A High-Pressure Gas Solid Carbonation Route to Produce Vaterite

A novel synthetic strategy based on a high pressure gas solid reaction using urea as an additive to produce value-added CaCO3 material is reported. Results showed that at about 150 degrees C and 12 MPa the reaction attained complete carbonation with predominant spherical vaterite crystals via a self -sustained reaction. The influences of working conditions including pressure, temperature, Ca(OH)(2)/urea mass ratio, and reaction time on the mineralization process were studied. The as prepared CaCO3 powder exhibited vaterite content as high as 94.2% and a surface area up to 32.9 m(2)/g. The mechanism study showed that the highpressure CO, acted as an inhibitor for urea decomposition at high temperature besides as a reactant; the urea entrapped Ca(OH)(2) via its melt to stabilize vaterite formation by an amine functional group and initiated the carbonation process via tiny water triggered by its slight decomposition. The separation to obtain the fine product was simple and allowed high urea recovery (for example, 93.6%). The method has merits for both the high CO, utilization and production of value-added CaCO3 without discharging inorganic salts; thus, it would be an environmentally friendly and potential route for industrial application.