bioleaching/biocorrosion metals/biomining
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Bioleaching/Biocorrosion Metals/Biomining. Lisa Smith Marian Cummins Deborah Mc Auliffe. - PowerPoint PPT PresentationTRANSCRIPT
Bioleaching/Biocorrosion Bioleaching/Biocorrosion Metals/BiominingMetals/Biomining
Lisa Smith
Marian Cummins
Deborah Mc Auliffe
• Metal Contamination of soil environments and the assessment of its potential risk to terrestrial environments and human health is one of the most challenging tasks confronting scientists today.
• Challenge for mining companies– Service-no long term impact on environment
• Increasing interest in microbial approaches for recovery of base and precious metals
BiominingBiomining
• Use of microorganisms
– Ores of high quality rapidly being depleted
– Environmentally friendly alternative
BiominingBiomining
• Naturally existing microorganisms leach and oxidate
1. Bioleaching
2. Biooxidation
• Bioleaching
– Extraction of metals with the use of microorganisms
• Biooxidation
– Microorganisms make metal ready for extraction
General PropertiesGeneral Properties
• Chemolithotrophic - “ rock eating”
• Autotrophic
• Acidophilic ( acid loving)
• Use oxygen as the preferred electron acceptor
Specific Microorganisms Specific Microorganisms
Most common:
• Thiobacillus ferrooxidans
• Thiobacillus thiooxidans
Thiobacillus ferrooxidansThiobacillus ferrooxidans
• Rod shaped• Relatively quick growing• Gram negative• Strictly aerobic• Aerobic conditions uses Fe2+ or reduced S (S2-) as
electron acceptor• Anoxic conditions use Fe3+ as electron acceptor• Mod. Thermophilic, temperatures of 20-35 degree C and
pH of 2.0
Thiobacillus thioxidansThiobacillus thioxidans
• Very similar to T. ferrooxidans
• Can’t oxidise Fe3+
The ProcessThe Process
• 2 Methods- Direct and indirect
• Direct- enzymatic attack and occurs at the cell membrane
• Indirect- bacteria produce Fe3+ ( ferric iron) by oxidizing Fe2+ (ferrous iron)
• Fe3+ is a powerful oxidizing agent that reacts with the metals and so produces Fe2+ in a continuous cycle.
Copper ProcessCopper Process
• 25% Copper production is recovered by biomining
• MS + 2O2 MSO4
• Metal sulphide is insoluble and metal sulphate is usually water soluble
• Cu ore contains CuS and CuFeS2
• T. ferrooxidans brings about both direct and indirect oxidation of CuS via the generation of (Fe3+) ferric iron from (Fe2+) ferrous sulphate
• Cu is recovered by solvent extraction or by using scrap iron where the iron replaces the Cu
• CuSO4 + Fe Cu + FeSO4
Other Application of BiominingOther Application of Biomining
• Gold • Due to depletions by the 1980’s • Dependent on lower grade ore• Gold is encased in the sulphide minerals• T. ferrooxidans• Fairview mine in S. Africa• Recovery rate of 70% to 95%
Cont’dCont’d
• Phosphates industry • 2nd largest agriculture chemical • 5.5 million tons/ year in the US• Traditional method was burning at high temperatures
(solid phosphorus) or with H2 SO4(phosphoric acid and gypsum)
• Pseudomonas cepacia E37 and Erwinia herbicola• Glucose---- gluconic and 2 ketogluconic acid
• Environmentally friendly as no Hs SO4 required and it occurs at room temperature.
Case Studies
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Economics of Biomining
Microbes ‘TO TACKLE MINE Microbes ‘TO TACKLE MINE WASTE’WASTE’
• Scientists are using microbes to clean up the problem of corrosive acid pollution left over as mining waste
• Some of the microbes being used were found in America, Wales and the Caribbean island
• By discovering microbes which can survive in this environment, will help address serious environmental hazards at abandoned mines and soil heaps
Industrial Biotechnology BiominingIndustrial Biotechnology Biomining
• Commercial Capabilities
• Underpinning Existing Capabilities
• Emerging Capabilities
• Institutional Capabilities
• Knowledge / Skills
Chile Biomining ProgramChile Biomining Program
• Worlds first biggest producer of Copper
• In 1971 copper mines were nationalized• But in 1990 Chile returned to democracy
• Started in 1990 with target @2.5m tons for the year 2000
• This Figure was superseded in 1995 and production exceeded 5m tons / late 1990’s
Economic Study of the Canadian Economic Study of the Canadian BiotechnologyBiotechnology
• Canadian environmental & industrial biotechnology firms
• Microorganisms in applications such as bioremediation leaching, energy production
• Canadian Stakeholders with; U.S, European, Japanese environmental regulators
Biomining Biomining “There’s GOLD in them thar’ Plants!”“There’s GOLD in them thar’ Plants!”
• Gold rush miners might have been better off using plants to find gold rather than panning streams for precious metal
• Early prospectors in Europe used certain weeds as indicator plants that signaled the presence of metal ore
RemediationRemediation
• Response to human health effects
• Response to environmental effects
• Redevelopment
BioremediationBioremediation
• Destroys or renders harmless various contaminants using microbial activity
• Bioremediation of metal-contaminated soil– Soil Flushing– Soil Washing– Phytostabilization– Phytoremediation
PhytostabilizationPhytostabilization
• Immobilization of a contaminant in soil through – Absorption & Accumulation– Adsorption – Precipitation
• Also use of plant & plant root to prevent contaminant migration
• Soil is then farmed to improve growth and reduce mobility and toxicity of contaminant
PhytoremediationPhytoremediation
• Use of plants to remove contaminants from soil
• Certain plant species-metal hyperaccumulators– extract metals, concentrate them in their
leaves
• Prevent recontamination-plants harvested
• Leaves accumulate metals and are harvested
• Roots take up metals from contaminated soil and transport to the stem, leaves
BiominingBiomining+Carried out insitu+Less energy input+No toxic/noxious gases produced+No noise or dust problems+Process is self generating+Large or small scale operations+Wide variety of metals (Cu, Ag, Pb, Au, Zn)+Work on low grade ores-Slow process
Traditional extraction causes environmental problems and degradation, biomining offers an environmentally friendly alternative!!!!!!