Coaxially extruded Ag/chitosan-ZnO macrotubes for efficient dyes removal in real water samples

In this study, CS-ZnO macrotubes were prepared through co-axial extrusion techniques and were used as a template for the stabilization of silver nanoparticles (Ag NPs). FESEM, EDS, XRD, FTIR, TGA, and zeta potential analytical tools were used for structural analysis of the catalyst. The catalytic activity was explored against MB, MO, and CR dyes in distilled water (DW), tap water (TW), and seawater (SW) in the presence of NaBH₄. All three model dyes were studied alone and in mixtures in the presence of NaBH₄. The highest activity was displayed by Ag/CS-ZnO in DW with an apparent rate constant (k_app) of 6.5 × 10^-1 min^-1, 3.6 × 10^-1 min^-1, and 2.0 × 10^-1 min^-1 against MO, CR, and MB dyes, respectively. It was observed that the presence of cations or anions in a water sample can affect the rate of anionic dye degradation. Various experimental parameters, i.e., catalyst dose, initial dye concentration, and NaBH₄ effect, were studied. The catalyst recyclability was checked for four consecutive cycles. These results demonstrate that Ag/CS-ZnO macrotubes act as a dip-catalyst and provide a robust, reusable, and environmentally benign catalytic platform for efficient treatment of dye-contaminated wastewater under real-world applications.