Development of two-dimensional amyloid fibril/carboxymethyl cellulose hybrid membranes for effective adsorption of hexavalent chromium

Amyloid fibrils (AFs) are protein aggregates with highly ordered fibrillar structures and can be formed via self-assembly of proteins under appropriate conditions. Owing to the unique properties of AFs, e.g., high surface-to-volume ratio and versatile functional groups, they offer abundant binding sites for the efficient adsorption of hexavalent chromium (Cr(VI)). This study was aimed at examining the performance of two-dimensional AF-based hybrid membranes for adsorbing Cr(VI). First, AF/carboxymethyl cellulose (AF/CMC) hybrid membranes were synthesized via chemical crosslinking coupled with phase inversion, followed by investigating the synthesis mechanism using Fourier transform infrared spectroscopy. Our results revealed that the surface microstructures and mechanical properties of the hybrid membranes could be affected by the AF:CMC mass ratio of the membrane. The porosity and ζ-potential of hybrid membranes were found to be dependent on both pH value and membrane composition. Analyses of the kinetics and thermodynamic behavior of Cr(VI) adsorption on the AF/CMC hybrid membranes revealed that the initial adsorption rate and maximum adsorption capacity were determined to be ∼149.20 mg g^–1 h^–1 and ∼311.11 mg g^–1, respectively. The Cr(VI) removal percentage of hybrid membrane with high CMC content was found to remain at >75 % after five successive adsorption-desorption cycles. Finally, the mechanism and interactions involved in the adsorption of Cr(VI) on the hybrid membrane were further investigated via thermodynamic analysis and X-ray photoelectron spectroscopy. This study provides an excellent example of harnessing AF-based membranes in water remediation, highlighting the potential of AF-based hybrid materials for wastewater treatment applications.