Adsorption Thermodynamics of p-Arsanilic Acid on Iron (Oxyhydr)Oxides: In-Situ ATR-FTIR Studies
Bibliographic record
Abstract
The organoarsenical p-arsanilic acid (p-AsA) is used in the U.S. poultry industry as a feed additive and its structure resembles one of the stable biodegradation products of Roxarsone (ROX) in anaerobic environments. With the implementation of recent EPA MCL of total arsenic in drinking water (10 ppb), thereareconcernsaboutthefate of organoarsenicals introduced to the environment through the application of arsenic-contaminated manure. We report herein, for the first time, the thermodynamics of p-AsA binding to Fe-(oxyhydr)oxides using ATR-FTIR. ATR-FTIR spectra were used to quantify surface coverage of p-AsA, p-AsA(ads), by analyzing the broadband assigned to v(As-O) at 837 cm(-1). Adsorption isotherms were measured in situ at 298 K and pH 7 in the concentration range 1 microM to 40 mM. Values of Keq were obtained from Langmuir model fits and they range from 1411 to 3228 M(-1). We also determined the maximum adsorption capacities of Fe-(oxyhydr)oxides to p-AsA, and they range from 1.9 x 10(13) to 2.6 x 10(13) molecules/cm2. Our results suggest that p-AsA is more mobile than methylated and inorganic forms of arsenic and that the transport of nanoparticles with p-AsA(ads) might play a role in its mobility in geochemical environments.
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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) | 0.001 | 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".