Mechanistic Understanding of Asphaltene Surface Interactions in Aqueous Media
Bibliographic record
Abstract
The interactions between asphaltene surfaces in aqueous media play important roles in many interfacial processes and phenomena in oil production and wastewater treatment. In this study, the interaction mechanisms between asphaltene surfaces in aqueous solutions were investigated using a surface forces apparatus (SFA) and atomic force microscopy (AFM). SFA results showed a long-range repulsion between two asphaltene surfaces in 1 mM NaCl solution at pH 8.5, and the force range dropped with decreasing the solution pH. Increasing the NaCl concentration only slightly affected the interaction behavior between asphaltene surfaces at pH 8.5. However, the addition of Ca 2+ substantially decreased the repulsion between the asphaltene surfaces. The measured long-range repulsion could not be described by the classical Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, which was mainly attributed to the steric interactions resulting from the formation of the pancake domains and the increased surface roughness of the asphaltene surfaces in aqueous solutions as evident from the AFM topographic imaging. Adhesion was detected during separation of the two asphaltene surfaces under all the solution conditions investigated, which could be attributed to the hydrophobicity of the asphaltene surfaces, their van der Waals attraction, and the interpenetration of the asphaltene chains/aggregates with polar groups or Ca 2+ -induced bridging when Ca 2+ ions were added. The pH, salinity, and Ca 2+ addition also influenced the adhesion strength measured between the asphaltene surfaces. Using AFM, the interactions between an AFM tip and asphaltene surfaces under the same solution conditions as in SFA experiments were measured to better understand the interactions of asphaltenes at nanoscale. Theoretical calculations based on the DLVO theory reasonably agreed with the measured force curves for the AFM tip–asphaltene surface interactions, indicating the DLVO interaction origin of asphaltenes in aqueous solutions at nanoscale. Our results provide useful insights into the asphaltene interaction mechanisms at both nanoscale and surface level in aqueous media, with implications for the stabilization mechanism of oil-in-water emulsions and solid particles in the presence of asphaltenes.
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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) | 0.001 | 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 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".