Preparation and characterization of a chitosan/TiO2 nanocomposite hydrogel intended for the photocatalytic degradation of pollutants

Nanocomposite chitosan-based hydrogels (chitosan-co-polycrotonic acid), with and without TiO2, were prepared via chemical cross-linking of chitosan using sodium trimetaphosphate (STMP), followed by free radical polymerization. The structural and morphological properties of the synthesized composites were investigated and analyzed using X-ray diffraction, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and diffuse reflectance spectroscopy (DRS) techniques, as well as by determining the swelling rate and the pH at the point of zero charge (pH(pzc)). The results of these analyses showed that the cross-linking of chitosan by STMP and the distribution of TiO2 nanoparticles on the surface of the gel were both successfully achieved. In addition, the incorporation of TiO2 particles into the hydrogel led to an increase in the swelling rate but a reduction in the band gap of titanium dioxide. These findings allowed concluding that the prepared material can be used for the efficient photocatalytic degradation of pollutants. [GRAPHICS]