| Simulation of pyrite oxidation in fresh mine tailings under near-neutral conditions. | |
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MedLine Citation:
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PMID: 22777533 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Sulphidic residual products from ore processing may produce acid rock drainage, when exposed to oxygen and water. Predictions of the magnitude of ARD and sulphide oxidation rates are of great importance in mine planning because they can be used to minimize or eliminate ARD and the associated economic and environmental costs. To address the lack of field data of sulphide oxidation rate in fresh sulphide-rich tailings under near-neutral conditions, determination and simulation of the rate was performed in pilot-scale at Kristineberg, northern Sweden. The quality of the drainage water was monitored, along with oxygen and carbon dioxide concentrations. The chemical composition of the solid tailings was also determined. The field data were compared to predictions from simulations of pyrite oxidation using a 1-D numerical model. The simulations' estimates of the amount of Fe and S released over a seven year period (52 kg and 178 kg, respectively) were in reasonably good agreement with those obtained by analysing the tailings (34 kg and 155 kg, respectively). The discrepancy is probably due to the formation of secondary precipitates such as iron hydroxides and gypsum; which are not accounted for in the model. The observed mass transport of Fe and S (0.05 and 1.0 kg per year, respectively) was much lower than expected on the basis of the simulations and the core data. Neutralization reactions involving carbonates in the tailings result in a near-neutral pH at all depths except at the oxidation front (pH < 5), indicating that the dissolution of carbonates was too slow for the acid to be neutralized, which instead neutralized deeper down in the tailings. This was also indicated by the reduced abundance of solid Ca at greater depths and the high levels of carbon dioxide both of which are consistent with the dissolution of carbonates. It could be concluded that the near-neutral pH in the tailings has no decreasing effect on the rate of sulphide oxidation, but does reduce the concentrations of dissolved elements in the drainage water due to the formation of secondary minerals. This means that sulphide oxidation rates may be underestimated if determined from drainage alone. |
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Authors:
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Lena Alakangas; Angela Lundberg; Peter Nason |
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Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-7-10 |
Journal Detail:
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Title: Journal of environmental monitoring : JEM Volume: - ISSN: 1464-0333 ISO Abbreviation: - Publication Date: 2012 Jul |
Date Detail:
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Created Date: 2012-7-10 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 100968688 Medline TA: J Environ Monit Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
Affiliation:
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Division of Geosciences and environmental engineering, Luleå University of Technology, SE-97187, Sweden. Lena.Alakangas@ltu.se. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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