A Novel Cerium-Loaded Amyloid Hybrid Membrane for Advanced Removal of Fluorine-18 in Medical Wastewater

Despite its critical role in disease diagnosis as a radiopharmaceutical, Fluorine-18 generates medical wastewater that necessitates efficient treatment, for which membrane adsorption stands out as a potent method, albeit one that demands high-performance membranes with exceptional permeability and adsorption capacity. This study presents a novel cerium-loaded amyloid fibril hybrid membrane designed for efficient removal of fluorine-18 from such wastewater. The membrane is fabricated through a facile process involving oxidation-precipitation of cerium species onto amyloid fibrils, followed by vacuum filtration, with further compositional tuning via incorporation of porous silica or activated carbon dopants. The resulting membrane retains the characteristic amyloid fibril structure and exhibits high water permeability with a flux of up to 803.3 L/(m²·h·bar), superior to most of the other membrane materials. It effectively removes fluoride ions (F^-) from both low and high-concentration solutions, achieving a removal efficiency of up to 99% and a maximum adsorption capacity of 580 mg/g, outperforming many existing membrane materials. The hybrid membrane also demonstrates notable resistance to ionic interference, enabling selective F^- adsorption from solutions containing high concentrations of Cl^-, NO₃^- and SO₄^2-, with a distribution coefficient (Kd) as high as 4.1 × 10⁴ mL/g; furthermore, it maintains a fluoride removal rate above 51% after ten consecutive adsorption cycles. The membrane retains 51% of its initial fluoride removal efficiency after 10 cycles, indicating potential for repeated use, although further optimization or regeneration strategies would be required to fully restore performance. Mechanistic investigations reveal that F^- adsorption occurs mainly through ion exchange with hydroxyl groups on CeO₂. This work introduces a promising novel material with significant potential for the efficient treatment of medical radioactive wastewater containing fluorine-18.