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Detachment of Dodecane from Silica Surfaces with Variable Surface Chemistry Studied Using Molecular Dynamics
Binbin Jiang1, Huan Hou2, Qian Liu2
1State Key Laboratory of Water Resource Protection and Utilization in Coal Mining, China Energy Investment Group, Beijing 102211, China.
Molecules (Basel, Switzerland)
|June 28, 2023
Summary
Oil detachment from silica surfaces depends on silanol group density and type. Molecular dynamics simulations reveal Q3 surfaces facilitate easier oil removal via water diffusion and H-bonding. Q2 and Q4 surfaces hinder detachment due to silanol group interactions.
Area of Science:
- Surface Science
- Computational Chemistry
- Materials Science
Background:
- Understanding oil-water-solid interactions is crucial for various industrial processes.
- Silica surface chemistry, particularly silanol group density and type, influences interfacial behavior.
- Previous studies have explored surface properties, but detailed molecular insights into detachment mechanisms are needed.
Purpose of the Study:
- To investigate the adsorption and detachment of n-dodecane on silica surfaces with varying chemistry.
- To elucidate the role of silanol group density (Q2, Q3, Q4 environments) and type in oil detachment.
- To understand the molecular mechanisms governing oil-water-silica contact line dynamics.
Main Methods:
- Molecular dynamics simulations were employed to model n-dodecane adsorption and detachment.
- Simulations were conducted on silica surfaces with controlled silanol group densities (0 to 9.4 nm⁻²).
- Analysis focused on contact line dynamics, water diffusion, and hydrogen bonding interactions.
Main Results:
- Oil detachment was significantly easier and faster on perfect Q3 silica surfaces (≡Si(OH) groups) due to water-silanol H-bond formation.
- Increased Q2 silica surfaces (≡Si(OH)₂ groups) reduced oil detachment due to silanol-silanol H-bonding.
- No oil detachment occurred on Q4 surfaces (no silanol groups), as water could not diffuse at the contact line.
Conclusions:
- Oil detachment efficiency from silica is governed by both the area density and type of silanol groups.
- Surface chemistry, influenced by factors like cleavage plane and humidity, dictates detachment behavior.
- Molecular dynamics provides valuable insights into the complex interplay of surface properties and interfacial processes.
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