Effects of Weathering on Leaching Properties of Slag from a Niobium Mine, Oka, Quebec
Bibliographic record
Abstract
Between 1961 and 1976 niobium ore was mined by the St. Lawrence Columbium Group in the community of Oka, located approximately 50 km W of Montreal, Quebec. Ferroniobium was formed through aluminothermic reduction of pyrochlore-group minerals. This process produced circular slag casts that were discarded in a small dump at the mine site. This work is designed to provide knowledge with respect to the long-term stability of Oka slag and the reaction processes that control drainage water chemistry in slag disposal areas. The slag casts were sampled at the top, middle, and bottom based on the expectation that fractional crystallization had influenced the mineralogy and geochemistry during the cooling process. The slag mineralogy is dominated by hibonite, β-alumina, perovskite, calcium zirconate and F-Na-bearing calcium aluminate glass. Secondary minerals occur in close proximity to aluminum-calcium rich phases (hibonite, perovskite, gehlenite) and they were investigated in detail at the nanoscale using (S)TEM analyses and the results indicate that the secondary coatings are composed of a number of discrete phases. Whole-rock geochemical characterization demonstrates that Oka slag contains significant quantities of REE, U and Th. Bench scale leaching experiments were conducted using columns filled with crushed slag from the top, middle and bottom of the casts to investigate the mobility of U, Th, and REE in water draining from the slag. In general, the column effluent is characterized by high pH (maximum 13) and elevated Al (maximum 4906 mg/L) and F (704 mg/L). In the top sample, weathering of alumino-silicates and Al-rich glass resulted in high pH and elevated F- concentrations, which rendered the slag from the top of the casts to be highly reactive, releasing high concentrations of Al, Ca, Na, and K and leading to the formation of mixed secondary amorphous Al/Ca hydroxide and barite (BaSO4). The leaching and secondary-mineral properties of slag from the middle of the casts were similar, although aqueous concentrations in the leachate were slightly lower and secondary-minerals included amorphous Si oxy-hydroxides. In general, leachate from the bottom of the slag casts displayed the lowest concentrations of major cations and the lowest reactivity. Secondary minerals were lesser abundant, but similar in composition to the top and middle of the casts except for the occurrence of Fe oxy-hydroxides resulting from weathering of ferri-gehlenite.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.002 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".