Presentation on theme: "Bioleaching/Biocorrosion Metals/Biomining"— Presentation transcript:
1 Bioleaching/Biocorrosion Metals/Biomining Lisa SmithMarian CumminsDeborah Mc Auliffe
2 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.
3 Challenge for mining companies Service-no long term impact on environmentIncreasing interest in microbial approaches for recovery of base and precious metals
4 Biomining Use of microorganisms Ores of high quality rapidly being depletedEnvironmentally friendly alternative
5 Biomining Naturally existing microorganisms leach and oxidate BioleachingBiooxidation
6 Bioleaching Biooxidation Extraction of metals with the use of microorganismsBiooxidationMicroorganisms make metal ready for extraction
7 General Properties Chemolithotrophic - “ rock eating” Autotrophic Acidophilic ( acid loving)Use oxygen as the preferred electron acceptor
8 Specific Microorganisms Most common:Thiobacillus ferrooxidansThiobacillus thiooxidans
9 Thiobacillus ferrooxidans Rod shapedRelatively quick growingGram negativeStrictly aerobicAerobic conditions uses Fe2+ or reduced S (S2-) as electron acceptorAnoxic conditions use Fe3+ as electron acceptorMod. Thermophilic, temperatures of degree C and pH of 2.0
10 Thiobacillus thioxidans Very similar to T. ferrooxidansCan’t oxidise Fe3+
11 The Process 2 Methods- Direct and indirect Direct- enzymatic attack and occurs at the cell membraneIndirect- 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.
12 Copper Process 25% Copper production is recovered by biomining MS + 2O MSO4Metal sulphide is insoluble and metal sulphate is usually water solubleCu ore contains CuS and CuFeS2T. ferrooxidans brings about both direct and indirect oxidation of CuS via the generation of (Fe3+) ferric iron from (Fe2+) ferrous sulphate
13 Cu is recovered by solvent extraction or by using scrap iron where the iron replaces the Cu CuSO4 + Fe Cu + FeSO4
14 Other Application of Biomining GoldDue to depletions by the 1980’sDependent on lower grade oreGold is encased in the sulphide mineralsT. ferrooxidansFairview mine in S. AfricaRecovery rate of 70% to 95%
15 Cont’d Phosphates industry 2nd largest agriculture chemical 5.5 million tons/ year in the USTraditional method was burning at high temperatures (solid phosphorus) or with H2 SO4(phosphoric acid and gypsum)Pseudomonas cepacia E37 and Erwinia herbicolaGlucose---- gluconic and 2 ketogluconic acidEnvironmentally friendly as no Hs SO4 required and it occurs at room temperature.
16 Economics of Biomining Case Studies+Economics of Biomining
17 Microbes ‘TO TACKLE MINE WASTE’ Scientists are using microbes to clean up the problem of corrosive acid pollution left over as mining wasteSome of the microbes being used were found in America, Wales and the Caribbean islandBy discovering microbes which can survive in this environment, will help address serious environmental hazards at abandoned mines and soil heaps
19 Chile Biomining Program Worlds first biggest producer of CopperIn 1971 copper mines were nationalizedBut in 1990 Chile returned to democracyStarted in 1990 with tons for the year 2000This Figure was superseded in 1995 and production exceeded 5m tons / late 1990’s
20 Economic Study of the Canadian Biotechnology Canadian environmental & industrial biotechnology firmsMicroorganisms in applications such as bioremediation leaching, energy productionCanadian Stakeholders with; U.S, European, Japanese environmental regulators
21 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 metalEarly prospectors in Europe used certain weeds as indicator plants that signaled the presence of metal ore
22 Remediation Response to human health effects Response to environmental effectsRedevelopment
23 BioremediationDestroys or renders harmless various contaminants using microbial activityBioremediation of metal-contaminated soilSoil FlushingSoil WashingPhytostabilizationPhytoremediation
24 Phytostabilization Immobilization of a contaminant in soil through Absorption & AccumulationAdsorptionPrecipitationAlso use of plant & plant root to prevent contaminant migrationSoil is then farmed to improve growth and reduce mobility and toxicity of contaminant
26 Phytoremediation Use of plants to remove contaminants from soil Certain plant species-metal hyperaccumulatorsextract metals, concentrate them in their leavesPrevent recontamination-plants harvested
27 Leaves accumulate metals and are harvested Roots take up metals from contaminated soil and transport to the stem, leaves
28 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
29 Traditional extraction causes environmental problems and degradation, biomining offers an environmentally friendly alternative!!!!!!