Multifunctional lysozyme amyloid fibers-chitosan composite xerogel for adsorption of Cu2+, Cu-Citrate, and Cu-EDTA

Stable, treatment-resistant Cu complexes in practical wastewater are frequently neglected. Positively charged lysozyme amyloid fibrils (AF), however, exhibit unexplored potential for their adsorption. This study engineered an amyloid fibril-chitosan composite (AF-CS) xerogel and evaluated its adsorption performance in three systems: free Cu 2+ , Cu-Citrate binary, and Cu-EDTA binary. The characterization confirmed successful synthesis of AF-CS, revealing a porous and amine-rich structure with a more positive surface charge than that of pure AF xerogel. Systematic evaluation demonstrated adsorption capacities of 65.37 mg/g (free Cu 2+ ), 166.14 mg/g (Cu-Citrate), and 40.31 mg/g (Cu-EDTA). MINTEQ 3.0 speciation analysis identified anionic Cu-ligand complexes as dominant species in binary systems. Further investigation revealed synergistic adsorption mechanisms in the Cu-Citrate system: electrostatic attraction coupled with decomplexation-complexation pathways liberated citrate ligands, enabling electrostatic shielding and adsorption bridging that enhanced Cu coordination. Conversely, the high stability of Cu-EDTA chelates limited adsorption primarily to mechanisms involving electrostatic attraction, resulting in suboptimal performance. These findings advance the theoretical understanding of AF-CS interactions with diverse Cu species, demonstrating AF-CS as a promising material for Cu recovery from complex wastewater and providing guidance for designing novel remediation materials.