Revisiting temperature effect on the kinetics of liquid-phase adsorption by the Elovich equation: A simple tool for checking data reliability

Background: It is recognized that temperature has a significant effect on adsorption processes, including equilibrium and kinetics. In the past decades, the effect of temperature on adsorption equilibrium has been widely studied, which allows us calculating the thermodynamic parameters. On the other hand, the effect of temperature on adsorption kinetics was scarcely explored, which likely is attributed to the lack of a common, suitable, but sufficiently simple kinetic model, unlike the case of isotherm modeling. Methods: Kinetic data of liquid-phase adsorption processes abstracted from the literature and measured in this study were analyzed by the Elovich equation. The effect of temperatures on adsorption kinetics was explored such that its activation energy was determined based on the variations of the initial rates of adsorption (a parameter in the Elovich equation) with temperatures according to the Arrhenius equation. Significant findings: Among the twelve sets of adsorption processes studied herein, most of the adsorption processes (~80%) revealed an activation energy of 12.1 to 25.6 kJ mol(-1) in the temperature range of 293-323 K. However, three processes gave an abnormally high activation energy of 45.8-72.9 kJ mol(-1), in which data recheck was therefore suggested. The Elovich equation could be served as a simple tool to analyze and check the reliability and accuracy of the kinetic data (particularly, activation energy) in an adsorption process.

Automated summary

Temperature has a significant effect on adsorption processes, particularly on adsorption equilibrium. While the effect of temperature on adsorption kinetics has been less explored, likely due to a lack of a simple and suitable kinetic model. This study analyzed kinetic data using the Elovich equation and found that most adsorption processes had an activation energy in the range of 12.1 to 25.6 kJ mol(-1).