Thorium speciation in titania slag: Implications for environmental remediation and valorisation
Date
2024-11
Authors
Chadirji-Martinez, K
Hudon, G
Chernikov, R
Heredia, E
Feng, Renfei
Crawford, A
Pan, Yuanming
Journal Title
Journal ISSN
Volume Title
Publisher
Mineralogical Magazine
ORCID
Type
Preprint
Degree Level
Abstract
Titania slag, produced from smelting placer ilmenite concentrates and used as a feedstock for TiO2 pigment production, contains low levels of radioactivity due to thorium and uranium. This study investigated the distribution and speciation of thorium in Rio Tinto Chloride Slag (RTCS), which contains an average of 170 ppm Th and 16 ppm U, using a variety of analytical methods from powder X-ray diffraction (pXRD) analysis to bulk and laser ablation inductively coupled plasma mass spectrometry (ICP-MS and LA-ICP-MS), electron microprobe analysis (EMPA), quantitative evaluation of materials by scanning electron microscopy (QEMSCAN), Raman spectroscopy, microbeam synchrotron X-ray fluorescence (µsXRF) mapping, synchrotron Laue X-ray diffraction (LXRD) and synchrotron X-ray absorption spectroscopy (XAS). Our data demonstrate that ~99.4% of Th in the RTCS is hosted by a chevkinite-like Th-REE-Ti aluminosilicate containing an average of 8.05±0.64 wt.% ThO2. The Th-REE-Ti aluminosilicate occurs as acicular (~0.3x12 µm) or tabular (~5x15 µm) crystals in association with a Th-bearing
aluminosilicate glass (0.41±0.35 wt.% ThO2) as infillings either in interstitials or along the fractures of the main Ti-Fe oxides of the sassite-ferropseudobrookite solid-solution series. The Th-REE-Ti aluminosilicate and associated Th-bearing aluminosilicate glass formed probably
during the quenching stage of the titania slag production. LA-ICP-MS analyses and µsXRF mapping show that the main Ti-Fe oxides in the RTCS contain only an average of 0.32±0.60ppm Th. Future pyrometallurgy operations that utilize Th- and U-bearing heavy mineral sands
must consider their environmental effects and mitigate radioactivity. Also, preferential acid dissolution of the Th-REE-Ti aluminosilicate in RTCS and other titania slags may be used to recover Th and REE for dual environmental and economic benefits.
Description
Keywords
Thorium, titania slag, chevkinite-group, synchrotron XAS, valorisation
Citation
Chadirji-Martinez, K., Hudon, G., Chernikov, R., Heredia, E., Feng, R., Crawford, A., & Pan, Y. (2024). Thorium speciation in titania slag: Implications for environmental remediation and valorisation. Mineralogical Magazine, 1–35. https://doi.org/10.1180/mgm.2024.69
Degree
Department
Program
Advisor
Committee
Part Of
item.page.relation.ispartofseries
DOI
https://doi.org/10.1180/mgm.2024.69