Bioleaching of copper mining residues by Aspergillus niger
Bibliographic record
Abstract
A study was initiated to determine the possibility of using the fungus Aspergillus niger for bioleaching and then to identify and evaluate the parameters that affect this process. An oxidized mining residue containing mainly copper (7240 mg/kg residue) was studied. Sucrose and mineral salts medium were initially used to produce citric and gluconic acids by A. niger with various concentrations of residue (1, 5, 7, 10 and 15% w/v). Maximal removal of up to 60% of the copper was obtained for the 5% residue. These experiments showed that the pH decreased to around three within 10 days of incubation. Other substrates were evaluated including molasses, corn cobs and brewery waste. Sucrose gave the best results for copper removal, followed by molasses, corn cobs and brewery waste. Other experiments using ultrasound as a pre-treatment showed that 80% removal of the copper could be obtained for a 5% residue concentration. In conclusion, leaching of copper from a mining residue is technically feasible using A. niger. Further research must be performed to increase the economic feasibility of 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 | 0.000 | 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".