Characterisation of calcium carbonate and its polymorphs from cockle shells (Anadara granosa)

Calcium carbonate and its polymorphs from cockle shells (Anadara granosa) and commercial calcium carbonate were characterised using a variable pressure scanning electron microscopes (VPSEM), a transmission electron microscope (TEM), an energy dispersive X- ray analyser (EDX), X-ray diffraction (XRD) and Fourier transmission infrared spectroscopy (FT-IR). Cubic-like calcite crystals of commercial calcium carbonate and rod-like aragonite crystals of cockle shell powders were observed by both SEM and TEM. The EDX results showed that the cockle shells contained more calcium and carbon than the commercial calcium carbonate, whereas the commercial calcium carbonate contained more oxygen than the cockle shells. FT-IR analyses revealed the presence of carbonate groups in both the cockle shells and the commercial calcium carbonate. FT-IR analyses also showed the presence of aragonite in the cockle shells and calcite in the commercial calcium carbonate. XRD analyses showed that the cockle shells powder contained aragonite, whereas the commercial calcium carbonate contained calcite. The cockle shells powder was formed with good quality calcium carbonate and contained calcium carbonate in the aragonite phase.

Cockle shells are being used to produce scaffold to repair bone. No report is available on the characterisation of this substance. This study compared the chemical and morphological properties of shell components with the commercial calcium carbonate using VPSEM, EDX, TEM, FT-IR and XRD. The results demonstrated that cockle shells contain aragonite, the valuable polymorph of natural calcium carbonate.Figure optionsDownload as PowerPoint slideHighlights
► Powders were synthesised from cockle shells by mechanical grinding process.
► The cockle shells powders were characterised using VPSEM,,EDX, FT-IR and XRD.
► Calcium carbonate and its polymorph has characterised from cockle shells.
► Finally the cockle shells powders were detected as good quality calcium carbonate in the aragonite phase.