Bio-based surface functionalization of cotton via periodate oxidation and chitosan grafting for sustainable lac dyeing and multifunctional performance

Abstract

This study presents a fully bio-based and sustainable surface functionalization strategy to enhance lac dye adsorption on cotton fabric through a two-step modification involving periodate oxidation followed by chitosan grafting. Cotton fibers develop a negative charge in aqueous dyeing media, and the anionic nature of lac dye leads to electrostatic repulsion and limited uptake. To address this, sodium periodate was used to oxidize the cotton surface, introducing aldehyde groups that enabled covalent grafting of chitosan—a cationic, biologically active polysaccharide—via Schiff base formation. The resulting amine-rich surface improved dye–fiber interaction under mildly acidic conditions. Surface characterization through zeta potential analysis, X-ray photoelectron spectroscopy, and scanning electron microscopy confirmed successful modification without damaging fiber morphology. Adsorption kinetics followed a pseudo-second-order model, indicating chemisorption, with optimal dye uptake at pH 4–5 and 90 °C. The functionalized cotton also exhibited excellent ultraviolet protection (UPF rating) and strong antibacterial activity against Escherichia coli and Staphylococcus aureus. This work highlights the potential of chitosan as a functional biological macromolecule in developing sustainable, multifunctional textiles through eco-friendly processing.