New thermodynamically consistent competitive adsorption isotherm in RPLC.

Area of Science:

• Chromatography
• Physical Chemistry
• Adsorption Science

Background:

• Predicting multicomponent adsorption behavior is crucial for separation processes.
• Existing models often struggle with varying saturation capacities of individual components.
• Thermodynamic consistency is essential for accurate isotherm modeling.

Purpose of the Study:

• To develop a new equation for competitive adsorption isotherms within the Ideal Adsorbed Solution (IAS) framework.
• To predict multisolute adsorption isotherms using single-solute data.
• To validate the model's performance with experimental data for toluene and ethylbenzene mixtures.

Main Methods:

• Derived a new competitive isotherm equation based on IAS theory.
• Utilized liquid-solid extended multilayer Brunauer-Emmett-Teller (BET) isotherm for single-solute data.
• Experimentally determined adsorption isotherms for toluene and ethylbenzene on a Kromasil-C(18) column.
• Modeled elution band profiles of binary mixtures using the new competitive model.

Main Results:

• The new IAS-based model accurately predicts multisolute adsorption isotherms.
• Experimental adsorption data for toluene and ethylbenzene fit well to single-component isotherms with adjusted capacities.
• The model demonstrated excellent agreement with experimental elution band profiles for mixtures.
• Observed deviations between predicted and measured plateau concentrations were less than 2%.

Conclusions:

• The derived competitive isotherm equation, based on IAS theory, provides thermodynamically consistent predictions for multisolute adsorption.
• The model effectively captures the behavior of toluene-ethylbenzene mixtures, indicating near-ideal adsorbed phase behavior.
• This approach offers a reliable method for predicting complex adsorption phenomena from simpler single-solute data.