Data di Pubblicazione:
2025
Citazione:
Nanoscale analysis of Red Muds from Portovesme (Sardinia) / Ouladmansour, A.; Millán, J. J.; Abad Martìnez, M. I.; Mesto, E.; Lacalamita, M.; Agrosì, G.; Mongelli, G.; Mameli, P.; Schingaro, E. - (2025), pp. 153-153. (Intervento presentato al convegno Congresso congiunto SIMP-SGI 2025 Geosciences and the Challenges of the 21st Century tenutosi a Padova (Italy) nel 16 -18 September 2025) [10.3301/absgi.2025.03].
Abstract:
At the Porto Vesme disposal site in southern Sardinia, Italy, about 30 million tonnes of bauxite residues
from aluminium extraction using the Bayer process are stored. The mineralogical and geochemical features
of these residues have recently been investigated, also to assess the economic viability of extracting rare earth
elements (REEs) and other valuable elements, such Ga, Sc, V (Mameli et al., 2025; Schingaro et al., 2025). The
samples mineralogy includes hematite, goethite, ilmenite, gibbsite, boehmite, bayerite, anatase, rutile, quartz,
sodalite, cancrinite, andradite, calcite, dolomite, halite. Lanthanides-rich phosphate minerals as well as LREE
ferrotitanates were sporadically observed. The samples chemistry provides Fe2O3, Al2O3, SiO2, Na2O, TiO2 and
CaO in order of abundance but also relevant concentrations of Zr, Cr, Ce, V, Sr, Ni, Zn, Ga and Y. The REEs
are enriched relative to the parent material with LREEs > HREEs+Y and Sc. Ce is the most abundant LREE
and the chondrite normalized patterns show significant positive Ce anomalies. However identification of REE/
valuable elements bearing phases in bauxite residue is not a trivial task and necessitates investigation at the
nanoscale.
Preliminary results of TEM analyses have revealed the abundant presence of Fe-Ti oxides bearing Ca, Cr and
LREE with laminar habit and lattice fringes spacing around 2.70 Å which can correspond with a ferrotitanate
phase. EDS identification of the precise ferrrotitanate composition is difficult because of the LREE, Ti, and Cr
intense and complex X-ray energy overlaps in the 4.5 to 6 keV spectral interval, especially when Ti has high
concentration (Lacinska et al., 2021). However, detailed EDS analyses allowed the identification of a well
defined peak for the Lα line of La (4.65 keV), slightly overlapped with Ti Kα line (4.52 keV). Ce was identified
by the Ce Lβ line at 5.26 keV, given that Ce Lα line (4.84 keV) was usually hidden by the Ti Kβ line (4.93
keV). Cr was easily identified by its Cr Kα line (5.41 keV).
from aluminium extraction using the Bayer process are stored. The mineralogical and geochemical features
of these residues have recently been investigated, also to assess the economic viability of extracting rare earth
elements (REEs) and other valuable elements, such Ga, Sc, V (Mameli et al., 2025; Schingaro et al., 2025). The
samples mineralogy includes hematite, goethite, ilmenite, gibbsite, boehmite, bayerite, anatase, rutile, quartz,
sodalite, cancrinite, andradite, calcite, dolomite, halite. Lanthanides-rich phosphate minerals as well as LREE
ferrotitanates were sporadically observed. The samples chemistry provides Fe2O3, Al2O3, SiO2, Na2O, TiO2 and
CaO in order of abundance but also relevant concentrations of Zr, Cr, Ce, V, Sr, Ni, Zn, Ga and Y. The REEs
are enriched relative to the parent material with LREEs > HREEs+Y and Sc. Ce is the most abundant LREE
and the chondrite normalized patterns show significant positive Ce anomalies. However identification of REE/
valuable elements bearing phases in bauxite residue is not a trivial task and necessitates investigation at the
nanoscale.
Preliminary results of TEM analyses have revealed the abundant presence of Fe-Ti oxides bearing Ca, Cr and
LREE with laminar habit and lattice fringes spacing around 2.70 Å which can correspond with a ferrotitanate
phase. EDS identification of the precise ferrrotitanate composition is difficult because of the LREE, Ti, and Cr
intense and complex X-ray energy overlaps in the 4.5 to 6 keV spectral interval, especially when Ti has high
concentration (Lacinska et al., 2021). However, detailed EDS analyses allowed the identification of a well
defined peak for the Lα line of La (4.65 keV), slightly overlapped with Ti Kα line (4.52 keV). Ce was identified
by the Ce Lβ line at 5.26 keV, given that Ce Lα line (4.84 keV) was usually hidden by the Ti Kβ line (4.93
keV). Cr was easily identified by its Cr Kα line (5.41 keV).
Tipologia CRIS:
4.2 Abstract in Atti di convegno
Keywords:
Bauxite residues (red muds), Sardinia, TEM
Elenco autori:
Ouladmansour, A.; Millán, J. J.; Abad Martìnez, M. I.; Mesto, E.; Lacalamita, M.; Agrosì, G.; Mongelli, G.; Mameli, P.; Schingaro, E
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Titolo del libro:
Geosciences and the Challenges of the 21st Century