Zinc oxide-loaded chitosan-graphene oxide hydrogel nanocomposite as a potential catalyst for photocatalytic dye...

In this work, a novel in-situ approach was employed to incorporate the zinc oxide (ZnO) nanoparticles into the hybrid chitosan-graphene oxide (CSGO) hydrogel network, forming ZnO-embedded hydrogel nanocomposites (CSGOZnO). This endeavor offered a uniform dispersion of ZnO nanoparticles within the 3D polymeric hydrogel structure, as confirmed by FE-SEM and HR-TEM analyses. The XRD spectrum of CSGOZnO exhibited eleven characteristic crystal planes at 31.8, 34.5, 36.3, 47.6, 56.6, 62.9, 66.4, 68.0, 69.1, 72.6 and 77.0 (2θ), corresponding to enhanced crystallinity and structural integrity. The as-prepared hydrogel nanocomposite demonstrated outstanding potential to act as a catalyst for the photocatalytic degradation of cationic methylene blue (MB), anionic alizarin red (AR), and mixed dyes under visible-light. The dye degradation process followed the pseudo-second-order model, with rate constants of 5.0 × 10^-3, 3.0 × 10^-3, and 1.0 × 10^-3 min^-1 for MB, AR, and mixed dyes, respectively. The exceptional performance was attributed to the synergistic effects of the CSGO 3D gel network and the embedded ZnO nanoparticles, facilitating superior adsorption and photocatalytic degradation. To elucidate the degradation mechanism, a number of batch experiments were conducted in line with studying different parameters such as catalyst dosage, initial dye concentration, contact time and pH of the solution. Hence, the newly developed multifunctional CSGOZnO hydrogel nanocomposites, synthesized via an in-situ approach, demonstrate significant promise for photocatalytic degradation of organic dye molecules in contaminated water.