Sustainable Bio-Inspired Limestone Eggshell Powder for Potential Industrialized Applications

Biowaste chicken eggshells contain high amounts of calcium carbonate or calcite. Waste eggshells generated by processing industries have the potential to be used as limestone or lime in a variety of applications. Studies have shown removal of membrane from eggshells can be separated at the laboratory level, but mass production has not been industrialized. The aim of this study was to optimize two membrane removable techniques; heat treatment and bleach treatment. The as-received eggshell samples were first water ball milled into a 63 mu m powder. In the first method, fine eggshell powders were submitted to elevated temperatures from 105 to 800 degrees C in air. The second method involved submitting the powder to a chemical treatment of 10% to 100% bleach concentrations and holding in the solutions for different soak times. The powdered samples were characterized for chemical composition and microstructural analysis. The results indicated pure calcite can be produced by heating to a temperature of 300 degrees C for a period of 2 h or a 10% bleach treatment for 48 h or a 50% bleach for 10 min. In addition, calcite from eggshells could be transformed into lime by heating to 750 degrees C for 1 h. The heat treatment method can easily be scaled up to mass production. This study signified eggshells can be used as a total or partial alternative replacement to mined limestone.