Synthesis and characterization of nanocomposite chitosan-gelatin hydrogel loaded with ZnO and its application in photocatalytic dye degradation

The composite hydrogel loaded with ZnO nanoparticles was synthesized using grafting of acrylamide over the polymeric chains of chitosan and gelatin in the presence of ammonium persulphate as initiator and maleic acid as cross-linker. Initially, the ZnO nanoparticles were synthesized using zinc nitrate and loaded at the time of synthesis of hydrogel. The purity of the synthesized ZnO nanoparticles was confirmed through XRD. The ZnO nanoparticles incorporated chitosan–gelatin hydrogel (CG-g-poly(AAm)-ZnO) was synthesized using free radical mechanism. The nanocomposite hydrogel showed good swelling capacity i.e., 545.81 % at pH 10. The nanocomposite hydrogel was characterized using XRD, FTIR, SEM and further studied their thermal stability. The combination of broad band of hydrogel and sharp peaks of nanoparticles in XRD indicated the successful synthesis of nanocomposite hydrogel. The FTIR spectrum of hydrogel represented the characteristics of its main components with major and minor shifts in the vibrational frequencies. The SEM images revealed the cross-linked network of hydrogel with uniform distribution of nanoparticles and elemental analysis detects the composition of elements in a hydrogel. The nanocomposite hydrogel was thermally stable up to the temperature of 250 °C and utilized for environmental remediation. The chitosan–gelatin nanocomposite hydrogel successfully degraded 90.8 % of Congo red dye in aqueous medium up to four cycles of degradation. All the results of dye degradation were evaluated with the help of Response Surface Methodology (RSM) with Central Composite Design (CCD). Embraced with good catalytic activity, the nanocomposite chitosan–gelatin hydrogel holds a great potential in photocatalytic degradation of dyes. © 2022