Synthesis and Characterization of Spherical Calcium Carbonate Nanoparticles Derived from Cockle Shells

• Main Authors: Abbas Ibrahim Hussein, Zuryati Ab-Ghani, Ahmad Nazeer Che Mat, Nur Atikah Ab Ghani, Adam Husein, Ismail Ab. Rahman
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: Applied Sciences
• Subjects: calcium carbonate; calcium oxide; cockle shell; sol–gel method; morphological images; nanoparticles
• Online Access: https://www.mdpi.com/2076-3417/10/20/7170

<b> </b>Cockle shells are a natural reservoir of calcium carbonate (CaCO₃), which is widely used in bone repair, tissue scaffolds, and the development of advanced drug delivery systems. Although many studies report on the preparation of CaCO₃, the development of a nanosized spherical CaCO₃ precursor for calcium oxide (CaO) that is suitable to be incorporated in dental material was scarce. Therefore, this study aimed to synthesize a nanosized spherical CaCO₃ precursor for CaO derived from cockle shells using a sol–gel method. Cockle shells were crushed to powder form and mixed with hydrochloric acid, forming calcium chloride (CaCl₂). Potassium carbonate (K₂CO₃) was then fed to the diluted CaCl₂ to obtain CaCO₃. The effect of experimental parameters on the morphology of CaCO₃, such as volume of water, type of solvents, feeding rate of K₂CO₃, and drying method, were investigated using field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffractometry (XRD), Brunauer–Emmett–Teller surface area analysis, and thermogravimetric analysis. Optimized CaCO₃was then calcined to form CaO. XRD analysis of CaCO₃ nanoparticles was indicative of the formation of a calcite phase. The well-structured spherical shape of CaCO₃ was obtained by the optimum condition of the addition of 50 mL of water into CaCl₂ in ethanolic solution with a 1 h feeding rate of K₂CO₃. Less agglomeration of CaCO₃ was obtained using a freeze-drying technique with the surface area of 26 m²/g and average particle size of 39 nm. Spherical shaped nanosized CaO (22–70 nm) was also synthesized. The reproducibility, low cost, and simplicity of the method suggest its potential applications in the large-scale synthesis of the nanoparticles, with spherical morphology in an industrial setting.