Adsorption Isotherms of Benzene and Its Derivatives by RPLC Frontal Analysis

Abstract

The adsorption behaviour of solute is one of the most important
factors to design a batch and a continuous liquid chromatographic separation
process. In liquid chromatography, these behaviours are based
on the adsorption equilibrium between a liquid mobile-phase and a solid
stationary-phase. However, almost of the retention models were developed
under linear adsorption isotherm only few researchers have investigated
the relationship between the adsorption parameters and the mobile phase
composition and some empirical models were introduced. In this work,
the adsorption isotherms were obtained by the frontal analysis for 4
low-molecular compounds (benzene, toluene, chlorobenzene and 1,2-
dichlorobenzene) on a commercial C₁₈ bonded column. The absorption
based on the linear and Langmuir models was investigated according to
the changes of the composition of methanol high-enriched eluent. The
calculations and analysis of the coefficients obtained for both models
confirm that the adsorption data for solutes are best modeled with the
linear approach. Langmuir isotherm model couldn't satisfactorily
describe mechanism and provide the objective information on the physical
nature of the absorption in spite of the acceptable accuracy.