Molecular and electronic structure elucidation of Fe<sup>2+</sup>/Fe<sup>3+</sup> complexed chelators used in iron sulphide scale removal in oil and gas wells
Bibliographic record
Abstract
ABSTRACT Quantum chemical calculations based on DFT are employed to study the electronic structure and binding affinity of chelators used in the removal of iron sulphide scales. Three chelating agents, EDTA, HEDTA, and DTPA, are considered in this work. The complexes showed a coordination number of 5, 6, and 7 for Fe2+ and Fe3+ ions with HEDTA, EDTA, and DTPA, respectively. However, regarding EDTA, Fe3+ could coordinate with an additional water molecule and form a seven‐coordinate complex. The calculated binding energies agreed with the experimental stability constants of the chelators in the order DTPA > EDTA > HEDTA for both Fe2+/Fe3+ complexes. The binding free energies showed a spontaneous reaction with Fe3+ having a stronger binding affinity than Fe2+ due to electrostatic forces. This investigation provides insights regarding how chelators that are applied in iron sulphide scale removal may be designed by increasing the number of nitrogen atoms to above the number of carboxylate groups.
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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) | 0.003 | 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".