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| Titel |
Solid speciation and availability of nickel and chromium in Ni mining spoils |
| VerfasserIn |
Sophie Raous, Jérémie Garnier, Thibaul Sterckeman, Guillaume Echevarria, Thierry Becquer, Fabien Thomas |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250045358
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| Zusammenfassung |
| Nickel mining of ultramafic laterites generates different types of wastes, topsoils and ores that
are too poor in Ni to be currently processed. These are mixed and stored on heaps
which could be a potential source of Ni and Cr pollution. Chemical reactivity of
the main metal bearing phases present in the mining spoils of Goiás (Brasil) was
investigated. Principally a silicated ‘saprolite’ material and a Fe-oxide rich limonitic
material were isolated from the wastes. Their total Ni and Cr content are high,
respectively for Ni and Cr : 7,170 and 54,970 mg kg-1 in limonite and 12,200
and 12,650 mg kg-1 in saprolite. The main metal-bearing minerals, identified and
localized using XRD, TEM-EDX, Raman spectroscopy and Mossbaüer spectrometry
are well-crystallized minerals: goethite (75%), hematite (13%) and chromite in
limonite and ferruginous smectite, talc and chromite in saprolite. Single and sequential
extractions showed that the amounts of 1M KCl exchangeable Ni and Cr reached
respectively 7.1% and 0.03% of total contents in saprolite. Moreover, Cr(VI) extraction
by KH2PO4 showed that more than 2% (980 mg kg-1) of total Cr was under this
labile toxic form in limonite. This study allowed us to determine the main reactions
controlling the Ni and Cr mobility in the spoils i.e. Ni2+ cationic exchange in saprolitic
spoil and CrO32- surface complexation in limonitic spoil. This study allowed us
to demonstrate the need of chemical rehabilitation of mining wastes in order to
avoid the dispersion of the high contents of Ni and Cr available. It constitutes the
system definition needed to predict the Cr and Ni mobility in ultramafic mining
spoils. |
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