A Novel Hybrid Adsorbent Based on Fly Ash and Waste Flax Fibers for Efficient Separation of Rare Earth Ions from Water

In this study, carbonaceous and hybrid adsorbents were synthesized from waste flax fibers and fly ash, integrating two abundant waste streams into a single functional material. Materials were thermally modified and activated with NaOH at 500 °C in a nitrogen atmosphere. The prepared adsorbents exhibit high efficiency for scandium ion removal, with the hybrid systems significantly outperforming the individual components. The obtained Langmuir maximum adsorption capacities for the adsorption of scandium onto hybrid adsorbents were 18.28 and 32.32 mg/g, depending on the flax fibers/fly ash ratio. The contrasting thermodynamic behavior between hybrid adsorbents of different composition highlights the significant influence of material structure on the adsorption mechanism. The results demonstrate that the synergistic integration of waste flax fibers and fly ash in hybrid materials produces efficient and environmentally sustainable adsorbents, offering a novel approach for REE recovery from aqueous systems.