A Model for the Structure of Adsorbed Layers at Solid/Liquid Interfaces
Ying Li1, Wanguo Hou1,2
1Key Laboratory of Colloid & Interface Chemistry (Ministry of Education), Shandong University, Jinan 250100, P. R. China.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 8, 2022
Summary
A new dynamic bonding equilibrium (DBE) model correlates adsorbed layer structure, including composition and thickness, with equilibrium adsorption amount. This thermodynamic model aids in understanding and predicting adsorption layer characteristics at solid/liquid interfaces.
Area of Science:
- Physical Chemistry
- Surface Science
- Thermodynamics
Background:
- Understanding adsorbed layer structure (composition, thickness) is crucial for adsorption studies.
- Existing thermodynamic models lack a feasible description of the correlation between adsorbed layer structure and equilibrium adsorption amount.
- Adsorbed layers of organics at solid/liquid interfaces are significant in various applications.
Purpose of the Study:
- To develop a feasible thermodynamic model correlating adsorbed layer structure (mole fraction of sorbate, xA, and thickness, d_al) with equilibrium adsorption amount (Γe).
- To provide a method for predicting or describing the structure of adsorbed layers from equilibrium adsorption data.
Main Methods:
- Development of the dynamic bonding equilibrium (DBE) model based on adsorption equilibrium thermodynamics.
- Assumption that sorbate and solvent in the adsorbed layer exist in different bonding states at equilibrium.
- Validation of the DBE model using literature data for various organics (surfactants, proteins, polymers) on different surfaces.
Main Results:
- The DBE model successfully relates adsorbed layer composition (xA) and thickness (d_al) with the equilibrium adsorption amount (Γe).
- The model's predictions align with experimental adsorption data reported in the literature.
- Demonstrated applicability across diverse organic adsorbates and surface types (hydrophilic, hydrophobic).
Conclusions:
- The developed DBE model offers a feasible thermodynamic approach to characterize adsorbed layer structure at solid/liquid interfaces.
- This model provides valuable insights into the nature of adsorption and can guide applications.
- Enables obtaining structural information of adsorbed layers directly from equilibrium adsorption measurements.
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