|Title: ||The role of nano-perovskite in the negligible thorium release in seawater from Greek bauxite residue (red mud)|
|Authors: ||Gamaletsos, Platon N. ×|
Mertzimekis, Theo J.
Angelopoulos, George N.
Filippidis, Anestis #
|Issue Date: ||2016 |
|Series Title: ||Scientific Reports vol:6|
|Article number: ||10.1038/srep21737|
|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 (232)Th and (238)U, 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 Th(4+) is due to its incorporation into an insoluble perovskite-type phase with major composition of Ca(0.8)Na(0.2)TiO3 and crystallites observed in nanoscale. The Th L(III)-edge EXAFS spectra demonstrated that Th(4+) ions, which are hosted in this novel nano-perovskite of BR, occupy Ca(2+) sites, rather than Ti(4+) sites. That is most likely the reason of no Th release in Mediterranean seawater.|
|Publication status: ||published|
|KU Leuven publication type: ||IT|
|Appears in Collections:||Sustainable Metals Processing and Recycling|