Modeling of adsorption dynamics at air-liquid interfaces using statistical rate theory (SRT)

Area of Science:

• Physical Chemistry
• Surface Science
• Chemical Engineering

Background:

• Mass transfer at interfaces is crucial in many natural and technological processes.
• Interfacial properties like adsorption impact wetting, foaming, coating, and film stabilization.
• Current models often rely on Fick's law for diffusion and empirical equations for adsorption kinetics.

Purpose of the Study:

• To develop a general theoretical model for adsorption kinetics/dynamics at the air-liquid interface.
• To derive a new kinetic equation based on statistical rate theory (SRT).
• To identify and characterize different regions of adsorption dynamics.

Main Methods:

• Development of a general theoretical model for adsorption kinetics.
• Derivation of a new kinetic equation using statistical rate theory (SRT).
• Numerical simulations of surface adsorption and verification of the model.
• Analysis of adsorption dynamics using dimensionless numbers: psi, lambda, and Nk.

Main Results:

• A new SRT-based kinetic equation for adsorption dynamics was derived.
• Three distinct regions of adsorption dynamics were identified: diffusion controlled, mixed diffusion and transfer controlled, and transfer controlled.
• The Nk number was found to predominantly determine the adsorption dynamics regime.
• Lower values of psi and lambda were shown to favor maximum surface adsorption and surface tension reduction.

Conclusions:

• The developed model provides a more mechanistic understanding of adsorption kinetics at air-liquid interfaces.
• The dimensionless number Nk effectively categorizes adsorption dynamics into three distinct regions.
• The study offers insights into optimizing surface adsorption for applications like surface tension reduction.