Process intensification of xanthene dye sequestration using a recirculating fixed-bed configuration: High-fidelity CFD diagnostics and synergistic regeneration

While conventional single-pass adsorption columns often suffer from limited residence time and mass transfer resistances, this study proposes a process intensification strategy through a novel recirculating flow configuration for Rhodamine B (RhB) recovery using Purolite C100 resin. Beyond standard batch assessments, which confirmed a chemisorption-driven mechanism (PSO, R 2 > 0.99), the research focuses on the dynamic transition from single-pass to recirculated systems. The recirculating mode achieved 91% removal efficiency, effectively overcoming film diffusion limitations prevalent in traditional setups. A high-fidelity Computational Fluid Dynamics (CFD) model was developed to provide spatio-temporal diagnostics of the mass transfer zone (MTZ) and internal concentration gradients, bridging the gap between laboratory observations and industrial scale-up. Furthermore, a synergistic binary eluent (70% EtOH/1 M HCl) ensured near-quantitative dye elution (~100%), aligning the process with circular economy principles. This holistic framework demonstrates that integrating multiphysics simulations with innovative flow configurations is essential for optimizing sustainable wastewater remediation units.