Specific properties of hydroxyapatite as a potential transporter of copper ions and its complexes

Application of the synergism between eggshells and copper in nanotechnology

Eggshells, the non-edible part of an egg, have immense uses in nanotechnology. Copper being an inexpensive metal has versatile applications in nanotechnology. However, its susceptibility to oxidation limits its practical applications. Eggshells are an efficient candidate to synthesize cap copper nanoparticles and copper nanoclusters, which are used in various arenas (dye degradation, antibacterial activity, nitrophenol adsorption, copper adsorption, and sensing). Reports on the edible part of an egg for passivating copper nanoparticles are rare. Usually, chicken eggshells are mostly used in this regard. Moreover, eggshells can be used for the adsorption of ionic copper. Thus, the synergism between eggshells and copper is a very pivotal aspect. The use of biological waste in association with copper in various applications may open a new pathway towards the circular economy. This review article summarizes applications that evolved from copper-eggshell synergism.

The preparation of calcium phosphate adsorbent from natural calcium resource and its application for copper ion removal

Using the hen eggshells (biowaste) as a source of calcium and an environmentally friendly approach, the nanopowder composed of 74% of hydroxyapatite (HA) and 26% of β-tricalcium phosphate (β-TCP) was obtained. Due to the maximum reduction of the stages associated with the use of chemicals and energy, this method can be considered as economically and environmentally friendly. A well-developed surface area and the negative zeta potential at pH above 3.5 indicate good adsorption properties of this material. The obtained material shows high adsorption capacity towards Cu²⁺ ions, i.e. 105.4 mg/g at pH 5. Good fit of the Langmuir adsorption model and the pseudo-second-order kinetic model may indicate chemical adsorption probably due to the electrostatic interactions between the Cu²⁺ cations and the negatively charged phosphate and hydroxyl groups on the material surface.