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The oxidative dissolution of arsenopyrite (FeAsS) and enargite (Cu3AsS4) by Leptospirillum ferrooxidans
Corkhill, C L; Wincott, P L; Lloyd, J R; Vaughan, D J
Geochimica Et Cosmochimica Acta. 2008;72(23):5616-5633.
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Abstract
Arsenopyrite (FeAsS) and enargite (Cu3AsS4) fractured in a nitrogen atmosphere were characterised after acidic (pH 1.8), oxidative dissolution in both the presence and absence of the acidophilic microorganism Leptospirillum ferrooxidans. Dissolution was monitored through analysis of the coexisting aqueous solution using inductively Coupled plasma atomic emission spectroscopy and coupled ion chromatography-inductively coupled plasma mass spectrometry, and chemical changes at the mineral surface observed using X-ray photoelectron spectroscopy and environmental scanning electron microscopy (ESEM). Biologically mediated oxidation of arsenopyrite and enargite (2.5g in 25 ml) was seen to proceed to a greater extent than abiotic oxidation, although arsenopyrite oxidation was significantly greater than enargite oxidation. These dissolution reactions were associated with the release of similar to 917 and similar to 180 ppm of arsenic into Solution. The formation of Fe(III)-oxyhydroxides, ferric sulphate and arsenate was observed for arsenopyrite, thiosulphate and an unknown arsenic oxide for enargite. ESEM revealed an extensive coating of an extracellular polymeric substance associated with the L.ferrooxidans cells on the arsenopyrite surface and bacterial leach pits suggest a direct biological oxidation mechanism, although a combination of indirect and direct bioleaching cannot be ruled out. Although the relative oxidation rates of enargite were greater in the presence of L. ferrooxidans, cells were not in contact with the surface suggesting an indirect biological oxidation mechanism. Cells of L. ferrooxidans appear able to withstand several hundreds of ppm of As(III) and As(V). (C) 2008 Elsevier Ltd. All rights reserved.
Keyword(s)
ACID-MINE DRAINAGE; AIR OXIDATION; BINDING-ENERGIES; LEACHING PATTERNS; MINERALS; MULTIPLET STRUCTURE; PYRITE; SULFIDE; THIOBACILLUS-FERROOXIDANS; VACANCY LEVELS; X-RAY PHOTOELECTRON
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- Corkhill, C. L. Wincott, P. L. Lloyd, J. R. Vaughan, D. J. EPSRC [R011822] The authors thank Professor Barrie Johnson and Dr. Kevin Hallberg (Bangor University) for providing cultures of acidophilic bacteria from their collection and invaluable discussions about the microbiology of L. ferrooxidans, Mr. Steve Caldwell, Mr. David Plant, Mr. Paul Lythgoe and Mr. Alastair Bewsher (University of Manchester) for assistance with ESEM, EPMA, ICP-AES and IC-ICP-MS data collection and Miss Kim Handley (University of Manchester) for her assistance with gene amplification techniques. This manuscript benefitted from the very useful comments of H.W. Nesbitt, M.A. McKibben and an anonymous reviewer. Financial support from EPSRC (Grant R011822) is gratefully acknowledged. 50 PERGAMON-ELSEVIER SCIENCE LTD OXFORD 373QV