Study of Asphaltene Adsorption on Kaolinite by X-ray Photoelectron Spectroscopy and Time-of-Flight Secondary Ion Mass Spectroscopy
Bibliographic record
Abstract
The interaction between asphaltenes and clay is crucial in understanding wettability changes in petroleum reservoirs and in oilsands production. In this study, we report the changes in surface properties and composition of kaolin clay as a result of exposure to solutions of asphaltenes. Adsorption experiments were conducted at 25 °C with solutions of asphaltenes in toluene at concentrations ranging from 0.05 to 5 mg/mL. The wettability of the modified kaolinite surface was characterized by contact angle measurement. Chemical composition changes of the surface because of asphaltene adsorption were assessed using time-of-flight secondary ion mass spectroscopy (ToF-SIMS), X-ray photoelectron spectroscopy (XPS), and elemental analysis. The contact angle data indicated that, upon asphaltene adsorption, the clay particles changed from water-wet to bi-wet. Both ToF-SIMS and XPS measurements indicated that the kaolinite surface was never completely covered by asphaltenes based on the concentration of Al and Si on asphaltene-treated kaolinite surfaces. ToF-SIMS analysis indicated that, with more asphaltenes covered on the kaolinite surface, the relative intensities of C 3 H 5 + /Al + and C 3 H 5 + /Si + increased and an inverse linear correlation between the contact angle and surface Si + concentration was observed. The maximum thickness of adsorbed asphaltenes, assuming complete surface coverage, was estimated to be 11 nm based on XPS depth profile results on a model silica surface, with a mean value of 3 nm. The XPS depth profile also indicated no preferential adsorption of nitrogen- or sulfur-rich species at the interface between asphaltenes and kaolinite.
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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) | 0.001 | 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) | 0.002 | 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".