Abstract
The chemical and physical properties of rhenium render it a highly demanded metal for advanced applications in important industrial fields. This very scarce element occurs mainly in ores of porphyry copper-molybdenum deposits associated with the mineral molybdenite, MoS2, but it has also been found in granite pegmatites and quartz veins as well as in volcanic gases. Molybdenite is a typical polytype mineral which crystal structure is based on the stacking of [S-Mo-S] with molybdenum in prismatic coordination by sulphide anions; however, it is not yet clearly established if rhenium ions replace Mo4+ cations in a disordered way or else, if such replacement gives rise to dispersed nanodomains of a rhenium-rich phase. As a contribution to clarify this question, an X-ray absorption spectroscopy (XANES) study using synchrotron radiation was performed at the Re L3-edge of rhenium-containing molybdenite samples. Obtained results are described and discussed supporting the generally accepted structural perspective that rhenium is mainly carried by molybdenite through the isomorphous replacement of Mo, rather than by the formation of dispersed Re-specific nanophase(s).
Highlights
IntroductionRhenium (Re) was the last naturally occurring element to be discovered, with a mean concentration in the earth’s crust of the order of 1 ppb [1]
Rhenium (Re) was the last naturally occurring element to be discovered, with a mean concentration in the earth’s crust of the order of 1 ppb [1]. This very scarce element has been found in granite pegmatites and quartz veins as well as in volcanic gases, namely from the Kudryavy Volcano, Kurile Islands [3], but it occurs mainly in ores of porphyry copper-molybdenum deposits [4,5,6,7,8,9] associated to molybdenite, MoS2, generally recognized as the main Re-carrier in nature [10,11]
Re L3-edge X-ray absorption spectroscopy (XANES) spectra obtained from the molybdenite samples are reproduced in Figure 1; these spectra display identical layouts (Re L3-edge at 10.538 keV; first post-edge feature 0.014 keV and second 0.052 keV after the edge), quite coincident with the W L3-edge spectrum obtained for synthetic WS2 (W L3edge at 10.207 keV; first post-edge feature 0.014 keV and second 0.050 keV after the edge)
Summary
Rhenium (Re) was the last naturally occurring element to be discovered, with a mean concentration in the earth’s crust of the order of 1 ppb [1]. This very scarce element has been found in granite pegmatites and quartz veins (e.g. in Japan [2]) as well as in volcanic gases, namely from the Kudryavy Volcano, Kurile Islands [3], but it occurs mainly in ores of porphyry copper-molybdenum deposits [4,5,6,7,8,9] associated to molybdenite, MoS2, generally recognized as the main Re-carrier in nature [10,11]. The largest world rhenium producer is currently Chile, followed by the United States, Peru and Poland [20]
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