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!!!!!!