Impact of various inorganic oxyanions on the removal rates of hexavalent chromium mediated by zero-valent iron
Bibliographic record
Abstract
Environmental context. Oxyanions in soil extract can interfere with the zero valent iron induced reduction of chromium(VI) to chromium(III). At pH 6, the reaction rate was decreased (2 to 6-fold) by an equivalent of arsenate, phosphate or silicate but was increased by sulfate and remained unchanged by borate or nitrate. At pH 2, not only was the rate of reaction dramatically increased (~900-fold) but interferences from the major components of soil solution (nitrate, silicate and sulfate) were minimised. Abstract. The rate of zero-valent iron (ZVI) mediated reduction of CrVI was dependent on the condition of the ZVI surface, the pH of the medium and on the presence of inorganic oxyanions that can interfere with the process by competing for active sites on the ZVI surface. Whereas at pH 2, a single exponential decay provided an acceptable fit to the data, for pH 6 an appreciably better fit to the data was obtained with the sum of two exponential decays. The surface area normalised rate constant (kSA1) corresponding to the first decay was considered to model reactions at exposed active sites and kSA2, corresponding to the second decay, was considered to model decomposition kinetics through an intervening oxyhydroxide layer above the ZVI surface. The rate of CrVI reduction was decreased ~900-fold when the pH was increased from 2 to 6 in the absence of competing ions. At pH 2, interferences from the major components of soil solution (nitrate, silicate and sulfate) were minimised.
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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) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 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".