THORIUM SPECIATION IN SYNTHETIC ANHYDRITE, PLACER ILMENITE CONCENTRATE, AND TITANIA SLAG: IMPLICATIONS FOR THORIUM GEOCHEMICAL BEHAVIOR, SEQUESTRATION, AND BENEFICIATION

Understanding thorium speciation and distribution in ore minerals and related materials is of critical importance so that the thorium fuel cycle can be sourced as byproducts from metallurgical processes. The objective of this dissertation is to study thorium-bearing species in selected ore minerals and their metallurgical products, and the uptake mechanisms of thorium into these materials. Gaining an understanding of thorium in these materials will improve both thorium extraction and sequestration methods. Conditions present in the Sulfuric Acid Roasting Method for rare-earth element (REE) mineral processing were simulated to synthesize thorium-bearing anhydrite. Synchrotron ThLIII-edge X-ray absorption spectroscopy (XAS) reveals that lattice-bound Th in anhydrite, via the substitution Th4++1O2–iCa2+-1 with an interstitial O2– ion, can account for at least 1780 ppm Th in anhydrite produced in relevant experimental conditions. Ilmenite concentrate from the Mandena deposit, Madagascar, used to produce titania slag, contains 133 ppm Th and 12.8 ppm U. Our data show that monazite-(Ce), mainly as discrete grains, accounts for ~55% of thorium in the Mandena ilmenite concentrates. Thorianite hosting the remaining thorium at ~45% is revealed by synchrotron ThLIII edge XAS and is correlated with the degree of ilmenite alteration. Titania slag produced from the Mandena ilmenite concentrate contains an average of 170 ppm Th and 16 ppm U. Our data collectively demonstrate that 95.37% of Th in the Rio Tinto Chloride Slag (RTCS) is hosted by a Th-REE-Ti-silicate phase, containing up to 9.24 wt% ThO2 with an empirical formula of (Ti1.37Ca0.79Ce0.72Th0.36La0.31Nd0.30Pr0.08Ba0.03K0.02Y0.01U0.01)□(Ti1.41Al0.27 Fe2+0.11 Mn0.08 Mg0.07Nb0.03Zr0.03)(Ti1.91□0.09)(Si3.05Ti0.95)O22. This Th-REE-Ti-silicate occurs as acicular (<0.3 μm ⨯ 12 μm) or tabular (<5 μm ⨯ 15 μm) crystals in association with an aluminosilicate glass as infillings either in interstitial to or along fractures of the main Ti-Fe-oxides of the sassite-ferropseudobrookite solid solution series, formed most likely during the quenching stage of the titania slag. The viability of using primary ores and metallurgy products is evaluated based on their production tonnage, thorium concentration, and speciation. Hypothetically, if the global energy demand was met using only liquid fluoride thorium reactors, the cumulative thorium produced by the three mineral processing facilities studied would be sufficient to meet that global energy demand.

Name thesis:degree_name

Doctor of Philosophy (Ph.D.)

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Geology

Grantor

University of Saskatchewan

Year dc:date.issued

2023

Author dc:creator

• Chadirji-Martinez, Kamil

Advisor dc:contributor.advisor

• Pan, Yuanming

Committee members dc:contributor.committeemember

• Eglington, Bruce
• Ansdell, Kevin
• Butler, Samuel
• Zhao, Baodong
• Urquhart, Stephen
• Grosvenor, Andrew

• thorium
• XANES
• EXAFS
• rare earth
• anhydrite
• titanium
• slag
• synchrotron
• XRF
• EMPA
• ilmenite
• leucoxene
• QEMSCAN
• synthesis
• hydrometallurgy
• Th
• Th4+
• sulfuric acid roasting
• Raman
• pXRD
• substitution
• chevkinite
• Bayan Obo
• Baotou
• Mandena Deposit
• Madagascar
• actinide
• LA-ICP-MS
• geochemistry

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10388/15306

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/15306