Synchrotron X-ray absorption spectroscopic study of thorium in ilmenite and titanium slag: towards green mineral processing

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Thorium as a common radionuclide in some ore minerals, mine wastes and mine tailings poses a serious risk to the environment on the one hand but represents a potential source of this strategic material for the thorium fuel cycle that is becoming increasingly viable in recent years. Therefore, extraction of thorium as a byproduct from ores or waste materials not only has environmental benefits but also is of economic value. Three types of materials that contain elevated thorium contents are: (1) anhydrite- and gypsum-rich tailings stemming from the extraction of rare earth elements from monazite and bastnaesite ores; (2) ferroniobium slag from smelting of pyrochlore concentrates to produce ferroniobium alloy and (3) titanium slag (used for TiO2 pigment) from smelting of ilmenite concentrates extracted from heavy mineral sands. Extraction of thorium as a byproduct and recovery of thorium from mine wastes for the thorium fuel cycle both require detailed knowledge about the distribution, speciation and uptake mechanisms of thorium in host materials. The present study, in collaboration with Rio Tinto Fer et Titane of Sorel-Tracy, Quebec, is designed to use several state-of-the-art analytical techniques (e.g., microbeam synchrotron X-ray fluorescence mapping, synchrotron X-ray absorption spectroscopy, and electron paramagnetic resonance spectroscopy) to investigate the distribution, speciation and uptake mechanisms of thorium in selected titanium slags and ilmenite concentrates, with applications to both minimizing radiation risks to the environment and potential development of new techniques to extract this material for the thorium fuel cycle. The specific objectives of the proposed project include: 1) systematic study on the distribution of thorium in titanium slags and ilmenite concentrates, 2) detailed structural study on the speciation and uptake mechanisms of thorium in titanium slags and ilmenite concentrates, and 3) preliminary experiments to extract thorium from titanium slags and ilmenite concentrates. This project of combined basic and applied research provides an excellent training opportunity for one PhD student (Kamil Chadirji-Martinez) and one undergraduate research assistant at the University of Saskatchewan.