Kinetic Model of Batch Sorption Processes: Comparing Calculated and Experimental Data

The possibility of deriving a model of the kinetics of batch sorption processes is considered by transforming a nonlinear difference kinetic equation with a nonconstant equilibrium parameter for the interface into approximate pseudo first- and second-order equations with fixed parameters, depending on the characteristic of equilibrium isotherms in a certain way. The calculated and experimental equilibrium and kinetic parameters are compared for a large number of processes, including the sorption and electrosorption of metal ions on activated coals, the sorption of lead on nanostructured carbon materials, and phosphatidylcholine sorption on ordered mesoporous nanostructured silica materials. Good coincidence is observed between the calculated equilibrium data and the respective experimental results obtained in kinetic experiments. At the same time, there is no correspondence between calculated and experimental dimensionless parameters based on the relationships of kinetic coefficients for different order equations (due apparently to great errors in determining these coefficients when processing the experimental data using the pseudo second-order model of kinetics). The obtained results confirm earlier conclusions that it is impossible to characterize the mechanisms of kinetic processes based only on good descriptions of experimental results using pseudo first- or second-order kinetic equations.