Restoration of in situ leached uranium mines with iron nanoparticles
Bibliographic record
Abstract
In situ leaching (ISL) provides a method of extracting uranium from the subsurface without direct excavation or perturbation. Following ore removal at an ISL site, environmental responsibility lies with subsequent restoration of the groundwater system. The experiments outlined in the current study were driven by the possibility of injecting metallic iron nanoparticles into the ore zone with the purpose of (i) immobilising residual soluble uranium (VI) as insoluble uranium (IV) oxide and (ii) restoration of anoxic conditions within the subsurface. The study also explores the possibility of persistent inflow of oxygen into the ore zone or change in the redox conditions of the geological zone, Solutions highly concentrated in uranium (1000 ppm) with an initial pH ranging from 3 to 7 were studied in presence of zero valent iron nanoparticles under mildly oxic conditions (1.2 % O2 and 0.0017 % CO2) to simulate the oxidizing conditions of a exhausted uranium mine. Characterisation of both solid and solution phases indicated that at 4 hours period of reaction the Eh stabilized at values ranging from -0.1 to -0.4 V. The addition of iron nanoparticles triggered the reductive precipitation of UO2, which was demonstrated to be the main process responsible for the removal of uranium from solution at reaction times between 1 to 4 hours [1,2] . The reoxidation of uranite precipitated on the nanoparticle surface was studied at mildly acidic and at neutral-basic conditions to account for the possible disruption of the reducing conditions in the geological zone. Despite thermodynamic modelling calculations of the studied system using NEA-TDB [3] indicate UO3.2H2O as the only uranium solid phase for 4 < pH < 9, the experimental results indicated that a Fe-uranyl phase with becquerelite-like crystalline structure stabilized at neutral basic pH [4]. [1] Chadwick (1973) Chem. Phys. Lett. 21 (2), 291-294. [2] Scott et al. (2005) Geochim. Cosmochi. Acta 69 (24). [3] Guillaumont et al. (2003) Chemical Thermodynamics 5. NEA OECD, Elsevier. [4] Burns et al. (1996) The Canadian Mineralogist 34.
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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 | 0.000 |
| 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) | 0.000 | 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".