3D simulation of flow field heterogeneity impact on mass transfer for emodin recovery in a packed adsorption column

This study presents a comprehensive 3D computational fluid dynamics (CFD) framework, coupled with a linear driving force (LDF) model, to investigate the impact of flow field heterogeneity on the dynamic adsorption of emodin (EMO) in packed columns. The packed column has an inner diameter of 19.98 mm and a bed height of 0.05 cm, packed with DX06 adsorbent particles having an average diameter of 0.662 mm. Combined with steady Darcy-Brinkman flow and transient mass transfer equation, the model was validated through seven fixed-column experiments using lab-synthesized DX06 resin under varying operational conditions. 3D simulations revealed significant spatial velocity variations, including near-wall oscillations, interstitial high-velocity corridors, and quasi-stagnant zones, creating heterogeneous distributions of local mass transfer coefficients. Parametric analysis showed that increasing inlet EMO concentration accelerated breakthrough and exhaustion times. An optimal flow rate of 1 mL/min was identified, balancing external film resistance and residence time to maximize the overall mass transfer coefficient (K_f = 3.57 × 10⁻⁵ m/s). Furthermore, the mass transfer zone (MTZ) evolution was characterized in three distinct stages: formation (0 to 41 min, HMTZ = 3.02 cm), migration (41 to 86 min), and moving-out (86 to 235 min). Molecular docking revealed that π-π stacking interactions dominate the EMO/DX06 adsorption mechanism. Reusability tests confirmed stable performance over three cycles. This 3D CFD-LDF approach provides a robust tool for the design and optimization of industrial packed-bed adsorption systems.