Cross-Linkable Protein Nanofiber Aerogels for the Removal of Cationic and Anionic Dyes

Water contamination by synthetic dyes from textile, plastic, paint, and paper industries poses a significant environmental and public health challenge. These dyes are chemically stable, toxic, and prone to bioaccumulation, necessitating efficient and sustainable removal strategies. Here, we present protein nanofiber-based aerogels derived from bovine serum albumin (BSA) as effective biobased adsorbents for dye removal. BSA nanofibers were prepared through a high-temperature, acid-mediated self-assembly process and subsequently cross-linked and freeze-dried to form porous aerogels. Degree of cross-linking was varied to assess impacts on aerogel porosity, mechanical strength, and adsorption efficiency. Optimized aerogel formulations exhibited high removal efficiencies exceeding 99% for both cationic (crystal violet) and anionic (rose bengal) dyes. Adsorption isotherms were fitted using Langmuir, Freundlich, and Redlich-Peterson models; while all three showed good correlation, the Redlich-Peterson model provided the best overall fit, indicating a hybrid adsorption mechanism. The maximum Langmuir adsorption capacities achieved were 344 mg g^-1 for crystal violet and 246 mg g^-1 for rose bengal. The adsorption kinetics followed a pseudo-second-order model and reached equilibrium within 6 h. Finally, aerogel regeneration was performed over three cycles, showcasing the potential of aerogel reuse without significant changes in adsorption/desorption performance. Overall, this work demonstrates the potential of BSA nanofiber aerogels as a renewable, biodegradable, and high-performance platform for water purification of organic dyes.