The role of nano-perovskite in the negligible thorium release in seawater from Greek bauxite residue (red mud)

Scientific publication - Journal Article uoadl:2320623 1296 Read counter

Unit:
Department of Geology and Geoenviromment
Title:
The role of nano-perovskite in the negligible thorium release in seawater from Greek bauxite residue (red mud)
Languages of Item:
English
Abstract:
We present new data about the chemical and structural characteristics of bauxite residue (BR) from
Greek Al industry, using a combination of microscopic, analytical, and spectroscopic techniques.
SEM-EDS indicated a homogeneous dominant “Al-Fe-Ca-Ti-Si-Na-Cr matrix”, appearing at the
microscale. The bulk chemical analyses showed considerable levels of Th (111 μg g−1), along with
minor U (15 μg g−1), which are responsible for radioactivity (355 and 133 Bq kg−1 for 232Th and 238U,
respectively) with a total dose rate of 295 nGy h−1. Leaching experiments, in conjunction with SFICP-
MS, using Mediterranean seawater from Greece, indicated significant release of V, depending on
S/L ratio, and negligible release of Th at least after 12 months leaching. STEM-EDS/EELS & HR-STEMHAADF
study of the leached BR at the nanoscale revealed that the significant immobility of Th4+ is due
to its incorporation into an insoluble perovskite-type phase with major composition of Ca0.8Na0.2TiO3
and crystallites observed in nanoscale. The Th LIII-edge EXAFS spectra demonstrated that Th4+ ions,
which are hosted in this novel nano-perovskite of BR, occupy Ca2+ sites, rather than Ti4+ sites. That is
most likely the reason of no Th release in Mediterranean seawater.
Publication year:
2016
Authors:
Platon N. Gamaletsos
Athanasios Godelitsas
Takeshi Kasama
Alexei Kuzmin
Markus Lagos
Theo J. Mertzimekis
Jörg Göttlicher
Ralph Steininger
Stelios Xanthos
Yiannis Pontikes
George N. Angelopoulos
Charalampos Zarkadas
Aleksandr Komelkov
Evangelos Tzamos
Anestis Filippidis
Journal:
Scientific Reports
Publisher:
Nature Publishing Group
Volume:
6
Number:
-
Pages:
21737
Keywords:
bauxite, thorium, red-mud, titanium, perovskite, nano, synchrotron, TEM
Main subject category:
Science
Official URL (Publisher):
Bauxite_red_mud_Sci.Reports2016.pdf (5 MB) Open in new window