Amyloid–Chitosan Aerogels for Multi-Contaminant Water Purification under Batch and Rapid Flow-through Conditions

The increasing production of chemically diverse contaminants from industrial, municipal, and healthcare activities has motivated the need for developing innovative wastewater treatment strategies. For example, pharmaceuticals, including ibuprofen (IBP) and sulfamethoxazole (SMX), and toxic heavy metals, such as hexavalent chromium (Cr(VI)) and nickel (Ni(II)), have been increasingly detected in aquatic environments. Traditional water treatment strategies did not account for the removal of such contaminants in mind. Herein, we present a class of protein–polysaccharide composite aerogels constructed from bovine serum albumin (BSA) amyloid fibers and chitosan as adsorbents for the removal of these pharmaceutical and heavy metal contaminants. Amyloid fibers were prepared via acid-induced self-assembly, and chitosan was incorporated post-fibrillation in tunable ratios, followed by crosslinking and freeze-drying to yield highly porous and mechanically durable aerogel networks. Overall, the incorporation of a higher ratio of chitosan resulted in enhanced available surface area, mechanical strength, and structural stability, which collectively contributed to improved adsorption processes. Adsorption was evaluated for individual contaminants between pH 3 and 9, whereby IBP and SMX exhibited optimum removal at pH 6 (up to 92% for SMX), Cr(VI) between pH 3 and 6 (over 97%), and Ni(II) at pH 9 (78%). The aerogels also demonstrated excellent performance in binary pharmaceutical (IBP/SMX) and heavy-metal (Cr(VI)/Ni(II)) mixtures at ppb-level residual concentrations. Finally, we demonstrated the applicability of our aerogels in flow systems, achieving high Cr(VI) removal under both gravity-driven and rapid flow-through filtration, albeit with progressive breakthrough over five consecutive cycles without regeneration of the aerogel. Notably, the rapid-flow system achieved ∼96% Cr(VI) removal in the first cycle in only ∼20 s, comparable to results seen in equilibrium batch experiments. Overall, these findings establish BSA–chitosan aerogels as promising bio-based adsorbents for practical, continuous, and sustainable water purification.