Recycling of Rare Earth Element from Nickel Metal Hydride Battery Utilizing Supercritical Fluid Extraction
Bibliographic record
Abstract
The anode of nickel metal hydride battery contains about 30 wt% of rare earth elements, namely, lanthanum, cerium, praseodymium, and neodymium. These elements are in increasing high demand, but facing supply uncertainty and near zero recycling. Current recycling practices rely on either pyrometallurgy or hydrometallurgy. The former is highly energy intensive and the latter relies on large volumes of acids and organic solvents, generating large volumes of hazardous residues. This study put the emphasis on developing an innovative and environmentally sustainable process for the urban mining of rare earth elements from nickel metal hydride battery. The developed process relies on supercritical fluid extraction utilizing CO 2 as the solvent. This process is very efficient because it runs at low temperature, and does not produce hazardous waste, while recovering about 90% of rare earth elements.
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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 | 0.001 |
| Open science | 0.000 | 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".