부산대학교 도서관

Utilization of abundant natural resources has been an important issue in recent years. CaCO3 was successfully prepared from natural sand by purification bubbling methods with flowing CO2 gas into an aqueous Ca(OH)2 medium with NaOH as catalyst. In the experimental set-up, natural sand was dissolved with different NaOH concentrations of 5, 6, and 7 M, respectively. In the carbonation process, room temperature is used as reaction temperature, while CO2 gas flow rate was carried out at 5 SCFH (Square Cubic Feet per Hour) and the speed of stirring was kept constant. The reaction was occurred around 5 minutes to produce precipitation of CaCO3. The influences of reaction parameters such as the various concentrations of NaOH were studied by using X-ray fluorescence spectrometer (XRF), X-ray powder diffraction (XRD), Particle size analyzer (PSA), and Scanning Electron Microscopy (SEM) to investigate the element composition, crystal structure, size of particles, and morphology of particles, respectively. The results showed that NaOH concentration effected not only on the phases of CaCO3 but also on the microstructure and morphology of CaCO3. Calcite and vaterite phases are observed which have a rhombic and spherical morphology in micro-scale, respectively.