Bioleaching/Biocorrosion Metals/Biomining

1. Bioleaching/Biocorrosion Metals/Biomining Lisa Smith Marian Cummins Deborah 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 environment • Increasing interest in microbial approaches for recovery of base and precious metals

4. Biomining • Use of microorganisms • Ores of high quality rapidly being depleted • Environmentally friendly alternative

5. Biomining • Naturally existing microorganisms leach and oxidate • Bioleaching • Biooxidation

6. Bioleaching • Extraction of metals with the use of microorganisms • Biooxidation • Microorganisms make metal ready for extraction

7. General Properties • Chemolithotrophic - “ rock eating” • Autotrophic • Acidophilic ( acid loving) • Use oxygen as the preferred electron acceptor

8. Most common: Thiobacillus ferrooxidans Thiobacillus thiooxidans Specific Microorganisms

9. 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 ferrooxidans

10. Thiobacillus thioxidans • Very similar to T. ferrooxidans • Can’t oxidise Fe3+

11. The 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.

12. Copper 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

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 • 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%

15. Cont’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.

16. 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 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

18. Industrial Biotechnology Biomining • Commercial Capabilities • Underpinning Existing Capabilities • Emerging Capabilities • Institutional Capabilities • Knowledge / Skills

19. 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 target @2.5m tons for the year 2000 • This Figure was superseded in 1995 and production exceeded 5m tons / late 1990’s

20. 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

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 metal • Early 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 effects • Redevelopment

23. Bioremediation • Destroys or renders harmless various contaminants using microbial activity • Bioremediation of metal-contaminated soil • Soil Flushing • Soil Washing • Phytostabilization • Phytoremediation

24. 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

26. 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

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!!!!!!