Systems: V Microorganisms in the Natural Environment Human metabolism relies on C6 H12 O6 O2 CO2 1. 2. 3. 4. Oxidation state of carbon in.
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Systems: V Microorganisms in the Natural Environment Human metabolism relies on C6 H12 O6 O2 CO2 1. 2. 3. 4. Oxidation state of carbon in glucose is zero Oxidation state of carbon in CO2 is +4 Energy is obtained with glucose as an electron donor The energy source also serves as the carbon sources In natural environments a variety of other oxidation/reduction reactions take place altering the solubility of minerals: 1. Uranium 2. acid mine tailings 3. Bio mining At the end of this module we will see how these systems might be harnessed For fuel cells. C6 Typical redox “ladder” (order of reduction) O2 H2O NO3NO2N2 Mn4+ Mn2+ Fe3+ Fe2+ Fe2+ SO42SO S2O3 C2H4O4 (fumarate) CH4 - CO2 methanogenesis Depth of sediment (lack of oxygen) Patricia A. Maurice and Lesley A. Warren,Introduction to Geomicrobioloyg: Microbial Interactions with Minerals CMS Workshop Lectures, Vol 14 Iron oxides are very reactive surfaces and serve as an electron source/donor For a large variety of environmental electron transfer reactions. The most common electron acceptors in the environment are (in order of activity) O2> NO3->MnO2,s>Fe(OH)3s>SO42->CO2 Most reactions occur by Organic + electron acceptor oxidized organic + reduced electron acceptor Some types of interesting organic “eating” “bugs” Psuedomonas denitrificans 3 2 CH3OH NO NO NO N 2 Electron donor methanol C3 H6 O3 Mn 4 Mn Electron donor lactate CH3COO Mn 4 Mn 2 CO2 U (VI ) NO3 Geobactermetallireducens 2 CO2 Degrade explosives: RDX Geobactermetallireducens pyruvate 2 Fe( III ) 2 H 2O acetate HCO3 2 Fe( II ) 3H acetate 8Fe( III ) 4 H 20 2 HCO3 8Fe( II ) 9 H Can uses acetate, Ethanol, propionate, butyrate Valerate, pyruvate, propanol And toluene The Impact of Fe(III)-reducing acterium on uraniu mobility, Biogeochemistry 2006 125-150, Michael J. Wilkins, Francis R. Livens, David j. Vaughan, Jonathan R. Lloyd. Ferrihydrite is present in less quantity in rock-forming minerals but is the most Bioavailable. – fine grained with surface area of several hunded m2/g Present as coatings on other materials (including clays). Thermodynamically unstable (ripens to hematite or goethtie). Enzymatic reduction of hematite/goethite phases Hansel, C.M., Benner, Nico P. and Fendorf, S., 2004, Geochim. Cosmochim Acta 68, 3217-3229: Structural constrainst of ferric hydroxoides on dissimilatory iron Reduction and the fate of Fe(II) Appears to be altered by the deposition of Fe(II) coating – passification occurs. Natural minerals easier to reduce due to greater crystalline disorder and defects Between the natural and syntheic s oxides. The Impact of Fe(III)-reducing acterium on uraniu mobility, Biogeochemistry 2006 125-150, Michael J. Wilkins, Francis R. Livens, David j. Vaughan, Jonathan R. Lloyd. Oxidized uranium is soluble UVIO22Reduced uranium is insoluble UIVO2 Therefore of interest in containing uranium contamination in Groundwater. Principle microorganisms D. Vulgaris G. Sulfurreducens Shewanella putrefacians Remainder of the review discusses in site injection of microorganisms lactate Fe( III ) CO2 Fe( II ) Shewanellaputrifaciens Shewanellaoneidensis lactate U (VI ) U ( IV ) H2 SO42 S 2 Disulfovibrio desulfuricans methanogenicbacteria 2Corg 2 H2 O CO2 CH4 Surface structure effects on direct reduction of iron oxides by Shewanella oneidensis, Geochimica et Cosmochimica Acta, 67, 23, 4489, Andrew L. Neal, Kevin M. Rosso, Gill G. Geesey, Yuri A. Gorby, Brenda J. Little. Shewanell Oneidensis is a bacteria that terminates its respiration by donating electrons to Fe3+. How it does this is of general interest to environmental chemists, geochemists, and for possible application to biofuel cell development. Shewanella on hematite Developing biofilm of Shewanella oneidensis MR-1. The three-dimensional structure of biofilms is revealed by live imaging using confocal microscopy. Red color indicates cellular DNA and green color indicates extracellular polysaccharides, which play a structural role in the biofilm and may actively and passively sequester metals and radionuclides from the environment. Each unit represents 40 microns. http://www.eurekalert.org/multimedia/pub/589.php http://www.sysbio.org/sysbio/biofilms.stm Acid mine reactions Pyrite reactions 2 FeS 2 7O2 2 H 2 O 2 Fe 2 4 SO42 4 H 4 Fe 2 O2 4 H 4 Fe 3 2 H 2 O RDS 4 Fe 3 12 H 2 O 4 Fe OH 3 12 H ferrihydrite FeS 2 14 Fe 3 8 H 2 O 15Fe 2 2 SO42 16 H 3FeS 2 8O2 20 H 2 O 14 Fe 3 13Fe 2 6SO42 4 Fe OH 3 28 H ferrihydrite 6H2 SO4 Thiobcillus ferrooxidans Acid loving creatures found at acid mine waste sites Oxidize iron and sulfur and alter the solubility of the minerals facilitating Formation of soluble metals (helps mining) and formation of sulfates (increases Acid discharge) Fe 2 21 O2 2 H Fe 3 H2 O 2 FeS2 2 H2 O 7O2 2 FeSO4 2 H2 SO4 Acid Mine Waste http://technology.infomine.com/enviromine/ard/Microorganisms/roleof.htm 3 Fe 2 21 O2 2 H Fe H2 O thiobacillus ferrooxidans MS 2 Fe 3 M 2 2 Fe 2 S Catalytic cycle results in mobile or soluble metal M ions Cu, Zn Pb, Cd Electron transfer kinetics iron mineral reductions 1. 2. 3. 4. Reactivity of Edges Effect of Size (role of clays) Structural implications of reduction Calculated and measured e.t. Surface Complexation of Ferrous Iron and Carbonate on Ferrihydrite and the Mobilization of Arsenic, Appelo et al EST 2002 36 3096 Arsenic water poisoning major issue in Bangladesh where irrigation dropped Water table resulting in one of the following 1. Dissolution of iron oxides containing As 2. Reduction of sorbed As and desorption of arsenite 3. Oxidation of arsenic containing pyrite. 4. Author’s proposal: Displacement of sorbed As by carbonates Behaviour of Fe-oxides relevant to cntaminant uptake in the environment, Chemical Gegology, 190, 2002, 321-337, Stipp et al Iron-oxides with their high surface area andstrong affinity, sequester cations Such as the transitin metals and radionucleides in proportions that are storngly A funciton of oslution composition and pH. Also strong adsorbers of anionic complexes Persson, P.; Nilsson, N.; Sjoberg, S., 1996, Strucuture and obnding of orthophosphate ions at the iron oxideaqueous surface, J. Colloic InterfaceSci, 177, 263-275 Randall, S. R.,Sherman, D. M., Ragnarsdottir, K. V., 2001, Sorption of As(V) ongreeen rust (Fe4(II)Fe2(III)(OH)12SO403H2O) and lepidocrocite (gamma-FeOOH): surface complexes from EXAFS spectroscopy,Geochim Cosmochim Acta 65, 1015-1023 CrO42- Ding, M., B.H.W. S. de JOng, S. J. Roosendall, Bredenberg, A. Geochemica Cosmochimica Acta 65, 2000, 1209-1219 XPS studies on the electronic structure of fonbing between oslid and solutes: adsorption of arsenate, chromate, phsophate, Pb2+and Zn2_ on amorphous black ferric oxyhydroxide. Mix iron oxides with contaminated sources (water, ash from incinerators etc), Precipitate and bind as an oxidie. Use as a reactive barrier. Behaviour of Fe-oxides relevant to cntaminant uptake in the environment, Chemical Gegology, 190, 2002, 321-337, Stipp et al Many contaminants (ash) dissolve and are precipitated with iron to prevent Motion. Irreversible sorption implies localization within the changing crystal as opposed to surface complexation – depends on rate of transformation 1. Adsorb to surface (precipitation) 2. Transformation to a more stable phase 3. Dissolve again or exsolve incorporated components Figure 2 shows that only 40% of material is released – suggesting transformation Should depend on mineral morphology particle size Figure 8 shows that ferrihydrite minerals “age”into larger sized hematite and goethite Iron redox cycling in the with iron oxides Reduction of POlyhalogenated Methanes by Surface-BoundFe(II) in Aqueous Suspensions of Iron Oxides, Env. Sci. Tech. 36, 2002 36 1734-1741 K. Pecher et al. Iron cycling known to control reductive transformaiton of organic and inorganic Pollutants in soils and groundwater In nearly all cases: Fe(II)-surface is more reactive than Fe(II) aqueous Study use of Fe(II)-iron oxide on reduction of polyhalogenated methanes Highest reactivity found at pH consistent with precipitation of hydrous oxides Color of species was blue-green suggests mixed valence iron phases as the acti Possible green rust, green rust is a powerful reductant for CCl4 +e CX4 -X.CX3 -R. :CX3- +2e -2X:CX2 -X- +R-H +H2O -2HX HCOO- +H+ HCX3 CO +OH- Not well understood what controlls the 1e vs either 2e or ee halves Eng. Life Sci 007 7 1 2-60, Masih, Izumi, Aika, Seida, Optimation of an Iron Intercalated Montmorillonite Preparation for theRemoval of Arsenic at Low Concentrations The most active iron species for arsenic adsorption was prepared by ion exchange Converts arsenite to arsentate IN order to determine the mechanism of reaction the authors compare Fe They do NOTstate, But it is k12 Implicit in The application Of the comparison OX CX 4 products k12 Vary CX4 =change in K12 k11k22 K12 f But same reaction Mechanism ( Reorganization energies) With the reaction of Fe porphyrin CX 4 products 1e k12 hydroquinone mercapto juglone CX 4 products 2e k12 Should get a slope close to 1 in comparing the two types of reactions If they are similar. They find a slope of 0.86 in comparing the Rates of reactions of Fe-O-X to juglone so they conclude the reaction is Most likely could involve 2 e Compared 1 vs 2 e products as a function of surface coverage by Fe(II) and Conclude that the relative importantce of 2e transfer increases with Fe(II) Coverage (provides adjacent sites) At higher pH the 1e pathway increaseswhich they suggest is due tote prsence of green rust precipitates which have both Fe(II) and Fe(III) centers thus reducing the concentration of Fe(II) adjacent sites. T2g d orbitals on the Central metal lie Somewhat out of The path of the Incoming octahedrally Oriented ligands Eg d orbitals on central metal lie in the path Of incoming octahedrally Oriented ligands Image: A Van der Ven and G. Ceder, p 47 in Lithium Batteries Science and Technology, Nazri and Pistoia, eds., Kluwer, 2004 An extreme example of the inner sphere work required is to reduce an iron containing crystal Charge transport in micas: The kinetics of FeII/III electron transfer in the octahedral sheet, Keven M. Rosso and Eugene S. Ilton, . J of Chemical Physics, 119, 17, 9207 Hydroxyl group at “waist” (cis) Hydroxyl group at apex (trans) Calculate the self exchange Of FeII to FeIII from the M1 And M2 sites using a cluster Anschtz, amy J. and R. Lee Pnn, Reduction of crystalline iron(III) oxyghydroxides Uisng hydroquinone: influence of phase and particle size, Geochemical Transacations, 2005, 6,3, 60-66 Prepare ferrihdrite 6 nm nanorod goethite microrod goethite Characterize the surface area by TEM, and calculation of edge area Characeerize the cyrstallinity of the mineral surfaces 2 2 Fe5 HO8 4 H2 Os 5H 2 Q 20 H 5Q 10 Feaq 24 H 2 O ferrihydrite 2 10 FeOOH s 5H 2 Q 20 H 10 Feaq 5Q 20 H 2 O goethite Stoichiometry checked; initial rates measured by the production of Q as a function Of H2Q concentration holding the total iron constant Anschtz, amy J. and R. Lee Pnn, Reduction of crystalline iron(III) oxyghydroxides Uisng hydroquinone: influence of phase and particle size, Geochemical Transacations, 2005, 6,3, 60-66 Prepare ferrihdrite 6 nm nanorod goethite microrod goethite Characterize the surface area by TEM, and calculation of edge area Characeerize the cyrstallinity of the mineral surfaces Table 2 here Reactivity of ferrihydrite was two orders higher – suggested Related to cyrstallinity and greater surface area/unit iron. To account for possilbe diffusion through different void shapes the data for Ferrihydrite was compared for two different particle sizes to determine an Area dependent rate and the relative reaction orders Suggest that it is not area per se but thenumber of kinks and atomic steps Present resulting in greater surface energy and reativity also showing differnet Reaction orders with the larger size ferrihydrite showing Anschtz, amy J. and R. Lee Pnn, Reduction of crystalline iron(III) oxyghydroxides Uisng hydroquinone: influence of phase and particle size, Geochemical Transacations, 2005, 6,3, 60-66 Reactivity of ferrihydrite was two orders higher – suggested Related to cyrstallinity and greater surface area/unit iron. To account for possilbe diffusion through different void shapes the data for Ferrihydrite was compared for two different particle sizes to determine an Area dependent rate and the relative reaction orders Suggest that it is not area per se but thenumber of kinks and atomic steps Present resulting in greater surface energy and reativity also showing differnet Reaction orders with the larger size ferrihydrite showing d Q m n k H2 Q S dt Model 1D 1D 2D 2D Particle 4nm-6LF 6nm-6LF Nanorod Microrod Accounting for diffusion as either 1D on the surface Or two dimensional for the nanoand micro rods m 0.55 0.79 0.92 0.82 n 0.51 1.29 1.61 1.74 kBET 1.29x108 /h-m2 0.35x108/h-m2 7.2x 3.6x Only one possible literature comparison Andrew G. Stack, Kevin M. Rosso, Dale M. A. Smith, and Carrick M. Eggleston, Reaction of hydroquinone with hematite. II. Calculated electron-transfer rates and comparison to the reductive dissolution rate, Journal of Colloid and Interface Science 2004, 274-442-450. Fe x Oy Fe x O y e Fe x Oy Q H 2 Fe x Oy QH2 k12 K Stack, EC-STM Measured 1.1 Q/nm2 McBride and Wesselink mesured QH2 on boehmite (AlOOH) of 0.2QH2/nm2 Find that they have no correlation with the rate of dissolution Suggest that the mechanism genealized as 1. H2Q adsorption 2. Et to form a semiquinone and reduced iron 3. Desorption of the semiquinone 4. Dissolution of the reduced iron 5. Adsorption of the semiquinone 6. ET to form a quinone and reduced iron 7. Desorption of Q 8. Dissolution of reduced iron NOT RDS et large not likely NOT RDS et large could be RDS not likely For microbial rates would indicate that should be very high et dependent Primarily on the orientaiton of the active enzyme site to the surface Enzyem aticle on hemtatie and goethite here Direct et Cell attachment Cell cyt c orientation distance Calculate The electrostatic surface of the iron oxides The electrostatic of the heme Calculate inner sphere bond length changes Calculate the work to bring cytochrome and hematite together from the charges Calculate activation energy and the rate of electron transfer as a function of cyt c distance from the iron oxide surface k et Ae f 4 F E E o wo wr Grxo 1 1 i o 4 i o G rnn ro 2 2 Compares the calculated e.t. Rates with cell density Measurements of colonies Assuming growth limited by e.t. External f F E E o wo wr Grxo 1 1 i o 4 i o G 4 2 Suggest: Larger internal reorganization energies associated with the iron oxide surfaces as opposed to the internal bulk mineral internal 3.43 5.34 4.303 Rate of cell density increase (104/cm2)/min Results are not consistent suggesting that ……. More work 2 Microbial driven reduction 1. Direct contact by dissimilatory iron reducing bacteria (DIRB Assumes pili of the baceria could either attach and/or reduce the iron. Suggest the possibility of nanowires to shuttle electrons (Reguera, G., McCarthy, K. D., Mehta, T., Nicoll, J. S.Tu 2. Chelators to enhance solubility 3. Existing electron mediators humic acids (functional groups are quinones) (analog is 2,6-anthraquinone disulfonate (AQDS) 4. Production of electron mediators