Chitosan coated cotton fabric embedded with silver nanoparticles for azo dye degradation in aqueous solutions

Anthropogenic activities have led to severe environmental degradation, posing a significant threat to global sustainability. Among these pollutants, synthetic dyes are of particular concern due to their contribution to water contamination and detrimental effects on ecosystems. Herein, we present an eco-friendly approach to remove toxic dyes from wastewater using silver nanoparticle-decorated chitosan-coated cotton fabric (Ag/Chi-CF) as a heterogeneous nano-catalyst. A 1 wt% Chi solution was applied to cotton fabric to enhance surface functionality and improve metal ion uptake capacity. The functionalized fabric was then treated with silver nitrate (AgNO₃) solutions at concentrations of 100, 200, and 300 μg/mL. Next, the subsequent reduction with 0.1 M NaBH₄ hydrate facilitates the in situ formation of silver nanoparticles, which is confirmed by a visible color change. The untreated cotton fabric (CF), chitosan-coated cotton (Chi-CF), and Ag/Chi-CF were characterized by SEM, XRD, EDX, and FTIR for their surface morphology, crystal structure, elemental analysis, and functional groups, respectively. Catalytic degradation studies were conducted with UV-Vis spectroscopy using Congo red dye as a model pollutant. The Ag3/Chi-CF nano-catalyst demonstrated excellent catalytic performance, achieving approximately 90% degradation of 50 ppm dye within 20 min (k_obs = 0.1 min⁻¹), following a second-order kinetic model, while showing a poor fit to zero-order and first-order models. The reusability of the Ag3/Chi-CF catalyst was demonstrated through three cycles, with minimal loss in performance to approximately 77%, highlighting its potential for sustainable wastewater treatment applications.