[en] The purpose of this research project is to develop efficient leaching processes for the extraction of uranium from low-grade ores and for the removal of long half-life radionuclides (radium and thorium) from the leach residue in order to produce innocuous tailings. The present investigation is the first part of a three-year project. It provides kinetic information not heretofore available for uranium leaching by hydrochloric and sulfuric acid solutions and preliminary data for the removal of radionuclides from the leach residues by KCl-solutions. This study has demonstrated that uranium extractions as high as almost 100% can be realized with either HCl or H₂SO₄ leach solutions. Initial radium concentration of 245 pCi g^-1 originally in the ore was reduced to 70 and 23 pCi g^-1 in the final tailings of hydrochloric and sulfuric acid leachings

[en] The purpose of this research project is to demonstrate the possibility of development of efficient leaching processes for the extraction of uranium from low-grade ores and for the removal of long half-life radionuclides (radium-226) from the leach residues in order to produce radiochemically innocuous tailings. The present investigation is the second part of a three-year project. It provides kinetic information not heretofore available for uranium leaching by hydrochloric and sulfuric acid solutions and initial data for the extraction of ²²⁶Ra from the leach residues by brine solutions. Preliminary data on the removal of ²²⁶Ra from neutralized tailing effluents and leach solutions with commercially available solid organic ion exchangers are discussed. A generalized mathematical form has been developed for the initial rate of uranium extraction as a function of the leaching parameters using experimental data and a linear regression computation technique. 31 references, 5 figures, 8 tables

[en] The Great Lakes area sediments are contaminated with varying amounts of heavy metals and polychlorinated organic matter. With respect to the bioremediation of metallic contents of these sediments, it was shown that a number of microorganisms exist which can effectively solubilize heavy metals. The basic reaction mechanisms of bioleaching processes were discussed and the effects of semiconductor character of the sulfide substrate explained. A special emphasis was made to comment on INEL's bioremediation capability. 37 refs

[en] Microorganisms were evaluated for use in recovery of uranium under conditions of in-situ solution mining. The cultures tested were Thiobacillus ferrooxidans, the faculative-thermophilic TH3 strain, and two Sulfolobus species. Growth of the organisms occurred in the presence of 0.34 to 5.0 mM uranyl ion with higher concentrations being inhibitory. Uranium ore from the Anaconda Minerals Co. Jackpile mine was not readily leachable by microorganisms. To support bacterial activity the ore was supplemented with pyrite or ferrous iron. The ore possessed some toxic properties. T. ferrooxidans was able to assist in leaching of uranium from the ore at a hydrostatic pressure of 10.3 MPa

[en] The theme of the International Biohydrometallurgy Symposium (IBS) held in Jackson Hole, Wyoming, August 22--25, 1993, is ''Biohydrometallurgy: An Industry Matures''. This is a developing technology which made important contributions to the minerals industry. The IBS-93 is focused on recent advances achieved in fundamental and applied aspects of research and development of biotechnologies applied to mineral domains. The papers presented at the Symposium are grouped together in two volumes, which are the following: this volume contains papers selected for publication which are predominantly dealing with subjects related to laboratory and industrial scale bioleaching of base and precious metals, biocorrosion phenomena, diverse bioreduction processes and electrochemical reactions. Individual papers have been processed separately for inclusion in the appropriate data bases

[en] The theme of the International Biohydrometallurgy Symposium held in Jackson Hole, Wyoming, August 22-25, 1993, is ''Biohydrometallurgy: An Industry Matures.'' This is a developing technology which made important contributions to the minerals industry. Biohydrometallurgical technology was first introduced into the copper industry and subsequently to the uranium industry for the production of metal values from low-grade mineral resources. Currently, biotechnology has advanced a step further. It is now commercially applied for the treatment of high-grade refractory gold ores in aerated stirred reactors to liberate precious metals for cyanidation. In addition, the industrial applications of biotechnology involve bioenhanced tertiary oil recovery processes, which contribute to an increase in oil production from previously exhausted wells. Furthermore, many bioremediation technologies are being developed for the removal of toxic heavy metals and radionuclides from contaminated soils and aqueous mining and industrial effluents. This volume contains papers selected for publication which are predominantly dealing with subjects related to laboratory and industrial scale bioleaching of base and precious metals, biocorrosion phenomena, diverse bioreduction processes and electrochemical reactions. Individual papers have been processed separately for inclusion in the appropriate data bases

[en] It is well known that seasonal changes affect the solubility of barium-radium sulfate [(Ba, Ra)SO₄]. In early spring higher Ra-226 concentrations are in solution than by the end of the fall season. The present study has developed an intensified leach technique for the assessment of the influence of microorganisms on the stability of (Ba, Ra)SO₄ contained in synthetic and actual uranium mill-tailings. In this process, a period of 10.5 simulated weathering years is equivalent to three weeks of wet and two weeks of dry treatment of tailings. The results obtained indicate that in the presence of microorganisms, Thiobacillus ferrooxidans, the Ra-226 concentration was decreased as a function of time compared to that concentration obtained in the sterile experiments. The decrease in the Ra-226 concentration was found to be the consequence of sulfuric acid and ferric sulfate production from pyrite by bacterial action. The excess of sulfate in solution resulted in a decrease in the solubility of (Ba, Ra)SO₄. In the sterile experiments, the pyrite oxidation was considerably slower, as indicated by pH measurements, and fewer sulfates were produced. Therefore, the solubility of (Ba, Ra)SO₄ could proceed towards the dissociation resulting in higher Ra-226 concentrations in solutions

[en] The present preliminary study has demonstrated that the kinetics of uranium extraction from a low-grade ore will be improved in the presence of hydrogen peroxide at moderate temperature using conventional tank leaching technique. Yield improvements of 6% and higher reaction rates were observed in the presence of H/sub 2/O/sub 2/. 30 refs

[en] Uranium extractions above 82 per cent have been realized from the ore by sulfuric acid leaching at 30⁰C without addition of any oxidant other than air. Increasing the temperature to 70⁰C resulted in a complete extraction of uranium in the presence and absence of chemical oxidants. In the temperature range of 30-50⁰C, the hydrogen peroxide resulted in yield improvements of 5 to 6 per cent relative to the effect of air. At 30⁰C the hydrogen peroxide was found to be a more efficient oxidant than sodium chlorate. An equation, similar to the Langmuir adsorption form, has been developed and its applicability in the description of uranium rate phenomena demonstrated. The process of uranium extraction resulted in two apparent activation energies, which were for the lower temperature range ΔE = 245 J/mol and for the higher temperature range ΔE = 642 J/mol. These relatively low ΔE values suggest that the extraction of uranium may be diffusion controlled and more than one reaction mechanism is associated with the process. (orig.)

[en] Application of biotechnological principles in the mineral processing, especially in hydrometallurgy, has created new opportunities and challenges for these industries. During the 1950's and 60's, the mining wastes and unused complex mineral resources have been successfully treated in bacterial assisted heap and dump leaching processes for copper and uranium. The interest in bio-leaching processes is the consequence of economic advantages associated with these techniques. For example, copper can be produced from mining wastes for about 1/3 to 1/2 of the costs of copper production by the conventional smelting process from high-grade sulfide concentrates. The economic viability of bio leaching technology lead to its world wide acceptance by the extractive industries. During 1970's this technology grew into a more structured discipline called 'bio hydrometallurgy'. Currently, bio leaching techniques are ready to be used, in addition to copper and uranium, for the extraction of cobalt, nickel, zinc, precious metals and for the desulfurization of high-sulfur content pyritic coals. As a developing technology, the microbiological leaching of the less common and rare metals has yet to reach commercial maturity. However, the research in this area is very active. In addition, in a foreseeable future the biotechnological methods may be applied also for the treatment of high-grade ores and mineral concentrates using adapted native and/or genetically engineered microorganisms. (author)