Low molecular weight carboxylic acids in oxidizing porphyry copper tailings

Détails

ID Serval
serval:BIB_B078B97ADBA5
Type
Article: article d'un périodique ou d'un magazine.
Collection
Publications
Institution
Titre
Low molecular weight carboxylic acids in oxidizing porphyry copper tailings
Périodique
Environmental Science and Technology
Auteur⸱e⸱s
Dold B., Blowes D.W., Dickhout R., Spangenberg J.E., Pfeifer H.R.
ISSN-L
0013-936X
Statut éditorial
Publié
Date de publication
2005
Peer-reviewed
Oui
Volume
39
Pages
2515-2521
Langue
anglais
Résumé
The distribution of low molecular weight carboxylic acids (LMWCA) was
investigated in pore water profiles from two porphyry copper tailings
impoundments in Chile (Piuquenes at La Andina and Cauquenes at El
Teniente mine). The objectives of this study were (1) to determine the
distribution of LMWCA, which are interpreted to be the metabolic
byproducts of the autotroph microbial community in this low organic
carbon system, and (2) to infer the potential role of these acids in
cycling of Fe and other elements in the tailings impoundments. The
speciation and mobility of iron, and potential for the release of H+ via
hydrolysis of the ferric iron, are key factors in the formation of acid
mine drainage in sulfidic mine wastes. In the low-pH oxidation zone of
the Piuquenes tailings, Fe(III) is the dominant iron species and shows
high mobility. LMWCA, which occur mainly between the oxidation front
down to 300 cm below the tailings surface at both locations (e.g., max
concentrations of 0.12 mmol/L formate, 0.17 mmol/L acetate, and 0.01
mmol/L pyruvate at Piuquenes and 0.14 mmol/L formate, 0.14 mmol/L
acetate, and 0.006 mmol/L pyruvate at Cauquenes), are observed at the
same location as high Fe concentrations (up to 71.2 mmol/L Fe(II) and
16.1 mmol/L Fe(III), respectively). In this zone, secondary Fe(111)
hydroxides are depleted. Our data suggest that LMWCA may influence the
mobility of iron in two ways. First, complexation of Fe(III), through
formation of bidentate Fe(III)-LMWCA complexes (e.g., pyruvate,
oxalate), may enhance the dissolution of Fe(III) (oxy)hydroxides or may
prevent precipitation of Fe(III) (oxy)hydroxides. Soluble Fe(III)
chelate complexes which may be mobilized downward and convert to Fe(II)
by Fe(III) reducing bacteria. Second, monodentate LMWCA (e.g., acetate
and formate) can be used by iron-reducing bacteria as electron donors
(e.g., Acidophilum spp.), with ferric iron as the electron acceptor.
These processes may, in part, explain the low abundances of secondary
Fe(III) hydroxide precipitates below the oxidation front and the high
concentrations of Fe(II) observed in the pore waters of some low-sulfide
systems. The reduction of Fe(III) and the subsequent increase of iron
mobility and potential acidity transfer (Fe(II) oxidation can result in
the release of H+ in an oxic environment) should be taken in account in
mine waste management strategies.
Création de la notice
26/09/2012 14:11
Dernière modification de la notice
20/08/2019 15:19
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