Synthesis of Eggshell-derived Nanoparticles and Bionanocomposites Thereof for Food Packaging
Creators: Upadhyay, Punita
Publisher: name: University of Alberta Library
Year: 2023

<p>Eggshells are widely considered an agricultural waste and hence they are generally disposed into landfills without any transformation into useful products. However, this waste can be valuable source material for fertilizer production, fodder, and the development of valuable high-performance nanostructured biomaterials. This waste has the potential of producing hydroxyapatite which is a major component present in bone and teeth. Hydroxyapatite nanoparticles (HANPs) are widely used in biomedical and other fields such as wastewater treatment, soil remediation, catalyst, and food packaging applications due to their excellent biocompatibility and bioactivity properties. In this study, HANPs were successfully synthesized from eggshell waste by microwave-assisted (MW) as well as conventional heating (CH) precipitation methods using the low temperature (40 ℃) and a green template i.e., Azadirachta Indica leaf (Neem) (AI). The synthesized HANPs were characterized by different analytical techniques such as Fourier Transformation Infrared spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), and Thermogravimetric Analysis (TGA) for determining their functionality, shape, size, crystallinity, phase purity, and thermal stability. FTIR and Raman’s spectroscopy confirmed the pure hydroxyapatite phase with no other impurities. SEM and TEM analyses confirmed that HANPs obtained uniform distribution with less agglomeration by the MW method in the presence of AI when compared to the CH method and without AI. TEM analyses revealed the average size of HANPs from both methods without AI was 30-31 nm in width and 53-55 nm in length while in the presence of AI was 27-28 nm in width and 44-46 nm in length. XRD analysis indicated the formation of the pure crystalline structure of nanoparticles. The synthesized HANPs were thermally very stable and had a lower Ca/P ratio (1.81) from the MW method compared to the conventional heating method which is 1.95. Thus, this study revealed that HANPs synthesized by the MW method in presence of AI with smaller crystallite size and less agglomerated particles have a great potential to be used in the biomedical fields as well as food packaging applications.<br>
Further, in this study, the synthesized HANPs were used to reinforce biopolymer to prepare bionanocomposites films without any cross-linking agent in the presence of glycerol as a plasticizer. The influence of HANPs in bionanocomposites was investigated by varying their concentrations (1wt%, 3wt%, 5wt%, and 10wt%). The effect of the addition of HANPs and their impact on the final film properties were evaluated by TGA, Differential Scanning Calorimetry (DSC), Dynamic Mechanical Analysis (DMA), Tensile Testing, and Water Vapor Permeability (WVP). The morphology of bionanocomposites and the dispersion of nanoparticles in the chitosan matrix were evaluated using SEM, TEM, and XRD. The structural changes in the films were investigated by FTIR and XPS techniques. Results indicated that the addition of HANPs exhibited improved thermal stability, delated melting point, and better viscoelastic properties (higher glass transition temperature) of bionanocomposites compared to chitosan control film. The tensile strengths of the bionanocomposites increased with low concentrations (1wt%, and 3wt%) and decreased with high concentration (5wt%, and 10wt%) of HANPs. The films with 3wt% HANPs, demonstrated the highest tensile strength i.e., 61.54 % increase compared to neat films. Furthermore, the WVP of the bionanocomposites significantly declined by the addition of nanoparticles e.g., the addition of 1wt% HANPs exhibited a decrease in WVP (52%) compared to the control films. The SEM, TEM, and XRD analyses, confirmed that the bionanocomposites with 1wt% and 3wt% HANPs had more uniform nano-dispersions leading to exfoliated to partially intercalated nanocomposites. Based on the attractive properties obtained, the egg-shell waste based bionanocomposites have a great potential to be used in food packaging applications. </p>