Visualization of Type-J counter current chromatography: Hydrodynamic behavior in a helical column

Area of Science:

• Chromatography
• Chemical Engineering
• Fluid Dynamics

Background:

• Counter-current chromatography (CCC) relies on the hydrodynamic motion of two-phase solvent systems.
• Previous visualization studies used stroboscopic photography, limiting real-time observation.
• On-line visualization of solvent distribution and movement is crucial for understanding CCC hydrodynamics.

Purpose of the Study:

• To continuously visualize and analyze the dynamic motion and phase distribution of solvent systems in a running CCC bobbin.
• To investigate the hydrodynamic behavior of both quaternary (HEMWat) and ternary solvent systems during CCC separation.
• To correlate observed hydrodynamic phenomena with CCC separation efficiency.

Main Methods:

• Utilized a high-speed imaging camera for continuous on-line video recording of a running CCC bobbin.
• Investigated conventional quaternary solvent system hexane/ethyl acetate/methanol/water (HEMWat) and ternary solvent system dichloromethane/methanol/water.
• Recorded dynamic motion, phase distribution, and sample dispersion processes during CCC operation.

Main Results:

• Observed wave-like mixing in areas of minimum centrifugal force across different column diameters.
• Demonstrated that the mixing zone remained fixed at the minimum centrifugal force position upon coil rotation.
• Found that phase dispersion remained largely unchanged once equilibrium was established in the rotating coiled tube.
• Recorded the sample dispersion process, providing insights into solute movement.

Conclusions:

• The study provides valuable on-line visualization of solvent dynamics in CCC.
• Observed hydrodynamic behaviors, such as wave-like mixing and stable phase distribution, offer insights into separation mechanisms.
• Results facilitate a better understanding of CCC separation processes and highlight areas for future research on separation efficiency.