Wool-based biosorbents as separation media: Process performance, fixed-bed operation, and regeneration

Wool-derived materials—ranging from raw fibers and keratin powders to electrospun membranes and MOF-wool hybrids—have re-emerged as promising separation media for water purification. This critical review synthesizes peer-reviewed evidence (2020–2025) on the adsorptive separation of dyes and metal ions using wool-based materials, with an emphasis on process performance beyond material characterization. We first map materials, surface chemistries, and hybridization strategies that translate into separation-relevant properties (capacity, kinetics, selectivity, and mass-transfer coefficients). We then assess batch vs. fixed-bed operation, including breakthrough behavior, model discrimination (Thomas, Yoon–Nelson, Bohart–Adams), and scale-up descriptors (bed height, empty bed contact time). Particular attention is given to regeneration and multi-cycle stability, desorption agents (e.g., mild acids, EDTA), and performance decay. We discuss methodological alignment (Langmuir/Freundlich/Sips; PFO/PSO vs. diffusion-controlled kinetics), process intensification via electrospun modules and magnetic/photocatalytic hybrids, and the transition from synthetic matrices to real effluents. Finally, we outline the techno-economic and environmental aspects of waste-wool valorization within circular water-treatment schemes, identifying gaps that currently limit industrial adoption, such as the need for standardized fixed-bed testing and durability beyond 5–10 cycles under realistic chemistries. Overall, wool-derived biosorbents are not merely materials of interest; they are viable separation media that can enable low-cost, low-impact purification when engineered with process constraints in mind. We conclude with a prioritized roadmap for continuous operation, green regeneration, and global relevance of applications. • Waste wool enables low-cost adsorptive separation of dyes and metals. • Fixed-bed data analyzed with Thomas/Yoon–Nelson for scale-up guidance. • Regeneration assessed: ≥3–10 cycles and mild eluents for reuse. • Process-oriented metrics link capacity/kinetics to breakthrough control. • Roadmap to real effluents, TEA/LCA, and continuous water purification.