ATR-FTIR Studies on the Adsorption/Desorption Kinetics of Dimethylarsinic Acid on Iron–(Oxyhydr)oxides
Bibliographic record
Abstract
Dimethylarsinic acid (DMA) is an organoarsenical compound that, along with monomethylarsonic acid, poses a health and an environmental risk, and a challenge to the energy industry. Little is known about the surface chemistry of DMA at the molecular level with materials relevant to geochemical environments and industrial sectors. We report herein the first in situ and surface-sensitive rapid kinetic studies on the adsorption and desorption of DMA to/from hematite and goethite at pH 7 and I = 0.01 M KCl using ATR-FTIR. Values for the apparent rates of adsorption and desorption were extracted from experimental data as a function of spectral components, flow rate of the aqueous phase, film thickness of hematite, and using chloride and hydrogen phosphate as desorbing agents. The adsorption kinetic data show fast and slow rates, consistent with the formation of more than one type of adsorbed DMA. Apparent adsorption and desorption rate constants were extracted from the dependency of the initial adsorption rates on [DMA(aq)]. Desorption rate constants were also extracted from desorption experiments using hydrogen phosphate and chloride solutions, and were found to be higher by 1-2 orders of magnitude than those using chloride. In light of the complex ligand exchange reaction mechanism of DMA desorption by phosphate species at pH 7, apparent desorption rate constants were found to depend on [hydrogen phosphate] with an order of 0.3. The impact of our studies on the environmental fate of DMA in geochemical environments, and the design of technologies to reduce arsenic content in fuels is discussed.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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 teacher head, 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".