Some Historical Briefs and Outlooks of the Chemical and Biological Acid Leaching of Uranium Ores
Bibliographic record
Abstract
The purpose of this paper is to briefly review early developments in the chemical and biological acid leaching of uranium ores in Portugal, Canada, Sweden, Finland, Estonia, and Pakistan. Uranium exists in tetravalent (U(IV)) and hexavalent (U(VI)) oxidation states in igneous, metamorphic, and sedimentary mineral deposits. Acidic ferric sulfate is a chemical oxidant of tetravalent uranium and is regenerated from ferrous iron in the leachate and produced also from pyrite (FeS2, cubic), marcasite (FeS2, orthorhombic), greigite (Fe3S4) and pyrrhotite (Fe1-xS) by acidophilic Fe- and S-oxidizing bacteria and archaea. The hexavalent uranium is soluble in sulfuric acid solution (lixiviant) and is recovered in downstream hydrometallurgical processing to produce a concentrate (yellowcake). The acid bioleaching reactions are optimal at pH 1.5-3 as the low pH facilitates proton attack on minerals and alleviates the precipitation of metals in the leachate and on mineral surfaces. Uranium is extracted from ores on a commercial scale using heap, dump, and stope leaching processes. In some operations other metals can also be recovered as byproducts in the process.
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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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.004 | 0.006 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.002 | 0.003 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.009 | 0.006 |
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".