Preparation and Characterization of Chemically Cross-Linked Xanthan/Poly(Vinylalcohol) Hydrogel Films Containing Cerium Oxide Nanoparticles for Potential Application in Removal of Methylene Blue and Crystal Violet Dyes

In this work, hydrogel nanocomposites, as films, were prepared by embedding cerium oxide nanoparticles (CeO₂NPs) within xanthan gum (Xn)/poly(vinylalcohol) (PVA) matrices. Their physicochemical properties were tuned by adjusting the ratio between components and thermal treatment conditions. The cross-linking of the polymer network was confirmed by attenuated total reflectance-Fourier transform infrared (ATR-FTIR), thermal analysis, and swelling behavior. Morphological features were evaluated by atomic force microscopy (AFM), scanning electron microscopy (SEM), while optical properties were investigated by UV-Vis spectroscopy. Undoped films displayed high transparency (~80% transmittance at 400 nm), with thermal cross-linking determined only slight yellowing and negligible changes in absorption edge (300 ± 2 nm). In contrast, CeO₂NPs incorporation increased reflectance and introduced a new absorption threshold around 400 ± 2 nm, indicating nanoparticle-matrix interactions that modify optical behavior. Sorption studies with Methylene Blue (MB) and Crystal Violet (CV) dyes highlighted the influence of nanoparticle content and cross-linking on functional performance, with thermally treated samples showing the highest efficiency (~97-98% MB and 71-83% CV removal). Overall, the results demonstrate how structural tailoring and cross-linking control the characteristics of Xn/PVA/CeO₂ nanocomposites, providing insight into their design as multifunctional hydrogel materials for environmental applications.