bioleaching : bioleaching Smratee malode
Guided by , M.Sc [BT] III SEM
Ms.Sujatha.R contents : contents Introduction
References Leaching : Leaching Minerals and its mining : Minerals and its mining Chuquicamata, chile : Chuquicamata, chile Site of the largest and the deepest open pit copper mines in the world. Carrara, italy : Carrara, italy Marble quarry coquina : coquina Quarry wyoming : wyoming Coal strip mine Impacts of mining : Impacts of mining Northern minnesota (acid mine drainage) : Northern minnesota (acid mine drainage) Located between Northern Shore of Lake Superior and the Boundary Waters Canoe Area Wilderness. philippine : philippine Geita gold mine philippines : philippines Healthy rice field in Oriental Mindoro; Left-Barren rice field philippines : philippines Impact of Marcopper Corporation tailings Bioleaching : Bioleaching history : history 1OOO B.C.
1990s Principle of bioleaching : Principle of bioleaching Slide 19: Low pH 2Fe3+ + H2O & e- A. & L. ferrooxidans
forming ATP by ferrous iron oxidation 2 Fe2+ + 0.5O2 + 2H+ Fe2+ Fe3+ Reduced e- source Oxidised e- source Oxidised
e- acceptor Reduced
e- acceptor e- Precursor Temp. energy storage H+ H+ Generally O2 H2O e- ADP ATP H+ H+ Energy releasing
redox reaction: Slide 20: These microorganisms actually gain energy by breaking down minerals into their constituent elements.
Bioleaching by microorganisms takes place owing to destruction of a crystal lattice of minerals, composing solid. Microorganisms take elements necessary for feeding and construction of a cell from a crystal lattice.
This shakes of a lattice are causes the destruction of a mineral. Direct and indirect mechanisms of bioleaching : Direct and indirect mechanisms of bioleaching Electrochemical mechanism : Electrochemical mechanism REACTIONS INVOLVED : REACTIONS INVOLVED Generation of ferric ions in indirect bioleaching
4FeSO4 + O2 + 2H2SO4 2Fe2(SO4)3 + 2H2O.
Cu2S + 2Fe2(SO4)3 2CuSO4 +2FeSO4 +S0
Direct bioleaching invoves:
CuS +2O2 T.Ferroxidans CuSO4 Biofilm formation : Biofilm formation Experiment conducted by Schaeffer, Holbert And Umbreit in 1962 to demonstrate the nature of attachment of bacteria to the crystals. : Experiment conducted by Schaeffer, Holbert And Umbreit in 1962 to demonstrate the nature of attachment of bacteria to the crystals. Surface of crystal prior to exposure to bacteria Surface of crystal after exposure to bacteria. Comparison of crystal with high and low innoculum of bacteria. : Comparison of crystal with high and low innoculum of bacteria. Surface of another crystal of sulfur after incubation with low innoculum of Thiobacillus Thiooxidans. Surface of sulfur crystal after incubation with high innoculum of Thiobacillus Thiooxidans. Organisms involved : Organisms involved Slide 28: Mesophiles -(Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans and species of Ferroplasma)
Moderately thermophilic bacteria-(Sulfobacillus and Acidithiobacillus cladus)
Extremophiles- ( Acidianusbrierleyi, Sulfolobus metallicus and Metallosphaera sedula.) Organisms involved can be conveniently classified into: Scanning electron micrograph : Scanning electron micrograph Cork screw shaped Leptospirllium and mesophilic rod shaped bacteria embedded in biofilm on ore particle. Scanning electron micrograph of moderately thermopile bacteria : Scanning electron micrograph of moderately thermopile bacteria Bacterial cells are 2-5 micrometer long and 0.5-1 micrometer in diameter Scanning electron micrograph of Acidianus brierly; an extremophilic thermophiles : Growing on molybdenite Scanning electron micrograph of Acidianus brierly; an extremophilic thermophiles common Features of organisms involved : common Features of organisms involved Single-celled organisms.
Derive carbon dio-oxide, oxygen from atmosphere.
Requires acidic pH. thiobacillus : thiobacillus Thiobacillus ferrooxidans : Thiobacillus ferrooxidans Identifying Characteristics : Identifying Characteristics Strictly aerobic.
Cells are 0.3 to1- 3mm in size.
Best growth at 25-35° C
Able to oxidize sulfide, elemental S, thiosulfate, and polythionate. Cont… : Cont… Obligate autotrophs (cannot grow with organic carbon as an electron and carbon source).
A few species grow on organic compounds.
Grow best at neutral pH.
Some spp. are able to live in highly acidic environments.
Responsible for acid mine drainage due to the metabolism of coal spoil piles causing the production of sulfuric acid.
Some spp. are able to utilize iron as an energy source.
Some spp. are able to carry out denitrification. Yellow and red zones below a hot spring in yellowstone national park,. : Yellow and red zones below a hot spring in yellowstone national park,. Where large populations of thermal-tolerant thiobacilli have grown by oxidizing reduced sulfur and iron in the water. Engineering of Bioleaching Process : Engineering of Bioleaching Process Dump leaching on a slope : Dump leaching on a slope Dump ore leaching : Dump ore leaching Slide 41: In –situ bioleaching HEAP LEACHING : HEAP LEACHING FACTORS EFFECTING BIOMINING: : FACTORS EFFECTING BIOMINING: Success of biomining and efficiency in recovery of minerals depends on various factors some of which are discussed below.
(a) Choice of Bacteria - This is the most important factor that determines the success of bioleaching. Suitable bacteria that can survive at high temperatures, acid concentrations, high concentrations of heavy metals, remaining active under such circumstances, are to be selected to ensure successful bioleaching.
(b) Crystal Lattice Energy - This determines the mechanical stability and degree of solubility of the sulfides. The sulfide ores with lower crystal lattice energy have higher solubility, hence, are easily extracted into solution by the action of bacteria.
(c) Surface Area - Rate of oxidation by the bacteria depends on the particle size of the ore. The rate increases with reduction in size of the ore and vice-versa. Cont… : Cont… (d)Ore Composition – Composition of ore such as concentration of sulfides, amount of mineral present, and the extent of contamination, has direct effect on the rate of bio-oxidation being selected. The rate of biooxidation is reduced significantly if the temperature is above or below the optimum temperature.
(e) Acidity - Biooxidation requires a pH of 2.5-3 for maximum results. The rate of biooxidation decreases significantly if the pH is not in this range since the activity of acidophilic bacteria is reduced.
(f) Temperature - The bacteria used in biomining are either mesophilic or thermophilic. Optimum temperature is required for biooxidation to proceed at a fast rate. Optimum temperature range for a given bacteria is between 25-35° C depending on the type of ore Slide 46: (g) Aeration - The bacteria used in biomining are aerobic thus require an abundant supply of oxygen for survival and growth. Oxygen can be provided by aerators and pipes. Mechanical agitation is also an effective method to provide continuous air supply uniformly and also to mix the contents.
(h) Solid-liquid Ratio - The ratio of ore/sulfide to the leach solution (water + acid solution + bacteria inoculum) should be maintained at optimum level to ensure that biooxidation proceeds at maximum speed. The leach solution containing leached minerals should be removed periodically and replaced with new solution.
(i) Surfactants - Adding small amounts of surfactants like Tween 20 to the leaching process increases the rate of biooxidation of minerals from sulfide ores. The surfactants decrease the surface tension of the leach solution, thus, wetting the ore and resulting in increased bacterial contact which ultimately increases the rate of biooxidation. Extraction of copper, gold and uranium : Extraction of copper, gold and uranium Copper leaching : Copper leaching Copper dump bioleach operation atBingham Canyon mine near salt lake city, Utah. : Copper dump bioleach operation atBingham Canyon mine near salt lake city, Utah. Reactions involved in copper bioleaching : Reactions involved in copper bioleaching 4FeSO4 + O2 + 2H2SO4 2Fe2(SO4)3 + 2H2O.
CuFeS2 (chalcopyrite)+2Fe2(SO4)3 CuSO4 +5FeSO4 + 2S0
FeS2 (pyrite) + Fe2(SO4)3 3FeSO4 +2S0
CuO (tenorite) + 2H2SO4 CuSO4 + H2O
CuS (covellite) + 2O2 CuSO4 URANIUM MINING : URANIUM MINING According to the World Nuclear Association, the largest national share of nuclear reserve was
Australia (1,243,000 tones, 23%)
Kazakhstan (817,000 t, 15%)
Russia (546,000 t, 10%)
South Africa (435,000 t, 8%)
Canada (423,000 t, 8%)
USA (342,000 t, 6%)
Brazil (278,000 t, 5%)
Namibia (275,000 t, 5%)
Niger (274,000 t, 5%)
Ukraine (200,000 t, 4%)
Jordan (112,000 t, 2%). Cont…… : Cont…… With current technology, there are three main techniques in use for uranium mining. These are open pit mining, underground mining, and in situ leach mining. In open pit mining, the land above the material is blasted and dug away to reveal the ore body. After they have found the fuel deposit, it will be blasted, excavated and removed with dump trucks. Underground mining is carried with access tunnels, and drilling and blasting. In situ leach mining involves drilling boreholes down into an ore body, pumping a leaching fluid into the ore and then pumping the resulting solution to the surface to extract the uranium. The leaching fluid is sometimes a combination of acids or sometimes alkaline solution. The type of the solution used depends on the type of the ore body. Slide 54: UO2 + 2H2SO4 +Fe2(SO4)3 UO2(SO4)3 +2FeSO4+ 4H+.
sss Gold mining : Gold mining Biooxidation (Pretreatment process)
Chemical leaching by cyanide solution.
Cyanidation Process: 2Au +4CN- +O2 2Au(CN)2
4Au+8S2O32-+O2+2H2O 4Au(S2O3)3-+4OH- Slide 56: Stacking microbially-inoculated, sulfidic-refractory gold ore at newmount gold quarry mine in nevada. Slide 57: Stacking acid-conditioned secondary copper ore on engineered leach pad at teckcominco’s quebrada blanca mine in chile Slide 58: Plastic-lined pads on the right are ready for loading the ore for biooxidation with a heap under biooxidation on the left. Slide 59: Aerated stirred tank bioleach plant.
Courtesy of Kasese company, Uganda Slide 60: Blowers external to the heap provide air that is distributed to the
Perforated plastic pipes laid beneath the heap. Bioleaching in processing of Non-metallics : Bioleaching in processing of Non-metallics Desulphurization of coal : Desulphurization of coal Cont… : Cont… Micro-organisms degrading DBTs:
Rhodococcus sp. (Gray et al., 1996)
Pseudomonas (Kilbane, 1989)
Brevibacterium sp. (McEldowney et al., 1993)
The inorganic sulphur in coal can be oxidized by chemolithotrophs :
Linked to the oxidation of reduced iron, T. ferrooxidans generates energy by the direct oxidation of iron (II) sulphide to iron (I) sulphate
2FeS2 + 7O2 + 2H2O 2FeSO4 + 2H2SO4
Microbial action can also directly convert elemental sulphur to sulphuric acid.
2S + 3O2 + 2H2O 2H2SO4 Kerogen liberation from oil shales : Kerogen liberation from oil shales Bioleaching in alkaline and neutral environment : Bioleaching in alkaline and neutral environment Obligate chemolithotrophs: Halothiobacillus neapolitanus
Phototrophs:Thiocystis Cont... : Cont... Bioleaching from electronic scraps : Bioleaching from electronic scraps Organism involved :
Thermophillic and acidophillic bacteria which includes Sulfobacillus thermosulfooxidans and an unidentified acidophillic heterotroph isolated from local environment. ULTRASONOBIOLEACHINg(SOUND- ASSISTED BIOLEACHING) : ULTRASONOBIOLEACHINg(SOUND- ASSISTED BIOLEACHING) Ultrasonication : Ultrasonication The irradiation of a liquid sample with ultrasonic (>20 kHz) waves resulting in agitation. Sound waves propagate into the liquid media result in alternating high-pressure (compression) and low-pressure (rarefaction) cycles. During rarefaction, high-intensity sonic waves create small vacuum bubbles or voids in the liquid, which then collapse violently (cavitation) during compression, creating very high local temperatures. The future of Bioleaching : The future of Bioleaching Isolate new bacterial strains from extreme environments, such as mine-drainage sites, hot springs, and waste sites, and use these to seed bioleaching processes.
Improve isolates by conventional mutation and selection or by genetic engineering. One possibility would be to introduce arsenic resistance into some bioleaching organisms, which could then be used in gold bioleaching.
Heterotrophic leaching is a solution for wastes and ores of high pH (5.5) where many of the acidophiles would not grow. Fungi likeTrichoderma horzianum have been shown to solubilize MnO2, Fe2O3, Zn, and calcium phosphate minerals.
The population dynamics within the bioleaching dumps and the relative importance of various organisms and mechanisms needs to be understood Conclusion : Conclusion The mining industry is constantly seeking new and more practical and environmental friendly technologies. Therefore biogeotechnology occupies an increasingly important place among the available mining technologies. Today it is no longer a promising technology but the actual alternative for solving various mining and geological problems. References : References Analytical applications of ultrasound By M. D. Luque de Castro, F. Priego Capote;137-140
Microbial Processing of Metal Sulfides By Edgardo R. Donati, Wolfgang Sand;127-132
Textbook Of Environmental Biotechnology PB Pradipta Kumar Mohapatra I. K. International 395-411
Environmental Biotechnology: Basic Concepts and Applications Textbook I.K .International Pvt. Ltd Indu Shekhar Thakur 359-366
Environmental Biotechnology: Fundamentals And Applications Pradeep PariharAgrobios (india)473-483
Microbial Biotechnology - Fundamentals Of Applied MicrobiologyAlexander N. Glazer, Hiroshi Nikaido Cambridge University PressSecond edition 609-610
Journal ( 1962)Department of Bacteriology, Rutgers, The State University, New Brunswick, New Jersey
Biol-CSES 4684 - Thiobacillus.mhtss
http://biomine.skelleftea.se/ html/ BioMine/ The%20overlay%20technique... 2.6Mb http://environnement.u-psud.fr/ %21Biogeotechnology%20maxime.ppt 4.9Mb http://www.biotechnology.uwc.ac.za/ teaching/ BTY227/ Microbial%20appl... 601k
Nova Biotechnologica VII-I (2007).pdf Department of Biotechnology, Institute of Geotechnics of the Slovak Academy of Sciences, Watsonova 45, Košice, SK-043 53, Slovak Republic
Photomicrograph courtesy ofNewmont Mining Corporation
Photos courtesy of compañía quebrada blanca
Photo courtesy of Brierley Consultancy LLC.