Pyrite oxidation in alkaline solutions: Nature of the product layer

C. L. Caldeira, V. S.T. Ciminelli, A. Dias, Kwadwo Asare Osseo-Asare

Research output: Contribution to journalArticle

65 Citations (Scopus)

Abstract

The nature of the oxides formed during pyrite oxidation by molecular oxygen in alkaline solutions has been investigated with the aid of Eh-pH diagrams and direct analysis of the solid products. X-ray diffraction (XRD) and infrared analyses indicate that the products formed are determined by solution composition. In hydroxide medium, hematite, as the main phase, and small amounts of ferrihydrite are identified. In contrast, in carbonate medium, the main constituent is ferrihydrite, with some iron hydroxide carbonate phase also present. In calcium hydroxide medium, only calcium carbonate was detected on the surface of oxidized pyrite in an amount that increased when the system was opened to the atmosphere. Only by diffuse reflectance infrared spectroscopy (IR) was it possible to identify carbonate compounds among the products formed during pyrite oxidation in aqueous solutions. The morphology of the product layers was also affected by solution composition. In NaOH solutions, the particles are initially covered by a thin oxide layer that fractures after longer reaction times. Most of the oxide reports to the solution, where it remains as a stable suspension. Pyrite oxidation in Na2CO3/NaHCO3 solutions results in particles that are initially covered by a discontinuous oxide coating that grows with reaction time, thus increasing the overall pyrite surface coverage. In this case, a precipitation confined to the solid/liquid interface is favored by the higher ionic strength of the sodium carbonate solutions.

Original languageEnglish (US)
Pages (from-to)373-386
Number of pages14
JournalInternational Journal of Mineral Processing
Volume72
Issue number1-4
DOIs
StatePublished - Sep 29 2003

Fingerprint

Pyrites
pyrite
oxidation
Oxidation
Oxides
Carbonates
oxide
carbonate
ferrihydrite
hydroxide
iron hydroxide
Calcium Hydroxide
Hydrated lime
product
Molecular oxygen
Calcium Carbonate
infrared spectroscopy
Hematite
calcium carbonate
Calcium carbonate

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology
  • Geochemistry and Petrology

Cite this

Caldeira, C. L. ; Ciminelli, V. S.T. ; Dias, A. ; Osseo-Asare, Kwadwo Asare. / Pyrite oxidation in alkaline solutions : Nature of the product layer. In: International Journal of Mineral Processing. 2003 ; Vol. 72, No. 1-4. pp. 373-386.
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Pyrite oxidation in alkaline solutions : Nature of the product layer. / Caldeira, C. L.; Ciminelli, V. S.T.; Dias, A.; Osseo-Asare, Kwadwo Asare.

In: International Journal of Mineral Processing, Vol. 72, No. 1-4, 29.09.2003, p. 373-386.

Research output: Contribution to journalArticle

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