The Balance between Diffusional and Surface Reaction Kinetic Models: A Theoretical Study

Abstract

In this work we considered the factors determining the rate of adsorption. By assuming the balance between the surface reaction and diffusional mechanisms we discussed the possibility to conclude which model is the rate-controlling step. By using the pseudo first-order Lagergren equation we showed the theoretical interpretation of the Lagergren coefficient. If this parameter is time-dependent, the diffusional model should be assumed to represent the kinetics of adsorption. Such property can be utilized practically to resolve the rate-determining step. We also discussed the influence of surface energetic heterogeneity on the mechanism of the rate of adsorption.

Keywords:

• adsorption
• Fick's second law
• Lagergren equation
• rate-determining step