The beneficiation of rare earth element-bearing minerals
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Bibliographic record
Abstract
Rare earth elements (REE) comprise the fifteen elements of the lanthanide series as well as yttrium, and may be found in over 250 different minerals. These elements are required for many different applications such as high-strength permanent magnets, catalysts for petroleum refining, metal and glass additives and phosphors used in electronic displays. REE are abundant in the earth's crust, yet deposits with economically extractable concentrations are much less common. This thesis examines the separation techniques that are currently employed for REE bearing mineral (REM) beneficiation, identifies areas in need of further research, employs characterisation techniques to examine fundamental properties of certain REM, and then applies this knowledge to the beneficiation of the Nechalacho REE deposit in the Northwest Territories of Canada.In order to build up the knowledge of the physicochemical properties of important REM, pure samples of minerals such as bastnäsite, allanite, fergusonite and zircon were acquired along with common gangue minerals in the Nechalacho deposit such as magnetite, hematite and quartz. After characterisation experiments were completed for each of these minerals, lab-scale separation experiments were conducted on a bulk sample from the Nechalacho deposit involving a series of gravity and magnetic separations. A pre-concentration flowsheet was then selected with the resultant product being used for downstream flotation experiments. As the feed sample for flotation was concentrated in many REM, it provided an excellent opportunity for assessing flotation kinetics of these minerals in a multi-mineral system as well as investigating different reagent additions which may be applicable to the development of an industrial flotation process.The major findings from characterisation experiments include the verification of the paramagnetism of REM, the identification of hydroxamates as an ideal flotation reagent for the concentration of bastnäsite from silicate gangue as well as the finding that hydroxamates are not suitable for the flotation of allanite, a silicate REM. Additional work was undertaken to develop a means of floating allanite using alternative reagents such as dodecylamine and the addition of metal ion activators. The concentration of REM from the Nechalacho deposit using physical separation was successfully achieved using a Knelson centrifugal gravity separator and a low intensity magnetic drum separator. The resultant product had a grade of 7.50 wt. % rare earth oxide (REO) and a REO recovery of 11.8 %. An additional finding from this work was that the concentration of the most valuable heavy REE is upgraded in the coarse size fractions after grinding to a P80 of 40 µm.Subsequent ore flotation experiments using this material found that the kinetics of REM flotation from this deposit using hydroxamates are strongly dependent on mineral solubility and metal cation content. Additionally, the addition of lead cations to this system improves the recovery of less floatable REMs such as allanite, and the staged addition of hydroxamates results in improved REM grade and recovery.The implications of this research work includes an improved understanding of fundamental REM properties as well as multiple strategies for improving industrial process designs for the Nechalacho deposit. Implementing selective comminution strategies to upgrade the concentration of the most valuable REE could have a profound effect on any future process by providing a simple means of beneficiation as well as minimizing energy losses in overgrinding. Two different flotation reagent strategies have been investigated with different outcomes. The staged addition of hydroxamate targets REM with rapid flotation kinetics whereas the addition of lead ions is able to improve the recovery of REM with slower flotation kinetics. These reagent schemes may have applications in different stages of an industrial flotation process.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it