A breakthrough technique for the preparation of high-yield precipitated calcium carbonate

Precipitated calcium carbonate (PCC) is conventionally produced through the gas–solid–liquid carbonation route, which consists on bubbling gaseous CO2 through a concentrated calcium hydroxide (Ca(OH)2) slurry. However, atmospheric carbonation processes are slow and have low carbonation efficiency. A novel technology based on the combination of supercritical carbon dioxide (scCO2) and ultrasonic agitation is described here for the preparation of high-yield PCC. The combination of both techniques has demonstrated to produce outstanding improvement for the conversion of Ca(OH)2 to the stable calcite polymorph of calcium carbonate (CaCO3). These experiments were carried out at 313 K and 13 MPa using a high-pressure reactor immersed in an ultrasounds cleaner bath. The process kinetics and the characteristics of the precipitated particles using ultrasonic agitation were compared with those obtained under similar experimental conditions using mechanical stirring and non-agitated systems. The crystal characteristics of the samples obtained using the three different agitation techniques were characterized by X-ray diffraction and scanning electron microscopy.