Influence of Glutaraldehyde Cross-Linking on the Structure and Metal-Binding Properties of PEI-Modified Pineapple Leaf Microfiber

) was observed at a GA:PEI ratio of 1:25. Further increases in GA dosage led to a disproportionate decrease in Cu-(II) uptake relative to the nitrogen content, indicating reduced availability of effective binding sites despite the presence of nitrogen functionalities. This behavior is interpreted as arising from restricted conformational flexibility and diminished cooperative multidentate coordination at higher cross-link densities, demonstrating that GA cross-linking governs not only nitrogen incorporation but also the functional accessibility of amine groups in surface-immobilized PEI systems.