Controlled synthesis and full factorial design optimization of chitosan-graphitic carbon nitride nanocomposite for improved antimicrobial activity.

Chitin and chitosan derived from natural waste sources offer significant potential when combined with metal-free photocatalysts. In this study, chitin was extracted from banana peel waste and deacetylated to chitosan, achieving high degrees of deacetylation confirmed by titration (92.83-95.95%) and FTIR (90.40-94.17%). The yield of chitin content of the banana waste peels and deacetylated banana peel chitin (banana peel chitosan) is 38.5 ± 1.2% and 32.3 ± 0.9% respectively. Graphitic carbon nitride (g-C₃N₄) synthesized from melamine-impregnated waste polyurethane foam was incorporated with chitosan to form a CS-g-C₃N₄ nanocomposite optimized using full factorial design of experiment. Characterization (FTIR, SEM-EDX, XRD, BET, zeta potential) confirmed successful integration and improved material properties. CS-g-C₃N₄ exhibited the strongest antioxidant activity (IC₅₀ = 46.8 μg/mL) and superior antibacterial performance, producing inhibition zones of 13.8 mm (S. aureus) and 11.5 mm (E. coli) at 0.5 mg/mL. ANOVA showed significant differences (p < 0.01) compared to individual components. These results identify CS-g-C₃N₄ as a promising multifunctional biomaterial for antimicrobial coatings, wound dressings, and environmental disinfection technologies.