Abstract

A review of a certain class of theoretical models describing the kinetics of pollutants sorption onto various sorbents is presented. These assuming the rate of surface reaction as the rate-limiting step are considered. A special attention is paid to possible theoretical grounds of the most commonly applied mathematical expressions, such as the pseudo-second and the pseudo-first order equations. Simple theoretical considerations based on some fundamental theories suggest that these two formulae do not correspond to any specific physical model. They simply approximate well the behaviours predicted by many different theoretical approaches.

Keywords: Sorption; Modeling; Kinetics; Pseudo-first order; Pseudo-second order; Pollutants removal

Article Outline

1. Introduction

2. Models overview

2.1. Langmuir kinetic model

2.2. Statistical Rate Theory (SRT) approach

2.3. The pseudo-second, the pseudo-first and the Elovich equations

2.3.1. The pseudo-second order equation

2.3.2. The pseudo-first order equation

2.3.3. Some considerations on the correlation of the experimental data by using the pseudo-first and the pseudo-second order equations

2.3.4. The Elovich equation

2.4. Other models

3. Concluding remarks

Acknowledgements

References