kensington, N.S.W., Australia (1977)
    The filamentous green alga Hormidium fluitans (Gay) Heering grows extremely luxuriantly in turbulent outflows of mine drainage waters in Northern Territory, Australia, and on Bougainville Island, Papua-New Guinea. The drainage waters contain between 30 and 700 p.p.m. copper and have a pH range 3.2 - 5.3. The metal-concentrating ability of the naturally-occurring alga has been examined in respect of 25 elements; high concentration ratios have been noted for the elements, Ag, Al, Fe, Mo, Ti and V. In the case of copper, histochemical examination shows a possible binding of the metal in a cell-wall layer. An alkali-soluble fraction of the dried cells prepared from field samples of the alga, had a very high affinity for copper (11.8% of dry weight). This fraction made up about 1.5% of the cell polymers. The alga has been artificially cultivated in a number of modes, but grows best in vigorously sparged submerged culture on artificial mine water, in the presence of ore lumps. Under most laboratory conditions, motile and unicellular forms of the algae occur. It has been shown recently that culture filtrate from the algal growth stimulates the rate of iron oxidation and of growth of some Thiobacillus ferrooxidans strains, and enhances the rate of copper release from chalcopyrite ores.

View more