Sequestration of arsenic and molybdenum during the neutralization of uranium mill wastes: Key Lake mill, Saskatchewan, Canada
Notice bibliographique
Résumé
The As- and Mo- bearing secondary mineral phases formed during the neutralization of uranium mill wastes were studied for a variety of ore blends including current and future ore sources at the Key Lake milling operation, northern Saskatchewan, Canada. A lab-scale plant model was employed to characterize secondary precipitates obtained during the mill waste neutralization process. Three scenarios of ore blends were processed through the lab-scale plant to produce mill waste solutions for neutralization before combination into final tailings. Slurry samples (n = 12) were collected from the secondary precipitates formed during the neutralization of mill wastes (raffinate) by precipitation with Ca(OH)2 (slaked lime) from pH 1.5 to 10.5. Synchrotron based X-ray absorption spectroscopy of mill and lab-scale plant precipitates showed arsenate adsorbed to ferrihydrite was the dominant As mineral phase regardless of pH or sample blend (53-77%), with fractional contributions from ferric arsenates, and adsorption to aluminum phases (AlOHSO4, As(OH)3 and hydrotalcite). Molybdate adsorbed to ferrihydrite was the dominant Mo mineral phase, regardless of pH or sample blend, with fractional contribution decreasing with increasing pH, and minor contributions from calcium molybdate, ferric molybdate and nickel molybdate. These results were used in geochemical modelling to predict the source terms for these mineral phases in tailings facilities. Sequestration of As and Mo in the model showed solubility was controlled by adsorption to both Fe and Al oxide surfaces as well as by direct precipitation with other dissolved constituents (Ni, Ca and SO4).The models developed pH profiles of mineral phase precipitation to explain the solubility of As, Mo, Fe, Al, Mg and Ni during sequestration from pH 1.5 to 10.5 that were consistent regardless of ore blend used in simulations. Since adsorption of anions to the surface of ferrihydrite has been shown to slow conversion to crystalline forms of Fe oxides (goethite and hematite) and sequestration of arsenate effectively controls As solubility at high pH (pH >10), As-bearing mineral phases are expected to be stable for thousands of years. With adsorption as well as direct precipitation considered, Mo phases though effectively sequestering below pH 8, became unstable and released Mo back into the tailings porewater (pH >10), as predicted by the thermodynamic model. Historical data obtained from as-discharged tailings as well as previously published U mill tailings studies agree with these findings.
Récupéré en direct depuis OpenAlex et désinversé. Les résumés ne sont pas conservés dans cette base de données : les index inversés représentent 8,6 Go des 9,3 Go de texte de la base, et le serveur dispose de 13 Go libres.
Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,000 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,001 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».