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.

The materials used for the construction of buildings are changing. There are now many sustainability drivers for developing novel green construction materials. An emerging material used for building construction is concrete with conventional coarse aggregates substituted as recycled concrete aggregates (RCA). This is a form of sustainable concrete. A finite number of buildings (>10) with this material have been constructed in North America, Europe and Asia. However; to help facilitate wide spread use and development of sustainable concrete with RCA, there is purpose in considering this material's at-elevated temperature (in-fire) mechanical properties. To date, this topic has seen limited research attention as it is difficult to study. The study herein considered the mechanical properties of conventional and sustainable concrete with RCA. The only difference between the conventional and the sustainable concrete mixes was the mass proportion of a conventional natural coarse aggregate, Limestone, which had been substituted with coarse RCA (at replacement proportions of 0%, 30% and 100%). Both the ambient and elevated temperature mechanical properties were considered with compressive mechanical tests using an innovative optical technology for strain measurement. Based on the analysis performed, a proportional decrease in retained strength and elasticity of concrete at-elevated temperature with increasing RCA content was observed. For example both mechanical properties showed a 0.2% decrease in retained value for every 1% RCA increase at 500°C. In addition the modelling parameter of Poisson ratio appeared to be influenced by the heat imposed and the aggregate type contained within the concrete. For example at 500°C, this parameter showed an 73% increase for concrete samples with only Limestone aggregate and a 15% decrease for samples with only RCA (of mixed origin primarily Siliceous). This paper concludes with highlighting current knowledge gaps and research needs that when addressed could help improve the facilitation of using sustainable concrete's with RCA in construction of buildings.

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The development of polyaniline (PANI)/biomaterial composites as humidity sensor materials represents an emerging area of advanced materials with promising applications. The increasing attention to biopolymer materials as desiccants for humidity sensor components can be explained by their sustainability and propensity to absorb water. This review represents a literature survey, covering the last decade, which is focused on the interrelationship between the core properties and moisture responsiveness of multicomponent polymer/biomaterial composites. This contribution provides an overview of humidity-sensing materials and the corresponding sensors that emphasize the resistive (impedance) type of PANI devices. The key physicochemical properties that affect moisture sensitivity include the following: swelling, water vapor adsorption capacity, porosity, electrical conductivity, and enthalpies of adsorption and vaporization. Some key features of humidity-sensing materials involve the response time, recovery time, and hysteresis error. This work presents a discussion on various types of humidity-responsive composite materials that contain PANI and biopolymers, such as cellulose, chitosan and structurally related systems, along with a brief overview of carbonaceous and ceramic materials. The effect of additive components, such as polyvinyl alcohol (PVA), for film fabrication and their adsorption properties are also discussed. The mechanisms of hydration and proton transfer, as well as the relationship with conductivity is discussed. The literature survey on hydration reveals that the textural properties (surface area and pore structure) of a material, along with the hydrophile–lipophile balance (HLB) play a crucial role. The role of HLB is important in PANI/biopolymer materials for understanding hydration phenomena and hydrophobic effects. Fundamental aspects of hydration studies that are relevant to humidity sensor materials are reviewed. The experimental design of humidity sensor materials is described, and their relevant physicochemical characterization methods are covered, along with some perspectives on future directions in research on PANI-based humidity sensors.