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

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

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. (EN)

scientific_publication_article

Επιστημονική δημοσίευση - Άρθρο Περιοδικού (EL)

Scientific publication - Journal Article (EN)

Θετικές Επιστήμες (EL)

Science (EN)

Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών

Πέργαμος

Άρθρο Περιοδικού (Journal Article)

Αγγλική γλώσσα

2016-01-01

uoadl:2320623

https://pergamos.lib.uoa.gr/uoa/dl/object/uoadl:2320623