Investigation of Eggshell Membrane Removal With Two Different Treatment Methods

Chicken eggshells (ESs) consist of 96%–97% calcium carbonate, while about 3%–4% consists of organic substances, mainly in the form of protein-based membranes and occluded organic matter. Recently, ESs have been studied as a filler in polymer composite materials, which represents an innovative solution to address ES valorization. In this study, thermal and chemical treatments were investigated for membrane removal since the membrane may alter various properties when the ES fillers are added to the composite material. A nanoindentation method was used to measure changes in the ES mechanical properties. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and Fourier-transform infrared (FT-IR) spectroscopy were used to characterize the ES membrane removal through chemical treatment. The results showed that even at a heating temperature of 100°C, the ES mechanical properties were negatively affected, while a low concentration of bleach solution (25% bleach solution and 10 min of holding time) was able to remove the membrane without reducing the ES mechanical properties. The chemical treatment method offers a means for ES membrane removal while conserving the quality of the mineral fraction (calcite; CaCO₃).