The Simple Method of Synthesizing Calcite and Aragonite from Indonesian Limestone

Precipitated CaCO₃ (PCC) with calcite and aragonite phases have been successfully synthesized using natural limestone. Synthesis of PCC was carried out by the simple method of carbonation using slurry Ca(OH)₂ with a variation of CO₂ gas flow rate at room temperature and variation of temperatures at a constant CO₂ gas flow rate. The raw material used is a very high purity Madura Island limestone. The PCC product was characterized by X-Ray Diffraction (XRD), Fourier Transform Infra-Red (FT-IR), and Scanning Electron Microscope (SEM). PCC on CO₂ gas flow variation produced the same phase, calcite with the characteristic of 2θ = 29.23° (104), rhombohedral cubic morphology, and a wavenumber of 712 cm^-1 as displayed from the FTIR spectra. The mixture of aragonite and calcite phase was observed in PCC products with temperature variations of 60-90°C. The characteristic aragonite was observed at 2θ = 26.2° with needle-like morphology. The highest fraction of aragonite was at the temperature of 60°C at 71.35%.