Presentation on theme: "Bioleaching/Biocorrosion Metals/Biomining Lisa Smith Marian Cummins Deborah Mc Auliffe."— Presentation transcript:
Bioleaching/Biocorrosion Metals/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
Biomining Use of microorganisms –Ores of high quality rapidly being depleted –Environmentally friendly alternative
Biomining 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 Properties Chemolithotrophic - “ rock eating” Autotrophic Acidophilic ( acid loving) Use oxygen as the preferred electron acceptor
Specific Microorganisms Most common: Thiobacillus ferrooxidans Thiobacillus thiooxidans
Thiobacillus ferrooxidans Rod shaped Relatively quick growing Gram negative Strictly aerobic Aerobic conditions uses Fe 2+ or reduced S (S 2- ) as electron acceptor Anoxic conditions use Fe 3+ as electron acceptor Mod. Thermophilic, temperatures of degree C and pH of 2.0
Thiobacillus thioxidans Very similar to T. ferrooxidans Can’t oxidise Fe 3+
The Process 2 Methods- Direct and indirect Direct- enzymatic attack and occurs at the cell membrane Indirect- bacteria produce Fe 3+ ( ferric iron) by oxidizing Fe 2+ (ferrous iron) Fe 3+ is a powerful oxidizing agent that reacts with the metals and so produces Fe 2+ in a continuous cycle.
Copper Process 25% Copper production is recovered by biomining MS + 2O 2 MSO 4 Metal sulphide is insoluble and metal sulphate is usually water soluble Cu ore contains CuS and CuFeS 2 T. ferrooxidans brings about both direct and indirect oxidation of CuS via the generation of (Fe 3+ ) ferric iron from (Fe2+) ferrous sulphate
Cu is recovered by solvent extraction or by using scrap iron where the iron replaces the Cu CuSO 4 + Fe Cu + FeSO 4
Other 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’d Phosphates industry 2 nd largest agriculture chemical 5.5 million tons/ year in the US Traditional method was burning at high temperatures (solid phosphorus) or with H 2 SO 4 (phosphoric acid and gypsum) Pseudomonas cepacia E37 and Erwinia herbicola Glucose---- gluconic and 2 ketogluconic acid Environmentally friendly as no H s SO 4 required and it occurs at room temperature.
Case Studies + Economics of Biomining
Microbes ‘TO TACKLE MINE 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
Chile 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 tons for the year 2000 This Figure was superseded in 1995 and production exceeded 5m tons / late 1990’s
Economic Study of the Canadian Biotechnology Canadian environmental & industrial biotechnology firms Microorganisms in applications such as bioremediation leaching, energy production Canadian Stakeholders with; U.S, European, Japanese environmental regulators
Biomining “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
Remediation Response to human health effects Response to environmental effects Redevelopment
Bioremediation Destroys or renders harmless various contaminants using microbial activity Bioremediation of metal-contaminated soil –Soil Flushing –Soil Washing –Phytostabilization –Phytoremediation
Phytostabilization 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
Phytoremediation 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
Biomining +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!!!!!!