TY - JOUR
T1 - The role of nano-perovskite in the negligible thorium release in seawater from Greek bauxite residue (red mud)
AU - Gkamaletsos, Platon
AU - Godelitsas, Athanasios
AU - Kasama, Takeshi
AU - Kuzmin, Alexei
AU - Lagos, Markus
AU - Mertzimekis, Theo J.
AU - Göttlicher, Jörg
AU - Steininger, Ralph
AU - Xanthos, Stelios
AU - Pontikes, Yiannis
AU - Angelopoulos, George N.
AU - Zarkadas, Charalampos
AU - Komelkov, Aleksandr
AU - Tzamos, Evangelos
AU - Filippidis, Anestis
PY - 2016
Y1 - 2016
N2 - 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 mu g g(-1)), along with minor U (15 mu g g(-1)), which are responsible for radioactivity (355 and 133 Bq kg(-1) for Th-232 and U-238, respectively) with a total dose rate of 295 nGy h(-1). Leaching experiments, in conjunction with SF-ICP-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-STEM-HAADF 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 L-III-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.
AB - 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 mu g g(-1)), along with minor U (15 mu g g(-1)), which are responsible for radioactivity (355 and 133 Bq kg(-1) for Th-232 and U-238, respectively) with a total dose rate of 295 nGy h(-1). Leaching experiments, in conjunction with SF-ICP-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-STEM-HAADF 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 L-III-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.
U2 - 10.1038/srep21737
DO - 10.1038/srep21737
M3 - Journal article
C2 - 26899139
SN - 2045-2322
VL - 6
JO - Scientific Reports
JF - Scientific Reports
M1 - 21737
ER -