Two-Dimensional Modeling and Simulation of Nonlinear Isothermal Gradient Elution Chromatography with Radial Concentration Gradients

Chromatography is a widely used separation technique, often relying on conventional unidimensional isocratic models. However, these models fail to capture radial concentration gradients from imperfect sample injection and the benefits of gradient elution, where solvent strength varies. This study proposes a two-dimensional nonlinear isothermal equilibrium dispersive model

with gradient elution to better represent the physical phenomena. The model equations, subject to various initial and boundary conditions, are numerically solved using a high-resolution finite volume scheme (HR-FVS). This scheme ensures at least second-order accuracy by employing higher-order accuracy in smooth regions while minimizing numerical dissipation near discontinuities. Extensive case studies covering critical parameter ranges are conducted. The presented results provide deeper insights into nonlinear isothermal gradient elution chromatography, supporting process optimization. Incorporating gradient elution and radial concentration gradients in the two-dimensional model offers a comprehensive representation of the chromatographic separation process, facilitating improved design and operation of chromatographic columns.