This research investigates the development of an innovative membrane for the treatment of saline 26 wastewater, with a specific focus on sodium ion removal. The deposition of Soy Protein Isolate 27 28 29 30 31 32 33 34 35 36 37 38 39 (SPI) amyloid nanofibrils (ANFs) onto electrospun cellulose acetate membranes (CAMs) significantly enhanced sodium ion removal efficiency. ANFs were synthesized from a 4 % w/v SPI solution at 85 °C for durations of 12, 18, and 24 h, resulting in the formation of fibrils with 57nm, 97 nm, and 250 nm, respectively. The formation of fibrils was confirmed through atomic force microscopy, CD-spectroscopy, and FTIR, which demonstrated a structural change from an alphahelix-rich to a beta-sheet-enhanced configuration (as quantified by CD spectral deconvolution) during the fibrillation process. Electrospun CAMs were immersed in fibril-containing solutions for 2 and 5 min. Filtration assessments revealed that fibrils produced with a mean diameter of 57nm and a 5 min immersion time achieved the highest sodium rejection rate (~15.90 %)representing a greater than threefold increase compared to the unmodified control membrane, which exhibited a sodium rejection rate of 4.4%. Contact angle measurements revealed that the incorporation of these smaller fibrils led to a significant enhancement in surface hydrophilicity, decreasing the contact angle from 136.1 ° to 73.3 °. Although sodium rejection remained modest Journal Pre-proof40 (15.9 %), the study demonstrates a proof-of-concept that soy protein fibrils can modulate 41 membrane hydrophilicity and surface morphology. The approach shows potential as a pretreatment 42 or ion-selective tuning strategy but requires further optimization for desalination applications.

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