Corale L. Brierley

Bioremediation of metal‐contaminated surface and groundwaters

Abstract Microorganisms immobilize, mobilize, or transform metals by extracellular precipitation reactions, intracellular accumulation, oxidation and reduction reactions, methylation and demethylation, and extracellular binding and complexation. Nearly all of these microbe/metal interactions occur within the wetlands approach to acid mine drainage treatment, a process that is rapidly gaining support as a low‐maintenance, cost‐effective approach to solving an important environmental problem. Several proprietary processes, which employ nonliving microorganisms that are immobilized in polymer matrixes, are entering the water treatment market. These processes take advantage of negatively charged functional groups on cell walls and exopolymers of microorganisms that bind cationic metals. These biosorbents effectively remove low concentrations (<1 to about 20 mg/L) of heavy metal cations in the presence of high concentrations of alkaline earth metals (Ca2+ and Mg2+) and organic contaminants to levels lower than...

Progress in bioleaching: part B: applications of microbial processes by the minerals industries

This review presents developments and applications in bioleaching and mineral biooxidation since publication of a previous mini review in 2003 (Olson et al. Appl Microbiol Biotechnol 63:249–257, 2003). There have been discoveries of newly identified acidophilic microorganisms that have unique characteristics for effective bioleaching of sulfidic ores and concentrates. Progress has been made in understanding and developing bioleaching of copper from primary copper sulfide minerals, chalcopyrite, covellite, and enargite. These developments point to low oxidation–reduction potential in concert with thermophilic bacteria and archaea as a potential key to the leaching of these minerals. On the commercial front, heap bioleaching of nickel has been commissioned, and the mineral biooxidation pretreatment of sulfidic-refractory gold concentrates is increasingly used on a global scale to enhance precious metal recovery. New and larger stirred-tank reactors have been constructed since the 2003 review article. One biooxidation–heap process for pretreatment of sulfidic-refractory gold ores was also commercialized. A novel reductive approach to bioleaching nickel laterite minerals has been proposed.

Molybdenite-leaching: Use of a high-temperature microbe

Abstract A high-temperature, chemoautotrophic microorganism was studied to establish its capability for leaching molybdenite and to ascertain its response to soluble molybdenum. Experimental results confirm that the organism can tolerate 2000 ppm hexavalent molybdenum and can grow when the concentration of soluble molybdenum is 750 ppm. A molybdenite concentrate is leached at a maximum rate of 6.6 mg Mo solubilised/1./day; this rate is maximised by supplementing the medium with 0.02% yeast extract and 1% iron(II) sulphate. Batch reactor-leaching suppresses the rate of molybdenum solubilisation; the original leaching rate can be re-established by periodic replacement of the suspending medium. Some organic compounds enhance the leaching rate, but combinations of these compounds are not additive. Sulphur is inhibitory to molybdenite leaching; pyrite suppresses molybdenum solubilisation if the concentration of pyrite exceeds 50% of the total solid substrate. Molybdenite ore is successfully leached. Molybdenite waste and tailings contain acid-consuming gangue and lime, respectively, which raise the pH well above optimum for biogenic leaching. Hence, biogenic leaching of waste and tailings is not successful by the technique employed herein. Direct observations of the high-temperature microorganism on molybdenite fines illustrate colonial growth and developmental characteristics in a microbial—mineral interaction. The organism responds to hexavalent molybdenum by reducing this metal to the pentavalent state in aerobic and nitrogen gas atmospheres.

MICROBIAL LEACHING OF COPPER AT AMBIENT AND ELEVATED TEMPERATURES

This report compares the leaching ability of Thiobacillus ferrooxidans, a microbe commonly associated with copper leaching operations at ambient temperature, and a high-temperature Sulfolobus- like microbe, an organism recently determined to be associated with metals extraction at 60°C. The mineral substrates used for leaching included mine waste and concentrate from the Kennecott Copper Corporation, Chino Mines Division, NM, ore from the Phelps-Dodge Corporation, Tyrone Division, AZ, and concentrate from the Phelps-Dodge Corporation, Ajo Division, AZ. The bio-leaching experiments were run in stationary batch reactors. Four nutrient conditions were evaluated for their effect on bio-leaching of copper minerals at room temperature and 60°C: 1) basic leach solution only; 2) basic leach solution supplemented with 0.02% yeast extract; 3) basic leach solution with 36 mM ferrous iron; and 4) a combination of basic leach solution, 0.02% yeast extract and 36 mM ferrous iron. Soluble copper concentration was monitored after 30 and 60-days leaching. The yeast extract did not greatly affect copper leaching by either T. ferrooxidans or the Sulfolobus- like microbe except with the Ajo concentrate which was leached more effectively. The addition of ferrous iron enhanced the bio-leaching of copper. Apparent increased bio-leaching at 60°C was attributed to temperature affect rather than enhanced bio-activity by the thermophile except with the Ajo concentrate, indicating greater ability by the Sulfolobus- like microbe for extracting copper from a mineral substrate rich in chalcopyrite.

Anaerobic Reduction of Molybdenum by Sulfolobus Species

Summary The acidothermophilic Archaebacteria, Sulfolobus acidocaldarius and S. brierleyi, oxidized elemental sulfur anaerobically producing sulfuric acid by using Mo (VI) as an apparent electron acceptor. Molybdenum reduction resulted in the formation of a blue color which was intensified in the presence of aluminum at concentrations of 20–50 mM. Molybdenum was not reduced when S. brierleyi was grown anaerobically on yeast extract as an energy source, suggesting that the organic substrate was utilized in a fermentative metabolism mode.

Preliminary observations on the effect of heavy metals from mining and smelting on nitrogen-fixing bacteria in some British soils

Nitrogen fixation by free-living non-symbiotic bacteria has been qualitatively estimated in several surface soils and mine wastes from mineralised areas in Derbyshire and Cornwall, using a technique based on acetylene reduction. Fresh samples contaminated with varying amounts of one or more of the metals lead, zinc, cadmium and copper, together with appropriate controls, showed no ability to reduce acetylene, indicating an absence of nitrogen fixation. Addition of activeAzotobacter chroococcum resulted in acetylene reduction in the majority but not all of the samples. The effects of varying concentrations of lead, zinc, cadmium and copper on the growth ofAzotobacter chroococcum andBeijerinckia lactogenes were tested in laboratory culture.