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 μm powder. In the first method, fine eggshell powders were submitted to elevated temperatures from 105 to 800 °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 °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 °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.

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Disposal of massive amounts of eggshells and seashells from processing industries is a challenge. In recent years, there has been a focus to reuse these waste resources in the production of new thermoplastic and thermoset polymer materials. This paper reviews eggshell and seashell production by country and provides a perspective on the quantity of bio-calcium carbonate that could be produced annually from these wastes. The achievements obtained from the addition of recycled bio-calcium carbonate fillers (uncoated/unmodified) in polymer composites with a focus on tensile strength, flexural strength and impact toughness are discussed. To improve compatibility between calcium carbonate (mineral and bio-based) fillers and polymers, studies on surface modifiers are reviewed. Knowledge gaps and future research and development thoughts are outlined. Developing novel and innovative composites for this waste material could bring additional revenue to egg and seafood processors and at the same time reduce any environmental impact.

Graphene oxide (GO) was cross-linked with chitosan to yield a composite (GO-LCTS) with variable morphology, enhanced surface area, and notably high methylene blue (MB) adsorption capacity. The materials were structurally characterized using thermogravimetric analysis and spectroscopic methods (X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and 13 C solid-state NMR) to support that cross-linking occurs between the amine groups of chitosan and the −COOH groups of GO. Equilibrium swelling studies provide support for the enhanced structural stability of GO-cross-linked materials over the synthetic precursors. Scanning electron microscopy studies reveal the enhanced surface area and variable morphology of the cross-linked GO materials, along with equilibrium and kinetic uptake results with MB dye in aqueous media, revealing greater uptake of GO-LCTS composites over pristine GO. The monolayer uptake capacity ( Q m ; mg g –1 ) with MB reveals twofold variation for Q m , where GO-LCTS (402.6 mg g –1 ) > GO (286.9 mg g –1 ). The kinetic uptake profiles of MB follow a pseudo-second-order trend, where the GO composite shows more rapid uptake over GO. This study reveals that the sorption properties of GO are markedly improved upon formation of a GO–chitosan composite. The facile cross-linking strategy of GO reveals that its physicochemical properties are tunable and versatile for a wider field of application for contaminant removal, especially over multiple adsorption–desorption cycles when compared against pristine GO in its highly dispersed nanoparticle form.