Facile synthesis of CaCO3 and investigation on structural and optical properties of high purity crystalline calcite

Abstract

Crystalline calcium carbonate (CaCO3) is an inorganic substance readily available and able to be produced artificially. The widespread applications to industries especially as a filler has increased the need for further research on its properties and behavior. Crystalline CaCO3 may also provide a route to hydroxyapatite with biomedical applications. The physicochemical properties of CaCO3 can be manipulated via different preparation methods. This study focusses on a precipitation method to synthesize CaCO3. Calcium chloride (CaCl2) and ammonium carbonate (NH4CO3) were used for the synthesis in different concentrations ranging from 0.05 M to 1.0 M. Elemental and particle analysis were done to describe the resulting products structurally and phase identification. Elemental analysis was undertaken by X-Ray diffraction (XRD), Fourier transform infrared Spectroscopy (FT-IR), Raman Spectroscopy and Energy Dispersive X-Ray Analysis (ED-X). From elemental analysis, it was confirmed that the resulting product was calcite micro-particles. Further analysis was done on particle and crystallite sizes by Nano-Particle Sizer, XRD and FE-SEM micrograph. It was deduced from the aforementioned analysis, the smallest crystallite size measured by Scherrer equation is 85.71 nm obtained by precipitation CaCO3 at 0.5 M concentration. This also tallied with the smallest particle size measured by FESEM micrograph showing the smallest margin of particles with size 783 nm. Optical characteristic of CaCO3 was described by ultra-violet spectroscopy (UV–vis) showing UV was absorbed in UV-C range. This study is also informative by presenting calculated absorption coefficient 0.1154 M−1cm−1. Recent studies on CaCO3 precipitation method have rarely reported its absorption coefficient: hence this information is useful. It was concluded that the optimal concentration for CaCO3 precipitation is within the range of 0.1 M–0.5 M. Synthesized CaCO3 crystalline are all ≤1000 nm. This study has demonstrated that the precipitation method is able to produce calcite in the micrometer range and is suitable for further study on biosensor technology or drug delivery system application.